Altered properties of endothelial cells and mesenchymal stem cells underlying the development of scleroderma‐like vasculopathy in Klf5+/‐;Fli1+/‐ mice

OBJECTIVE We previously established a new animal model (Klf5+/- ;Fli1+/- mice) broadly recapitulating fundamental pathologic features of systemic sclerosis (SSc). SSc vasculopathy is believed to occur as a result of impaired vascular remodeling, but its detailed mechanism has remained unknown. To address this issue, we investigated the properties of dermal microvascular endothelial cells (DMECs), bone marrow-derived endothelial progenitor cells (BM-EPCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs), a precursor of pericytes, in Klf5+/- ;Fli1+/- mice. METHODS Neovascularization and angiogenesis were assessed by in vivo Matrigel plug assay and in vitro tube formation assay, respectively. The properties of BM-EPCs and BM-MSCs were assessed in in vitro studies. Dermal vasculature was visualized in vivo by FITC-dextran injection. RESULTS Neovascularization was diminished in skin-embedded Matrigel plug in Klf5+/- ;Fli1+/- mice. Klf5+/- ;Fli1+/- DMECs showed defective tubulogenic activity, decreased expression of VE-cadherin and CD31, and imbalance of Notch1/delta-like ligand 4, suggesting that angiogenesis and anastomosis are disturbed. Klf5+/- ;Fli1+/- BM-MSCs exhibited enhanced proliferation, migration and collagen production by transforming growth factor-β1, indicating the preferential differentiation into myofibroblasts rather than pericytes. Klf5+/- ;Fli1+/- BM-EPCs displayed the transition toward mesenchymal cells, suggesting that vasculogenesis is impaired. Wound healing was delayed in Klf5+/- ;Fli1+/- mice (15.67 ± 0.82 days versus 13.50 ± 0.84 days; P = 0.0017), and vascular network was poorly developed in wound scar tissue. CONCLUSION Klf5+/- ;Fli1+/- mice represent impaired neovascularization and vascular maturation similar to those of SSc at least partially due to the induction of SSc-like properties in DMECs, BM-EPCs and BM-MSCs, indicating the critical contribution of KLF5 and Fli1 deficiency in vascular cells and related precursors to SSc vasculopathy.