Objectives To investigate if calcineurin pathway is involved in cardiac fibroblasts proliferation, transdifferentiation and apoptosis induced by mechanical stretch.
Methods Primary cardiac fibroblasts from 1- to 2-day-old Sprague-Dawley rats were isolated by trypsinization and purified by differential anchoring velocity technology. The cultured cells of passage 2-3 were divided into: control group, mechanical stretch group (MS group), calcineurin siRNA + mechanical stretch group (CaN-siRNA + MS group), FK506 + mechanical stretch group (FK506 + MS group), calcineurin overexpression + mechanical stretch group (CaN-overex + MS group). Calcineurin and downstream NFAT3 expressions were determined by western blot. Cardiac fibroblasts proliferation was determined by cell counting kit-8 and detection of proliferating cell nuclear antigen (PCNA), cell transdifferentiation was measured by alpha-smooth muscle actin (alpha-SMA) through western blot and apoptosis by Bax/Bcl-2.
Results Mechanical stretch promoted cardiac fibroblasts proliferation, as well as upregulation of alpha-SMA and increased Bax/Bcl-2 ratio, overexpression of calcineurin could promote more cardiac fibroblasts adverse remodelling similar to those induced by mechanical stretch. Pretreatment with calcineurin-siRNA lentivirus significantly attenuated cardiac fibroblasts proliferation, transdifferentiation and apoptosis when later stimulated by mechanical stretch, whereas pretreatment with FK506, a calcineurin inhibitor, only moderately inhibited cardiac fibroblasts proliferation and apoptosis with no obvious effect on cell transdifferentiation.
Conclusions This study demonstrates that mechanical stretch promoted cardiac fibroblasts proliferation, transdifferentiation and apoptosis via activating calcineurin/NFAT3, thus abolishing the calcineurin pathway might be beneficial for reversing myocardial fibrosis.