Bone Marrow-Derived Endothelial Progenitor Cells Participate in Cerebral Neovascularization After Focal Cerebral Ischemia in the Adult Mouse

Abstract

Abstract-We investigated whether circulating endothelial progenitor cells contribute to neovascularization after stroke.Donor bone marrow cells obtained from transgenic mice constitutively expressing ␤-galactosidase transcriptionally regulated by an endothelial-specific promoter, Tie2, were injected into adult mice. Focal cerebral ischemia was induced by embolic middle cerebral artery (MCA) occlusion and changes of cerebral blood flow (CBF) were measured by perfusion-weighted magnetic resonance imaging (MRI). Laser scanning confocal microscopy (LSCM), immunohistochemistry and X-gal staining were performed. Perfusion-weighted MRI demonstrated increases in CBF around the boundary of an infarct area 1 month after ischemia. Morphological and 3-dimensional image analyses revealed enlarged and thin-walled blood vessels with sprouting or intussusception at the boundary of the ischemic lesion, which closely corresponded to elevated CBF areas detected on perfusion-weighted MRI, indicating the presence of neovascularization. X-gal and double immunostaining demonstrated that Tie2-lacZ-positive cells incorporated into sites of neovascularization at the border of the infarct, and these cells exhibited an endothelial antigenic marker (von Willebrand factor). In addition, bone marrow recipient mice without ischemia showed incorporation of Tie2-lacZ-expressing cells into vessels of the choroid plexus. These data suggest that formation of new blood vessels in the adult brain after stroke is not restricted to angiogenesis but also involves vasculogenesis and that circulating endothelial progenitor cells from bone marrow contribute to the vascular substructure of the choroid plexus. Key Words: bone marrow Ⅲ endothelial progenitor cells Ⅲ neovascularization Ⅲ cerebral ischemia Ⅲ Tie2 I n the early embryogenesis, the vascular system develops from vasculogenesis in which angioblasts differentiate into endothelial cells to form a primitive capillary network, whereas angiogenesis, the sprouting of capillaries from preexisting blood vessels, is involved in the late stage of embryogenesis and in the adult. 1 Angioblast-like circulating endothelial progenitor cells are present in the peripheral blood and have been isolated from adult animals. 2,3 Injection of circulating endothelial progenitor cells into animals with hindlimb or myocardial ischemia results in incorporation of circulating endothelial progenitor cells into neovasculature at the site of ischemia, suggesting that circulating endothelial progenitor cells contribute to formation of new blood vessels in the adult tissue. 4 The endothelial cells of cerebral capillaries differ functionally and morphologically from those of noncerebral capillaries. 5,6 During embryonic development, the cerebral vascular system originates from the perineural plexus when vascular sprouts invade the proliferating neuroectoderm, indicating that the cerebral vascular system is primarily developed by angiogenesis and not by vasculogenesis. 7 The cerebral endothelial cells are linked by complex tight junc...

A Neurovascular Niche for Neurogenesis after Stroke

“…Stroke damage adjacent to the SVZ induces neuroblast migration from GFAPexpressing progenitor cells (Yamashita et al, 2006). Alternatively, after cardiac, limb, or brain ischemia, bone marrowderived cells or EPCs are mobilized into the peripheral circulation, in which they proliferate and give rise to local endothelial cells, macrophage or microglial cells after stroke, and pericytes (Zhang et al, 2002;Hess et al, 2004;Kokovay et al, 2006). Circulating EPCs may also give rise to new neurons after stroke (Hess et al, 2004).…”

“…However, ischemia mobilizes bone marrow-derived endothelial precursor cells (EPCs) that incorporate into blood vessels after ischemia (Zhang et al, 2002;Hristov and Weber, 2004) and may form neurons in situ near stroke (Hess et al, 2004). Local neurogenesis from the SVZ to the striatum derives from a GFAP expression progenitor (Yamashita et al, 2006).…”

Transplantation of Mouse Embryonic Stem Cells into the Cochlea of an Auditory-Neuropathy Animal Model: Effects of Timing after Injury

“…Accumulating evidence suggests that bone-marrow-derived vascular progenitor cells are able to mobilize into the peripheral circulation and contribute to neovascularization in response to various pathological conditions including cerebral ischemia (Zhang et al 2002) and myocardial infarct ). Unfortunately, we were unable to determine the precise origins of these endothelial cells in the present study.…”

Therapeutic Potential of Endothelial Progenitor Cells in Cardiovascular Diseases

“…9,10,21,30,33,41,76,77 For example, the bone marrowderived mononuclear cells (BM-MNCs), containing also the EPC population, home to ischemic myocardium, 12,21,60 brain, 78 and hind limb, 10 homing of CD34 ϩ cells was seen in patients with myocardial infarction 12,60 or hind limb 43 ischemia. Furthermore, in patients with inoperable coronary artery disease, mobilization and homing of EPCs to the ischemic myocardium increased up to 9 weeks after VEGF gene transfer, in parallel with increase in circulating levels of VEGF, 11 and in patients with critical limb ischemia VEGF gene transfer led to marked increase in CEPCs.…”