Estrogen-Mediated Endothelial Progenitor Cell Biology and Kinetics For Physiological Postnatal Vasculogenesis

Abstract

Abstract-Estrogen has been demonstrated to promote therapeutic reendothelialization after vascular injury by bone marrow (BM)-derived endothelial progenitor cell (EPC) mobilization and phenotypic modulation. We investigated the primary hypothesis that estrogen regulates physiological postnatal vasculogenesis by modulating bioactivity of BMderived EPCs through the estrogen receptor (ER), in cyclic hormonally regulated endometrial neovascularization. Cultured human EPCs from peripheral blood mononuclear cells (PB-MNCs) disclosed consistent gene expression of ER ␣ as well as downregulated gene expressions of ER ␤. Under the physiological concentrations of estrogen (17␤-estradiol, E2), proliferation and migration were stimulated, whereas apoptosis was inhibited on day 7 cultured EPCs. These estrogen-induced activities were blocked by the receptor antagonist, ICI182,780 (ICI). In BM transplanted (BMT) mice with ovariectomy (OVX) from transgenic mice overexpressing ␤-galactosidase (lacZ) regulated by an endothelial specific Tie-2 promoter (Tie-2/lacZ/BM), the uterus demonstrated a significant increase in BM-derived EPCs (lacZ expressing cells) incorporated into neovasculatures detected by CD31 immunohistochemistry after E2 administration. The BM-derived EPCs that were incorporated into the uterus dominantly expressed ER ␣, rather than ER ␤ in BMT mice from BM of transgenic mice overexpressing EGFP regulated by Tie-2 promoter with OVX (Tie-2/EGFP/BMT/OVX) by ERs fluorescence immunohistochemistry. An in vitro assay for colony forming activity as well as flow cytometry for CD133, CD34, KDR, and VE-cadherin, using human PB-MNCs at 5 stages of the female menstrual-cycle (early-proliferative, pre-ovulatory, post-ovulatory, mid-luteal, late-luteal), revealed cycle-specific regulation of EPC kinetics. These findings demonstrate that physiological postnatal vasculogenesis involves cyclic, E2-regulated bioactivity of BM-derived EPCs, predominantly through the ER␣. (Circ Res. 2007;101:598-606.)Key Words: estrogen Ⅲ endothelial progenitor cell Ⅲ estrogen receptor Ⅲ physiological postnatal vasculogenesis I n the female reproductive system, neovascularization is a recurring phenomemnon controlled by cyclic development of transient structure and cyclical repair of damaged tissue. 1 The ovarian sex steroid hormones, estrogen and progesterone, are primarily uterotropic and control the cyclical patterns of uterine cell proliferation and vascular growth that occur throughout the nonpregnant menstrual cycle. Given the synchronized nature of neovascularization in this cyclical mannter, it is assumed that angiogenic growth factor expression is induced by steroid hormones and regulates blood vessel formation in reproductive organogenesis. [2][3][4][5] Despite clinical evidence for the significant role of steroid hormones in endometrial neovascularization, further investigation using in vitro and in vivo experiments have yielded inconclusive results regarding pathophysiological mechanisms in angiogenesis. 6 -10 Moreover, estrogen has been sh...

Regulation of endometrial vascular remodelling: role of the vascular endothelial growth factor family and the angiopoietin–TIE signalling system

“…There is also evidence illustrating an important role for endothelial progenitor cells in endometrial angiogenesis, with several studies demonstrating the presence of donor-derived endothelial cells within the uterus after bone marrow transplant from either male mice or transgenic mice with endothelial cell-specific mutations (Asahara et al 1999, Masuda et al 2007, Mints et al 2008. In a human study, endothelial cells with an XY genotype were detected in the endometrium of a women receiving an allogenic transplant with bone marrow derived from a male (Mints et al 2008).…”

“…The extent of endothelial progenitor cell incorporation is influenced by circulating hormones. In a study by Masuda et al (2007), ovariectomised mice received a bone marrow transplant from transgenic mice expressing b-galactosidase under the regulation of the endothelial cell-specific promoter TIE2. In these animals, oestrogen, but not progesterone, treatment caused a significant increase in bone marrow-derived endothelial progenitor cells incorporated into the growing uterine vasculature.…”

Sexual dimorphism in cancer

“…Sex steroids have an impact on stem cell populations of various types. Estrogens enhance self renewal of embryonic stem cells 29 , promote endothelial progenitor cells 30 and, during pregnancy, contribute to the expansion of hematopoietic stem cell populations 31 .…”

“…Estrogens have a well established pro-angiogenesis function, best known in the endometrium during the female reproductive cycle, which is mediated by enhancement of endothelial cell proliferation and migration 30,53 . This is mediated by diffusible factors like PAF 54 and VEGF 55 , which are frequently secreted by cancer cells in response to estrogens.…”

Alcohol Consumption Negates Estrogen-mediated Myocardial Repair in Ovariectomized Mice by Inhibiting Endothelial Progenitor Cell Mobilization and Function

“…Apart from the local induction of endothelial growth factors, the underlying proposed mechanisms of E2 also include the ability of E2 to mobilize EPCs, which can incorporate into denuded carotid arteries, thereby participating in the regeneration of the neo-endothelium (3,4). We and others (3,14,16) have also shown that E2-mediated enhancement in the recovery from AMI involves ischemic cardiac neovascularization, reduction in fibrosis, and enhanced expression of angiogenic growth factors in OVX mice receiving estradiol that is, at least in part, due to mechanisms involving eNOS and/or MMP9-dependent EPC mobilization, homing, and inhibition of apoptosis. In another published study, using BM-transplantation models, we have demonstrated that following E2 supplementation, EPC mobilization and EPC-mediated cardiac repair is depressed significantly in mice lacking either ER␣ or ER␤ (15).…”