ER Stress-induced Apoptosis Of Osteoblasts Within The Osteolytic Osseous Tissues In Aseptic Loosening After Total Hip Replacement

Background:Wear particles-induced osteoblasts apoptosis in vitro has been documented in many studies. However, the apoptosis of osteoblasts whin osteolytic bone tissue and the specific mechanisms involved in the pathogenesis of osteolysis and aseptic loosening have been rarely studied. Objective:To investigate the cause of the aseptic loosening, providing new ideas and theoretical basis for aseptic loosening prevention. To observe the influence of ER stress on the apoptosis of osteoblasts in osteolytic bone tissue and osteolysis, and to investigate the pathogenesis of osteolysis, providing new tactics and therapeutic approach for the prevention and treatment of particles-induced osteolysis and aseptic loosening. Methods: the transmission electron microscope(TEM) was introduced to disclosed the tissue ultrastructure analysis of wear particles in interface membrane; The changes of bone resorption were assessed by toluidine blue staining; The transformation of inflammatory infiltration was evaluated by HE staining; The alteration of bone tunnel was valuated by ALP staining; The expression of ER stress markers(IRE1-α),Grp78/Bip 和 CHOP) was examined by Western blot in clinical osteolytic osseous specimens of patients suffered from aseptic loosening, osteolytic craniums from particles-induced osteolysis (PIO) animal models and osteoblasts treated with wear particles; The apoptosis of osteoblasts within clinical osteolytic osseous specimens and osteolytic craniums from mouse was evaluated by TUNEL staining and the immunohistochemistry of Caspase-3; The apoptosis rate of osteoblasts in vitro was evaluated via the flow cytometer and Caspae-3 activity assay; Furthermore, the differentiation of osteoblasts was measured by ALP activity and the viability of osteoblasts was measured by MTT assay. Results:Our results demonstrated that wear particles were capable of inducing ER stress in osteoblasts, and were associated with inflammation, osteoblasts differentiation and apoptosis in cultured osteoblasts, osteolytic craniums, and clinical loosened osseous specimens. Blocking ER stress with 4-PBA dramatically reduced ER stress and apoptosis in vitro and in vivo. Along with apoptosis, in PIO animal models, this ER stress blocker also dramatically promoted the differentiation of osteoblasts and reduced the severity of osteolysis. However, when mixed the ER stress inducer (Tg) in wear particles, the experimental result was completely the opposite. Conclusion:The results of our study suggest that pharmacological interventions targeting the ER stress of osteoblasts may lead to a promising therapeutic approach for the prevention and treatment of particles-induced osteolysis and aseptic loosening.