Abstract
Abstract: :
Purpose:We have shown previously that adult bone marrow derived lineage negative hematopoietic stem cells target the retinal vasculature and exert vasculo– and neurotrophic rescue effects. However, the specific cell type(s) within this heterogeneous population mediating the observed effects remains unknown. We report here the use of a single marker to positively select a population of cells that targets the retinal vasculature. Methods:An antibody against CD44 (hyaluronic acid receptor) was used to label whole bone marrow from mice that express GFP in all nucleated cells. Flow cytometry revealed distinct CD44HI and CD44LO expressing groups within mouse bone marrow. Using FACS, these two CD44+ populations were sorted and injected intravitreally into P5 mice. Results:CD44HI cells were strongly represented in the lineage negative population used in prior experiments; these cells were significantly reduced in number or completely absent in lineage positive and other, non–targeting, control populations. CD44HI cells, at varying timepoints after injection, were observed to target the retinal vasculature and differentiate in a perivascular localization, while the CD44LO cells were either absent from the retina, or not differentiated nor targeted to the vasculature. Further analysis of CD44HI cells shows that they have blast–like characteristics based on light scattering properties and express CD11b (Mac–1), indicating a possible myeloid origin. Conclusions: We demonstrate the feasibility of using positive selection as a strategy for preparing populations of adult bone marrow derived stem cells that target to retinal vasculature. Intravitreal injection exposes cells to significant levels of hyaluronic acid, making CD44 a reasonable candidate receptor that mediates cell survival and/or function in this environment. Functional and trophic properties of this cell population are currently under investigation.
Keywords: retinal neovascularization • retina • vascular cells