Period 2 is essential to maintain early endothelial progenitor cell function in vitro and angiogenesis after myocardial infarction in mice

• Published in: Journal of cellular and molecular medicine 2014-05, Vol.18 (5), p.907-918
• Main Authors: Sun, Yuan‐Yuan, Bai, Wen‐Wu, Wang, Bo, Lu, Xiao‐Ting, Xing, Yi‐Fan, Cheng, Wen, Liu, Xiao‐Qiong, Zhao, Yu‐Xia
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; AKT protein; Angiogenesis; Animals; Apoptosis; Bone marrow; Cardiac function; Cardiovascular disease; Cardiovascular diseases; Cell Adhesion; Cell Count; Cell Movement; Cell Proliferation; Cells, Cultured; Chemokines; Circadian rhythm; Circadian rhythms; Clinical trials; CXCR4 protein; endothelial progenitor cells; Endothelial Progenitor Cells - cytology; Flow cytometry; Forkhead protein; Forkhead Transcription Factors - metabolism; Heart attacks; Heart Function Tests; Ischemia; Male; Mice; Mice, Inbred C57BL; Myocardial infarction; Myocardial Infarction - pathology; Myocardial Infarction - physiopathology; Myocardial Infarction - therapy; Myocardium; Neovascularization, Physiologic; Original; period 2; Period 2 protein; Period Circadian Proteins - deficiency; Period Circadian Proteins - metabolism; Phosphatidylinositol 3-Kinases - metabolism; Progenitor cells; Protein Binding; Proto-Oncogene Proteins c-akt - metabolism; Receptors, CXCR4 - metabolism; Stem Cell Transplantation; Studies; Survival Analysis; Vascular endothelial growth factor; Vascularization
• ISSN: 1582-1838; 1582-4934
• DOI: 10.1111/jcmm.12241

Cellular therapeutic neovascularization has been successfully performed in clinical trials for patients with ischaemia diseases. Despite the vast knowledge of cardiovascular disease and circadian biology, the role of the circadian clock in regulating angiogenesis in myocardial infarction (MI) remains poorly understood. In this study, we aimed to investigate the role and underlying mechanisms of Period 2 (Per2) in endothelial progenitor cell (EPC) function. Flow cytometry revealed lower circulating EPC proportion in per2−/− than in wild‐type (WT) mice. PER2 was abundantly expressed in early EPCs in mice. In vitro, EPCs from per2−/− mice showed impaired proliferation, migration, tube formation and adhesion. Western blot analysis demonstrated inhibited PI3k/Akt/FoxO signalling and reduced C‐X‐C chemokine receptor type 4 (CXCR4) protein level in EPCs of per2−/− mice. The impaired proliferation was blocked by activated PI3K/Akt/FoxO signalling. Direct interaction of CXCR4 and PER2 was detected in WT EPCs. To further study the effect of per2 on in vivo EPC survival and angiogenesis, we injected saline or DiI‐labelled WT or per2−/− EPC intramyocardially into mice with induced MI. Per2−/− reduced the retention of transplanted EPCs in the myocardium, which was associated with significantly reduced DiI expression in the myocardium of MI mice. Decreased angiogenesis in the myocardium of per2−/− EPC‐treated mice coincided with decreased LV function and increased infarct size in the myocardium. Per2 may be a key factor in maintaining EPC function in vitro and in therapeutic angiogenesis in vivo.