Biliary Epithelial Senescence in Cellular Rejection Following Live Donor Liver Transplantation

Abstract

Background: As with the hepatocytes, cholangiocyte senescence can also easily be detected in damaged small bile ducts and bile ductules during liver disease affecting the biliary system and cholangiocytes. Despite cellular senescence being a feature of chronic progressive cholangiopathies in adults, only a few studies have investigated its role in liver transplant rejection.

Method: Transplant biopsies displaying features of rejection were reviewed and classified based on the type of rejection and the time since transplantation. An immunohistochemistry panel has been applied for 3 senescent cell markers (p53, p21, p16).

Results: Immunohistochemical expression analysis for the biliary senescence markers (53 biopsies) was done in the post-transplantation periods (Group 1-4) for the cases with the histologically proven diagnosis of rejection. In post-transplant group 1 (<3 months), group 2 (3-6 months), group 3 (6-12 months) and group 4 (>12 months), any 2 senescent markers' positivity was noted in 5/14 (35.7%), 8/13 (61.5%), 16/17 (94.1%) and 9/9 (100%) biopsies respectively and were comparable in all four groups (P = 0.001). A comparison of early biopsies (Group1; 3 months) and late biopsies (Group 2,3&4; >3 months) revealed significantly higher expression in late biopsies (>3 months) (P = 0.001 for any two markers). In ACR, LAR, ECR, and CR/DR any two senescent markers were positive in 14/28 (50%), 12/13 (92.3%) cases, 9/9 (100%), and 3/3cases (100%). Senescent markers (any two) were comparable in all four histological groups (P < 0.001).LAR group had increased expression (P = 0.009 for any two markers and 0.001 for all three markers) and has increased progression to CR (P = 0.019) as compared to ACR.

Conclusion: This study on a large number of LDLT allograft biopsies demonstrates the role of biliary senescence in rejection and suggests a pathobiological role for senescence in the poor prognosis seen in late acute cellular rejection and chronic rejection.

Keywords: ACR, Acute cellular rejection; BEC, Biliary epithelial cells; CR/DR, Chronic Rejection/Ductopenic Rejection; ECR, Early chronic rejection; LAR, Late acute cellular rejection; LDLT, Live donor liver transplantation; MELD, Model for end-stage liver disease; RAI, Rejection activity index; liver; rejection; senescence; transplant.

Figure 1

Consort diagram displaying the study design.

Figure 2

ACR displaying portal inflammation and bile duct injury (arrow) (A; H&E;400x). LAR portal tracts show less inflammation (B; H&E;200x) and more prominent Zone 3 necroinflammatory lesion (Incet). An abnormal bile duct (arrow) in ECR along with nuclear pleomorphism and loss of polarity produce a ‘dysplastic-like’ appearance (C; H&E;200x). CR/DR shows loss of bile ducts (D; H&E; 200x). ACR, Acute cellular rejection; LAR, Late acute cellular rejection; ECR, Early chronic rejection; CR/DR, Chronic Rejection/Ductopenic Rejection.

Figure 3

Immunohistochemical stain for the cells senescence markers p16, p21, and p53 in liver allograft biopsy with LAR (A, B, and C, respectively), ECR (D, E, and F, respectively) and in CR/DR (G, H, and I, respectively) show a high level of expression. LAR, Late acute cellular rejection; ECR, Early chronic rejection; CR/DR, Chronic Rejection/Ductopenic Rejection.