Abstract
Abstract: :
Purpose: Bone marrow (BM) reconstitution with exogenous donor cells has been used to demonstrate the involvement of bone marrow–derived endothelial precursor cells (EPC) in ocular neovascularization (NV). Questions have been raised about the effects of BM ablation, especially irradiation, on this process. We employed endogenous label–retaining cells to examine the contribution of an individual's own EPC to ocular NV. Methods: C57Bl6/J mice were given bromodeoxyuridine (BrdU) ad libitum in their water for 10 days, followed by a chase period without BrdU of 3 months. During this chase period, selected animals were euthanized at 2–week intervals and their tissues examined for the presence of BrdU–retaining cells. At the end of the chase period the remaining animals were then subjected to either of our models for laser–induced pre–retinal or choroidal NV. The retinas and posterior poles were then examined by fluorescent microscopy for the presence of BrdU–retaining endothelial cells. Results: Both rapidly–cycling and slowly–cycling cells incorporated BrdU during the pulse period. The degree of BrdU labeling in a variety of tissues decreased by varying degrees with time, depending on the rapidity with which the particular tissue turns over. Little or no label was detected in ocular vasculature 3 months after withdrawl of BrdU. However, laser injury in these animals resulted in robust and extensive incorporation of label–retaining endothelial cells into both retinal and choroidal vasculature, to a degree comparable to prior reports using BM–reconstituted animals. Conclusions: This study shows, for the first time, that endogenous, adult EPC are recruited to areas of laser–induced NV in both the retinal and choroidal vasculature. This process resulted solely from the injury induced in the ocular tissue, as no additional injury (such as irradiation or chemical ablation of bone marrow) was involved. These results confirm earlier findings using transplanted BM, and show that the reconstitution process had no effect on those outcomes.
Keywords: neovascularization • vascular cells • pathology: experimental