Effects of chondroitinase ABC and chymopapain on spinal motion segment biomechanics. An in vivo biomechanical, radiologic, and histologic canine study

Modic changes in the lumbar vertebral column of chondrodystrophic and non-chondrodystrophic dogs with intervertebral disc disease

Introduction

Modic changes (MC) are signs of vertebral pathology visible on magnetic resonance (MR) images that have been associated with low back pain (LBP) and disc degeneration in people. Multiple breeds of dogs also develop MCs and coincident back pain. However, the association between breed, MC, and spinal pathologies has yet to be fully elucidated. This study aimed to identify the prevalence of MC that occur spontaneously in the lumbar vertebral column of dogs diagnosed with intervertebral disc disease (IVDD) and examine their association with demographic criteria and the disc width index (DWI).

Methods

Medical records and lumbar vertebral column MR images were examined from 104 dogs (831 intervertebral disc spaces and adjacent vertebrae), which were divided into three groups: chondrodystrophic dogs (CD; n =54) and non-chondrodystrophic dogs (NCD; n =30) with IVDD as the primary diagnosis, and control dogs (n =20) with other spinal diseases as their primary diagnosis.

Results

Increasing age and a diagnosis of IVDD were significantly associated with MC in dogs (p <  0.001 and p = 0.0062, respectively). In CD dogs with IVDD, Type 2 MC were most prevalent, whereas, in NCD dogs, Type 3 MC were the most prevalent type. Type 2 MC were distributed nearly equally across the lumbar vertebral column, while Type 3 MC were primarily detected at the level of L7-S1.

Discussion

This study demonstrated that MC developed spontaneously in dogs, are common in dogs diagnosed with IVDD, and the type observed varies by breed. Further research is needed to understand the pathogenesis of MC; however, the increased presence of Type 2 MC in CD dogs, similar to what is found in people with disc degeneration, suggests that CD dogs could serve as models for MC in people.

Lateral fenestration of lumbar intervertebral discs in rabbits: development and characterisation of an in vivo preclinical model with multi-modal endpoint analysis

PURPOSE

To evaluate the biological and biomechanical effects of fenestration/microdiscectomy in an in vivo rabbit model, and in doing so, create a preclinical animal model of IVDD.

METHODS

Lateral lumbar IVD fenestration was performed in vivo as single- (L3/4; n = 12) and multi-level (L2/3, L3/4, L4/5; n = 12) fenestration in skeletally mature 6-month-old New Zealand White rabbits. Radiographic, micro-CT, micro-MRI, non-destructive robotic range of motion, and histological evaluations were performed 6- and 12-weeks postoperatively. Independent t tests, one-way and two-way ANOVA and Kruskal-Wallis tests were used for parametric and nonparametric data, respectively. Statistical significance was set at P < 0.05.

RESULTS

All rabbits recovered uneventfully from surgery and ambulated normally. Radiographs and micro-CT demonstrated marked reactive proliferative osseous changes and endplate sclerosis at fenestrated IVDs. Range of motion at the fenestrated disc space was significantly reduced compared to intact controls at 6- and 12-weeks postoperatively (P < 0.05). Mean disc height index percentage for fenestrated IVDs was significantly lower than adjacent, non-operated IVDs for both single and multi-level groups, at 6 and 12 weeks (P < 0.001). Pfirrmann MRI IVDD and histological grading scores were significantly higher for fenestrated IVDs compared to non-operated adjacent and age-matched control IVDs for single and multi-level groups at 6 and 12 weeks (P < 0.001).

CONCLUSIONS

Fenestration, akin to microdiscectomy, demonstrated significant biological, and biomechanical effects in this in vivo rabbit model and warrants consideration by veterinary and human spine surgeons. This described model may be suitable for preclinical in vivo evaluation of therapeutic strategies for IVDD in veterinary and human patients.

Chondroitinase as a therapeutic enzyme: Prospects and challenges

The chondroitinases (Chase) are bacterial lyases that specifically digest chondroitin sulfate and/or dermatan sulfate glycosaminoglycans via a β-elimination reaction and generate unsaturated disaccharides. In recent decades, these enzymes have attracted the attention of many researchers due to their potential applications in various aspects of medicine from the treatment of spinal cord injury to use as an analytical tool. In spite of this diverse spectrum, the application of Chase is faced with several limitations and challenges such as thermal instability and lack of a suitable delivery system. In the current review, we address potential therapeutic applications of Chase with emphasis on the challenges ahead. Then, we summarize the latest achievements to overcome the problems by considering the studies carried out in the field of enzyme engineering, drug delivery, and combination-based therapy.

An in vitro comparison of three nucleus pulposus removal techniques for partial intervertebral disc replacement: An ultra-high resolution MRI study

Background

Nuclectomy, also known as nucleotomy, is a percutaneous surgical procedure performed to remove nucleus material from the center of the disc. Multiple techniques have been considered to perform a nuclectomy, however, the advantages and disadvantages of each are not well understood.

Aims

This in vitro biomechanical investigation on human cadaveric specimens aimed to quantitatively compare three nuclectomy techniques performed using an automated shaver, rongeurs, and laser.

Material & Methods

Comparisons were made in terms of mass, volume and location of material removal, changes in disc height, and stiffness. Fifteen vertebra-disc-vertebra lumbar specimens were acquired from six donors (40 ± 13 years) and split into three groups. Before and after nucleotomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen.

Results

When using the automated shaver and rongeurs similar volumes of disc material were removed (2.51 ± 1.10% and 2.76 ± 1.39% of the total disc volume, respectively), while considerably less material was removed using the laser (0.12 ± 0.07%). Nuclectomy using the automated shaver and rongeurs significantly reduced the toe-region stiffness (p = 0.036), while the reduction in the linear region stiffness was significant only for the rongeurs group (p = 0.011). Post-nuclectomy, 60% of the rongeurs group specimens showed changes in the endplate profile while 40% from the laser group showed subchondral marrow changes.

Discussion

From the MRIs, homogeneous cavities were seen in the center of the disc when using the automated shaver. When using rongeurs, material was removed non-homogeneously both from the nucleus and annulus regions. Laser ablation formed small and localized cavities suggesting that the technique is not suitable to remove large volumes of material unless it is developed and optimized for this application.

Conclusion

The results demonstrate that both rongeurs and automated shavers can be used to remove large volumes of NP material but the reduced risk of collateral damage to surrounding tissues suggests that the automated shaver may be more suitable.

DPSCs Protect Architectural Integrity and Alleviate Intervertebral Disc Degeneration by Regulating Nucleus Pulposus Immune Status

Intervertebral disc (IVD) degeneration is the primary cause for low back pain that has a high prevalence in modern society and poses enormous economic burden on patients. Few effective therapeutic strategies are available for IVD degeneration treatment. To understand the biological effects of dental pulp stem cells (DPSCs) on nucleus pulposus (NP) cells, we carried out RNA sequencing, bioinformatic analysis which unveiled gene expression differences, and pathway variation in primarily isolated patients' NP cells after treatment with DPSCs supernatant. Western blot and immunofluorescence were used to verify these molecular alterations. Besides, to evaluate the therapeutic effect of DPSCs in IVD degeneration treatment, DPSCs were injected into a degeneration rat model in situ, with treatment outcome measured by micro-CT and histological analysis. RNA sequencing and in vitro experiments demonstrated that DPSCs supernatant could downregulate NP cells' inflammation-related NF-κB and JAK-STAT pathways, reduce IL-6 production, increase collagen II expression, and mitigate apoptosis. In vivo results showed that DPSCs treatment protected the integrity of the disc structure, alleviated extracellular matrix degradation, and increased collagen fiber expression. In this study, we verified the therapeutic effect of DPSCs in an IVD degeneration rat model and elucidated the underlying molecular mechanism of DPSCs treatment, which provides a foundation for the application of DPSCs in IVD degeneration treatment.

Immuno-Modulatory Effects of Intervertebral Disc Cells

Low back pain is a highly prevalent, chronic, and costly medical condition predominantly triggered by intervertebral disc degeneration (IDD). IDD is often caused by structural and biochemical changes in intervertebral discs (IVD) that prompt a pathologic shift from an anabolic to catabolic state, affecting extracellular matrix (ECM) production, enzyme generation, cytokine and chemokine production, neurotrophic and angiogenic factor production. The IVD is an immune-privileged organ. However, during degeneration immune cells and inflammatory factors can infiltrate through defects in the cartilage endplate and annulus fibrosus fissures, further accelerating the catabolic environment. Remarkably, though, catabolic ECM disruption also occurs in the absence of immune cell infiltration, largely due to native disc cell production of catabolic enzymes and cytokines. An unbalanced metabolism could be induced by many different factors, including a harsh microenvironment, biomechanical cues, genetics, and infection. The complex, multifactorial nature of IDD brings the challenge of identifying key factors which initiate the degenerative cascade, eventually leading to back pain. These factors are often investigated through methods including animal models, 3D cell culture, bioreactors, and computational models. However, the crosstalk between the IVD, immune system, and shifted metabolism is frequently misconstrued, often with the assumption that the presence of cytokines and chemokines is synonymous to inflammation or an immune response, which is not true for the intact disc. Therefore, this review will tackle immunomodulatory and IVD cell roles in IDD, clarifying the differences between cellular involvements and implications for therapeutic development and assessing models used to explore inflammatory or catabolic IVD environments.

Discovery and Application of Postnatal Nucleus Pulposus Progenitors Essential for Intervertebral Disc Homeostasis and Degeneration

Intervertebral disc degeneration (IDD) results from the dysfunction of nucleus pulposus (NP) cells and the exhaustion of NP progenitors (ProNPs). The cellular applications of NP cells during IDD are currently limited due to the lack of in vivo studies showing whether NP cells are heterogeneous and contain ProNPs throughout postnatal stages. In this study, single-cell RNA sequencing of purified NP cells is used to map four molecularly defined populations and urotensin II receptor (UTS2R)-expressing postnatal ProNPs is identified, which are markedly exhausted during IDD, in mouse and human specimens. The lineage tracing shows that UTS2R⁺ ProNPs preferentially resides in the NP periphery with its niche factor tenascin-C and give rise to functional NP cells. It is also demonstrated that transplanting UTS2R⁺ ProNPs with tenascin-C into injured intervertebral discs attenuate the progression of IDD. The study provides a novel NP cell atlas, identified resident ProNPs with regenerative potential, and revealed promising diagnostic and therapeutic targets for IDD.

Combination of ultra-purified stem cells with an in situ-forming bioresorbable gel enhances intervertebral disc regeneration

Background

Lumbar intervertebral disc (IVD) herniations are associated with significant disability. Discectomy is the conventional treatment option for IVD herniations but causes a defect in the IVD, which has low self-repair ability, thereby representing a risk of further IVD degeneration. An acellular, bioresorbable, and good manufacturing practice (GMP)-compliant in situ-forming gel, which corrects discectomy-associated IVD defects and prevents further IVD degeneration had been developed. However, this acellular matrix-based strategy has certain limitations, particularly in elderly patients, whose tissues have low self-repair ability. The aim of this study was to investigate the therapeutic efficacy of using a combination of newly-developed, ultra-purified, GMP-compliant, human bone marrow mesenchymal stem cells (rapidly expanding clones; RECs) and the gel for IVD regeneration after discectomy in a sheep model of severe IVD degeneration.

Methods

RECs and nucleus pulposus cells (NPCs) were co-cultured in the gel. In addition, RECs combined with the gel were implanted into IVDs following discectomy in sheep with degenerated IVDs.

Findings

Gene expression of NPC markers, growth factors, and extracellular matrix increased significantly in the co-culture compared to that in each mono-culture. The REC and gel combination enhanced IVD regeneration after discectomy (up to 24 weeks) in the severe IVD degeneration sheep model.

Interpretation

These findings demonstrate the translational potential of the combination of RECs with an in situ-forming gel for the treatment of herniations in degenerative human IVDs.

Funding

Ministry of Education, Culture, Sports, Science, and Technology of Japan, Japan Agency for Medical Research and Development, and the Mochida Pharmaceutical Co., Ltd.

SIRT3 mitigates intervertebral disc degeneration by delaying oxidative stress-induced senescence of nucleus pulposus cells

Senescence of nucleus pulposus (NP) cells (NPC) is a major cause of intervertebral disc degeneration (IVDD), so delay NPC senescence may be beneficial for mitigating IVDD. We studied the effect and mechanism of silent information regulator 2 homolog 3 (SIRT3) on NPC senescence in vivo and in vitro. First, we observed SIRT3 expression in normal and degenerated NPC with immunohistochemical and immunofluorescence staining. Second, using SIRT3 lentivirus transfection, reactive oxygen species probe, senescence-associated β-galactosidase staining, polymerase chain reaction, and western blot to observe the oxidative stress, senescence, and degeneration degree among groups. Subsequently, pretreatment with adenosine monophosphate-activated protein kinase (AMPK) agonists and inhibitors, observing oxidative stress, senescence, and degeneration degree among groups. Finally, the IVDD model was constructed and divided into Ctrl, Vehicle, LV-shSIRT3, and LV-SIRT3 groups. X-ray and magnetic resonance imaging scans were performed on rat's tails after 1 week; hematoxylin and eosin and safranin-O staining were used to evaluate the degree of IVDD; immunofluorescence staining was used to observe SIRT3 expression; immunohistochemical staining was used to observe oxidative stress, senescence, and degeneration degree of NP. We found that SIRT3 expression is reduced in degenerated NP tissues but increased in H2 O2 -induced NPC. Moreover, SIRT3 upregulation decreased oxidative stress, delayed senescence, and degeneration of NPC. In addition, activation of the AMPK/PGC-1α pathway can partially mitigate the NPC oxidative stress, senescence, and degeneration caused by SIRT3 knockdown. The study in vivo revealed that local SIRT3 overexpression can significantly reduce oxidative stress and ECM degradation of NPC, delay NPC senescence, thereby mitigating IVDD. In summary, SIRT3 mediated by the AMPK/PGC-1α pathway mitigates IVDD by delaying oxidative stress-induced NPC senescence.

Combined nucleus pulposus augmentation and annulus fibrosus repair prevents acute intervertebral disc degeneration after discectomy

Tissue-engineered approaches for the treatment of early-stage intervertebral disc degeneration have shown promise in preclinical studies. However, none of these therapies has been approved for clinical use, in part because each therapy targets only one aspect of the intervertebral disc's composite structure. At present, there is no reliable method to prevent intervertebral disc degeneration after herniation and subsequent discectomy. Here, we demonstrate the prevention of degeneration and maintenance of mechanical function in the ovine lumbar spine after discectomy by combining strategies for nucleus pulposus augmentation using hyaluronic acid injection and repair of the annulus fibrosus using a photocrosslinked collagen patch. This combined approach healed annulus fibrosus defects, restored nucleus pulposus hydration, and maintained native torsional and compressive stiffness up to 6 weeks after injury. These data demonstrate the necessity of a combined strategy for arresting intervertebral disc degeneration and support further translation of combinatorial interventions to treat herniations in the human spine.

Denosumab alleviates intervertebral disc degeneration adjacent to lumbar fusion by inhibiting endplate osteochondral remodeling and vertebral osteoporosis in ovariectomized rats

Background

Although adjacent segmental intervertebral disc degeneration (ASDD) is one of the most common complications after lumbar fusion, its exact mechanism remains unclear. As an antibody to RANKL, denosumab (Dmab) effectively reduces bone resorption and stimulates bone formation, which can increase bone mineral density (BMD) and improve osteoporosis. However, it has not been confirmed whether Dmab has a reversing or retarding effect on ASDD.

Methods

Three-month-old female Sprague-Dawley rats that underwent L4–L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after bilateral ovariectomy (OVX) surgery were given Dmab 4 weeks after PLF surgery (OVX+PLF+Dmab group). In addition, the following control groups were defined: Sham, OVX, PLF, and OVX+PLF (n=12 each). Next, manual palpation and X-ray were used to evaluate the state of lumbar fusion. The bone microstructure in the lumbar vertebra and endplate as well as the disc height index (DHI) of L5/6 was evaluated by microcomputed tomography (μCT). The characteristic alterations of ASDD were identified via Safranin-O green staining. Osteoclasts were detected using tartrate-resistant acid phosphatase (TRAP) staining, and the biomechanical properties of vertebrae were evaluated. Aggrecan (Agg), metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) expression in the intervertebral disc were detected by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) analysis. In addition, the expression of CD24 and Sox-9 was assessed by immunohistochemistry.

Results

Manual palpation showed clear evidence of the fused segment’s immobility. Compared to the OVX+PLF group, more new bone formation was observed by X-ray examination in the OVX+PLF+Dmab group. Dmab significantly alleviated ASDD by retaining disc height index (DHI), decreasing endplate porosity, and increasing vertebral biomechanical properties and BMD. TRAP staining results showed a significantly decreased number of active osteoclasts after Dmab treatment, especially in subchondral bone and cartilaginous endplates. Moreover, the protein and mRNA expression results in discs (IVDs) showed that Dmab not only inhibited matrix degradation by decreasing MMP-13 and ADAMTS-4 but also promoted matrix synthesis by increasing Agg. Dmab maintained the number of notochord cells by increasing CD24 but reducing Sox-9.

Conclusions

These results suggest that Dmab may be a novel therapeutic target for ASDD treatment.

Long-term pre-clinical evaluation of an injectable chitosan nanocellulose hydrogel with encapsulated adipose-derived stem cells in an ovine model for IVD regeneration

The potential therapeutic benefit of adipose-derived stem cells (ASCs) encapsulated in an injectable hydrogel for stimulating intervertebral disc (IVD) regeneration has been assessed by a number of translational and preclinical studies. However, previous work has been primarily limited to small animal models and short-term outcomes of only a few weeks. Long-term studies in representative large animal models are crucial for translation into clinical success, especially for permanent stabilization of major defects such as disc herniation. An injectable chitosan carboxymethyl cellulose hydrogel scaffold loaded with ASCs was evaluated regarding its intraoperative handling, crosslinking kinetics, cell viability, fully-crosslinked viscoelasticity, and long-term therapeutic effects in an ovine model. Three IVDs per animal were damaged in 10 sheep. Subcutaneous adipose tissue was the source for autologous ASCs. Six weeks after IVD damage, two of the damaged IVDs were treated via ASC-loaded hydrogel injection. After 12 months following the implantation, IVD disc height and histological and cellular changes were assessed. This system was reliable and easy to handle intraoperatively. Over 12 months, IVD height was stabilized and degeneration progression significantly mitigated compared to untreated, damaged IVDs. Here we show for the first time in a large animal model that an injectable chitosan carboxymethyl cellulose hydrogel system with encapsulated ASCs is able to affect long-term stabilization of an injured IVD and significantly decrease degeneration processes as compared to controls.

Research and Application of Chondroitin Sulfate/Dermatan Sulfate-Degrading Enzymes

Chondroitin sulfate (CS) and dermatan sulfate (DS) are widely distributed on the cell surface and in the extracellular matrix in the form of proteoglycan, where they participate in various biological processes. The diverse functions of CS/DS can be mainly attributed to their high structural variability. However, their structural complexity creates a big challenge for structural and functional studies of CS/DS. CS/DS-degrading enzymes with different specific activities are irreplaceable tools that could be used to solve this problem. Depending on the site of action, CS/DS-degrading enzymes can be classified as glycosidic bond-cleaving enzymes and sulfatases from animals and microorganisms. As discussed in this review, a few of the identified enzymes, particularly those from bacteria, have wildly applied to the basic studies and applications of CS/DS, such as disaccharide composition analysis, the preparation of bioactive oligosaccharides, oligosaccharide sequencing, and potential medical application, but these do not fulfill all of the needs in terms of the structural complexity of CS/DS.

Regulation of the inflammatory cycle by a controllable release hydrogel for eliminating postoperative inflammation after discectomy

Surgery is the final choice for most patients with intervertebral disc degeneration (IDD). Operation-caused trauma will cause inflammation in the intervertebral disc. Serious inflammation will cause tissue defects and induce tissue degeneration, IDD recurrence and the occurrence of other diseases. Therefore, we proposed a scheme to treat recurrence after discectomy by inhibiting inflammation with an aspirin (ASP)-loaded hydrogel to restore the mechanical stability of the spine and relieve local inflammation. ASP-liposomes (ASP-Lips) were incorporated into a photocrosslinkable gelatin-methacryloyl (GelMA) via mixing. This material can effectively alleviate inflammation by inhibiting the release of high mobility group box 1 (HMGB1) from the nucleus to the cytoplasm. We further assessed the expression of inflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α), and degeneration-related factors, such as type II collagen (COL-2), Aggrecan, matrix metallopeptidases-3 (MMP-3), MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4) and ADAMTS-5 in rat nucleus pulpous cells. The level of IDD was analyzed through H&E, safranin-O staining and immunohistochemistry in rabbit samples. In vitro, we found that ASP-Lip@GelMA treatment significantly decreased inflammatory cytokines, MMP-3 and -13, and ADAMTS-4 and -5 and up-regulated COL-2 and Aggrecan via the inhibited release of HMGB-1 from the nucleus. In vivo, ASP-Lip@GelMA can effectively inhibit inflammation of local tissue after disc surgery and fill local tissue defects. This composite hydrogel system is a promising way to treat the recurrence of IDD after surgery without persistent complications.

Small molecule antagonist of C-C chemokine receptor 1 (CCR1) reduces disc inflammation in the rabbit model

BACKGROUND CONTEXT

Targeting chemokines or chemokine receptors is a promising treatment strategy for diseases with chronic inflammation such as rheumatoid arthritis and discogenic pain. Identifying specific molecules and determining their effectiveness in animal models are the first steps in developing these treatments. Macrophage markers have been detected in the intervertebral disc tissues of patients with disc degenerative disease and discogenic pain and in different animal models. Macrophage recruitment into the disc may play a role in initiation of inflammation and if unresolved may lead to chronic inflammation and subsequent back pain.

PURPOSE

The objectives of these studies are to (1) identify chemokine receptor antagonists that can block macrophage migration induced by disc cells in vitro and (2) determine if intradiscal treatment with these antagonists can reduce disc inflammation and degeneration in vivo.

STUDY DESIGN

In vitro migration assays were used to test effectiveness of chemokine receptor antagonists to block macrophage migration induced by disc cells. The rabbit annular puncture model was used to test for anti-inflammatory and regenerative effects of chemokine receptor antagonist treatment in vivo.

METHODS

In vitro - THP-1 human monocytic cell line and freshly isolated rabbit primary splenocytes were assayed for migration using 3 µm Corning Transwell inserts with conditioned media of interleukin (IL)-1β treated human or rabbit disc cells. Inhibition of macrophage migration was evaluated using different concentrations of small molecule antagonists of C-C chemokine receptor (CCR)1 and CCR2. In vivo - New Zealand White rabbits (n=40) underwent disc puncture and intradiscal treatment with saline, CCR1 or CCR2 antagonists within the same procedure. X-ray and magnetic resonance (MR) images and serum samples were taken for disc height, MRI grade and IL-8 serum level analyses. Intervertebral discs were isolated for RNA analysis of inflammatory and disc phenotypic markers and for immunohistochemical analysis of macrophage marker, RAM11. The outcome measures were compared between the three treatment groups. These studies were funded by a research grant from AO Foundation, Switzerland (Project no S-14-86A; 120000 CHF). CCR1 and CCR2 antagonists were kindly provided by ChemoCentryx (Mountain View, CA).

RESULTS

In vitro migration assays showed that THP-1 migration induced by disc cells was blocked by CCR2 antagonist more effectively than CCR1 antagonist, while rabbit splenocyte migration was inhibited by CCR1 antagonist and not the other. In the rabbit annular puncture model, rabbit discs treated with CCR1 antagonist had significantly better MRI grades than those treated with CCR2 antagonist at 6 weeks post-treatment. Gene expression studies demonstrate that discs treated with CCR1 or CCR2 antagonists expressed less inflammatory markers than saline-treated discs at 3 weeks post-treatment. Although CCR2 antagonist treatment did not reduce inflammatory marker expression at 6 weeks, discs treated with CCR1 antagonist expressed less inflammatory markers and also a higher ratio of collagen type 2 to collagen type 1 genes indicating favorable disc matrix production. There were no significant differences between all three treatment groups in regards to disc height indexes, IL-8 serum levels or macrophage marker detection.

CONCLUSIONS

These studies have identified that small molecule antagonists against CCR2 and CCR1 were respectively effective in blocking THP-1 and rabbit splenocyte migration induced by disc cells in vitro. Further, both CCR2 and CCR1 antagonist intradiscal treatments were effective in reducing disc inflammation at an early time point of 3 weeks. Lastly, only CCR1 antagonist demonstrated anti-inflammatory effects and better MRI grades at 6 weeks.

CLINICAL SIGNIFICANCE

Our preclinical studies demonstrate that CCR1 and CCR2 antagonist delivery through intradiscal injection is sufficient to reduce disc inflammation at early time points, whereas CCR1 antagonists had longer term anti-inflammatory effects. Clinical studies have found that CCR1 antagonist was safe, tolerable and clinically active in reducing inflammation in rheumatoid arthritis patients. These studies suggest that CCR1 antagonist may be a promising biological treatment to reduce disc inflammation that translates to back pain relief.

The Optimal Timing of Hydrogel Injection for Treatment of Intervertebral Disc Degeneration: Quantitative Analysis Based on T1ρ MR Imaging

STUDY DESIGN

Animal experimental study.

OBJECTIVE

The aim of this study was to investigate the optimal time of hydrogel injection for regenerating intervertebral disc degeneration (IDD) based on T1ρ magnetic resonance imaging (MRI).

SUMMARY OF BACKGROUND DATA

Currently, different approaches are being pursued to regenerate the IDD. However, the optimal timing for the regenerative intervention is unclear.

METHODS

The slowly, progressive IDD models were established in 18 rhesus monkeys. On the basis of the MR T1ρ values of the discs, the rhesus monkeys were divided into severe (T1ρ values: <81 ms), moderate (T1ρ values: 81∼95 ms), and mild (T1ρ values: 96∼110 ms) degeneration groups. Biocompatible hydrogel was injected into the central part of the nucleus pulposus of the discs under fluoroscopic guidance. Treatment effects were investigated using radiography, T1ρ MRI, and histology until 12 months postoperatively.

RESULTS

After injection, the T1ρ values of all the discs increased significantly at 1 month postoperatively, and then remained at approximately 110 ms in the mild and moderate groups during the whole observation period, with no significant difference compared to the values at 1 month (P > 0.05). However, in the severe group, the T1ρ values decreased significantly after 1 month and leveled at approximately 70 ms after 6 months, with significant difference compared to the values at 1 month (P < 0.05). In the mild and moderate groups, there were no significant differences between preoperative histological scores and those at 12 months (P > 0.05). However, the histological score in the severe group at 12 months was significantly higher than the preoperative scores (P < 0.05).

CONCLUSION

This study suggested that the moderate degenerative stage of IDD (T1ρ values from 95 to 80 ms) could be the optimal time for hydrogel injection aimed at the regenerative intervention, based on T1ρ-MR imaging technique and quantitative analysis.

LEVEL OF EVIDENCE

N/A.

Cervical disc width index is a reliable parameter and consistent in young growing Dutch Warmblood horses

Intervertebral disc disease, as well as the associated alteration of the radiographic intervertebral disc space width, has been reported in horses. Disc height index (DHI) has proven to be an accurate and objective parameter in other species but data related to this parameter are lacking in horses. Therefore, the aims of this retrospective longitudinal diagnostic accuracy study were (a) to evaluate the reliability of measurements within and between observers of the equine Disc Width Index (EDWI) as a parameter for radiographic equine cervical intervertebral disc space width, and (b) to evaluate the sequential development of the EDWI over time. For this, EDWI from all intervertebral disc spaces between second cervical (C) to first thoracic (Th) vertebrae were obtained in a group of 39 Dutch Warmblood horses at 1, 5, and 18 months of age, by one European College of Veterinary Diagnostic Imaging (ECVDI) board-certified veterinary radiologist (S.V.) and two veterinary students. Bland-Altmann plots and intraclass Correlation Coefficient revealed a good intra- and interobserver agreement. A linear mixed-effect model did reveal that mean EDWI increases significantly toward the caudal cervical spine, but did not differ significantly for a certain location over time or between sexes. Spearman's rank test did show a significant correlation between the vertebral alignment angle induced by different head-neck positions and a normalized EDWI (ρ = 0.33, P < .0001). Student's t-test revealed that the presence of C6-C7 transposition of the transverse processes did not influence EDWI significantly. It was concluded that EDWI represents a reliable parameter for equine cervical radiographic intervertebral disc space width. Practical implementation of EDWI warrants monitoring in a group of adult horses while maintaining a standardized head-neck position.

Selective Chemonucleolysis With Condoliase in Cynomolgus Monkeys

Selective chemonucleolytic effects of condoliase, a glycosaminoglycan degrading enzyme, was investigated histopathologically in cynomolgus monkeys. Condoliase was administered once into the lumber intervertebral disc (IVD), and as a comparative control, chymopapain, a proteolytic enzyme, was administered in a similar manner. Histopathological changes of the IVD and the adjacent vertebral body (VB) were examined at 1 to 26 weeks after administration. Major changes induced by condoliase in the IVD were degenerative and necrotic changes in the nucleus pulposus, annulus fibrosus, cartilaginous endplate (CEP), and epiphyseal growth plate (EGP); focal disappearance of the EGP; and neovascularization and ossification of the CEP. Decreased/necrosis of bone marrow cells with new bone formation was observed in the VB. Cellular regeneration in the IVD was observed as a recovery changes on and after week 4. The changes in the IVD and VB subsided at week 26. Chymopapain induced qualitatively similar but more widely extended changes. The degrees of the changes in the IVD and VB were more severe than those of condoliase, and the changes were exacerbated even at week 26. These results indicated that histopathological changes caused by condoliase were less severe and more selective than those by chymopapain.

Mesenchymal Stem Cell-Seeded High-Density Collagen Gel for Annular Repair: 6-Week Results From In Vivo Sheep Models

BACKGROUND

Our group has previously demonstrated in vivo annulus fibrosus repair in animal models using an acellular, riboflavin crosslinked, high-density collagen (HDC) gel.

OBJECTIVE

To assess if seeding allogenic mesenchymal stem cells (MSCs) into this gel yields improved histological and radiographic benefits in an in vivo sheep model of annular injury.

METHODS

Fifteen lumbar intervertebral discs (IVDs) were randomized into 4 groups: intact, injury only, injury + acellular gel treatment, or injury + MSC-seeded gel treatment. Sheep were sacrificed at 6 wk. Disc height index (DHI), Pfirrmann grade, nucleus pulposus area, and T2 relaxation time (T2-RT) were calculated for each IVD and standardized to healthy controls from the same sheep. Quantitative histological assessment was also performed using the Han scoring system.

RESULTS

All treated IVDs retained gel plugs on gross assessment and there were no adverse perioperative complications. The MSC-seeded gel treatment group demonstrated statistically significant improvement over other experimental groups in DHI (P = .002), Pfirrmann grade (P < .001), and T2-RT (P = .015). There was a trend for greater Han scores in the MSC-seeded gel-treated discs compared with injury only and acellular gel-treated IVDs (P = .246).

CONCLUSION

MSC-seeded HDC gel can be delivered into injured IVDs and maintained safely in live sheep to 6 wk. Compared with no treatment and acellular HDC gel, our data show that MSC-seeded HDC gel improves outcomes in DHI, Pfirrmann grade, and T2-RT. Histological analysis shows improved annulus fibrosus and nucleus pulposus reconstitution and organization over other experimental groups as well.

MicroRNA-181a exerts anti-inflammatory effects via inhibition of the ERK pathway in mice with intervertebral disc degeneration

Enzymatic decomposition of extracellular matrix and possibly local inflammation may cause intervertebral disc degeneration (IDD). MicroRNAs have been reported to correlate with the development of IDD. In this experiment, we aim at finding out the role of miR-181a in the inflammation of IDD and the underlying mechanism. The targeting relationship between miR-181a and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was verified. Following the establishment of IDD mouse models, disc height index (DHI) and the change of DHI (%DHI) were measured. The functional role of miR-181a in IDD was determined using ectopic expression and depletion and reporter assay experiments. Expression of miR-181a, TRAIL, extracellular signal-regulated kinase (ERK) pathway-related genes and inflammatory factors was evaluated. Also, the expression of collagen I and collagen II was observed. miR-181a directly targeted TRAIL. IDD mice exhibited significant degeneration of the intervertebral disc. miR-181a was downregulated while TRAIL was upregulated in mice with IDD. miR-181a upregulation and the ERK pathway inhibition could reduce expression of TRAIL, ERK pathway-related genes, inflammatory factors, and collagen I, but promote collagen II expression. Our results reveal that upregulation of miR-181a protects against inflammatory response by inactivating the ERK pathway via suppression of TRAIL in IDD mice. These results point to miR-181a as a potential therapeutic target for the clinical management of IDD.

Use of Allogeneic Hypoxic Mesenchymal Stem Cells For Treating Disc Degeneration in Rabbits

Intervertebral discs (IVDs) are important biomechanical components of the spine. Once degenerated, mesenchymal stem cell (MSC)-based therapies may aid in the repair of these discs. Although hypoxic preconditioning enhances the chondrogenic potential of MSCs, it is unknown whether bone marrow MSCs expanded under hypoxic conditions (1% O₂ , here referred to as hypoxic MSCs) are better than bone marrow MSCs expanded under normoxic conditions (air, here referred to as normoxic MSCs) with regards to disc regeneration capacity. The purpose of this study was to compare the therapeutic effects of hypoxic and normoxic MSCs in a rabbit needle puncture degenerated disc model after intra-disc injection. Six weeks after needle puncture, MSCs were injected into the IVD. A vehicle-treated group and an un-punctured sham-control group were included as controls. The tissues were analyzed by histological and immunohistochemical methods 6 and 12 weeks post-injection. At 6 and 12 weeks, less disc space narrowing was evident in the hypoxic MSC-treated group compared to the normoxic MSC-treated group. Significantly better histological scores were observed in the hypoxic MSC group. Discs treated with hypoxic MSCs also demonstrated significantly better extracellular matrix deposition in type II and XI collagen. Increased CD105 and BMP-7 expression were also observed upon injection of hypoxic MSCs. In conclusion, hypoxic MSC injection was more effective than normoxic MSC injection for reducing IVD degeneration progression in vivo. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1440-1450, 2019.

Computed tomography-guided sub-end plate injection of pingyangmycin for a novel rabbit model of slowly progressive disc degeneration

BACKGROUND CONTEXT

Different animal models are used in disc degenerative disease research by now. To our knowledge, a functional animal model that mimics ischemic and slowly progressive disc degeneration of humans does not exist.

STUDY DESIGN

This is an experimental animal study of disc degeneration.

PURPOSE

The purpose of this study was to establish an ischemic and slowly progressive intervertebral disc (IVD) degeneration model with an injection of pingyangmycin (PYM) into subchondral bone adjacent to the disc, using bone marrow needle guided by computed tomography (CT) scan.

METHODS

The subchondral bone adjacent to the lumbar IVDs (from L3-L4 to L5-L6) of 18 rabbits was randomly injected with 3 mL PYM solution (1.5 mg/mL PYM), 3 mL phosphate-buffered saline (vehicle control), or exteriorized but not injected with anything (sham), with using bone marrow needle guided by CT scan. The degenerative process was investigated by using radiography and magnetic resonance imaging at 1, 3, and 6 months postoperatively, combined with histological scoring, immunohistochemistry, and real-time polymerase chain reaction analysis.

RESULTS

Significant disc space narrowing was observed at 6 months in the discs adjacent to the subchondral bone injected with PYM, compared with the control groups (p<.05). The magnetic resonance imaging assessment also demonstrated a progressive loss of T2-weighted signal intensity postoperatively. The histological score increased significantly compared with that of the control groups from 3 months to the end point (p<.05). The bone tissue area of the end plate increased significantly at the end point, compared with that of the control groups (p<.05). The results of molecular analysis showed significant increase of matrix metalloproteinase-3, a disintegrin and metalloproteinase with thrombospondin motif-5, and marked reduction of aggrecan and Type II collagen after 3 months at the messenger RNA levels in the discs of PYM group (p<.05). The von Willebrand factor expression of PYM group also showed a significant reduction after 1 month (p<.05).

CONCLUSIONS

Percutaneous injection of PYM into the subchondral bone adjacent to the lumbar IVDs of rabbits, using bone marrow needle guided by CT scan, can result in ischemic and slowly progressive disc degeneration model, which mimics the onset of human disc degeneration.

The establishment and biological assessment of a whole tissue-engineered intervertebral disc with PBST fibers and a chitosan hydrogel in vitro and in vivo

Intervertebral disc (IVD) degeneration (IDD) is the main cause of low back pain in the clinic. In the advanced stage of IDD, both cell transplantation and gene therapy have obvious limitations. At this stage, tissue-engineered IVDs (TE-IVDs) provide new hope for the treatment of this disease. We aimed to construct a TE-IVD with a relatively complete structure. The inner annulus fibrosus (AF) was constructed using poly (butylene succinate-co-terephthalate) copolyester (PBST) electrospun fibers, and the outer AF consisted of solid PBST. The nucleus pulposus (NP) scaffold was constructed using a chitosan hydrogel, as reported in our previous research. The three components were assembled in vitro, and the mechanical properties were analyzed. AF and NP cells were implanted on the corresponding scaffolds. Then, the cell-seeded scaffolds were implanted subcutaneously in nude mice and cultured for 4 weeks; then they were removed and implanted into New Zealand white rabbits. After 4 weeks, their properties were analyzed. The PBST outer AF provided mechanical support for the whole TE-IVD. The electrospun film and chitosan hydrogel simulated the natural structure of the IVD well. Its mechanical property could meet the requirement of the normal IVD. Four weeks later, X-ray and MR imaging examination results suggested that the height of the intervertebral space was retained. The cells on the TE-IVD expressed extracellular matrix, which indicated that the cells maintained their biological function. Therefore, we conclude that the whole TE-IVD has biological and biomechanical properties to some extent, which is a promising candidate for IVD replacement therapies. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2305-2316, 2019.

Therapeutic effects of cell therapy with neonatal human dermal fibroblasts and rabbit dermal fibroblasts on disc degeneration and inflammation

BACKGROUND CONTEXT

Increasing evidence suggests transplanting viable cells into the degenerating intervertebral disc (IVD) may be effective in treating disc degeneration and back pain. Clinical studies utilizing autologous or allogeneic mesenchymal stem cells to treat patients with back pain have reported some encouraging results. Animal studies have shown that cells injected into the disc can survive for months and have regenerative effects. Studies to determine the advantages and disadvantages of cell types and sources for therapy are needed.

PURPOSE

The objective of this study is to determine the impact of donor source on the therapeutic effects of dermal fibroblast treatment on disc degeneration and inflammation.

STUDY DESIGN

Using the rabbit disc degeneration model, we compared transplantation of neonatal human dermal fibroblasts (nHDFs) and rabbit dermal fibroblasts (RDFs) into rabbit degenerated discs on host immune response, disc height, and IVD composition.

METHODS

New Zealand white rabbits received an annular puncture using an 18-guage needle to induce disc degeneration. Four weeks after injury, rabbit IVDs were treated with 5 × 10⁶ nHDFs, RDFs, or saline. At eight weeks post-treatment, animals were sacrificed. X-ray images were obtained. IVDs were isolated for inflammatory and collagen gene expression analysis using real-time polymerase chain reaction and biochemical analysis of proteoglycan contents using dimethylmethylene blue assay. These studies were funded by a research grant from SpinalCyte, LLC ($414,431).

RESULTS

Eight weeks after treatment, disc height indexes of discs treated with nHDF increased significantly by 7.8% (p<.01), whereas those treated with saline or RDF increased by 1.5% and 2.0%, respectively. Gene expression analysis showed that discs transplanted with nHDFs and RDFs displayed similar inflammatory responses (p=.2 to .8). Compared to intact discs, expression of both collagen types I and II increased significantly in nHDF-treated discs (p<.05), trending to significant in RDF-treated discs, and not significantly in saline treated discs. The ratio of collagen type II/collagen type I was higher in the IVDs treated with nHDFs (1.26) than those treated with RDFs (0.81) or saline (0.59) and intact discs (1.00). Last, proteoglycan contents increased significantly in discs treated with nHDF (p<.05) and were trending toward significance in the RDF-treated discs compared to those treated with saline.

CONCLUSIONS

This study showed that cell transplantation with nHDF into degenerated IVDs can significantly increase markers of disc regeneration (disc height, collagen type I and II gene expression, and proteoglycan contents). Transplantation with RDFs showed similar regenerative trends, but these trends were not significant. This study also showed that the human cells transplanted into the rabbit discs did not induce a higher immune response than the rabbit cells. These results support that the IVD is immune privileged and would tolerate allogeneic or xenogeneic grafts.

In vivo annular repair using high-density collagen gel seeded with annulus fibrosus cells

OBJECTIVE

The aim is assessing the in vivo efficacy of annulus fibrosus (AF) cells seeded into collagen by enhancing the reparative process around annular defects and preventing further degeneration in a rat-tail model.

SUMMARY OF BACKGROUND DATA

Treating disc herniation with discectomy may relieve the related symptoms but does not address the underlying pathology. The persistent annular defect may lead to re-herniation and further degeneration. We recently demonstrated that riboflavin crosslinked high-density collagen gels (HDC) can facilitate annular repair in vivo.

METHODS

42 rats, tail disc punctured with an 18-gauge needle, were divided into 3 groups: untreated (n = 6), injected with crosslinked HDC (n = 18), and injected with AF cell-laden crosslinked HDC (n = 18). Ovine AF cells were mixed with HDC gels prior to injection. X-rays and MRIs were conducted over 5 weeks, determining disc height index (DHI), nucleus pulposus (NP) size, and hydration. Histological assessments evaluated the viability of implanted cells and degree of annular repair.

RESULTS

Although average DHIs of both HDC gel groups were higher than those of the puncture control group at 5 weeks, the retention of disc height, NP size and hydration at 1 and 5 weeks was significant for the cellular group compared to the punctured, and at 5 weeks to the acellular group. Histological assessment indicated that AF cell-laden HDC gels have accelerated reparative sealing compared to acellular HDC gels.

CONCLUSIONS

AF cell-laden HDC gels have the ability of better repairing annular defects than acellular gels after needle puncture.

STATEMENT OF SIGNIFICANCE

This project addresses the compelling demand of a sufficient treatment strategy for degenerative disc disease (DDD) perpetuated by annulus fibrosus (AF) injury, a major cause of morbidity and burden to health care systems. Our study is designed to answer the question of whether injectable, photo-crosslinked, high density collagen gels can seal defects in the annulus fibrosus of rats and prevent disc degeneration. Furthermore, we investigated whether the healing of AF defects will be enhanced by the delivery of AF cells (fibrochondrocytes) to these defects. The use of cell-laden collagen gels in spine surgery holds promise for a wide array of applications, from current discectomy procedures to future nucleus pulposus reparative therapies, and our group is excited about this potential.

Annulus Fibrosus Repair Using High-Density Collagen Gel: An In Vivo Ovine Model

STUDY DESIGN

Ovine in vivo study.

OBJECTIVE

To perform lateral approach lumbar surgery in an ovine model to administer an injectable riboflavin cross-linked high-density collagen (HDC) gel and to assess its ability to mitigate intervertebral disc (IVD) degeneration after induced annulus fibrosus (AF) injury.

SUMMARY OF BACKGROUND DATA

Biological-based injectable gels have shown efficacy in restoring biomechanical, radiographic, and histological parameters in IVD-injured animal models. Riboflavin cross-linked HDC gel has previously demonstrated retention of nucleus pulposus (NP) tissue, reduced loss of disc height, and prevention of terminal cellular degenerative changes in rat-tail spines. However, this biological therapy has never been tested in large animal models.

METHODS

Forty lumbar IVDs were accessed from eight sheep via lateral approach surgery. IVDs were randomly assigned to healthy control, injury and HDC treatment, or negative control with injury and no treatment. IVD injury was carried out using a drill-bit through the AF followed by needle puncture of the NP. Sheep were followed for 16 weeks and underwent qualitative/quantitative magnetic resonance imaging, x-ray, and histological analyses of collagen and proteoglycan content.

RESULTS

The lateral approach to the ovine lumbar spine to deliver HDC gel proved to be safe and reproducible. IVDs treated with the HDC gel revealed less degenerative changes at the microscopic level based on AF and NP histology. However, mean Pfirrmann grade, T2 relaxation time, NP voxel size, and disc height index were not significantly different between the two injury groups.

CONCLUSION

Injectable HDC gel can be administered safely via lateral approach surgery in an ovine AF injury model. IVDs treated with HDC gel demonstrated less degeneration at the microscopic level though radiographic changes were slight when comparing treated to untreated IVDs. Future studies will need to elucidate the role of injury technique and time frame for follow-up in correlating histological and radiographical outcomes.

LEVEL OF EVIDENCE

N /A.

Prolactin inhibits the progression of intervertebral disc degeneration through inactivation of the NF-κB pathway in rats

Intervertebral disc degeneration (IVDD) is one of the key predisposing factors for low back pain. Although the exact mechanism remains unclear, inflammatory response and nucleus pulposus (NP) apoptosis are known to play important roles in this process. Prolactin protects against inflammation-associated chondrocyte apoptosis in arthritis. Based on prior studies, we hypothesized that prolactin might have therapeutic effects on IVDD by inhibiting the apoptosis of degenerative human disc NP cells. An experimental model of IVDD was established in 3-month-old Sprague-Dawley rats by submitting them to percutaneous disc puncture with a 20-gauge needle on levels 7–8 and 8–9 of the coccygeal vertebrae. Then the rats were injected with 20 or 200 ng prolactin on a weekly basis. Radiologic and histologic analyses were performed on days 4, 7, 14, and 28. The expression of prolactin and its receptor was analyzed in human tissue obtained from symptomatic patients undergoing microencoscopy discectomy, or from scoliosis patients undergoing deformity correction surgery. The results showed that intradiscal injection of prolactin maintained disc height and the mean signal intensity of the punctured disc. Histological analysis indicated that prolactin treatment significantly retained the complete structure of the NP and annulus fibrosus compared with the vehicle group. In addition, more collagen II, but fewer collagen I-containing tissues were detected in the prolactin treatment groups compared to the vehicle group. Moreover, low levels of tumor necrosis factor-α, interleukin-1β, cleaved-caspase 3, and TUNEL staining were observed in the prolactin treatment groups. We also demonstrated that prolactin impaired puncture-induced inflammation and cell apoptosis by downregulating activation of the NF-κB pathway. The degenerated NP tissues from patients had decreased expression of prolactin and its receptor, whereas expression was increased in the NP tissues removed from scoliosis patients. These results suggest that prolactin may be a novel therapeutic target for the treatment of IVDD.

Biologic Annulus Fibrosus Repair: A Review of Preclinical In Vivo Investigations

Lower back pain, the leading cause of workplace absences and disability, is often attributed to intervertebral disc degeneration, in which nucleus pulposus (NP) herniates through lesions in the annulus fibrosus (AF) and impinges on the spinal cord and surrounding nerves. Surgeons remove extruded NP via discectomy when indicated by local/radicular pain supported by radiographic evidence; however, current interventions do not alter the underlying disease or seal the AF. The reported rates of recurrent herniation or pain following discectomy cases range from 5% to 25%, which has pushed spine research in recent years toward annular repair and closure strategies. Synthetic implants designed to mechanically seal the AF have been subject to large animal and clinical trials, with limited success in preventing recurrent herniation. Like gold standard interventions, purely mechanical devices fail to promote tissue integration, long-term healing, or restore native biomechanical function to the spine. Biological repair strategies utilizing principles of tissue engineering have demonstrated success in overcoming the inadequacies of current interventions and mechanical implants, yet, none has reached clinical or proof-of-concept trials in humans. In this review, we will discuss annular repair strategies promoting biological healing that have been implemented in small and large animal models in vivo, and ways to enhance the efficacy of these treatments.

Total disc replacement using tissue-engineered intervertebral discs in the canine cervical spine

The most common reason that adults in the United States see their physician is lower back or neck pain secondary to degenerative disc disease. To date, approaches to treat degenerative disc disease are confined to purely mechanical devices designed to either eliminate or enable flexibility of the diseased motion segment. Tissue engineered intervertebral discs (TE-IVDs) have been proposed as an alternative approach and have shown promise in replacing native IVD in the rodent tail spine. Here we demonstrate the efficacy of our TE-IVDs in the canine cervical spine. TE-IVD components were constructed using adult canine annulus fibrosis and nucleus pulposus cells seeded into collagen and alginate hydrogels, respectively. Seeded gels were formed into a single disc unit using molds designed from the geometry of the canine spine. Skeletally mature beagles underwent discectomy with whole IVD resection at levels between C3/4 and C6/7, and were then divided into two groups that received only discectomy or discectomy followed by implantation of TE-IVD. Stably implanted TE-IVDs demonstrated significant retention of disc height and physiological hydration compared to discectomy control. Both 4-week and 16-week histological assessments demonstrated chondrocytic cells surrounded by proteoglycan-rich matrices in the NP and by fibrocartilaginous matrices in the AF portions of implanted TE-IVDs. Integration into host tissue was confirmed over 16 weeks without any signs of immune reaction. Despite the significant biomechanical demands of the beagle cervical spine, our stably implanted TE-IVDs maintained their position, structure and hydration as well as disc height over 16 weeks in vivo.

Degenerative changes of the canine cervical spine after discectomy procedures, an in vivo study

BACKGROUND

Discectomies are a common surgical treatment for disc herniations in the canine spine. However, the effect of these procedures on intervertebral disc tissue is not fully understood. The objective of this study was to assess degenerative changes of cervical spinal segments undergoing discectomy procedures, in vivo.

RESULTS

Discectomies led to a 60% drop in disc height and 24% drop in foraminal height. Segments did not fuse but showed osteophyte formation as well as endplate sclerosis. MR imaging revealed terminal degenerative changes with collapse of the disc space and loss of T2 signal intensity. The endplates showed degenerative type II Modic changes. Quantitative MR imaging revealed that over 95% of Nucleus Pulposus tissue was extracted and that the nuclear as well as overall disc hydration significantly decreased. Histology confirmed terminal degenerative changes with loss of NP tissue, loss of Annulus Fibrosus organization and loss of cartilage endplate tissue. The bony endplate displayed sclerotic changes.

CONCLUSION

Discectomies lead to terminal degenerative changes. Therefore, these procedures should be indicated with caution specifically when performed for prophylactic purposes.

Whole-body vibration of mice induces progressive degeneration of intervertebral discs associated with increased expression of Il-1β and multiple matrix degrading enzymes

OBJECTIVE

Whole-body vibration (WBV) is a popular fitness trend based on claims of increased muscle mass, weight loss and reduced joint pain. Following its original implementation as a treatment to increase bone mass in patients with osteoporosis, WBV has been incorporated into clinical practice for musculoskeletal disorders, including back pain. However, our recent studies revealed damaging effects of WBV on joint health in a murine model. In this report, we examined potential mechanisms underlying disc degeneration following exposure of mice to WBV.

METHODS

Ten-week-old male mice were exposed to WBV (45 Hz, 0.3 g peak acceleration, 30 min/day, 5 days/week) for 4 weeks, 8 weeks, or 4 weeks WBV followed by 4 weeks recovery. Micro-computed tomography (micro-CT), histological, and gene expression analyses were used to assess the effects of WBV on spinal tissues.

RESULTS

Exposure of mice to 4 or 8 weeks of WBV did not alter total body composition or induce significant changes in vertebral bone density. On the other hand, WBV-induced intervertebral disc (IVD) degeneration, associated with decreased disc height and degenerative changes in the annulus fibrosus (AF) that did not recover within 4 weeks after cessation of WBV. Gene expression analysis showed that WBV for 8 weeks induced expression of Mmp3, Mmp13, and Adamts5 in IVD tissues, changes preceded by increased expression of Il-1β.

CONCLUSIONS

Progressive IVD degeneration induced by WBV was associated with increased expression of Il-1β within the IVD that preceded Mmp and Adamts gene induction. Moreover, WBV-induced IVD degeneration is not reversed following cessation of vibration.

A large animal model that recapitulates the spectrum of human intervertebral disc degeneration

OBJECTIVE

The objective of this study was to establish a large animal model that recapitulates the spectrum of intervertebral disc degeneration that occurs in humans and which is suitable for pre-clinical evaluation of a wide range of experimental therapeutics.

DESIGN

Degeneration was induced in the lumbar intervertebral discs of large frame goats by either intradiscal injection of chondroitinase ABC (ChABC) over a range of dosages (0.1U, 1U or 5U) or subtotal nucleotomy. Radiographs were used to assess disc height changes over 12 weeks. Degenerative changes to the discs and endplates were assessed via magnetic resonance imaging (MRI), semi-quantitative histological grading, microcomputed tomography (μCT), and measurement of disc biomechanical properties.

RESULTS

Degenerative changes were observed for all interventions that ranged from mild (0.1U ChABC) to moderate (1U ChABC and nucleotomy) to severe (5U ChABC). All groups showed progressive reductions in disc height over 12 weeks. Histological scores were significantly increased in the 1U and 5U ChABC groups. Reductions in T2 and T1ρ, and increased Pfirrmann grade were observed on MRI. Resorption and remodeling of the cortical boney endplate adjacent to ChABC-injected discs also occurred. Spine segment range of motion (ROM) was greater and compressive modulus was lower in 1U ChABC and nucleotomy discs compared to intact.

CONCLUSIONS

A large animal model of disc degeneration was established that recapitulates the spectrum of structural, compositional and biomechanical features of human disc degeneration. This model may serve as a robust platform for evaluating the efficacy of therapeutics targeted towards varying degrees of disc degeneration.

Cell Therapy with Human Dermal Fibroblasts Enhances Intervertebral Disk Repair and Decreases Inflammation in the Rabbit Model

Study Design Pilot study using the rabbit model. Objective Low back pain is often associated with disk degeneration. Cell therapy for degenerating disks may promote tissue regeneration and repair. Human dermal fibroblasts, obtained from the patient's skin tissue or donated tissue, may be a promising cell therapy option for degenerating disks. The objective of these studies is to determine the effects of intradiscal transplantation of neonatal human dermal fibroblasts (nHDFs) on intervertebral disk (IVD) degeneration by measuring disk height, magnetic resonance imaging (MRI) signal intensity, gene expression, and collagen immunostaining. Methods New Zealand white rabbits (n = 16) received an annular puncture to induce disk degeneration and were treated with nHDFs or saline 4 weeks later. At 2 and 8 weeks post-treatment, X-ray and MRI images were obtained. IVDs were isolated and examined for changes in collagen staining and gene expression. Results In the nHDF-treated group, there was a 10% increase in the disk height index after 8 weeks of treatment (p ≤ 0.05), and there was no significant difference in the saline-treated group. When compared with the saline-treated disks, disks treated with nHDFs showed reduced expression of inflammatory markers, a higher ratio of collagen type II over collagen type I gene expression, and more intense immunohistochemical staining for both collagen types I and II. Conclusions Human dermal fibroblast introduction into the disk reduced inflammation and promoted tissue rich in both type I and type II collagens. The results of this study suggest that nHDFs would be a feasible cell therapy option for disk degeneration.

Organ culture bioreactors--platforms to study human intervertebral disc degeneration and regenerative therapy

In recent decades the application of bioreactors has revolutionized the concept of culturing tissues and organs that require mechanical loading. In intervertebral disc (IVD) research, collaborative efforts of biomedical engineering, biology and mechatronics have led to the innovation of new loading devices that can maintain viable IVD organ explants from large animals and human cadavers in precisely defined nutritional and mechanical environments over extended culture periods. Particularly in spine and IVD research, these organ culture models offer appealing alternatives, as large bipedal animal models with naturally occurring IVD degeneration and a genetic background similar to the human condition do not exist. Latest research has demonstrated important concepts including the potential of homing of mesenchymal stem cells to nutritionally or mechanically stressed IVDs, and the regenerative potential of "smart" biomaterials for nucleus pulposus or annulus fibrosus repair. In this review, we summarize the current knowledge about cell therapy, injection of cytokines and short peptides to rescue the degenerating IVD. We further stress that most bioreactor systems simplify the real in vivo conditions providing a useful proof of concept. Limitations are that certain aspects of the immune host response and pain assessments cannot be addressed with ex vivo systems. Coccygeal animal disc models are commonly used because of their availability and similarity to human IVDs. Although in vitro loading environments are not identical to the human in vivo situation, 3D ex vivo organ culture models of large animal coccygeal and human lumbar IVDs should be seen as valid alternatives for screening and feasibility testing to augment existing small animal, large animal, and human clinical trial experiments.

The effects of human Wharton's jelly cell transplantation on the intervertebral disc in a canine disc degeneration model

Introduction

Cell-based therapy was a promising treatment method for disc degenerative diseases. Wharton’s jelly cell (WJC) has been explored to cure various human diseases, while it still remains unknown about this MSC for disc repair. In our prior work, WJCs could differentiate into nucleus pulposus (NP)-like cells by co-culturing with NP cells in vitro. Thence, the aim of this study was further to investigate the survival and function of WJCs in vivo after transplantation into degenerated canine discs.

Method

WJCs were isolated from human umbilical cords and labeled with EGFP. The degeneration of L4-5, L5-6, and L6-7 discs of beagles was induced by aspirating the NP tissues. Four weeks after the operation, the injured discs were left to be no treatment at L4-5 (DS group), injected with 0.9 % saline at L5-6 (FS group), and transplanted with EGFP-labeled WJCs at L6-7 (TS group). In all animals, the intact disc L3-4 served as a control (CS group). The animals were followed up for 24 weeks after initial operation. Spine imaging was evaluated at 4, 8, 12, and 24 weeks, respectively. Histologic, biomechanics and gene expression analyses were performed at 24 weeks. Immunohistochemistry for aggrecan, types II collagen, SOX-9 was employed to investigate the matrix formation in the NP.

Results

The TS group showed a significantly smaller reduction in the disc height and T2-weighted signal intensity, and a better spinal segmental stability than DS and FS groups. Histologic assay demonstrated that WJCs were specifically detected in TS group at 24 weeks and the discs of TS group maintained a relatively well preserved structure as compared to the discs of DS and FS groups. Furthermore, real-time PCR and immunohistochemistry demonstrated that expressions of disc matrix genes, aggrecan, type II collagen, and SOX-9, were up-regulated in TS group compared to DS and FS groups.

Conclusion

WJCs could not only survive in the degenerate IVDs, but also promote the disc matrix formation of aggrecan and type II collagen in the degenerate IVDs. It may have value in cell-based therapy for degenerative disc disease.

Injectable microcryogels reinforced alginate encapsulation of mesenchymal stromal cells for leak-proof delivery and alleviation of canine disc degeneration

In situ crosslinked thermo-responsive hydrogel applied for minimally invasive treatment of intervertebral disc degeneration (IVDD) may not prevent extrusion of cell suspension from injection site due to high internal pressure of intervertebral disc (IVD), causing treatment failure or osteophyte formation. In this study, mesenchymal stromal cells (MSCs) were encapsulated in alginate precursor and loaded into previously developed macroporous PGEDA-derived microcryogels (PMs) to form three-dimensional (3D) microscale cellular niches, enabling non-thermo-responsive alginate hydrogel to be injectable. The PMs reinforced alginate hydrogel showed superior elasticity compared to alginate hydrogel alone and could well protect encapsulated cells through injection. Chondrogenic committed MSCs in the injectable microniches expressed higher level of nucleus pulposus (NP) cell markers compared to 2D cultured cells. In an ex vivo organ culture model, injection of MSCs-laden PMs into NP tissue prevented cell leakage, improved cell retention and survival compared to free cell injection. In canine IVDD models, alleviated degeneration was observed in MSCs-laden PMs treated group after six months which was superior to other treated groups. Our results provide in-depth demonstration of injectable alginate hydrogel reinforced by PMs as a leak-proof cell delivery system for augmented regenerative therapy of IVDD in canine models.

Increase or decrease in stability after nucleotomy? Conflicting in vitro and in vivo results in the sheep model

Nucleotomy is a common surgical procedure to treat disc herniations. The potential occurrence of segmental instability after surgery, however, is suspected to necessitate re-operation and fusion. Although in vitro studies support the theory of destabilization after nucleotomy, a prior, in-house animal study contrarily revealed an increase in stability after surgery. To identify which structural compartment of the motion segment is decisive for increased stability after nucleotomy in vivo, the flexibilities of ovine motion segments were measured after different stepwise reductions at the anterior and posterior spinal column. Different test groups were used in which nucleotomy had been performed during surgery in vivo and under isolated in vitro conditions, respectively. In accordance with expectations, in vitro nucleotomy on ovine motion segments significantly increased flexibility. By contrast, nucleotomy significantly decreased flexibility 12 weeks after surgery. After removal of the posterior structures, however, the differences in flexibility diminished. The present results thus suggest that it might not exclusively be the trauma to the intervertebral disc during surgery which is decisive for post-operative stability, but rather adaptive mechanisms in the posterior structures. Therefore, care should be taken to minimize the damage to the posterior structures in the course of the surgical approach, which more likely compromises stability.

Gene therapy for nucleus pulposus regeneration by heme oxygenase-1 plasmid DNA carried by mixed polyplex micelles with thermo-responsive heterogeneous coronas

Safe and high-efficiency gene therapy for nucleus pulposus (NP) regeneration was urgently desired to treat disc degeneration-associated diseases. In this work, an efficient nonviral cationic block copolymer gene delivery system was used to deliver therapeutic plasmid DNA (pDNA), which was prepared via complexation between the mixed cationic block copolymers, poly(ethylene glycol)-block-poly{N-[N-(2-aminoethyl)-2-aminoehtyl]aspartamide} [PEG-b-PAsp(DET)] and poly(N-isopropylacrylamide)-block-PAsp(DET) [PNIPAM-b-PAsp(DET)], and pDNA at 25 °C. The mixed polyplex micelles (MPMs) containing heterogeneous coronas with hydrophobic and hydrophilic microdomains coexisting could be obtained upon heating from 25 to 37 °C, which showed high tolerability against nuclease and strong resistance towards protein adsorption. The gene transfection efficiency of MPMs in NP cells was significantly higher than that of regular polyplex micelles prepared from sole block copolymer of PEG-b-PAsp(DET) (SPMs) in in vitro and in vivo evaluation due to the synergistic effect of improved colloidal stability and low cytotoxicity. High expression of heme oxygenase-1 (HO-1) in NP cells transfected by MPMs loading HO-1 pDNA significantly decreased the expression activity of matrix metalloproteinases 3 (MMP-3) and cyclo-oxygenase-2 (COX-2) induced by interleukin-1β (IL-1β), and simultaneously increased the NP phenotype-associated genes such as aggrecan, type II collagen, and SOX-9. Moreover, the therapeutic effects of MPMs loading pDNA were tested to treat disc degeneration induced by stab injury. The results demonstrated that administration of HO-1 pDNA carried by MPMs in rat tail discs apparently reduced inflammatory responses induced by need stab and increased glycosaminoglycan (GAG) content, finally achieving better therapeutic efficacy as compared with SPMs. Consequently, MPMs loading HO-1 pDNA were demonstrated to be potential as a safe and high-efficiency nonviral gene delivery system for retarding or regenerating the degenerative discs.

Pingyangmycin-induced in vivo lumbar disc degeneration model of rhesus monkeys

STUDY DESIGN

Animal experimental study.

OBJECTIVE

To establish a slowly progressive and reproducible intervertebral disc degeneration model and determine the performance of T1ρ magnetic resonance imaging in the evaluation of disc degeneration.

SUMMARY OF BACKGROUND DATA

Recently, one of the hotspots of research efforts was related to management of early stage of disc degeneration. To our knowledge, a functional animal model that mimics ischemic and slowly progressive disc degeneration of humans does not exist.

METHODS

The subchondral bone adjacent to the lumbar intervertebral discs (from L3-L4 to L6-L7) of 8 rhesus monkeys was randomly injected with 4 mL of Pingyangmycin (PYM) solution (1.5 mg/mL, PYM), or 4 mL of phosphate buffered saline (Vehicle control), or exteriorized but not injected anything (Sham), respectively. The degenerative process was investigated by using radiography and T1ρ magnetic resonance imaging at 1, 3, 6, 9, 12, and 15 months postoperatively. Histological scoring, immunohistochemistry, and real-time polymerase chain reaction were performed at 15 months.

RESULTS

The mean T1ρ values of nucleus pulposus and annulus fibrosus in the PYM group significantly decreased after 3 and 6 months, respectively, followed by slow decrease, and the histological score was significantly higher at 15 months, compared with the control groups. The results of molecular analysis revealed a significant increase matrix metalloprotease-3, A disintegrin and metalloproteinase with thrombospondin motifs -5, tumor necrosis factor α, interleukin-1β, interleukin-6 expressions, and marked reduction in aggrecan, type II collagen, von Willebrand factor expressions at the messenger RNA levels in the PYM group. Spearman correlation analysis of Pfirrmann grades showed significantly inverse correlation with T1ρ values of nucleus pulposus and annulus fibrosus (r = -0.634, -0.617, respectively, P < 0.01).

CONCLUSION

Injection of PYM into the subchondral bone adjacent to the lumbar intervertebral discs of rhesus monkeys can results in mild, slowly progressive disc degeneration, which mimics the onset of human disc degeneration, and the T1ρ magnetic resonance imaging is suited for evaluating intervertebral disc degeneration.

LEVEL OF EVIDENCE

N/A.

Chondroitinase: A promising therapeutic enzyme

Even after 20 years of granting orphan status for chondroitinase by US FDA, there is no visible outcome in terms of clinical use. The reasons are many. One of them could be lack of awareness regarding the biological application of the enzyme. The biological activity of chondroitinase is due to its ability to act on chondroitin sulfate proteoglycans (CSPGs). CSPGs are needed for normal functioning of the body. An increase or decrease in the level of CSPGs results in various pathological conditions. Chondroitinase is useful in conditions where there is an increase in the level of CSPGs, namely spinal cord injury, vitreous attachment and cancer. Over the last decade, various animal studies showed that chondroitinase could be a good drug candidate. Research focusing on developing a suitable carrier system for delivering chondroitinase needs to be carried out so that pharmacological activity observed in vitro and preclinical studies could be translated to clinical use. Further studies on distribution of chondroitinase as well need to be focused so that chondroitinase with desired attributes could be discovered. The present review article discusses about various biological applications of chondroitinase, drug delivery systems to deliver the enzyme and distribution of chondroitinase among microbes.

In vivo experimental intervertebral disc degeneration induced by bleomycin in the rhesus monkey

Background

Recently, biological therapies for early intervention of degenerative disc disease have been introduced and developed; however, a functional animal model that mimics slowly progressive disc degeneration of humans does not exist. The objective of this study was to establish a slowly progressive and reproducible intervertebral disc (IVD) degeneration model.

Methods

The subchondral bone adjacent to the lumbar IVDs (L3/4 and L5/6) of ten rhesus monkeys was randomly injected with 4 ml bleomycin solution (1.5 mg/ml), or 4 ml phosphate buffer saline (PBS) per segment as control, respectively. The degenerative process was investigated by using radiography and T1ρ MR imaging at 1, 3, 6, 9, 12 and 15 months postoperatively. Histological scoring, Sulfated Glycosaminoglycans (GAGs) analysis and real-time PCR were performed at 15 months. The correlation between histological score, GAGs and T1ρ values were also analyzed.

Results

The results showed that the mean T1ρ values of nucleus pulposus (NP) and annulus fibrosus (AF) in the bleomycin group significantly decreased after 3 and 6 months respectively, followed by slowly decrease until at 15 months. At 15 months, the histological scores was significantly higher, and the GAGs of NP was significantly lower in the bleomycin group, compared with the control group (P < 0.05). The results of real-time PCR revealed a significant increase in matrix metalloprotease (MMP)-3, A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5, tumor necrosis factor α, interleukin-1β, interleukin-6 expressions, transforming growth factor (TGF-β1) and marked reduction in aggrecan, type II collagen, von willebrand factor (vWF) expressions at the mRNA levels in the bleomycin group. Spearman correlation analysis showed a strong positive correlation between GAGs and T1ρ values of NP (r =0.740, P < 0.01), and a significant inverse correlation between histological score and T1ρ values of NP and AF (r = -0.761, r = -0.729, respectively, P < 0.01).

Conclusions

Injection of bleomycin into the subchondral bone adjacent to the lumbar IVDs of rhesus monkeys can results in mild, slowly progressive disc degeneration, which mimics the onset of human disc degeneration. T1ρ MR imaging is an effective and noninvasive technique for assessment of early stage disc degeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-340) contains supplementary material, which is available to authorized users.

Intervertebral disc height loss demonstrates the threshold of major pathological changes during degeneration

PURPOSE

Quantitative MRI techniques were utilized to study intervertebral disc degeneration. Main focus was to develop a novel approach to quantify disc height loss associated with disc degeneration. Currently there is no universally accepted metric of degeneration based on measurement of disc height. Such quantitative imaging methods would complement qualitative visual assessment methods currently used and offer a valuable diagnostic tool.

METHODS

51 adult participants took part in this MRI study. T2 weighted images were used to obtain disc height index (DHI) and also a semi-quantitative metric based on relative voxel intensities. For DHI, each disc was given a score based on standard deviations from the mean DHI of healthy discs. Diffusion Weighted MRI was used to assess morphological changes in the nucleus pulposus. Conventional Pfirrmann classification was used as the gold standard to assess these quantitative approaches.

RESULTS

At deviations of up to 1.5σ below normative disc height, levels of apparent diffusion coefficient (ADC) and normalized T2 intensity were maintained. Once disc compression reached 1.5σ, there was a massive drop in ADC and normalized T2 intensity. Pfirrmann degeneration scores also increased after the 1.5σ mark.

CONCLUSIONS

This study provides new, unbiased quantitative imaging tools to assess disc degeneration. We observed that these quantitative MRI measures indicate a threshold beyond which major pathological changes take place concurrently. Combined information from DHI, ADC and T2 images construct a set of novel biomarkers that could be used to identify degenerating discs that are approaching the threshold and possibly intervene before major pathologic changes occur.

Evaluation of intervertebral disc regeneration with implantation of bone marrow mesenchymal stem cells (BMSCs) using quantitative T2 mapping: a study in rabbits

PURPOSE

The aim of the study was to investigate the curative effects of transplantation of bone marrow mesenchymal stem cells (BMSCs) on intervertebral disc regeneration and to investigate the feasibility of the quantitative T2 mapping method for evaluating repair of the nucleus pulposus after implantation of BMSCs.

METHODS

Forty-eight New Zealand white rabbits were used to establish the lumber disc degenerative model by stabbing the annulus fibrosus and then randomly divided into four groups, i.e. two weeks afterwards, BMSCs or phosphate-buffered saline (PBS) were transplanted into degenerative discs (BMSCs group and PBS group), while the operated rabbits without implantation of BMSCs or PBS served as the sham group and the rabbits without operation were used as the control group. At weeks two, six and ten after operation, the T2 values and disc height indices (DHI) were calculated by magnetic resonance imaging (MRI 3.0 T), and the gene expressions of type II collagen (COL2) and aggrecan (ACAN) in degenerative discs were evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR). T2 values for the nucleus pulposus were correlated with ACAN or COL2 expression by regression analysis.

RESULTS

Cell clusters, disorganised fibres, interlamellar glycosaminoglycan (GAG) matrix and vascularisation were observed in lumber degenerative discs. BMSCs could be found to survive in intervertebral discs and differentiate into nucleus pulposus-like cells expressing COL2 and ACAN. The gene expression of COL2 and ACAN increased during ten weeks after transplantation as well as the T2 signal intensity and T2 value. The DHI in the BMSCs group decreased more slowly than that in PBS and sham groups. The T2 value correlated significantly with the gene expression of ACAN and COL2 in the nucleus pulposus.

CONCLUSIONS

Transplantation of BMSCs was able to promote the regeneration of degenerative discs. Quantitative and non-invasive T2 mapping could be used to evaluate the regeneration of the nucleus pulposus with good sensitivity.

Experimental chemonucleolysis with recombinant human matrix metalloproteinase 7 in human herniated discs and dogs

BACKGROUND CONTEXT

Chemonucleolysis has been proposed as a less invasive technique than surgery for patients with lumbar disc herniation. Once chymopapain had been approved as a chemonucleolysis drug, it was withdrawn because of serious complications. A novel agent with fewer complications would be desirable.

PURPOSE

The purpose of this study was to investigate the effects of recombinant human matrix metalloproteinase 7 (rhMMP-7) in experimental chemonucleolysis in vitro and in vivo and examine its effects on tissue damage.

STUDY DESIGN

The study design is the experimental study using human herniated discs and enzyme substrates in vitro and dogs in vivo.

METHODS

The effects of rhMMP-7 on the degradation of human herniated discs were examined by measuring the wet weight in vitro. The correlations between the decrease in wet weight by rhMMP-7 and the conditions associated with herniated discs were also analyzed. The effects of rhMMP-7 on the proteoglycan and water contents were respectively examined with alcian blue staining and T2-weighted magnetic resonance imaging at 7 days after intradiscal injection in dogs. The distribution of [125I]-labeled rhMMP-7 was investigated by autoradioluminography at 7 days after intradiscal injection in dogs. An epidural injection study with rhMMP-7 was performed to evaluate the effects on the tissue damage around the discs at 1 and 13 weeks after the treatment in dogs. The Type 1 and 2 collagen cleavage rates were measured and compared with those of aggrecan in vitro.

RESULTS

Recombinant human matrix metalloproteinase 7 concentration dependently decreased the wet weight of herniated discs in vitro. The decrease in wet weight of the discs by rhMMP-7 did not significantly correlate with the conditions associated with herniated discs. Intradiscal injection of rhMMP-7 reduced the proteoglycan and water contents, with an increase in the serum keratan sulfate levels. Radioactivity of [125I]-labeled rhMMP-7 was detected in the nucleus pulposus and annulus fibrosus but not in the muscle. Epidural injection of rhMMP-7 had no effect on the injection site or the nerve tissues. The Type 1 and 2 collagen cleavage rates of rhMMP-7 were 1,000-fold weaker than those of aggrecan.

CONCLUSIONS

This study demonstrated experimental chemonucleolysis with rhMMP-7 in vitro and in vivo. The effects of rhMMP-7 were not affected by the conditions associated with herniated discs. The epidural injection study together with the autoradioluminography and in vitro enzyme assay suggests that intradiscal injection of rhMMP-7 may not induce tissue damage around the discs because of its distribution and substrate selectivity. Recombinant human matrix metalloproteinase 7 may be a novel and promising chemonucleolysis agent.

Assessment of intervertebral disc degeneration based on quantitative magnetic resonance imaging analysis: an in vivo study

STUDY DESIGN

Animal experimental study.

OBJECTIVE

To evaluate a novel quantitative imaging technique for assessing disc degeneration.

SUMMARY OF BACKGROUND DATA

T2-relaxation time (T2-RT) measurements have been used to assess disc degeneration quanti-tatively. T2 values correlate with the water content of intervertebral disc tissue and thereby allow for the indirect measurement of nucleus pulposus (NP) hydration.

METHODS

We developed an algorithm to subtract out magnetic resonance imaging (MRI) voxels not representing NP tissue on the basis of T2-RT values. Filtered NP voxels were used to measure nuclear size by their amount and nuclear hydration by their mean T2-RT. This technique was applied to 24 rat-tail intervertebral discs (IVDs), which had been punctured with an 18-gauge needle according to different techniques to induce varying degrees of degeneration. NP voxel count and average T2-RT were used as parameters to assess the degeneration process at 1 and 3 months postpuncture. NP voxel counts were evaluated against radiograph disc height measurements and qualitative MRI studies on the basis of the Pfirrmann grading system. Tails were collected for histology to correlate NP voxel counts to histological disc degeneration grades and to NP cross-sectional area measurements.

RESULTS

NP voxel count measurements showed strong correlations to qualitative MRI analyses (R = 0.79, P < 0.0001), histological degeneration grades (R = 0.902, P < 0.0001), and histological NP cross-sectional area measurements (R = 0.887, P < 0.0001).In contrast to NP voxel counts, the mean T2-RT for each punctured group remained constant between months 1 and 3. The mean T2-RTs for the punctured groups did not show a statistically significant difference from those of healthy IVDs (63.55 ms ± 5.88 ms mo 1 and 62.61 ms ± 5.02 ms) at either time point.

CONCLUSION

The NP voxel count proved to be a valid parameter to assess disc degeneration quantitatively in a needle puncture model. The mean NP T2-RT does not change significantly in needle-puncture-induced degenerated IVDs. IVDs can be segmented into different tissue components according to their innate T2-RT.

Annular repair using high-density collagen gel: a rat-tail in vivo model

STUDY DESIGN

Animal in vivo study.

OBJECTIVE

To test the capability of high-density collagen gel to repair annular defects.

SUMMARY OF BACKGROUND DATA

Annular defects are associated with spontaneous disc herniations and disc degeneration, which can lead to significant morbidity. Persistent annular defects after surgical discectomies can increase reherniation rates. Several synthetic and biological materials have been developed for annular repair. This is the first study to test an injectable biomaterial in vivo.

METHODS

We punctured caudal intervertebral discs in 42 athymic rats, using an 18-gauge needle to create an annular defect. High-density collagen (HDC), either alone or cross-linked with riboflavin (RF), was injected into the defect. There were 4 separate study groups: HDC, HDC cross-linked with either 0.25 mM RF or 0.50 mM RF, and a negative control that was punctured and not treated. The animals were followed for 5 weeks; radiographs were used to assess disc heights and magnetic resonance images were used to evaluate degenerative changes. We developed an algorithm on the basis of T2-relaxation time measurements to assess the size of the nucleus pulposus. Tails were collected for histological analysis to evaluate disc degeneration and measure the cross-sectional area of the nucleus pulposus.

RESULTS

After 5 weeks, the control and the uncross-linked HDC groups both showed signs of progressive degenerative changes with minimal or no residual nucleus pulposus tissue in the disc space. Cross-linking significantly improved the ability of HDC gels to repair annular defects. The 0.50 mM RF cross-linked group showed only a slight decrease in nuclear tissue when compared with healthy discs, with no signs of intervertebral disc (IVD) degeneration. The annulus fibrosus was partially repaired by a fibrous cap that bridged the defect. Host fibroblasts infiltrated and remodeled the injected collagen.

CONCLUSION

HDC is capable of repairing annular defects induced by needle puncture. The stiffness of HDC can be modified by riboflavin cross-linking and seems to positively affect the repair mechanism. These results need to be replicated in a larger animal model.

LEVEL OF EVIDENCE

N/A.

A minimally invasive rabbit model of progressive and reproducible disc degeneration confirmed by radiology, gene expression, and histology

Objective

To develop a simple, reproducible model of disc degeneration in rabbits through percutaneous annular puncture and to confirm the degree of degeneration over time.

Methods

Fifteen New Zealand white rabbits (4 to 5 months old and weighing approximately 3 to 3.5 kg each) underwent annular puncture of the L2-L3, L3-L4, and L4-L5 discs. Rabbits were sacrificed at 4, 8, or 20 weeks after puncture. For a longitudinal study to assess changes in disc height over time, serial X-rays were performed at 0, 2, 4, 8, and 20 weeks for rabbits in the 20-week group. Upon sacrifice, the whole spinal column and discs were extracted and analyzed with magnetic resonance imaging (MRI), real time reverse transcriptase-polymerase chain reaction, and histological staining.

Results

The X-rays showed a slow, progressive decrease in disc height over time. Significant disc space narrowing compared to preoperative disc height was observed during the time period (p<0.001). The MRI grade, aggrecan, and matrix metalloprotease-13 mRNA expression and hematoxylin and eosin/safranin O/anti-collagen II staining were consistently indicative of degeneration, supporting the results of the X-ray data.

Conclusion

Percutaneous annular puncture resulted in slow, reproducible disc degeneration that was confirmed by radiology, biochemistry, and histology. This in vivo model can be used to study and evaluate the safety and efficacy of biologic treatments for degenerative disc disease.