Advanced bioartificial organs: genetically modified pig liver as a promising bridge for human liver failure

In a groundbreaking study recently published in Nature, Kai-Shan Tao and colleagues achieved the first successful heterotopic pigto-human liver xenotransplantation using a gene-edited Bama miniature pig carrying six targeted genetic modifications designed to suppress immunologic rejection and thrombosis. 1 The ability of the graft to maintain bile secretion, albumin synthesis, and histological integrity over 10 days in a brain-dead human recipient underscores the potential of xenotransplantation as a viable solution to the global shortage of donor livers for patients with acute or end-stage liver failure. 1 Central to the success of this approach was the precise engineering of the donor pig's genome.Researchers eliminated three major xenoantigen genes (GGTA1, CMAH, and B4GALNT2) encoding glycan epitopes widely recognized by human natural antibodies, effectively preventing hyperacute rejection.Simultaneously, three human transgenes (CD46, CD55, and hTHBD) were integrated to enhance complement regulation and minimize thrombosis.These combined modifications created a safer immunological and hemodynamic environment for the xenograft.The clinical protocol featured a heterotopic auxiliary liver transplantation technique, in which the porcine liver was implanted without removing the native human liver.This allowed careful monitoring of graft performance while minimizing surgical risks.Preoperative imaging ensured alignment of the porcine portal vein and hepatic artery with the recipient's vasculature, guaranteeing functional blood flow.Postoperatively, bile was diverted externally for direct measurement of secretory capacity.Within just 2 h of reperfusion, the graft began secreting bile-a reliable early indicator of hepatic viability.Throughout the 10-day period, the graft continuously secreted bile, indicating preserved exocrine capability (Fig. 1).Concurrently, metabolic activity was demonstrated through steadily increasing porcine-derived albumin levels in the recipient's circulation, confirming active hepatic protein synthesis.Serum biomarkers of liver injury remained largely stable, aside from a transient spike in aspartate aminotransferase (AST) shortly after transplantation.The authors suggested that the AST elevation could be cardiac in origin, partly supported by simultaneous rises in cardiac enzyme markers.Later increases in bilirubin and -glutamyl transpeptidase likely mirrored mild cholestatic changes in the native liver rather than the xenograft.These findings collectively indicated that the pig liver maintained structural and metabolic integrity without pronounced hepatocellular damage.