Inflammatory response of intervertebral disc cells is reduced by fibrin sealant scaffold in vitro

Pip5k1γ promotes anabolism of nucleus pulposus cells and intervertebral disc homeostasis by activating CaMKII-Ampk pathway in aged mice

Degenerative disc disease (DDD) represents a significant global health challenge, yet its underlying molecular mechanisms remain elusive. This study aimed to investigate the role of type 1 phosphatidylinositol 4-phosphate 5-kinase (Pip5k1) in intervertebral disc (IVD) homeostasis and disease. All three Pip5k1 isoforms, namely Pip5k1α, Pip5k1β, and Pip5k1γ, were detectable in mouse and human IVD tissues, with Pip5k1γ displaying a highest expression in nucleus pulposus (NP) cells. The expression of Pip5k1γ was significantly down-regulated in the NP cells of aged mice and patients with severe DDD. To determine whether Pip5k1γ expression is required for disc homeostasis, we generated a Pip5k1γfl/fl; AggrecanCreERT2 mouse model for the conditional knockout of the Pip5k1γ gene in aggrecan-expressing IVD cells. Our findings revealed that the conditional deletion of Pip5k1γ did not affect the disc structure or cellular composition in 5-month-old adult mice. However, in aged (15-month-old) mice, this deletion led to several severe degenerative disc defects, including decreased NP cellularity, spontaneous fibrosis and cleft formation, and a loss of the boundary between NP and annulus fibrosus. At the molecular level, the absence of Pip5k1γ reduced the anabolism of NP cells without markedly affecting their catabolic or anti-catabolic activities. Moreover, the loss of Pip5k1γ significantly dampened the activation of the protective Ampk pathway in NP cells, thereby accelerating NP cell senescence. Notably, Pip5k1γ deficiency blunted the effectiveness of metformin, a potent Ampk activator, in activating the Ampk pathway and mitigating lumbar spine instability (LSI)-induced disc lesions in mice. Overall, our study unveils a novel role for Pip5k1γ in promoting anabolism and maintaining disc homeostasis, suggesting it as a potential therapeutic target for DDD.

Evaluation and comparison of the efficacy of autologous fibrin glue with 4-0 silk sutures in periodontal flap closure and wound healing - A split mouth randomized controlled trial

BACKGROUND

Fibrin glue has shown to be a pioneering remedy to overcome the inconvenience of suturing. Autologous products reduce the risk of contamination and immunological responses compared to commercial fibrin glue. Hence using autologous fibrin glue (AFG) as a tissue sealant in periodontal flap closure would be of added value for a predictable outcome.

OBJECTIVE

To evaluate and compare the efficacy of AFG with 4-0 silk sutures in periodontal flap closure and healing.

MATERIAL AND METHODS

Total of 17 patients diagnosed with generalized periodontitis in the age group of 18 to 60 years with probing pocket depth of ≥ 6 mm and clinical attachment level of ≥5 mm in at least two quadrants were categorized into test group (AFG) and control group (4-0 silk sutures). Primary outcome measures [modified gingival index (MGI), early wound index (EHI) and interleukin 1 beta (IL-1ß) and secondary outcome measures (oral hygiene index, plaque index and visual analog scale (VAS) were recorded at baseline, 1, 2, 3 and 4 weeks.

RESULTS

A statistically significant reduction of IL-1ß value (p =.005); MGI (p = .02); EHI (p = .004), VAS scores (p < .001) and a positive Spearman's correlation (rho = 0.15) was seen between EHI scores & IL-1ß levels in test group at 1week period in comparison to control group.

CONCLUSION

AFG showed promising results as an alternative to sutures. The use of AFG significantly improved clinical parameters and reduced the levels of pro-inflammatory cytokines making it an effective adhesive with healing properties in the era of suture-less periodontal flap surgery.

Investigation and Comparison of the Effect of TGF-β3, kartogenin and Avocado/Soybean Unsaponifiables on the In-vitro and In-vivo Chondrogenesis of Human Adipose-Derived Stem Cells on Fibrin Scaffold

Due to the lack of suitable therapeutic approaches to cartilage defect, the objective of this study was to determine the effect of Transforming growth factor-β3 (TGF-β3), avocado/soybean (ASU) and Kartogenin (KGN) on chondrogenic differentiation in human adipose-derived stem cells (hADSCs) on fibrin scaffold. hADSCs seeded in fibrin scaffold and cultured in chondrogenic media. These cells were divided into 4 groups (control, TGF-β3, ASU and KGN). Cell viability was estimated by MTT assay. Differentiated cells were evaluated by histological and immunohistochemical (IHC) techniques. Expression genes [sex determining region Y-box 9 (SOX9), Aggrecan (AGG), type II collagen (Coll II) and type X collagen (Coll X)] were assessed by real-time PCR. For a study on an animal model, differentiated cells in fibrin scaffolds were subcutaneously transplanted in rats. Histological and immunohistochemistry were done in the animal model. The results of the real-time PCR indicated that SOX9, AGG and Col II genes expression in TGF-β3, KGN and ASU groups were significantly higher (p < 0.01) compared to the control group, Col X gene expression only in the TGF-β3 group was significantly higher (p< 0.01) compared to the control group. The glycosaminoglycan (GAG) deposition was higher in TGF-β3, KGN and ASU groups compared to the control group. The immunohistological analysis showed the distribution of collagen type X in the extracellular matrix in the fibrin scaffold TGF-β3 group was significantly higher in control, KGN and ASU groups, and (p < 0.001). ASU, particularly KGN, was suitable for successful chondrogenic differentiation of hADSCs and a suppressor of the consequent hypertrophy.

Evaluating the effect of a post-processing algorithm in detection of annular fissure on MR imaging

BACKGROUND AND PURPOSE

Visualization of annular fissures on MRI is becoming increasingly important but remains challenging. Our purpose was to test whether an image processing algorithm could improve detection of annular fissures.

MATERIALS AND METHODS

In this retrospective study, two neuroradiologists identified 56 IVDs with annular fissures and 97 IVDs with normal annulus fibrosus in lumbar spine MRIs of 101 patients (58 M, 43 F; age ± SD 15.1 ± 3.0 years). Signal intensities of diseased and normal annulus fibrosus, and contrast-to-noise ratio between them on sagittal T2-weighted images were calculated before and after processing with a proprietary software. Effect of processing on detection of annular fissures by two masked neuroradiologists was also studied for IVDs with Pfirrmann grades of ≤ 2 and > 2.

RESULTS

Mean (SD) signal baseline intensities of diseased and normal annulus fibrosus were 57.6 (23.3) and 24.4 (7.8), respectively (p < 0.001). Processing increased (p < 0.001) the mean (SD) intensity of diseased annulus to 110.6 (47.9), without affecting the signal intensity of normal annulus (p = 0.14). Mean (SD) CNR between the diseased and normal annulus increased (p < 0.001) from 11.8 (14.1) to 29.6 (29.1). Both masked readers detected more annular fissures after processing in IVDs with Pfirrmann grade of ≤ 2 and > 2, with an apparent increased sensitivity and decreased specificity using predefined image-based human categorization as a reference standard.

CONCLUSIONS

Image processing improved CNR of annular fissures and detection rate of annular fissures. However, further studies with a more stringent reference standard are needed to assess its effect on sensitivity and specificity.

Characterization of biomaterials intended for use in the nucleus pulposus of degenerated intervertebral discs

Biomaterials for regeneration of the intervertebral disc must meet complex requirements conforming to biological, mechanical and clinical demands. Currently no consensus on their characterization exists. It is crucial to identify parameters and their method of characterization for accurate assessment of their potential efficacy, keeping in mind the translation towards clinical application. This review systematically analyses the characterization techniques of biomaterial systems that have been used for nucleus pulposus (NP) restoration and regeneration. Substantial differences in the approach towards assessment became evident, hindering comparisons between different materials with respect to their suitability for NP restoration and regeneration. We have analysed the current approaches and identified parameters necessary for adequate biomaterial characterization, with the clinical goal of functional restoration and biological regeneration of the NP in mind. Further, we provide guidelines and goals for their measurement. STATEMENT OF SIGNIFICANCE: Biomaterials intended for restoration of regeneration of the nucleus pulposus within the intervertebral disc must meet biological, biomechanical and clinical demands. Many materials have been investigated, but a lack of consensus on which parameters to evaluate leads to difficulties in comparing materials as well as mostly partial characterization of the materials in question. A gap between current methodology and clinically relevant and meaningful characterization is prevalent. In this article, we identify necessary methods and their implementation for complete biomaterial characterization in the context of clinical applicability. This will allow for a more unified approach to NP-biomaterials research within the field as a whole and enable comparative analysis of novel materials yet to be developed.

Advanced Strategies for the Regeneration of Lumbar Disc Annulus Fibrosus

Damage to the annulus fibrosus (AF), the outer region of the intervertebral disc (IVD), results in an undesirable condition that may accelerate IVD degeneration causing low back pain. Despite intense research interest, attempts to regenerate the IVD have failed so far and no effective strategy has translated into a successful clinical outcome. Of particular significance, the failure of strategies to repair the AF has been a major drawback in the regeneration of IVD and nucleus replacement. It is unlikely to secure regenerative mediators (cells, genes, and biomolecules) and artificial nucleus materials after injection with an unsealed AF, as IVD is exposed to significant load and large deformation during daily activities. The AF defects strongly change the mechanical properties of the IVD and activate catabolic routes that are responsible for accelerating IVD degeneration. Therefore, there is a strong need to develop effective therapeutic strategies to prevent or reconstruct AF damage to support operational IVD regenerative strategies and nucleus replacement. By the way of this review, repair and regenerative strategies for AF reconstruction, their current status, challenges ahead, and future outlooks were discussed.

[Preparation and characterization of oriented scaffolds derived from cartilage extracellular matrix and silk fibroin]

OBJECTIVE

This study aims to prepare oriented scaffolds derived from a cartilage extracellular matrix (CECM) and silk fibroin (SF) and use to investigate their physicochemical property in cartilage tissue engineering.

METHODS

Oriented SF-CECM scaffolds were prepared from 6% mixed slurry (CECM：SF=1：1) through modified temperature gradient-guided thermal-induced phase separation, followed by freeze drying. The SF-CECM scaffolds were evaluated by scanning electron microscopy (SEM) and histological staining analyses and determination of porosity, water absorption, and compressive elastic modulus of the materials.

RESULTS

The SEM image showed that the SF-CECM scaffolds contained homogeneous reticular porous structures in the cross-section and vertical tubular structures in the longitudinal sections. Histological staining showed that cells were completely removed, and the hybrid scaffolds retained proteogly can and collagen. The composition of the scaffold was similar to that of natural cartilage. The porosity, water absorption rate, and vertical compressive elastic modulus of the scaffolds were 95.733%±1.010%, 94.309%±1.302%, and (65.40±4.09) kPa, respectively.

CONCLUSIONS

The fabricated SF-CECM scaffolds exhibit satisfactory physicochemical and biomechanical properties and thus could be an ideal scaffold in cartilage tissue engineering.

Incorporation of Collagen and Hyaluronic Acid to Enhance the Bioactivity of Fibrin-Based Hydrogels for Nucleus Pulposus Regeneration

Hydrogels, such as fibrin, offer a promising delivery vehicle to introduce cells into the intervertebral disc (IVD) to regenerate damaged disc tissue as a potential treatment for low back pain. However, fibrin lacks key extracellular matrix (ECM) components, such as collagen (Col) and hyaluronan (HA), normally found in native nucleus pulposus (NP) tissue. The overall aim of this work was to create a fibrin-based hydrogel, by incorporating Col and HA into the matrix to enhance NP-like matrix accumulation using articular chondrocytes (CC). Firstly, we assessed the effect of fibrin concentrations on hydrogel stability, and the viability and proliferation kinetics of articular chondrocytes. Secondly, we investigated the effect of incorporating Col and HA to enhance NP-like matrix accumulation, and finally, examined the influence of various HA concentrations. Results showed that increasing fibrin concentration enhanced cell viability and proliferation. Interestingly, incorporation of HA promoted sGAG accumulation and tended to suppress collagen formation at higher concentrations. Taken together, these results suggest that incorporation of ECM components can enhance the bioactivity of fibrin-based hydrogels, which may help advance the clinical potential of commercial cell and biomaterial ventures in the treatment of IVD regeneration.

Regenerative Treatments for Spinal Conditions

A literature review of clinical and translational studies was performed to provide an overview of current concepts on regenerative treatments for spinal conditions, including platelet rich plasma and stem cell treatments to treat low back pain.

Structural and Chemical Modification to Improve Adhesive and Material Properties of Fibrin-Genipin for Repair of Annulus Fibrosus Defects in Intervertebral Disks

Annulus fibrosus (AF) defects from intervertebral disk (IVD) herniation and degeneration are commonly associated with back pain. Genipin-crosslinked fibrin hydrogel (FibGen) is an injectable, space-filling AF sealant that was optimized to match AF shear properties and partially restored IVD biomechanics. This study aimed to enhance mechanical behaviors of FibGen to more closely match AF compressive, tensile, and shear properties by adjusting genipin crosslink density and by creating a composite formulation by adding Poly(D,L-lactide-co-glycolide) (PDLGA). This study also evaluated effects of thrombin concentration and injection technique on gelation kinetics and adhesive strength. Increasing FibGen genipin concentration from 1 to 36 mg/mL significantly increased adhesive strength (∼5 to 35 kPa), shear moduli (∼10 to 110 kPa), and compressive moduli (∼25 to 150 kPa) with concentration-dependent effects, and spanning native AF properties. Adding PDLGA to FibGen altered the material microstructure on electron microscopy and nearly tripled adhesive strength, but did not increase tensile moduli, which remained nearly 5× below native AF, and had a small increase in shear moduli and significantly decreased compressive moduli. Increased thrombin concentration decreased gelation rate to < 5 min and injection methods providing a structural FibGen cap increased pushout strength by ∼40%. We conclude that FibGen is highly modifiable with tunable mechanical properties that can be formulated to be compatible with human AF compressive and shear properties and gelation kinetics and injection techniques compatible with clinical discectomy procedures. However, further innovations, perhaps with more efficient fiber reinforcement, will be required to enable FibGen to match AF tensile properties.

Biotin-avidin mediates the binding of adipose-derived stem cells to a porous β-tricalcium phosphate scaffold: Mandibular regeneration

The present study aimed to investigate the properties of a promising bone scaffold for bone repair, which consisted of a novel composite of adipose-derived stem cells (ADSCs) attached to a porous β-tricalcium phosphate (β-TCP) scaffold with platelet-rich plasma (PRP). The β-TCP powder was synthesized and its composition was determined using X-ray diffraction and Fourier transform infrared spectroscopy. The surface morphology and microstructure of the fabricated porous β-TCP scaffold samples were analyzed using light and scanning electron microscopy, and their porosity and compressive strength were also evaluated. In addition, the viability of rabbit ADSCs incubated with various concentrations of the β-TCP extraction fluid was analyzed. The rate of attachment and the morphology of biotinylated ADSCs (Bio-ADSCs) on avidin-coated β-TCP (Avi-β-TCP), and untreated ADSCs on β-TCP, were compared. Furthermore, in vivo bone-forming abilities were determined following the implantation of group 1 (Bio-ADSCs/Avi-β-TCP) and group 2 (Bio-ADSCs/Avi-β-TCP/PRP) constructs using computed tomography, and histological osteocalcin (OCN) and alkaline phosphatase (ALP) expression analyses in a rabbit model of mandibulofacial defects. The β-TCP scaffold exhibited a high porosity (71.26±0.28%), suitable pore size, and good mechanical strength (7.93±0.06 MPa). Following incubation with β-TCP for 72 h, 100% of viable ADSCs remained. The avidin-biotin binding system significantly increased the initial attachment rate of Bio-ADSCs to Avi-β-TCP in the first hour (P<0.01). Following the addition of PRP, group 2 exhibited a bony-union and mandibular body shape, newly formed bone and increased expression levels of OCN and ALP in the mandibulofacial defect area, as compared with group 1 (P<0.05). The results of the present study suggested that the novel Bio-ADSCs/Avi-β-TCP/PRP composite may have potential application in bone repair and bone tissue engineering.

Characterization of mechanics and cytocompatibility of fibrin-genipin annulus fibrosus sealant with the addition of cell adhesion molecules

There is an unmet clinical need for a biomaterial sealant capable of repairing small annulus fibrosus (AF) defects. Causes of these defects include painful intervertebral disc herniations, microdiscectomy procedures, morbidity associated with needle puncture injury from discography, and future nucleus replacement procedures. This study describes the enhancements of a fibrin gel through genipin crosslinking (FibGen) and the addition of the cell adhesion molecules (CAMs), fibronectin and collagen. The gel's performance as a potential AF sealant is assessed using a series of in vitro tests. FibGen gels with CAMs had equivalent adhesive strength, gene expression, cytomorphology, and cell proliferation as fibrin alone. However, FibGen gels had enhanced material behaviors that were tunable to higher shear stiffness values and approximated human annulus tissue as compared with fibrin alone, were more dimensionally stable, and had a slower in vitro degradation rate. Cytomorphology of human AF cells cultured on FibGen gels exhibited increased elongation compared with fibrin alone, and the addition of CAMs to FibGen did not significantly affect elongation. This FibGen gel offers the promise of being used as a sealant material to repair small AF defects or to be used in combination with other biomaterials as an adhesive for larger defects.

Fibrin Sealant: The Only Approved Hemostat, Sealant, and Adhesive-a Laboratory and Clinical Perspective

Background. Fibrin sealant became the first modern era material approved as a hemostat in the United States in 1998. It is the only agent presently approved as a hemostat, sealant, and adhesive by the Food and Drug Administration (FDA). The product is now supplied as patches in addition to the original liquid formulations. Both laboratory and clinical uses of fibrin sealant continue to grow. The new literature on this material also continues to proliferate rapidly (approximately 200 papers/year). Methods. An overview of current fibrin sealant products and their approved uses and a comprehensive PubMed based review of the recent literature (February 2012, through March 2013) on the laboratory and clinical use of fibrin sealant are provided. Product information is organized into sections based on a classification system for commercially available materials. Publications are presented in sections based on both laboratory research and clinical topics are listed in order of decreasing frequency. Results. Fibrin sealant remains useful hemostat, sealant, and adhesive. New formulations and applications continue to be developed. Conclusions. This agent remains clinically important with the recent introduction of new commercially available products. Fibrin sealant has multiple new uses that should result in further improvements in patient care.

Inflammatory mediators in intervertebral disk degeneration and discogenic pain

Although degeneration of the intervertebral disk has historically been described as a misbalance between anabolic and catabolic factors, the role of inflammatory mediators has long been neglected. However, past research clearly indicates that inflammatory mediators such as interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor-α are expressed at higher levels in "diseased" intervertebral disks. Both disk cells as well as invading macrophages can be the source of the detected cytokines. Importantly, occurrence of inflammatory mediators in the disk can worsen the progress of degeneration by inducing the expression of matrix degrading enzymes as well as by inhibiting extracellular matrix synthesis. In addition, inflammatory mediators play a crucial role in pain development during intervertebral disk herniation (i.e., sciatica) and disk degeneration (i.e., discogenic pain). This review provides information on the most relevant inflammatory mediators during different types of disk diseases and explains how these factors can induce disk degeneration and the development of discogenic and sciatic/radiculopathic pain.