Biology subjects

O'Meara, C. C.

Publications and source records attributed to O'Meara, C. C..

2 recordsLinked to original sources

bioRxiv2022

Myofibroblast Ccn3 is regulated by Yap and Wwtr1 and contributes to adverse cardiac outcomes

While Yap and Wwtr1 regulate resident cardiac fibroblast to myofibroblast differentiation following cardiac injury, their role specifically in activated myofibroblasts remains unexplored. Here we assess the pathophysiological and cellular consequence of genetic depletion of Yap alone (Yapfl/fl;PostnMCM) or Yap and Wwtr1 (Yapfl/fl;Wwtr1fl/+;PostnMCM) in adult mouse myofibroblasts following myocardial infarction and identify and validate novel downstream factors specifically in cardiac myofibroblasts that mediate pathological remodeling. Following myocardial infarction, depletion of Yap in myofibroblasts had minimal effect on heart function while depletion of Yap/Wwtr1 resulted in smaller scars, reduced interstitial fibrosis, and improved ejection fraction and fractional shortening. Single cell RNA sequencing of interstitial cardiac cells 7 days post infarction showed suppression of pro-fibrotic genes in fibroblasts derived from Yapfl/fl,Wwtr1fl/+;PostnMCM hearts. In vivo myofibroblast depletion of Yap/Wwtr1 as well in vitro knockdown of Yap/Wwtr1 dramatically decreased RNA and protein expression of the matricellular factor Ccn3. Administration of recombinant CCN3 to adult mice following myocardial infarction remarkably aggravated cardiac function and scarring. CCN3 administration drove myocardial gene expression of pro-fibrotic genes in infarcted left ventricles implicating CCN3 as a novel driver of cardiac fibrotic processes following myocardial infarction.

physiology↗

bioRxiv2022

Cardiomyocyte ploidy is dynamic during postnatal development and varies across genetic backgrounds

Somatic polyploidization, an adaptation by which cells increase their DNA content to support cell and organ growth, is observed in many mammalian cell types, including cardiomyocytes. Although polyploidization is beneficial in many contexts, progression to a polyploid state is often accompanied by a loss of proliferative capacity. Recent work suggests that heterogeneity in cardiomyocyte ploidy is highly influenced by genetic diversity. However, the developmental course by which cardiomyocytes reach their final ploidy state has only been investigated in select genetic backgrounds. Here, we assessed cardiomyocyte number, cell cycle activity, and ploidy dynamics across two divergent inbred mouse strains; C57Bl/6J and A/J. Both strains are born and reach adulthood with a comparable number of cardiomyocytes, however the end composition of ploidy classes and developmental progression to reach the final state and number differ substantially. In addition to corroborating previous findings that identified Tnni3k as a mediator of cardiomyocyte ploidy, we also uncover a novel role for Runx1 and Tnni3k in ploidy dynamics and cardiomyocyte cytokinesis. These data provide novel insight into the developmental path to cardiomyocyte ploidy states and challenge the paradigm that polyploidization and hypertrophy are the only mechanisms for growth in the mouse heart after the first week of life.

developmental biology↗