Differential expression of transforming growth factor‐β in the interstitial tissue of testis during aging

AbstractTransforming growth factor‐βs (TGF‐βs) have significant effects on testis development. The pattern of TGF‐β expression in aging testis has not been established to date. We examined age‐related changes in the expression of TGF‐β and its receptors in the testis using Western blot analysis. TGF‐β1 expression increased continuously in aging rat testis, whereas no age‐associated changes were observed for TGF‐β3. Strong expression of TGF‐β2, as well as type I and II receptors was observed in 12‐month‐old testis, but following this time, expression decreased dramatically. Interestingly, TGF‐β2 and ‐β3 displayed strong and similar expression patterns in liver, regardless of age, suggesting that the down‐regulation of TGF‐β2 is testis‐specific. We observed significant induction of p53 and p21WAF1 in 18‐month‐old testis that appeared to correspond with aging. Moreover, caloric restriction (CR) prevented age‐related decrease in TGF‐β2 expression. Using immunohistochemistry, we showed that all TGF‐β1, ‐β2, and ‐β3 proteins are expressed primarily in interstitial cells, which are located in the space between adjoining seminiferous tubules. Our data collectively indicate that aging in the testis is regulated by differential expression of TGF‐β proteins, and decreased levels of TGF‐β2 contribute to the aging process. © 2004 Wiley‐Liss, Inc.