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Fibulin-5 is believed to play an important role in the elastic fiber formation. The present experiments were carried out to characterize the molecular interaction between fibulin-5 and tropoelastin. Our data showed that the divalent cations of Ca(2+), Ba(2+) and Mg(2+) significantly enhanced the binding of fibulin-5 to tropoelastin. In addition, N-linked glycosylation of fibulin-5 does not require for the binding to tropoelastin. To address the fibulin-5 binding site on tropoelastin constructs containing, exons 2-15 and exons 16-36, of tropoelastin were used. Fibulin-5 binding was significantly reduced to either fragment and also to a mixture of the two fragments. These results suggested that the whole molecule of tropoelastin was required for the interaction with fibulin-5. In co-immunoprecipitation experiments, tropoelastin binding to fibulin-5 was enhanced by an increase of temperature and sodium chloride concentration, conditions that enhance the coacervation of tropoelastin. The binding of tropoelastin fragments to fibulin-5 was directly proportional to their propensity to coacervate. Furthermore, the addition of fibulin-5 to tropoelastin facilitated coacervation. Taken together, the present study shows that fibulin-5 enhances elastic fiber formation in part by improving the self-association properties of tropoelastin.

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Chronically, sun-exposed human skin is characterized by dermal connective tissue damage with the accumulation of abnormal elastic fibers. However, little is known about the relationship between accumulation of abnormal elastic fibers and photodamaged skin. In the present study, we investigated the involvement of reactive oxygen species (ROS) in photoaged skin including abnormal accumulation of tropoelastin (TE) induced by ultraviolet A (UVA)-irradiation using an in vitro model of elastic fiber formation. Our data showed that the morphological appearances of TE deposition was observed following the addition of recombinant TE immediately after treatment with UVA-irradiation by immunofluorescence staining and semi-quantitative assay. Our data also revealed that treatment with hypoxanthine-xanthine oxidase, which generates superoxide radicals, stimulated TE deposition. Furthermore, we confirmed that abnormal TE deposition induced by UVA-irradiation was inhibited by treatment with Cu/Zn superoxide dismutase, a superoxide radical scavenger. Therefore, the data obtained suggest that superoxide radical is a candidate for inducing morphological changes and increasing TE deposition induced by UVA-irradiation in human skin fibroblast cells. The present study would be helpful for developing a prophylactic agent for photoaged skin.

Chronic ulcerations are caused by pressure, ischemia or attrition and is a serious problem for long term care. However, little is known about biomolecular markers expressed during the development of pressure ulcerations. In the present study, we examined whether various extracellular matrix components correlate with the development of pressure ulcerations. Examination of wound areas and immunohistological staining