Aging leads to decline of multiple cutaneous physiological functions
including decreased sweating, immune responsiveness, thermoregulation, DNA
repair, and sensory and tactile perception. Interestingly, sensory perception,
like that for pain or spatial acuity, varies in different body parts.
To evaluate epidermal innervation according to age and anatomical site.
Eighty-two biopsy samples from surgical procedures involving 82 patients
of different ages (20-93 years) were analyzed. Four anatomical sites were
examined: 2 from facial areas (upper eyelid and preauricular area) and 2 from
truncal areas (abdomen and mammary area). Epidermal innervation was detected
using a marker of neural cells, the protein gene product 9.5. The basement
membrane was stained with type IV collagen antibodies. The epidermal area
occupied by nerve endings was then calculated using image analysis.
A trend displaying age-associated decreased epidermal innervation of
facial skin was found. Epidermal innervation of abdominal skin did not change
with age, and an age-associated increased innervation was observed in mammary
skin. Also, the number of epidermal nerves in facial areas tested (palpebral
and preauricular areas) was significantly higher than their number in the
abdomen and mammary area. Eyelid epidermis showed the highest ratio of nerve
fiber surface to epidermal surface.
Epidermal nerve density variations could explain the different sensitivity
threshold in different parts of the body. Decreased spatial discrimination
with aging may be associated with decreased epidermal nerve density.