title: Cyclic stretch promotes osteogenesis-related gene expression in osteoblast-like cells through a cofilin-associated mechanism.
abstract: Osteoblasts have the capacity to perceive and transduce mechanical signals, and thus, regulate the mRNA and protein expression of a variety of genes associated with osteogenesis. Cytoskeletal reconstruction, as one of the earliest perception events for external mechanical stimulation, has previously been demonstrated to be essential for mechanotransduction in bone cells. However, the mechanism by which mechanical signals induce cytoskeletal deformation remains poorly understood. The actin‑binding protein, cofilin, promotes the depolymerization of actin and is understood to be important in the regulation of activities in various cell types, including endothelial, neuronal and muscle cells. However, to the best of our knowledge, the importance of cofilin in osteoblastic mechanotransduction has not been previously investigated. In the present study, osteoblast‑like MG‑63 cells were subjected to physiological cyclic stretch stimulation (12% elongation) for 1, 4, 8, 12 and 24 h, and the expression levels of cofilin and osteogenesis-associated genes were quantified with reverse transcription‑quantitative polymerase chain reaction, immunofluorescence staining and western blotting analyses. Additionally, knockdown of cofilin using RNA interference was conducted, and the mRNA levels of osteogenesis‑associated genes were compared between osteoblast‑like cells in the presence and absence of cofilin gene knockdown. The results of the present study demonstrated that cyclic stretch stimulates the expression of genes associated with osteoblastic activities in MG‑63 cells, including alkaline phosphatase (ALP), osteocalcin (OCN), runt‑related transcription factor 2 (Runx2) and collagen‑1 (COL‑1). Cyclic stretch also regulates the mRNA and protein expression of cofilin in MG‑63 cells. Furthermore, stretch‑induced increases in the levels of osteogenesis-associated genes, including ALP, OCN, Runx2 and COL‑1, were reduced following cofilin gene knockdown. Together, these results demonstrate that cofilin is involved in the regulation of mechanical load‑induced osteogenesis and, to the best of our knowledge, provides the first evidence demonstrating the importance of cofilin in osteoblastic mechanotransduction.
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Shanmin
authors.initials: S
authors.lastname: Fu
authors.affiliation: Department of Stomatology, General Hospital of Shenyang Military Area Command, Shenyang, Liaoning 110084, P.R. China.
authors.forename: Zhaobin
authors.initials: Z
authors.lastname: Zeng
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Li
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Qiannan
authors.initials: Q
authors.lastname: Niu
authors.affiliation: Department of Biomedical Engineering, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Da
authors.initials: D
authors.lastname: Jing
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Xue
authors.initials: X
authors.lastname: Feng
mesh_terms: D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006801:Humans; D010006:Osteoblasts / Q000502:physiology*; D010012:Osteogenesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D051339:Actin Depolymerizing Factors; D012333:RNA, Messenger