Focused low-intensity pulsed ultrasound promotes chondrocyte mitophagy via up-regulating PGAM5 protein

Abstract

Objective To investigate the effect of focused low-intensity pulsed ultrasound (FLIPUS) on the activation of mitophagy in chondrocytes. Methods Chondrocytes were isolated from the knee articular cartilage of C57BL/6J suckling mice, and then primarily cultured. Then osteoarthritis-like chondrocyte injury was inflicted by IL-1β simulation in the chondrocytes and identified. The chondrocytes were divided into 3 groups, that is, control, IL-1β and IL-1β+FLIPUS group. The mRNA expression of Col2α1 and MMP13 was detected by quantitative real-time PCR, and the protein levels of Col2α1, MMP13, LC3B-Ⅱ, TOM20, TIM23, PGAM5, FUNDC1 and p-FUNDC1 (p-ser13) were detected by Western blotting. Results We cultured primary chondrocytes and established osteoarthritis-like chondrocyte injury model successfully. Compared with the control group, the mRNA and protein levels of Col2α1 were significantly decreased (P < 0.01), while the levels of MMP13 were significantly increased (P < 0.01) in the IL-1β group. The levels of Col2α1 were obviously enhanced (P < 0.05), while those of MMP13 were reduced (P < 0.01) in the IL-1β+FLIPUS group than the IL-1β group. Compared with the control group, the protein expression of LC3B-Ⅱ was remarkably reduced in the IL-1β group (P < 0.05). The protein levels of LC3B-Ⅱ and PGAM5 were significantly increased (P < 0.01), while those of TOM20, TIM23 and p-Ser13 were notably decreased (P < 0.05) in the IL-1β+FLIPUS group than the IL-1β group. Conclusion FLIPUS may activate the mitophagy in chondrocytes though dephosphorylation of FUNDC1 Ser13 via up-regulating PGAM5 expression.

Keywords

• focused low-intensity pulsed ultrasound
• knee osteoarthritis
• mitophagy
• pgam5
• fundc1