Table2_Identifying molecular and functional similarities and differences between human primary cardiac valve interstitial cells and ventricular fibroblasts.XLSX

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.

引言：成纤维细胞（fibroblasts）是一类间充质细胞，主要负责合成并维持细胞外基质（extracellular matrix, ECM），同时也是损伤应答的关键介导因子。在心脏中，瓣膜间质细胞（valve interstitial cells, VICs）是一类成纤维细胞亚群，负责维持心脏瓣膜的结构与功能。该类细胞与心肌成纤维细胞存在区域特异性差异，其中左心室心肌成纤维细胞（left ventricular cardiac fibroblasts, LVCFBs）定位于心肌层，且与心肌细胞紧密相邻。本研究假设这类成纤维细胞亚群在转录与功能层面存在显著差异。

方法：为比较此类成纤维细胞亚型，我们收集了患者匹配的人类原代瓣膜间质细胞与左心室心肌成纤维细胞样本，并开展了批量RNA测序、细胞外基质谱分析以及功能收缩与钙化实验。

结果：本研究鉴定出，相较于左心室心肌成纤维细胞，瓣膜间质细胞在蛋白水平上存在SUSD2的联合表达，在转录水平上存在MEOX2、EBF2与RHOU的差异表达，且证实这些基因的表达可用于区分这两类成纤维细胞亚群。我们发现，体外实验中瓣膜间质细胞与左心室心肌成纤维细胞的激活与收缩潜能相似，但瓣膜间质细胞在激活后碱性磷酸酶（alkaline phosphatase, ALP）活性升高，且在细胞基质蛋白的表达水平上更高，包括软骨寡聚蛋白与α2-赫曼斯-施密特糖蛋白，已有研究表明这两种蛋白均与钙化过程相关。

结论：本项对比转录组学、蛋白质组学与功能学研究为阐明瓣膜间质细胞与左心室心肌成纤维细胞之间的异同提供了新视角，将有助于理解区域特异性心脏病理、区分成纤维细胞原代亚群，以及制备区域特异性干细胞来源心肌成纤维细胞。