title: Hypoxia inhibits cardiomyocyte proliferation in fetal rat hearts via upregulating TIMP-4.
abstract: Maternal hypoxia inhibits cardiomyocyte proliferation in the heart of fetal and neonatal rats. The present study tested the hypothesis that hypoxia has a direct effect inhibiting cardiomyocyte proliferation via upregulating tissue inhibitors of metalloproteinases (TIMP) in fetal rat hearts. Isolated fetal rat hearts and rat embryonic ventricular myocyte H9c2 cells were treated ex vivo with 20% or 1% O(2) for 48 or 24 h, respectively. Hypoxia caused a significant reduction in cardiomyocyte Ki-67 expression and bromodeoxyuridine incorporation in fetal hearts and H9c2 cells. In both fetal hearts and H9c2 cells, hypoxia resulted in a significant decrease in a cell division marker cyclin D2 but an increase in a cell division inhibitor p27. Additionally, hypoxia caused an upregulation of TIMP-3 and TIMP-4 in fetal hearts and H9c2 cells. Knockdown of TIMP-3 in H9c2 cells significantly increased cyclin D2 and Ki-67 and partially blocked the hypoxia-induced inhibition of cyclin D2 and Ki-67 in H9c2 cells. Unlike TIMP-3, TIMP-4 knockdown had no significant effects on the basal levels of cell proliferation but completely abrogated the hypoxia-mediated effects. These findings provide evidence of a novel causal role of TIMP-4 and TIMP-3 in the direct inhibitory effect of hypoxia on cardiomyocyte proliferation in the developing heart.
authors: Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA.
authors: Wenni
authors: W
authors: Tong
authors: Fuxia
authors: F
authors: Xiong
authors: Yong
authors: Y
authors: Li
authors: Lubo
authors: L
authors: Zhang
mesh_terms: D000818:Animals; D000963:Antimetabolites; D015153:Blotting, Western; D001973:Bromodeoxyuridine; D002460:Cell Line; D049109:Cell Proliferation; D048429:Cell Size; D056742:Cyclin D2 / Q000096:biosynthesis / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000096:biosynthesis; D005260:Female; D005318:Fetal Heart / Q000502:physiology*; D005311:Fetal Hypoxia / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D019394:Ki-67 Antigen / Q000096:biosynthesis; D032383:Myocytes, Cardiac / Q000502:physiology*; D011247:Pregnancy; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics / Q000502:physiology; D019714:Tissue Inhibitor of Metalloproteinases / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation / Q000502:physiology; D000097792:Tissue Inhibitor of Metalloproteinase-4
chemical_list: D000963:Antimetabolites; D001973:Bromodeoxyuridine; D056742:Cyclin D2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019394:Ki-67 Antigen; D034741:RNA, Small Interfering; D019717:Tissue Inhibitor of Metalloproteinase-3; D019714:Tissue Inhibitor of Metalloproteinases; D000097792:Tissue Inhibitor of Metalloproteinase-4