Background Scleroderma is a disease hallmarked by microangiopathy; the extensive avascular areas developing in the course of the disease are clinically associated with severe tissue hypoxia and the formation of digital ulcers. Tissue oxygenation is further impaired through the development of tissue fibrosis. The proangiogenic factor VEGF is upregulated in all stages of the disease with little effect on efficient neovascularization. Surprisingly, no correlation between the expression of VEGF and HIF-1a could be documented in scleroderma skin biopsies in previous reports.
Objectives The aim of this study was to investigate expression of HIF-1a and VEGF in naive scleroderma patients, and correlate histochemical findings with the capillaroscopic pattern and clinical manifestations.
Methods Skin biopsies from 9 patients with scleroderma (diffuse/ limited) were analysed and compared to 10 normal skin biopsies. Patients were informed prior to the biopsy and gave their consent. Mean age of the patients was 52,22±14,37 yrs, and median duration of the symptoms 28 months [4-120]. Autoantibody profile, capillaroscopic pattern and clinical manifestations, e.g. digital ulcerations, was recorded. Paraffin sections of 3μm were stained with Abs against HIF-1a and VEGF according to standardized protocols.
Results In the normal skin, there were rare immunoreactivecells for HIF-1a. In the dermis there was immunoreactivity of follicular keratinocytes of sweat and sebaceous glands and endothelial cells, in accordance with previously reported data. All skin biopsies from scleroderma patients were HIF-1a-positive. The staining was nuclear and it was observed throughout the keratinocytes of the epidermis. Nuclear expression of HIF-1a was also seen in sweat and sebaceous glands and in dermal inflammatory foci with distinct staining of endothelial cells and scattered staining of lymphocytes.
In the normal skin, immunostaining for VEGF was mainly observed in suprabasal keratinocytes. In the dermis there was immunoreactivity of endothelial cells. In patients with scleroderma, immunostaining of epidermal keratinocytes was seen in all cases. The immunoreactivity was cytoplasmic. Immunostaining was also observed in endothelial cells of the dermis.
No statistically significant differences in the expression of HIF-1a and VEGF, estimated semiquantitatively by immunohistochemistry, were recorded in patients at different stages at diagnosis according to capillaroscopic and clinical criteria.
Conclusions To date, and despite low pO2 values measured in the skin of patients with systemic sclerosis, no pathophysiological connection could be proven between clinical hypoxia and increased levels of the oxygen-sensitive alpha-subunit of HIF-1. Our study is the first to show potent constitutive expression and accumulation of HIF-1a in the skin of scleroderma patients, even in early stages of the disease. The patients included in this study were treatment-naïve, i.e. had not been previously exposed to any immuno- or vasomodulatory treatment. This observation contributes to the understanding of the pathophysiology of the disease. Further studies are needed in order to characterize downstream modulatory factors, which may interfere with efficient tissue neovascularization.
Disclosure of Interest None Declared