DESCRIPTION (provided by applicant): Allogeneic hematopoietic stem and progenitor cell (HSPC) transplantation has the potential to cure hematologic disease. However, many patients do not have an HLA matched donor, and graft-versus-host disease is a significant problem. Autologous patient HSPCs can be genetically corrected to cure the disease, but low yields of autologous HSPCs and ex vivo manipulation cause a loss of "stemness" leading to reduced engraftment. Thus, HSPC production from patient-specific induced pluripotent stem cells (iPSCs) would solve these problems and represent an unlimited cell source. To advance clinical translation of iPSC therapeutics, we propose a novel strategy to expand iPSC-derived HSPCs for hematopoietic transplantation. Specifically, we propose to engineer endothelial cells (ECs) for generation, expansion, and engraftment of putative HSPCs from pigtail macaque (Mn)iPSCs in the clinically relevant nonhuman primate model. In a promising collaboration with Dr. Shahin Rafii, we developed an effective, novel platform to expand macaque CD34+ LT- HSCs up to 25-fold by co-culture with Akt-activated human endothelial cells (E4+ECs). We recently found that iPSC-HSPCs expanded on E4+ECs have high levels of engraftment in NSG mice (up to 50% CD45+ cells). This evidence substantiates our novel approach to alter iPSC-HSPC biology through direct contact culture with angiocrine/hematopoietic signals unique to E4+ECs. The proposed studies will translate these findings to nonhuman primates and thus provide a major step toward producing iPSC-HSPCs with the capacity for hematopoietic reconstitution and correction of genetic diseases.

PUBLIC HEALTH RELEVANCE: The only cure for many genetic blood diseases affecting bone marrow and/or blood cells is a blood stem cell transplant. Only about 25% of patients will have a matched sibling donor. While alternative donors can be used, the risk of side effects from graft-versus-host disease and infectious complications will be substantially increased. Thus, the goal of this project is to develop an alternative stem cell therapy approach using vascular cells to direct a patient's own cells to become blood stem cells. Using the nonhuman primate as a model, reprogrammed nonhuman primate cells are converted into blood stem cells with help of a unique vascular platform. We will also add genetic elements that provide quality control of the blood stem cells and help them take up residence in the bone marrow of the original nonhuman primate, where they will produce all types of blood cells for the lifespan of the donor. Our primary goal is to enable the use of the patients' own cells to safely treat their underlying blood or marrow genetic disease.