Dexamethasone inhibits early regenerative response of rat liver after cold preservation and transplantation.

Regeneration is crucial for the recovery of hepatic mass following liver transplantation. Glucocorticoids, immunosuppressive and antiinflammatory agents commonly used in transplantation, are known to inhibit the expression of specific cytokines and growth factors. Some of these proteins, namely tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6), play a critical role in the initiation of liver regeneration. Following cold preservation and reperfusion of the transplanted liver, the normal recovery process is marked by increased expression of TNF-alpha and IL-6, followed by activation of cytokine-responsive transcription factors and progression of the cell cycle resulting in hepatocyte proliferation. We hypothesized that glucocorticoids may influence the repair mechanisms initiated after extended cold preservation and transplantation. Using a rat orthotopic liver transplant model, recipient animals were treated with dexamethasone at the time of transplantation of liver grafts with prolonged cold storage (16 hours). Treatment with dexamethasone suppressed and delayed the expression of TNF-alpha and IL-6 compared with animals receiving no treatment and attenuated downstream nuclear factor kappaB (NF-kappaB), signal transduction and activator of transcription 3 (STAT3), and activation protein 1 (AP-1) activation. This suppression was accompanied by poor cell-cycle progression, delayed cyclin D1 nuclear transposition, and impaired hepatocyte proliferation by BrdU uptake. Histologically, the liver grafts in treated animals demonstrated more injury than controls, which appeared to be necrosis, rather than apoptosis. In conclusion, these data provide evidence that the administration of glucocorticoids at the time of transplantation inhibits the initiation of the regenerative process and may have a deleterious effect on the recovery of liver grafts requiring significant regeneration. This may be particularly relevant for transplantation of partial liver grafts in the living donor setting.

Severe preservation injury induces Il-6/STAT3 activation with lack of cell cycle progression after partial liver graft transplantation.

Partial liver graft transplantation is a surgical advance developed to overcome severe donor shortage. Survival of these grafts involves recovery from cold ischemia and reperfusion (CIR) injury, immediate regeneration and maintenance of function. Here we examined the outcome of partial liver grafts in comparison to whole grafts following CIR injury. Lewis rats subjected to orthotopic liver transplantation (OLT) with whole grafts preserved in Viaspan were compared to rats receiving 50% and 30% grafts. Outcome was analyzed by survival and regeneration. Transplantation was associated with 100% survival for all grafts, whereas 16 h preservation resulted in 100%, 20% and 0% survival in animals receiving whole, 50% and 30% grafts, respectively. CIR induced increased IL-6 levels in 50% and 30% grafts, and activation of STAT3. Cell cycle progression (cyclin D1) and regeneration (BrdU) was initiated in all livers preserved for 1 or 8 h, but not in partial grafts preserved for 16 h. In conclusion, partial grafts recover from CIR injury through similar molecular pathways to whole grafts. Partial grafts with severe injury fail to achieve cellular proliferation despite the early initiating signals. This failure could be attributed to the impaired ability of the parenchyma to respond to initiating signals for regeneration.