The future of disc surgery and regeneration

Prevalence of lumbar disc herniation in populations with different symptoms based on magnetic resonance imaging study

BACKGROUND

Lumbar disc herniation (LDH) is common in aged human beings. This study is to investigate the prevalence of lumbar disc herniation (LDH) in different symptomatic populations attending outpatient clinics based on magnetic resonance imaging (MRI) studies, and to analyze the characteristics, distribution, and treatment strategies thereof.

METHODS

Patients who visited our outpatient clinics between January 1, 2022, and December 31, 2022, with complaints of low back pain, either accompanied or unaccompanied by lower limb symptoms (radiating pain, numbness or muscle weakness), were included. All patients underwent comprehensive lumbar spine MRI examinations. The prevalence of LDH in different symptomatic populations, as well as the characteristics, distribution, and treatment strategies of disc herniation were analyzed.

RESULTS

Among 8,161 individuals (3,411 males and 4,750 females), 4,496 were diagnosed with LDH, resulting in a prevalence of 55.1 %. Of these, 683 (15.2 %) individuals underwent surgical treatment. Among all patients, 3,529 exhibited only low back pain symptoms, 1,820 (51.6 %) were diagnosed with LDH, and 201 (11.0 %) received surgical treatment. Additionally, 2,673 patients with low back pain accompanied by lower limb symptoms were identified, with 1,608 individuals (82.1 %) diagnosed with LDH; 319 (19.8 %) underwent surgical treatment. Furthermore, 1,959 patients presented with lower limb symptoms only, 1,068 (54.5 %) were diagnosed with LDH, and 163 received surgical treatment (P < 0.001). The prevalence rate for males was 58.8 %, compared to females with 52.4 % (P < 0.01). The prevalence of LDH exhibited an initially increasing trend, later decreasing with advancing age. L4/5 and L5/S1 were the most commonly affected segments.

CONCLUSION

LDH prevalence varies among patients with different symptoms, with a higher rate in those presenting with low back pain accompanied by lower limb symptoms. These symptomatic patients also exhibit a higher rate of surgical intervention.

Reviving Intervertebral Discs: Treating Degeneration Using Advanced Delivery Systems

Intervertebral disc degeneration (IVDD) is commonly associated with many spinal problems, such as low back pain, and significantly impacts a patient's quality of life. However, current treatments for IVDD, which include conservative and surgical methods, are limited in their ability to fully address degeneration. To combat IVDD, delivery-system-based therapy has received extensive attention from researchers. These delivery systems can effectively deliver therapeutic agents for IVDD, overcoming the limitations of these agents, reducing leakage and increasing local concentration to inhibit IVDD or promote intervertebral disc (IVD) regeneration. This review first briefly introduces the structure and function of the IVD, and the related pathophysiology of IVDD. Subsequently, the roles of drug-based and bioactive-substance-based delivery systems in IVDD are highlighted. The former includes natural source drugs, nonsteroidal anti-inflammatory drugs, steroid medications, and other small molecular drugs. The latter includes chemokines, growth factors, interleukin, and platelet-rich plasma. Additionally, gene-based and cell-based delivery systems are briefly involved. Finally, the limitations and future development of the combination of therapeutic agents and delivery systems in the treatment of IVDD are discussed, providing insights for future research.

Comparative study of outcomes between allograft intervertebral disc transplantation and anterior cervical discectomy and fusion: a retrospective cohort study at least 5 years of follow-up

PURPOSE

Adjacent segment degeneration (ASDeg) after anterior cervical discectomy and fusion (ACDF) seriously affects the long-term efficacy of the operation. Therefore, our team has done a lot of research on allograft intervertebral disc transplantation (AIDT) to prove its feasibility and safety. This study will compare the efficacy between AIDT and ACDF in the treatment of cervical spondylosis.

METHODS

All patients who received ACDF or AIDT in our hospital from 2000 to 2016 and followed up for at least 5 years were recruited and divided into ACDF and AIDT groups. The clinical outcomes including functional scores and radiological data of both groups were collected and compared preoperatively and postoperatively at 1 week, 3 months, 6 months, 12 months, 24 months, 60 months and last follow-up. Functional scores included Japanese Orthopedic Association score (JOA), Neck Disability Index (NDI), Visual Analog Scale of Neck (N-VAS) and Arms (A-VAS) pain, the Short Form Health Survey-36 (SF-36) and imaging dates including digital radiographs in the lateral, hyperextension and flexion positions to assess the stability, sagittal balance and mobility of the cervical spine and magnetic resonance imaging (MRI) scans to assess the degeneration of adjacent segment.

RESULTS

There were 68 patients with 25 in AIDT group and 43 in ACDF group. Satisfactory clinical results were obtained in both groups, but the long-term NDI score and N-VAS score in the AIDT group were better. The AIDT obtained the same stability and sagittal balance of the cervical spine as fusion surgery. The range of motion of adjacent segments can be restored to the preoperative level after transplantation, but this increases significantly after ACDF. There were significant differences in the superior adjacent segment range of motion (SROM) between two groups at 12 months (P = 0.039), 24 months (P = 0.035), 60 months (P = 0.039) and the last follow-up (P = 0.011). The inferior adjacent segment range of motion (IROM) and SROM had a similar trend in the two groups. The ratio value of the greyscale (RVG) of adjacent segments showed a downward trend. At the last follow-up, the RVG decreased more significantly in the ACDF group. At the last follow-up, there was a significant difference in the incidence of ASDeg between the two groups (P = 0.000). And the incidence of adjacent segment disease (ASDis) is 22.86% in the ACDF group.

CONCLUSION

The allograft intervertebral disc transplantation may be as an alternative technique to traditional anterior cervical discectomy and fusion for the management of cervical degenerative diseases. For the more, the results showed it would improve cervical kinematics and reduce the incidence of adjacent segment degeneration.

Vanillin-based functionalization strategy to construct multifunctional microspheres for treating inflammation and regenerating intervertebral disc

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain. Although local delivery strategies using biomaterial carriers have shown potential for IVDD treatment, it remains challenging for intervention against multiple adverse contributors by a single delivery platform. In the present work, we propose a new functionalization strategy using vanillin, a natural molecule with anti-inflammatory and antioxidant properties, to develop multifunctional gelatin methacrylate (GelMA) microspheres for local delivery of transforming growth factor β3 (TGFβ3) toward IVDD treatment. In vitro, functionalized microspheres not only improved the release kinetics of TGFβ3 but also effectively inhibited inflammatory responses and promoted the secretion of extracellular matrix (ECM) in lipopolysaccharide-induced nucleus pulposus (NP) cells. In vivo, functionalized platform plays roles in alleviating inflammation and oxidative stress, preserving the water content of NP and disc height, and maintaining intact structure and biomechanical functions, thereby promoting the regeneration of IVD. High-throughput sequencing suggests that inhibition of the phosphatidylinositol 3-kinase (PI3K)-Akt signaling might be associated with their therapeutic effects. In summary, the vanillin-based functionalization strategy provides a novel and simple way for packaging multiple functions into a single delivery platform and holds promise for tissue regeneration beyond the IVD.

New Hope for Treating Intervertebral Disc Degeneration: Microsphere-Based Delivery System

Intervertebral disc (IVD) degeneration (IVDD) has been considered the dominant factor in low back pain (LBP), and its etiological mechanisms are complex and not yet fully elucidated. To date, the treatment of IVDD has mainly focused on relieving clinical symptoms and cannot fundamentally solve the problem. Recently, a novel microsphere-based therapeutic strategy has held promise for IVD regeneration and has yielded encouraging results with in vitro experiments and animal models. With excellent injectability, biocompatibility, and biodegradability, this microsphere carrier allows for targeted delivery and controlled release of drugs, gene regulatory sequences, and other bioactive substances and supports cell implantation and directed differentiation, aiming to improve the disease state of IVD at the source. This review discusses the possible mechanisms of IVDD and the limitations of current therapies, focusing on the application of microsphere delivery systems in IVDD, including targeted delivery of active substances and drugs, cellular therapy, and gene therapy, and attempts to provide a new understanding for the treatment of IVDD.

Elimination of Senescent Cells by Senolytics Facilitates Bony Endplate Microvessel Formation and Mitigates Disc Degeneration in Aged Mice

Senolytics are a class of drugs that selectively eliminate senescent cells and ameliorate senescence-associated disease. Studies have demonstrated the accumulation of senescent disc cells and the production of senescence-associated secretory phenotype decrease the number of functional cells in degenerative tissue. It has been determined that clearance of senescent cell by senolytics rejuvenates various cell types in several human organs, including the largest avascular structure, intervertebral disc (IVD). The microvasculature in the marrow space of bony endplate (BEP) are the structural foundation of nutrient exchange in the IVD, but to date, the anti-senescence effects of senolytics on senescent vascular endothelial cells in the endplate subchondral vasculature remains unclear. In this study, the relationships between endothelial cellular senescence in the marrow space of the BEP and IVD degeneration were investigated using the aged mice model. Immunofluorescence staining was used to evaluate the protein expression of P16, P21, and EMCN in vascular endothelial cells. Senescence-associated β-galactosidase staining was used to investigate the senescence of vascular endothelial cells. Meanwhile, the effects of senolytics on cellular senescence of human umbilical vein endothelial cells were investigated using a cell culture model. Preliminary results showed that senolytics alleviate endothelial cellular senescence in the marrow space of BEP as evidenced by reduced senescence-associated secretory phenotype. In the aged mice model, we found decreased height of IVD accompanied by vertebral bone mass loss and obvious changes to the endplate subchondral vasculature, which may lead to the decrease in nutrition transport into IVD. These findings may provide evidence that senolytics can eliminate the senescent cells and facilitate microvascular formation in the marrow space of the BEP. Targeting senescent cellular clearance mechanism to increase nutrient supply to the avascular disc suggests a potential treatment value of senolytics for IVD degenerative diseases.

The Impact of Physical Therapy Following Cervical Spine Surgery for Degenerative Spine Disorders: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To characterize the effects of postoperative physical therapy (PT) after surgery for cervical spondylosis on patient-reported outcomes and impairments. Secondarily, to identify associated complications, adverse effects, and health care costs with postoperative PT, and to describe the content, timing, and duration of the PT.

SUMMARY OF BACKGROUND DATA

Cervical spine surgery is common; however, it is unclear if the addition of postoperative PT leads to improved patient outcomes and decreased health care costs.

MATERIALS AND METHODS

PubMed, Embase, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, and Web of Science were searched until July 2019. All peer-reviewed articles involving cervical spine surgery with postoperative PT for cervical spondylosis were considered for inclusion. Risk of bias was assessed using the Revised Cochrane risk-of-bias tool for randomized trials. Findings were described narratively, and GRADE approach was used to define the quality of evidence.

RESULTS

A total of 10,743 studies were screened. Six studies met inclusion criteria; 2 randomized controlled trials and 4 subsequent follow-up studies containing study arms that included postoperative PT after cervical spine surgery. Meta-analysis was not performed due to study heterogeneity and no study compared PT+surgery to surgery alone. PT treatment included exercise therapy, cognitive behavioral therapy, and optional vestibular rehabilitation. Included studies indicated PT appeared to have positive effects on patient outcomes, however, there were no treatment control groups and the quality of evidence was very low to low. Timing, duration, and content of PT programs varied. No studies reported complications, adverse effects, or cost-effectiveness relating to PT after surgery.

CONCLUSIONS

Current literature prevents a definitive conclusion regarding the impact of postoperative PT, given the lack of treatment control groups. PT treatment was limited to exercise therapy, cognitive behavioral therapy, and optional vestibular rehabilitation in the included studies. PT treatment varied, limiting consistent recommendations for content, timing, and treatment duration. Controlled trials are needed to determine the effectiveness of the addition of postoperative PT following cervical spine surgery for cervical spondylosis.

LEVEL OF EVIDENCE

Level II.

Anterior Versus Posterior Decompression for Degenerative Thoracic Spine Diseases: A Comparison of Complications

STUDY DESIGN

Retrospective database.

OBJECTIVES

Although posterior decompression is the most common approach for surgical treatment of degenerative thoracic spine disease, anterior approach is gaining interest due to its advantage in disc visualization. The objective of this study was to compare the intra- and postoperative medical complication rates between anterior and posterior decompression for degenerative thoracic spine pathologies.

METHODS

A national US insurance database was queried for patients with degenerative diagnoses who had undergone anterior or posterior thoracic decompression. Incidence of intra- and postoperative complications were evaluated on the day of surgery and within 1 and 3 months. Two subgroups were matched based on age, gender, and comorbidity. The association of decompression approach and complications was assessed using logistic regression.

RESULTS

A total of 1459 patients were included, consisting of 1004 patients in posterior and 455 patients in anterior group. Respiratory complications were the most common complications on the day of surgery (8.57%) and within 30 days (17.75%). Matched analysis showed that anterior approach was associated with organ failure, gastrointestinal, and device-/implant-/graft-related complications in all follow-up periods; and with cardiovascular, deep venous thrombosis/pulmonary embolism, and respiratory complications in at least 1 follow-up period. Among respiratory complications, anterior decompression was significantly associated with noninfectious etiologies on the day of surgery (odds ratio [OR] = 1.72), within 30 days (OR = 2.05), and within 90 days (OR = 1.92).

CONCLUSIONS

Anterior approach was associated with increased rates of several complications. High rates of respiratory complications necessitate comprehensive preoperative risk stratification to identify those who may benefit more from posterior approach.

Transcriptional Profiling Uncovers Biologically Significant RNAs and Regulatory Networks in Nucleus Pulposus from Intervertebral Disc Degeneration Patients

Objective. This study aimed to uncover biologically significant RNAs in nucleus pulposus tissues of human intervertebral disc degeneration (IVDD) by integrated transcriptional profiling. Methods. From the Gene Expression Omnibus (GEO) database, three IVDD-related microarray profiling datasets were retrieved and assessed by intragroup data repeatability test. Then, differentially expressed circRNAs, lncRNAs, mRNAs, and miRNAs were screened in nucleus pulposus tissues between IVDD and control samples via the limma package. Coexpression networks were separately conducted via weighted gene correlation network analysis (WGCNA). Based on the feature RNAs in the IVDD-related modules, IVDD-related circRNA-miRNA-mRNA and lncRNA-miRNA-mRNA networks were conducted. The differentially expressed mRNAs in the two networks were analyzed by protein-protein interaction (PPI) and functional enrichment analyses. Results. By the intragroup data repeatability test, outlier samples were removed. Abnormally expressed RNAs were separately identified in nucleus pulposus between IVDD and controls. Via WGCNA, IVDD-related coexpression modules were constructed and the feature circRNAs, lncRNAs, mRNAs, and miRNAs were identified. Then, the circRNA- and lncRNA-miRNA-mRNA networks were built for IVDD. These mRNAs in the network exhibited complex interactions. Moreover, they were involved in distinct IVDD-related biological processes and pathways such as transcription, cell proliferation, TNF, TGF-β, and HIF signaling pathways. Conclusion. This study revealed biologically significant noncoding RNAs and their complex regulatory networks for IVDD.

Characterization and cytocompatibility of 3D porous biomimetic scaffold derived from rabbit nucleus pulposus tissue in vitro

Intervertebral disc (IVD) degeneration is one of the most important causes of lower back pain. Tissue engineering provides a new method for the experimental treatment of degenerative disc diseases. This study aims to develop a natural, acellular, 3D interconnected porous scaffold derived from the extracellular matrix (ECM) of nucleus pulposus. The nucleus pulposus (NP) was decellularized by sequential detergent-nuclease methods, including physical crushing, freeze-drying and cross-linking. These 3D porous scaffolds were fabricated with a high porosity of (81.28 ± 4.10)%, an ideal pore size with appropriate mechanical properties. Rabbit bone marrow mesenchymal stem cells (rBMSCs) were seeded and cultured on the scaffolds. And the mechanical tests showed the compressive elastic modulus of the scaffolds cultured for 4 weeks reached 0.12 MPa, which was better than that of the scaffolds cultured for 2 weeks (0.07 MPa) and that of the control group (0.04 MPa). Scanning electron microscopy (SEM), histological assays, molecular biology assays revealed that the scaffolds could provide an appropriate microstructure and environment for the adhesion, proliferation, migration and secretion of seeded cells in vitro. As assays like histology, immunohistochemistry and the real-time qRT-PCR showed, NP-like tissues were preliminarily formed. In conclusion, the 3D porous scaffold derived from NP ECM is a potential biomaterial for the regeneration of NP tissues. A natural, acellular, 3D interconnected porous scaffold derived from the extracellular matrix (ECM) of nucleus pulposus was developed by sequential detergent-nuclease and freeze-drying method, which can reduce the damage of protein activity to the minimum. It is very similar to the composition and internal environment of the natural nucleus pulposus, because it derived from the natural nucleus pulposus. Scanning electron microscopy (SEM), histological assays, molecular biology assays revealed that the scaffolds could provide an appropriate microstructure and environment for the adhesion, proliferation, migration, and secretion of seeded cells in vitro.

Examination of the Role of Cells in Commercially Available Cellular Allografts in Spine Fusion: An in Vivo Animal Study

BACKGROUND

Despite the extensive use of cellular bone matrices (CBMs) in spine surgery, there is little evidence to support the contribution of cells within CBMs to bone formation. The objective of this study was to determine the contribution of cells to spinal fusion by direct comparisons among viable CBMs, devitalized CBMs, and cell-free demineralized bone matrix (DBM).

METHODS

Three commercially available grafts were tested: a CBM containing particulate DBM (CBM-particulate), a CBM containing DBM fibers (CBM-fiber), and a cell-free product with DBM fibers only (DBM-fiber). CBMs were used in viable states (CBM-particulatev and CBM-fiberv) and devitalized (lyophilized) states (CBM-particulated and CBM-fiberd), resulting in 5 groups. Viable cell counts and bone morphogenetic protein-2 (BMP-2) content on enzyme-linked immunosorbent assay (ELISA) within each graft material were measured. A single-level posterolateral lumbar fusion was performed on 45 athymic rats with 3 lots of each product implanted into 9 animals per group. After 6 weeks, fusion was assessed using manual palpation, micro-computed tomography (μ-CT), and histological analysis.

RESULTS

The 2 groups with viable cells were comparable with respect to cell counts, and pairwise comparisons showed no significant differences in BMP-2 content across the 5 groups. Manual palpation demonstrated fusion rates of 9 of 9 in the DBM-fiber specimens, 9 of 9 in the CBM-fiberd specimens, 8 of 9 in the CBM-fiberv specimens, and 0 of 9 in both CBM-particulate groups. The μ-CT maturity grade was significantly higher in the DBM-fiber group (2.78 ± 0.55) compared with the other groups (p < 0.0001), while none of the CBM-particulate samples demonstrated intertransverse fusion in qualitative assessments. The viable and devitalized samples in each CBM group were comparable with regard to fusion rates, bone volume fraction, μ-CT maturity grade, and histological features.

CONCLUSIONS

The cellular component of 2 commercially available CBMs yielded no additional benefits in terms of spinal fusion. Meanwhile, the groups with a fiber-based DBM demonstrated significantly higher fusion outcomes compared with the CBM groups with particulate DBM, indicating that the DBM component is probably the key determinant of fusion.

CLINICAL RELEVANCE

Data from the current study demonstrate that cells yielded no additional benefit in spinal fusion and emphasize the need for well-designed clinical studies on cellular graft materials.

Melatonin prevents the binding of vascular endothelial growth factor to its receptor and promotes the expression of extracellular matrix-associated genes in nucleus pulposus cells

The mechanisms of intervertebral disc degeneration (IDD) involve numerous factors, including loss of the extracellular matrix (ECM) and vascular ingrowth. Melatonin has been reported to protect intervertebral discs (IVDs) from degeneration and to exert a potential anti-angiogenic effect. The aim of the present study was to investigate the anti-angiogenic and anabolic effects of melatonin in IVDs. Human nucleus pulposus (NP) and degenerative nucleus pulposus (DNP) cells were isolated and treated with melatonin. The results indicated that melatonin promoted ECM synthesis and NP cell proliferation. In addition, an NP/DNP and human umbilical vein endothelial cell (HUVEC) co-culture model was used to investigate the anti-angiogenesis effect of melatonin. Melatonin was indicated to suppress tube formation and migration of HUVECs in culture with NP cell-conditioned medium, as well as in an NP cell co-culture model. Fluorescence-labeled vascular endothelial growth factor (VEGF) was used to study the binding between VEGF and its receptor. The results of the present study indicated that melatonin exerts an angiogenic effect via inhibition of the binding of VEGF to its receptor in HUVECs. Taken together, these results suggest that melatonin is a potential agent to prevent IDD.

The impact and distinction of 'lipid healthy but obese' and 'lipid abnormal but not obese' phenotypes on lumbar disc degeneration in Chinese

Background

Lipid abnormality and obesity have been proposed to be associated with lumbar disc degeneration, but little is known about the effect of ‘lipid healthy but obese’ (LH-O) and ‘lipid abnormal but not obese’ (LA-NO) phenotypes on lumbar disc degeneration in Chinese. The study aims to determine the impact and distinction of LH-O and LA-NO phenotypes on lumbar disc degeneration in Chinese, and to identify the association of related factors with risk of lumbar disc degeneration.

Methods

A total of 678 individuals were included with lumbar magnetic resonance imaging, serum lipid levels and anthropometric measurements. Obesity was defined on the basis of body mass index or waist to hip ratio (WHR). Pfirrmann score and Weishaupt’s scale were utilized to assess the degree of disc degeneration and facet joint degeneration.

Results

The incidence of the LH-O and LA-NO phenotypes were 11.4% and 18.1%, respectively. LA-NO phenotype demonstrates a high incidence for disc degeneration (P < 0.05), while LH-O phenotype confers a severe disc degeneration grade (P < 0.05). No statistical difference in the percentage of severe facet joint degeneration grade in each group (P > 0.05). Elevated triglycerides and greater WHR may be the risk factors for lumbar disc degeneration in Chinese.

Conclusion

LH-O and LA-NO phenotypes are common with different status of disc degeneration in Chinese. Elevated triglycerides and abdominal obesity appear to play crucial roles in the development of lumbar disc degeneration.

Genipin-crosslinked decellularized annulus fibrosus hydrogels induces tissue-specific differentiation of bone mesenchymal stem cells and intervertebral disc regeneration

Biomaterial-based therapy that can restore annulus fibrosus (AF) function in early stage and promote endogenous repair of AF tissues is a promising approach for AF tissue repair. In this study, we established a genipin-crosslinked decellularized AF hydrogels (g-DAF-G) that are injectable and could manifest better in situ formability than noncrosslinked decellularized AF hydrogel, while preserving the capacity of directing differentiation of human bone mesenchymal stem cells (hBMSCs) towards AF cells. Hematoxylin and eosin staining, 4',6-diamidino-2-phenylindole staining, and so forth showed that the majority of cellular components were removed, whereas extracellular matrix and microstructure were largely preserved. The storage modulus increased from 465.5 ± 9.4 Pa to 3.29 ± 0.24 MPa after 0.02% genipin crosslinking of decellularized AF hydrogels (DAF-G) to form g-DAF-G. AF-specific genes (COL1A1, COL5A1, TNMD, IBSP, FBLN1) were significantly higher in DAF-G and g-DAF-G groups than that in control group after 21 days of culturing. g-DAF-G significantly restored nucleus pulposus water content and preserved intervertebral structure in vivo. Summarily, we produced a novel AF regeneration biomaterial, g-DAF-G, which exhibited well biocompatibility, great bioactivity, and much higher mechanical strength than DAF-G. This study will provide an easy and fast therapeutic alternative to repair AF injuries or tears.