EFFECTS OF TOPICAL TRETINOIN ON NON-SUN-EXPOSED PROTECTED SKIN OF THEELDERLY

Background: Topical tretinoin can alter some cutaneous structural alte rations induced by excessive exposure to sunlight. Most human studies have focused on photodamaged or photoaged skin. Little, if any, inform ation is available on the effects of tretinoin on chronologically or ' 'intrinsically'' aged human skin. Objective: Our purpose was to charac terize the clinical and structural changes in non-sun-exposed skin aft er long-term topical treatment with tretinoin. Methods. Six white wome n, 68 to 79 years of age, applied 0.025% tretinoin cream to the inner aspect of one thigh and vehicle cream to the opposite side, once daily for 9 months. Biopsy specimens were processed for histochemistry by l ight microscopy and for ultrastructural analysis by transmission elect ron microscopy. Results: Tretinoin treatment produced a marked increas e in the viable epidermal thickness and resulted in a more undulating dermoepidermal junction with prominent rete ridges. Return to a more u niform size and electron density of the basal and spinous keratinocyte s was also noted. Dermal changes included increases in glycosaminoglyc an deposition, elastic fibers, and new blood vessel formation. Conclus ion: Tretinoin substantially altered the involutional structural chang es in intrinsically aged protected skin. The magnitude of the changes may be even greater than those described for photodamaged skin.