The Effect of Recombinant Human Alpha-1,2-Fucosyltransferase and Alpha-Galactosidase A on the Reduction of Alpha-Gal Expression in the Liver of Transgenic Pigs

Abstract

Genetically modified pigs lacking Galα1 → 3Gal and other immunogenic carbohydrates are considered as the most promising, alternative source of various tissues and organs for human transplantation. Here, we tested the hypothesis that combining the expression of human α1,2-fucosyltransferase (hFUT2) and α-galactosidase A (hGLA) genes would allow for the removal of this specific carbohydrate in porcine transgenic livers. We investigated the expression profile of human α1,2-fucosyltransferase and α-galactosidase A proteins and the amount of Galα1 → 3Gal antigen in the liver of single transgenic hFUT2 (n=5), hGLA (n=5), and double transgenic hFUT2 × hGLA (n=5) pigs. Both human proteins, α1,2-fucosyltransferase and α-galactosidase A, were abundantly expressed in the liver tissue in respective transgenic lines as was revealed by confocal microscopy and Western blotting. The level of Galα1 → 3Gal epitope evaluated by lectin histochemistry and lectin blotting was significantly lower (p<0.05) in all genetically modified livers than that in the control non-transgenic porcine livers. Importantly, the double transgenic line expressed a significantly lower (p<0.05), but still detectable level of this antigen, compared to both single transgenic pigs, as shown by lectin blotting. Histological evaluation of the liver samples stained with haematoxylin and eosin showed no morphological evidence of hepatic abnormalities in all transgenic pigs. Our study indicates that the simultaneous expression of two protective transgenes hFUT2 × hGLA indeed improves the removal of the Galα1 → 3Gal epitope in porcine liver. However, this modification alone is not sufficient enough for complete elimination of this antigen from porcine liver tissue.