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Abstract Spermatogenesis is one of the most complex processes of cell differentiation and its failure is a major cause of male infertility. Therefore, a proper model that recapitulates spermatogenesis in vitro has been long sought out for basic and clinical research. Testis organ culture using the gas-liquid interphase method has been shown to support spermatogenesis in mice and rats. However, the conventional method using agarose gel has limitations including medium replacement efficiency and live imaging because agarose absorbs medium and is not transparent. To overcome this issue, we developed a new device using microporous membranes and oxygen-permeable materials. Mouse testes sandwiched between a microporous polyethylene terephthalate (PET) membrane on top and an oxygen-permeable 4-polymethyl-1-pentene polymer (PMP) membrane base maintained spermatogenesis over months. The chamber volume was minimized to 0.1% of the culture medium. Weekly time-lapse live imaging enabled us to observe transgenically fluorescent acrosome and nuclear shape formation throughout spermatogenesis. Finally, we obtained healthy fertile offspring from spermatozoa generated in our system. The device could be used not only for basic research to understand spermatogenesis but also for applied research, such as diagnosing and treating male infertility.

In the pharmaceutical industry, primary cultured hepatocytes is a standard tool used to assess hepatic metabolisms and toxicity in vitro. Drawbacks, however, include their functional deterioration upon isolation, mostly due to the lack of a physiological environment. Polydimethylsiloxane (PDMS) has been reported to improve the function of isolated hepatocytes by its high oxygen permeability when used as a material of microphysiological systems (MPS). However, its high chemical sorption property has impeded its practical use in drug development. In this study, we evaluated a new culture material, 4-polymethyl-1-pentene polymer (PMP), in comparison with PDMS and conventional tissue culture polystyrene (TCPS). First, we confirmed the high oxygen permeability and low sorption of PMP, and these properties were comparable with PDMS and TCPS, respectively. Moreover, using primary rat hepatocytes, we demonstrated maintained high levels of liver function at least for 1 week on PMP, with its low chemical sorption and high oxygen permeability being key factors in both revealing the potential of primary cultured hepatocytes and in performing an accurate evaluation of hepatic metabolisms. Taken together, we conclude that PMP is a superior alternative to both PDMS and TCPS, and a promising material for a variety of drug testing systems.