The effects of thyroid hormone on wound healing

Abstract

Wound healing disorders affect between 3 and 6 million Americans every year. Treatment options are variable and often unsuccessful, resulting in amputation. However, one commonly used treatment option applies growth factors and proteins topically to the site of the wound to improve the rate of healing. More recently, a positive role for the topical administration of thyroid hormone has also proven effective. These findings are interesting considering the systemic role of thyroid hormone on the skin where in the absence of Graves’ disease, patients with thyrotoxicosis have thinner skin. Questions still remain about the contradictory role of systemic and topical administrations of thyroid hormone, but research suggests that the topical application of thyroid hormone could be a useful therapeutic agent in patients with wound healing disorders. Other than the keratin genes in keratinocytes, the molecular targets of thyroid hormone are unknown. The complexity of wound healing makes it challenging to determine which factors are directly or indirectly affected by thyroid hormone, however, the integrin-β1 family could be a likely target. The integrin-β1 proteins are expressed in both keratinocytes and fibroblasts and play an important role in fibrogenesis. In addition, conditional knockouts for the integrin-β1 gene display reduced rates of wound healing. Therefore, the expression of integrin-β1 protein was analyzed by Western Blotting to determine whether fibroblasts dosed with thyroid hormone caused an increase in integrin-β1 expression. The experiment revealed that the expression of integrin-β1 is dependent on the presence of thyroid hormone. Furthermore, integrin-β1 is expressed maximally at physiological concentrations of thyroid hormone. These results suggest that thyroid hormone may improve wound healing by stimulating expression of integrin-β1 proteins.