Objective CDK9 controls the activation of primary inflammatory response genes. We determined whether CDK9 inhibition protects cartilage from the catabolic effects of pro-inflammatory cytokines. Methods Human chondrocytes were challenged with different pro-inflammatory stimuli (IL-1β, lipopolysaccharides, and TNFα), in the presence or absence of the CDK9 inhibitor Flavopiridol, or siRNA. The mRNA expression of inflammatory mediators, catabolic, and anabolic genes were determined by real-time PCR. Cartilage explants were incubated with IL-1β, with or without Flavopiridol, for 6 days. Cartilage matrix degradation was assessed by the release of glycosaminoglycan (GAG) and cleaved Type II collagen (Col2a) peptides. Results CDK9 inhibition by Flavopiridol, or knockdown by siRNA, effectively suppressed iNOS mRNA induction by all three pro-inflammatory stimuli. Results from NFkB-targets PCR array showed that Flavopiridol suppressed the induction of a broad range of inflammatory mediator genes (59 out of 67 tested) by IL-1β. CDK9 inhibition also suppressed induction of catabolic genes MMP 1, 3, 9, 13, and ADAMTS4, 5; but did not affect the basal expression of anabolic genes such as Col2a, aggrecan, and COMP, and housekeeping genes. Flavopiridol had no apparent short-term cytotoxicity as assessed by glucose-6-phosphate dehydrogenase activity. Finally, in IL-1β-treated cartilage explants, Flavopiridol reduced the release of matrix degradation products GAG and cleaved Col2a peptides, but did not affect long-term chondrocyte viability. Conclusion CDK9 activity is required for the primary inflammatory response in chondrocytes. Flavopiridol suppresses the induction of inflammatory mediators and catabolic genes to protect cartilage from the deleterious effects of pro-inflammatory cytokines, without impacting cell viability and functions.
Study Design: A retrospective study of prospectively collected radiographic and clinical data. Objective: This study aims to investigate the relationship between endplate morphology parameters and the incidence of cage subsidence in patients with mini-open single-level oblique lateral lumbar interbody fusion (OLIF). Methods: We included 119 inpatients who underwent OLIF from February 2015 to December 2017. A total of 119 patients with single treatment level of OLIF were included. Plain anteroposterior and lateral radiograph were taken preoperatively, postoperatively, and during follow-up. The correlation between disc height, endplate concave angle/depth, cage position and cage subsidence were investigated. Functional rating index (Visual Analogue Scale for pain, and Roland Morris Disability Questionnaire) were employed to assess clinical outcomes. Results: Cage subsidence was more commonly seen at the superior endplates (42/119, 35.29%) than at the inferior endplates (6/119, 5.04%) (p < 0.01). More importantly, cage subsidence was significantly less in patients with superior endplates that were without concave angle (3/20, 15%) than with concave angle (37/99, 37.37%) (p < 0.05). Cage subsidence correlated negatively with preoperative anterior disc height (r = −0.21, p < 0.05), but positively with disc distraction rate (r = 0.27, p < 0.01). Lastly, the distance of cage to the anterior edges of the vertebral body showed a positive correlation (r = 0.26, p < 0.01). Conclusions: This study for the first time demonstrated that endplate morphology correlates with cage subsidence after OLIF. Since relatively flat endplates with smaller concave angle significantly diminish the incidence of subsidence, the morphology of cage surface should be taken into consideration when designing the next generation of cage. In addition, precise measurement of the disc height to avoid over-distraction, and more anteriorly placement of the cage is suggested to reduce subsidence.
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