Formation Of Exogenic Pituitary, Eye Lens, And Midbrain Dopaminergic Neurons In Pigs Via Blastocyst Complementation

Abstract

Thousands of patients die waiting for an organ transplant every year, while those that do obtain a transplant may run into complications such as Graft vs. Host disease. One reason for this is that there is a lack of organ donors who can biologically match specific patients. A solution to this problem would be to generate human organs in pigs using the patient’s own cells, and then to transplant these organs once they are grown. Blastocyst complementation is the perfect method to do this as it is involves injecting donor cells into a pig embryo, which can then contribute to growing to an organ in the pig if the pig’s own genetic code does not allow its own cells to form that very same tissue. Blastocyst complementation was previously done using PITX3 KO pig embryos and human induced pluripotent stem cells (hiPSCs) or human umbilical cord blood stem cells (hUCBSCs) in the Low Lab to create exogenic pituitaries, eye lenses, and midbrain dopaminergic neurons made of human cells. Human Nuclear Antigen staining of pituitaries in this study show positive signals. The human cells failed to integrate into the eye lens and midbrain dopamine neurons, despite the fact that the dopaminergic neurons were complemented and able to grow into functional cells. This failure could have been due to either incorrect stage-matching of donor cells to the host embryo, or knocking out a gene that was only partially responsible for cellular development. A second gene, LMX1A, was therefore knocked out together with PITX3 to try and get complementation with GFP-labelled porcine blastomeres. This study shows that the eye lenses of these embryos are similar in terms of a round, circular morphology to that of wild-type pig lenses. GFP is found to be present in the pituitary of a PITX3/LMX1A KO embryo injected with porcine blastomeres, meaning the donor cells successfully integrated into the organ.