Preclinical studies in eyes with acute ischemia-reperfusion injury or diabetic retinopathy demonstrated that these cells rapidly homed into the damaged retinal vasculature, where they appeared to play a role in tissue repair.14 No long-term ocular or systemic safety issues were noted with intravitreal administration of human BM CD34+ cells in NOD-SCID mice with acute ischemia-reperfusion injury.15 These human cells could be identified incorporated into the mouse retinal vasculature even 6 months following administration. This evidence concerns the gene CD34 and diabetic retinopathy.