Advanced glycation end products induce nucleus pulposus cell apoptosis by upregulating TXNIP via inhibiting glycolysis pathway in intervertebral disc degeneration.

Accumulation of advanced glycation end products (AGEs) causes apoptosis in human nucleus pulposus cells (NPCs), contributing to intervertebral disc degeneration (IVDD). The purpose of this study was to determine the roles of thioredoxin-interacting protein (TXNIP) in the mechanisms underlying AGE-induced apoptosis of NPCs. TXNIP was silenced or overexpressed in HNPCs exposed to AGEs. Glycolysis was assessed using extracellular acidification rate (ECAR), ATP level, GLUT1, and GLUT4 measurements. AGEs, TXNIP, GLUT1, and GLUT4 levels in IVDD patients were measured as well. In NPCs, AGEs reduced cell viability, induced apoptosis, inhibited glycolysis, and increased TXNIP expression. Silencing TXNIP compromised the effects of AGEs on cell viability, apoptosis, and glycolysis in NPCs. Furthermore, TXNIP overexpression resulted in decreased cell viability, increased apoptotic cells, and glycolysis suppression. Furthermore, co-treatment with a glycolysis inhibitor improved TXNIP silencing's suppressive effects on AGE-induced cell injury in NPCs. In IVDD patients with Pfirrmann Grades II-V, increasing trends in AGEs and TXNIP were observed, while decreasing trends in GLUT1 and GLUT4. AGE levels had positive correlations with TXNIP levels. Both AGE and TXNIP levels correlated negatively with GLUT1 and GLUT4. Our study indicates that TXNIP plays a role in mediating AGE-induced cell injury through suppressing glycolysis. The accumulation of AGEs, the upregulation of TXNIP, and the downregulation of GLUT1 and GLUT4 are all linked to the progression of IVDD.

TRIM32 triggers ß-catenin signaling through ubiquitylation of AXIN1 to promote inflammatory factor-induced apoptosis of rat nucleus pulposus cells.

The dysregulation of ubiquitin ligase is the cause of many human diseases. Tripartite motif protein 32 (TRIM32) is an E3 ubiquitin ligase whose role in nucleus pulposus (NP) cell apoptosis is unclear. The expression of TRIM family protein and ß-catenin in 40 NP tissue samples was detected by RT-PCR. Interleukin (IL)-1ß or tumor necrosis factor (TNF)-α was used to treat rat NP cells. Knockdown and overexpression of Trim32 were achieved using specific siRNA and recombinant plasmids. Western blotting, RT-PCR, and flow cytometry were used to assess the expression of TRIM32/ß-catenin and the apoptosis rate of NP cells. Coimmunoprecipitation was adopted to analyze the possible interactions between AXIN1 and TRIM32. In clinical samples, TRIM32 expression was of positive relevance with the expression of CTNNB1 (ß-catenin). In vitro, apoptosis of IL-1ß- or TNF-α-treated rat NP cells was induced through upregulated Trim32 expression and activated ß-catenin signaling, whereas Trim32 siRNA and inhibition of ß-catenin reversed the induction effect of cytokines. Further studies indicated that TRIM32 activated the ß-catenin signaling pathway through ubiquitination of AXIN1, thereby regulating apoptosis. Collectively, this study reveals that TRIM32 promotes inflammatory factor-induced apoptosis of rat NP cells, in part by direct degradation of AXIN1 to trigger ß-catenin signaling.

Tumor Necrosis Factor Alpha Promotes Osteoclast Formation Via PI3K/Akt Pathway-Mediated Blimp1 Expression Upregulation.

Tumor necrosis factor alpha (TNF-α)-induced osteoclastogenesis have profound effects in states of inflammatory osteolysis such as rheumatoid arthritis, periprosthetic implant loosening, and periodontitis. However, the exact mechanisms by which TNF-α promotes RANKL-induced osteoclast formation remains poorly understood. B lymphocyte-induced maturation protein-1 (Blimp1) is a transcriptional repressor that plays crucial roles in the differentiation and/or function of various kinds of cells including osteoclasts. A novel mechanism was identified where TNF-α-mediated Blimp1 expression, which contributed to RANKL-induced osteoclastogenesis. It is shown that TNF-α could promote the level of Blimp1 expression during osteoclast differentiation. Silencing of Blimp1 in osteoclast precursor cells obviously attenuated the stimulatory effect of TNF-α on osteoclastogenesis. Mechanistically, TNF-α-induced Blimp1 expression was markedly rescued by blocking the PI3K/Akt signaling pathway, which suggested that PI3K/Akt signaling was involved in the regulation of TNF-α-stimulated Blimp1 expression. Taken together, the results established a molecular mechanism of TNF-α-induced osteoclasts differentiation, and provided insights into the potential contribution of Blimp1 in the regulation of osteoclastogenesis by TNF-α. J. Cell. Biochem. 118: 1308-1315, 2017. © 2016 Wiley Periodicals, Inc.

The Impact of Cervical Degeneration and Sagittal Balance on Retro-Odontoid Soft-Tissue Thickness.

OBJECTIVE: To investigate whether retro-odontoid soft-tissue thickness (ROSTT) is associated with cervical degeneration, cervical spine mobility, and sagittal balance of cervical spine. METHODS: The data of 151 patients who presented at our hospital with cervical spondylosis were reviewed. The ROSTT was measured using T1-weighted sagittal cervical magnetic resonance imaging findings. The assessment of the degree of cervical intervertebral disc degeneration (IVDD) was conducted using sagittal T2-weighted imaging. The T1 slope (T1S), C0-C2 angle, C1-C2 angle, C2-C7 angle, C1-C7 sagittal vertical axis and C2-C7 sagittal vertical axis were measured. The range of motion was assessed by measuring the flexion-extension radiographs. According to the ROSTT, those measuring less than 3 mm were classified as normal group and those measuring larger than 3 mm were classified as thickened group. RESULTS: The thickened group had larger cervical IVDD grade, age, C2-C7 angle, and T1S compared to the normal group (all P < 0.05). Additionally, the C0-C2 angle was significantly smaller in the thickened group than in the normal group (P < 0.05). ROSTT showed a negative correlation with C0-C2 angle (r = -0.181, P < 0.05), but positive correlations with both C2-C7 angle (r = 0.255, P < 0.05) and T1S (r = 0.240, P < 0.05). Furthermore, ROSTT was positively correlated with age (r = 0277, P < 0.05) and cervical IVDD grade (Spearman, r = 0.299, P < 0.05). CONCLUSIONS: Cervical sagittal balance and cervical degeneration have a significant impact on ROSTT. Patients with a higher T1S and severe cervical degeneration are more likely to result in greater ROSTT.

Comparison of Atlantoaxial Intra-Articular Fusion and Posterior Structural Bone Grafting Techniques for Treating Atlantoaxial Dislocation.

BACKGROUND: The structural bone grafting (SBG) technique provided high fusion rate and satisfied outcomes for treating atlantoaxial dislocation, but it is unclear whether the atlantoaxial intra-articular cage (AIC) technique can provide clinical results comparable with SBG technique. OBJECTIVE: To compare the outcomes of 2 bone graft techniques applied in posterior C1-C2 screw-rod fixation and fusion surgery for treating atlantoaxial dislocation. METHODS: The data from 55 patients with atlantoaxial dislocation were retrospectively reviewed. The SBG technique had been used in 29 patients and the AIC technique in 26 patients. The outcomes were evaluated using the Japanese Orthopedic Association scale score, Neck Disability Index, and visual analog scale score for neck pain and compared between the 2 groups. The donor site complications were also recorded in SBG group, and donor site pain was assessed using a visual analog scale. RESULTS: In the final follow-up, the bone fusion rate was 100% in both groups. No significant differences were found in the bone fusion time between the 2 groups ( P > .05). Postoperatively, the Japanese Orthopedic Association, Neck Disability Index, and visual analog scale score for neck pain indexes improved significantly within both SBG (all P < .05) and AIC groups (all P < .05). Nevertheless, there were no statistically significant differences between the 2 groups (all P > .05). CONCLUSION: The SBG and AIC techniques were both effective for achieving atlantoaxial arthrodesis, and the AIC technique is a perfect alternative to the SBG technique when the posterior arch of C1 is incompetent.

Dysfunction of Caveolae-Mediated Endocytic TßRI Degradation Results in Hypersensitivity of TGF-ß/Smad Signaling in Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a genetic disorder caused by mutations of type I collagen-related genes, and excessive transforming growth factor-beta (TGF-ß) signaling is a common mechanism. TGF-ß/Smad signaling has inhibitory effects on osteoblast differentiation and maturation and is mainly transduced and regulated by the internalization of a tetrameric receptor complex comprising types I and II TGF-ß receptors (TßRI and TßRII). During internalization, clathrin-mediated endocytosis enhances TGF-ß/Smad signaling via Smad2/3 phosphorylation and receptors recycling, while caveolae-mediated endocytosis turns off TGF-ß/Smad signaling by promoting receptor ubiquitination and degradation. In this study, using an animal model of OI (Colla2oim , osteogenesis imperfecta murine [oim]/oim mouse), we found that osteoblastic cells of oim/oim mice were more sensitive to the inhibitory effects of TGF-ß on osteoblast differentiation and maturation and had much higher cell membrane protein levels of TGF-ß receptors than those of wild-type (wt)/wt mice. Further results showed that clathrin-mediated endocytosis of TßRI was enhanced, whereas caveolae-mediated TßRI endocytic degradation was reduced in oim/oim mice, combined with reduced caveolin-1 (Cav-1) phosphorylation. In addition, type I collagen downregulated TßRI via focal adhesion kinase (FAK) and Src activation-dependent Cav-1 phosphorylation. To further examine this mechanism, 4-week-old oim/oim and wt/wt mice were treated with either TßRI kinase inhibitor (SD-208) or vehicle for 8 weeks. SD-208 treatment significantly reduced the fracture incidence in oim/oim mice. Micro-computed tomography and biomechanical testing showed that femoral bone mass and strength were significantly improved with SD-208 treatment in both genotypes. Additionally, SD-208 significantly promoted osteoblast differentiation and bone formation and inhibited bone resorption. In conclusion, dysfunction of caveolae-mediated endocytic TßRI degradation is a possible mechanism for the enhanced TGF-ß/Smad signaling in OI. Targeting this mechanism using a TßRI kinase inhibitor effectively reduced fractures and improved bone mass and strength in OI model and, thus, may offer a new strategy for the treatment of OI. © 2022 American Society for Bone and Mineral Research (ASBMR).

MiR-202-3p regulates interleukin-1ß-induced expression of matrix metalloproteinase 1 in human nucleus pulposus.

MicroRNAs (miRNAs), small noncoding RNA molecules, have emerged as important factors during intervertebral disc degeneration. This study was to determine whether miR-202-3p regulates interleukin-1ß (IL-1ß)-induced expression of matrix metalloproteinase 1 (MMP-1) in human nucleus pulposus (NP) cells. Human NP cells were stimulated with IL-1ß in vitro. MicroRNA arrays were used to determine the expression profile of 1971 human miRNAs and the miRNAs targets were identified using bioinformatics. In IL-1ß-stimulated NP cells, 10 microRNAs were down-regulated, 2 microRNAs were up-regulated. There was a significant reduction in hsa-miR-202-3p (miR-202-3p) expression in the severe degenerative disc compared with mild degenerative disc. Down-regulation of miR-202-3p expression by IL-1ß was correlated with up-regulation of MMP-1 expression in human NP cells. IL-1ß-induced activation of MAP kinase (MAPK) and nuclear factor-κB (NF-κB) decreased miR-202-3p expression and induced MMP-1 expression. MiR-202-3p suppressed IL-1ß-induced MMP-1 production. Conversely, treatment with anti-miR-202-3p remarkably increased MMP-1 production. In addition, mutation of the miR-202-3p binding site in the 3'-UTR of MMP-1 mRNA abolished miR-202-3p-mediated repression of reporter activity. Functional analysis showed that miR-202-3p could decrease type II collagen degradation, whereas overexpression of MMP-1 by Lentiviral-shMMP-1 abolished the effect of miR-202-3p on type II collagen degradation. These results suggest that miR-202-3p is an important regulator of MMP-1 in human nucleus pulposus and may contribute to the development of intervertebral disc degeneration.

Posterior Open Reduction and Interlaminae Compression Fusion for Os Odontoideum with Atlantoaxial Dislocation.

OBJECTIVE: To evaluate the outcome of posterior open reduction and interlaminae compression fusion using a screw-rod system combined with a structural iliac bone graft in the treatment of atlantoaxial dislocation (AAD) secondary to os odontoideum. METHODS: A retrospective study was performed on 24 patients with AAD secondary to os odontoideum. All cases were with partial reduction after skeletal traction. Intraoperative open reduction and fixation were performed with a posterior screw-rod system, followed by interlaminae compression of an autologous iliac bone graft for fusion. The modified atlanto-dental interval (MADI) was measured to assess the degree of dislocation before traction, after traction, and postoperatively. Japanese Orthopaedic Association (JOA) score, Nurick scale score, visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI) score, and neck stiffness were used to evaluate functional outcomes. RESULTS: The mean duration of follow-up was 43.0 ± 24.0 months. All patients achieved relief of symptoms and solid bone fusion. There were no complications associated with instrumentation and operation. At the final follow-up, the average MADI was reduced to 2.0 ± 0.8 mm (pretraction: 9.2 ± 1.1 mm; post-traction: 6.6 ± 0.7 mm; P < 0.001). The neck stiffness was significantly relieved (P < 0.001), and function of the spinal cord manifested by the JOA score and Nurick scale score significantly improved (all P < 0.001). The NDI score and VASSNP markedly decreased (all P < 0.001). CONCLUSIONS: Intraoperative open reduction and interlaminae compression fusion using a posterior screw-rod system combined with a structural iliac bone graft is a safe and effective procedure for AAD secondary to os odontoideum.