Connective Tissue Alterations in the Skin of Ultraviolet Irradiated Hairless Mice

Connective tissue alterations were induced in hairless mouse skin by ultraviolet (UV) irradiation. Hairless mice were irradiated three times a week for 10 weeks with sunlamps (UVA and UVB) and the skin was examined using immunochemical and biochemical techniques. Indirect immunofluorescence was performed with antibodies directed against elastin, microfibrillar proteins, and fibronectin. Increased fluorescence was observed in the actinically damaged skin for elastin, microfibrillar proteins, and fibronectin. The elastic fiber components, elastin and microfibrillar proteins, were then isolated and quantified. Control skin contained approximately 0.1% by dry weight of elastic fiber components, whereas actinically damaged skin contained 0.2% by dry. weight. These data are consistent with previous observations of elastic fiber hyperplasia in UV irradiated mice. In addition, irradiated mouse skin contained 1.12 mg of extracted fibronectin per gram wet weight as compared with 0.59 mg in control skin. Irradiated mouse skin contained increased quantities of hyaluronic acid and chondroitin sulfate (uronic acid content). These studies further support the validity of the UV irradiated hairless mouse as a model of human dermal photoaging