title: Mechanisms of Cdc42-mediated rat MSC differentiation on micro/nano-textured topography.
abstract: Micro/nano-textured titanium surface topography promotes osteoblast differentiation and the Wnt/β-catenin signaling pathway. However, the response of rat bone mesenchymal stem cells (MSCs) to micro/nano-textured topography, and the underlying mechanisms of its effects, are not well understood. We hypothesized that cell division cycle 42 protein (Cdc42), a key member of the Rho GTPases family, may regulate rat MSCs morphology and osteogenic differentiation by micro/nano-textured topography, and that crosstalk between Cdc42 and Wnt/β-catenin is the underlying mechanism. To confirm the hypothesis, we first tested rat MSCs' morphology, cytoskeleton, and osteogenic differentiation on micro/nano-textured topography. We then examined the cells' Wnt pathway and Cdc42 signaling activity. The results show that micro/nano-textured topography enhances MSCs' osteogenic differentiation. In addition, the cells' morphology and cytoskeletal reorganization were dramatically different on smooth surfaces and micropitted/nanotubular topography. Ligands of the canonical Wnt pathway, as well as accumulation of β-catenin in the nucleus, were up-regulated by micro/nano-textured topography. Cdc42 protein expression was markedly increased under these conditions; conversely, Cdc42 silencing significantly depressed the enhancement of MSCs osteogenic differentiation by micro/nano-textured topography. Moreover, Cdc42si attenuated p-GSK3β activation and resulted in β-catenin cytoplasmic degradation on the micro/nano-textured topography. Our results indicate that Cdc42 is a key modulator of rat MSCs morphology and cytoskeletal reorganization, and that crosstalk between Cdc42 and Wnt/β-catenin signaling though GSK3β regulates MSCs osteogenic differentiation by implant topographical cues.
  
  
  
  Topographical modification at micro- and nanoscale is widely applied to enhance the tissue integration properties of biomaterials. However, the response of bone mesenchymal stem cells (MSCs) to the micro/nano-textured topography and the underlying mechanisms are not well understood. This study shows that the micropitted/nanotubular hierarchical topography produced by etching and anodic oxidation treatment drives fusiform cell morphology, cytoskeletal reorganization as well as better MSCs osteogenic differentiation. The cross-talk between Cdc42 pathway and Wnt/β-catenin pathway though GSK3β modulates the osteoinductive effect of the micro/nano-textured topography on MSCs. This finding sheds light on a novel mechanism involved in micro/nano-textured surface-mediated MSCs osteogenic differentiation and is a major step in the development of new surface modifications aiming to accelerate and enhance the process of osseointegration.
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Disease & Shaanxi Key Laboratory of Oral Disease, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Guangwen
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Prosthodontics, The First Affiliated Hospital of Xinjiang Medical University, Xinjiang 830054, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Song
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Disease & Shaanxi Key Laboratory of Oral Disease, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Mengqi
authors.initials: M
authors.lastname: Shi
authors.affiliation: Department of Stomatology of the 463 Hospital of PLA, Shenyang 110042, China.
authors.forename: Yuanhong
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Stomatology of the 463 Hospital of PLA, Shenyang 110042, China. Electronic address: wangwei19831120@126.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Disease & Shaanxi Key Laboratory of Oral Disease, Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an 710032, China. Electronic address: wqtzym@fmmu.edu.cn.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D048430:Cell Shape; D003599:Cytoskeleton / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000737:chemistry*; D010012:Osteogenesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D013499:Surface Properties; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051176:beta Catenin; D020764:cdc42 GTP-Binding Protein
keywords: Cdc42; MSC; Micro/nano-textured topography; Wnt/beta-catenin pathway