Effects of CD8 T-cell Transfer on Biomechanics of Post-Myocardial Infarction Scar Formation

CD8+ T-cells are adverse regulators of post-MI remodeling, resulting in attenuated cardiac function and overall survival. Based on previous studies, we hypothesize that CD8+ T-cells impair cardiac function by altering scar composition. MI was induced by ligating the left anterior descending coronary artery on C57BL6/J wildtype (WT; 3-7 months of age, n≥2/sex) and CD8atm1mak (CD8−/−; 3-7 months of age, n≥2/sex/ group) mice. CD8−/− mice were injected with either vehicle or naïve splenic CD8+ T-cells via tail vein, 4-hours post-coronary artery ligation to assess potential effects on the scar. On day 7 post-MI, infarct tissue was collected, undergoing either passive stretch biomechanical analysis or histological and biochemical assays for collagen composition. Effects of granzyme (Gzm) B and K on collagen cleavage were tested using a fluorogenic collagen cleavage assay to examine possible mechanisms of scar alteration. Mice lacking CD8+ T-cells had improved ejection fraction and decreased dilation compared to WT mice at post-MI Day 7. This protective effect was lost in CD8−/− mice that received splenic CD8+ T-cells. Biomechanical analysis demonstrated CD8−/− mice had a 2-fold increase in regional stiffness compared to WT mice. Re-supplementation with splenic CD8+ T-cells decreased scar tissue stiffness mimicking biomechanics of WT mice. Picrosirius red staining surprisingly showed no significant differences in total collagen levels (p=0.51). Immunoblotting for Collagen 1 trended an increase in the 250 kDa band in CD8−/− mice that decreased after supplementation indicating a loss of pro-collagen formation (p=0.051). Ex-vivo cleavage assay demonstrated GzmK cleaved collagen in a concentration (0-50 AU) and temporal-dependent manner (0-24 hrs). Moreover, GzmK demonstrated a 10-fold greater capacity in collagen cleavage compared to GzmB at 25 AU, indicating the role GzmK plays during post-MI remodeling may be distinctly separate from that of GzmB. In conclusion, our data demonstrates that CD8+ T-cells regulate cardiac fibrosis potentially in part through the release of granzymes, leading to alterations in biomechanical capability of the left ventricle. This work was supported by the National Institutes of Health T32GM123055, R25GM113278; the Biomedical Laboratory Research and Development Service of the Veterans Affairs Offce of Research and Development Award IK2BX003922 and BX003922; and South Carolina Translational Research Center UL1TR001450. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.