Introduction: Human thrombomodulin (hTBM) is frequently introduced into genetically engineered pigs to reduce coagulation-related complications in xenotransplantation. While hTBM expression improves vascular compatibility in solid organ transplantation, its impact on endocrine organs such as the pancreas remains unclear. This study aimed to evaluate the metabolic and immunological consequences of hTBM expression in pigs engineered for islet xenotransplantation.
Methods: Transgenic pigs expressing hTBM (QKO-hTBM) were produced by genetic engineering system. Total pancreatectomy was followed by comparative analysis of gross morphology, histology, serum biochemistry, and cytokine profiles among with wild-type (WT) and four xeno-antigen (GGTA1, CMAH, b4GalNT2 and A3GALT2) knockout (QKO) pigs. Human serum was also analyzed for comparison. Fat accumulation was assessed by Oil Red O staining, and insulin-positive islet area was measured via immunofluorescence.
Results: Gross and histological examination revealed extensive pancreatic fat infiltration in QKO-hTBM pigs, while WT and QKO pancreas appeared normal. QKO-hTBM pigs showed significantly larger islets but exhibited elevated fasting blood glucose and reduced porcine insulin and C-peptide levels. Serum hTBM levels in transgenic pigs were also significantly higher than in healthy humans. Cytokine profiling indicated increased IFN-γ, IL-1β, IL-17, and TNF-α, alongside reduced IL-10, suggesting a shift toward a pro-inflammatory state.
Conclusion: Although hTBM expression regulate coagulation-related complication in xenotransplantation, its systemic overexpression may impair pancreatic function and immune balance, posing risks in islet transplantation. Tight regulation of hTBM expression, potentially through tissue-specific or inducible promoters, may be necessary to optimize metabolic outcomes in future clinical islet xenotransplantation.