Effect of hyperglycemia on apoptosis of notochordal cells and intervertebral disc degeneration in diabetic rats

Notochordal cells: A potential therapeutic option for intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a prevalent musculoskeletal degenerative disorder worldwide, and ~40% of chronic low back pain cases are associated with IDD. Although the pathogenesis of IDD remains unclear, the reduction in nucleus pulposus cells (NPCs) and degradation of the extracellular matrix (ECM) are critical factors contributing to IDD. Notochordal cells (NCs), derived from the notochord, which rapidly degrades after birth and is eventually replaced by NPCs, play a crucial role in maintaining ECM homeostasis and preventing NPCs apoptosis. Current treatments for IDD only provide symptomatic relief, while lacking the ability to inhibit or reverse its progression. However, NCs and their secretions possess anti-inflammatory properties and promote NPCs proliferation, leading to ECM formation. Therefore, in recent years, NCs therapy targeting the underlying cause of IDD has emerged as a novel treatment strategy. This article provides a comprehensive review of the latest research progress on NCs for IDD, covering their biological characteristics, specific markers, possible mechanisms involved in IDD and therapeutic effects. It also highlights significant future directions in this field to facilitate further exploration of the pathogenesis of IDD and the development of new therapies based on NCs strategies.

A systematic review and meta-analysis of risk factors for reoperation after degenerative lumbar spondylolisthesis surgery

BACKGROUND

Considering the high reoperation rate in degenerative lumbar spondylolisthesis (DLS) patients undergoing lumbar surgeries and controversial results on the risk factors for the reoperation, we performed a systematic review and meta-analysis to explore the reoperation rate and risk factors for the reoperation in DLS patients undergoing lumbar surgeries.

METHODS

Literature search was conducted from inception to October 28, 2022 in Pubmed, Embase, Cochrane Library, and Web of Science. Odds ratio (OR) was used as the effect index for the categorical data, and effect size was expressed as 95% confidence interval (CI). Heterogeneity test was performed for each outcome effect size, and subgroup analysis was performed based on study design, patients, surgery types, follow-up time, and quality of studies to explore the source of heterogeneity. Results of all outcomes were examined by sensitivity analysis. Publication bias was assessed using Begg test, and adjusted using trim-and-fill analysis.

RESULTS

A total of 39 cohort studies (27 retrospective cohort studies and 12 prospective cohort studies) were finally included in this systematic review and meta-analysis. The overall results showed a 10% (95%CI: 8%-12%) of reoperation rate in DLS patients undergoing lumbar surgeries. In surgery types subgroup, the reoperation rate was 11% (95%CI: 9%-13%) for decompression, 10% (95%CI: 7%-12%) for fusion, and 9% (95%CI: 5%-13%) for decompression and fusion. An increased risk of reoperation was found in patients with obesity (OR = 1.91, 95%CI: 1.04-3.51), diabetes (OR = 2.01, 95%CI: 1.43-2.82), and smoking (OR = 1.51, 95%CI: 1.23-1.84).

CONCLUSIONS

We found a 10% of reoperation rate in DLS patients after lumbar surgeries. Obesity, diabetes, and smoking were risk factors for the reoperation.

Addition of Resolvins D1 or E1 to Collagen Membranes Mitigates Their Resorption in Diabetic Rats

Uncontrolled diabetes is characterized by aberrant inflammatory reactions and increased collagenolysis. We have reported that it accelerates the degradation of implanted collagen membranes (CM), thus compromising their function in regenerative procedures. In recent years, a group of physiological anti-inflammatory agents called specialized pro-resolving lipid mediators (SPMs) have been tested as a treatment for various inflammatory conditions, either systemically or locally, via medical devices. Yet, no study has tested their effect on the fate of the biodegradable material itself. Here, we measured the in vitro release over time of 100 or 800 ng resolvin D1 (RvD1) incorporated into CM discs. In vivo, diabetes was induced in rats with streptozotocin, while buffer-injected (normoglycemic) rats served as controls. Resolvins (100 or 800 ng of RvD1 or RvE1) were added to biotin-labeled CM discs, which were implanted sub-periosteally over the calvaria of rats. Membrane thickness, density, and uniformity were determined by quantitative histology after 3 weeks. In vitro, significant amounts of RvD1 were released over 1-8 days, depending on the amount loaded. In vivo, CMs from diabetic animals were thinner, more porous, and more variable in thickness and density. The addition of RvD1 or RvE1 improved their regularity, increased their density, and reduced their invasion by the host tissue significantly. We conclude that addition of resolvins to biodegradable medical devices can protect them from excessive degradation in systemic conditions characterized by high degree of collagenolysis.

Inhibitory Effect of Insulin Treatment on Apoptosis of Intervertebral Disc Cells in a Streptozotocin-Induced Diabetic Rat Model

STUDY DESIGN

Experimental study using a streptozotocin (STZ)-induced diabetic rat model.

PURPOSE

This study aims to investigate whether insulin treatment could attenuate disc cell apoptosis and matrix degradation in a STZ-induced diabetic rat model.

OVERVIEW OF LITERATURE

Diabetes is a significant risk factor for disc degeneration due to excessive apoptosis of disc cells and matrix degradation. However, no studies were noted to demonstrate the inhibitory effect of insulin treatment on the apoptosis of disc cells and matrix degradation in diabetic patients.

METHODS

Rats were allocated randomly into one of three groups: control, STZ, and STZ-insulin. Diabetes was induced by a single intraperitoneal injection of STZ (65 mg/kg) in the STZ and STZ-insulin groups. The blood glucose level was consistently above 400 mg/ dL in the STZ and STZ-insulin groups 2 weeks after STZ injection. After 2 weeks of STZ injection, the STZ-insulin group was administered insulin treatment (1.5 unit/100 g) daily for up to 4 weeks. Blood glucose of the STZ-insulin rats significantly decreased to normal levels 4 weeks after insulin treatment. The rats were sacrificed 6 weeks after STZ injection, and disc cells and tissues were harvested to investigate the expression of apoptosis markers and matrix metalloproteinases (MMPs).

RESULTS

Fas and caspase-8, -9, and -3 expressions were significantly increased in the STZ group, along with increased expressions of MMP-2 and -3. On the contrary, insulin treatment significantly decreased the expressions of Fas, caspase-8, -9, and -3 as well as MMP-2 and -3 in the STZ-insulin group.

CONCLUSIONS

The results of the current study demonstrated that insulin treatment attenuates excessive apoptosis of disc cells and matrix degradation in the diabetic rat model. Accordingly, strict blood glucose control should be recommended to prevent disc degeneration in diabetic patients.

A systematic morphology study on the effect of high glucose on intervertebral disc endplate degeneration in mice

To explore the relationship between diabetes and intervertebral disc degeneration in mice and the associated underlying mechanism. Four-week-old male Kunming mice were used to model diabetes using a high-fat diet combined with streptozotocin injection. After 6 months, morphological and pathological changes in L4-L6 intervertebral discs were detected by magnetic resonance imaging, micro-CT and histological staining. Immunostaining of CD31, F4/80 and CD16/32 receptors was used to detect vascular invasion and inflammatory infiltration in endplates; the exact changes were then explored by the transmission electron microscopy. The nucleus pulposus of the control and the diabetic group had a clear boundary and regular shape without collapse, while endplate calcification and chondrocyte abnormality in the diabetic group were more obvious. Immunofluorescence confirmed that compared to control, expression levels of CD31 (vascular endothelial marker) and F4/80 (monocyte/macrophage marker) in the diabetic group were significantly increased (P < 0.05), with an elevated number of F4/80 (+)/CD16/32 (+) cells (P < 0.05). The morphology of endplates was observed by transmission electron microscopy, which showed monocytes/macrophage accumulation in the endplate of the diabetic group, accompanied by increased vascular density, collagen fiber distortion and chondrocyte abnormality. In a conclusion, diabetes promotes endplate degeneration with vascular invasion, monocyte/macrophage infiltration and inflammation in mice.

Type 2 diabetes mellitus, physical activity, and neuromusculoskeletal complications

Objectives

The objectives of the study were to investigate the neuromusculoskeletal complications of Type 2 diabetes mellitus (T2DM) and their associated factors, including the level of physical activity (PA) and clinicodemographic characteristics.

Materials and Methods

In this cross-sectional analysis, we included 370 participants diagnosed with T2DM for no <1 year who satisfied the inclusion and exclusion criteria. Demographic and clinical characteristics were noted and a thorough clinical examination was performed on all the participants. International PA Questionnaire-Short Form was used to evaluate the level of PA of the participants. The continuous data is presented as mean ± SD and the categorical data is presented as the number of participants (n) and percentage (%). A logistic regression model was used to investigate the predictors for the prevalence of the complications.

Results

The mean duration of T2DM was 7.32 ± 5.53 years and the mean hemoglobin A1C (HbA1c) level (%) was 8.16±1.67. A majority of the participants were having uncontrolled diabetes with an HbA1c level ≥7.5% (n = 190; 51.35%). The level of PA was low in a substantial proportion of the participants (n = 276; 74.59%). A total of 162 (43.78%) participants were diagnosed with neuromusculoskeletal complications. Low back pain was the most common complication and degenerative disk disease was the most common diagnosis overall. Longer duration of diabetes, poor glycemic control, and low PA were associated with the prevalence of neuromusculoskeletal complications (P < 0.05).

Conclusion

Neuromusculoskeletal complications of T2DM are common and can result in significant disability in this population. Low PA is very common among T2DM patients and an important contributor to the development of complications. Health-care providers should consider PA an integral component of the management protocol for T2DM patients.

Association between cardiovascular risk factors and degenerative disc disease of the thoracolumbar spine in the general population: results from the KORA MRI Study

BACKGROUND

Little is known about the associations between cardiovascular risk factors (CRF) and disc degeneration (DD).

PURPOSE

To evaluate the potential association between CRFs and intervertebral DD in a population-based sample.

METHODS

A total of 400 participants from the community-based KORA-study were assessed in terms of CRFs, specifically obesity, hypertension, diabetes, elevated LDL-c, low HDL-c, elevated triglycerides, smoking status, and alcohol consumption. The patients additionally underwent whole-body magnetic resonance imaging (MRI) using T2-weighted single-shot fast-spin-echo and T1 dual-echo gradient-echo Dixon pulse sequences. Thoracic and lumbar DD were assessed using the Pfirrmann score and for the presence of disc bulging/protrusion. Cross-sectional associations between CRFs and MR-based Pfirrmann score were then analyzed.

RESULTS

A total of 385 individuals (58.2% men; mean age 56.3 ± 9.2 years) were included. Prevalence of DD was 76.4%. Older age (β = 0.18; 95% CI 0.12-0.25; P < 0.001) and higher body mass index (BMI) (β = 0.19; 95% CI 0.06-0.30; P = 0.003) were significantly associated with DD of the thoracolumbar spine. Diabetes was significantly associated with DD at T7/8 (P = 0.029) and L3/4 (P = 0.017). Hypertension correlated significantly with DD in univariate analysis, but the association did not persist using multivariate analysis (β = 0.53; 95% CI -0.74 to 1.81; P = 0.41). None of the other CRFs (P ≥ 0.11) were associated with advanced DD. Disc bulging was independently associated with hypertension (β = 0.47; 95% CI 0.27-0.81; P = 0.01).

CONCLUSION

A significant independent association exists between age, BMI, and intervertebral DD. In contrast, there is no significant association between cardiovascular risk factors and DD. Providing strong evidence that the pathologic process undergirding DD is mechanical, rather than microvascular, in nature.

Systemic Risk Factors for Adult Spinal Deformity (ASD): A Retrospective Analysis of 48 Patients

Introduction: Adult spinal deformity (ASD) results in significant patient morbidity and burden to quality of life. The degree to which systemic risk factors and comorbidities that contribute to ASD affect specific spinopelvic parameters is not well-documented. We determine the extent to which preoperative risk factors may contribute to spinopelvic parameters associated with ASD.

Methods: Retrospective single-center study of 48 patients with ASD. Analysis of variance (ANOVA) linear regression analysis was performed to evaluate correlation between systemic comorbidities (obesity, arterial hypertension (HTN), hyperlipidemia (HLD), cardiomyopathy, diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD), and asthma) and the following radiographic parameters: pelvic incidence (PI), lumbar lordosis (LL), C7 sagittal vertical axis (C7SVA), and the T10-L2 sagittal cobb angle.

Results: A total of 48 patients were included with mean C7SVA of 79.6 mm (SD: 63, range: 43-254), mean LL of 32.9° (SD: 15.9, range: -14 to 78), T10-L2 sagittal cobb angle of 3° (SD: 12.7, range: -24 to 30), and PI was 49° (SD: 10.7, range: 21 to 77). Only DM correlated with sagittal imbalance with high C7SVA and PI-LL mismatch. The beta coefficient for DM and preoperative C7SVA was 0.49, t=3.16, p=0.003, preoperative PI-LL mismatch standardized beta coefficient was -0.4, t=-2.38, p=0.022, and preoperative T10-L2 sagittal cobb standard beta coefficient was -0.07, t=-0.46, p=0.645. No significant correlations were found for asthma, COPD, HTN, HLD, or cardiomyopathy.

Conclusions: Diagnosis of DM was found to correlate with pathologic C7SVA and significant PI-LL mismatch associated with ASD. HTN, HLD, cardiomyopathy, obesity, and pulmonary disease did not correlate with radiographic findings of sagittal imbalance.

The Potential Role of Cytokines in Diabetic Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a major cause of low back pain. Diabetes mellitus is a chronic inflammatory disease that may cause or aggravate IVDD; however, the mechanism by which diabetes induce IVDD is currently unclear. Compared to non-diabetic individuals, diabetic patients have higher levels of plasma cytokines, especially TNF-α, IL-1β, IL-5, IL-6, IL-7, IL-10, and IL-18. Due to the crucial role of cytokines in the process of intervertebral disc degeneration, we hypothesized that elevation of these cytokines in plasma of diabetic patients may be involved in the process of diabetes-induced IVDD. In this review, changes in plasma cytokine levels in diabetic patients were summarized and the potential role of elevated cytokines in diabetes-induced IVDD was discussed. Results showed that some cytokines such as TNF-α and IL-1β may accelerate the development of IVDD, while others such as IL-10 is supposed to prevent its development. Apoptosis, senescence, and extracellular matrix metabolism were found to be regulated by these cytokines in IVDD. Further studies are required to validate the cytokines targeted strategy for diabetic IVDD therapy.

High glucose mediates the ChREBP/p300 transcriptional complex to activate proapoptotic genes Puma and BAX and contributes to intervertebral disc degeneration

Emerging evidence shows that obesity and type 2 diabetes (T2D) are associated with intervertebral disc degeneration (IDD). However, the underlying mechanisms are still obscure. Here, we found that serum glucose concentrations were significantly increased in T2D-IDD patients. Detection of molecular changes indicated that two glucose transporters (GLUTs), including GLUT1 and GLUT4, were hyperactivated in these IDD patients with obesity. Using a microarray assay to detect the dysregulated genes in IDD patients with obesity, we identified 33 differentially expressed genes and verified only two proapoptotic genes, including Puma (p53 upregulated modulator of apoptosis) and BAX (BCL2 associated X) responded to glucose. The mechanistic investigation revealed that carbohydrate-responsive element-binding protein (ChREBP) coupled with the histone acetyltransferase p300 to bind to the promoter of Puma and BAX genes and activated their expression in the condition of high glucose. The accumulation of Puma and BAX triggered mitochondrial dysfunction and caspase activation, resulting in apoptosis. Moreover, we found that glucose could accelerate the occurrence of IDD in a rat model. Interestingly, we administrated two GLUT inhibitors (BAY-876 and Fasentin) in rats injected glucose and found that these two inhibitors could reverse the defects of IDD by decreasing apoptosis. Our in vitro and in vivo data support a model in which high glucose activates the ChREBP/p300 transcriptional complex to bind to the promoters of Puma and BAX, causing apoptosis and IDD pathogenesis. Our discovery suggests that the control of glucose absorption in T2D-IDD patients may decrease the outcome of IDD.

Cycloastragenol and Astragaloside IV activate telomerase and protect nucleus pulposus cells against high glucose-induced senescence and apoptosis

In diabetes-induced intervertebral disc degeneration (Db-IVDD), senescence and apoptosis of nucleus pulposus cells (NPCs) are major contributing factors. Telomere attrition and telomerase downregulation are some of the main reasons for senescence and eventual apoptosis. The derivatives of the Chinese herb Astragalus membranaceus, Cycloastragenol (CAG) and Astragaloside IV (AG-IV), are reportedly effective telomerase activators against telomere shortening; however, their effect in Db-IVDD have not been explored. The present study simultaneously investigated the regulation of these derivatives on senescence, apoptosis, telomeres and telomerase a model of high-glucose (HG)-induced stress using rat primary NPCs. The NPCs were stimulated with HG (50 mM) to evoke HG-induced stress, and the effects of CAG and AG-IV were observed on: i) The expression level of senescence marker p16; ii) β-Gal staining; iii) the expression levels of apoptosis markers cleaved-caspase 3 (c-C3), BAX and Bcl-2; iv) telomerase activation with telomerase reverse transcriptase (TERT) mRNA and protein expression, while telomere length was measured with reverse transcription-quantitative PCR. Cell proliferation was determined using the Cell Counting Kit-8 assay. Results demonstrated an upregulation in the expression levels of p16, c-C3 and BAX, and increased β-Gal staining; while the expression level of Bcl-2 was downregulated in a concentration-dependent manner. Pre-treatment of the NPCs with CAG and AG-IV downregulated the protein expression levels of p16, c-C3 and BAX, and decreased the percentage of β-Gal and FITC staining; while upregulating the Bcl-2 expression. These effects protected the cells from HG stress-induced senescence and apoptosis. HG also downregulated the expression profile of TERT and shortened the telomere length in a glucose concentration-dependent manner. While pretreatment with CAG and AG-IV upregulated TERT expression and ameliorated the telomere attrition. CAG and AG-IV also increased cell proliferation and improved cell morphology in HG conditions. Overall, these findings indicated that CAG and AG-IV suppressed HG stress-induced senescence and apoptosis, in addition to enhancing telomerase activation and lengthening of the Telomere. Therefore, CAG and AG-IV prolonged the replicative capability and longevity of the NPCs and they have the potential to be therapeutic agents in Db-IVDD.

Strong association of type 2 diabetes with degenerative lumbar spine disorders

Tantalizing connections between type 2 diabetes and degenerative lumbar spine disorders have become increasingly evident. However, the association of type 2 diabetes with degenerative lumbar spine disorders remains unclear. We sought to clarify the association between type 2 diabetes and lumbar spine disorders using nationwide data in Korea. Furthermore, we explored the association of diabetes with the prevalence of spinal procedures. The data in this study was obtained from Korean health claim database. Between 2016 and 2019, totals of 479,680 diabetes and 479,680 age- and sex-matched control subjects were enrolled. Patients with diabetes had more likely to have degenerative lumbar spine disorders and spinal procedures than controls. Using multivariate-adjusted analysis, patients with diabetes were at increased risk of being concomitantly affected by lumbar disc disorder [adjusted odds ratio 1.11 (95% confidence interval 1.10-1.12)], lumbar spondylotic radiculopathy [1.12 (1.11-1.13)], spondylolisthesis [1.05 (1.02-1.08)] and spinal stenosis [1.16 (1.15-1.18)], compared to controls. Furthermore, diabetic patients had an increased risk of undergoing lumbar spinal injection [1.13 (1.12-1.14)], laminectomy [1.19 (1.15-1.23)], and fusion surgery [1.35 (1.29-1.42)]. We demonstrated that type 2 diabetes was significantly associated with lumbar spine disorders and frequent spinal procedures. Our results suggest diabetes as a predisposing factor for lumbar spine disorders.

Mitochondrial quality control in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common and early-onset pathogenesis in the human lifespan that can increase the risk of low back pain. More clarification of the molecular mechanisms associated with the onset and progression of IDD is likely to help establish novel preventive and therapeutic strategies. Recently, mitochondria have been increasingly recognized as participants in regulating glycolytic metabolism, which has historically been regarded as the main metabolic pathway in intervertebral discs due to their avascular properties. Indeed, mitochondrial structural and functional disruption has been observed in degenerated nucleus pulposus (NP) cells and intervertebral discs. Multilevel and well-orchestrated strategies, namely, mitochondrial quality control (MQC), are involved in the maintenance of mitochondrial integrity, mitochondrial proteostasis, the mitochondrial antioxidant system, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Here, we address the key evidence and current knowledge of the role of mitochondrial function in the IDD process and consider how MQC strategies contribute to the protective and detrimental properties of mitochondria in NP cell function. The relevant potential therapeutic treatments targeting MQC for IDD intervention are also summarized. Further clarification of the functional and synergistic mechanisms among MQC mechanisms may provide useful clues for use in developing novel IDD treatments.

High-glucose environment accelerates annulus fibrosus cell apoptosis by regulating endoplasmic reticulum stress

Diabetes mellitus (DM) is an important risk factor of intervertebral disc degeneration. However, how DM affects annulus fibrosus (AF) biology remains unclear. The present study was aimed to investigate the effects and mechanism of high glucose on AF cell biology. Rat AF cells were cultured in baseline medium and culture medium with 0.2 M glucose. The inhibitor 4-PBA was added along with the high glucose culture medium to study the role of endoplasmic reticulum (ER) stress in this process. Compared with the control cells, high glucose significantly increased cell apoptosis ratio and caspase-3/9 activity, up-regulated mRNA/protein expression of Bax and caspase-3/cleaved caspase-3, but down-regulated mRNA/protein expression of Bcl-2. Moreover, high glucose increased mRNA and protein expression of CHOP, ATF-6 and GRP78. However, once ER stress was inhibited by the inhibitor 4-PBA in the high glucose group, cell apoptosis ratio and caspase-3/9 activity were decreased, mRNA/protein expression of Bax and caspase-3/cleaved caspase-3 was down-regulated, but mRNA/protein expression of Bcl-2 was up-regulated. In conclusion, high glucose condition can promote AF cell apoptosis through inducing ER stress. The present study helps us understand the mechanism of disc degeneration in DM patients.

Associations between Health-Related Physical Fitness and Cardiovascular Disease Risk Factors in Overweight and Obese University Staff

PURPOSE

This cross-sectional study examined the associations between health-related physical fitness (HPF) and cardiovascular disease (CVD) risk factors in overweight and obese university staff.

METHODS

A total of 340 university staff (109 women, mean age 43.1 ± 9.7 years) with overweight (n = 284) and obesity (n = 56) were included. The HPF indicators included skeletal muscle mass index (SMI), body fat percentage (BFP), grip strength (GS), sit-and-reach test (SRT), and vital capacity index (VCI). CVD risk factors were measured, including uric acid (UA), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose (GLU).

RESULTS

BFP, SMI, and GS were positively associated with UA level (β = 0.239, β = 0.159, β = 0.139, p < 0.05). BFP was positively associated with TG and TG/HDL-C levels (β = 0.421, β = 0.259, p < 0.05). GS was positively associated with HDL-C level (β = 0.244, p < 0.05). SRT was negatively associated with GLU level (β = -0.130, p < 0.05).

CONCLUSIONS

In overweight and obese university staff, body composition, muscle strength, and flexibility were associated with CVD risk factors. An HPF test may be a practical nonmedical method to assess CVD risk.

The Long-term Reoperation Rate Following Surgery for Lumbar Stenosis: A Nationwide Sample Cohort Study With a 10-year Follow-up

STUDY DESIGN

Retrospective cohort study of a nationwide sample database.

OBJECTIVE

The objective of the present study was to compare the long-term incidence of reoperation for lumbar spinal stenosis (LSS) after anterior fusion, posterior fusion, and decompression.

SUMMARY OF BACKGROUND DATA

Surgical treatment for LSS can be largely divided into 2 categories: decompression only and decompression with fusion. A previous nationwide study reported that fusion surgery was performed in 10% of patients with LSS, and the 10-year reoperation rate was approximately 17%. However, with the development of surgical techniques and changes in surgical trends, these results should be reassessed.

METHODS

The National Health Insurance Service-National Sample Cohort of the Republic of Korea was utilized to establish a cohort of adult patients (N = 1400) who first underwent surgery for LSS during 2005 to 2007. Patients were followed for 8 to 10 years. Considering death before reoperation as a competing event, reoperation hazards were compared among surgical techniques using a Fine and Gray regression model after adjustment for sex, age, diabetes, osteoporosis, Charlson comorbidity index, severity of disability, type of medical coverage, and type of hospital.

RESULTS

The overall cumulative incidence of reoperation was 6.2% at 2 years, 10.8% at 5 years, and 18.4% at 10 years. The cumulative incidence of reoperation was 20.6%, 12.6%, and 18.6% after anterior fusion, posterior fusion, and decompression, respectively, at 10 years postoperatively (P = 0.44). The first surgical technique did not affect the reoperation type (P = 0.27). Decompression was selected as the surgical technique for reoperation in 83.5% of patients after decompression, in 72.7% of patients after anterior fusion, and in 64.3% of patients after posterior fusion.

CONCLUSION

The initial surgical technique did not affect reoperation during the 10-year follow-up period. Decompression was the most commonly used technique for reoperation.

LEVEL OF EVIDENCE

4.

Effects of type 1 diabetes mellitus on lumbar disc degeneration: a retrospective study of 118 patients

BACKGROUND

The study aimed to investigate the correlation between type 1 diabetes (T1D) and lumbar disc degeneration (LDD).

METHODS

A retrospective analysis of 118 patients with T1D recruited from January 2014 to March 2019 was performed, and multivariate logistic regression was used to analyse the incidence of T1D; the age, sex, and body mass index (BMI) of the patients; the disease duration and the glycosylated haemoglobin and venous blood glucose levels. All patients who suffered low back pain were assessed by MRI using the Pfirrmann grading system.

RESULTS

A total of 118 patients with an average age of 36.99 ± 17.01 (8-85 years) were reviewed. The mean hospitalization duration, venous glucose fluctuation range, glycated haemoglobin level, highest venous glucose level, venous glucose level, and disease course duration were 13.98 ± 10.16 days, 14.99 ± 5.87 mmol/L, 9.85 ± 2.52 mmol/L, 25.29 ± 7.92 mmol/L, 13.03 ± 5.75 mmol/L and 7.30 ± 8.41 years. The average Pfirrmann scores of the different discs were 2.20 ± 0.62 (L1-2), 2.35 ± 0.67 (L2-3), 2.90 ± 0.45 (L3-4), 4.20 ± 0.52 (L4-5) and 4.10 ± 0.72 (L5-S1). The patients with T1D showed severe disc degeneration. The male sex, glycosylated haemoglobin, venous glucose and venous glucose fluctuations were significantly associated with LDD (P < 0.05).

CONCLUSIONS

Glycosylated haemoglobin, the male, venous glucose and the venous glucose fluctuation range were risk factors for LDD.

Does Type II Diabetes Induce Early Senescence and Degeneration in Human Intervertebral Discs? A Tissue Biomarker Evaluation

Background

Diabetes mellitus is one of the leading causes of morbidity resulting in multi-organ dysfunction. Animal studies have shown that hyperglycemia results in stress-induced senescence through the p16-pRb pathway, thereby accelerating early disc degeneration. There is a paucity of literature on the effect of hyperglycemia in human intervertebral disc cells. We aimed to analyze the effect of diabetes mellitus in human intervertebral disc cells.

Methods

This is a prospective study done in patients with degenerative disc disease. Patients were categorized into a control group (no diabetes: 26 patients) and a study group (type 2 diabetes for > 3 years: 24 patients). All patients underwent either discectomy or transforaminal lumbar interbody fusion and the removed disc was transported to pathology department. Tissue was prepared and histopathological grading was done followed by immunohistochemistry studies using antibodies for MMP-1, p21, p16, and pRb.

Results

Samples from diabetic patients had severe (grade 2) degenerative changes compared with the control group (grade 1). Changes were more intense in the nucleus pulposus with increased cellularity and clustering of chondrocytes, and disorganization and loss of nuclear matrix. Immunohistochemical staining for MMP1, p16, and pRb was more intense (Q score = 4) whereas the staining for p21 was less intense (Q score = 1) in the diabetic group compared with the control group.

Conclusion

Our study demonstrates that type 2 diabetes mellitus accelerates stress-induced senescence in human intervertebral discs resulting in early disc degeneration. Also, the severity of disc degeneration is severe compared with the normal subjects.

Clinical Relevance

Hyperglycemia can affect the intervertebral discs similar to other organs and hence adequate control of blood glucose in diabetics can prevent the disc degeneration, which is the initiator of degeneration cascade in spine.

The role of estrogen in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main contributor to low back and radicular pain, which imposes heavy economic burdens on society. However, the etiology and mechanism of IVDD are complex and still not completely clear. In particular, the role of estrogen in IVDD has not received much attention in recent research, although estrogen plays a crucial role in the metabolic dysfunction of others musculoskeletal structures, such as bone, muscle, and tendon. In this review, we attempt to describe the role of estrogen in IVDD and to summarize the proposed mechanisms in vivo and in vitro, as well as, to outline several interesting questions in this field.

Marein protects human nucleus pulposus cells against high glucose-induced injury and extracellular matrix degradation at least partly by inhibition of ROS/NF-κB pathway

Intervertebral disc degeneration (IDD), a major cause of discogenic low back pain, is a musculoskeletal disorder involving the apoptosis of nucleus pulposus cells (NPCs) and extracellular matrix (ECM) degradation. Marein is a major active flavonoid ingredient extracted from the hypoglycemic plant Coreopsis tinctoria with several beneficial biological activities including anti-diabetic effects. Nevertheless, there are no reports concerning the effects of marein on IDD. Our study aimed to evaluate the effects of marein on high glucose (HG)-induced injury and ECM degradation in human NPCs (HNPCs). CCK-8 assay was applied to evaluate cell viability. Flow cytometry analysis, a cell death detection ELISA, and caspase-3 activity assay were used to assess apoptosis. The mRNA expression of ECM-related proteins matrix metalloproteinase (MMP)-3, MMP-13, Collagen II, and aggrecan were determined by qRT-PCR. The changes of the nuclear factor-kappa B (NF-κB) pathway were examined by western blot. Stimulation with HG significantly reduced cell viability and induced apoptosis in HNPCs. Moreover, HG exposure increased MMP-3 and MMP-13 expression and decreased Collagen II and aggrecan expression in HNPCs. Notably, marein effectively alleviated HG-induced viability reduction, apoptosis and ECM degradation in HNPCs. We also found that marein inhibited HG-induced ROS generation and NF-κB activation in HNPCs. Inhibition of NF-κB pathway reinforced HG-induced injury and ECM degradation in HNPCs. In summary, marein protected HNPCs against HG-induced injury and ECM degradation at least partly by inhibiting the ROS/NF-κB pathway.

Intervertebral disc degeneration: A focus on obesity and type 2 diabetes

Obesity (OB) and type 2 diabetes (T2D) are among the most prevalent metabolic diseases. They currently affect a substantial part of the world population and are characterized by several systemic co-morbidities, including cardiovascular diseases, stroke, cancer, liver steatosis, and musculoskeletal disorders, by increasing the risk of developing osteoarthritis and intervertebral disc degeneration (IVDD). IVDD is a chronic, progressive process whose main features are disc dehydration, loss of disc height, and changes of load distribution across the spine, resulting in disc structure disruption and leading to low back pain onset. Given the high prevalence of these metabolic disorders and their association with IVDD, several studies have been conducted in order to investigate the causative role of biological and biomechanical characteristics proper to these conditions in the development of IVDD. This review aims to analyse the role of OB and T2D on IVDD, in order to clarify the pathophysiological drivers of the degenerative process and to delineate possible targets to which appropriate treatments may be addressed in the near future.

The Role of Type I Diabetes in Intervertebral Disc Degeneration

STUDY DESIGN

An experimental laboratory study.

OBJECTIVE

To investigate the pathogenesis of intervertebral disc degeneration (IDD) in a murine model of type 1 diabetes mellitus (DM), namely nonobese diabetic (NOD) mouse.

SUMMARY OF BACKGROUND DATA

IDD is a leading contributor of low back pain, which represents one of the most disabling symptoms within the adult population. DM is a chronic metabolic disease currently affecting one in 10 adults in the United States. It is associated with an increased risk of developing IDD, but the underlying process remains poorly understood.

METHODS

Total disc glycosaminoglycan content, proteoglycan synthesis, aggrecan fragmentation, glucose transporter gene expression, and apoptosis were assessed in NOD mice and wild-type euglycemic control mice. Spinal structural and molecular changes were analyzed by micro-computed tomography, histological staining (Safranin-O and fast green), and quantitative immunofluorescence (anti-ADAMTS-4 and -5 antibodies).

RESULTS

Compared with euglycemic controls, NOD mice showed increased disc apoptosis and matrix aggrecan fragmentation. Disc glycosaminoglycan content and histological features of NOD mice did not significantly differ from those of euglycemic littermates.

CONCLUSION

These data demonstrate that DM may contribute to IDD by increasing aggrecan degradation and promoting cell apoptosis, which may represent early indicators of the involvement of DM in the pathogenesis of IDD.

LEVEL OF EVIDENCE

N/A.

High glucose promotes annulus fibrosus cell apoptosis through activating the JNK and p38 MAPK pathways

Diabetes mellitus (DM) is an important risk factor of intervertebral disc degeneration. A high glucose niche-mediated disc cell apoptosis is an implicate causative factor for the spine degenerative diseases related with DM. However, the effects of a high glucose niche on disc annulus fibrosus (AF) cell apoptosis and the potential signaling transduction pathway is unclear. The present study is to investigate the effects of high glucose on disc AF cell apoptosis and the role of two potential signaling pathways in this process. Rat AF cells were cultured in baseline medium or medium with different concentrations (0.1 and 0.2 M) of glucose for 3 days. Flow cytometry was used to assess the degree of apoptosis. Activity of caspase 3/9 was evaluated by chemical kit. Expression of pro-apoptotic and anti-apoptotic molecules was analyzed by real-time polymerase chain reaction and Western blot. In addition, activity of the C-Jun NH₂-terminal kinases (JNK) pathway and p38 mitogen-activated protein kinase (MAPK) pathway was evaluated by Western blot. Compared with the control group, high glucose culture increased cell apoptosis ratio and caspase-3/9 activity, up-regulated expression of bax, caspase-3, cleaved caspase-3 and cleaved PARP, and down-regulated expression of bcl-2 in a glucose concentration-dependent manner. Additionally, high glucose culture increased expression of the p-JNK and p-p38 MAPK in a concentration-dependent manner. Further results showed that inhibition of the JNK or p38 MAPK pathway attenuated the effects of high glucose on AF cell apoptosis. Together, high glucose promoted disc AF cell apoptosis through regulating the JNK pathway and p38 MAPK pathway in a glucose concentration-dependent manner.

Diabetes mellitus as a risk factor for intervertebral disc degeneration: a critical review

PURPOSE

To examine to what extent diabetes mellitus (DM) is implicated as a distinct mechanism in intervertebral disc degeneration (IVDD).

METHODS

The published clinical and laboratory data relevant to this matter are critically reviewed. A total of 12 clinical studies evaluate the association between DM and degenerative changes such as IVDD, spinal stenosis (SS) and IVD herniation. A total of 34 laboratory research papers evaluate the association between DM and IVDD.

RESULTS

There are 7 studies that correlate DM with IVDD, 4 of them showing that DM is a significant risk factor for degeneration, and 3 of them failing to establish any association. Three studies demonstrate significant association between DM and SS. However, 2 of these studies also include patients with IVD herniation that failed to demonstrate any correlation with DM. Two other studies indicate a significant association between DM and lumbar disc herniation. Multiple different mechanisms, acting independently or interactively, cause tissue damage leading to IVDD including: microangiopathy of the subchondral vertebral endplate, cellular senescence, cell death (through apoptosis or autophagy), hyperglycaemia, advance glycation end products, adipokines, and cytokines (through oxidative, osmotic, and inflammatory mechanisms).

CONCLUSION

The clinical evidence is not consistent, but weakly supports the relationship between DM and IVDD. However, the laboratory studies consistently suggest that DM interferes with multipronged aberrant molecular and biochemical pathways that provoke IVDD. Taken as a whole, the strong laboratory evidence and the weak clinical studies implicate DM as a distinct contributing factor for IVDD. These slides can be retrieved under Electronic Supplementary Material.

Osteogenic protein-1 alleviates high glucose microenvironment-caused degenerative changes in nucleus pulposus cells

Increasing evidence has indicated a close relationship between diabetes mellitus (DM) and disc degeneration. As a potential therapeutic growth factor, osteogenic protein-1 (OP-1) has lots of protective effects on the healthy disc cell’s biology. The present study was aimed to investigate the effects of OP-1 on degenerative changes of nucleus pulposus (NP) cells in a high glucose culture. Rat NP cells were cultured in the baseline medium or the high glucose (0.2 M) culture medium. OP-1 was added into the high glucose culture medium to investigate whether its has some protective effects against degenerative changes of NP cells in the high glucose culture. NP cell apoptosis ratio, caspase-3/9 activity, expression of apoptosis-related molecules (Bcl-2, Bax, and caspase-3), matrix macromolecules (aggrecan and collagen II), and matrix remodeling enzymes (MMP-3, MMP-13, and ADAMTS-4), and immuno-staining of NP matrix proteins (aggrecan and collagen II) were evaluated. Compared with the baseline culture, high glucose culture significantly increased NP cell apoptosis ratio, caspase-3/9 activity, up-regulated expression of Bax, caspase-3, MMP-3, MMP-13 and ADAMTS-4, down-regulated expression of Bcl-2, aggrecan and collagen II, and decreased staining intensity of aggrecan and collagen II. However, the results of these parameters were partly reversed by the addition of OP-1 in the high glucose culture. OP-1 can alleviate high glucose microenvironment-induced degenerative changes of NP cells. The present study provides that OP-1 may be promising in retarding disc degeneration in DM patients.

Population-based Risk Factors for the Development of Degenerative Disk Disease

STUDY DESIGN

This is a retrospective case control study.

OBJECTIVE

Identify risk factors and assess their relative impact on the development of degenerative disk disease (DDD).

SUMMARY OF BACKGROUND DATA

DDD is responsible for widespread disability in the civilian and military population. Despite the impact of low back pain and DDD, its multifactorial etiology is not entirely understood.

MATERIALS AND METHODS

The Defense Medical Surveillance System was searched for military members with the diagnosis of DDD as identified with the use of International Classification of Disease, 9th Revision (ICD-9) codes. These patients were compared with an age-matched and sex-matched control of military members without DDD from the Defense Medical Surveillance System. The prevalence of risk factors (obesity, hip, and knee osteoarthritis, tobacco dependence, diabetes, and type of employment) was then determined for both groups. In total, 160,911 patients with DDD were identified compared with 315,225 controls. Multivariate conditional logistical regression analysis was utilized to determine odds ratio (OR) for these groups based on data matched by age and sex and were adjusted for military rank and race/ethnicity.

RESULTS

Diabetes showed an OR of 1.469 [confidence interval (CI), 1.350-1.598]. Hip and knee arthritis produced an OR of 2.925 (CI, 2.685-3.187) and tobacco dependency showed an OR of 1.799 (CI, 1.762-1.836). The comparison of overweight to normal body mass index produced an OR of 1.334 (CI, 1.307-1.361) and the analysis of obese to normal body mass index had an OR of 1.556 (CI, 1.497-1.618). There failed to be a clinically significant association between military duty assignments and the presence of DDD.

CONCLUSIONS

Our research failed to show a clinical significance association between military duty assignment and DDD. However, we were able to identify a significant association between concomitant hip and knee osteoarthritis, obesity, diabetes, and tobacco dependency with the development of DDD.

LEVEL OF EVIDENCE

Level IV.

High glucose-induced excessive reactive oxygen species promote apoptosis through mitochondrial damage in rat cartilage endplate cells

Diabetes mellitus (DM) is an important factor in intervertebral disc degeneration (IDD). Apoptosis of cartilage endplate (CEP) cells is one of the initiators of IDD. However, the effects of high glucose on CEP cells are still unknown. Therefore, we conducted the present study to evaluate the effects of high glucose on CEP cells and to identify the mechanisms of those effects. Rat CEP cells were isolated and cultured in 10% foetal bovine serum (FBS, normal control) or high-glucose medium (10% FBS + 0.1 M glucose or 10% FBS + 0.2 M glucose, experimental conditions) for 1 or 3 days. In addition, CEP cells were treated with 0.2 M glucose for 3 days in the presence or absence of alpha-lipoic acid (ALA, 0.15 M). Flow cytometry was performed to identify and quantify the degree of apoptosis. The expression of reactive oxygen species (ROS) was assessed by flow cytometry, and mitochondrial damage (mitochondrial membrane potential) was assessed by fluorescence microscopy. Furthermore, the expression levels of cleaved caspase-3, cleaved caspase-9, Bcl-2, Bax, and cytochrome c were evaluated by Western blotting. High glucose significantly increased apoptosis and ROS accumulation in CEP cells in a dose- and time-dependent manner. Meanwhile, a disrupted mitochondrial membrane potential was detected in rat CEP cells cultured in the two high glucose concentrations. Incubating in high glucose enhanced the expression levels of cleaved caspase-3, cleaved caspase-9, Bax, and cytochrome c but decreased the level of the anti-apoptotic protein Bcl-2. ALA inhibited the expression of cleaved caspase-3, cleaved caspase-9, Bax, and cytochrome c but enhanced the expression of Bcl-2. ALA also prevented disruption of the mitochondrial membrane potential in CEP cells. This study demonstrates that high glucose-induced excessive reactive oxygen species promote mitochondrial damage, thus causing apoptosis in rat CEP cells in a dose- and time-dependent manner. ALA could prevent mitochondrial damage and apoptosis caused by high glucose in CEP cells. The results suggest that appropriate blood glucose control may be the key to preventing IDD in diabetic patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2476-2483, 2018.

Is there an association between diabetes and neck pain and lower back pain? Results of a population-based study

BACKGROUND

The objective of the study was to study the association between low back pain (LBP), neck pain (NP), and diabetes while controlling for many sociodemographic characteristics, comorbidities, and lifestyle variables. The study also aimed to identify which of these variables is independently associated with LBP and NP among diabetes sufferers.

METHODS

A case-control study using data taken from the European Health Interview Surveys for Spain was conducted in 2009/2010 (n=22,188) and 2014 (n=22,842). We selected subjects ≥40 years of age. Diabetes status was self-reported. One non-diabetic control was matched by the year of survey, age, and sex for each diabetic case. The presence of LBP and NP was defined as the affirmative answer to both of the questions: "Have you suffered chronic LBP/NP over the last 12 months?" and "Has your physician confirmed the diagnosis?" Independent variables included demographic and socioeconomic characteristics, health status variables, lifestyles, and pain characteristics.

RESULTS

The prevalence of NP (32.2% vs 26.8%) and LBP (37.1% vs 30.3%) was significantly higher among those suffering from diabetes. Multivariable analysis showed that diabetes was associated with a 1.19 (95% CI 1.04-1.36) and 1.20 (95% CI 1.06-1.35) higher risk of NP and LBP. Among diabetic subjects, being female, concomitant mental or respiratory disorders, being obese, and physically inactive are variables associated with suffering from these pains. Those suffering NP had 8 times higher risk of reporting LBP than those without NP and the same association is found among those suffering from LBP.

CONCLUSION

The prevalence and intensity of NP and LBP are high among people with diabetes, affecting them significantly more than their age- and sex-matched non-diabetic controls. Specific preventive and educational strategies must be implemented to reduce the incidence, severity, and negative effect on the quality of NP and LBP among diabetic patients.

Resveratrol attenuates high glucose-induced nucleus pulposus cell apoptosis and senescence through activating the ROS-mediated PI3K/Akt pathway

Background: Diabetes mellitus is closely correlated with disc degeneration. Nucleus pulposus (NP) cell apoptosis and senescence are typical cellular features within the degenerative disc. Resveratrol is a newly identified phytoalexin that has protective effects on cartilaginous tissue.

Objective: To investigate the whether resveratrol can protect against high glucose-induced NP cell apoptosis and senescence, and the potential mechanism in this process.

Methods: Rat NP cells were cultured in either 10% FBS culture medium (control group) or 10% FBS with a high glucose concentration (0.2 M, experiment group) for 3 days. Resveratrol or the combination of resveratrol and LY294002 was added into the culture medium of experiment group to investigate the effects of resveratrol and the PI3K/Akt pathway.

Results: High glucose significantly promoted NP cell apoptosis and NP cell senescence compared with the control group. Resveratrol exhibited protective effects against high glucose-induced NP cell apoptosis and senescence. Further analysis showed that resveratrol suppressed reactive oxygen species (ROS) generation and increased the activity of the PI3K/Akt pathway under the high glucose condition. However, the LY294002 had no significant effects on ROS content in the resveratrol-treated high glucose group.

Conclusion: Resveratrol can attenuate high glucose-induced NP cell apoptosis and senescence, and the activation of ROS-mediated PI3K/Akt pathway may be the potential mechanism in this process.

The potential effect of type 2 diabetes mellitus on lumbar disc degeneration: a retrospective single-center study

Background

Diabetes mellitus (DM) and low back pain which is mainly caused by degeneration of the intervertebral discs (IVDs) both are major public health problem worldwide. The present study was designed to investigate the association between type 2 diabetes mellitus (T2D) and severity of lumbar disc degeneration (LDD).

Methods

We retrospectively reviewed patients with low back pain visiting our spine clinic in 2014. Low back pain patients all have the lumbar MRI imaging and no previous treatment. One hundred fifty patients without T2D (group A) and 622 patients with T2D meeting the criteria were included. Sex, age, body mass index (BMI), high blood pressure (HBP), history of smoking, alcohol use, and duration of T2D were recorded. Patients with T2D were assigned to a well-controlled group (group B, n = 380) and a bad-controlled group (group C, n = 242). In group B, T2D duration of 148 patients was ≤ 10 years (group B1) and 232 patients > 10 years (group B2). In group C, T2D duration of 100 patients was ≤ 10 years (group C1) and 142 patients > 10 years (group C2). The severity of LDD was evaluated using the five-level Pfirrmann grading system. Data were analyzed using SPSS 19.0.

Results

Demographic data except age showed no difference among groups (P > 0.5). Compared to patients without T2D, patients with T2D showed more severe disc degeneration after removal of age effects (P < 0.05). From L1/2 to L5/S1, the average Pfirrmann scores between groups A and B1 showed no difference(P > 0.05); groups B2, C1, and C2 showed higher average Pfirrmann scores than group A (P < 0.05). Groups B2 and C2 showed higher average Pfirrmann scores than groups B1 and C1 (P < 0.05). Groups C1 and C2 showed higher average Pfirrmann scores than groups B1 and B2 (P < 0.05). From L1/2 to L5/S1, the severity of LDD was highly positively related to T2D duration both in groups B and C (P < 0.05).

Conclusions

T2D duration > 10 years and a bad control of T2D were risk factors for LDD. The longer T2D duration was, the more severe disc degeneration would be.

High Glucose Induces Autophagy through PPARγ-Dependent Pathway in Human Nucleus Pulposus Cells

Diabetes mellitus is a multiorgan disorder affecting many types of connective tissues, including bone and cartilage. High glucose could accelerate the autophagy in nucleus pulposus (NP) cells. In our present study, we investigated whether peroxisome proliferator-activated receptor γ (PPAR-γ) pathway is involved into autophagy regulation in NP cells under high glucose condition. After NP cells were treated with different high glucose concentrations for 72 hours, the rate of autophagy increased. Moreover, the levels of PPARγ, Beclin-1, and LC3II were significantly increased and p62 was significantly decreased compared to control group. Then, NP cells were treated with high glucose plus PPARγ agonist or PPARγ antagonist, respectively. The rate of autophagy and the levels of Beclin-1 and LC3II increased, but p62 decreased when PPARγ agonist was used. On the contrary, the rate of autophagy and the levels of Beclin-1 and LC3II decreased, while p62 increased when PPARγ antagonist was added. These results suggested that autophagy induced by high glucose in NP cells was through PPARγ-dependent pathway.

Pramlintide regulation of extracellular matrix (ECM) and apoptosis through mitochondrial-dependent pathways in human nucleus pulposus cells

Pramlintide, an approved analog of amylin, is responsible for regulating the physiology of energy homeostasis. The goals of this study were to investigate the roles of pramlintide in the regulation of cell survival and matrix metabolism, and further explore their underlying mechanisms, in human nucleus pulposus (NP) cells. NP cells were treated with different concentrations of pramlintide in normoxic or hypoxic conditions. Cell viability, LAC concentration, calcium concentration, mitochondrial membrane potential (ΔΨm), MMPs proteins, and apoptotic related proteins were detected. The results indicate that pramlintide could improve NP cell proliferation, glycolytic activity, and the ECM synthesis under hypoxia, which is evident from the increased precipitation of proteoglycans; increased expression of AGG, Col2, and SOX9 proteins; and decreased expression of MMP3, MMP9, and MMP13 proteins, which are Ca²⁺-dependent enzymes. And, pramlintide could facilitate the survival of NP cells through mitochondrial-mediated, Bcl-2/caspase-3-dependent apoptosis. In addition, activation of AKT-AMPK/mTOR signaling pathway is also observed by the treatment. These findings demonstrate that pramlintide may play a pivotal role in reversing intervertebral disk degeneration and may relieve the impairment of ECM metabolism and NP cells survival through mitochondrial-dependent apoptotic signaling pathway, thus offering a novel potential pharmacological treatment strategy.

Detection of O-Linked-N-Acetylglucosamine Modification and Its Associated Enzymes in Human Degenerated Intervertebral Discs

Study Design

Human herniated discs were obtained from discectomy specimens for the immunohistochemical detection of O-GlcNAc and O-GlcNAcase (OGA)/O-GlcNAc transferase (OGT).

Purpose

This study aimed to quantify the extent of O-GlcNAcylation and its associated enzymes (OGT/OGA) in human degenerated intervertebral discs.

Overview of Literature

The O-GlcNAcylation of nuclear, cytoplasmic, and mitochondrial proteins as well as the effects of such post-translational modifications are currently the focus of extensive research. O-GlcNAcylation is believed to contribute to the etiology of chronic illnesses by acting as a nutrient and stress sensor in the cellular environment. Mature intervertebral disc cells are chondrocyte-like cells, and O-GlcNAc has been shown to promote chondrocyte apoptosis in vitro. We believe that O-GlcNAcylation is a key regulator of disc degeneration.

Methods

Fifty-six specimens were fixed for 24 hours in a 10% solution of neutral-buffered formaldehyde, dehydrated, and embedded in paraffin. Tissue slices (4-µm-thick) were used for hematoxylin-eosin staining and immunohistochemistry.

Results

We found that O-GlcNAcylation of cytoplasmic proteins was less than that of nuclear proteins in both single cells and cell clusters. Cytoplasmic O-GlcNAcylation occurs subsequent to nuclear O-GlcNAcylation and is directly proportional to disc degeneration. OGT and O-GlcNAc expression levels were identical in all specimens examined.

Conclusions

O-GlcNAc and OGA/OGT expression is shown to correlate for the first time with intervertebral disc cell degeneration. Increasing disc degeneration is associated with increasing O-GlcNAcylation in both nuclear and cytoplasmic proteins in human disc cells.

Diabetes and Back Pain: Markers of Diabetes Disease Progression Are Associated With Chronic Back Pain

IN BRIEF Diabetes has been associated with the incidence of back pain. However, the relationship between markers of diabetes progression and back pain has not been studied. The objective of this study was to correlate clinical and laboratory measures of diabetes disease severity to the presence of back pain to provide insight into the relationship between these conditions. Findings showed that markers of diabetes disease progression were associated with the presence of back pain, suggesting that uncontrolled diabetes may contribute to the development of chronic back pain.

Down-regulation of islet amyloid polypeptide expression induces death of human annulus fibrosus cells via mitochondrial and death receptor pathways

Islet amyloid polypeptide (IAPP) exerts its biological effects by participating in the regulation of glucose metabolism and cell apoptosis. The main goal of the present study was to investigate the expression of IAPP in degenerated intervertebral disc tissue and IAPP's modulation of extracellular matrix (ECM) catabolic and anabolic genes in human AF cells. We found that the expression of IAPP, the calcitonin receptor, and receptor activity modifying protein decreased considerably in AF cells during the progression of intervertebral disc degeneration (IDD). Meanwhile, transfection with pLV-siIAPP decreased the expression of IAPP and its receptors and reduced glucose uptake and the expression of aggrecan, Col2A1, and BG. Down-regulation of IAPP also induced a significant increase in reactive oxygen species generation in AF cells, along with a decrease in matrix metalloproteinases and an increase in the concentration of cellular Ca²⁺_, ultimately leading to death. Further analysis revealed that siIAPP intervention promoted the release of cytochrome c from mitochondria, resulting in the activation of Caspase-3 and Caspase-9. In contrast, significantly decreased expression of Caspase-3 and Caspase-9 was observed in AF cells transfected with pLV-IAPP. The concentrations of Fas and FasL proteins were significantly decreased in AF cells transfected with PLV-IAPP, while activation of the Fas/FasL system and cell death were induced by siIAPP intervention. Mechanistically, AMPK/Akt-mTOR signaling pathways were involved. In conclusion, down-regulation of IAPP expression induces the death of human AF cells via mitochondrial and death receptor pathways, potentially offering a novel therapeutic target for the treatment of IDD.

The Regenerative Potential of Notochordal Cells in a Nucleus Pulposus Explant

STUDY DESIGN

In vitro disk explant culture.

OBJECTIVE

Notochordal cells (NCs) have been shown to upregulate matrix production by nucleus pulposus (NP) cells in coculture. To examine the translation of these in vitro results to a nativelike setting, the regenerative potential of NCs injected into NP tissue was assessed in this study.

METHODS

NP explants were cultured after injection with NCs in phosphate-buffered saline (PBS) or with PBS alone (sham). At days 0 and 42, cell viability and morphology, water, DNA, sulfated glycosaminoglycan and hydroxyproline content, and gene expression of anabolic markers were analyzed.

RESULTS

NCs remained viable during culture, but their morphology changed. The biochemical content remained unchanged, except for the DNA content in the NC group. Overall ACAN expression remained unchanged, whereas COL2A1 decreased during culture.

CONCLUSIONS

No overall anabolic response was observed when NCs were injected into NP explants. NCs were found to survive but did not display the typical NC morphology by the end of the culture period.

IAPP modulates cellular autophagy, apoptosis, and extracellular matrix metabolism in human intervertebral disc cells

The pathogenic process of intervertebral disc degeneration (IDD) is characterized by imbalance in the extracellular matrix (ECM) metabolism. Nucleus pulposus (NP) cells have important roles in maintaining the proper structure and tissue homeostasis of disc ECM. These cells need adequate supply of glucose and oxygen. Islet amyloid polypeptide (IAPP) exerts its biological effects by regulating glucose metabolism. The purpose of this study was to investigate the expression of IAPP in degenerated IVD tissue, and IAPP modulation of ECM metabolism in human NP cells, especially the crosstalk mechanism between apoptosis and autophagy in these cells. We found that the expression of IAPP and Calcr-RAMP decreased considerably during IDD progression, along with the decrease in the expression of AG, BG, and Col2A1. Induction of IAPP in NP cells by transfection with pLV-IAPP enhanced the synthesis of aggrecan and Col2A1 and attenuated the expression of pro-inflammatory factors, tumor necrosis factor (TNF)-α, and interleukin (IL)-1. Upregulation of IAPP also affected the expression of the catabolic markers—matrix metalloproteinases (MMPs) 3, 9 and 13 and ADAMTS 4 and 5. Downregulation of IAPP by siRNA inhibited the expression of anabolic genes but increased the expression of catabolic genes and inflammatory factors. The expressions of autophagic and apoptotic markers in NP cells transfected with pLV-IAPP were upregulated, including BECLIN1, ATG5, ATG7, LC3 II/I and Bcl-2, while significantly increase in the expression of Bax and Caspase-3 in NP cells transfected with pLV-siIAPP. Mechanistically, PI3K/AKT-mTOR and p38/JNK MAPK signal pathways were involved. We propose that IAPP might play a pivotal role in the development of IDD, by regulating ECM metabolism and controlling the crosstalk between apoptosis and autophagy in NP, thus potentially offering a novel therapeutic approach to the treatment of IDD.

Chronic low-back pain in adult with diabetes: NHANES 2009-2010

The aim of this study was to test the hypothesis that diabetes mellitus (DM) is associated with an increased prevalence of chronic low back pain (CLBP) in the general population. We analyzed data for 5106 adults (4591 without DM & 515 with diagnosed DM), who were part of the National Health and Nutrition Examination Survey (NHANES) from 2009 through 2010. Adults with DM were older (mean age 54.2years' vs. 42.1years), more likely to be obese (BMI>30, 69.5% vs. 33.3%), less educated (college or above 44.4% vs. 57.3%), had a lower annual income (<$20,000, 16.8% vs. 13.4%), were more likely to be a former smoker (31.5% vs. 20.9%), less physically active (43.5% vs. 59.4%). The prevalence of CLBP was 19.8% in adults with DM vs. 12.9% in adults without DM (age-adjusted OR 1.46; 95% CI, 1.00-1.94, P=.050). After the adjustments for CLBP's known risk factors, the association remained significant (OR 1.39; 95% CI, 1.02-1.92, P=.041). Adults with DM have a higher prevalence of CLBP. Further research is needed to examine the association and pathophysiology of DM and CLBP as well as the role of shared risk factors.

SUMMARY

Adults with diabetes have higher prevalence of chronic low back pain (CLBP), and higher odds of CLBP after adjusting for LBP risk factors.

The Paracrine Effect of Degenerated Disc Cells on Healthy Human Nucleus Pulposus Cells Is Mediated by MAPK and NF-κB Pathways and Can Be Reduced by TGF-β1

Inflammation is thought to have a major role in the pathogenesis of disc degeneration. Studies have shown that nucleus pulposus cells (NPCs) respond to one or two specific cytokines by regulating cell proliferation or matrix synthesis. However, the effects of a cocktail of factors secreted by degenerated disc cells on transplanted exogenous healthy NPCs remain unknown. Concentrations of multiple cytokines in degenerated disc tissue-conditioned medium (dCM) were measured using enzyme-linked immunosorbent assay (ELISA). 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and Ki67 immunofluorescence staining were used to evaluate the proliferation of cells in dCM. The function of exogenous NPCs cultured in dCM was evaluated by examining catabolic markers (ADAMTS-4, ADAMTS-5, MMP-1, MMP-3, and MMP-13), anabolic markers (TIMP-1, TIMP-2, and TIMP-3), and the extracellular matrix protein-aggrecan (ACAN) and collagen II (COL2)-expression with real time polymerase chain reaction (RT-PCR). Mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) pathway activation was observed using Western blotting. Finally, we examined the role of transforming growth factor (TGF)-β1 in reducing dCM-mediated exogenous NPC dysfunction. Levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-1α, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17, interferon-γ (IFN-γ), and prostaglandin E2 (PGE2) were higher and TGF-β1 levels were lower in dCM compared with the control medium. Treatment with dCM increased the proliferation of healthy NPCs. NPCs exhibited significantly higher expression of ADAMTS-4, ADAMTS-5, MMP-1, MMP-3, and MMP-13 and decreased TIMP-2, ACAN, and COL2 expression in the dCM group in a dose- and time-dependent manner. Treatment with dCM moderately increased TIMP-1 expression and had no effect on TIMP-3 mRNA levels. The MAPK and NF-κB pathways were implicated in dCM-mediated responses of healthy NPCs. TGF-β1 partially reversed the dCM-mediated NPC dysfunction. Increased levels of inflammatory factors and decreased TGF-β1 levels in dCM suggest an inflammatory environment in degenerated disc tissue. The catabolic effect of dCM on human healthy NPCs is mediated by MAPK and NF-κB pathways and can be reduced by TGF-β1.

Reoperation Rates After Anterior Cervical Discectomy and Fusion for Cervical Spondylotic Radiculopathy and Myelopathy: A National Population-based Study

STUDY DESIGN

National population-based cohort study.

OBJECTIVE

To compare the reoperation rates between cervical spondylotic radiculopathy and myelopathy in a national population of patients.

SUMMARY OF BACKGROUND DATA

There is an inherently low incidence of reoperation after surgery for cervical degenerative disease. Therefore, it is difficult to sufficiently power studies to detect differences between reoperation rates of different cervical diagnoses. National population-based databases provide large, longitudinally followed cohorts that may help overcome this challenge.

METHODS

We used the Korean Health Insurance Review and Assessment Service national database to select our study population. We included patients with the diagnosis of cervical spondylotic radiculopathy or myelopathy who underwent anterior cervical discectomy and fusion from January 2009 to June 2014. We separated patients into two groups based on diagnosis codes: cervical spondylotic radiculopathy or cervical spondylotic myelopathy. Age, sex, presence of diabetes, osteoporosis, associated comorbidities, number of operated cervical disc levels, and hospital types were considered potential confounding factors.

RESULTS

The overall reoperation rate was 2.45%. The reoperation rate was significantly higher in patients with cervical spondylotic myelopathy than in patients with cervical radiculopathy (myelopathy: P = 0.0293, hazard ratio = 1.433, 95% confidence interval 1.037-1.981). Male sex, presence of diabetes or associated comorbidities, and hospital type were noted to be risk factors for reoperation.

CONCLUSION

The reoperation rate after anterior cervical discectomy and fusion was higher for cervical spondylotic myelopathy than for cervical spondylotic radiculopathy in a national population of patients.

LEVEL OF EVIDENCE

3.

High Glucose-Induced Oxidative Stress Mediates Apoptosis and Extracellular Matrix Metabolic Imbalances Possibly via p38 MAPK Activation in Rat Nucleus Pulposus Cells

Objectives. To investigate whether high glucose-induced oxidative stress is implicated in apoptosis of rat nucleus pulposus cells (NPCs) and abnormal expression of critical genes involved in the metabolic balance of extracellular matrix (ECM). Methods. NPCs were cultured with various concentrations of glucose to detect cell viability and apoptosis. Cells cultured with high glucose (25 mM) were untreated or pretreated with N-acetylcysteine or a p38 MAPK inhibitor SB 202190. Reactive oxygen species (ROS) production was evaluated. Activation of p38 MAPK was measured by Western blot. The expression of ECM metabolism-related genes, including type II collagen, aggrecan, SRY-related high-mobility-group box 9 (Sox-9), matrix metalloproteinase 3 (MMP-3), and tissue inhibitor of metalloproteinase 1 (TIMP-1), was analyzed by semiquantitative RT-PCR. Results. High glucose reduced viability of NPCs and induced apoptosis. High glucose resulted in increased ROS generation and p38 MAPK activation. In addition, it negatively regulated the expression of type II collagen, aggrecan, Sox-9, and TIMP-1 and positively regulated MMP-3 expression. These results were changed by pretreatment with N-acetylcysteine or SB 202190. Conclusions. High glucose might promote apoptosis of NPCs, trigger ECM catabolic pathways, and inhibit its anabolic activities, possibly through a p38 MAPK-dependent oxidative stress mechanism.

Stem Cell Approaches to Intervertebral Disc Regeneration: Obstacles from the Disc Microenvironment

Intervertebral disc (IVD) degeneration results in segmental instability and irritates neural compressive symptoms, such as low back pain and motor deficiency. The transplanting of stem cell into degenerative discs has attracted increasing clinical attention, as a new and proven approach to alleviating disc degeneration and to relieving discogenic pains. Aside from supplementation with stem cells, the IVD itself already contains a pool of stem and progenitor cells. Since the resident disc stem cells are incapable of reversing the pathologic changes that occur during aging and disc degeneration, it has been debated as to whether transplanted stem cells are capable of providing an efficient and durable therapeutic effect, even though there have been positive outcomes in both animal models and in clinical trials. This review aims to decipher the interactions between the stem cell and the disc microenvironment. Within their new niches in the IVD, the exogenous stem cell shows metabolic adaptation to the low-glucose supply, hypoxia, and compressive loadings, but demonstrates little tolerance to the disc-like acidity and hypertonicity. Similarly, the survival of endogenous stem cells is threatened as well by the harsh disc microenvironment, which may exhaust the stem cell resources and restrict the self-repair capacity of a degenerating IVD. To eliminate the intrinsic obstacles within the stressful disc niches, stem cells should be delivered with an injectable scaffold that provides both survival and mechanical support. Quick healing or concretion of the injection injuries, which minimizes stem cell leakage and disturbance to disc homeostasis, is of equal importance toward achieving efficient stem cell-based disc regeneration.

Rat Notochordal Cells Undergo Premature Stress-Induced Senescence by High Glucose

Study Design

In vitro cell culture.

Purpose

The purpose of the study was to investigate the effect of high glucose on premature stress-induced senescence of rat notochordal cells.

Overview of Literature

Glucose-mediated increase of oxidative stress is a major causative factor for the development of diseases associated with diabetes mellitus such as senescence. However, no information is available for the effect of high glucose on premature stress-induced senescence of rat notochordal cells.

Methods

Notochordal cells were isolated from 4-week-old rats, cultured and placed in either 10% fetal bovine serum (FBS, normal control) or 10% FBS plus two high glucose concentrations (0.1 M and 0.2 M, experimental conditions) for 1 and 3 days. We identified and quantified the mitochondrial damage (mitochondrial transmembrane potential), reactive oxygen species (ROS) and antioxidants, such as manganese superoxide dismutase (MnSOD) and catalase, for each condition. We also identified and quantified senescence and telomerase activity. Finally, we determined the expression of proteins related to replicative senescence (p53-p21-pRB) and stress-induced senescence (p16-pRB) pathways.

Results

Two high glucose concentrations enhanced the disruption of mitochondrial transmembrane potential and excessive generation of ROS in notochordal cells for 1 and 3 days, respectively. The expressions of MnSOD and catalase were increased in notochordal cells treated with both high glucose concentrations at 1 and 3 days. The telomerase activity declined at 1 and 3 days. Two high glucose concentrations increased the occurrence of stress-induced senescence of notochordal cells by p16-pRB pathways at 1 and 3 days.

Conclusions

Despite compensatory expression of antioxidants, high glucose-induced oxidative stress accelerates stress-induced senescence in rat notochordal cells. This may result in dysfunction of notochordal cells, leading to accelerated premature disc degeneration. The prevention of excessive generation of oxidative stress by strict blood glucose control is important to prevent or to delay premature disc degeneration in young patients with diabetes mellitus.

Mechanics and biology in intervertebral disc degeneration: a vicious circle

Intervertebral disc degeneration is a major cause of low back pain. Despite its long history and large socio-economical impact in western societies, the initiation and progress of disc degeneration is not well understood and a generic disease model is lacking. In literature, mechanics and biology have both been implicated as the predominant inductive cause; here we argue that they are interconnected and amplify each other. This view is supported by the growing awareness that cellular physiology is strongly affected by mechanical loading. We propose a vicious circle of mechanical overloading, catabolic cell response, and degeneration of the water-binding extracellular matrix. Rather than simplifying the disease, the model illustrates the complexity of disc degeneration, because all factors are interrelated. It may however solve some of the controversy in the field, because the vicious circle can be entered at any point, eventually leading to the same pathology. The proposed disease model explains the comparable efficacy of very different animal models of disc degeneration, but also helps to consider the consequences of therapeutic interventions, either at the cellular, material or mechanical level.

The adverse effects of diabetes on osteoarthritis: update on clinical evidence and molecular mechanisms

Projected increases in the prevalence of both diabetes mellitus (DM) and osteoarthritis (OA) ensure their common co-existence. In an era of increasing attention to personalized medicine, understanding the influence of common comorbidities such as DM should result in improved care of patients with OA. In this narrative review, we summarize the literature addressing the interactions between DM and OA spanning the years from 1962 to 2014. We separated studies depending on whether they investigated clinical populations, animal models, or cells and tissues. The clinical literature addressing the influence of DM on OA and its therapeutic outcomes suggests that DM may augment the development and severity of OA and that DM increases risks associated with joint replacement surgery. The few high quality studies using animal models also support an adverse effect of DM on OA. We review strengths and weaknesses of the common rodent models of DM. The heterogeneous literature derived from studies of articular cells and tissues also supports the existence of biochemical and biomechanical changes in articular tissues in DM, and begins to characterize molecular mechanisms activated in diabetic-like environs which may contribute to OA. Increasing evidence from the clinic and the laboratory supports an adverse effect of DM on the development, severity, and therapeutic outcomes for OA. To understand the mechanisms through which DM contributes to OA, further studies are clearly necessary. Future studies of DM-influenced mechanisms may shed light on general mechanisms of OA pathogenesis and result in more specific and effective therapies for all OA patients.

The relationship between diabetes and the reoperation rate after lumbar spinal surgery: a nationwide cohort study

BACKGROUND CONTEXT

Diabetes is present in 5% to 20% of patients undergoing spine surgeries and is a known risk factor for reoperation. Considering the chronicity of diabetes, its influence on the reoperation rate may differ over time.

PURPOSE

To present the relationship between diabetes and the reoperation rate over time.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

A national health insurance database was used to identify a cohort of patients who underwent an initial surgery for lumbar degenerative disease in 2003 (n=34,918).

OUTCOME MEASURES

The primary end point was any type of second lumbar surgery after fusion surgery (n=4,792) or decompression surgery (n=30,126) during the early (0-postoperative 90 days), short-term (91-365 days), and midterm (1-6 years) periods.

METHODS

All patients were followed up until December 2008. Cox proportional hazards regression modeling was used to assess the adjusted reoperation rates in the diabetic patients.

RESULTS

The incidence of diabetes in the present cohort was 24.5% in the fusion group and 16.9% in the decompression group. Overall, reoperation was performed in 13.2% (631 of 4,792) of the patients after fusion surgery and in 14.0% (4,214 of 30,126) of the patients after decompression surgery. After fusion surgery, diabetes did not make a significant difference in the reoperation rate during the entire follow-up period. After decompression surgery, the reoperation rate was not different during Postoperative Month 3, but diabetic patients showed a 1.2 to 1.4 times higher reoperation rate during postoperative 3 months to 5 years (p<.01).

CONCLUSIONS

The study did not find a relationship between diabetes at the time of surgery and the reoperation rate during the early postoperative period. Thereafter, the reoperation rate was not higher after fusion surgery in diabetic patients, but it was higher after decompression surgery.

Effect of high glucose on stress-induced senescence of nucleus pulposus cells of adult rats

Study Design

In vitro cell culture model.

Purpose

We investigated the effect of diabetes mellitus (DM) on senescence of adult nucleus pulposus (NP) cells.

Overview of Literature

DM is a major public health issue worldwide, especially adult-onset (type 2) DM. DM is also thought to be an important etiological factor in disc degeneration. Hyperglycemia is considered to be a major causative factor in the development of DM-associated diseases through senescence. However, little is known about the effects of DM on senescence in adult NP cells.

Methods

Adult NP cells were isolated from 24-week-old rats, cultured, and placed in either 10% fetal bovine serum (FBS, normal control) and 10% FBS plus two different high glucose concentrations (0.1 M or 0.2 M; experimental conditions) for 1 or 3 days. We identified and quantified the occurrence of senescence in adult rat NP cells using senescence-associated-beta-galactosidase (SA-β-Gal) staining. We also investigated the expression of proteins related to the replicative senescence (p53-p21-pRB) and stress-induced premature senescence (p16-pRB) pathways.

Results

The mean SA-β-Gal-positive percentage was increased in adult rat NP cells treated with high glucose in a dose- and time-dependent manner. Both high glucose levels increased the expression of p16 and pRB proteins in adult rat NP cells. However, the levels of p53 and p21 proteins were decreased in adult rat NP cells treated with both high glucose concentrations.

Conclusions

The current study demonstrated that high glucose accelerated stress-induced senescence in adult rat NP cells in a dose- and time-dependent manner. Accelerated stress-induced senescence in adult NP cells could be an emerging risk factor for intervertebral disc degeneration in older patients with DM. These results suggest that strict blood glucose control is important in prevent or delaying intervertebral disc degeneration in older patients with DM.

Effect of coculturing canine notochordal, nucleus pulposus and mesenchymal stromal cells for intervertebral disc regeneration

Introduction

Early degenerative changes in the nucleus pulposus (NP) are observed after the disappearance of notochordal cells (NCs). Thus, it has been suggested that NCs play an important role in maintaining the NP and may have a regenerative potential on other cells of the NP. As the number of resident NP cells (NPCs) decreases in a degenerating disc, mesenchymal stromal (stem) cells (MSCs) may be used for cell supplementation. In this study, using cells of one species, the regenerative potential of canine NCs was assessed in long-term three-dimensional coculture with canine NPCs or MSCs.

Methods

Canine NCs and canine NPCs or MSCs were cocultured in alginate beads for 28 days under hypoxic and high-osmolarity conditions. Cell viability, cell morphology and DNA content, extracellular matrix production and expression of genes related to NC markers (Brachyury, KRT18) and NP matrix production (ACAN, COL2A1, COL1A1) were assessed after 1, 15 and 28 days of culture.

Results

NCs did not completely maintain their phenotype (morphology, matrix production, gene expression) during 28 days of culture. In cocultures of NPCs and NCs, both extracellular matrix content and anabolic gene expression remained unchanged compared with monoculture groups, whereas cocultures of MSCs and NCs showed increased glycosaminoglycan/DNA. However, the deposition of these proteoglycans was observed near the NCs and not the MSCs. Brachyury expression in the MSC and NC coculture group increased in time. The latter two findings indicate a trophic effect of MSCs on NCs rather than vice versa.

Conclusions

No regenerative potential of canine NCs on canine NPCs or MSCs was observed in this study. However, significant changes in NC phenotype in long-term culture may have resulted in a suboptimal regenerative potential of these NCs. In this respect, NC-conditioned medium may be better than coculture for future studies of the regenerative potential of NCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0569-6) contains supplementary material, which is available to authorized users.