Injection of human umbilical tissue–derived cells into the nucleus pulposus alters the course of intervertebral disc degeneration in vivo

Background contextPatients often present to spine clinic with evidence of intervertebral disc degeneration (IDD). If conservative management fails, a safe and effective injection directly into the disc might be preferable to the risks and morbidity of surgery.PurposeTo determine whether injecting human umbilical tissue–derived cells (hUTC) into the nucleus pulposus (NP) might improve the course of IDD.DesignProspective, randomized, blinded placebo–controlled in vivo study.Patient sampleSkeletally mature New Zealand white rabbits.Outcome measuresDegree of IDD based on magnetic resonance imaging (MRI), biomechanics, and histology.MethodsThirty skeletally mature New Zealand white rabbits were used in a previously validated rabbit annulotomy model for IDD. Discs L2–L3, L3–L4, and L4–L5 were surgically exposed and punctured to induce degeneration and then 3 weeks later the same discs were injected with hUTC with or without a hydrogel carrier. Serial MRIs obtained at 0, 3, 6, and 12 weeks were analyzed for evidence of degeneration qualitatively and quantitatively via NP area and MRI Index. The rabbits were sacrificed at 12 weeks and discs L4–L5 were analyzed histologically. The L3–L4 discs were fixed to a robotic arm and subjected to uniaxial compression, and viscoelastic displacement curves were generated.ResultsQualitatively, the MRIs demonstrated no evidence of degeneration in the control group over the course of 12 weeks. The punctured group yielded MRIs with the evidence of disc height loss and darkening, suggestive of degeneration. The three treatment groups (cells alone, carrier alone, or cells+carrier) generated MRIs with less qualitative evidence of degeneration than the punctured group. MRI Index and area for the cell and the cell+carrier groups were significantly distinct from the punctured group at 12 weeks. The carrier group generated MRI data that fell between control and punctured values but failed to reach a statistically significant difference from the punctured values. There were no statistically significant MRI differences among the three treatment groups. The treated groups also demonstrated viscoelastic properties that were distinct from the control and punctured values, with the cell curve more similar to the punctured curve and the carrier curve and carrier+cells curve more similar to the control curve (although no creep differences achieved statistical significance). There was some histological evidence of improved cellularity and disc architecture in the treated discs compared with the punctured discs.ConclusionsTreatment of degenerating rabbit intervertebral discs with hUTC in a hydrogel carrier solution might help restore the MRI, histological, and biomechanical properties toward those of nondegenerated controls. Treatment with cells in saline or a hydrogel carrier devoid of cells also might help restore some imaging, architectural, and physical properties to the degenerating disc. These data support the potential use of therapeutic cells in the treatment of disc degeneration.     

Injection of AAV2-BMP2 and AAV2-TIMP1 into the nucleus pulposus slows the course of intervertebral disc degeneration in an in vivo rabbit model

Background contextIntervertebral disc degeneration (IDD) is a common cause of back pain. Patients who fail conservative management may face the morbidity of surgery. Alternative treatment modalities could have a significant impact on disease progression and patients’ quality of life.PurposeTo determine if the injection of a virus vector carrying a therapeutic gene directly into the nucleus pulposus improves the course of IDD.Study designProspective randomized controlled animal study.MethodsThirty-four skeletally mature New Zealand white rabbits were used. In the treatment group, L2–L3, L3–L4, and L4–L5 discs were punctured in accordance with a previously validated rabbit annulotomy model for IDD and then subsequently treated with adeno-associated virus serotype 2 (AAV2) vector carrying genes for either bone morphogenetic protein 2 (BMP2) or tissue inhibitor of metalloproteinase 1 (TIMP1). A nonoperative control group, nonpunctured sham surgical group, and punctured control group were also evaluated. Serial magnetic resonance imaging (MRI) studies at 0, 6, and 12 weeks were obtained, and a validated MRI analysis program was used to quantify degeneration. The rabbits were sacrificed at 12 weeks, and L4–L5 discs were analyzed histologically. Viscoelastic properties of the L3–L4 discs were analyzed using uniaxial load-normalized displacement testing. Creep curves were mathematically modeled according to a previously validated two-phase exponential model. Serum samples obtained at 0, 6, and 12 weeks were assayed for biochemical evidence of degeneration.ResultsThe punctured group demonstrated MRI and histologic evidence of degeneration as expected. The treatment groups demonstrated less MRI and histologic evidence of degeneration than the punctured group. The serum biochemical marker C-telopeptide of collagen type II increased rapidly in the punctured group, but the treated groups returned to control values by 12 weeks. The treatment groups demonstrated several viscoelastic properties that were distinct from control and punctured values.ConclusionsTreatment of punctured rabbit intervertebral discs with AAV2-BMP2 or AAV2-TIMP1 helps delay degenerative changes, as seen on MRI, histologic sampling, serum biochemical analysis, and biomechanical testing. Although data from animal models should be extrapolated to the human condition with caution, this study supports the potential use of gene therapy for the treatment of IDD.     

Intradiscal injections of osteogenic protein-1 restore the viscoelastic properties of degenerated intervertebral discs

BACKGROUND CONTEXT: Using biochemical, histological, and radiological parameters in a rabbit model of intervertebral disc (IVD) degeneration, the intradiscal injection of a growth factor, such as osteogenic protein-1 (OP-1), has been shown to regenerate the IVD. However, very little is known about how such a biological therapeutic approach affects the biomechanical properties of the degenerated IVD. PURPOSE: To investigate the effects of an intradiscal injection of OP-1 on the biomechanical properties of IVDs in the rabbit annular-puncture disc degeneration model and to determine their relationship to biochemical properties. STUDY DESIGN/SETTING: In vivo study on the effects of intradiscally administered OP-1 on the biomechanical and biochemical properties of IVDs in the rabbit annular-puncture disc degeneration model. METHODS: New Zealand White rabbits (n=16) underwent annulus fibrosus (AF) puncture, using an 18-gauge needle, at L2-L3 and L4-L5 (L3-L4: nonpunctured control). Four weeks later, the punctured discs received an injection of either 5% lactose (10 microL) or OP-1 (100 microg/10 microL of 5% lactose) into the nucleus pulposus (NP). The disc height was radiographically monitored biweekly. After sacrifice and removal of bone-disc-bone complexes 8 weeks postinjection, the dynamic viscoelastic properties of the IVDs were tested by applying a cycle of sinusoidal strain in uniaxial compression at six loading frequencies (0.05 to 2 Hz). The biochemical properties of the dissected IVDs were then analyzed and correlated with the biomechanical properties. RESULTS: A single injection of OP-1 significantly restored disc height when compared with the lactose-injected discs (OP-1 vs. lactose, p<.001). The elastic modulus of the IVDs in the OP-1-injected discs was significantly higher than that in the lactose-injected discs at all frequencies (mean: +43%, p<.001). The viscous modulus in the OP-1-injected discs was significantly higher at 0.05, 0.2, 0.5, and 1 Hz (mean: +55%, p<.001) and showed higher tendencies at other frequencies (p=.08-.09). For both moduli, no significant differences were observed between the OP-1-injected and the nonpunctured control discs. The OP-1 injection significantly increased the proteoglycan (PG) content in the NP and AF, and the collagen content in the NP (p<.001-.05). Both elastic and viscous moduli showed significant positive correlations with PG content in the NP and collagen content in the NP and AF (Rho=.357-.466, p=.010-.047). CONCLUSIONS: We have shown for the first time that an injection of the growth factor, OP-1, restored the biomechanical properties of IVDs in a rabbit model of IVD degeneration. Comparing biomechanical with biochemical data suggests that the OP-1-induced biomechanical restoration was a consequence of increased activities of anabolic pathways that resulted in biochemical changes in the IVD.     

Patterns of lumbar disc degeneration are different in degenerative disc disease and disc prolapse magnetic resonance imaging analysis of 224 patients

Background contextExisting research on lumbar disc degeneration has remained inconclusive regarding its etiology, pathogenesis, symptomatology, prevention, and management. Degenerative disc disease (DDD) and disc prolapse (DP) are common diseases affecting the lumbar discs. Although they manifest clinically differently, existing studies on disc degeneration have included patients with both these features, leading to wide variations in observations. The possible relationship or disaffect between DDD and DP is not fully evaluated.PurposeTo analyze the patterns of lumbar disc degeneration in patients with chronic back pain and DDD and those with acute DP.Study designProspective, magnetic resonance imaging–based radiological study.MethodsTwo groups of patients (aged 20–50 years) were prospectively studied. Group 1 included patients requiring a single level microdiscectomy for acute DP. Group 2 included patients with chronic low back pain and DDD. Discs were assessed by magnetic resonance imaging through Pfirmann grading, Schmorl nodes, Modic changes, and the total end-plate damage score for all the five lumbar discs.ResultsGroup 1 (DP) had 91 patients and group 2 (DDD) had 133 patients. DP and DDD patients differed significantly in the number, extent, and severity of degeneration. DDD patients had a significantly higher number of degenerated discs than DP patients (p<.000). The incidence of multilevel and pan-lumbar degeneration was also significantly higher in DDD group. The pattern of degeneration also differed in both the groups. DDD patients had predominant upper lumbar involvement, whereas DP patients had mainly lower lumbar degeneration. Modic changes were more common in DP patients, especially at the prolapsed level. Modic changes were present in 37% of prolapsed levels compared with 9.9% of normal discs (p<.00). The total end-plate damage score had a positive correlation with disc degeneration in both the groups. Further the mean total end-plate damage score at prolapsed level was also significantly higher.ConclusionThe results suggest that patients with disc prolapse, and those with back pain with DDD are clinically and radiologically different groups of patients with varying patterns, severity, and extent of disc degeneration. This is the first study in literature to compare and identify significant differences in these two commonly encountered patient groups. In patients with single-level DP, the majority of the other discs are nondegenerate, the lower lumbar spine is predominantly involved and the end-plate damage is higher. Patients with back pain and DDD have larger number of degenerate discs, early multilevel degeneration, and predominant upper lumbar degeneration. The knowledge that these two groups of patients are different clinically and radiologically is critical for our improved understanding of the disease and for future studies on disc degeneration and disc prolapse.     

Nucleus pulposus degeneration alters properties of resident progenitor cells

Background contextThe intervertebral disc (IVD) possesses a minimal capability for self-repair and regeneration. Changes in the differentiation of resident progenitor cells can represent diminished tissue regeneration and a loss of homeostasis. We previously showed that progenitor cells reside in the nucleus pulposus (NP). The effect of the degenerative process on these cells remains unclear.PurposeWe sought to explore the effect of IVD degeneration on the abundance of resident progenitor cells in the NP, their differentiation potential, and their ability to give rise to NP-like cells. We hypothesize that disc degeneration affects those properties.Study designNucleus pulposus cells derived from healthy and degenerated discs were methodically compared for proliferation, differentiation potential, and ability to generate NP-like cells.MethodsIntervertebral disc degeneration was induced in 10 skeletally, mature mini pigs using annular injury approach. Degeneration was induced in three target discs, whereas intact adjacent discs served as controls. The disc degeneration was monitored using magnetic resonance imaging for 6 to 8 weeks. After there was a clear evidence of degeneration, we isolated and compared cells from degenerated discs (D-NP cells [NP-derived cells from porcine degenerated discs]) with cells isolated from healthy discs (H-NP cells) obtained from the same animal.ResultsThe comparison showed that D-NP cells had a significantly higher colony-forming unit rate and a higher proliferation rate in vitro. Our data also indicate that although both cell types are able to differentiate into mesenchymal lineages, H-NP cells exhibit significantly greater differentiation toward the chondrogenic lineage and NP-like cells than D-NP cells, displaying greater production of glycosaminoglycans and higher gene expression of aggrecan and collagen IIa.ConclusionsBased on these findings, we conclude that IVD degeneration has a meaningful effect on the cells in the NP. D-NP cells clearly go through the regenerative process; however, this process is not powerful enough to facilitate full regeneration of the disc and reverse the degenerative course. These findings facilitate deeper understanding of the IVD degeneration process and trigger further studies that will contribute to development of novel therapies for IVD degeneration.     

大鼠正常与退变性髓核突出导致神经根性疼痛的对比研究

目的探讨正常与退变髓核突出对大鼠疼痛阈值以及背根神经节中TNF-α表达的影响,研究椎间盘退变与神经根性疼痛之间的关系。方法72只大鼠随机分为4组:正常对照组(n=18)、假手术组(n=19)、正常髓核(N-NP)组(n=16)和退变髓核(P-NP)组(n=19)。对P-NP组大鼠利用尾椎椎间盘纤维环穿刺的方法建立椎间盘退变模型。分别取出N-NP组和P-NP组大鼠自体的正常髓核与退变髓核组织,置于手术显露后的腰5左侧神经根处,建立髓核突出致神经根性疼痛动物模型。采用行为学测试的方法分别观察各组大鼠术前1天,术后1、4、7、10、14、21天机械刺激阈值与热刺激阈值的变化;采用免疫组化方法分别检测术后第4、14天各组大鼠背根神经节中TNF-α的表达。结果行尾椎间盘纤维环穿刺后2周,组织学与MRI检查均证实椎间盘组织发生明显退变。对照组和假手术组动物未出现明显的痛觉过敏现象,N-NP组和P-NP组大鼠机械性刺激阈值均显著下降,该痛觉过敏现象持续至术后2周消失;与正常髓核组织相比,退变髓核所致机械性刺激阈值下降程度更为严重。各实验组均未发生热刺激阈值的规律性变化。术后第4、14天对照组和假手术组背根神经节中未见TNF-α明显表达,而正常及退变髓核组TNF-α表达量均显著升高。结论大鼠尾椎纤维环穿刺是建立大鼠椎间盘退变模型的一种有效方法。与正常髓核组织相比,发生退变的髓核组织可导致神经根性疼痛的加重,提示椎间盘退变过程中释放的炎症因子在疼痛的发生机制中可能起到了重要作用。     

Experimental disc degeneration due to endplate injury

The aim of this study was to create an experimental model of disc degeneration that closely mimicked human disc degeneration. In six domestic pigs, an L4 cranial endplate perforation into the nucleus pulposus was made. Three months postoperatively, compressive testing was performed on the L2-L4 motion segments, and intradiscal pressure was measured in the intervening discs. Histochemical and morphologic examinations were made on the excised degenerated and adjacent discs. A significant reduction in water content was observed in the outer anterior annulus of the degenerated disc. In the nucleus, the proteoglycan content was significantly reduced, as well as the cellularity, although not significantly. The nucleus lost its gel-like structure and was discolored, and there was delamination of annular layers. Intradiscal pressure in the nucleus was significantly lower in the degenerated disc. In conclusion, experimental degeneration of the intervertebral disc induced by endplate penetration resembled human disc degeneration, as exemplified by biochemical and structural changes.     

Anular delamination strength of human lumbar intervertebral disc

Introduction

Progression of intervertebral disc (IVD) herniation does not occur exclusively in a linear manner through the anulus fibrosus (AF), but can migrate circumferentially due to localized AF delamination. Consequently, resistance to delamination is an important factor in determining risk of herniation progression. The inter-lamellar matrix located between the AF layers is responsible for resisting this delamination; however, its mechanical properties are largely unknown. This study aimed to determine the mechanical properties of the inter-lamellar matrix in human AF samples via a peel test.

Materials and methods

Seventeen human IVDs (degeneration grades of 2–3) were obtained from six lumbar spines. From these 17 discs, 53 tissue samples were obtained from the superficial and deep regions of the anterior and posterior AF. Samples were dissected into a ‘T’ configuration to facilitate a T-peel test (or 180-degree peel test) by initiating delamination between the two middle AF layers.

Results

Peel strength was found to be 33?% higher in tissues obtained from the superficial AF region as compared with the deep region (p?=?0.047).

Conclusion

This finding may indicate a higher resistance to delamination in the superficial AF, and as a result, delamination and herniation progression may occur more readily in the deeper layers of the AF.     

腰椎间盘基质降解酶的研究

椎间盘基质大分子的变化可使其生物力学性能丧失,这种变化涉及到能使基质中的胶原和蛋白多糖发生改变的细胞外酶。作者以氚－Ⅰ型胶原为底物,对４１例手术治疗的腰椎间盘突出者的椎间盘组织及３４个正常尸检腰椎间盘组织作了胶原酶活力的测定,纤维环与髓核分别测定。用ＰＡＧＥ法以变性胶原为底物,光密度扫描峰值面积自动积分法对６个正常与１６个退变椎间盘作了中性蛋白酶相对含量的初步研究。结果显示,正常纤维环与髓核的胶原酶活力相似,仅含极微量的中性蛋白酶,退变椎间盘胶原酶与中性蛋白酶活性明显增强,尤其是退变髓核。破裂型椎间盘突出者的髓核胶原酶活力高于凸起型。提示基质降解酶在腰椎间盘退变过程中起重要作用,退变程度的差异是临床不同突出类型的生化基础。     

Stable mechanical environments created by a low-tension traction device is beneficial for the regeneration and repair of degenerated intervertebral discs

BACKGROUNDBy blocking the cascade of reactions leading to intervertebral disc degeneration through immobilization-traction, a delay in intervertebral disc degeneration and its regeneration, to some extent, has been observed. However, the precise balance of regulation of the microenvironment of intervertebral disc biomechanics and coordination of the complex spatiotemporal reconstruction of the extracellular matrix have not yet been solved, and clinical results are far from successful.PURPOSEIn the present study, a mechanical degeneration model was constructed to evaluate the possibility and effectiveness of disc regeneration or repair through low-tension traction of degenerated discs so as to provide basic biomechanical information for clinical optimization of the traction device and to establish traction parameters for prevention and treatment of disc degeneration.STUDY DESIGNA macro-, micro-, and nano-level structural analysis of degenerative discs of rat tail before and after controlled traction.METHODSSix-month-old male Sprague-Dawley rats were randomly divided into seven groups: Group A: control group (instrumented with Kirschner [K]-wires only); Group B: Model group (caudal vertebrae immobilized using a custom-made external device to fix four caudal vertebrae [Co7−Co10], while Co8−Co9 vertebrae underwent 4 weeks of compression to induce disc degeneration); Group C: experimental control group (devices removed after the 4 week compression described in Group B, and recovered by themselves for 4 weeks). The remaining four groups represented intervention groups (Groups D and F: Co8−Co9 vertebrae compressed for 4 weeks followed by 2 or 4 weeks of in situ traction, respectively; Groups E and G: vertebrae compressed for 4 weeks followed by 2 or 4 weeks of excessive traction, respectively). X-ray and magnetic resonance imaging were performed at each time point to measure disc height and T2 signal intensity. At the end of the experiment, the animals were euthanized and tail vertebrae harvested for analysis of intervertebral disc histopathology, proteoglycan content, elastic modulus of fibers of the annulus fibrosus (AF) and nucleus pulposus (NP), and microstructure of the bony end plate.RESULTSAfter 2 to 4 weeks of continuous traction (in situ and excessive traction), the Co8–Co9 intervertebral disc space of rats in Groups D to G increased significantly compared with Groups B and C (p < .05). In addition, signs of tissue regeneration were apparent in all four intervention groups (D–G). In addition, histologic scores of the intervention groups (D–G) were significantly lower than those in the model and experimental control groups (Groups B and C, respectively), although no significant difference was found between those four groups. Compared with the model group (Group B), total proteoglycan content of the NP in the intervention groups (D–G) increased significantly (p < .05). After 2 to 4 weeks of intervention (in situ and excessive traction), the morphology of pores in the bony end plate, their number, and the diameter had recovered significantly compared with those in Group B. The in situ traction group was superior to the excessive traction group, and 4 weeks in situ group significantly superior to the 2 weeks group. In all intervention groups, in both the inner and outer AF, mean fibril diameter decreased significantly (p < .05), although they remained larger in the excessive traction group than that in the in situ traction group. Consistent with trend in collagen fiber diameter, the outer AF was stiffer than the inner, and the modulus of the AF in each intervention group not significantly different from that of the control group (Group A) except Group C. However, within the NP, the variation in trend in diameter and modulus of collagen fibers was essentially inconsistent with that of the AF.CONCLUSIONSDegenerated discs exhibit greater reconstruction after low tension traction. It is clear that the intervertebral disc mechanical microenvironment depends to a greater extent on low-tension traction than high-tension traction.     

Low energy extracorporeal shock wave therapy combined with low tension traction can better reshape the microenvironment in degenerated intervertebral disc regeneration and repair

BACKGROUNDLow-tension traction is more effective than high-tension traction in restoring the height and rehydration of a degenerated disc and to some extent the bony endplate. This might better reshape the microenvironment for disc regeneration and repair. However, the repair of the combination of endplate sclerosis, osteophyte formation, and even collapse leading to partial or nearly complete occlusion of the nutrient channel is greatly limited.PURPOSETo evaluate the effectiveness of low-intensity extracorporeal shock wave therapy (ESWT) combined with low tension traction for regeneration and repair of moderately and severely degenerated discs; to explore the possible mechanism of action.STUDY DESIGNAnimal study of a rat model of degenerated discs.METHODSA total of thirty-five 6-month old male Sprague-Dawley rats were randomly assigned to one of five groups (n=7, each group). In Group A (model group), caudal vertebrae were immobilized using a custom-made external device to fix four caudal vertebrae (Co7–Co10) whereas Co8–Co9 underwent 4 weeks of compression to induce moderate disc degeneration. In Group B (experimental control group), as in Group A, disc degeneration was successfully induced after which the fixed device was removed for 8 weeks of self-recovery. The remaining three groups of rats represented the intervention Groups (C–E): after successful generation of disc degeneration in Group C (com - 4w/tra - 4w) and Group D (com - 4w/ESWT), as described for group A, low-tension traction (in-situ traction) or low-energy ESWT was administered for 4 weeks (ESWT parameters: intensity: 0.15 Mpa; frequency: 1 Hz; impact: 1,000 each time; once/week, 4 times in total); Group E (com - 4w/tra - 4w/ESWT): disc degeneration as described for group A, low-tension traction combined with low-energy ESWT was conducted (ESWT parameters as Group D). After experimentation, caudal vertebrae were harvested and disc height, T2 signal intensity, disc morphology, total glycosaminoglycan (GAG) content, gene expression, structure of the Co8–Co9 bony endplates and elastic moduli of the discs were measured.RESULTSAfter continuous low-tension traction, low energy ESWT intervention or combined intervention, the degenerated discs effectively recovered their height and became rehydrated. However, the response in Group D was weaker than in the other intervention groups in terms of restoration of intervertebral disc (IVD) height, whereas Group E was superior in disc rehydration. Tissue regeneration was evident in Groups C to E using different interventions. No apparent tissue regeneration was observed in the experimental control group (Group B). The histological scores of the three intervention groups (Groups C–E) were lower than those of Groups A or B (p<.0001), and the scores of Groups C and E were significantly lower than those of Group D (p<.05), but not Group C versus Group E (p>.05). Compared with the intervention groups (Groups C–E), total GAG content of the nucleus pulposus (NP) in Group B did not increase significantly (p>.05). There was also no significant difference in the total GAG content between Groups A and B (p>.05). Of the three intervention groups, the recovery of NP GAG content was greatest in Group E. The expression of collagen I and II, and aggrecan in the annulus fibrosus (AF) was up-regulated (p<.05), whereas the expression of MMP-3, MMP-13, and ADAMTS-4 was down-regulated (p<.05). Of the groups, Group E displayed the greatest degree of regulation. The trend in regulation of gene expression in the NP was essentially consistent with that of the AF, of which Group E was the greatest. In the intervention groups (Groups C–E), compared with Group A, the pore structure of the bony endplate displayed clear changes. The number of pores in the endplate in Groups C to E was significantly higher than in Group A (p<.0001), among which Group C versus Group D (p=.9724), and Group C versus Group E (p=.0116). There was no significant difference between Groups A and B (p=.5261). In addition, the pore diameter also increased, the trend essentially the same as that of pore density. There was no significant difference between the three intervention groups (p=.7213). It is worth noting that, compared with Groups A and B, peripheral pore density and size in Groups D and E of the three intervention groups recovered significantly. The elastic modulus and diameter of collagen fibers in the AF and NP varied with the type of intervention. Low tension traction combined with ESWT resulted in the greatest impact on the diameter and modulus of collagen fibers.CONCLUSIONSLow energy ESWT combined with low tension traction provided a more stable intervertebral environment for the regeneration and repair of moderate and severe degenerative discs. Low energy ESWT promoted the regeneration of disc matrix by reducing MMP-3, MMP-13, and ADAMTS-4 resulting in inhibition of collagen degradation. Although axial traction promoted the recovery of height and rehydration of the IVD, combined with low energy ESWT, the micro-nano structure of the bony endplate underwent positive reconstruction, tension in the annulus of the AF and nuclear stress of the NP declined, and the biomechanical microenvironment required for IVD regeneration and repair was reshaped.     

Asymmetry between the superior and inferior endplates is a risk factor for lumbar disc degeneration

Endplate pathology plays an important role in the development of lumbar disc degeneration. Previous research paid little attention to differences between the superior and inferior endplates as a possible risk factor for disc degeneration. The purpose of this study was to test the hypothesis that asymmetry between the superior and inferior endplates is a risk factor for the development of lumbar disc degeneration. A total of 134 patients with lumbar disc herniation (LDH) and 100 healthy adults (“Controls”) underwent magnetic resonance imaging scans. Each disc was categorized as non‐degenerated (Pfirrmann grades I–II) or degenerated (Pfirrmann grades III–V) and get the following three groups: “Degenerated LDH” discs (n = 145), “Non‐degenerated LDH” discs (n = 525) and “Non‐degenerated Control” discs (n = 500). On mid‐sagittal image, the lumbar endplate morphology could be categorized into three types: Flat, concave, and irregular. Superior and inferior endplates of a given disc were “symmetric” if both were of the same type, and “asymmetric” if they were of different types. The proportion of asymmetric endplates at L4–5 was higher in the “Degenerated LDH” discs group (47%) than in the “Non‐degenerated LDH” discs group (21%) or “Non‐degenerated Control” discs group (7%) (p < 0.05). At L5‐S1 the proportions were 73%, 55%, and 38% (p < 0.05). Asymmetry of superior and inferior endplates in the mid‐sagittal plane is a risk factor for lumbar disc degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2469–2475, 2018.

     

Mesenchymal progenitor cells primed with pentosan polysulfate promote lumbar intervertebral disc regeneration in an ovine model of microdiscectomy

Background Context

Neural compression associated with lumbar disc herniation is usually managed surgically by microdiscectomy. However, 10%–20% of patients re-present with debilitating back pain, and approximately 15% require further surgery.

Biochemical validity of imaging techniques (X-ray,MRI, and dGEMRIC) in degenerative disc disease of the human cervical spine—an in vivo study

Background Context

On a molecular level, maturation or degeneration of human intervertebral disc is among others expressed by the content of glycosaminoglycans (GAGs). According to the degenerative status, the disc content can differ in nucleus pulposus (NP) and annulus fibrosus (AF), respectively. Research in this area was conducted mostly on postmortem samples. Although several radiological classification systems exist, none includes biochemical features. Therefore, we focused our in vivo study on a widely spread and less expensive imaging technique for the cervical spine and the correlation of radiological patterns to biochemical equivalents in the intervertebral discs.

Lumbar Intervertebral Disc Herniation Following Experimental Intradiscal Pressure Increase

Summary  An experimental biomechanical model of overload and rupture of the annulus fibrosus (AF) and lumbar disc herniation was achieved by increasing intradiscal pressure while keeping disc height constant in 69 motion segments at the L4–L5 level excised from cadaveric spines. The experiments were made on 53 specimens in neutral posture and on 16 specimens in flexion posture.  The values found for the rupture intradiscal pressure (RIP) ranged from 750 to 1300 kPa for neutral posture and the maximum RIP in anterior flexion was 1177 kPa.  The degree of disc degeneration was assessed by vertebral transcorporeal discography (previous to experiment) and by sectioning the intervertebral disc after the experiment.  The herniated lumbar intervertebral disc model by intradiscal pressure increase makes possible these assertions: –*The correlation between the degree of AF degeneration and the RIP is significant: the maximum RIP corresponds to a nondegenerated AF and the less RIP can tear only a degenerated AF; so disc herniation only occurs to discs with torn AF. –*AF breaking is more often paramedian, left or right. The place of AF breaking was paramedian in 70.3% cases, median in 9.45% cases and posterolateral in 20.25% cases.     

P物质阳性神经纤维在退变腰椎间盘的分布及意义

目的研究P物质（substance P,SP）阳性神经纤维在腰椎间盘中的出现及分布,以探讨其在椎间盘退变中的潜在作用。方法收集16例患者的21个病变腰椎间盘和来自于新鲜尸体的12个正常对照椎间盘,行组织学检查和SP免疫组织化学染色检查。结果SP阳性神经纤维偶见于正常椎间盘,在病变椎间盘内可见较多的SP免疫反应阳性神经纤维分布,阳性神经纤维数量与腰椎间盘退变程度呈正相关。结论腰椎间盘退变程度和SP阳性神经纤维数量有明显的相关性,SP可能作为神经炎性介质加速了腰椎间盘的退变。     

Senescence mechanisms of nucleus pulposus chondrocytes in human intervertebral discs

Background contextThe population of senescent disc cells has been shown to increase in degenerated or herniated discs. However, the mechanism and signaling pathway involved in the senescence of nucleus pulposus (NP) chondrocytes are unknown.PurposeTo demonstrate the mechanisms involved in the senescence of NP chondrocytes.Study design/settingSenescence-related markers were assessed in the surgically obtained human NP specimens.Patient sampleNP specimens remaining in the central region of the intervertebral disc were obtained from 25 patients (mean: 49 years, range: 20–75 years) undergoing discectomy. Based on the preoperative magnetic resonance images, there were 3 patients with Grade II degeneration, 17 patients with Grade III degeneration, and 5 patients with Grade IV degeneration.Outcome measuresWe examined cell senescence markers (senescence-associated β-galactosidase [SA-β-gal], telomere length, telomerase activity, p53, p21, pRB, and p16) and the hydrogen peroxide (H₂O₂) content as a marker for an oxidative stress in the human NP specimens.MethodsSA-β-gal expression, telomere length, telomerase activity, and H₂O₂ content as well as their relationships with age and degeneration grades were analyzed. For the mechanism involved in the senescence of NP chondrocytes, expressions of p53, p21, pRB, and p16 in these cells were assessed with immunohistochemistry and Western blotting.ResultsThe percentages of SA-β-gal-positive NP chondrocytes increased with age (r=.82, p<.001), whereas the telomere length and telomerase activity declined (r=?.41, p=.045; r=?.52, p=.008, respectively) However, there was no significant correlation between age and H₂O₂ contents (p=.18). The NP specimens with Grade III or Grade IV degeneration showed significantly higher percentages of SA-β-gal-positive NP chondrocytes than those with Grade II degeneration (p=.01 and p=.025, respectively). Immunohistochemistry showed that the senescent NP chondrocytes in all the specimens expressed p53, p21, and pRB, but a few NP chondrocytes in only two specimens expressed p16. Western blotting showed that the expressions of p53, p21, and pRB displayed a corresponding pattern, that is, a strong p53 expression led to strong p21 and pRB expressions and vice versa.ConclusionsOur in vivo study demonstrated that senescent NP chondrocytes increased or accumulated in the NP with increasing age and advancing disc degeneration. The NP chondrocytes in the aging discs exhibited characteristic senescent features such as an increased SA-β-gal expression, shortened telomeres, and decreased telomerase activity. We further demonstrated that the telomere-based p53-p21-pRB pathway, rather than the stress-based p16-pRB pathway, plays a more important role in the senescence of NP chondrocytes in an in vivo condition. Our results suggest that prevention or reversal of the senescence of NP chondrocytes can be a novel therapeutic target for human disc degeneration.     

A novel rabbit disc degeneration model induced by fibronectin fragment

ObjectiveTo establish a novel and useful rabbit model of lumbar disc degeneration using microinjection of a fibronectin fragment.MethodsThirty-two rabbits underwent injection of N-terminal 30 kDa fibronectin fragment (Fn-f) (Group A, n = 12; Group B, n = 4) or phosphate buffered saline (PBS) (Group C, n = 12; Group D, n = 4) into the lumbar discs using a 32-gauge microsyringe. Two rabbits (Group E) with no treatment were sacrificed to examine the proteoglycan synthesis of neucleus pulposus (NP) using ³⁵S-sulfate incorporation assay. At the 4-, 8-, 12-, and 16-week time points, the discs were examined histologically, radiographically and with proteoglycan synthesis.Results(1) Histology demonstrated a progressive loss of cell numbers in NP and architecture disorganization in NP and annulus fibrosus (AF) over the study period. (2) Radiology: comparing with the PBS-injected discs, the Fn-f-injected discs exhibited no significant differences in disc heights at the 4-week time point, but significant decreases in disc heights at the 8-, 12-, and 16-week time points (P < 0.01). Apparent anterior osteophytes formed at the 12-week time point and enlarged remarkably by the 16-week time point in the Fn-f-injected spines. (3) Protoglycan synthesis in the Fn-f-injected discs decreased progressively (P < 0.01). At each time point, the Fn-f-injected discs showed significantly decreased proteoglycan synthesis compared with controls (P < 0.05 or P < 0.01).ConclusionsFn-f induced a progressively degenerative process in rabbit discs, which was consistent with the spontaneous degeneration in human. Fn-f induced degeneration seemed to be a novel and useful model for the study of disc degeneration at the molecular level.     

A longitudinal study of the matrix changes induced in the intervertebral disc by surgical damage to the annulus fibrosus.

A 5 x 5-mm anterolateral incision was made in the annulus fibrosus (AF) of lumbar discs of 16 sheep; four animals of similar age not operated on were used as controls. The experimental animals were sacrificed 2, 4, 6, 8, 12, and 18 months postoperatively (PO), and the incised and adjacent lumbar discs were collected. Discs were dissected into four zones: AF (zones 1 and 2) and nucleus pulposus (NP) (zones 3 and 4) corresponding to the half of the AF in which the cut was made and its opposite half, and the complementary halves of the NP. Each zone was analyzed for moisture, proteoglycan (PG), collagen, and noncollagenous protein (NCP) content. The PG extractability, aggregation, and hydrodynamic size were also examined. The NP of injured discs showed a significant loss of PGs and collagen 8 months PO, but NCP levels increased. In the incised discs, PG aggregation initially declined but recovered to within control values 6-8 months PO. The NP of discs adjacent to the incised disc also showed time-dependent changes in matrix components that included loss of collagen and PG; however, the AF matrix remained essentially uneffected. Double immunodiffusion studies indicated that a sizeable proportion of the NCPs present in the injured discs (but not the adjacent lumbar discs) were derived from serum.