Reprogramming technologies allow for defining cell identity a la carte. Whereas reprogramming to induced Pluripotent Stem Cells (iPSCs) have attracted most of the attention due to their potential for regenerative medicine and disease modeling applications, while avoiding the need for embryonic material required for generating Embryonic Stem Cell (ESC) lines, iPSC generation and their further differentiation to specific cell lineages and tissues do not represent the sole reprogramming strategy available. Indeed, the use of iPSCs, per se, possesses a priori the inherent risk of tumor formation due to residual pluripotent cell transplantation. In addition, the long time required for iPSC reprogramming and further differentiation make iPSCs prone to accumulation of random somatic mutations that, whereas mostly silenced and irrelevant, might in some cases provoke cellular anomalies leading to malfunction or carcinogenesis. Among all different lineages that can be derived from iPSCs and ESCs, vascular lineages present perhaps the broadest catalogue of potential clinical use. Vascularization, or the generation of new vessels, does not only provide an alternative for the treatment of, for example diabetic patients in where the vasculature is being destroyed, but also extends to a number of vascular diseases, and most importantly, represents the cornerstone for any traumatic injury treatment as well as for cardiovascular disease and infarction. Vascularization will, in this case, allow for replenishing oxygen and nutrient supplies to the injured area. This in turn allows for healing and avoids necrosis, which so often leads to amputation procedures.
Our proposal therefore focuses on generating functional vascular cells for human use and their testing in different ischemia and infarction models. We have focused first on the deciphering of a methodology for deriving vascular cells from both iPSCs and ESCs with high efficiencies. So far, our results indicate that vascular cells derived from pluripotent cells are functional and do not lead to tumors upon transplantation. In addition, our differentiation methodologies do not seemingly compromise the human genome. Therefore, this represents a safe approach for clinical translation. To avoid any potential problem that might arise in the long term, we have additionally identified a set of different conditions that allow us to directly convert human skin cells into functional vascular cells. In this case, the generated vascular cells do not transition through an iPSC state and are therefore safer by definition. To further provide a safe cellular product for clinical applications we have furthermore translated all our methodologies to non-integrative gene delivery systems that further secure and contribute to the absence of genetic mutations in the converted vascular cells. To date, we have been able to produce high quality vascular cells in a large-scale manner and are now ready for initiating our safety studies in injury models of myocardial infarction and limb ischemia.