Expression and Action of Transforming Growth Factor Beta (TGFβ1, TGFβ2, and TGFβ3) during Embryonic Rat Testis Development1

Andrea S. Cupp; Grace Kim; Michael K. Skinner

doi:10.1095/biolreprod60.6.1304

The objective of the current study was to determine the role of transforming growth factor beta (TGF) during seminiferous cord formation and embryonic testis development. The expression pattern of mRNA for TGF isoforms was evaluated during testis development through a quantitative reverse transcription-polymerase chain reaction (QRT-PCR) procedure. Expression of mRNA for TGF1 was highest at postnatal day 0 (P0) and P10. In contrast, TGF2 was high at embryonic day 15 (E15), declined at E16, and showed a transient increase at P0 through P3 of testis development. Interestingly, expression of mRNA for TGF3 was high during embryonic development and then declined after P3. Immunohistochemical localization of TGF1 and TGF2 demonstrated expression in Sertoli cells at E14 and in the seminiferous cords at P0. Selective interstitial cells expressed high concentrations of TGF1 and TGF2 in P0 testis. TGF3 was expressed in selective cells at the junction of the E14 testis and mesonephros. The cells expressing TGF3 in the testis appeared to be preperitubular cells that resided around the seminiferous cords. TGF3 was localized to gonocytes in P0 testis. TGF1 was found to have no influence on seminiferous cord formation in embryonic organ cultures of E13 testis. In contrast, growth of both E13 and E14 embryonic organ cultures was inhibited by TGF1 and resulted in reduced testis size (40% of controls) with fewer cords present. A P0 testis cell culture and thymidine incorporation assay were used to directly examine the effects of recombinant TGF1. TGF1 alone had no influence on thymidine incorporation in P0 testis cell cultures when compared to controls. Interestingly, TGF1 inhibited epi-dermal growth factor (EGF), and 10% calf serum stimulated P0 testis cell growth but not FSH-stimulated growth. Therefore, TGF1 appears to inhibit testis growth in both the embryonic and early postnatal periods. The hormonal regulation of TGF expression was measured using P0 testis cell cultures and a QRT-PCR procedure for each TGF isoform. High concentrations of EGF stimulated expression of mRNA for TGF1 after 24 h but suppressed expression of TGF3. In contrast, there was no effect of FSH on TGF isoform expression. In summary, TGF regulates embryonic and P0 testis growth through inhibiting the actions of positive growth factors such as EGF. In addition, EGF but not FSH appears to regulate TGF isoform expression. Combined observations from the present study demonstrate that TGF iso-forms are differentially expressed and appear to be regulators of testis growth during the embryonic and early postnatal periods .

Expression and Action of Transforming Growth Factor Beta (TGFβ1, TGFβ2, and TGFβ3) during Embryonic Rat Testis Development1

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