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The regulation of spermatogenesis is based on a complex network of endocrine, paracrine and cellular mediators. The specific process of spermatogenesis is known in detail, but despite intensive research the exact regulation is not known yet. A lot of research teams tried to develop in vitro-systems to cultivate germ cells and therfor contribute towards clarifying the modulatory mechanics. But up to today it is not possible to seed germ cells to elongated spermatids or spermatozoon under in vitro conditions.
In previous studies from our research team as well as other research teams the hypothesis was drawn, that TGF-β and the apoptosis of germ cells, that is induced by TGF-β at the onset of puberty may have an essential role for spermatogenesis. In this study we tried to figure out, if the secretion of TGF-β might be regulated by androgen.
Over a period of 72h we stimulated sertoli cells (SK11), a mixture of sertoli cells and peritubular cells (WL3) and germ cells (GC2) with different concentrations of testosterone. Afterwards we measured the concentration of TGF-β in the medium of these cells via ELISA. Sertoli cells (SK11) secreted just 20% as much TGF-β1 as the mixed culture (WL3) and just 3% as much TGF-β2 as the mixed culture (WL3). The secretion of TGF-β1 and TGF-β2 in sertoli cells (SK11) as well as the mixed culture (WL3) was inhibited by testosterone depending on its concentration. This effect was reversible by stimulation with the antiandrogene flutamid. This shows, that immortilised sertoli cells have a functional AR. Interestingly there was no TGF-β3 secretion detectable in the prepubertal germ cells (GC2) nor in the mixed culture (WL3). Furthermore we could not measure any secretion of TGF-β2 in the germ cells (GC2). For further confirmation of our results we analysed the TGF-β2 secretion and AR expression of testicular cells from microscopic cuts of infertile men via immunohistochemic. Thereby we observed, that the microscopic cuts of men with a disturbed spermatogenesis had a significant stronger colouration of TGF-β2 in testicular cells, than the ones with normal spermatogenesis. However we were not able to show a correlation between AR-Expression and TGF-β2 secretion with this method and so far we did not use another method. In conclusion we were able to show, that TGF-β1 and TGF-β2 are regulated by
androgen. Thus one mechanism of regulation during spermatogenesis is understood and can prove helpful for further studies, that involve the mechanism of spermatogenesis. Moreover it may be one step further regarding the improvement of different therapy options for male infertility.