Transforming Growth Factor-@ (PI, ,82, and ,63) Gene Expression and Action during Pubertal Development of the Seminiferous Tubule: Potential Role at the Onset of Spermatogenesis

The potential role of transforming growth factor-p (TGFB) as a mediator of cell-cell interactions during the pubertal development of the seminiferous tubule was examined. Mesenchymal-derived peritubular cells and epithelial-like Sertoli cells were isolated from prepubertal, midpubertal, and late pubertal rat testes. The developmental expression of the multiple forms of TGFB (TGFPl, -82, and -83) in whole testis and isolated somatic cell types was determined using a nuclease protection analysis. TGFBI and TGFP2 mRNA expression was predominant in the immature testis and decreased at the onset of puberty. TGFB3 mRNA expression, the most abundant form of TGFP present, peaked at an early pubertal stage, coincident with the initiation of spermatogenesis. Peritubular and Sertoli cells expressed each isoform of TGF/3 during development. Peritubular cell mRNA expression of TGFPl, -82, and $3 decreased during pubertal development upon differentiation of this cell type. Sertoli cell expression of TGFPl increased slightly and plateaued during pubertal development. TGFP2 mRNA expression was evident only in immature prepubertal Sertoli cells. Sertoli cell mRNA expression of TGFB3 increased transiently at the onset of puberty, corresponding with the peak of expression observed during the analysis of whole testicular development. lmmunoblot analysis indicated that both cultured peritubular and Sertoli cells can produce the proteins for TGFPl, -82, and $33. Analysis of the hormonal regulation of TGFP expression revealed that FSH caused a dramatic decrease in Sertoli cell TGFj32 expression while having no effect on TGFPl