Paracrine effect of MSCs revealed by single cell gene expression assay in mouse infarcted hearts

Abstract

Mesenchymal stem cells (MSCs) have recently been demonstrated as a promising stem cell type to rescue damaged myocardium after acute infarction. One of the most important mechanisms underlying their therapeutic effects is the secretion of paracrine factors. However, the expression profile of paracrine factors of MSCs in infarcted hearts, especially at single cell level, is poorly defined. We aimed to depict the transcriptional profile of paracrine factors secreted by MSCs in vivo, with particular interest in the comparison between normal and infarcted hearts. MSCs were isolated and injected into mice hearts immediately after infarction surgery. Bioluminescence imaging indicated a proportion of cells still alive even up to 12 days post surgery. Paralleled with survived cells, cardiac function was significantly improved after MSCs injection compared to that in PBS-injected mice, indicated by echocardiography and MRI. Despite increased number of vessels in MSCs-injected hearts, endothelial cells and cardiomyocytes transdifferentiation were rarely observed in infarcted hearts 5 days after infarction. Furthermore, laser capture microdissection followed by high through-put real time PCR was employed in our study, uncovering that the injected MSCs, compared to local cardiomyocytes, displayed elevated levels of secreted factors. To further investigate the regulation of those factors, we performed single cell analysis to dissect the gene expression profile of 48 MSCs in infarcted and normal hearts, respectively. Consistent with the in vivo observation, a similar regulation pattern of those factors was detected in cultured MSCs. Our study, for the first time, elucidated gene expression profiles, as well as regulation of paracrine factors, of MSCs at single cell level in vivo, indicating that paracrine factors from MSCs account for the improvement of cardiac function after infarction.