Mayourian Joshua, Cashman Timothy J, Ceholski Delaine K, Johnson Bryce V, Sachs David, Kaji Deepak A, Sahoo Susmita, Hare Joshua M, Hajjar Roger J, Sobie Eric A, Costa Kevin D
From the Cardiovascular Research Center (J.M., T.J.C., D.K.C., D.S., S.S., R.J.H., K.D.C.), Department of Developmental and Regenerative Biology (D.A.K.), and Department of Pharmacology and Systems Therapeutics (E.A.S.), Icahn School of Medicine at Mount Sinai, New York; Department of Medicine, University of Washington Seattle (B.V.J.); and The Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, FL (J.M.H.).
Circ Res. 2017 Aug 4;121(4):411-423. doi: 10.1161/CIRCRESAHA.117.310796. Epub 2017 Jun 22.
Myocardial delivery of human mesenchymal stem cells (hMSCs) is an emerging therapy for treating the failing heart. However, the relative effects of hMSC-mediated heterocellular coupling (HC) and paracrine signaling (PS) on human cardiac contractility and arrhythmogenicity remain unresolved.
The objective is to better understand hMSC PS and HC effects on human cardiac contractility and arrhythmogenicity by integrating experimental and computational approaches.
Extending our previous hMSC-cardiomyocyte HC computational model, we incorporated experimentally calibrated hMSC PS effects on cardiomyocyte L-type calcium channel/sarcoendoplasmic reticulum calcium-ATPase activity and cardiac tissue fibrosis. Excitation-contraction simulations of hMSC PS-only and combined HC+PS effects on human cardiomyocytes were representative of human engineered cardiac tissue (hECT) contractile function measurements under matched experimental treatments. Model simulations and hECTs both demonstrated that hMSC-mediated effects were most pronounced under PS-only conditions, where developed force increased ≈4-fold compared with non-hMSC-supplemented controls during physiological 1-Hz pacing. Simulations predicted contractility of isolated healthy and ischemic adult human cardiomyocytes would be minimally sensitive to hMSC HC, driven primarily by PS. Dominance of hMSC PS was also revealed in simulations of fibrotic cardiac tissue, where hMSC PS protected from potential proarrhythmic effects of HC at various levels of engraftment. Finally, to study the nature of the hMSC paracrine effects on contractility, proteomic analysis of hECT/hMSC conditioned media predicted activation of PI3K/Akt signaling, a recognized target of both soluble and exosomal fractions of the hMSC secretome. Treating hECTs with exosome-enriched, but not exosome-depleted, fractions of the hMSC secretome recapitulated the effects observed with hMSC conditioned media on hECT-developed force and expression of calcium-handling genes (eg, SERCA2a, L-type calcium channel).
Collectively, this integrated experimental and computational study helps unravel relative hMSC PS and HC effects on human cardiac contractility and arrhythmogenicity, and provides novel insight into the role of exosomes in hMSC paracrine-mediated effects on contractility.
将人间充质干细胞（hMSC）输送至心肌是一种新兴的治疗心力衰竭的方法。然而，hMSC介导的异细胞偶联（HC）和旁分泌信号传导（PS）对人体心脏收缩性和致心律失常性的相对影响仍未明确。
通过整合实验和计算方法，更好地了解hMSC的PS和HC对人体心脏收缩性和致心律失常性的影响。
在我们之前的hMSC-心肌细胞HC计算模型的基础上，我们纳入了经实验校准的hMSC的PS对心肌细胞L型钙通道/肌浆网钙-ATP酶活性以及心脏组织纤维化的影响。对仅hMSC的PS以及HC+PS联合作用于人心肌细胞的兴奋-收缩模拟，代表了在匹配的实验处理下对人体工程心脏组织（hECT）收缩功能的测量。模型模拟和hECT均表明，hMSC介导的效应在仅PS条件下最为显著，在生理1Hz起搏期间，与未添加hMSC的对照组相比，所产生的力量增加了约4倍。模拟预测，分离的健康和缺血成人心肌细胞的收缩性对hMSC的HC敏感性最低，主要由PS驱动。在纤维化心脏组织的模拟中也揭示了hMSC的PS占主导地位，其中hMSC的PS在不同植入水平下可保护免受HC潜在的促心律失常作用。最后，为了研究hMSC旁分泌对收缩性影响的本质，对hECT/hMSC条件培养基的蛋白质组分析预测PI3K/Akt信号通路被激活，这是hMSC分泌组的可溶性和外泌体部分公认的靶点。用hMSC分泌组的富含外泌体但非耗尽外泌体的部分处理hECT，重现了hMSC条件培养基对hECT产生的力量和钙处理基因（如SERCA2a、L型钙通道）表达的影响。
总体而言，这项整合实验和计算的研究有助于阐明hMSC介导的PS和HC对人体心脏收缩性和致心律失常性的相对影响，并为外泌体在hMSC旁分泌介导的收缩性影响中的作用提供了新的见解。
