Despite increasing experimental evidence, the antifibrotic potential of platelet rich plasma (PRP) remains controversial and its action mechanisms are not fully clarified.

This short report extends our previous research on PRP capability to prevent the in vitro differentiation of fibroblasts towards myofibroblasts, the key effectors of fibrosis, induced by the pro-fibrotic agent transforming growth factor (TGF)-β1. In particular, we focused on the involvement of vascular endothelial growth factor (VEGF)-A/VEGF Receptor (R)-mediated signalling in PRP-induced fibroblast response highlighting gap junction (GJ) features.

Electrophysiological and morphological analyses revealed that PRP hindered morpho-functional differentiation of both NIH/3T3 and human primary adult skin fibroblasts towards myofibroblasts as judged by the analysis of membrane phenomena, α-smooth muscle actin and vinculin expression and cell morphology. VEGF-A neutralization by blocking antibodies or pharmacological VEGFR inhibition by KRN633 in TGF-β1-treated fibroblasts prevented the PRP-promoted effects such as the reduction of voltage-dependent transjunctional currents in cell pairs and a decreased expression of connexin (Cx) 43, the typical Cx isoform forming voltage-dependent connexons. The role of VEGF-A in inhibiting these events was confirmed by treating TGF-β1-stimulated fibroblasts with soluble VEGF-A. The results obtained when cells were differentiated using KRN633 alone suggest an antagonistic cross-talk between TGF-β1 and VEGFR. In conclusion, this study identifies for the first time GJ currents as crucial targets in the VEGF-A/VEGFR-mediated antifibrotic pathway and contributes to bring new insights into mechanisms behind PRP action on preventing fibroblast to myofibroblast differentiation.

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