Event: Japanese

In a world first, a Japanese team of researchers has developed miniaturized testicular tissues known as testicular organoids from mouse embryonic stem (ES) cells in an experimental vessel. The achievement by the team — comprising University of Osaka professor Katsuhiko Hayashi and associate professor Takashi Yoshino, as well as Yokohama City University professor Takehiko Ogawa and other researchers — was published in U.S. journal Science on Thursday. In 2021, Hayashi and Yoshino created ovarian organoids from mouse ES cells — also the first in the world to do so — when they were at Kyushu University. If testicular organoids are produced from human induced pluripotent stem (iPS) cells in the future, they could help in identifying the causes of male infertility, and the organs created may be used to support testicular functions. However, it is expected to take more than 10 years to develop technology to produce sperm in the human testicular organoids and enable childbirth through in vitro fertilization. Just like iPS cells, which are made by introducing gene clusters into skin and other types of cells, ES cells, created by growing inner cell masses extracted from embryos, can develop into various types of tissues. Ovarian organoids are formed by aggregating gonadal somatic cells and primordial germ cells induced from female ES cells. But simply converting them into male ES cells would lead to the creation of ovarian organoids, not testicular organoids. To address this, the researchers developed a method to create testicular organoids by using three agents to prevent feminization. The team collected spermatogonial stem cells created by the testicular organoids made using the method. The cells were transplanted into the seminiferous tubules of infertile male mice, resulting in the production of normal sperm and the creation of offspring through fertilization with normal eggs.