Stabilization of hypoxia-inducible factor-1α alleviates osteoarthritis via interacting with Per2 and resetting the circadian clock

Abstract

Objective: The study aimed to establish whether HIF1α entrains the core clock in chondrocytes and how the HIF1α affects the circadian rhythm.

Methods: We subjected primary chondrocytes to chronic circadian desynchrony (CCD) and subsequently treated with oxygen rhythm and dimethyloxalylglycine (DMOG). Circadian oscillations were analyzed with a real-time monitoring system of Per2 promoter activity and qPCR. Chondrocytes were assayed core clock genes expression patterns and extracellular matrix metabolism. HIF1α siRNA was used to knock down HIF1α. ChIP-qPCR and dual-luciferase reporter assay were used to validate that Per2 was the target gene of HIF1α. The surgical model of osteoarthritis was induced by destabilization of the medial meniscus (DMM). The chronic jet lag model was established light/dark cycle advance shift. Joint degeneration was measured using histological staining, immunological assays, and micro-CT scanning.

Results: We report that different patterns of clock genes expression between healthy and osteoarthritic cartilage tissues and oxygen rhythms and DMOG reset the molecular clockwork which was dampened after CCD culture in a HIF1α-dependent manner. HIF1α increased the amplitude of oscillation by directly binding to the HRE-like and E-box-like elements located on the Per2 promoter. The rhythmic circadian clock significantly enhanced extracellular matrix production. Our study also demonstrates that DMOG ameliorated the increased OA severity caused by jet lag in the DMM model.

Conclusions: This study shows that circadian clock resetting caused by DMOG is at least partially mediated by the HIF1α through interaction with the Per2 promoter and proposes DMOG as supportive therapy for OA.

Keywords: Cartilage; Circadian clock; HIF1alpha; Osteoarthritis.