Effect of age and anatomical site on density of sensory innervation in human epidermis.
BACKGROUND
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.


OBJECTIVE
To evaluate epidermal innervation according to age and anatomical site.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Besné
Isabelle
I
Direction des Science du Vivant, L'Oréal Recherche, Clichy, France. ibesne@recherche.loreal.com
Descombes
Caroline
C
Breton
Lionel
L
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D046508:Culture Techniques; D004817:Epidermis / Q000294:innervation* / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D009411:Nerve Endings; D009412:Nerve Fibers / Q000648:ultrastructure*; D011336:Probability; D012307:Risk Factors; D012677:Sensation / Q000502:physiology*; D012680:Sensitivity and Specificity; D015595:Skin Aging / Q000473:pathology*; D018709:Statistics, Nonparametric