Researching the effect of mesenchymal stem cells on the testicular microenvironment and the spermatogonial stem cell pool under in vitro conditions

Önen, S. Researching The Effect Of Mesenchymal Stem Cells On The Testicular Microenvironment And The Spermatogonial Stem Cell Pool Under in vitro Conditions. Hacettepe University Institute of Health Sciences, Master of Science Thesis in Stem Cell Programme, Ankara, 2019. Fourty six percent of male patients display infertility due to germ cell damage induced by chemo-radiotherapy for treatment of childhood cancers. It is not possible to collect mature sperm from these patients since spermatogenesis is not present start until puberty. Monolayer long term culture of spermatogonial stem cells is challenging. Mesenchymal stem cells have a similar embryonic origin with the Sertoli cells that have a crucial role in regulation of spermatogenesis. Sertoli cells share gene expression profile and differentiation potential of mesenchymal stem cells. We hypothesized that mesenchymal stem cells can support the testicular niche and maintain the stem cell pool in an in vitro co-culture system by supporting Sertoli cells. The aim of this study is to protect stem cell viability of newborn C57BL/6 mice testes for 1, 2, 4 and 6 weeks by using an syngenic bone marrow derived mesenchymal stem cell supported indirect air liquid interphase co-culture system. The co-culture system has been set and maintained successfully using isolated mesenchymal stem cells of passage 3. The efficiency of mesenchymal stem cell contributed co-culture system was evaluated by histochemical, immunohistochemical and flow cytometric analyses. Mesenchymal stem cells increased seminiferous tubule area at week 1 to 6 and the luminal area at week 2 and 6 when compared to controls (p<0.05). The number of SALL4 labeled spermatogonial stem cells increased at week 1 to 6; PLZF labeled cells increased at week 1 and 2; and c-Kit labeled spermatogenic cells increased at week 6 (p<0.05) with mesenchymal support. In conclusion, this novel mesenchymal stem cell contributed air liquid interphase co-culture system presents a new tool for the in vitro maintenance of testis strips prior to gonadotoxic cancer treatment by providing moderate growth and development of testicular tubules. Keywords: Testis, organ culture, coculture, mesenchymal stem cell, spermatogonial stem cell