The effect of thyroid hormone-dependent dermal fibroblast proliferation: an investigation of connective tissue growth factor and proliferative cell nuclear antigen

Abstract

Thyroid hormone has significant impact on skin homeostasis and cutaneous wound healing. Previous research has demonstrated both in vitro proliferation of keratinocytes and fibroblasts and in vivo stimulation of epidermal and dermal layers in response to triiodothyronine (T3) administration. However, the physiological mechanism of action involving T3 signaling and the specific intermediate factors of T3-induced cell proliferation are poorly understood. Currently, there is no working model of T3-dependent dermal fibroblast proliferation. In order to gain a more complete understanding of thyroid hormone regulation in wound healing, two known proliferative growth factors, connective tissue growth factor (CTGF) and proliferative cell nuclear antigen (PCNA), were chosen as potential mediators of T3-stimulated fibroblast proliferation. In vitro dermal fibroblast cultures were dosed with one of three experimental T3 concentrations (10-9 M, 10-8 M and 10-7 M) and western blot analysis was conducted to determine whether CTGF and PCNA expression are regulated by T3 stimulation. The results indicated no significant change in CTGF or PCNA expression dependent on T3 concentration. The implications of the findings were addressed and suggestions for future research directions have been proposed. It is still unclear which growth factors are involved in T3-regulated fibroblast proliferation. Once these mediators are identified, it will be possible to construct a mechanism of action to integrate the findings and ultimately develop a complete understanding of cutaneous physiology.