Transforming growth factor β1 has a critical role in the regulation of testicular function. Transgenic male mice over expressing α and β subunits of hCG (hCG+) are infertile and testicular steroidogenesis is enhanced showing high levels of testosterone and progesterone (P4). The chronic hCG hyperstimulation leads to Leydig cell (LC) hypertrophy/hyperplasia in prepubertal mice.
Aims: To analyze: i) the expression of the TGF-β1 system in LC from WT and hCG+ mice of 21-days old by immunohistochemistry and by RT-PCR; ii) the in vitro effect of hCG, P4 and T on the TGF-β1 system in purified LC from WT mice by RT-PCR; iii) the in vitro effect of TGF-β1 on proliferation markers in purified LC from WT animals and iv) the in vivo effect of TGF-β1 on testicular morphometry in WT mice. TGF-β1, ALK-5 and ALK-1 were immunolocalized in WT and hCG+ LC. The expression of TGF-β1 and endoglin (EDG) was significantly higher in hCG+ LC respect to control (P<0.05). hCG (10 IU/ml) stimulated the expression of TGF-β1 while P4 (10−6 M) increased the expression of EDG, and this effect was blocked by RU486 (antiprogestin) (P<0.05). T (10−6 M) failed to modify TGF-β1 system expression. The action of TGF-β1 (1 ng/ml) in the presence of P4 caused: i) the phosporylation of Smad1/5 detected by western blot, ii) an increase in PCNA expression levels detected by immunocytochemestry and iii) a decrease in the Bax/Bcl2 ratio analyzed by RT-PCR (P<0.05). Morphometric studies revealed that the intratesticular injection of TGF-β1 and P4 (s.c.) augmented the LC volume (V) due to an increase in the cytoplasmic V (control 341.49±43.86 vs TGF-β1+P4 511.16±30.83, P<0.05) and a decrease of the nuclear V (control 144.28±17.74 vs TGF-β1+P4 125.02±4.89, P<0.05). These results prompt us to speculate that the TGF-β1-EDG-ALK-1-Smad1/5 signalling pathway could be involved in the LC hypertrophy/hyperplasia.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology