Stem cell research provides promising strategies in improving healthcare for human beings. As a noninvasively obtained and easy-to-culture cell resource with relatively low expense, urine-derived stem cells have special advantages. They have been extensively studied on its proliferation ability and differentiation potential and were being reprogrammed to model diseases during the last decade. In this review, we intend to summarize the latest progress on the research of urine-derived stem cells for its broad application mainly in regenerative medicine and disease modeling, as well as in what is challenging currently. This minireview will highlight the potential application of urine-derived stem cells and provides possible direction of further research in the future.

Gold nanorods (GNRs) are commonly used nanomaterials with potential harmful effects on male reproduction. However, the mechanism by which GNRs affect male reproduction remains largely undetermined. In this study, the metabolic changes in spermatocyte-derived cells GC-2 and Sertoli cell line TM-4 were analyzed after GNR treatment for 24 h. Metabolomic analysis revealed that glycine was highly decreased in TM-4 cells after GNR-10 nM treatment while there was no significant change in GC-2 cells. RT-PCR showed that the mRNA levels of glycine synthases in the mitochondrial pathway decreased after GNR treatment, while there was no significant difference in mRNA levels of glycine synthases in the cytoplasmic pathway. High content screening (HCS) showed that GNRs decreased membrane permeability and mitochondrial membrane potential of TM-4 cells, which was also confirmed by JC-1 staining. In addition, RT-PCR and Western blot indicated that the mRNA and protein levels of blood-testis barrier (BTB) factors (ZO-1, occludin, claudin-5, and connexin-43) in TM-4 cells were also disrupted by GNRs. After glycine was added into the medium, the GNR-induced harmful effects on mitochondria and BTB factors were recovered in TM-4 cells. Our results showed that even low doses of GNRs could induce significant toxic effects on mitochondria and BTB factors in TM-4 cells. Furthermore, we revealed that glycine was a potentially important metabolic intermediary for the changes of membrane permeability, mitochondrial membrane potential and BTB factors after GNR treatment in TM-4 cells.

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Thirdhand smoke (THS) is a new term for the toxins in cigarette smoke that linger in the environment long after the cigarettes are extinguished. The effects of THS exposure on male reproduction have not yet been studied. In this study, metabolic changes in male germ cell lines (GC-2 and TM-4) were analyzed after THS treatment for 24 h. THS-loaded chromatography paper samples were generated in a laboratory chamber system and extracted in DMEM. At a paper: DMEM ratio of 50 μg/ml, cell viability in both cell lines was normal, as measured by the MTT assay and markers of cytotoxicity, cell cycle, apoptosis and ROS production were normal as measured by quantitative immunofluorescence. Metabolomic analysis was performed on methanol extracts of GC-2 and TM-4 cells. Glutathione metabolism in GC-2 cells, and nucleic acid and ammonia metabolism in TM-4 cells, was changed significantly by THS treatment. RT-PCR analyses of mRNA for enzyme genes Gss and Ggt in GC-2 cells, and TK, SMS and Glna in TM-4 cells reinforced these findings, showing changes in the levels of enzymes involved in the relevant pathways. In conclusion, exposure to THS at very low concentrations caused distinct metabolic changes in two different types of male reproductive cell lines.