Abstract
Despite the clinical significance of post-stroke angiogenesis, a detailed phenotypic analysis of pre-stroke vascular remodeling and post-stroke angiogenesis had not yet been done in a model of focal ischemia. In this study, using BrdU-labeling of proliferating cells and immunofluorescence of pre- and post-stroke rats, we found that, (i) BrdU administered before stroke was incorporated preferentially into the nuclei of endothelial cells lining the lumen of existing blood vessels and newly born neurons in the dentate gyrus but not in the subventricular zone or proliferating microglia, (ii) BrdU injection prior to stroke led to the patchy distribution of the newly incorporated endothelial cells into existing blood vessels of the adult rat brain, (iii) BrdU injection prior to stroke specifically labeled neuronal precursors cells in a region of soft tissue beyond the inhibitory scar, which seems to be permissive to regenerative events, (iv) BrdU injection after stroke led to labeling of endothelial cells crossing or detaching from the disintegrating blood vessels and their incorporation into new blood vessels in the stroke region, scar tissue and the region beyond, (v) BrdU injection after stroke led to specific incorporation of BrdU-positive nuclei into the “pinwheel” architecture of the ventricular epithelium, (vi) blood vessels in remote areas relative to the infarct core and in the contralateral non-lesioned cortex, showed co-labeled BrdU/RECA+ endothelial cells shortly after the BrdU injection, which strongly suggests a bone marrow origin of the endothelial cells. In the damaged cortex, a BrdU/prolyl 4-hydroxylase beta double labeling in the close proximity to collagen IV-labeled basement membrane, suggests that, in addition to bone marrow derived endothelial cells, the disintegrating vascular wall itself could also be a source of proliferating endothelial cells, (vii) By day 28 after stroke, new blood vessels were observed in the perilesional area and the scar tissue region, which is generally considered to be resistant to regenerative events. Finally, (viii) vigorous angiogenesis was also detected in a region of soft tissue, also called “islet of regeneration,” located next to the inhibitory scar.Conclusion: BrdU administered prior to, and after stroke, allows to investigate brain vasculature remodeling in the adult brain.
Highlights
IntroductionResearch on stroke is focused on tissue structure restoration and functional recovery based on revascularization and cell therapy based neuroregeneration
Following recanalization and neuroprotection, research on stroke is focused on tissue structure restoration and functional recovery based on revascularization and cell therapy based neuroregeneration
By BrdU-labeling prior to stroke and immunohistochemistry we found that before injury there is a continuous remodeling of the adult brain vasculature by the incorporation of BrdU into the nuclei of endothelial cells lining the lumen of existing blood vessels in the adult rat cortex
Summary
Research on stroke is focused on tissue structure restoration and functional recovery based on revascularization and cell therapy based neuroregeneration. The molecular and genetic events underlying successful angiogenesis are not fully understood and cannot be exploited for stroke therapy [2,3,4,5]. Endogenous recovery and long-term post-stroke repair mechanisms in the brain rely on angiogenesis, which can be enhanced by release of pro-angiogenic factors in response to, for example, physical exercise in the brain. Few studies have investigated human post-stroke angiogenesis at molecular level. The authors demonstrated an increased synthesis of angiogenic growth factors, such as FGF2, PDGF, VEGF, and their receptors within hours of stroke that correlated with blood vessel growth in the penumbra [8, 9]
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