In Vitro Oogenesis
Creating Oocytes In Vitro


Germ cells differentiate into spermatozoa or oocytes, and these cells in turn fuse to generate new individuals, thereby transmitting genetic information across successive generations.

The founding scientists of Houjou have been leading the quest for in vitro gametogenesis (IVG), the process of creating spermatozoa or oocytes from germ cells induced from pluripotent stem cells (PSCs) [embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs)] in vitro. The scientists have demonstrated the proof-of-principle for IVG in mice and have been working to extend IVG to humans and other mammals.

Spermatozoa—and even more particularly oocytes, which are few in number and difficult to collect/preserve—are critical biological resources that determine the development and evolution of given species, and ensure their continued existence.

Accordingly, in developed countries, fertility treatments and other assisted reproductive technologies (ART) have been eagerly pursued, and the ratio of births involving ART has been steadily increasing (1 in 15 new births involved ART in Japan in 2019). Moreover, recent investigations have shown that epigenetic properties of fertilized eggs are key to the embryonic development and disease sensitivities of offspring. Thus, the fundamental roles of germ cells in health and disease are also being increasingly recognized in the field of medicine.

Houjou develops and validates methodologies for inducing germ cells, particularly oocytes from the PSCs of humans, rare/important non-human primates, and representative mammals, thereby creating a foundation for realizing the significant potential of IVG in future societies.

founding scientists
Mitinori Saitou M.D.,Ph.D
Katsuhiko Hayashi Ph.D


  • 2020.01.06



Trade NameHoujou, Inc.
EstablishedJan 6, 2020
Head Office103-5, Tanaka-Monzen-cho, Sakyo-ku, Kyoto 606-8225 JAPAN
President & CEOMasakazu Kobayashi
Executive DirectorMitinori Saitou Katsuhiko Hayashi
AuditorShusei Kamata
Our businessHoujou would like to address global key issues, including infertility, species conservation, food supply, and so on, through the generation of mature oocytes from human and other species stem cells.

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