Expression of stem cell factor in the lesional skin of systemic sclerosis

Mast cells are thought to play an important role in the pathogenesis of systemic sclerosis (SSc), although their significance is still unknown. As mast cells are increased in number in the lesional skin of the early stage of scleroderma, we addressed the question whether expression of stem cell factor (SCF), a mast cell growth factor, is upregulated in the lesional skin.

Immunohistochemical analysis of SCF was performed in paraffin-embedded skin sections from the lesions of 18 patients with SSc (13 in the edematous and 5 in the sclerotic phase) and from normal skin of 5 subjects. SCF messenger RNA expression was also examined on cultured fibroblasts derived from SSc by using reverse-transcriptase polymerase chain reaction.

Immunostaining showed focal expression for SCF in fibroblast-like spindle-shaped cells, mast cells, keratinocytes and endothelial cells. SCF-positive spindle-shaped cells were significantly increased in the reticular dermis in the early edematous stage of SSc (33.7 +/- 13.0/mm2) as compared with normal skin (18.3 +/- 4. 2/mm2; p <0.05); however, there was no significant difference between the sclerotic phase (18.9 +/- 6.9/mm2) and normal skin. mRNA expression of SCF was detected both in cultured scleroderma-derived and normal skin-derived fibroblasts.

These results may suggest that SCF plays a role in the fibrotic process in early-stage SSc.