[Thyroid hormone receptors in human skin during aging.]

Area of Science:

• Dermatology
• Endocrinology
• Cell Biology

Background:

• Skin aging is a complex process involving cellular changes.
• Thyroid hormones and their receptors play vital roles in development and cellular function.

Purpose of the Study:

• To investigate the age-related expression of thyroid hormone receptors (TRs) in human dermal fibroblasts.
• To determine the correlation between TR levels and fibroblast proliferation during skin aging.

Main Methods:

• Immunohistochemistry was used to assess TR-α and TR-β expression.
• Cell counting and proliferating cell nuclear antigen (PCNA) staining quantified fibroblast numbers and proliferation.
• Hematoxylin and eosin staining evaluated total fibroblast counts.

Main Results:

• TR-α and TR-β levels were highest during fetal development (20-40 weeks gestation).
• TR expression significantly decreased from birth to 40 years, stabilizing thereafter.
• Fibroblast numbers and PCNA-positive cells declined with age, particularly by 40 years.
• A strong association was found between reduced TR levels and decreased fibroblast proliferation and numbers.

Conclusions:

• Thyroid hormone receptors are significantly involved in the age-dependent decline of fibroblast number and proliferation in human dermis.
• These findings suggest TRs are key regulators of skin aging processes.