Identifying molecular and functional similarities and differences between human primary cardiac valve interstitial cells and ventricular fibroblasts

Abstract

Introduction: Fibroblasts are mesenchymal cells that predominantly produce and maintain the extracellular matrix (ECM) and are critical mediators of injury response. In the heart, valve interstitial cells (VICs) are a population of fibroblasts responsible for maintaining the structure and function of heart valves. These cells are regionally distinct from myocardial fibroblasts, including left ventricular cardiac fibroblasts (LVCFBs), which are located in the myocardium in close vicinity to cardiomyocytes. Here, we hypothesize these subpopulations of fibroblasts are transcriptionally and functionally distinct.Methods: To compare these fibroblast subtypes, we collected patient-matched samples of human primary VICs and LVCFBs and performed bulk RNA sequencing, extracellular matrix profiling, and functional contraction and calcification assays.Results: Here, we identified combined expression of SUSD2 on a protein-level, and MEOX2, EBF2 and RHOU at a transcript-level to be differentially expressed in VICs compared to LVCFBs and demonstrated that expression of these genes can be used to distinguish between the two subpopulations. We found both VICs and LVCFBs expressed similar activation and contraction potential in vitro, but VICs showed an increase in ALP activity when activated and higher expression in matricellular proteins, including cartilage oligomeric protein and alpha 2-Heremans-Schmid glycoprotein, both of which are reported to be linked to calcification, compared to LVCFBs.Conclusion: These comparative transcriptomic, proteomic, and functional studies shed novel insight into the similarities and differences between valve interstitial cells and left ventricular cardiac fibroblasts and will aid in understanding region-specific cardiac pathologies, distinguishing between primary subpopulations of fibroblasts, and generating region-specific stem-cell derived cardiac fibroblasts.

Y chromosome linked UTY modulates sex differences in valvular fibroblast methylation in response to nanoscale extracellular matrix cues

“…To the best of our knowledge, our study is the first to directly show UTY influences malespecific VIC myofibroblast activation and osteoblast-like differentiation in response to extracellular mechanical cues. Primary VICs from porcine sources have long been utilized to evaluate myofibroblast activation and osteogenic differentiation processes in AVS in response to different bulk substrate stiffnesses 28,[34][35][36][37][38][39] . For example, in response to tissue culture plastic (elastic modulus, E ~ 1 GPa), VICs automatically activate to myofibroblasts through the expression of ɑ-SMA stress fibers 26 .…”

“…Force-deformation (F-δ) data were calculated using F-d curves by subtracting the initial cantilever deflection. To determine Young's modulus E at each node, the loading portion of each F-δ curve was fit to an analytical model for a rigid conical tip in contact with an elastic half-space (38), i.e., F=(2/π)(E/1−ν 2 )(tanα)δ 2 , using angle α determined from SEM images, an assumed Poisson's ratio for the hydrogel (ν = 0.5), and E as the sole fitting parameter.…”

Healthy human induced pluripotent stem cell-derived cardiomyocytes exhibit sex dimorphism even without the addition of hormones

“…Donor hearts associated with underlying coronary artery disease, impaired left ventricular function (ejection fraction <50%), known bacteremia, viral hepatitis or HIV, or anticipated cold ischemic time of >6 hours were excluded. The aLVCF isolation was performed as previously described [77][78][79][80] . Briefly, hearts were flushed with ice-cold cardioplegia solution, excised and immediately submerged in ice-cold cardioplegia solution, and transported on ice.…”