Previous cross-species studies using human CD34+ cells in mice have not used as extensive systemic immunosuppression as was used in this study, because these prior studies were short-term studies.33,34 These earlier studies have shown retinal vascular incorporation and transretinal migration of intravitreally injected human CD34+ cells in animal models of diabetic retinopathy or laser retinal injury. This evidence concerns the gene CD34 and diabetic retinopathy.