Altered expression of eNOS, prostacyclin synthase, prostaglandin G/H synthase, and thromboxane synthase in porcine aortic endothelial cells after exposure to human serum—relevance to xenotransplantation

Abstract

Under normal conditions, the activity of platelets is stringently and precisely balanced between activation and quiescent state. This guarantees rapid hemostasis and avoids uncontrolled thrombosis. However, excessive platelet activation and resulting thrombotic microangiopathy are frequently observed in pig-to-primate xenotransplantation models. Endothelium-derived inhibitory mechanisms play an important role in regulation of platelet activation. These mainly include nitric oxide (NO), prostacyclin PGI , and adenosine, which are synthesized by endothelial NO synthases (eNOS), prostacyclin synthase, and CD39/CD73, respectively. We investigated whether endothelium-derived regulatory mechanisms are affected in porcine aortic endothelial cells (PAECs) after exposure to human serum. In the present study, exposure of PAECs or porcine iliac arteries to human serum suppressed gene expression of eNOS and prostacyclin synthase, while induced gene expression of prostaglandin G/H synthase and thromboxane synthase. Simultaneously, exposure to human serum reduced NO and PGI production in PAEC culture supernatants. Thus, human serum altered the balance of endothelium-derived inhibitory mechanisms in PAECs, which may indicate a regulatory mechanism of excessive platelet activation in pig-to-primate xenotransplantation.

Selective inhibition of cyclooxygenase‐2 protects porcine aortic endothelial cells from human antibody‐mediated complement‐dependent cytotoxicity

“…COX‐2 overespression in allograft has also been reported previously in rat cardiac transplantation, and human renal transplantation . We previously found the upregulation of COX‐2 expression in PAECs exposed to human serum, but the effects of COX‐2 overexpression on PAECs remain unknown …”

“…We previously observed the upregulation of COX‐2 expression in wild‐type PAECs and α1,3‐galactosyltransferase gene‐knockout (GTKO) PAECs exposed to human serum . However, the effects of COX‐2 overexpression in PAECs remain unknown.…”

“…Porcine aortic endothelial cells (PAECs) were isolated from wild‐type Chinese domestic miniature Wuzhishan pig, GTKO Wuzhishan pig, or Bama miniature pigs arteries, as previously described . Four isolations of PAECs were used in this study: P16004 and P16007 (WT Wuzhishan PAEC), P16010 (GTKO Wuzhishan PAEC), P16019 (WT Bama PAEC).…”

“…RNA extraction, reverse transcription, and the real‐time PCR procedure were as previously described . The primer sequences are listed in Table .…”

“…Vascular endothelial cells express high levels of COX‐2 as a result of various extracellular stimuli and increase in PG production . Dysregulated COX‐2 expression usually contributes to endothelial dysfunction.…”