Background: Small-for-size syndrome limits the minimum liver mass required for successful segmental liver transplantation. Maximizing the ability of small segments to regenerate could potentially expand both the living and deceased liver donor pool. We investigated the role of inflammatory cytokines in promoting and impairing liver regeneration in a murine hepatectomy model.

Method: C57BL/6 mice underwent 70% hepatectomy and received supportive treatment only (vehicle control), 200ug anti-IL-6 blocking antibody at 3 hours post-op, 300ug anti-IL-6 Ab at 3h, or 300ug isotype control at 3h (IgG control). Serum IL-6 and ALT levels were measured at baseline and at serial time-points post-op. Liver biopsies were also taken for H&E and Ki-67 staining. Survival was determined both by following animals out to 7 days unless found dead or determined to be moribund and euthanized prior to the end of the study period, and by using a validated body condition scoring system that predicts long term survival with 97.3% accuracy.

Results: Serum IL6 levels increased in all mice up to 3h post-op. However, in mice that died, IL6 levels rose to 7-fold higher levels at 6h and remained elevated until death, while in mice that survived, IL6 levels dropped at 6h and returned to baseline by 12h (2251±581 vs. 371±129 pg/ml, P=0.003, fig. 1a).

These changes preceded serum ALT differences, which did not become significantly higher in dying animals until 24h post-op. Unsurprisingly, histology of livers from dying animals showed steatosis, vacuoles, necrotic patches, and low levels of Ki-67 compared to those from animals that survived. 300ug anti-IL6 blocking antibody, but not 200ug, resulted in decreased IL-6 (fig. 1b) and ALT levels (fig. 1c), improved survival (fig. 1d), increased hepatocyte replication (Ki-67+ cells, 67.9% vs 27.1% on 2d, p=0.03) and reversed the histologic changes (fig. 2).

Conclusion: Although IL-6 is crucial for initiating hepatocyte replication, prolonged elevation of IL-6 is associated with continued liver injury, poor regeneration, and death from liver failure. Delayed blockade of IL-6 activity decreased liver injury, and increased hepatocyte replication and survival and may be useful in promoting liver regeneration after small segment liver transplantation.