VEGFA and severe combined immunodeficiency: Transfection of mouse and human pancreatic islet cells mRNA treated with the angiogenic growth factor vascular endothelial growth factor A (VEGF-A) mRNA before transplantation in mice showed to improve engraftment vascularization and β-cell mass after 30 days providing a possible safe and effective approach.60 In addition the possibility of co-transplantation of endothelial progenitor cells coated to human islet surfaces to promote islet vascular engraftment, has been studied in non-obese diabetic/severe combined immunodeficiency mice.