Hematopoetic Stem Cell (HSC) Plasticity Associated With Laser–Induced Bruch’s Membrane Rupture Model of Choroidal Neovascularization

Abstract

Abstract: : Purpose: Repair by adult hematopoietic stem cells (HSC) is well appreciated and these cells are known for their plasticity. We have previously shown that endothelial cells derived from adult HSC participate in CNV following laser rupture of Bruch’s membrane. We used this same model to look for evidence of HSC differentiation into other cells types known to participate in this wounding response. Methods: Lethally irradiated C57Bl6/J mice were stably reconstituted with gfp⁺Sca–1⁺c–kit⁺ bone marrow cells. These chimeric mice were subjected to laser–induced rupture of Bruch’s membrane and euthanized 3 weeks after laser injury. The retina and choroid were examined histologically and immunohistochemically for endothelial, astrocytic, retinal pigment epithelium, macrophage and mural cell morphology and/or markers. Both the neural retinas and the posterior cups in both laser–treated and control eyes were examined. Results: Closure of laser–induced RPE wound was incomplete at time of euthanasia. Gfp⁺ astrocytes were observed in patches concentrated along the edge of the laser wound (and were not evident in the control eye). These cells were bipolar in morphology and closely ensheathed the neovasculature. Numerous gfp⁺ endothelial cells and gfp⁺ macrophages/microglia were evident. Large irregularly shaped gfp⁺ cells were adjacent to the edge of denuded RPE area. A small proportion of these cells had two nuclei, enlarged cell surface area, and less regularly distributed pigment granules resulting in irregularity to the typical mosaic pattern. Conclusions: Postnatal HSC can transdifferentiate into endothelial cells, astrocytes, macrophages/microglia, and RPE in response to acute injury. The transdifferentiated astrocytes closely ensheathed the neovasculature. These studies suggest that hematopoietic stem cells could serve as a therapeutic source for long–term regeneration of injured retina or choroid.

Keywords: choroid: neovascularization • retinal pigment epithelium • age-related macular degeneration