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In vitro spermatogenesis (IVS) has important applications including fertility preservation of prepubertal cancer patients; however, thus far, IVS has only been achieved using mouse models. To study the effects of growth factors on the maintenance of testicular tissue integrity, germ cell numbers, and potential induction of IVS using a porcine model, we cultured small testicular fragments (~2 mg) from 1-wk-old piglets under six different media conditions (DMEM + 10%KSR alone or supplemented with GDNF, bFGF, SCF, EGF, or a combination of all) for 8 weeks. Overall, tissues supplemented with GDNF and bFGF had the greatest seminiferous tubule integrity and least number of apoptotic cells. GDNF-supplemented tissues had the greatest number of gonocytes per tubule, followed by bFGF-supplemented tissues. There was evidence of gradual Sertoli cell maturation in all groups. Moreover, histological examination and the expression of c-KIT (a marker of differentiating spermatogonia and spermatocytes) and STRA8 (a marker of the pre/meiotic stage germ cells) confirmed the induction of IVS in all groups. However, GDNF- and bFGF-supplemented tissue cultures had greater numbers of seminiferous tubules with spermatocytes compared to other groups. In conclusion, overall, GDNF and bFGF supplementation better maintained the tissue integrity and gonocyte numbers and induced IVS in cultured testicular tissues. [ABSTRACT FROM AUTHOR]

Simple Summary: One out of every 650 children is affected by cancer, and about half of survivors become permanently infertile due to the side effects of cancer treatments. Pre-treatment testicular biopsies can be collected and cryopreserved for future use to uphold biological fatherhood. Currently, the only safe approach to produce haploid germ cells is through in vitro spermatogenesis (IVS), which has only been fully achieved in mice. Pigs are a more suitable animal model for the study of testicular development and IVS, not only because of their anatomical and physiological similarities to humans but also their long prepubertal period. This study explored optimal conditions for the long-term culture of neonatal porcine testicular tissues as a first step in achieving IVS from pigs, as a model. In this study, we investigated the effects of testicular tissue size, tissue preparation method, and serum source in media on long-term culture of neonatal porcine testicular tissues. We showed that small intact testicular tissue fragments (~2 mg) cultured in knockout serum replacement could be effectively maintained in vitro for up to 4 weeks of culture. Moreover, the presence of viable germ cells after 4 weeks of culture indicates that this approach may be applicable for IVS in pigs. Long-term culture of testicular tissue has important applications, including the preservation of fertility potential of prepubertal boys undergoing gonadotoxic cancer treatment. This study was designed to define optimal conditions for the long-term culture of neonatal porcine testicular tissue as an animal model for preadolescent individuals. Testes from 1 wk old donor piglets were used to examine the effects of tissue fragment size (~2, 4, 6, or 8 mg), preparation method (intact, semi-digested, or physically dispersed fragments), and serum source in the media (fetal bovine serum—FBS—or knockout serum replacement—KSR). Testicular fragments were examined weekly for 4 weeks for tissue integrity, seminiferous cord density and morphology, and gonocyte counts. Testicular tissue integrity was dependent on fragment size and preparation method, where the smallest size (2 mg, p < 0.05) and intact preparation method were advantageous (p < 0.05). Seminiferous cord density decreased over the culture period (p < 0.05). Although the relative number of gonocytes decreased over time for all sizes and methods (p < 0.01), smaller intact fragments (2 and 4 mg) had greater numbers of gonocytes (p < 0.05). Our findings suggest that intact or physically dispersed testicular fragments of the smallest size (2 mg) cultured in KSR-supplemented media could be effectively maintained in vitro for the duration of 4 weeks. [ABSTRACT FROM AUTHOR]

Gonocytes are germline stem cells in the neonatal testis with important potential applications in fertility restoration and transgenesis. Using stepwise experiments, we examined the effects of different media combined with fetal bovine serum (FBS) and/or knockout serum replacement (KSR) on the in vitro proliferation, colony-formation, ultrastructure, and expression of pluripotency markers of porcine gonocytes. Testis cells from 1-wk-old piglets were cultured for 28 days in 6 different culture media (DMEM, DMEM/F12, GMEM, α-MEM, StemPro, and RPMI), each supplemented with 5%, 10%, or 15% FBS and/or 5%, 10%, or 15% KSR. The media and FBS/KSR combination leading to the maximum number of gonocytes, and their colonies were selected for further analyses. KSR supplementation resulted in a reduced somatic cell propagation and increased gonocyte colony formation (P < 0.001). Culturing in DMEM+15%FBS led to the greatest number of gonocytes (P < 0.001), while the largest diameter and greatest number of colonies were formed in DMEM+5%FBS+10%KSR cultures (P < 0.001). Gonocytes and their colonies in DMEM+15%FBS expressed all the examined gonocyte and pluripotency markers. KSR alone did not support gonocyte propagation, likely due to a reduced somatic cell proliferation; however, the combination of FBS and KSR increased gonocyte colony formation and their size. • Optimized culture of germline stem cells has important potential applications for fertility restoration and transgenesis. • Tested the effects of six different media combined with various concentrations of FBS or KSR on proliferation of gonocytes, their colonies, and their pluripotency. • Gonocytes and their colonies in DMEM+15%FBS expressed all the examined gonocyte and pluripotency markers. • KSR alone did not support gonocyte propagation, but the combination of FBS and KSR increased gonocyte colony formation and their size. [ABSTRACT FROM AUTHOR]