Modulation of the Hippo signalling pathway by a novel miRNA to enhance cardiac regenerative capacity

  • Ardiansah Nugroho

Student thesis: Phd

Abstract

Recent studies have revealed that postnatal human hearts possess a marked ability for renewal, raising hope for a new therapeutic approach for cardiac repair through stimulating endogenous cardiomyocyte proliferation. Modulation of the Hippo pathway, a key regulator of cardiomyocyte proliferation and survival, has been shown to improve cardiac structure and function post-MI. However, targeting the core components of the pathway for therapeutic purpose is difficult due to the limited understanding on its upstream regulatory mechanism. MicroRNAs (miRNAs), small non-coding ribonucleic acids (RNAs), are considered potential therapeutic targets because of their ability to modulate the expression of genes, including those related to the Hippo pathway. The aim of this study is to identify novel miRNA(s) that can modulate the Hippo pathway and enhance cardiac regenerative capacity. First, we performed literature review, bioinformatics study, and Yes-associated protein (YAP) luciferase assay to screen candidate miRNAs for their ability to enhance the activity of YAP, the main effector of the Hippo pathway, and identified miR-411 as a potential Hippo regulator. Overexpression of miR-411 can significantly induce cardiomyocyte proliferation by reducing phosphorylation of Hippo component large tumour suppressor kinase 1 (LATS1) and YAP. To test the effects of miR-411 in vivo, we overexpress miR-411 by injecting miR-411 mimics resuspended with non-viral vector polyethilenimine directly into the myocardium of a normal heart or following myocardial infarction (MI). Overexpression of miR-411 can induce cardiomyocyte cell cycle re-entry in the adult heart and improve cardiac structures and functions at four weeks post-MI. To investigate miR-411 target genes in cardiomyocytes, the expression of 30 candidate target genes was examined following in vitro and in vivo overexpression of miR-411. The expression of the serotonin transporter gene (SERT) was found to be significantly downregulated and the interaction between miR-411 and the 3’ untranslated region (3’UTR) of SERT messenger RNA (mRNA) was confirmed by luciferase assay, indicating that SERT is a direct target of miR-411. Interestingly, small interfering RNA (siRNA)-mediated knockdown of SERT resulted in a significant reduction in LATS1 phosphorylation and an increase in YAP activity, a phenotype similar to that of miR-411 treated neonatal rat cardiomyocytes (NRCMs). In addition, experiments using serotonin receptor antagonist supported the finding that miR-411 mediated Hippo modulation was linked with SERT-dependent signalling. However, the exact mechanism is yet to be investigated. In conclusion, miR-411 enhances cardiac regeneration and improves cardiac function post-MI by modulating the Hippo pathway. The mechanism is likely through the inhibition of SERT expression.
Date of Award31 Dec 2020
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorElizabeth Cartwright (Supervisor) & Delvac Oceandy (Supervisor)

Keywords

  • serotonin transporter
  • miR-411
  • serotonin signalling
  • cardiac regeneration
  • Hippo pathway
  • miRNA
  • myocardial infarction

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