Selective deletion of endothelial cell calpain in mice reduces diabetic cardiomyopathy by improving angiogenesis
The role of non-cardiomyocytes in diabetic cardiomyopathy has not been fully addressed. This study investigated whether endothelial cell calpain plays a role in myocardial endothelial injury and microvascular rarefaction in diabetes, thereby contributing to diabetic cardiomyopathy.
Endothelial cell-specific Capns1-knockout (KO) mice were generated. Conditions mimicking prediabetes and type 1 and type 2 diabetes were induced in these KO mice and their wild-type littermates. Myocardial function and coronary flow reserve were assessed by echocardiography. Histological analyses were performed to determine capillary density, cardiomyocyte size and fibrosis in the heart. Isolated aortas were assayed for neovascularisation. Cultured cardiac microvascular endothelial cells were stimulated with high palmitate. Angiogenesis and apoptosis were analysed.
Endothelial cell-specific deletion of Capns1 disrupted calpain 1 and calpain 2 in endothelial cells, reduced cardiac fibrosis and hypertrophy, and alleviated myocardial dysfunction in mouse models of diabetes without significantly affecting systemic metabolic variables. These protective effects of calpain disruption in endothelial cells were associated with an increase in myocardial capillary density (wild-type vs Capns1-KO 3646.14 ± 423.51 vs 4708.7 ± 417.93 capillary number/high-power field in prediabetes, 2999.36 ± 854.77 vs 4579.22 ± 672.56 capillary number/high-power field in type 2 diabetes and 2364.87 ± 249.57 vs 3014.63 ± 215.46 capillary number/high-power field in type 1 diabetes) and coronary flow reserve. Ex vivo analysis of neovascularisation revealed more endothelial cell sprouts from aortic rings of prediabetic and diabetic Capns1-KO mice compared with their wild-type littermates. In cultured cardiac microvascular endothelial cells, inhibition of calpain improved angiogenesis and prevented apoptosis under metabolic stress. Mechanistically, deletion of Capns1 elevated the protein levels of β-catenin in endothelial cells of Capns1-KO mice and constitutive activity of calpain 2 suppressed β-catenin protein expression in cultured endothelial cells. Upregulation of β-catenin promoted angiogenesis and inhibited apoptosis whereas knockdown of β-catenin offset the protective effects of calpain inhibition in endothelial cells under metabolic stress.
These results delineate a primary role of calpain in inducing cardiac endothelial cell injury and impairing neovascularisation via suppression of β-catenin, thereby promoting diabetic cardiomyopathy, and indicate that calpain is a promising therapeutic target to prevent diabetic cardiac complications.
Keywordsβ-Catenin Calpain Diabetic cardiomyopathy Endothelial cells Neovascularisation
Adenoviral vector containing rat calpastatin
Adenoviral vector containing β-galactosidase
Coronary flow reserve
Cardiac microvascular endothelial cell
- E/A ratio
Ratio of maximal early and late transmitral velocities
Small interfering RNA
Vascular endothelial growth factor
XT designed the experiments, researched and analysed data, drafted the manuscript and approved the submitted version. CJ researched and interpreted data, drafted the manuscript and approved the submitted version. HZ researched and collected data, drafted the manuscript and approved the submitted version. DZ designed the experiments, researched data, drafted the manuscript and approved the submitted version. RN researched data, drafted the manuscript and approved the submitted version. DJH contributed to the experimental design and discussion, reviewed/edited the manuscript and approved the submitted version. SX contributed to the discussion and the experimental design, reviewed/edited the manuscript, and approved the submitted version. G-CF contributed to the design and discussion, reviewed/revised the manuscript and approved the submitted version. PAG contributed to the generation of endothelial cell Capns1 knockout mice, the design and discussion, reviewed/revised the manuscript and approved the submitted version. ZS contributed to the early conception and design and the discussion, reviewed/revised the manuscript and approved the submitted version. TP designed the study, analysed data, wrote/revised the manuscript and approved/submitted the final version. TP is the guarantor of this work.
This work was supported by operating grants from the National Natural Science Foundation of China  and the Canadian Institutes of Health Research [MOP-133657], and by the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT, IRT1075).
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
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