FIBRILLIN MICROFIBRILS ARE REDUCED IN SKIN EXHIBITING STRIAE-DISTENSAE

Striae distensae (striae: stretch marks) are a common disfiguring cond ition associated with continuous and progressive stretching of the ski n-as occurs during pregnancy. The pathogenesis of striae is unknown bu t probably relates to changes in those structures that provide skin wi th its tensile strength and elasticity Such structures are components of the extracellular matrix, including fibrillin, elastin and collagen s. Using a variety of histological techniques, we assessed the distrib ution of these extracellular matrix components in skin affected by str iae. Pregnant women were assessed for the presence of striae, and punc h biopsies were obtained from lesional striae and adjacent normal skin . Biopsies were processed for electron microscopy, light microscopy an d immunohistochemistry. For histological examination, 7 mu m frozen se ctions were stained so as to identify the elastic fibre network and gl ycosaminoglycans. Biopsies were also examined with a panel of polyclon al antibodies against collagens I and III, and fibrillin and elastin. Ultrastructural analysis revealed alterations in the appearance of ski n affected by striae compared with that of normal skin in that the der mal matrix of striae was looser and more floccular. Light microscopy r evealed an increase in glycosaminoglycan content in striae. Furthermor e, the number of vertical fibrillin fibres subjacent to the dermal-epi dermal junction (DEJ) and elastin fibres in the papillary dermis was s ignificantly reduced in striae compared with normal skin. The orientat ion of elastin and fibrillin fibres in the deep dermis showed realignm ent in that the fibres ran parallel to the DEJ. However, no significan t alterations were observed in any other extracellular matrix componen ts. This study identifies a reorganization and diminution of the elast ic fibre network of skin affected by striae. Continuous strain on the dermal extracellular matrix, as occurs during pregnancy, may remodel t he elastic fibre network in susceptible individuals and manifest clini cally as striae distensae.