Investigation of gene expression changes in normal human dermal fibroblasts after exposure to bone marrow mesenchymal stromal cell secretome

Mesenchymal stromal cells (MSCs) are been widely investigated in clinical trials for several clinical conditions. It is known that these cells do not promote their effects by engrafment and differentiation, as they die shortly after intravenous administration. Extracellular vesicles (EVs) are membrane bound particles that carry bioactive lipids, peptides and nucleic acids and act in cell-cell communication. The aim of this study is to determine the transcriptomic effects of exposure of dermal fibroblasts to fractions of bone marrow MSCs, including conditioned medium (CM), non-small extracellular vesicles (NsEV), small extracellular vesicles (sEVs) and depleted medium (DM). Differential gene expression and gene ontology analysis showed that there enrichment of pathways related to migration and genes within the regulation of cell population proliferation pathway had their expression changed after exposure to MSC-sEVs. This indicates that MSC secretome promotes targeted gene expression change that can be of particular interest in wound healing studies and clinical trials. To study the effects of MSC secretome, we fractioned conditioned medium into non-small extracellular vesicles (nsEV, pellet obtained after centrifuging CM at 10,000 g for 40 minutes), and small extracellular vesicles (sEV, ultracentrifugation at 100,000 g for 90 minutes and washing pellet with PBS on a further ultracentrifugation at 100,000g). We then exposed normal human dermal fibroblasts to the different fractions of secretome for 48 hours; controls were cells exposed only to DMEM 1% Penicillin/Streptomycin. Total RNA was extracted and sent for mRNA sequencing at Novogene Limited (Cambridge, UK).