title: Hypoxia inhibits mesenchymal stem cell proliferation through HIF1α-dependent regulation of P27.
abstract: Stem cells have inherent properties of self-renewal and differentiation. High percentage of transplanted stem cells (95 %) die into ischemic heart due to unfavorable environment where in hypoxia considered among major contributing factors. Hypoxia inducible factor-1 α is a well-known transcription factor which robustly induced during hypoxia and an essential factor for adaptation under lower oxygen tension. The effects of hypoxia onto stem cells and its cell cycle are poorly understood. Mesenchymal stem cells were isolated from adult male Fischer-344 rats bone marrow and kept under hypoxia (1 % O2). Cell survival and proliferation were studied using MTT and CFSE assay which showed reduced proliferation rate with an arrest in G0/G1 phase of cell cycle using flow cytometry. Western blot analysis revealed an increase in expressions of HIF-1α along with P53, a tumor suppressor gene. Cyclin-dependent kinase inhibitor (CDKI), p27 was significantly increased, in concordance with the findings, cyclin D1 was also reduced under hypoxia and forestalling S phase entry. In addition, loss of function study with HIF-1α knockdown revealed progression of cell cycle even under hypoxia. Knocking down p27 abrogated the hypoxia-induced G1 checkpoint, suggesting a key regulator of G1/S transition in hypoxic cells. Hypoxia could cause HIF-1α-dependent increase in the expression of p27 leading to cell cycle arrest in G0/G1 phase. The demonstration of the molecular mechanism of hypoxia-induced G1/S regulation provides insight into a fundamental response of stem cells to low oxygen tension.
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 4110 Libra Drive, Bld 20., Orlando, FL, 32816, USA. sanjay.kumar@ucf.edu.|Department of Biochemistry, Central University of Haryana, Mahendergarh, Haryana, India. sanjay.kumar@ucf.edu.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Department of Biochemistry, M.G.M Medical College, Indore, India.
authors.forename: Meenal
authors.initials: M
authors.lastname: Vaidya
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D016193:G1 Phase; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D016192:Resting Phase, Cell Cycle
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27
keywords: G0/G1 arrest; HIF1α; Hypoxia; Mesenchymal stem cell; P27