Evaluation of ex vivo produced endothelial progenitor cells for autologous transplantation in primates

Background: Autologous transplantation of endothelial progenitor cells (EPCs) is a promising therapeutic approach in the treatment of various vascular diseases. We previously reported a two-step culture system for scalable generation of human EPCs derived from cord blood CD34(+) cells ex vivo. Here, we now apply this culture system to expand and differentiate human and nonhuman primate EPCs from mobilized peripheral blood (PB) CD34(+) cells for the therapeutic potential of autologous transplantation. Methods: The human and nonhuman primate EPCs from mobilized PB CD34(+) cells were cultured according to our previously reported system. The generated adherent cells were then characterized by the morphology, surface markers, nitric oxide (NO)/endothelial NO synthase (eNOS) levels and Dil-acetylated low-density lipoprotein (Dil-Ac-LDL) uptake/fluorescein isothiocyanate (FITC)-lectin binding actives. Furthermore, the efficacy and safety studies were performed by autologous transplantation via hepatic portal vein injection in a nonhuman primate model with acute liver sinusoidal endothelial cell injury. Results: The mobilized PB CD34(+) cells from both human and nonhuman primate were efficiently expanded and differentiated. Over 2 x 108 adherent cells were generated from 20 mL mobilized primate PB (1.51 x 10(6) +/- 3.39 x 10(5) CD34(+) cells) by 36-day culture and more than 80% of the produced cells were identified as EPCs/endothelial cells (ECs). In the autologous transplant model, the injected EPC/ECs from nonhuman primate PB were scattered in the intercellular spaces of hepatocytes at the hepatic tissues 14 days post-transplantation, indicating successful migration and reconstitution in the liver structure as the functional EPCs/ECs. Conclusions: We successfully applied our previous two-step culture system for the generation of primate EPCs from mobilized PB CD34(+) cells, evaluated the phenotypes ex vivo, and transplanted autologous EPCs/ECs in a nonhuman primate model. Our study indicates that it may be possible for these ex-vivo high-efficient expanded EPCs to be used in clinical cell therapy.