Expression, action, and regulation of transforming growth factor alpha andepidermal growth factor receptor during embryonic and perinatal rat testisdevelopment

The objective of the current study was to extend previous observations and examine the expression pattern and effects of transforming growth factor al pha (TGF alpha) and epidermal growth factor receptor (EGFR) on embryonic te stis morphogenesis and growth. The expression of TGF alpha was determined a fter morphological sex determination (seminiferous cord formation at embryo nic day 13 [ED13]) through perinatal testis development (postnatal day 5 [P D5]) with a quantitative reverse transcription-polymerase chain reaction pr ocedure. Expression of messenger RNA (mRNA) for TGF alpha appeared to be mo re dynamic during testis development when compared with the expression of m RNA for EGFR. Message for TGF alpha was reduced at ED16 and PD4, and was el evated at PD0 during testis development. In contrast, EGFR mRNA levels were negligible at ED15 and were elevated constitutively from ED16 through PD5. Immunohistochemistry was conducted at ED14, ED16, ED19, PD0, PD3, and PD5 to localize cellular expression of both TGFa and EGFR. At ED16, positive st aining for EGFR was localized to the cords, and by ED19, was mainly in the cords with slight expression in the interstitium. From PD0 to PD5, positive staining for EGFR was detected in the germ, Sertoli, and interstitial cell s. Immunohistochemistry for TGF alpha detected localization at ED14 and ED1 6 to the Sertoli cells and to specific cells in the interstitium. From ED19 through PD5, TGF alpha was detected in the Sertoli, germ, and interstitial cells, and in endothelial cells within the interstitium. To determine the effects of TGF alpha on embryonic testis growth and seminiferous cord forma tion, ED13 testis organ cultures were treated with sense and antisense TGF alpha oligonucleotides. Antisense TGF alpha inhibited testis growth by 25%- 30% in ED13 testis organ cultures when compared with sense oligonucleotide control pairs. To examine the effects of TGF alpha on perinatal testis grow th, PD0 testis cultures were treated with different doses of TGF alpha. TGF alpha increased thymidine incorporation into DNA in PD0 testis cultures. T herefore, TGF alpha appears to have actions on both embryonic and perinatal testis growth. The regulation of TGF alpha and EGFR mRNA levels were exami ned using PD0 testis cultures treated with hormones that stimulate testis g rowth. Follicle-stimulating hormone (FSH) stimulated (P < .05) and testoste rone tended to stimulate (P < .07) mRNA expression of EGFR. Epidermal growt h factor stimulation of PD0 testis cultures did not affect levels of mRNA e xpression for EGFR, but did suppress expression of mRNA for TGF alpha. Thes e results taken together demonstrate that TGF alpha can act to regulate ear ly embryonic and perinatal testis growth. Furthermore, TGF alpha and EGFR e xpression can be regulated through growth stimulatory hormones such as FSH and testosterone.