Immunohistochemical clues at aging of the skin microvascular unit

Skin aging is a multifaceted process influenced by various factors affecting at variable degree at different body sites. This study focused on the aging process affecting dermal dendrocytes and the microvasculature. We also explored the effect of substance P released by capsaicin because this neuropeptide is known to affect the microvasculature environment.

The first part of the present study was undertaken in two groups of 35 men who were younger than 30 years and older than 65 years, respectively. A skin biopsy was taken from the intact skin of a thigh during orthopedic surgical intervention after road accident. The second part of the study was performed on 30 men aged 65-68 years. They applied once daily a 0.05% capsaicin gel and the vehicle in a randomized design on the volar forearms. A skin biopsy was taken at inclusion and after a 5-month treatment phase. Immunohistochemistry was performed using a panel of antibodies. Dermal cells were distinguished according to the presence of factor XIIIa, CD34 or thrombomodulin. Blood and lymphatic vessels were studied by Ulex europaeus agglutinin-1, human podoplanin, human vascular endothelial growth factor-C (H-VEGF-C) and alpha-actin immunoreactivities.

In the study phase 1, a significant decrease in thrombomodulin-positive cells and vascularity were evidenced in the aged group. In the study phase 2, capsaicin appeared to boost the factor XIIIa-positive dendrocytes, the thrombomodulin-positive cells and the blood vessel network as well.

Specific subsets of the dermal dendrocyte populations and the blood microvasculature appear affected by aging. Capsaicin may limit these aging effects.