Identification of cardioprotective factors produced by fetal mesenchymal stem cells through a combined transcriptomic and proteomic approach.

Background: mesenchymal stem cells of fetal origin (F-MSC) can be isolated from the amniotic membrane of human placenta. We have data showing that F-MSC exert remarkable cardioprotective and proangiogenic effects through paracrine mechanisms. However, the complete nature and scope of the soluble mediators of cardioprotection have not been investigated yet. Methods: F-MSC were isolated from human term placenta. Human dermal fibroblasts were used as control population. Total RNA and proteins were extracted from cultured F-MSC (N=10) and fibroblasts (n=10) after 48 hrs of serum deprivation. Genome-wide expression profiling was performed on RNA samples with Illumina platform. Proteins extracted from both cell populations were analyzed by liquid chromatography-Fourier transform mass spectrometry (LC-FTMS). Results: whole-transcriptome gene expression analysis revealed that 647 genes are significantly over-expressed in F-MSC vs fibroblasts. Among these genes, 131 are up-regulated more than 2 fold in F-MSC. Computational analysis led to the identification of 32 genes encoding for secreted factors. Among them, the known cardioprotective factors Midkine (MDK) and SPARC are highly up-regulated in F-MSC vs fibroblasts. qPCR confirmed that MDK (+8 fold, p<0.01) and SPARC (+5.8, p<0.01) are up-regulated in F-MSC. Intriguingly, the role of the majority of the identified secreted factors in heart repair is still unknown. LC-FTMS proteomic analysis identified 266 proteins significantly up-regulated in F-MSC vs fibroblasts, including 22 secreted proteins. Some of these candidates may have a potential beneficial role in heart repair. In particular, Pentraxin-3 (PTX3) and Galectin-1 (GAL1) emerged as putative mediators of the cardioprotective effects exerted by F-MSC. Conclusion: using a combined transcriptomic and proteomic approach we identified known and novel putative cardioprotective factors produced by F-MSC. In particular, MDK, SPARC, PTX3 and GAL1 seem strong candidates. Further studies will help to fully dissect their role in myocardial repair.