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Granzyme K : a novel contributor in cardiac allograft vasculopathy

University of British Columbia

Background - A major factor limiting survival for patients that have undergone cardiac transplantation is cardiac allograft vasculopathy (CAV). CAV is a fibroproliferative inflammatory form of vascular rejection mediated by immune cells and which is initiated upon damage to the graft endothelium and medial smooth muscle cells (SMC). Granzymes are a family of five serine proteases in humans. Granzymes have been shown to exert roles in cell death, endothelial dysfunction, inflammation and matrix remodeling. Granzyme K (GzmK) specifically can promote endothelial dysfunction and the production of inflammatory mediators IL-1β, IL-6, and monocyte chemotactic protein-1. As such, we hypothesized that GzmK contributes to CAV. Methods - An infrarenal aortic interposition graft was completed across a complete major histocompatibility complex (MHC)-mismatch with recipients being either wildtype or GzmK-KO mice. Allografts were then assessed for CAV severity and compared to human CAV samples. The effects of GzmK on human SMC were also assessed in vitro. Given that atherosclerosis shares similar underlying mechanisms to CAV, GzmK deposition was also characterized in atherosclerosis. Results - Human CAV samples demonstrated increased neointimal GzmK deposition as compared to unaffected native coronaries (p= 0.017). GzmK primarily localized to the medial and neointimal layers. Similar deposition patterns were observed in murine transplants. When the role of GzmK was examined, GzmK deficiency resulted in reduced CAV with less neointima formation (p=0.019) and less luminal obstruction (p<0.0163). GzmK deficiency also had significantly less cellular proliferation as measured by Ki67 (p=0.026) while apoptosis (as measured by cleaved caspase 3) was unaffected (p=0.711). In vitro, GzmK lacked cytotoxicity on SMC whereas it increased cellular proliferation by 30% (p=0.038). Immunofluorescence co-localized GzmK with macrophages and lymphocytes while GzmK deposition was also observed in GzmK-KO recipients indicating that it is potentially graft derived. Conclusion – GzmK contributes to CAV with GzmK potentially arising from recipient and graft derived sources. GzmK may serve as a novel therapeutic target in CAV

Text

2020-08-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75778

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/