Isolated, mammalian, bone marrow-derived, lineage negative hematopoietic
stem cell populations (Lin.sup.- HSC) contain endothelial progenitor
cells (EPC) capable of forming retinal blood vessels. At least about 50%
of the cells in the isolated Lin.sup.- HSC population include cell
surface markers for CD31 and c-kit. Up to about 8% of the cells can
include the Sca-1 cell marker, and up to about 4% of the cells can
include the Flk-1/KDR marker. The isolated Lin.sup.- HSC populations of
the present invention are useful for treatment of ocular vascular
diseases. The isolated Lin.sup.- HSC populations that have been
transfected with therapeutically useful genes are also provided, which
are useful for delivering genes to the eye for cell-based gene therapy.