title: In vitro and in vivo proliferation, differentiation and migration of cardiac endothelial progenitor cells (SCA1+/CD31+ side-population cells).
abstract: BACKGROUND
  Side-population (SP) cells are a select population identified by a capacity to efflux Hoechst dye and are enriched for stem/progenitor cell activity. Previous studies suggested that cardiac SP (CSP) cells could be divided into SCA1(+)/CD31(-) and SCA1(+)/CD31(+) CSP cells. SCA1(+)/CD31(-) CSP cells have been shown to be cardiac stem/progenitor cells. However, SCA1(+)/CD31(+) CSP cells have not been fully characterized.
  
  
  OBJECTIVE
  The aim of the present study was to characterize SCA1(+)/CD31(+) CSP cells in the adult mouse heart, and investigate their abilities to proliferate, differentiate, vascularize and migrate in vitro and in vivo.
  
  
  RESULTS
  Using fluorescence-activated cell sorting (FACS), RT-PCR, and assays of cell proliferation, differentiation and migration, and a murine model of myocardial infarction (MI), we showed that SCA1(+)/CD31(+) CSP cells express stem cell and endothelial-specific genes, and reside in the blood vessels. These cells were able to proliferate, differentiate, migrate and vascularize in vitro and in vivo. After MI, SDF-1α and CXCR4 were up-regulated in the damaged myocardium and on SCA1(+)/CD31(+) CSP cells, respectively. Our results further showed that SDF-1α induced migration of these cells in vitro. Importantly, we found that SCA1(+)/CD31(+) CSP cells could migrate into the ischemic region from the non-ischemic area within the myocardium and form a vascular tube-like structure after MI.
  
  
  CONCLUSIONS
  Based on the gene expression profile, localization of SCA1(+)/CD31(+) CSP cells, and their ability to proliferate, differentiate, migrate and vascularize in vitro and in vivo, we postulate that SCA1(+)/CD31(+) CSP cells may represent endothelial progenitor cells in the mouse heart.
authors: Center for Vascular Research, University of New South Wales, Sydney, NSW, Australia.
authors: S X
authors: SX
authors: Liang
authors: L M
authors: LM
authors: Khachigian
authors: Z
authors: Z
authors: Ahmadi
authors: M
authors: M
authors: Yang
authors: S
authors: S
authors: Liu
authors: B H
authors: BH
authors: Chong