Induction of leptin expression in orbital preadipocyte fibroblasts.

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

• Level A · Stronger Clinical Evidence
• Level B · Emerging clinical evidence with positive signals
• Level C · Early human research exploring benefits
• Level D · Scientific groundwork from lab and animal studies
• Emerging · Emerging topic under active research

Abstract (original English)

Graves' ophthalmopathy (GO) is an autoimmune disease characterized by an increase in the volume of the orbital fatty/connective tissues and extraocular muscles. This volume change is due to expansion of the adipose tissues and to accumulation of glycosaminoglycans and edema within the connective tissues of the orbit. We have shown previously that a subpopulation of confluent human orbital preadipocyte fibroblasts can be induced in vitro to differentiate into cells with morphological features of adipocytes and that these cultures express functional thyrotropin receptor (TSHR). In order to identify and study these cells further, we examined the expression of leptin protein and TSHR and leptin mRNA in these cultures. Using immunocytochemistry with objective measurement of immunofluorescent staining intensity on digitized microscopic images, we determined leptin protein expression to be 6 to 37 times greater in differentiated cultures than in control cultures. In addition, we showed that the expression of both genes is enhanced in differentiated cultures. We suggest that an unknown humoral stimulus, present in Graves' disease, might act to induce the differentiation of normal orbital fibroblasts into TSHR-bearing adipocytes. This process would be expected to result in expansion of the orbital adipose tissues and increased TSHR expression within the orbit.

Evidence level

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

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