High expression of angiotensin-converting enzyme and angiotensin-converting enzyme 2 in preservation injury after liver transplantation in rats

Aim: To explore the possible role of local renin-angiotensin system (RAS) in preservation injury (PI) after liver transplantation by studying expression of angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) in the transplanted liver of rats and its relationship with PI. Methods: The animals receiving liver transplantation were assigned to cold preservation group (CP group) and non-cold preservation group (NCP group). The sham-operation group was used as the control. The severity of PI was assessed by histology. The mRNA and protein expressions of ACE and ACE2 were detected by real-time PCR, Western blot, respectively. Tissue hypoxia was assessed by pimonidazole staining. Results: Various degrees of tissue injury were observed after liver transplantation, especially in CP group. ACE2 mRNA and protein expressions in the transplantation groups were elevated significantly compared with those of the control group (P < 0.01, P < 0.05), and higher in CP group than those in NCP group (P < 0.05). There was a close positive correlation between PI and mRNA expression of ACE and ACE2. Positive pimonidazole staining distributed around the hepatic central vein, and became darker and more extensive with deterioration of PI. Conclusion: ACE2 was closely related to tissue hypoxia due to CP-induced PI of the transplanted liver, and ACE may aggravate the inflammation in PI. Local RAS may play an important role in PI of the transplanted liver.