Is M30 staining a reliable marker predicting graft rejection and fibrosis in protocolar liver biopsies in post-liver transplant pediatric patients?

Background: Liver transplantation is currently a treatment of choice in patients with end-stage liver disease. Acute cellular rejection (ACR), antibody-mediated rejection (AMR), and chronic rejection (ChR) are major causes of graft injury. Therefore, new markers predicting graft rejection are investigating. Apoptosis has been recently proposed as one of the mechanisms contributing to liver fibrosis in liver grafts. Coarse needle liver biopsy is still a gold standard in monitoring post-transplant pathologies. The aim of this study was to assess the utility of immunohistochemical (IHC) staining for M30 (cytokeratin 18), as a prognostic marker of rejection in pediatric recipients of liver transplant and predicting marker of liver fibrosis and worse follow-up.

Methods: The study enrolled 55 biopsies from 55 patients aged 2.37 to 18.9 years (median 13.87 years) who underwent protocolar liver biopsies taken 1-17 years after liver transplantation (median 8.36 years). The control group (positive control group) consisted of 26 biopsies from 16 patients in whom acute ACR was diagnosed. IHC staining for M30 (cytokeratin 18) and histochemical Azan staining were performed in all liver specimens. The following changes were re-evaluated in each specimen: features of ACR (the severity was assessed using RAI/Rejection Activity Index/Scale, which ranges from 3-9 points and include 3 histopathological changes suggestive of rejection), AMR or ChR; severity of fibrosis (Ishak Scale); presence of cholestasis and steatosis. Clinical parameters including laboratory tests of liver function (AST, ALT, GGTP, bilirubin) were also evaluated.

Results: M30 expression correlated with presence of acute cellular rejection. However, no relationship was found between M30 expression and severity of fibrosis.

Conclusions: M30 staining, marker of apoptosis, seems to be a promising marker predicting acute cellular rejection.