Long-term Radiological and Clinical Outcomes After Using Bone Marrow Mesenchymal Stem Cells Concentrate Obtained With Selective Retention Cell Technology in Posterolateral Spinal Fusion

A Di-aptamer-functionalized scaffold promotes bone regeneration by facilitating the selective retention of MSCs and EPCs and then promoting crosstalk between osteogenesis and angiogenesis

The crosstalk between osteogenesis and angiogenesis plays an important role in promoting the formation of a microenvironment that supports bone regeneration. This suggests that the retention of endogenous osteogenic and angiogenic cells in the bone defect area can promote tissue-engineered bone (TEB) osteogenesis and cell-cell interactions. In this study, a Di-Aptamer-functionalized HA/β-TCP (Di-Aptamer-H/T) scaffold was prepared by sequential modification of APTES and sulfo-SMCC and connected with aptamer HM69 and EPC1. We confirmed that aptamers HM69 and EPC1 can specifically identify mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs), respectively. This process triggers the expression of adhesion-related genes in these cells and allows these cells to selectively stay coupled to Di-Aptamer-H/T. The osteogenic differentiation ability of MSCs treated with Di-Aptamer-H/T in vitro was significantly increased. Similarly, the ability of Di-Aptamer-H/T-treated EPCs to form blood vessels was also enhanced. Notably, the osteogenic and angiogenic abilities of cocultured MSCs and EPCs treated with the Di-Aptamer-H/T scaffold were significantly better than those of cells cultured individually. In vivo, the results of micro-CT angiography, H&E staining, Masson's staining and histochemical staining further confirmed that Di-Aptamer-H/T formed new bones and vessels more readily than those treated with a single aptamer linked to HA/β-TCP or with HA/β-TCP alone. In brief, our study demonstrated that crosstalk between osteogenesis and angiogenesis is promoted by the Di-Aptamer-H/T scaffold, which serves as a potential treatment strategy for bone defects and can improve outcomes.

Bone Graft Options in Spinal Fusion: A Review of Current Options and the Use of Mesenchymal Cellular Bone Matrices

BACKGROUND

Spinal fusion is the mainstay treatment for various spinal conditions ranging from lumbar and cervical stenosis to degenerative spondylolisthesis as well as extensive deformity corrections. A new emerging category of allograft is cellular bone matrices (CBMs), which take allogeneic mesenchymal stem cells and incorporate them into an osteoconductive and osteoinductive matrix. This study reviewed the current spinal fusion options and new emerging treatment options.

METHODS

Articles were searched using PubMed. The search included English publications since January 1, 2014, using the search terms "cellular bone matrix," "mesenchymal stem cells spinal fusion," "spinal arthrodesis AND mesenchymal stem cells," and "spine fusion AND cellular bone matrix."

RESULTS

Spinal fusion is accomplished through the use of allografts, autografts, and bone graft substitutes in combination or alone. An emerging category of allograft is CBMs, in which an osteoconductive and osteoinductive matrix is filled with mesenchymal stem cells. Studies demonstrate that CBMs have achieved equivalent or better fusion rates compared with traditional options for anterior cervical discectomy and fusions and posterolateral lumbar fusions; however, the studies have been retrospective and lacking control groups and therefore not ideal.

CONCLUSIONS

Many treatment options have been successfully used in spinal fusion. Newer allografts such as CBMs have shown promising results in both animal and clinical studies. Further research is needed to determine the therapeutic dose of mesenchymal stem cells delivered within CBMs.

Selective Retention of Bone Marrow Stromal Cells with Gelatin Sponge for Repair of Intervertebral Disc Defects after Microendoscopic Discectomy: A Prospective Controlled Study and 2-Year Follow-Up

Objective

Discectomy remains the classic procedure for treating lumbar intervertebral disc (IVD) herniation, but the occurrence of defects after discectomy is thought to be an important cause generating recurrent and accelerated IVD degeneration. Previous studies attempted suture of the annulus fissure, but the validity of this technique on restraining the degenerative process is controversial. On the other hand, cell therapies have been shown in multiple clinical and basic studies. Our purpose was to investigate the effectiveness of selective retention of autologous Bone Marrow Stromal Cells (BMSCs) with gelatin sponge in combination with annulus fibrosus suture (AFS) for the repair of IVD defects following mobile microendoscopic discectomy (MMED).

Methods

This prospective, two-armed, and controlled clinical study was conducted from December 2016 to December 2018. Written informed consent was obtained from each patient. Forty-five patients with typical symptoms, positive signs of radiculopathy, and obvious lumbar disc herniation observed by MRI were enrolled. Patients were divided into 3 groups with different treating methods: MMED (n = 15), MMED+AFS (n = 15), and MMED+AFS+BMSCs (n = 15). A postoperative 2-year follow-up was performed to evaluate the patient-reported outcomes of VAS, ODI, and SF-36. The improvement rate of VAS and ODI was calculated as [(latest‐preoperative)/preoperative] to evaluate the therapeutic effect of the three groups. Assessment parameters included Pfirrmann grade, intervertebral disc height (IDH), and disc protrusion size (DPS), as measured by MRI to evaluate the morphological changes.

Results

All patients enrolled had a postoperative follow-up at 3, 6, 12, and 24 months. VAS and ODI scores were significantly improved compared to the preoperative status in all three groups with a mean DPS reduction rate over 50%. At the final follow-up, the improvement rate of the VAS score in the MMED+AFS+BMSCs group was significantly higher than the MMED+AFS and MMED groups (80.1% ± 7.6% vs. 71.3% ± 7.0% vs. 70.1% ± 7.8%), while ODI improvement showed a significant change (65.6% ± 8.8% vs. 59.9% ± 5.5% vs. 57.8% ± 8.1%). All participants showed significant improvement in SF-36 PCS and MCS; the differences between each group were not significant. The mean IDH loss rate of the MMED+AFS+BMSCs group was also significantly lower than other groups (−17.2% ± 1.3% vs. −27.6% ± 0.7% vs. −29.3% ± 2.2%). The Pfirrmann grade was aggravated in the MMED and MMED+AFS groups while maintained at the preoperative grade in the MMED+AFS+BMSCs group. No adverse events of cell transplantation or recurrence were found in all patients during the postoperative follow-up period.

Conclusions

It is feasible and effective to repair lumbar IVD defects using SCR-enriched BMSCs with gelatin sponges, which warrants further study and development as a cell-based therapy for IVD repair.

Osteobiologics

BACKGROUND

Osteobiologics are engineered materials that facilitate bone healing and have been increasingly used in spine surgery. Autologous iliac crest bone grafts have been used historically, but morbidity associated with graft harvesting has led surgeons to seek alternative solutions. Allograft bone, biomaterial scaffolds, growth factors, and stem cells have been explored as bone graft substitutes and supplements.

OBJECTIVE

To review current and emerging osteobiologic technologies.

METHODS

A literature review of English-language studies was performed in PubMed. Search terms included combinations of "spine," "fusion," "osteobiologics," "autologous," "allogen(e)ic," "graft," "scaffold," "bone morphogenic protein," and "stem cells."

RESULTS

Evidence supports allograft bone as an autologous bone supplement or replacement in scenarios where minimal autologous bone is available. There are promising data on ceramics and P-15; however, comparative human trials remain scarce. Growth factors, including recombinant human bone morphogenic proteins (rhBMPs) 2 and 7, have been explored in humans after successful animal trials. Evidence continues to support the use of rhBMP-2 in lumbar fusion in patient populations with poor bone quality or revision surgery, while there is limited evidence for rhBMP-7. Stem cells have been incredibly promising in promoting fusion in animal models, but human trials to this point have only involved products with questionable stem cell content, thereby limiting possible conclusions.

CONCLUSION

Engineered stem cells that overexpress osteoinductive factors are likely the future of spine fusion, but issues with applying viral vector-transduced stem cells in humans have limited progress.

Comparison of Individual Tissue-Engineered Bones and Allogeneic Bone in Treating Bone Defects: A Long-Term Follow-Up Study

The treatment of bone defects has always been a challenge for orthopedic surgeons. The development of tissue engineering technology provides a novel method for repairing bone defects and has been used in animal experiments and clinical trials. However, there are few clinical studies on comparing the long-term outcomes of tissue-engineered bones (TEBs) and other bone grafts in treating bone defects, and the long-term efficiency of TEBs remains controversial. Therefore, a study designed by us was aimed to compare the long-term efficacy and safety of individual tissue-engineered bones (iTEBs) and allogeneic bone granules (ABGs) in treating bone defects caused by curettage of benign bone tumors and tumor-like lesions. From September 2003 to November 2009, 48 patients who received tumor curettage and bone grafting were analyzed with a mean follow-up of 122 mo (range 60 to 173 mo). Based on implant style, patients were divided into groups of iTEBs (n = 23) and ABGs (n = 25). Postoperatively, the healing time, healing quality, incidence of complications, and functional scores were compared between the two groups. The Musculoskeletal Tumor Society functional evaluation system and Activities of Daily Living Scale scores were significantly improved in both groups with no significant difference. The average healing time of ABGs was longer than that of iTEBs (P < 0.05). At the final follow-up, iTEBs had a better performance in the bone healing quality evaluated by modified Neer classification (P < 0.05). In the group of iTEBs, the complication and reoperation rate was lower than that in the group of ABGs, with no tumorigenesis or immune rejection observed. In summary, for treating bone defects caused by tumor curettage, iTEBs were safe, effective, and tagged with more rapid healing speed, better healing outcome, and lower complication and reoperation rate, in comparison with ABGs.

Laminin alpha 4 promotes bone regeneration by facilitating cell adhesion and vascularization

Selective cell retention (SCR) has been widely used as a bone tissue engineering technique for the real-time fabrication of bone grafts. The greater the number of mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) retained in the scaffold, the better the osteoinductive and angiogenic properties of the scaffold's microenvironment. Improved bioscaffold properties in turn lead to improved bone graft survival, bone regeneration, and angiogenesis. Laminin plays a key role in cell-matrix adhesion, cell proliferation, and differentiation. We designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 (CBD-LN peptide) to supplement the functional surface of a collagen-based decalcified bone matrix (DBM) scaffold. This scaffold promoted MSCs and EPCs early cell adhesion through up-regulating the expression of integrin α5β1 and integrin αvβ3 respectively, thus accelerated the following cell spreading, proliferation, and differentiation. Interestingly, it promoted the retention of MSCs (CD90⁺/CD105⁺ cells) and EPCs (CD31⁺ cells) in the scaffold following the use of clinical SCR technology. Furthermore, the DBM/CBD-LN scaffold induced the formation of type H vessels through the activation of the HIF-1α signaling pathway. The DBM/CBD-LN scaffold displayed rapid bone formation and angiogenesis in vivo, suggesting that it might be used as a new biomaterial in bone tissue engineering. STATEMENT OF SIGNIFICANCE: Selective cell retention technology (SCR) has been utilized in clinical settings to manufacture bioactive bone grafts. Specifically, demineralized bone matrix (DBM) is a widely-used SCR clinical biomaterial but it displays poor adhesion performance and angiogenic activity. In this work, we designed a collagen-binding domain (CBD) containing the core functional amino acid sequences of laminin α4 to supplement the functional surface of a collagen-based DBM scaffold. This bioscaffold promoted SCR-mediated MSCs and EPCs early cell adhesion, thus accelerated the following cell spreading, proliferation, and differentiation. Our results indicate this bioscaffold greatly induced osteogenesis and angiogenesis in vivo. In general, this bioscaffold has a good prospect for SCR application and may provide highly bioactive bone implant in clinical environment.

Understanding the Future Prospects of Synergizing Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery with Ceramics and Regenerative Cellular Therapies

Transforaminal lumber interbody fusion (TLIF) is the last resort to address the lumber degenerative disorders such as spondylolisthesis, causing lower back pain. The current surgical intervention for these abnormalities includes open TLIF. However, in recent years, minimally invasive TLIF (MIS-TLIF) has gained a high momentum, as it could minimize the risk of infection, blood loss, and post-operative complications pertaining to fusion surgery. Further advancement in visualizing and guiding techniques along with grafting cage and materials are continuously improving the safety and efficacy of MIS-TLIF. These assistive techniques are also playing a crucial role to increase and improve the learning curve of surgeons. However, achieving an appropriate output through TLIF still remains a challenge, which might be synergized through 3D-printing and tissue engineering-based regenerative therapy. Owing to their differentiation potential, biomaterials such as stem/progenitor cells may contribute to restructuring lost or damaged tissues during MIS-TLIF, and this therapeutic efficacy could be further supplemented by platelet-derived biomaterials, leading to improved clinical outcomes. Thus, based on the above-mentioned strategies, we have comprehensively summarized recent developments in MIS-TLIF and its possible combinatorial regenerative therapies for rapid and long-term relief.

Radiological and clinical outcomes using induced membrane technique combined with bone marrow concentrate in the treatment of chronic osteomyelitis of immature patients

Aims

Treatment of chronic osteomyelitis (COM) for young patients remains a challenge. Large bone deficiencies secondary to COM can be treated using induced membrane technique (IMT). However, it is unclear which type of bone graft is optimal. The goal of the study was to determine the clinical effectiveness of bone marrow concentrator modified allograft (BMCA) versus bone marrow aspirate mixed allograft (BMAA) for children with COM of long bones.

Methods

Between January 2013 and December 2017, 26 young patients with COM were enrolled. Different bone grafts were applied to repair bone defects secondary to IMT procedure for infection eradication. Group BMCA was administered BMCA while Group BMAA was given BMAA. The results of this case-control study were retrospectively analyzed.

Results

Patient infection in both groups was eradicated after IMT surgery. As for reconstruction surgery, no substantial changes in the operative period (p = 0.852), intraoperative blood loss (p = 0.573), or length of hospital stay (p = 0.362) were found between the two groups. All patients were monitored for 12 to 60 months. The median time to bone healing was 4.0 months (interquartile range (IQR) 3.0 to 5.0; range 3 to 7) and 5.0 months (IQR 4.0 to 7.0; range 3 to 10) in Groups BMCA and BMAA, respectively. The time to heal in Group BMCA versus Group BMAA was substantially lower (p = 0.024).

Conclusion

IMT with BMCA or BMAA may attain healing in large bone defects secondary to COM in children. The bone healing time was significantly shorter for BMCA, indicating that this could be considered as a new strategy for bone defect after COM treatment.

Cite this article: Bone Joint Res 2021;10(1):31–40.

Inhibition of protein-tyrosine phosphatase 1B phosphorylation enhances early adhesion of mesenchymal stem cells to facilitate fabrication of tissue-engineered bone

Enhancement of cell-matrix adhesion is preferable and crucial in various fields of tissue engineering. Integrins are important receptors that facilitate cell-matrix adhesion, mediated by intracellular molecules and crosstalk with the cadherin adhesion pathway, which mainly facilitates cell-cell adhesion. Protein-tyrosine phosphatase 1B (PTP1B) has emerged as a pivot in the crosstalk between the cadherin adhesion pathway and the integrin adhesion pathway. The phosphorylation state of PTP1B tyrosine-152 (Y152) plays a central role in balancing the two different cell adhesion forms. In this study, a PTP1B Y152 region mimicking (152RM) peptide was designed to decrease the phosphorylation of PTP1B Y152 via competitive inhibition. As a result, the dissociation of cadherin complexes and the release of PTP1B from cadherin had sharply increased, and Src, an important intracellular component of integrin, was activated, indicating that the cadherin adhesion pathway was inhibited, whereas the integrin adhesion pathway was enhanced. Moreover, upon treatment with the 152RM peptide, we observed that the early adhesion of human bone marrow-derived mesenchymal stem cells (MSCs) was accelerated and the anchoring of MSCs on the surface of integrin ligands was enhanced by an enhanced matrix adhesion ability of MSCs themselves. Importantly, the 152RM peptide significantly promoted the adhesion efficiency of MSCs in the selective cell retention technology, which fabricates instant bone implants in clinical settings, to stimulate osteogenesis in vivo.

Autologous mesenchymal stromal cells embedded in tricalcium phosphate for posterolateral spinal fusion: results of a prospective phase I/II clinical trial with long-term follow-up

BACKGROUND

Posterolateral spinal fusion with autologous bone graft is considered the "gold standard" for lumbar degenerative disc disease (DDD) when surgical treatment is indicated. The potential role of mesenchymal stromal cells (MSCs) to replace the bone graft in this setting has not been fully addressed.

OBJECTIVE

To analyze the safety, feasibility and potential clinical efficacy of the implantation of autologous MSCs embedded with tricalcium phosphate as a therapeutic alternative to bone graft in patients with DDD during posterolateral spine fusion.

STUDY DESIGN

Phase I/II single-arm prospective clinical trial.

METHODS

Eleven patients with monosegmental DDD at L4-L5 or L5-S1 level were included. Autologous bone marrow-derived MSC were expanded in our Good Manufacturing Practice (GMP) Facility and implanted during spinal surgery embedded in a tricalcium phosphate carrier. Monitoring of patients included a postoperative period of 12 months with four visits (after the 1st, 3rd, 6th, and 12th month), with clinical and radiological assessment that included the visual analog scale (VAS), the Oswestry disability index (ODI), the Short-Form Health Survey (SF-36), the vertebral fusion grade observed through a simple Rx, and the evaluation of possible complications or adverse reactions. In addition, all patients were further followed up to 5 years for outcome.

RESULTS

Median age of patients included was 44 years (range 30-58 years), and male/female ratio was (6/5) L4-L5 and L5-S1 DDD was present five and six patients, respectively. Autologous MSCs were expanded in all cases. There were no adverse effects related to cell implantation. Regarding efficacy, both VAS and ODI scores improved after surgery. Radiologically, 80% of patients achieved lumbar fusion at the end of the follow-up. No adverse effects related to the procedure were recorded.

CONCLUSIONS

The use of autologous MSCs for spine fusion in patients with monosegmental degenerative disc disease is feasible, safe, and potentially effective.

TRIAL REGISTRATION

no. EudraCT: 2010-018335-17 ; code Identifier: NCT01513694 ( clinicaltrials.gov ).

Multiple integrin ligands provide a highly adhesive and osteoinductive surface that improves selective cell retention technology

Among various bone tissue engineering strategies, selective cell retention (SCR) technology has been used as a practical clinical method for bone graft manufacturing in real time. The more mesenchymal stem cells (MSCs) are retained, the better the osteoinductive microenvironment provided by the scaffold, which in turn promotes the osteogenesis of the SCR-fabricated bone grafts. Integrin receptors are crucial to cell-matrix adhesion and signal transduction. We designed a collagen-binding domain (CBD)-containing IKVAV-cRGD peptide (CBD-IKVAV-cRGD peptide) to complement the collagen-based demineralized bone matrix (DBM) with a functionalized surface containing multiple integrin ligands, which correspond to the highly expressed integrin subtypes on MSCs. This DBM/CBD-IKVAV-cRGD composite exhibited superior in vitro adhesion capacity to cultured MSCs, as determined by oscillatory cell adhesion assay, centrifugal cell adhesion assay and mimetic SCR. Moreover, it promoted the retention of MSC-like CD271⁺ cells and MSC-like CD90⁺/CD105⁺ cells in the clinical SCR method. Furthermore, the DBM/CBD-IKVAV-cRGD composite induced robust MSC osteogenesis, coupled with the activation of the downstream FAK-ERK1/2 signaling pathway of integrins. The SCR-prepared DBM/CBD-IKVAV-cRGD composite displayed superior in vivo osteogenesis, indicating that it may be potentially utilized as a biomaterial in SCR-mediated bone transplantation. STATEMENT OF SIGNIFICANCE: Selective cell retention technology (SCR) has been utilized in clinical settings to manufacture bioactive bone grafts. Specifically, demineralized bone matrix (DBM) is a widely-used SCR clinical biomaterial but it displays poor adhesion performance and osteoinduction. Improvements of the DBM that promote cell adhesion and osteoinduction will benefit SCR-prepared implants. In this work, we developed a novel peptide that complements the DBM with a functionalized surface of multiple integrin ligands, which are corresponding to integrin subtypes available on human bone marrow-derived mesenchymal stem cells (MSCs). Our results indicate this novel functionalized bioscaffold greatly increases SCR-mediated MSC adhesion and in vivo osteogenesis. Overall, this novel material has promising SCR applications and may likely provide highly bioactive bone implants in clinical settings.

ISASS Recommendations and Coverage Criteria for Bone Graft Substitutes used in Spinal Surgery

Autologous bone graft remains the gold standard by which bone graft substitutes are compared in spine fusion surgery. The utilization of bone graft substitutes, either as (1) an extender for spinal fusion constructs or (2) an alternative to minimize morbidity while maximizing outcomes, is changing. Moreover, current procedures technology (CPT) code 20939 became effective in 2018 defining bone marrow aspirate for bone grafting, spine surgery only. Changes in the complex landscape of grafting materials have prompted ISASS to provide category guidance for bone graft substitutes by comparing and contrasting US regulatory pathways, mechanisms of action, and supportive clinical evidence for these bone grafting materials.

The Biological Enhancement of Spinal Fusion for Spinal Degenerative Disease

In this era of aging societies, the number of elderly individuals who undergo spinal arthrodesis for various degenerative diseases is increasing. Poor bone quality and osteogenic ability in older patients, due to osteoporosis, often interfere with achieving bone fusion after spinal arthrodesis. Enhancement of bone fusion requires shifting bone homeostasis toward increased bone formation and reduced resorption. Several biological enhancement strategies of bone formation have been conducted in animal models of spinal arthrodesis and human clinical trials. Pharmacological agents for osteoporosis have also been shown to be effective in enhancing bone fusion. Cytokines, which activate bone formation, such as bone morphogenetic proteins, have already been clinically used to enhance bone fusion for spinal arthrodesis. Recently, stem cells have attracted considerable attention as a cell source of osteoblasts, promising effects in enhancing bone fusion. Drug delivery systems will also need to be further developed to assure the safe delivery of bone-enhancing agents to the site of spinal arthrodesis. Our aim in this review is to appraise the current state of knowledge and evidence regarding bone enhancement strategies for spinal fusion for degenerative spinal disorders, and to identify future directions for biological bone enhancement strategies, including pharmacological, cell and gene therapy approaches.