title: Inhibition of FSS-induced actin cytoskeleton reorganization by silencing LIMK2 gene increases the mechanosensitivity of primary osteoblasts.
abstract: Mechanical stimulation plays an important role in bone cell metabolic activity. However, bone cells lose their mechanosensitivity upon continuous mechanical stimulation (desensitization) and they can recover the sensitivity with insertion of appropriate rest period into the mechanical loading profiles. The concrete molecular mechanism behind the regulation of cell mechanosensitivity still remains unclear. As one kind of mechanosensitive cell to react to the mechanical stimulation, osteoblasts respond to fluid shear stress (FSS) with actin cytoskeleton reorganization, and the remodeling of actin cytoskeleton is closely associated with the alteration of cell mechanosensitivity. In order to find out whether inhibiting the actin cytoskeleton reorganization by silencing LIM-kinase 2 (LIMK2) gene would increase the mechanosensitivity of primary osteoblasts, we attenuated the formation of actin stress fiber under FSS in a more specific way: inhibiting the LIMK2 expression by RNA interference. We found that inhibition of LIMK2 expression by RNA interference attenuated the formation of FSS-induced actin stress fiber, and simultaneously maintained the integrity of actin cytoskeleton in primary osteoblasts. We confirmed that the decreased actin cytoskeleton reorganization in response to LIMK2 inhibition during FSS increased the mechanosensitivity of the osteoblasts, based on the increased c-Fos and COX-2 expression as well as the enhanced proliferative activity in response to FSS. These data suggest that osteoblasts can increase their mechanosensitivity under continuous mechanical stimulation by reducing the actin stress fiber formation through inhibiting the LIMK2 expression. This study provides us with a new and more specific method to regulate the osteoblast mechanosensitivity, and also a new therapeutic target to cure bone related diseases, which is of importance in maintaining bone mass and promoting osteogenesis.
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China.
authors.forename: Shuyi
authors.initials: S
authors.lastname: Tan
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200072, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Guangdong No. 2 Provincial People's Hospital, Guangzhou, Guangdong 510317, PR China.
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Guangzhou Hospital of Integrated Traditional and West Medicine, Guangzhou, Guangdong 510800, PR China.
authors.forename: Changjing
authors.initials: C
authors.lastname: Wu
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Huizhou Stomatological Hospital Zhong Kai Branch, Huizhou, Guangdong 516006, PR China.
authors.forename: Yajuan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China.
authors.forename: Zijun
authors.initials: Z
authors.lastname: Song
authors.affiliation: Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China. Electronic address: fuqiangds@aliyun.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu
mesh_terms: D008841:Actin Cytoskeleton; D000818:Animals; D000831:Animals, Newborn; D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D005434:Flow Cytometry; D020868:Gene Silencing; D054461:Lim Kinases / Q000235:genetics* / Q000378:metabolism; D040542:Mechanotransduction, Cellular; D008807:Mice, Inbred BALB C; D010006:Osteoblasts / Q000166:cytology / Q000201:enzymology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012212:Rheology; D013314:Stress, Mechanical; D015854:Up-Regulation
chemical_list: D016760:Proto-Oncogene Proteins c-fos; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D054461:Lim Kinases; C095325:Limk2 protein, mouse
keywords: Actin cytoskeleton reorganization; Cell mechanosensitivity; LIMK2 gene; Mechanotransduction; Osteoblasts