The effect of triiodothyronine on the expression of PDGF-BB in fibroblasts
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The thyroid gland consists of two types of cells that develop from distinct tissues. The parafollicular C-cells are derived from neural crest tissue and produce calcitonin, while the follicular cells produce thyroid hormone and are derived from endodermal tissue; thyroid hormone is the focus of this study. In the follicular cells, iodide is eventually metabolized into T4 and T3, with T4 being the primary production. Deiodinase 2 processes T4 into T3 because T3 serves the greatest physiological function. Thyroid hormone is crucial in maintaining basal metabolic rate and has a major effect on many organs, so in order for the body to optimally operate, thyroid hormone must be produced and utilized in a proper manner. However, the role of thyroid hormone in wound healing has not been properly addressed. The main steps in wound healing involve migration, proliferation, remodeling, and angiogenesis. Fibroblasts play a key role in all of these steps and hence, were the cells of choice in this study. Platelet derived growth factor- BB is critical in wound healing because it is potent in causing both the proliferation and migration of fibroblasts. In this study, we dosed fibroblasts with different concentrations of thyroid hormone in an attempt to see if the expression of PDGF-BB increased in fibroblasts dosed with thyroid hormone. Fibroblasts were passed, dosed with T3, lysed, and western blots were run to see if the expression of PDGF-BB changed depending on the concentration of T3. Previous studies conducted on mice and guinea pigs showed that an application of topical thyroid hormone cream onto wounds resulted in quicker healing. The next step is to find the individual mechanisms and proteins that thyroid hormone affects, using western blots. The T3 concentrations utilized were 10-7 M and 10-8 M and a control was used that contained fibroblasts with no thyroid hormone. The western blot films clearly showed an increase in the expression of PDGF-BB with the 10-7 M and 10-8 M fibroblasts compared to the control group. Thus, thyroid hormone could affect the migration and proliferation steps of wound healing through the expression of PDGF-BB. Unfortunately, this expression did not appear to be dose-dependent since the samples with less thyroid hormone, 10-8 M, contained an equal or heavier band than the 10-7 M samples. Hence, more experiments need to be run with more concentrations in order to obtain statistically significant data.
Thesis (M.A.)--Boston University