Generation of rat offspring using spermatids produced through in vitro spermatogenesis

An in vitro spermatogenesis method using mouse testicular tissue to produce fertile sperm was established more than a decade ago. Although this culture method has generally not been effective in other animal species, we recently succeeded in improving the culture condition to induce spermatogenesis of rats up to the round spermatid stage. In the present study, we introduced acrosin-EGFP transgenic rats in order to clearly monitor the production of haploid cells during spermatogenesis in vitro. In addition, a metabolomic analysis of the culture media during cultivation revealed the metabolic dynamics of the testis tissue. By modifying the culture media based on these results, we were able to induce rat spermatogenesis repeatedly up to haploid cell production, including the formation of elongating spermatids, which was confirmed histologically and immunohistochemically. Finally, we performed a microinsemination experiment with in vitro produced spermatids, which resulted in the production of healthy and fertile offspring. This is the first demonstration of the in vitro production of functional haploid cells that yielded offspring in animals other than mice. These results are expected to provide a basis for the development of an in vitro spermatogenesis system applicable to many other mammals.

Automated summary

More than a decade ago, a method using mouse testicular tissue to produce fertile sperm in vitro was established. Although this method has not been effective in other animal species, we recently improved the culture condition to induce spermatogenesis of rats. By introducing acrosin-EGFP transgenic rats and analyzing the metabolomics of the culture media, we successfully induced rat spermatogenesis up to haploid cell production, leading to the production of healthy and fertile offspring through microinsemination. This is the first demonstration of functional haploid cell production and offspring generation in animals other than mice, contributing to the development of an in vitro spermatogenesis system applicable to various mammals.