Impaired Endothelium-Mesenchymal Stem Cells Cross-talk in Systemic Sclerosis: a Link Between Vascular and Fibrotic Features

Introduction: To assess if an impaired cross-talk between endothelial cells (ECs) and perivascular/multipotentmesenchymal stem cells (MSCs) might induce a perturbation of vascular repair and leading to a phenotypic switchof MSC toward myofibroblast in Systemic Sclerosis (SSc).Methods: We investigated different angiogenic and profibrotic molecules in a tridimentional matrigel assay,performing co-cultures with endothelial cells (ECs) and bone marrow derived MSCs from patients and healthycontrols (HC). After 48 hours of co-culture, cells were sorted and analyzed for mRNA and protein expression.Results: ECs-SSc showed a decreased tube formation ability which is not improved by co-cultures with differentMSCs. After sorting, we showed: i. an increased production of vascular endothelial growth factor A (VEGF-A) inSSc-MSCs when co-cultured with SSc-ECs; ii. an increased level of transforming growth factor beta (TGF-β) andplatelet growth factor BB (PDGF-BB) in SSc-ECs when co-cultured with both HC- and SSc-MSCs; iii. an increase ofTGF-β, PDGF-R, alpha smooth muscle actin (α-SMA) and collagen 1 (Col1) in both HC- and SSc-MSCs whenco-cultured with SSc-ECs.Conclusion: We showed that during SSc, the ECs-MSCs crosstalk resulted in an altered expression of differentmolecules involved in the angiogenic processes, and mainly SSc-ECs seem to modulate the phenotypic switch ofperivascular MSCs toward a myofibroblast population, thus supporting the fibrotic process.