Mechanisms that govern interspecies chimeric hearts

About This Grant

The only curative therapy for end-stage heart disease is heart transplantation. Millions of patients (worldwide) could benefit from such therapy but are not eligible for transplantation due to limited donor organ availability, thus, there is an urgent need to develop alternative organ sources. Genetically modified pigs as an organ source for xenotransplantation has met with limited success. An alternative is to engineer a porcine model that is deficient for key developmental regulatory factors, so that the target organ (i.e. heart) is disabled. We hypothesize that these mutant porcine embryonic hosts provide a developmental “niche”, for the healthy donor stem cells to populate and generate a donor-derived organ. Using this strategy, our lab was the first to engineer intraspecies (pig-pig) vasculature in an ETV2 null pig (Nature Biotechnology and Nature Cell Biology) and intraspecies (pig-pig) muscle in a MYOD/MYF5/MYF6 null pig embryo (Nature Biomedical Engineering). These studies were innovative steps forward for the field as they demonstrated for the first time that allogeneic (pig-pig) organs could be engineered in the absence of immunosuppression. We further engineered human vasculature and separately human skeletal muscle in gene edited pigs (thereby rescuing the respective null phenotypes) but these interspecies chimeras were less efficient and novel methods are required to interrogate the barriers that prevent efficient chimerism. We have recently developed a novel aggregation-based culture system that extends porcine embryo development through gastrulation, providing the first ever opportunity to study lineage allocation and interspecies cell interactions without reliance on surrogates. In these studies, we will use our high throughput system to interrogate interspecies cell competition, the advantage of a cardiac specific niche, as well as the production of a macaque heart within a lineage disabled porcine embryo. To examine our hypotheses, we will address the following specific aims: Specific Aim #1: Establish and optimize an in vitro long-term culture platform that supports the development of both wild-type and NKX2-5 null porcine embryos up to early organogenesis; Specific Aim #2: Generate and characterize nonhuman primate (macaque)–pig chimeric embryos using NKX2-5 null porcine hosts; and Specific Aim #3: Generate and characterize a macaque heart in the NKX2-5 null porcine host in vivo. In these studies, we will use state-of-the-art gene technologies and macaque GFP-labeled stem cell populations to engineer a nonhuman primate heart in a gene edited pig. This nonhuman primate large animal model will be an important resource for regenerative medicine and will serve as a platform for generating personalized humanized porcine models. This strategy has the capacity to have a profound impact on the development of emerging therapies for endstage heart failure, transplantation, and the democratization of organ availability for our patients.