ER Stress Mediates TiAl6V4 Particle-Induced Peri-Implant Osteolysis by Promoting RANKL Expression in Fibroblasts.

Zhenheng Wang,Tongguo Shi,Ting Guo,Hongbo Qian,Nirong Bao,Jingjing Gan,Zhenzhen Wang,Naicheng Liu,Gang Zhou,Jianning Zhao,Dominique Heymann

doi:10.1371/journal.pone.0137774

Abstract

Wear particle-induced osteolysis is a major cause of aseptic loosening, which is one of the most common reasons for total hip arthroplasty (THA) failure. Previous studies have shown that the synovial fibroblasts present in the periprosthetic membrane are important targets of wear debris during osteolysis. However, the interaction mechanisms between the wear debris and fibroblasts remain largely unknown. In the present study, we investigated the effect of ER (endoplasmic reticulum) stress induced by TiAl6V4 particles (TiPs) in human synovial fibroblasts and calvarial resorption animal models. The expression of ER stress markers, including IRE1-α, GRP78/Bip and CHOP, were determined by western blot in fibroblasts that had been treated with TiPs for various times and concentration. To address whether ER stress was involved in the expression of RANKL, the effects of ER stress blockers (including 4-PBA and TUDCA) on the expression of RANKL in TiPs-treated fibroblasts were examined by real-time PCR, western blot and ELISA. Osteoclastogenesis was assessed by tartrate resistant acid phosphatase (TRAP) staining. Our study demonstrated that ER stress markers were markedly upregulated in TiPs-treated fibroblasts. Blocking ER stress significantly reduced the TiPs-induced expression of RANKL both in vitro and in vivo. Moreover, the inhibition of ER stress ameliorated wear particle-induced osteolysis in animal models. Taken together, these results suggested that the expression of RANKL induced by TiPs was mediated by ER stress in fibroblasts. Therefore, down regulating the ER stress of fibroblasts represents a potential therapeutic approach for wear particle-induced periprosthetic osteolysis.

Highlights

Wear particles induced osteolysis and the subsequent aseptic loosening are the most common reason for arthroplasty failure and revision surgery [1]
The results showed that TiAl6V4 particles (TiPs) markedly increased the protein levels of ER stress markers in both time- and dose-dependent manners (Fig 1A–1D)
ER stress mediated the upregulation of receptor activator of nuclear factor kappa-B ligand (RANKL) and the RANKL/OPG ratio in TiPs-stimulated fibroblasts and promoted osteoclastogenesis in vitro In TiPs-treated fibroblast cells, we observed a time-dependent upregulation of RANKL mRNA expression (Fig 2A)

Summary

Introduction

Wear particles induced osteolysis and the subsequent aseptic loosening are the most common reason for arthroplasty failure and revision surgery [1]. Fibroblasts constitute the majority of the cells in membrane interfaces, information on the response of fibroblasts to wear debris is less extensive than such information for other cell types such as macrophages and osteoclasts [2]. Studies have reported that fibroblasts in the periprosthetic membrane. Osteoclastogenesis is largely regulated by RANKL and OPG (osteoprotegrin) [3]. RANKL can promote osteoclast differentiation and activity while OPG is a decoy receptor that limits the biologic activity of RANKL, and the balance between RANKL and OPG is essential to regulate bone remodeling [4,5,6,7]. The mechanism underlying the expression of RANKL in fibroblasts that are affected by wear particles remains largely unknown [8]

Methods

Results

Conclusion