title: Role of the ERK1/2 Signaling Pathway in Osteogenesis of Rat Tendon-Derived Stem Cells in Normoxic and Hypoxic Cultures.
abstract: BACKGROUND
  Ectopic ossification and increased vascularization are two common phenomena in the chronic tendinopathic tendon. The increased vascularization usually leads to an elevated local oxygen tension which is one of micro-environments that can influence differentiate status of stem cells.
  
  
  OBJECTIVE
  This study aimed to investigate the osteogenesis capacity of rat tendon-derived stem cells TDSCs (rTDSCs) in normoxic and hypoxic cultures, and to study the role of ERK1/2 signaling pathway in this process.
  
  
  METHODS
  rTDSCs were subjected to osteogenesis inductive culture in hypoxic (3% O2) and normoxic (20% O2) conditions. The inhibitor U0126 was added along with culture medium to determine the role of ERK1/2 signaling pathway. Cell viability, cell proliferation, alizarin red staining, alkaline phosphatase (AKP) activity, gene expression (ALP, osteocalcin, collagen I and RUNX2) and protein expression (p-ERK1/2 and RUNX2) of osteogenic-cultured rTSDCs were analyzed in this study.
  
  
  RESULTS
  Hypoxic and normoxic culture had no effects on cell viability of rTDSCs, whereas the proliferation potential of rTDSCs was significantly increased in hypoxic culture. The osteogenesis capacity of rTDSCs in normoxic culture was significantly promoted compared with hypoxic culture, which was reflected by an increased alizarin red staining intensity, an elevated ALP activity, and the up-regulated gene (ALP, osteocalcin, collagen I and RUNX2) or protein (RUNX2) expression of osteogenic makers. However, the osteogenesis capacity of rTDSCs in both hypoxic and normoxic cultures was attenuated by the inhibitor U0126.
  
  
  CONCLUSIONS
  Normoxic culture promotes osteogenic differentiation of rTDSCs compared with the hypoxic culture, and the ERK1/2 signaling pathway is involved in this process.
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Pei
authors: P
authors: Li
authors: 2. Department of Orthopedic Surgery, Xinqiao Hospital, Third Military Medical University, Chongqing, 400038, China.
authors: Yuan
authors: Y
authors: Xu
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Yibo
authors: Y
authors: Gan
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Lei
authors: L
authors: Song
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Chengmin
authors: C
authors: Zhang
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Liyuan
authors: L
authors: Wang
authors: 1. Department of Orthopedic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China;
authors: Qiang
authors: Q
authors: Zhou
mesh_terms: D000469:Alkaline Phosphatase / Q000096:biosynthesis; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D015687:Cell Hypoxia / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D024042:Collagen Type I / Q000096:biosynthesis; D005786:Gene Expression Regulation; D006801:Humans; D020935:MAP Kinase Signaling System / Q000235:genetics; D059630:Mesenchymal Stem Cells / Q000166:cytology; D015675:Osteocalcin / Q000096:biosynthesis; D010012:Osteogenesis / Q000235:genetics*; D051381:Rats; D052256:Tendinopathy / Q000235:genetics* / Q000473:pathology; D013710:Tendons / Q000254:growth & development / Q000473:pathology*
chemical_list: D024042:Collagen Type I; D015675:Osteocalcin; D000469:Alkaline Phosphatase
keywords: hypoxic; normoxic; osteogenesis.; tendinopathy; tendon-derived stem cells