title: Mechanism of osteogenic and adipogenic differentiation of tendon stem cells induced by sirtuin 1.
abstract: The aim of the present study was to assess the expression of sirtuin (Sirt)1 in tendon stem cells (TSCs) and to elucidate its association with osteogenic and adipogenic differentiation of TSCs. Reverse-transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analyses were performed to detect Sirt1 mRNA and protein levels in TSCs, respectively. TSCs were positive for Sirt1 expression, which was elevated by Sirt1 activator SRT1720 in a time- and concentration- dependent manner, and decreased by Sirt1 inhibitor EX527. TSCs were treated with SRT1720 and EX527 for various time periods and resulting changes in osteogenic and adipogenic protein markers were analyzed using alizarin red and oil red O staining. According to RT-qPCR and western blot analyses, the associated factors β‑catenin, Runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 were elevated following increases of Sirt1 levels, while CCAAT/enhancer binding protein (CEBP)α and peroxisome proliferator-activated receptor (PPAR)γ were decreased. These results suggested that osteogenic differentiation capacity was enhanced, while adipogenic differentiation capacity declined. Further mechanistic study revealed that phosphoinositide‑3 kinase (PI3K) and AKT were decreased following activation of Sirt1. In conclusion, the present study suggested that Sirt1 promotes the osteogenic differentiation of TSCs through upregulating β‑catenin and Runx2 and inhibits the adipogenic differentiation of TSCs through the PI3K/AKT pathway with downregulation of CEBPα and PPARγ.
authors.affiliation: Department of Orthopaedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China.
authors.forename: Junpeng
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Orthopaedic Surgery, Beijing Tian Tan Hospital, Capital Medical University, Hangzhou, Zhejiang 310003, P.R. China.
authors.forename: Weifeng
authors.initials: W
authors.lastname: Han
authors.affiliation: Department of Orthopaedic Surgery, Wuhan General Hospital of Guangzhou Military Area in Wuhan, Wuhan, Hubei 430070, P.R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China.
authors.forename: Kanglai
authors.initials: K
authors.lastname: Tang
mesh_terms: D050156:Adipogenesis / Q000235:genetics*; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics*; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D008297:Male; D010012:Osteogenesis / Q000235:genetics*; D047495:PPAR gamma / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D056564:Sirtuin 1 / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D013710:Tendons / Q000166:cytology*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D022763:CCAAT-Enhancer-Binding Protein-alpha; D050659:Core Binding Factor Alpha 1 Subunit; D047495:PPAR gamma; D051176:beta Catenin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D056564:Sirtuin 1