Small Extracellular Vesicles from Human Bone Marrow Mesenchymal Stromal Cells enhance migration and regulate gene expression of reparative mechanisms in human dermal fibroblasts

Studies have showed that mesenchymal stromal cells (MSCs) could secrete a variety of bioactive particles, including small extracellular vesicles (sEVs), a type of membrane bound vesicle produced by cells, that might be a key intermediate to the beneficial paracrine effects of MSC therapy. In this study, we harvested the conditioned medium (CM) from both human bone marrow mesenchymal stromal cells (hBM-MSCs) and normal human dermal fibroblasts (NHDFs), fractionated CM of each into the sEV fraction and non-small extracellular vesicle (NsEV) fraction and compared their functions on NHDF-based migration and proliferation assays, as crucial processes in wound healing, coupled with transcriptomic analysis through mRNA sequencing to assess the regulation on gene expression of the recipient NHDFs by secretome exposure. Our findings show that both sEV and NsEV as well as CM from hBM-MSCs showed an overall promotive effect on migration behaviour of NHDFs, but MSC-sEV seems to be more potent for NHDF migration among different MSC secretome fractions and is also superior in effect to the corresponding sEVs produced by the recipient NHDFs (HDF-sEV). Gene ontology analysis revealed enrichment of pathways related to migration, corroborating in vitro results; changes in genes within the regulation of proliferation pathway were also significant. Our study provides referential significance for the choice of cellular secretome fractions to be used in wound healing studies and trials. The secretome fractionation and functional comparison strategy using cell-based model and comparative transcriptomics analysis would be a useful tool for comprehensive functional evaluation of cellular secretome.