CHANGES IN STRATUM-CORNEUM LIPID AND DESMOSOME STRUCTURE TOGETHER WITH WATER BARRIER FUNCTION DURING MECHANICAL-STRESS

The elastic properties of the stratum corneum have been examined by ma ny investigators, bur the morphological evidence for changes in the st ructure of stratum corneum cohesive elements, lipids and desmosomes, d uring mechanical extension remains sparse. Additionally, little is kno wn of the effect of mechanical stress on stratum corneum water barrier function. In this study we have examined in detail changes in the str ucture of the stratum corneum intercellular lipids and desmosomes duri ng linear extension studies on isolated stratum corneum in vitro. Ultr astructural changes have been investigated by electron microscopy, and barrier function has been assessed by measuring water loss through th e tissue. Initially, at low extensions of the stratum corneum the stru cture of the intercellular bilayer lipids appeared normal, during furt her extension their membrane structure became disrupted, and with cont inued extension they became progressively disorganized. Desmosomes, by comparison, were more resilient structures, only being perturbed afte r large extensions during which intercorneocyte desmosomal links were observed to rupture just before the complete fracture of the tissue. T hese events were associated with increased water loss through the stra tum corneum. Ii these in vitro events are paralleled in vivo, it appea rs that stratum corneum lipids are sufficiently fluid to maintain barr ier function during small extensions of the skin surface. However, fol lowing large extensions the structural changes could lead to perturbed water barrier function, desmosome rupture, and aberrant desquamation, resulting in the appearance of xerotic skin conditions.