Prohibitin 1 deletion from activated cardiac fibroblasts in vivo attenuates cardiac fibrosis
Authors: Davis Julie , de Castro Brás Lisandra , Garvin Alexandra 
Published: May 2024

Cardiac fibroblasts (CF) are responsible for extracellular matrix (ECM) deposition with cardiac injury. While fibrosis is a typical response to injury, excessive or uncontrolled fibrotic remodeling by CFs underlies the progression to heart failure. Cardiac injury-induced activated CFs are characteristically identified as periostin expressing cells that are proliferative and ECM secreting. This activated secretory phenotype is supported by altered mitochondrial mechanisms. Prohibitin 1 (PHB1) is known to play a role in cell survival via its impact on mitochondrial integrity, and we have established that it is enriched in activated CFs. This study aims to investigate the impact of conditional PHB1 deletion in vivo from activated CFs, and it is expected that PHB1 deletion will reduce or prevent isoproterenol (ISO)-induced fibrotic remodeling. Male and female Periostin-Cre (PC) Phb1fl/fl and WT Phb1fl/fl mice were infused with ISO (75 mg/kg/day) or vehicle (0.003% ascorbic acid in saline) for 1 or 2 weeks via osmotic micro-pump. Cre recombinase was induced by tamoxifen injection (75 mg/kg, i.p.). Hearts were collected, a mid-myocardial section was fixed and stained for fibrosis (Sirius red), and remaining tissue was frozen for protein and RNA extraction. Two weeks of ISO tended to increase hypertrophy in male (p=0.06) and female (p=0.08) mice compared to vehicle. Periostin protein expression was modulated similarly in male and female hearts, which exhibited a significant 7-fold increase following 2 weeks of ISO infusion (p=0.003 vs. vehicle). CF PHB1 deletion significantly attenuated this increase (p=0.009 vs. WT ISO). PHB1 deletion in activated CFs resulted in reduced Col1a1 gene expression following 2 weeks of ISO in males (38.6%) and in females (68.0%) relative to WT ISO. Further, both male and female PC mice exhibited ~55% reduction in Col3a1 gene expression after ISO infusion compared to WT. Taken together, these findings indicate that PHB1 deletion prevents ISO-induced CF activation in both sexes. Left ventricular fibrosis via Sirius red stain was more pronounced in mice treated for 2 weeks compared to 1 week, with males having markedly more fibrosis than females. The accumulation of ISO-induced fibrosis in males was prevented by PHB1 deletion. Interestingly, the extent of cardiac fibrosis with and without PHB1 deletion correlated with periostin protein expression in males, but not in females. Thus, the measured reduction in CF activation by conditional PHB1 deletion may limit ECM deposition in males. The lack of fibrotic tissue in the presence of elevated collagen gene expression and periostin in the ISO-treated females may reflect sex-specific CF phenotypes or fibrotic remodeling. In this model of fibrosis, it is unclear how PHB1 deletion is impacting the female heart structurally. Future studies will aim to elucidate altered mitochondrial mechanisms after PHB1 deletion in models of fibrosis, as well as sex-specific mechanisms of fibrotic remodeling. ECU REDE startup program, NIH T32HL007249-44, UArizona Sarver Heart Center. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.