Testicular TGF-β1 system expression and its participation in hypertrophy and hyperplasia of Leydig cells
Candela Rocio Gonzalez1, Betina Gonzalez1, Susana Rulli1, Luiz Renato França2, Guillermi Mattos Jardim Costa2, Ilpo Huhtaniemi3, Ricardo Saul Calandra1 & Silvia Ines Gonzalez-Calvar1,3
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.