Background Vascular changes are consistent early findings in SSc and often proceed the development of fibrosis. Despite a severe reduction in the capillary density, signs of neoangiogenesis cannot be detected.
Objectives To examine the role of VEGF and its receptors in the impaired angiogenesis of SSc.
Methods Skin pO2 was measured intradermally using the pO2 histograph in 13 patients with SSc and in 5 healthy controls. Cultured SSc and normal skin fibroblasts were exposed to hypoxia and analysed for VEGF mRNA by real-time PCR (TaqMan). Immunohistochemistry with anti-VEGF-Receptor-1 and anti-VEGF-Receptor-2 antibodies was performed on skin biopsies of SSc patients and healthy controls. Serum samples of 47 patients with SSc and 21 healthy controls were analysed for VEGF by ELISA and correlated with clinical parameters.
Results PO2 values from involved skin of SSc patients (23,7 ± 2,1 mmHg) were significantly lower compared to healthy controls (33,6 ± 4,1 mmHg) and non-involved skin areas (37,8 ± 8,6 mmHg, p < 0.05). After hypoxic exposure of cultured fibroblasts, VEGF mRNA was found to be upregulated compared to normoxic controls in SSc (3,7 ± 1,7 fold) and normal skin fibroblasts (3,0 ± 1,8 fold). The bioavailability of VEGF was not reduced, since the expression of VEGF-Receptor-1 and VEGF-Receptor-2 was found on endothelial cells of 4/5 patients with SSc, whereas no signal could be detected in healthy controls. In addition to the overexpression of VEGF mRNA in skin samples, serum levels of VEGF protein were significantly higher in SSc patients compared to healthy controls (mean 461 pg/ml, range 93–1153 pg/ml vs. 106 pg/ml, range 0–500 pg/ml, p < 0.001). Interestingly, levels of VEGF were upregulated in patients with pre-SSc (clinical evidence for SSc without fulfilling ACR criteria, mean 451 pg/ml, range 230–601 pg/ml, p < 0.05) and in patients with early disease stages (disease duration < 2 years, mean 569 pg/ml, range 135–1013 pg/ml, p < 0.01). Patients with diffuse disease and the presence of fingertip ulcers had higher levels of VEGF (mean 339 pg/ml, range 93–714 pg/ml) than healthy controls, but highly significant lower levels than patients without fingertip ulcers (mean 655 pg/ml, range 281–1151 pg/ml, p < 0.001).
Conclusion Our results suggest a hypoxia mediated activation of the VEGF/VEGF-receptor axis in SSc. The correlation with clinical parameters indicate that elevated levels of VEGF are a feature of early disease stages and might be protective against the development of fingertip ulcers. Since the feasibility of a treatment with VEGF has just been approved in other ischaemic diseases, the application of VEGF may be a therapeutic option for the vascular insufficiency in SSc.