Impaired lymphangiogenesis due to excess vascular endothelial growth factor-D/Flt-4 signalling in the skin of patients with systemic sclerosis

P>Background Vascular abnormalities are one of the primary pathological components of systemic sclerosis (SSc). However, it has not been determined if there are also abnormalities in the formation of lymphatic vessels in SSc. Objective To evaluate lymphangiogenic activity in SSc skin. Methods The numbers of D2-40-positive lymphatic vessels in skin specimens from healthy control subjects and patients with SSc were counted and compared. Quantitative real-time polymerase chain reaction (PCR) was performed to determine mRNA levels of vascular endothelial growth factor (VEGF)-D and Flt-4 (fms-related tyrosine kinase 4, VEGFR-3, one of the receptors for VEGF-D) in the skin. Serum VEGF-D levels were measured with specific enzyme-linked immunosorbent assays. Results The number of lymphatic vessels in patients with SSc was significantly decreased compared with healthy control subjects. Mean relative transcript levels of FIGF (VEGF-D) and FLT4 (Flt-4) in skin tissue from patients with SSc were significantly increased compared with healthy control subjects. By the analysis of the association between serum VEGF-D levels and the clinical or laboratory features, we found that patients with SSc with higher serum VEGF-D levels more frequently have skin ulcers than those with normal VEGF-D levels. Conclusions A systemic increase of VEGF-D, as well as local overexpression of FIGF and FLT4, may be the cause of disturbed lymphangiogenesis in SSc skin and play a role in the pathogenesis of SSc. We showed the possibility that regulation of VEGF-D/Flt-4 signalling could lead to new treatment of skin ulcers in SSc by controlling the formation of lymphatic vessels.