Suneeta Narumanchi
Minerva Institute for Medical Research, Finland
Title: MicroRNA let-7c regulates heart regeneration after cryoinjury in adult zebrafish
Biography
Biography: Suneeta Narumanchi
Abstract
Introduction: Micro-RNAs are short, noncoding RNA molecules that regulate gene expression. Micro-RNA let-7c has an important role in cardiac regeneration and remodelling after myocardial infarction in mice. Understanding the role of let-7c in regeneration of zebrafish heart remains incomplete.
Methods: Antagomir injections were used to knockdown Let-7c, while injections of scramble RNA were used as control in adult zebrafish. The apex of the ventricle was cooled with a metal probe dipped in liquid nitrogen, this procedure kills cardiomyocytes and mimics myocardial infarction. Knockdown of let-7c was confirmed with qPCR. Cardiac function was followed with cardiac ultrasound before the cryoinjury and after the cryoinjury at day 1, 1 week, 2 weeks, 3 weeks and 4 weeks. Fractional volume shortening (FVS) of the ventricle was found to be the most reliable and repeatable method to quantify cardiac function. Heart, liver and kidney samples were collected at 2 weeks and 4 weeks for qPCR, Acid Fuchsine Orange G staining and immunohistochemistry with proliferating cell nuclear antigen (PCNA).
Results: Let-7c antagomir treatment resulted in faster recovery of cardiac function and improved regeneration after cryoinjury compared to control treatment. FVS returned to pre-cryoinjury levels (35.74%±1.01%) in let-7c antagomir fish three weeks after cryoinjury (29.92 %±1.9%, P=0.053), whereas, FVS was comparable to pre-cryoinjury levels at 4 weeks (29.18 %±0.63%, P=0.052) in the control fish. Let-7c antagomir fish had lower fibrin% (8.64 %±2.20, P=0.039) in the injured area at four weeks compared to control fish (19.67%±4.26). Collagen accumulation started earlier in the let-7c antagomir fish indicating a faster recovery. At 2 weeks fibrin/collagen% was greater in let-7c antagomir fish compared to control fish (43.16%± 4.87 vs. 29.98%±3.97, P=0.05).
Immunohistochemistry with PCNA revealed a trend of higher proliferating cardiomyocytes in the antagomir group at two weeks.
Conclusion: Inhibition of Let-7c improved cardiac regeneration after cryoinjury in adult zebrafish.