TOKYO—A top Japanese scientist who co-authored disputed stem-cell papers committed suicide by hanging himself, police said Tuesday.

Yoshiki Sasai, deputy director of the Riken Center for Developmental Biology, guided research published in the journal Nature that purported to show a revolutionary method of creating stem cells by dipping cells in a mild acid solution. The research, published in January, was quickly challenged. Nature retracted the papers in July, saying they contained inaccurate data and other flaws that undermined...