G protein coupled estrogen receptor attenuates mechanical stress-mediated apoptosis of chondrocyte in osteoarthritis via suppression of Piezo1

Yi Sun,Huanshen Gao,Chenkai Li,Ping Leng,Pengcheng Guo,Yikai Liu,Haining Zhang,Zhenghui Li

doi:10.1186/s10020-021-00360-w

Abstract

BackgroundApoptosis of chondrocyte is involved in osteoarthritis (OA) pathogenesis, and mechanical stress plays a key role in this process by activation of Piezo1. However, the negative regulation of signal conduction mediated by mechanical stress is still unclear. Here, we elucidate that the critical role of G protein coupled estrogen receptor (GPER) in the regulation of mechanical stress-mediated signal transduction and chondrocyte apoptosis.MethodsThe gene expression profile was detected by gene chip upon silencing Piezo1. The expression of GPER in cartilage tissue taken from the clinical patients was detected by RT-PCR and Western blot as well as immunohistochemistry, and the correlation between GPER expression and OA was also investigated. The chondrocytes exposed to mechanical stress were treated with estrogen, G-1, G15, GPER-siRNA and YAP (Yes-associated protein)-siRNA. The cell viability of chondrocytes was measured. The expression of polymerized actin and Piezo1 as well as the subcellular localization of YAP was observed under laser confocal microscope. Western blot confirmed the changes of YAP/ Rho GTPase activating protein 29 (ARHGAP29) /RhoA/LIMK /Cofilin pathway. The knee specimens of osteoarthritis model were stained with safranin and green. OARSI score was used to evaluate the joint lesions. The expressions of GPER and YAP were detected by immunochemistry.ResultsExpression profiles of Piezo1- silenced chondrocytes showed that GPER expression was significantly upregulated. Moreover, GPER was negatively correlated with cartilage degeneration during OA pathogenesis. In addition, we uncovered that GPER directly targeted YAP and broadly restrained mechanical stress-triggered actin polymerization. Mechanism studies revealed that GPER inhibited mechanical stress-mediated RhoA/LIMK/cofilin pathway, as well as the actin polymerization, by promoting expression of YAP and ARHGAP29, and the YAP nuclear localization, eventually causing the inhibition of Piezo1. YAP was obviously decreased in degenerated cartilage. Silencing YAP caused significantly increased actin polymerization and activation of Piezo1, and an increase of chondrocyte apoptosis. In addition, intra-articular injection of G-1 to OA rat effectively attenuated cartilage degeneration.ConclusionWe propose a novel regulatory mechanism underlying mechanical stress-mediated apoptosis of chondrocyte and elucidate the potential application value of GPER as therapy targets for OA.

Highlights

Osteoarthritis (OA) is a chronic and degenerative disease of the joint, which is characterized by degeneration of cartilage, subchondral bone changes, and formation of osteophytes (Glyn-Jones et al 2015)
G protein coupled estrogen receptor (GPER) is upregulated in chondrocytes exposed to mechanical stress after Piezo1 silencing In order to explore the molecular and regulatory networks that interact with Piezo1, we explored the effect of Piezo1-siRNA on the expression profile of chondrocytes exposed to mechanical stress
Further studies showed that the novel estrogen receptor GPER was significantly up-regulated after Piezo1 silencing, while the conventional ERα and ERβ had no significant change

Summary

Introduction

Osteoarthritis (OA) is a chronic and degenerative disease of the joint, which is characterized by degeneration of cartilage, subchondral bone changes, and formation of osteophytes (Glyn-Jones et al 2015). In addition to genetic and environmental factors, mechanical stress has a crucial effect on the development of osteoarthritis by regulating chondrocyte apoptosis (Felson et al 2000). It was found that apoptosis of chondrocytes induced by mechanical stress was downregulated by cytochalasin D (cytoD), implying that cytoskeleton protein, especially the actin, may have vital roles in mechanical signal transduction during OA. Chondrocytes from OA cartilage show actin polymerization, which renders OA cartilage, susceptible to mechanical stress (Millward-Sadler et al 2000). Apoptosis of chondrocyte is involved in osteoarthritis (OA) pathogenesis, and mechanical stress plays a key role in this process by activation of Piezo. We elucidate that the critical role of G protein coupled estrogen receptor (GPER) in the regulation of mechanical stress-mediated signal transduction and chondrocyte apoptosis

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Results

Conclusion