CHRONIC SUN EXPOSURE ALTERS BOTH THE CONTENT AND DISTRIBUTION OF DERMAL GLYCOSAMINOGLYCANS

Chronic sun exposure leads to structural and functional alterations in exposed skin, Photoageing is a process distinct from the changes taki ng place due to chronological ageing, Unique alterations in the dermal extracellular matrix occur as a result of photoageing and are respons ible for many of these physiological changes taking place in sun-damag ed skin, Accompanying the deposition of abnormal elastic tissue, or so lar elastosis, are significant alterations in dermal glycosaminoglycan s (GAGs), Accumulation of GAGs as a result of photoageing, as demonstr ated in both humans and animal models of photoageing, seems almost par adoxical in view of the large amounts of GAGs present in the skin of n ewborns, making their skin well hydrated and supple, in sharp contrast to the weathered appearance of photoaged skin, We investigate the rel ative GAG content of photoaged skin using immunoperoxidase stains spec ific for hyaluronic acid and chondroitin sulphate, and determine the l ocation of these GAGs using confocal laser scanning microscopy. Our re sults demonstrate significant increases in GAG staining in sun-damaged vs. sun-protected skin from the same individuals, as measured by comp uter-based image analysis, Furthermore, confocal laser scanning micros copy reveals that the increased dermal GAGs in sun-damaged skin are de posited on the elastotic material of the superficial dermis of photoda maged skin, and not between collagen and elastic fibres as in normal s kin. The abnormal location of GAGs on these fibres may explain the app arent paradoxical weathered appearance of photodamaged skin despite in creased GAGs.