The investigation of the role of Desert Hedgehog signalling pathway in abnormal spermatogenesis and in the formation of testicular cancer

Hedgehog (Hh) signalling regulates many aspects of normal development and is upregulated in some cancers. Although the contribution of Hedgehog signalling to cancers is widely accepted, its importance for testis development, spermatogonial stem cells, a unique pluripotent cell type sustained through adulthood, and its roles in spermatogenesis are unknown. Because it is hypothesised that the germ cells which couldn?t mature properly during embriyonic life are associated with testicular cancer in adult life, this thesis aimed to clarify the contribution of Hedgehog signalling in abnormal spermatogenesis and testicular cancer by using in situ hybridisation, immunohistochemistry, tubule drop culture and qRT-PCR techniques..The results of our study showed that during the first wave of spermatogenesis, Hh signaling pathway is active in germ cells, disapearing at birth and reactivating with spermatogenesis in adults. The results from irradiated rat testis model showed that Hh signalling is not only active in embryonic spermatogonial stem cells but also in adult stem cells in the testis. These findings provide the first indication that Hh signalling is active in resting stem cells and are turned off when stem cells mature.When embryonic testis development is disturbed by using DBP exposure and Activin ? -A knock-out models, we observed that the activity of Hh signalling has been changed. This suggests the possible contribution of Hh signalling in abnormal germ cell development.By using a hanging drop culture system on postnatal day 1 mouse seminiferous cords with or without Cyclopamine, (an inhibitor of the Hh signalling pathway), we showed that the genes associated with meiotic divisions such as Stra8 and SCYP3 are upregulated.As well as the expression sites of Hh signalling in murine testis shown in this study, we also understand that Hh signalling is active in testicular cancer patients samples.This thesis provides fresh information regarding Hh signalling which demonstrated that Hh pathway component expression is highly regulated in the testis, indicating that Hh signals function at discrete stages of spermatogenesis. The data presented in this thesis provide a new understanding of how Hh signalling is regulated in vivo and demonstrate its potential contribution to male fertility and infertility. As our understanding of the number of cancers associated with Hh signalling increases, understanding the mechanisms by which Hh signal transduction is regulated is essential for identifying potential target drugs and developing new treatments.Key Words: Desert Hedgehog signalling pathway, spermatogenesis, testicular development, in situ hybridization.