Reduced fibroblast interaction with intact collagen as a mechanism for depressed collagen synthesis in photodamaged skin.

This report provides evidence from a number of different approaches (i.e., comparison of cell shape in 1-microm sections of photodamaged versus healthy skin at the light microscopic level; comparison of cell shape and apposition to collagen fibrils in ultrathin sections of the same tissues examined by transmission electron microscopy, and fluorescence staining for adhesion site protein expression and actin filament architecture in frozen tissue sections) that dermal cells in healthy skin are attached to collagen fibrils over a large part of the cell border, have a flattened/spread (two-dimensional) appearance and have abundant actin in their cytoplasm. In contrast, cells in photodamaged skin are often in contact with fragmented collagen or amorphous debris rather than intact collagen, have a collapsed/elongated shape, and have a lower amount of actin. Collagen synthesis is reduced in severely photodamaged skin relative to collagen synthesis in corresponding sun-protected skin (N Engl J Med 329:530, 1993). We hypothesize that fibroblasts in severely damaged skin have less interaction with intact collagen and as a result experience a reduction in mechanical tension. Decreased collagen synthesis is (presumed to be) the result.