Expression and action of transforming growth factor beta (TGF beta 1, TGF beta 2, and TCF beta 3) during embryonic rat testis development

The objective of the current study was to determine the role of transformin g growth factor beta (TGF beta) during seminiferous cord formation and embr yonic testis development. The expression pattern of mRNA for TGF beta isofo rms was evaluated during testis development through a quantitative reverse transcription-polymerase chain reaction (QRT-PCR) procedure. Expression of mRNA for TGF beta 1 was highest at postnatal day 0 (P0) and P10. In contras t, TGF beta 2 was high at embryonic day 15 (E15), declined at E16, and show ed a transient increase at PO through P3 of testis development Interestingl y, expression of mRNA for TGF beta 3 was high during embryonic development and then declined after P3. Immunohistochemical localization of TGF beta 1 and TGF beta 2 demonstrated expression in Sertoli cells at E14 and in the s eminiferous cords at PO. Selective interstitial cells expressed high concen trations of TGF beta 1 and TGF beta 2 in PO testis. TGF beta 3 was expresse d in selective cells at the junction of the E14 testis and mesonephros. The cells expressing TGF beta 3 in the testis appeared to be preperitubular ce lls that resided around the seminiferous cords. TGF beta 3 was localized to gonocytes in PO testis. TGF beta 1 was found to have no influence on semin iferous cord formation in embryonic organ cultures of E13 testis. In contra st, growth of both E13 and E14 embryonic organ cultures was inhibited by TG F beta 1 and resulted in reduced testis size (40% of controls) with fewer c ords present. A PO testis cell culture and thymidine incorporation assay we re used to directly examine the effects of recombinant TGF beta 1. TGF beta 1 alone had no influence on thymidine incorporation in PO testis cell cult ures when compared to controls. interestingly, TGFP1 inhibited epidermal gr owth factor (EGF), and 10% calf serum stimulated PO testis fell growth but not FSH-stimulated growth. Therefore, TGF beta 1 appears to inhibit testis growth in both the embryonic and early postnatal periods. The hormonal regu lation of TGF beta expression was measured using PO testis cell cultures an d a QRT-PCR procedure for each TGF beta isoform. High concentrations of EGF stimulated expression of mRNA for TGFP1 after 24 h but suppressed expressi on of TGFP beta 3. In contrast, there was no effect of FSH on TCF beta isof orm expression. In summary, TGF beta regulates embryonic and PO testis grow th through inhibiting the actions of positive growth factors such as EGF. I n addition, EGF but not FSH appears to regulate TGF beta isoform expression . Combined observations from the present study demonstrate that TGF beta is oforms are differentially expressed and appear to be regulators of testis g rowth during the embryonic and early postnatal periods.