Human in vitro gametogenesis may transform reproductive medicine. Human pluripotent stem cells (hPSCs) have been induced into primordial germ cell–like cells (hPGCLCs); however, further differentiation to a mature germ cell has not been achieved. Here, we show that hPGCLCs differentiate progressively into oogonia-like cells during a long-term in vitro culture (approximately 4 months) in xenogeneic reconstituted ovaries with mouse embryonic ovarian somatic cells. The hPGCLC-derived oogonia display hallmarks of epigenetic reprogramming—genome-wide DNA demethylation, imprint erasure, and extinguishment of aberrant DNA methylation in hPSCs—and acquire an immediate precursory state for meiotic recombination. Furthermore, the inactive X chromosome shows a progressive demethylation and reactivation, albeit partially. These findings establish the germline competence of hPSCs and provide a critical step toward human in vitro gametogenesis.

The in vitro derivation and propagation of spermatogonial stem cells (SSCs) from pluripotent stem cells (PSCs) is a key goal in reproductive science. We show here that when aggregated with embryonic testicular somatic cells (reconstituted testes), primordial germ cell-like cells (PGCLCs) induced from mouse embryonic stem cells differentiate into spermatogonia-like cells in vitro and are expandable as cells that resemble germline stem cells (GSCs), a primary cell line with SSC activity. Remarkably, GSC-like cells (GSCLCs), but not PGCLCs, colonize adult testes and, albeit less effectively than GSCs, contribute to spermatogenesis and fertile offspring. Whole-genome analyses reveal that GSCLCs exhibit aberrant methylation at vulnerable regulatory elements, including those critical for spermatogenesis, which may restrain their spermatogenic potential. Our study establishes a strategy for the in vitro derivation of SSC activity from PSCs, which, we propose, relies on faithful epigenomic regulation.

(Abstracted from Science 2018;362:356–360) Studies have shown that mouse pluripotent stem cells (PSCs) can be induced into primordial germ cell–like cells (hPGCLCs), which, following transplantation under appropriate conditions, can contribute to the development of gametes capable of developing into fertile offspring. Human in vitro gametogenesis from PSCs has long-reaching implications in reproductive medicine but has not yet been achieved.

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Mixed composition metal–halide perovskites were developed to improve the performance of perovskite solar cell devices incorporating tin(iv) oxide substrates for electron transport layers by optimizing the I/Br halide ion ratio.

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With a rapid progress in photovoltaic performance over the past several years, organic–inorganic perovskite solar cells (PSCs) have been regarded as a promising candidate for next-generation photovoltaic devices such as lightweight and flexible photovoltaic equipment and portable systems. However, the photovoltaic performance and its durability during the mechanical bending test of flexible PSCs (fPSCs) are insufficient for the realistic application. This inadequacy stems from a lack of a superior electron transport material (ETM) for fPSCs. Here, we describe the application of SnO2 as an ETM for fPSCs (SnO2-fPSCs), achieving outstanding photovoltaic performance and excellent mechanical bending durability. We demonstrate the high power conversion efficiency (PCE) of 17.1 and 16.2% with negligible hysteresis and the high stabilized power output of 17.0 and 15.9% of normal-architecture SnO2-fPSCs with a photoactive area of 0.1 and 1.0 cm2, respectively. Moreover, the SnO2-fPSCs exhibit an excellent bending durability that retains 76.5% of the initial PCE even after 2000 times harsh bending cycle with a small bending radius of 4.0 mm on 0.1 cm2 active area.

Bending tests and X-ray diffraction studies were conducted on oven-dried wood samples (Picea jezoensis Carr.) treated with various concentrations of aqueous NaOH solution to investigate the influence of alkali treatment on the longitudinal contraction, bending properties, and cellulose structure. The length of the wood samples decreased and the density increased at NaOH concentrations greater than 10%. The Young's modulus and the specific Young's modulus decreased and the strain at yield increased for the same concentration range. However, the stress at yield was almost constant for all concentration ranges. X-ray diffraction analysis showed that lattice transformation from cellulose I to cellulose II did not occur during alkali treatment and the crystallinity index decreased at NaOH concentrations greater than 10%. The crystallinity index was linearly correlated with the changes in longitudinal contraction and the bending properties, which indicates that the increase in the proportion of amorphous components of the cellulose influences the longitudinal contraction and the bending properties of wood samples during alkali treatment.