Combined transcriptomic and proteomic approach identifies several putative paracrine factors of fetal mesenchymal stem cells.

Background: Mesenchymal stem cells of fetal origin (F-MSCs) can be isolated from the amniotic membrane of human placenta. Our results showed that F-MSCs exert remarkable protect cytoprotection and promote angiogenesis through paracrine mechanisms. However, the complete nature and scope of the soluble mediators of cardioprotection have not been uncovered yet. Methods: F-MSCs were isolated from human term placenta. Human dermal fibroblasts were used as control population. Total RNA and proteins were extracted from cultured F-MSCs and fibroblasts (n=8) after 48 hrs of serum deprivation. Genome-wide expression profiling was performed on RNA samples with Illumina microarray platform containing 48,813 different probes targeting 37,812 different genes. Proteins extracted from both cell populations were analyzed by liquid chromatography-Fourier transform mass spectrometry (LC-FTMS). Conditioned media from both cell population were analyzed by Human Angiogenesis Array I (Raybiotech). Results: Whole-transcriptome gene expression analysis revealed that 1831 genes were expressed at significantly different levels among F-MSCs and fibroblasts. 319 genes were up-regulated more than 2 folds in F-MSCs compared with fibroblasts. Among these, 60 encoded for known secreted factors (18 of which were up-regulated more than 5 fold in the F-MSC). Interestingly, the identified secreted proteins included several factors involved in the regulation of cell growth, proliferation and survival, extra-cellular matrix modulation and angiogenesis. Intriguingly, the function of several identified secreted factors is still undetermined. LC-FTMS proteomic analysis led to the identification of 886 proteins: among these 28 were uniquely expressed by the F-MSC and 266 significantly up-regulated in the F-MSCs compared with fibroblasts. Most of them are intracellular cytoskeletal components but several are proteins involved in cellular metabolic processes, angiogenesis and cytoprotection. Conclusion: The combined transcriptomic and proteomic approach led to the identification of several known and novel putative paracrine factors produced by F-MSC. Further studies will help to fully dissect their role in myocardial repair.