Immunoglobulin G of patients with circumscribed pretibial myxedema of Graves' disease stimulates proteoglycan synthesis in human skin fibroblasts in culture

Abstract

nor ophthalmopathy. Human skin fibroblasts were incubated with the IgGs and labeled with [35S]sulfate. The medium and cell layer were separated and the proteoglycan was extracted. The 35S radioactivity in the proteoglycan fraction was measured. Compared with normal IgGs or with those of Graves' disease without PTM or ophthalmopathy, PTM IgGs significantly increased the incorporation of the 35S into the proteoglycan. The effect of PTM IgG was dose-dependent. As PTM IgG did not alter degradation of the 35S labeled proteoglycan, an increase in 35S incorporation reflects increased synthesis. The effect was mediated through a mechanism other than adenylate cyclase activation. The present study demonstrates the presence of an autoantibody in PTM IgG that stimulates proteoglycan production through human skin fibroblasts. This is not correlated with the thyroid stimulating antibody activity. It is suggested that the activity of this antibody leads to the development of PTM.Circumscribed pretibial myxedema (PTM) is a cutaneous complication occasionally associated with Graves' dis¬ ease. Histochemical examination of the biopsied speci¬ men showed the accumulation of hyaluronic acid and proteoglycan (1, 2). In a previous paper, we examined the proteoglycans extracted from the affected skin and found that a large amount of dermatan sulfate proteog¬ lycan had accumulated (3). It is widely accepted that fibroblasts are the source of hyaluronic acid and proteo¬ glycan synthesis, because skin fibroblasts actively syn¬ thesize both of them in culture. It is tempting to speculate that an autoantibody IgG produced in Graves' disease patients may stimulate skin fibroblasts to synthesize excess amounts of hyaluronic acid and proteoglycan.However, attempts to show that the sera of PTM patients stimulate proteoglycan synthesis in human skin fibro¬ blasts in culture have yielded conflicting results (3-13). For example, Joliffe et al. (4) and Cheung et al. (5) reported that serum components of PTM patients could stimulate glycosaminoglycan synthesis in human skin fibroblasts in culture. On the other hand, Rotella and his associates reported that the IgG of PTM patients stimu-lated glycosaminoglycan synthesis in rat thyroid cells but not in human skin fibroblasts, although they showed that PTM IgG stimulates collagen synthesis in human skin fibroblasts in culture (6-12). A recent report by Tao et al. also showed that glycosaminoglycan synthesis in cultured human skin fibroblasts was not stimulated by the sera of PTM patients which contained autoantibodies capable of stimulating thyroid tissue (13). We wondered if there was an antibody IgG in patients with PTM capable of stimulating proteoglycan synthesis in human skin fibroblasts in culture, but that the effect was masked either by serum-derived growth factors or by limitations of the methods employed. In the present study, we examined this aspect-no serum component other than IgG was included, except for bovine serum albumin (BSA)-employing the recently developed methods for proteoglycan...

Effects of Dibutyryl Cyclic AMP on Hyaluronan and Proteoglycan Synthesis by Retroocular Tissue Fibrobrasts in Culture.

“…These observations emphasize that retroocular tissue fibroblasts have a unique character in regard to glycosaminoglycan synthesis when compared with adult skin fibroblasts. Although there was observed an increase in proteoglycan synthesis by adult skin fibroblasts culture in the present experiments, the results were apparently contradictory to our previous reports [12], in which we reported that Bt2 cAMP failed to stimulate proteoglycan synthesis. The discrepancy may be due to the origin of the skin fibroblasts: in our previous experiments, fibroblasts were obtained from the lower leg of a 14-year-old Japanese female while in the present experiments fibroblasts were from either the left thigh of a 66-year-old black male (case 5) or some unidentified part of his body (case 4).…”

Hyaluronan in skin

“…Skin biopsies from the lesions show high amounts of glycosaminoglycans, especially HYA [27]. It has been suggested that a circulating IgG antibody stimulates the local skin fibroblasts to produce HYA [28].…”

Echographic diagnosis of pretibial myxedema in patients with autoimmune thyroid disease

“…Mucin is made up of acid glycosaminoglycans and is a compound with considerable water-binding capacity (6,7) produced by dermal fibroblasts. Although in patients with AITD the presence of PTM is generally associated with circulating thyroid-stimulating immunoglobulins (2,8), experiments conducted to identify fibroblast-stimulating serum factors that are specific for 'Presented in part at the 75th Annual Meeting of the American Endocrine Society, Las Vegas, 9-12 June, 1993. the pathogenesis of the dermopathy have yielded inconclusive results (1,(9)(10)(11). The presence of PTM is generally observed on clinical examination and may be confirmed only by histo¬ logical examination of a biopsied specimen of pretibial skin, which represents the gold standard for the diagnosis.…”