Biology subjects

Vagnozzi, R. J.

Publications and source records attributed to Vagnozzi, R. J..

3 recordsLinked to original sources

bioRxiv2022

Cardiac fibroblasts regulate cardiomyocyte hypertrophy through dynamic regulation of type I collagen

RationaleCardiomyocytes and fibroblasts in the heart communicate through both secreted growth factors as well as through sensing the structural properties of the extracellular matrix that each helps generate. Previous studies have shown that defects in fibroblast activity during disease stimulation result in altered cardiomyocyte hypertrophy, although the role that collagen might play in this communication is unknown. ObjectiveHere we investigated how type I collagen maturation and disease-responsive matrix expansion in the heart by cardiac fibroblasts impacts cardiac fibrosis and cardiomyocyte hypertrophy. Methods and ResultsWe generated and characterized Col1a2-/- mice using standard gene-targeting. Col1a2-/- mice were viable, although by young adulthood their hearts showed alterations in extracellular matrix mechanical properties, as well as an unanticipated activation of cardiac fibroblasts and induction of a progressive fibrotic response. This included increases in fibroblast number and a progressive cardiac hypertrophy, with reduced functional performance by 9 months. Col1a2-loxP targeted mice were also generated and crossed with the tamoxifen-inducible Postn-MerCreMer knock-in mice to delete the Col1a2 gene in myofibroblasts post-pressure overload injury, to more specifically implicate fibroblasts as effectors of cardiomyocyte hypertrophy in vivo. Opposite to the gradual induction of cardiac hypertrophy observed in germline Col1a2-/- mice as they matured developmentally, adult fibroblast-specific deletion of Col1a2 during pressure overload protected these mice from cardiac hypertrophy in the first week with a delayed fibrotic response. However, this reduction in hypertrophy due to myofibroblast-specific Col1a2 deletion was gradually lost over 2 and 6 weeks of pressure overload as augmented fibrosis returned. ConclusionsDefective type I collagen in the developing heart alters the structural integrity of the extracellular matrix that leads to fibroblast expansion, activation, fibrosis and hypertrophy with progressive cardiomyopathy in adulthood. However, acute deletion of type I collagen production for the first time in the adult heart during pressure overload prevents ECM expansion and inhibits cardiomyocyte hypertrophy, while gradual restoration of fibrosis again permitted hypertrophy comparable to controls.

cell biology↗

bioRxiv2021

S-Palmitoylation-Dependent Regulation of Cardiomyocyte Rac1 Signaling Activity and Cardiac Hypertrophy

S-palmitoylation is a reversible lipid modification that regulates trafficking, localization, activity, and/or stability of protein substrates by serving as a fatty acid anchor to cell membranes. However, S-palmitoylation-dependent control of signal transduction in cardiomyocytes and its effects on cardiac physiology are not well understood. We performed an in vivo gain-of-function screen of zinc finger Asp-His-His-Cys (zDHHC) family S-acyl transferases that catalyze S-palmitoylation and identified the Golgi-localized enzyme zDHHC3 as a critical regulator of cardiac maladaptation. The closely-related enzyme, zDHHC7, also induced severe cardiomyopathy but this effect was not observed with overexpression of plasma membrane enzyme zDHHC5, endoplasmic reticulum enzyme zDHHC6, or Golgi enzyme zDHHC13. To identify effectors that may underlie zDHHC3-induced cardiomyopathy we performed quantitative site-specific S-acyl proteomics in zDHHC3-overexpressing cells that revealed the small GTPase Rac1 as a novel substrate. We generated cardiomyocyte-specific transgenic mice overexpressing zDHHC3, which develop severe cardiac disease. Cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice are preceded by enhanced S-palmitoylation of Rac1 and induction of additional Rho family small GTPases including RhoA, Cdc42, and the Rho family-specific chaperone RhoGDI. In contrast, transgenic mice overexpressing an enzymatically-dead mutant of zDHHC3 do not exhibit this profound induction of RhoGTPase signaling or develop cardiac disease. Rac1 S-palmitoylation, plasma membrane localization, activity, and downstream hypertrophic signaling were substantially increased in zDHHC3 overexpressing hearts. Taken together, these data suggest inhibition of zDHHC3/7 S-acyl transferase activity at the cardiomyocyte Golgi or disruption of Rac1 S-palmitoylation as novel therapeutic strategies to treat cardiac disease or other diseases associated with enhanced RhoGTPase signaling.

molecular biology↗

bioRxiv2019

Satellite cell depletion in early adulthood attenuates muscular dystrophy pathogenesis

Satellite cells are skeletal muscle resident stem cells that regenerate adult myofibers following an acute injury to muscle. Despite the assumption that the loss of satellite cells would be detrimental in a chronic regeneration-inducing muscle disease such as muscular dystrophy, this assumption has never been tested using mouse genetics. Here we generated a novel model of satellite cell ablation and crossed it with mouse models of muscular dystrophy to directly investigate how critical these cells are in maintaining muscle during a chronic degenerative disorder. Satellite cell deletion in 2-week-old young dystrophic mice provided noticeable improvements in histopathology and function, although at this early timepoint it was utimately detrimental because muscle size was not sufficient to permit survival. However, depletion of satellite cells beginning at 2 months of age in dystrophic mice provided similar histological and functional improvements but without compromising muscle size. The improved profile showed fewer damaged fibers, less myofiber central nucleation, increased sarcolemma integrity, decreased fibrosis and a dramatic size increase in the remaining myofibers. At the functional level, young adult dystrophic mice lacking satellite cells performed significantly better than those with satellite cells when exercised on a treadmill. Thus, loss of satellite cells during early adulthood in dystrophic mice produces an unexpected protective effect.

molecular biology↗