Abstract Body: Introduction: Endothelial cells (ECs) are indispensable in maintaining cardiac homeostasis, and EC dysfunction contributes to diabetic cardiomyopathy. Reelin (RELN) is a large secreted extracellular matrix protein critical in organizing external encapsulating structure. Emerging evidence has revealed its broader physiological significance, including cancer progression, coagulation deficits, and endothelial dysfunction associated with chronic inflammatory diseases. However, the function of RELN in cardiomyopathy remains to be explored.
Hypothesis: We hypothesize that EC RELN protects against cardiomyopathy via mitophagy and chronic inflammation in diabetic conditions.
Methods: Type 2 diabetes was induced in control (Reln^fl/fl) and EC RELN deficient mice (Reln^ECKO) by high-fat diet feeding combined with low-doses streptozotocin administration. Cardiac function was measured by echocardiography at different time points. In vitro diabetic conditions were simulated using D-glucose and palmitic acid. Cell proliferation, apoptosis, and reactive oxygen species (ROS) production were analyzed in primary human and RELN-deficient mouse cardiac ECs. RNA sequencing was performed for gene set enrichment analysis in RELN-deficient ECs. Cardiac ECs overexpressing fluorescent mitophagy reporter (cox8-EGFP-mCherry) were used to examine mitophagy following RELN silencing.
Results: Following the development of T2D, Reln^ECKO mice exhibited a significant decline in cardiac function, including reduced ejection fraction and fractional shortening (n = 10/group, p < 0.01). The increase in left ventricular internal systolic diameter and decreased left ventricular posterior wall thickness during diastole indicated impaired systolic function along with subtle structural and functional myocardial alterations. Mechanistically, endothelial RELN deficiency led to decreased cell proliferation, increased apoptosis, elevated ROS production, and impaired mitophagy. Gene set enrichment analysis indicated that the loss of RELN in ECs impaired EC mitophagy and increased inflammatory cytokines, particularly C-X-C Motif Chemokine Ligand 10 production.
Conclusions: Our study reveals that EC RELN deficiency exacerbates diabetic cardiomyopathy via mitophagy and chronic inflammation. These findings underscore the critical role of EC RELN in maintaining cardiac homeostasis, suggesting its potential as a therapeutic target for diabetic cardiomyopathy.