RGS5 and scleroderma: In ourin vitro differentiated SSc-ECs, while the expression ofMMP1 was 2.4-fold upregulated in S1- EC, MMP9expression showed 12-fold decrease compared to C1-EC, suggesting a dysregulation ofMMP1 and MMP9 expression in S1-EC (Fig.3F).Scleroderma vessels have abnormal ECs which express regulator of G protein signaling 5(RGS5), a protein associated with vascular rarefaction, but lack normal VE-cadherinexpression (19).