Increased sFRP3 expression correlated to senescence of endothelial cells in the aging process of mice.

Aging is tightly associated with various diseases, such as cardiovascular diseases; however, there is no effective biomarker to detect and evaluate the aging process in vivo. Therefore, it is critical to identify new aging biomarkers for earlier diagnose of aging-related diseases. This study investigated the profile of cytokines in serum samples of young and aged mice with the purpose of exploring new biomarkers that have remarkable alterations in aging. A solid-phase antibody array was used to screen 200 proteins in the mouse serum, among which 32 cytokines differentially expressed between young and aged mice were screened. The major proteins were secreted frizzled-related protein 3 (sFRP3), Fractalkine, IGFBP-5, IGFBP-6, etc. We select secreted frizzled-related protein 3 (sFRP3) in follow-up study. Then, enzyme-linked immunosorbent assay (ELISA) was used to detect the expression levels of sFRP3. Our results revealed that the expression levels of sFRP3 in serum samples from aged mice were significantly higher than those in samples from young mice. ELISA data were identical to those obtained by the antibody array. Our findings indicated that sFRP3 has remarkable significance in senescence. Furthermore, we detected sFRP3 level in culture supernatants of primary endothelial cells, and the variation trend of sFRP3 levels in culture supernatant was consistent with serum data. We also detected serum sFRP3 amounts in healthy young and elderly individuals. Interestingly, serum sFRP3 amounts in the elderly were significantly increased compared with those of young individuals.