Human in vitro spermatogenesis from pluripotent stem cells: in need of a stepwise differentiation protocol?

Recently, complete in vitro generation of male gametes starting from pluripotent stem cells was obtained in a mouse model with live offspring as a result. This breakthrough was probably due to the use of a stepwise differentiation protocol taking the tightly regulated in vivo situation into account. As shown previously, factors of the TGFβ superfamily, metabolites of vitamin A, growth hormones, sex steroids and, most importantly, somatic cell...