Labral calcification in end‐stage osteoarthritis of the hip correlates with pain and clinical function

The acetabular labrum of the hip (ALH) is recognized as a clinically important structure, but knowledge about the pathophysiology of this fibrocartilage is scarce. In this prospective study we determined the prevalence of ALH calcification in patients with end‐stage osteoarthritis (OA) and analyzed the relationship of cartilage calcification (CC) with hip pain and clinical function. Cohort of 80 patients (70.2 ± 7.6years) with primary OA scheduled for total hip replacement. Harris Hip Score (HHS) was recorded preoperatively. Total ALH and femoral head (FH) were sampled intraoperatively. CC of the ALH and FH was analyzed by high‐resolution digital contact radiography. Histological degeneration of the ALH (Krenn‐Score) and FH (OARSI‐Score) was determined. Multivariate linear regression model and partial correlation analyses were performed. The prevalence of cartilage calcification both in the ALH and FH was 100%, while the amount of CC in the ALH was 1.55 times higher than in the FH (p < 0.001). There was a significant inverse regression between the amount of calcification of both the ALH and the FH and preoperative HHS (β_ALH = ?2.1, p = 0.04), (β_FH = ?2.9, p = 0.005), but pain was influenced only by ALH calcification (β_ALH = ?2.7, p = 0.008). Age‐adjusted, there was a significant correlation between cartilage calcification and histological degeneration (ALH:r_s = 0.53, p < 0.001/FH: r_s = 0.30, p = 0.007). Fibrocartilage and articular cartilage calcification are inseparable pathological findings in end‐stage osteoarthritis of the hip. Fibrocartilage calcification is associated with poor and painful hip function. Clinical significance: ALH fibrocartilage appears to be particularly prone to calcification, which may explain higher pain levels in individuals with a high degree of ALH calcification independent of age and histological degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1248–1255, 2018.

     

Apoptosis of human intervertebral discs after trauma compares to degenerated discs involving both receptor‐mediated and mitochondrial‐dependent pathways

Post‐traumatic disc degeneration with consecutive loss of reduction and kyphosis remains a debatable issue within both the operative and nonoperative treatment regimen of thoracolumbar spine fractures. Intervertebral disc (IVD) cell apoptosis has been suggested to play a vital role in promoting the degeneration process. To evaluate and compare apoptosis‐regulating signaling mechanisms, IVDs were obtained from patients with thoracolumbar spine fractures (n = 21), patients suffering from symptomatic IVD degeneration (n = 6), and from patients undergoing surgical resection of a primary vertebral tumor (n = 3 used as control samples). All tissues were prospectively analyzed in regards to caspase‐3/7, ‐8, and ‐9 activity, apoptosis‐receptor expression levels, and gene expression of the mitochondria‐bound apoptosis‐regulating proteins Bax and Bcl‐2. Morphologic changes characteristic for apoptotic cell death were confirmed by H&E staining. Statistical significance was designated at p < 0.05 using the Student's t‐test. Both traumatic and degenerative IVD demonstrated a significant increase of caspase‐3/7 activity with evident apoptosis. Although caspase‐3/7 activation was significantly greater in degenerated discs, both showed equally significant activation of the initiator caspases 8 and 9. Traumatic IVD alone demonstrated a significant increase of the Fas receptor (FasR), whereas the TNF receptor I (TNFR I) was equally up‐regulated in both morbid IVD groups. Only traumatic IVD showed distinct changes in up‐regulated TNF expression, in addition to significantly down‐regulated antiapoptotic Bcl‐2 protein. Our results suggest that post‐traumatic disc changes may be promoted and amplified by both the intrinsic mitochondria‐mediated and extrinsic receptor‐mediated apoptosis signaling pathways, which could be, in part, one possible explanation for developing subsequent disc degeneration. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:999–1006, 2008     

T2* mapping of ovine intervertebral discs: Normative data for cervical and lumbar spine

To obtain T2* values in histologically evaluated healthy ovine intervertebral discs of the cervical and lumbar spine. Intervertebral discs of nine sheep and nine lambs underwent histological assessment with the modified Boos score for grading of disc degeneration. Discs with a score <10 points (maximum = 40 points) underwent T2* mapping (n = 64). Mid‐sagittal T2* values were obtained in five regions: Anterior annulus fibrosus, anterior nucleus pulposus, central nucleus pulposus, posterior nucleus pulposus, and posterior annulus fibrosus. We noted a zonal T2* distribution with high values in the central nucleus and low T2* values in the anterior and posterior annulus fibrosus. The T2* values were higher in lamb than in sheep IVDs for both cervical and lumbar spine (p < 0.001). The T2* values were also higher in the cervical than in the lumbar spine (p = 0.029 for sheep and p < 0.001 for lamb IVDs). The T2* values obtained in these ovine intervertebral discs can serve as baseline values for future T2* measurements both in health and disease. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:717–724, 2016.     

Differential Effector Response of Amnion‐ and Adipose‐Derived Mesenchymal Stem Cells to Inflammation; Implications for Intradiscal Therapy

Intervertebral disc degeneration (IVDD) is a progressive condition marked by tissue destruction and inflammation. The therapeutic effector functions of mesenchymal stem cells (MSCs) makes them an attractive therapy for patients with IVDD. While several sources of MSCs exist, the optimal choice for use in the inflamed IVD remains a significant question. Adipose (AD)‐ and amnion (AM)‐derived MSCs have several advantages compared with other sources, however, no study has directly compared the impact of IVDD inflammation on their effector functions. Human MSCs were cultured in media with or without supplementation of interleukin‐1β (IL‐1β) and tumor necrosis factor‐α at concentrations reportedly produced by IVDD cells. MSC proliferation and production of pro‐ and anti‐inflammatory cytokines were quantified following 24 and 48 h of culture. Additionally, the osteogenic and chondrogenic potential of AD‐ and AM‐MSCs was characterized via histology and biochemical analysis following 28 days of culture. In inflammatory culture, AM‐MSCs produced significantly more anti‐inflammatory IL‐10 (14.47 ± 2.39 pg/ml; p = 0.004) and larger chondrogenic pellets (5.67 ± 0.26 mm²; p = 0.04) with greater percent area staining positively for glycosaminoglycan (82.03 ± 3.26%; p < 0.001) compared with AD‐MSCs (0.00 ± 0.00 pg/ml; 2.76 ± 0.18 mm²; 34.75 ± 2.49%; respectively). Conversely, AD‐MSCs proliferated more resulting in higher cell numbers (221,000 ± 8,021 cells; p = 0.048) and produced higher concentrations of pro‐inflammatory cytokines prostaglandin E₂ (1,118.30 ± 115.56 pg/ml; p = 0.030) and IL‐1β (185.40 ± 7.63 pg/ml; p = 0.010) compared with AM‐MSCs (109,667 ± 5,696 cells; 1,291.40 ± 78.47 pg/ml; 144.10 ± 4.57 pg/ml; respectively). AD‐MSCs produced more mineralized extracellular matrix (3.34 ± 0.05 relative absorbance units [RAU]; p < 0.001) compared with AM‐MSCs (1.08 ± 0.06 RAU). Under identical inflammatory conditions, a different effector response was observed with AM‐MSCs producing more anti‐inflammatories and demonstrating enhanced chondrogenesis compared with AD‐MSCs, which produced more pro‐inflammatory cytokines and demonstrated enhanced osteogenesis. These findings may begin to help inform researchers which MSC source may be optimal for IVD regeneration. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2445–2456, 2019     

Quantitative analysis of intervertebral disc degeneration using Q-space imaging in a rat model

The degree of intervertebral disc (IVD) degeneration is qualitatively evaluated on T2-weighted imaging (T2WI). However, it is difficult to assess subtle changes in IVD degeneration using T2WI. Q-space imaging (QSI) is a quantitative diffusion-weighted imaging modality used to detect subtle changes in microenvironments. This study aimed to evaluate whether QSI can detect the inhibitory effects of the antioxidant N-acetylcysteine (NAC) in IVD degeneration. We classified female Wistar rats into control, puncture, and NAC groups (n = 5 per group). In the puncture and NAC groups, IVDs were punctured using a needle. The antioxidant NAC, which suppresses the progression of IVD degeneration, was orally administered in the NAC group 1 week prior to puncture. The progression and inhibitory effect of NAC in IVD degeneration were assessed using magnetic resonance imaging (MRI): IVD height, T2 mapping, apparent diffusion coefficient (ADC), and QSI. MRI was performed using a 7-Tesla system with a conventional probe (20 IVDs in each group). QSI parameters that were assessed included Kurtosis, the probability at zero displacement (ZDP), and full width at half maximum (FWHM). IVD degeneration by puncture was confirmed by histology, IVD height, T2 mapping, ADC, and all QSI parameters (P < .001); however, the inhibitory effect of NAC was confirmed only by QSI parameters (Kurtosis and ZDP: both P < .001; FWHM: P < .01). Kurtosis had the largest effect size (Kurtosis: 1.13, ZDP: 1.06, and FWHM: 1.02) when puncture and NAC groups were compared. QSI has a higher sensitivity than conventional quantitative methods for detecting the progressive change and inhibitory effect of NAC in IVD degeneration.     

Contrast‐enhanced μCT of the intervertebral disc: A comparison of anionic and cationic contrast agents for biochemical and morphological characterization

The objective of this study was to quantify and compare the contrast‐enhancing properties of the anionic contrast agent ioxaglate/Hexabrix, and cationic contrast agent CA⁴⁺ for biochemical and morphological characterization of the intervertebral disc (IVD) via μCT. Optimal contrast agent concentrations were determined by incubating rat lumbar IVDs in dilutions of Hexabrix‐320 (20%, 30%, 40%, and 50%) and CA⁴⁺ (10, 20, 30, and 40 mg I/ml). μCT imaging was performed at 70 kVp, 114 μA, and 250 ms integration time, 12 μm voxel size. The kinetics of contrast enhancement were quantified with cumulative incubations for 0.5, 1, 2, 12, 16, 20, and 24 h using both agents. Agreement in morphological quantification was assessed via serial scans of the same IVDs. Correlation of attenuation to glycosaminoglycan (GAG) content was determined by enzymatic digestion of IVDs, subsequent μCT imaging, and GAG quantification via dimethylmethylene blue assay. Forty percent Hexabrix and 30 mg I/ml CA⁴⁺ were chosen as optimal concentrations. Hexabrix enabled greater delineation of the IVD from surrounding tissues, and CA⁴⁺ had the lowest uptake in surrounding soft tissue. Twenty‐four hour incubation was sufficient for >99% equilibration of both agents. A high level of agreement was observed in the quantification of IVD volume (ICC = 0.951, r = 0.997) and height (ICC = 0.947, r = 0.991). Both agents exhibited strong linear correlations between μCT attenuation and GAG content (Hexabrix: r = −0.940; CA⁴⁺: r = 0.887). Both agents enable biochemical and morphological quantification of the IVD via contrast‐enhanced μCT and are effective tools for preclinical characterization. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1067–1075, 2017.

     

Cervical and thoracic intervertebral disc hydration increases with recumbency: a study in 101 healthy volunteers

Background Context

Variation in the water content and the size of lumbar intervertebral discs (IVDs) is known to occur because of recumbency and has been associated with lumbar IVD herniation risk through the impact of IVD hydration on tissue mechanical properties. It is not clear if similar changes in cervical or thoracic IVDs occur with recumbency.

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.

     

The presence of extracellular matrix degrading metalloproteinases during fetal development of the intervertebral disc

Matrix metalloproteinases (MMPs) regulate connective tissue architecture and cell migration through extracellular matrix (ECM) degradation and are associated with both physiological and pathological processes. Although they are known to play a role in skeletal development, little is known about the role of MMPs in intervertebral disc (IVD) development. Sixteen fetal human lumbar spine segments, obtained at autopsy, were compared with five normal, non-fetal L4–L5 IVDs. Intensity and/or localization of immunohistochemical staining for MMP-1, -2, -3 and -14 were evaluated by three independent observers. MMP-2 production and activation was quantified by gelatin zymography. MMP-1 and -14 were abundantly present in the nucleus pulposus (NP) and notochordal (NC) cells of the fetal IVDs. In non-fetal IVDs, MMP-1 and -14 staining was significantly less intense (p = 0.001 and p < 0.001, respectively). MMP-3 was found in almost the entire IVD with no significant difference from non-fetal IVDs. MMP-2 staining in the NC and NP cells of the fetal IVD was moderate, but weak in the non-fetal IVD. Gelatin zymography showed a negative correlation of age with MMP-2 activity (p < 0.001). MMP-14 immunostaining correlated positively with MMP-2 activity (p = 0.001). For the first time, the presence of MMP-1, -2, -3 and -14 in the fetal human IVD is shown and the high levels of MMP-1, -2 and -14 suggest a role in the development of the IVD. In particular, the gradual decrease in MMP-2 activation during gestation pinpoints this enzyme as key player in fetal development, possibly through activation by MMP-1 and -14.     

Attenuation of aortic calcification with lanthanum carbonate versus calcium-based phosphate binders in haemodialysis: A pilot randomized controlled trial

Background: Vascular calcification (VC) contributes to cardiovascular disease in haemodialysis (HD) patients. Few controlled studies have addressed interventions to reduce VC but non‐calcium‐based phosphate binders may be beneficial. No published randomized study to date has assessed the effect of lanthanum carbonate (LC) on VC progression. Methods: We conducted a pilot randomized controlled trial to determine the effect of LC on VC. Forty‐five HD patients were randomized to either LC or calcium carbonate (CC). Primary outcome was change in aortic VC after 18 months. Secondary outcomes included superficial femoral artery (SFA) VC, bone mineral density (BMD) of lumbar spine and serum markers of mineral metabolism. At baseline, 6 and 18 month computed tomography was performed to measure VC and BMD. A random effect linear regression model was performed to assess differences. Results: Thirty patients completed the study (17 LC, 13 CC); baseline median age 58 years, 38% diabetic, 64% male. Ninety‐three per cent had aortic VC at commencement and 87% showed progression. At 18 months, there was significantly less aortic VC progression with LC than CC (adjusted difference ?98.1 (?149.4, ?46.8) Hounsfield units (HU), P < 0.001). There was also a non‐significant reduction with LC in left SFA VC (?25.8 (?67.7, 16.1) HU, P = 0.2) and right SFA VC (?35.9 (?77.8, 5.9) HU, P = 0.09). There was no difference in lumbar spine BMD and serum phosphate, calcium and parathyroid hormone levels between groups. Limitations to the study include small sample size and loss to follow up. Conclusions: Lanthanum carbonate was associated with reduced progression of aortic calcification compared with CC in HD patients over 18 months.     

Estrogen receptor expression in lumbar intervertebral disc of the elderly: Gender- and degeneration degree-related variations

ObjectivesSexual dimorphism does occur in intervertebral disc (IVD) degeneration. The involvement of estrogen on IVD health has been well reported in recent years. The estrogen receptors (ER) are the main mediators of estrogen action. ER might play specific roles in the sexual variations of the IVD degeneration.MethodsThirty-six elderly patients with lumbar disc degeneration were selected and graded using Pfirrmann's system based on MRI images. Differences of ERα and ERβ immunoreactivity staining in nucleus pulposus of each sex and degeneration degree were recorded and compared.ResultsBoth cytoplasmic and nuclear staining of ERα and ERβ immunoreactivity were observed in the nucleus pulposus cells. ERα and ERβ expression significantly decreased along with the aggravation of IVD degeneration both in males and females. Expression of ERα and ERβ protein in nucleus pulposus of males was significantly higher than that of females.ConclusionsGender-specific expression of ER might play a part in sexual dimorphism of IVD degeneration. Gender and degeneration condition differences should be taken into account when the effects of estrogen on IVD metabolism are studied further.     

Surgical pinealectomy accelerates intervertebral disc degeneration process in chicken

Despite the importance of intervertebral disc (IVD) degeneration both in research and clinical practice, the underlying biological mechanism of this phenomenon remains obscure. The current study investigated the effects of neonatal pinealectomy on the development of IVD degeneration process in chicken. Thirty chicks (3 days of age) were divided into two equal groups: unoperated controls (Group X) and pinealectomized chicks (Group Y). Pinealectomies were performed at the age of 3 days. At the age of 8 weeks, magnetic resonance imaging examination of one animal in each experimental group was taken. At the end of the study, serum melatonin level was determined by using ELISA method and histopathological or biochemical examination of specimens from all subjects was done. The results of biochemical analyses were compared using Mann–Whitney U test, whereas The Chi-square test was adopted for the histological findings. In this study, the serum melatonin levels in Group Y were significantly lower than those in Group X (P < 0.001). Similarly, scoliosis was developed in 14 out of 15 (93%) in Group Y. Hydroxyproline content of IVD tissue was high in Group Y compared with the values in Group X, although there was no significant difference. Histologically, an appearance of normal IVD was observed in Group X, while the presence of a degenerated IVD was observed in Group Y. From the results of the current study, it is evident that surgical pinealectomy in new-hatched Hybro Broiler chicks has a significant effect on serum melatonin level as well as on the development of IVD degeneration and spinal malformation. In the light of these results from present animal study, melatonin may play a role in the development of IVD degeneration in human beings, but this suggestion need to be validated in the human setting.     

Evaluation of age-related changes in lumbar facet joints using T2 mapping

BackgroundThe purpose in this study is to investigate the T2 value of lumbar facet joint (FJ) in subjects without lumbar spinal disorders, age from 20s to 70s, using T2 mapping, and to evaluate the correlation between age and T2 value. And also, we investigated the T2 value of lumbar intervertebral disc (IVD) in the same way as FJ, and evaluated the correlation between the T2 value of FJ and that of IVD.MethodsWe investigated 60 volunteers (30 male, 30 female), who were recruited from six age groups, 20s–70s (10 subjects in each decade; 5 male, 5 female). We measured the T2 values of FJ at the L4/5 level in axial image and those of IVD (nucleus pulposus; NP, anterior and posterior annulus fibrosus; AAF and PAF) at the L4/5 level in midline sagittal image. We investigated the correlation between age and T2 value of FJ, and the correlation between the T2 value of FJ and that of IVD.ResultsThere was a strong positive correlation between age and T2 value of FJ (r = 0.717). Age and T2 values of IVD were negatively correlated (NP; r = −0.728, AAF; r = −0.696, PAF; r = −0.580). There was a negative correlation between T2 value of FJ and that of IVD (NP; r = −0.575, AAF; r = −0.617, PAF; r = −0.492).ConclusionsT2 value of FJ was significantly increased as age rose. Our results suggest that T2 mapping could detect the degenerative changes of FJ related to aging even in subjects without lumbar spinal disorders. The results of this study will be the reference data of FJ T2 value in order to evaluate the relationship between low back pain and FJ using T2 mapping.     

Response to tumor necrosis factor‐α mediated inflammation involving activation of prostaglandin E2 and Wnt signaling in nucleus pulposus cells

The cyclooxygenase 2 (COX‐2) product, prostaglandin E₂ (PGE₂), acts through a family of G protein‐coupled receptors designated E‐prostanoid (EP) receptors that mediate intracellular signaling by multiple pathways. However, it is not known whether crosstalk between tumor necrosis factor‐α(TNF‐α)–PGE₂‐mediated signaling and Wnt signaling plays a role in the regulation of intervertebral disc (IVD) cells. In this study, we investigated the relationship between TNF‐α–PGE₂ signaling and Wnt signaling in IVD cells. TNF‐α increased the expression of COX‐2 in IVD cells. The EP receptors EP1, EP3, and EP4 were expressed in IVD cells, and TNF‐α significantly increased PGE₂ production. Stimulation with TNF‐α also upregulated EP3 and EP4 mRNA and protein expression in IVD cells. The inductive effect of the EP3 and EP4 receptors on Topflash promoter activity was confirmed through gain‐ and loss‐of‐function studies using selective EP agonists and antagonists. PGE₂ treatment activated Wnt–β‐catenin signaling through activation of EP3. We conclude that TNF‐α‐induced COX‐2 and PGE₂ stimulate Wnt signaling and activate Wnt target genes. Suppression of the EP3 receptor via TNF‐α–PGE₂ signaling seems to suppress IVD degeneration by controlling the activation of Wnt signaling. These findings may help identify the underlying mechanism and role of Wnt signaling in IVD degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1756–1768, 2015.     

Correlation of radiographic and MRI parameters to morphological and biochemical assessment of intervertebral disc degeneration

Degenerative disc disease (DDD) is a common finding in MRI scans and X-rays. However, their correlation to morphological and biochemical changes is not well established. In this study, radiological and MRI parameters of DDD were assessed and compared with morphological and biochemical findings of disc degeneration. Thirty-nine human lumbar discs (L1–S1), age 19–86 years, were harvested from eight cadavers. Within 48 h postmortem, MRIs in various spin-echo sequences and biplanar radiographs of intact spines were obtained. Individual discs with endplates were then sectioned in the mid-sagittal plane and graded according to the morphological appearance. Samples from the nucleus of each disc were harvested for biochemical analysis including water and proteoglycan contents. On MRIs, T2-signal intensity, Modic changes, disc extension beyond the interspace (DEBIT), nucleus pulposus shape, annular tears, osteophytes and endplate integrity were graded. On radiographs, an independent observer classified the parameters disc height, endplate sclerosis, osteophytes, Schmorls nodes, intradiscal calcifications and endplate shape. General linear-regression models were used for statistical analysis. Backward elimination with a 10% significance cut-off level was used to identify the most significant parameters, which then were summed to create composite scores for radiography, MRI and the combination of both methods. The grading was performed by three observers, and a reliability analysis using Cronbachs alpha model was used to control interobserver agreement. The three radiographic parameters height-loss, osteophytes and intradiscal calcifications correlated significantly with the morphological degree of degeneration (p<0.001, R²=642). Significant differences of even one morphological grade could also be differentiated in the composite radiological score (p<0.05), except at the extremes between grades 1 and 2 and grades 4 and 5. All MRI parameters correlated significantly with the morphological grade (p<0.05); however Modic changes, T2-intensity and osteophytes accounted for 83% of the variation in the data. T2-signal intensity correlated significantly with H₂O and proteoglycan content (p<0.001), and was best for detecting highly degenerated discs. Regression showed that the combined score was better correlated with the morphological grade (p<0.001, R² =775) than either the composite radiographic (p<0.001, R² =642) or composite MRI (p<0.001, R² =696) alone. Based on the combined score, a backwards elimination of the regression was performed, in which the parameters Modic changes, and T2-intensity loss (MRI) as well as calcifications (X-ray) accounted for 87% of the variability. The interobserver validation showed a high correlation for all three scores (Cronbachs alpha values ranging from 0.95 to 0.97). Conclusion: selective imaging parameters and a newly created scoring scheme were found to correlate with disc degeneration as determined in a morphological manner. Surprisingly, radiographic parameters were able to distinguish different stages of degeneration, whereas MRI could only detect advanced stages of disc degeneration. We conclude that X-rays may remain a cost-effective, non-invasive in vivo-grading method to detect early disc degeneration, and, combined with MRI, correlate best with morphological and biochemical assessment of disc degeneration.     

Role of SHOX2 in the development of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is the most common cause of low back pain, which affect 80% of the population during their lives, with heavy economic burden. Many factors have been demonstrated to participate in IVD degeneration. In this study, we investigated the role of short stature homeobox 2 (SHOX2) in the development of IVD degeneration. First, we detected the expression of SHOX2 in different stages of human IVD degeneration; then explored the role of SHOX2 on nucleus pulposus (NP) cells proliferation and apoptosis, finally we evaluated the effect of SHOX2 on the production of extracellular matrix in NP cells. Results showed that the expression of SHOX2 is mainly in NP compared with AF tissues, its expression decreased with the severity of human IVD degeneration. TNF‐α treatment led to dose‐ and time‐dependent decrease in SHOX2 mRNA, protein expression and promoter activity in NP cells. The silencing of SHOX2 inhibited NP cells proliferation and induced NP cells apoptosis. Finally, SHOX2 silencing led to decreased aggrecan and collagen II expression, along with increased ECM degrading enzymes MMP3 and ADAMTS‐5 in NP cells. In summary, our results indicated that SHOX2 plays an important role in the process of IVD degeneration, and might be a protective factor for IVD degeneration. Further studies are required to confirm its exact role, and clarify the mechanism. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1047–1057, 2017.

     

Intervertebral disc degeneration relates to biomechanical changes of spinal ligaments

BACKGROUND CONTEXTThe ligamentum flavum (LF), the inter- and supraspinous ligament (ISL&SSL) and the intertransverse ligament (ITL) are relevant spinal structures for segmental stability. The biomechanical effect of degeneration and aging on their biomechanical properties remains largely unknown.PURPOSEThe aim of this study was to assess the material properties of the ITL, ISL&SSL and LF and to correlate parameters of biomechanical function with LF-thickness, intervertebral disc (IVD) degeneration and age.STUDY DESIGNBiomechanical cadaveric study.METHODSMRI- and CT-scans of 50 human lumbar segments (Th12-L5) were used to assess the ISL (acc. to Keorochana), the grade of IVD degeneration (acc. to Pfirrmann) and to quantify LF-thickness. The ITL, ISL&SSL and LF were resected in the neutral position of the spinal segment with a specifically developed method to conserve initial strain. Ramp to failure testing was performed (0.5 mm/s) to record initial tension, slack length, stiffness and ultimate strength. The relationship between the biomechanical characteristics and age and radiological parameters were analyzed. There are no study-specific conflicts of interest and no external funding was received for this study.RESULTSWith aging, a significant reduction in initial tension (r=-0.5, p<.01) and ultimate strength (r=-0.41, p<.01) of the LF was observed, while the effect on LF-stiffness and the characteristics of the other ligaments was non-significant. IVD-degeneration was correlated with a significant reduction in stiffness (r=-0.47, p=.001; r=-0.36, p=.01) and ultimate strength (r=-0.3, p=.04; r=-0.36, p=.01) of the LF and ISL&SSL respectively and a significant reduction in initial tension (r=-0.4, p<.01) of the LF. For the ITL, no significant correlation was observed. Comparing Pfirrman 2 to 5, this reduction was 40% to 80% for stiffness 60% to 70% for ultimate strength and 88% for initial tension of the LF. ISL&SSL-stiffness between Kerorochana grade A and D differed significantly (p=.03), while all other comparisons were non-significant (p>.05). LF-thickness did not correlate with the biomechanical properties of the LF (p>.05).CONCLUSIONSAging is primarily related to biomechanical changes to the LF. IVD-degeneration is related to a relevant reduction in stiffness and ultimate strength of the LF and ISL&SSL, with a similar trend for the ITL. The ISL-specific Keorochana grading system provides only minimal biomechanical information and LF-thickness does not provide biomechanical information.CLINICAL SIGNIFICANCEPatient age and the degenerative state of the IVD can be used to evaluate the biomechanical characteristics of the dorsal spinal ligaments, which can be helpful in selecting the optimal surgical procedure (e.g. in decompression surgery) for a specific situation.     

Accumulated Spinal Axial Biomechanical Loading Induces Degeneration in Intervertebral Disc of Mice Lumbar Spine

Objective

To investigate the effect of accumulated spinal axial biomechanical loading on mice lumbar disc and the feasibility of applying this method to establish a mice intervertebral disc degeneration model using a custom‐made hot plate cage. In previous studies, we observed that the motion pattern of mice was greatly similar to that of humans when they were standing and jumping on their lower limbs. There is little data to demonstrate whether or not accumulated spinal axial biomechanical loading could induce intervertebral disc degeneration in vivo.

Methods

Twenty‐four 0‐week‐old mice were randomly divided into model 1‐month and 3‐month groups, and control 1‐month and 3‐month groups (n = 6 per group). The model groups was transferred into the custom‐made hot plate cage three times per day for modeling. The control group was kept in a regular cage. The intervertebral disc samples of the L₃–L₅ were harvested for histologic, molecular, and immunohistochemical studies after modeling for 1 and 3 months.

Results

Accumulated spinal axial biomechanical loading affects the histologic, molecular, and immunohistochemical changes of mice L_3–L₅ intervertebral discs. Decreased height of disc and endplate, fissures of annulus fibrosus, and ossification of cartilage endplate were found in morphological studies. Immunohistochemical studies of the protein level showed a similar expression of type II collagen at 1 month, but a slightly decreased expression at 3 months, and an increased expression level of type X collagen and matrix metalloproteinase 13 (MMP13). Molecular studies showed that ColIIa1 and aggrecan mRNA expression levels were slightly increased at 1 month (P > 0.05), but then decreased slightly (P > 0.05). ColXa1, ADAMTS‐5, and MMP‐13 expression levels werer increased both at 1 and 3 months (P < 0.05). In addition, increased expression of Runx2 was observed.

Conclusion

Accumulated spinal axial loading provided by a custom‐made hot plate accelerated mice lumbar disc and especially endplate degeneration. However, this method requires further development to establish a lumbar disc degeneration model.     

Inhibiting nerve growth factor or its receptors downregulates calcitonin gene‐related peptide expression in rat lumbar dorsal root ganglia innervating injured intervertebral discs

Nerve growth factor (NGF) and its dual structurally unrelated receptors, tropomyosin‐related kinase A (TrkA) or p75 neurotrophin receptor (p75^NTR), cause the pathogenesis of discogenic pain. To investigate the sensory innervation of injured rat lumbar intervertebral disc (IVD), we examined the expression of neuropeptides such as calcitonin gene‐related peptide (CGRP) at dorsal root ganglia (DRG) by inhibiting NGF or its dual receptors. Sprague–Dawley rats with multiply punctured L5–L6 IVD were used. Six experimental groups were prepared: naïve, sham control, and four agent‐treated groups with punctured IVD (vehicle, anti‐NGF antibody, anti‐TrkA antibody, and anti‐p75^NTR antibody). Retrograde neurotracer Fluoro‐Gold (FG) was applied together except for the naïve group. Their lumbar DRG were harvested and immunolabeled for CGRP. FG‐labeled DRG neurons were most prevalent at L1 and L2 DRG, and the proportion of FG‐labeled CGRP‐immunoreactive DRG neurons in the vehicle group was significantly elevated (p < 0.05) compared with the sham group, while those of antibody‐treated groups, especially in the anti‐p75^NTR group, significantly decreased compared with the vehicle group (p < 0.05). Direct intradiscal application of antibody to NGF or its receptors suppressed CGRP expression, and p75^NTR antagonism induced the most profound suppression. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1614–1620, 2010