Age-related functional and structural changes in human dermo-epidermal junction components.
Cultured normal human keratinocytes obtained from 14 facial skin biopsies of donors aged 9-79 y were used to study the influence of donor age on the integrin receptors, cell adhesive properties in vitro, and type VII collagen synthesis. Immuno-spectrofluorimetric quantitation of integrins showed a decrease in the beta1- and beta4-subunits in low (0.08 mM) and high (1.8 mM) calcium conditions with aging. Calcium ions decreased the fluorescence intensity by relocating integrins at cell boundaries. Measurements of adhering cells showed that adhesion to bovine serum albumin-, type IV collagen- or laminin 1-coated plastic surfaces initially increased until donor age reached 30 y and then decreased. Specific adhesion to type IV collagen and laminin 1 did not vary with age, but the increase in adhesion to type IV collagen produced by manganese ions increased with age, suggesting an age-dependent feature of beta1 integrin. Synthesis of type VII collagen, increased or not by TGFbeta1 (10 ng per ml), did not vary with the donor age. Global normalized principal component analysis showed that variables related to integrins were strongly correlated, as were those of adhesion. Pre-embedding immunoelectron microscopy of freshly isolated keratinocytes showed that certain hemidesmosomes from aged cells had little or no reaction with anti-beta4-chain antibody. Post-embedding type IV collagen immunostaining and image analysis showed less type IV collagen in adult dermo-epidermal junctions. These findings indicate that there are structural and functional changes in the dermo-epidermal junction components with aging, probably giving a less effective epidermal anchoring system.