Involvement of Bone Marrow-Derived Vascular Progenitor Cells in Neovascularization During Formation of the Corpus Luteum in Mice1

Neovascularization is necessary for formation of the corpus luteum (CL) and includes angiogenesis and vasculogenesis. Vasculogenesis is the formation of new blood vessels by bone marrow-derived endothelial progenitor cells. Here we investi-gated whether vasculogenesis occurs in neovascularization during CL formation. Mice transplanted with bone marrow from transgenic mice expressing green fluorescent protein (GFP) were injected with equine chorionic gonadotropin and human chorionic gonadotropin (hCG) to induce ovulation and subse-quent CL formation. Immunohistochemistry was performed on the ovaries obtained before hCG injection and at 6, 12, and 24 h after hCG injection using antibodies for CD34 or CD31 (an endothelial cell marker), platelet-derived growth factor receptor beta (PDGFR-beta, a pericyte marker), F4/80 (a macrophag