Human Stem Cell Complementation in PITX3 Null Porcine Blastocysts: Lens Development

Abstract

A major goal of research in stem cell biology and regenerative medicine is the generation of organs, tissues and cells for replacement therapy. Differentiation of phenotype-specific cell types can be achieved from Embryonic stem cells (ESCs), induced Pluripotent stem cells (iPSCs) or via Direct reprogramming. However, the generation of entire functional organs and completely reprogrammed authentic cells is yet to be achieved. Blastocyst complementation utilizing human pluripotent stem cells (hPSCs) is an approach that can potentially generate whole organs. We utilized an interspecies complementation strategy by injecting hPSCs into porcine parthenogenetic blastocysts. Through this, we were able to achieve successful incorporation of human stem cells into the inner cell mass (ICM) of the parthenogenetic blastocysts, and ultimately in the porcine parthenote fetuses, when the chimeric blastocysts were implanted into surrogate pigs. A previous study reported successful complementation of normal porcine blastomeres in the blastocysts of an organogenesis-disabled pig, leading to the development of a completely donor-derived organ in that pig. We wanted to determine if a similar approach could be achieved by complementing human stem cells in a porcine blastocyst lacking a gene for lens development and generation of dopaminergic neurons (Pitx3). hPSCs successfully incorporated into Pitx3 deficient blastocysts and resulted in the presence of lens-like fibers in the eyes of complemented fetuses. Though more analyses on the fetuses are yet to be performed to confirm successful complementation of human cells in the Pitx3-/- pigs, initial analyses provide promising results for potential generation of human-derived cells or organs in an organogenesis-disabled pig. Thus, inter-species blastocyst complementation approach using hPSCs can provide more opportunities for safe cell/organ replacement therapy.