Recent increasing restrictions on animals have persuaded researchers to seek in vitro alternatives that could reduce the use of experimental animals and provide a unique methodology for the exploration of specific toxicant mechanisms in testes. Although various in vitro models have been reported, their application in toxicological studies has been limited due to various reasons. In the present study, an improved three-dimensional rat testicular cell co-culture model was established by the addition of KSR to the culture medium instead of FBS.The effects of KSR and FBS were assessed and followed by an assessment of the effects of BPA on somatic cell function and germ cell differentiation in vitro using this improved co-culture model. It was found that the addition of KSR could enhance cell proliferation and germ cell meiosis, which confirmed the functional integrity of the co-culture model. Finally, the effects of BPA on the in vitro model demonstrated that the model could successfully mimic in vivo testis physiology phenomenon. We concluded that the modified model could be used to evaluate various chemicals on rat testis cells and investigate the specific mechanisms of toxicant activity in the testis in future studies.

Our recent studies suggest that H2 (hydrogen) has a potential as a novel radioprotector without known toxic side effects. The present study was designed to examine the underlying radioprotective mechanism of H2 and its protective role on irradiated germ cells. Produced by the Fenton reaction and radiolysis of H2O, hydroxyl radicals (•OH) were identified as the free radical species that were reduced by H2. We used a H2 microelectrode to dynamically detect H2 concentration in vivo, and found H2 significantly reduced in situ fluorescence intensity of hydroxyphenyl fluorescein; however, as we treated the mice with H2 after irradiation, the decrease is not significant. We found that pre-treatment of H2 to IR (ionizing radiation) significantly suppressed the reaction of •OH and the cellular macromolecules which caused lipid peroxidation, protein carbonyl and oxidatively damaged DNA. The radioprotective effect of H2 on male germ cells was supported by ameliorated apoptotic findings examined by morphological changes and TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) in testicular tissue, and by preserved viability of stem spermatogonia examined for testicular histological parameters, daily sperm production and sperm quality; we used WR-2721 [S-2-(3-aminopropylamino)ethyl phosphorothioic acid] as a reference compound. Our results represent the first in vivo evidence in support of a radioprotective role of H2 by neutralizing •OH in irradiated tissue with no side effects.