INSR mediated by transcription factor KLF4 and DNA methylation ameliorates osteoarthritis progression via inactivation of JAK2/STAT3 signaling pathway.

OBJECTIVE: To probe into the role and regulatory mechanisms of INSR in pathogenesis of osteoarthritis (OA).
METHODS: KLF4 and INSR expression was detected in cartilage tissues of 40 OA patients and 10 controls using RT-qPCR. IL-1β-induced OA chondrocytes and anterior cruciate ligament transection (ACLT)-induced OA models were respectively constructed. After overexpressing or silencing KLF4 or INSR, flow cytometry assay was utilized to detect chondrocyte apoptosis. Furthermore, JAK2/STAT3, cartilage markers and OA-related markers were examined by western blot. Dual luciferase report and CHIP assay were carried out to verify the interactions between KLF4 and INSR, followed by functional gain and loss assay. INSR promoter methylation was assessed by MS-PCR.
RESULTS: Both KLF4 and INSR were down-regulated both in OA chondrocytes and cartilage tissues. Knockdown of KLF4 or INSR accelerated apoptosis of IL-1β-induced OA chondrocytes. However, overexpression of KLF4 or INSR ameliorated OA progression both in OA chondrocytes and OA mouse models. Moreover, INSR inactivated JAK2/STAT3 pathway in OA chondrocytes. Dual luciferase report and CHIP assay results confirmed that INSR was transcriptionally regulated by KLF4. As shown in MS-PCR results, INSR expression was mediated by DNA methylation in OA.
CONCLUSION: Our findings suggested that INSR, as a key regulator for OA, was regulated by transcription factor KLF4 and DNA methylation, thereby mediating the activation of JAK2/STAT3 signaling, which was considered as an underlying therapeutic target for OA. AJTR