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Germ cell production from stem cells allows for studying the mechanisms involved in gamete development with the aim of helping infertile couples with the generation of healthy gametes. In this context, improving the protocols for in-vitro germ cell induction from stem cells is very important. Recently, SB4 small molecule has been introduced as a potent agonist for bone morphogenic protein 4 (BMP4). Herein, we investigated whether BMP4, is replaceable by SB4 for having affordable protocol for in vitro germ cell differentiation. We demonstrated that SB4 can induce Blimp1 (as the first gene induced germ line differentiation) expression significantly but at a lower level compared to BMP4. However, Tfap2c (a putative downstream target of Blimp1 during germ cell differentiation) expression level in SB4-induced aggregates was significantly higher than in BMP4-induced aggregates. Moreover, co-presence of both BMP4 and SB4 could increase the expression level of Prdm14, Nnose3 and Stella (Dppa3), and thereby improve establishment of the germ cell fate during in-vitro differentiation of embryonic stem cells. In summary, our data suggest that SB4 could improve germ line gene expression pattern induced by BMP4 during embryonic stem cells in-vitro differentiation., (Copyright © 2021. Published by Elsevier B.V.)

Demystifying the mechanisms that underlie germline development and gamete production is critical for expanding advanced therapies for infertile couples who cannot benefit from current infertility treatments. However, the low number of germ cells, particularly in the early stages of development, represents a serious challenge in obtaining sufficient materials required for research purposes. In this regard, pluripotent stem cells (PSCs) have provided an opportunity for producing an unlimited source of germ cells in vitro. Achieving this ambition is highly dependent on accurate stem cell niche reconstitution which is achievable through applying advanced cell engineering approaches. Recently, hydrogel microparticles (HMPs), as either microcarriers or microcapsules, have shown promising potential in providing an excellent 3-dimensional (3D) biomimetic microenvironment alongside the systematic bioactive agent delivery. In this review, recent studies of utilizing various HMP-based cell engineering strategies for appropriate niche reconstitution and efficient in vitro differentiation are highlighted with a special focus on the capabilities of droplet-based microfluidic (DBM) technology. We believe that a deep understanding of the current limitations and potentials of the DBM systems in integration with stem cell biology provides a bright future for germ cell research., Supplementary Information: The online version contains supplementary material available at 10.1007/s12551-021-00907-5., Competing Interests: Conflict of interestThe authors declare no competing interests., (© International Union for Pure and Applied Biophysics (IUPAB) and Springer-Verlag GmbH Germany, part of Springer Nature 2021.)

Recently, metal oxide nanoparticles such as zinc oxide nanoparticles (ZnO-NPs) have received considerable attention and humans are exposed to them in everyday life. The increasing use of ZnO-NPs may lead to human health issues. However, little is known about their effects on female reproductive systems, particularly on female germ cells. Germ cells differentiation is a complex biological process that is sensitive to environmental insults and any negative effect on germ cells development may inhibit fertility. Therefore, this study aimed to determine the impact of ZnO-NPs on mouse ovarian germ cells in an in vitro system. The effects of ZnO-NPs on these cells were evaluated using light microscopy, cell proliferation assessment, reactive oxygen species (ROS) level determination, standard cytotoxicity assessment (cell viability assessed by PI staining) and gene expression analysis. Our results demonstrated that ZnO-NPs have cytotoxic effects in a concentration- and time-dependent manner in mouse ovarian germ cells. Exposure of cells to ZnO-NPs concentration-dependently enhanced ROS generation. Furthermore, molecular analysis of ZnO-NPs-treated cells showed a significant increase in expression of premeiotic germ cells markers but a decrease in meiotic and post-meiotic markers compared to un-treated cells. Taken together, our data provides a preliminary insight into possible adverse effects of ZnO-NPs on mouse ovarian germ cells differentiation even at low concentrations., (Copyright © 2020 Elsevier Ltd. All rights reserved.)