Figure 1.

Progressive loss of HA from the dermis of chronically UVB-irradiated mice. Shaved C57/BL6 mice were either sham-irradiated or UVB-irradiated (three times per week, 3 MED ∼210 mJ/cm²), and consecutive skin biopsies were collected (see Materials and Methods). HA was detected by affinity histochemistry using biotinylated HAbP. A: Experimental design. B: HA staining. Top: Intrinsic aging; sham-irradiated controls at 150, 300, and 400 days. Bottom: Extrinsic aging; UVB-irradiated C57/BL6 mice at 150, 300, and 400 days. Arrows indicate the HA-rich zone in the papillary dermis where loss of HA is strongest. C: Densitometric quantification of HA staining, controls, n = 7, and UVB, n = 8; *P < 0.05 intrinsic aging versus UVB at 400 days (two-way analysis of variance). D: Biochemical quantification of HA in the dermis of controls versus UVB-irradiated skin at 400 days; mean ± SEM, controls, n = 4, and UVB, n = 5; *P < 0.05 (t-test). Original magnifications, ×100.