Scleroderma Mesenchymal Stem Cells display a different phenotype from healthy controls; implications for regenerative medicine

Vascular involvement is a key feature of Systemic sclerosis (SSc). Although the pericytes/endothelial cells (ECs) cross-talk regulates vessels formation, no evidences about the pericytes contribution to ineffective angiogenesis in SSc are available. Recent findings showed similarities between pericytes and Bone Marrow Mesenchymal Stem Cells (BM-MSCs). Due to difficulties in pericytes isolation, this work explores the possibility to use BM-MSCs as pericytes surrogate, clarifying their role in supporting neo-angiogenesis during SSc. To demonstrate their potential to normally differentiate into pericytes, both SSc and healthy controls (HC) BM-MSCs were treated with TGF-beta and PDGF-BB. The expression of pericytes specific markers (alpha-SMA, NG2, RGS5 and desmin) was assessed by qPCR, western blot, and immunofluorescence; chemioinvasion and capillary morphogenesis were also performed. Cell-sorting of BM-MSCs co-cultured with HC-ECs was used to identify a possible change in contractile proteins genes expression. We showed that BM-MSCs isolated from SSc patients displayed an up-regulation of alpha-SMA and SM22 alpha genes and a reduced proliferative activity. Moreover during SSc, both TGF-beta and PDGF-BB can specifically modulate BM-MSCs toward pericytes. TGF-beta was found interfering with the PDGF-BB effects. Using BM-MSCs/MVECs co-culture system we observed that SSc BM-MSCs improve ECs tube formation in stressed condition, and BM-MSCs, sorted after co-culture, showed a reduced alpha-SMA and SM22 alpha gene expression. BM-MSCs from SSc patients behave as pericytes. They display a more mature and myofibroblast-like phenotype, probably related to microenvironmental cues operating during the disease. After their co-culture with HC-MVECs, SSc BM-MSCs underwent to a phenotypic modulation which re-programs these cells toward a pro-angiogenic behaviour.