Inhibition of Transglutaminase 2 Reduces Peritoneal Injury in a Chlorhexidine-Induced Peritoneal Fibrosis Model

Long-term peritoneal dialysis (PD) is often associated with peritoneal dysfunction leading to withdrawal from PD. The characteristic pathologic features of peritoneal dysfunction are widely attributed to peritoneal fibrosis and angiogenesis. The detailed mechanisms remain unclear, and treatment targets in clinical settings have yet to be identified. We investigated transglutaminase 2 (TG2) as a possible novel therapeutic target for peritoneal injury. TG2 and fibrosis, inflammation, and angiogenesis were investigated in a chlorhexidine gluconate (CG)-induced model of peritoneal inflammation and fibrosis, representing a noninfectious model of PD-related peritonitis. Trans-forming growth factor (TGF)-0 type I receptor (TGF0R-I) inhibitor and TG2-knockout mice were used for TGF-0 and TG2 inhibition studies, respectively. Double immunostaining was performed to identify cells expressing TG2 and endothelial-mesenchymal transition (EndMT). In the rat CG model of peritoneal fibrosis, in situ TG2 activity and protein expression increased during the development of peritoneal fibrosis, as well as increases in peritoneal thickness and numbers of blood vessels and macrophages. TGF0R-I inhibitor suppressed TG2 activity and protein expression, as well as peritoneal fibrosis and angiogenesis. TGF-01 expression, peritoneal fibrosis, and angiogenesis were suppressed in TG2-knockout mice. TG2 activity was detected by a-smooth muscle actin-positive myofibroblasts, CD31-positive endothelial cells, and ED-1-positive macro-phages. CD31-positive endothelial cells in the CG model were a-smooth muscle actin-positive, vimentin-positive, and vascular endothelial-cadherin-negative, suggesting EndMT. In the CG model, EndMT was suppressed in TG2-knockout mice. TG2 was involved in the interactive regu-lation of TGF-0. As inhibition of TG2 reduced peritoneal fibrosis, angiogenesis, and inflammation associated with TGF-0 and vascular endothelial growth factor-A suppression, TG2 may provide a new therapeutic target for ameliorating peritoneal injuries in PD.(c) 2022 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.

Automated summary

Long-term peritoneal dialysis is often associated with peritoneal dysfunction characterized by fibrosis, inflammation, and angiogenesis. In this study, transglutaminase 2 (TG2) was identified as a potential therapeutic target for peritoneal injury. TG2 activity and protein expression were found to increase during the development of peritoneal fibrosis, and TGF-β and TG2 interaction played a role in regulating peritoneal fibrosis, angiogenesis, and inflammation. Inhibition of TG2 showed promising results in reducing peritoneal injuries associated with PD.