IL-6 induces regeneration and angiogenesis in bile ducts and prevents complications after liver transplantation

Question Bile duct (BD) damage leads to complications that are a major cause of morbidity and mortality after liver transplantation. Previous studies by our group have shown that donors’ livers with damaged BD epithelia after cold storage are linked to an increased risk of developing these complications than livers with intact bile ducts. The molecular mechanisms leading to damage and healing are yet to be fully understood. However, in-vitro-studies suggest that IL-6 may play a striking role in bile duct regeneration as well as damage prevention. This study aims to examine this role using novel in-situ-hybridization methods combined with automated image analysis algorithms.

Methods During liver transplantation, specimens of donors’ common bile duct were taken after cold storage and after reperfusion and fixated (FFPE). Following a HE-staining to determine the presence of ‘major’ bile duct damage, an in-situ hybridization for IL-6 mRNA was performed for each specimen, and the density of IL-6-positive cells in predefined areas (subepithelial/peribiliary glands) was analyzed using an image analysis software. Effects on angiogenesis was detected using subsequent immunhistochemical staining for VEGFa. To determine IL-6’s cellular origin and its possible local effects on cell proliferation, angiogenesis and immune response, a novel multiplex-fluorescence-in-situ-hybridisation method (miFISH) was used.

Results In comparison to cold storage (n = 20), after reperfusion (n = 30) a significantly increased IL-6 expression could be measured in the BDs (p < 0.0001). Patients who did not develop BD complications had received BDs with significantly increased IL-6 amounts and increased VEGFa levels compared to patients who did develop complications (p=.001;.03). IL-6 and VEGFa were co-expressed subepithelial and in peribiliary glands. Fibroblasts (aSMA+) and endothelial cells (CD34+) could be identified as a cellular origin of IL-6, whereas BD epthelial cells (CK19+) and infiltrating leukocytes (CD45+) showed no IL-6 expression.

Conclusions For the very first time it was possible to show an upregulation of IL-6-expression in the BD in-situ following reperfusion. The results suggest that IL-6 indeed prevents BD damage and induces regeneration and angiogenesis of damaged BDs, thus leading to lower probabilities of complications. In the future, the perfusion of IL-6 through the donor’s BD might be a therapeutical approach to reduce complication rates after liver transplantation.

Publication History

Article published online:
04 January 2021