Spermatogenesis in a cultured testis tissue.
Credit: Takehiko Ogawa / Yokohama National University
CAMBRIDGE: Japanese researchers have successfully produced mature, functional sperm in a laboratory dish for the first time - a feat that has eluded reproductive biologists for more than half a century.
The scientists met this challenge with mice, successfully culturing mouse testes cells, inducing them to cultivate sperm, and then using this sperm to reproduce seemingly normal offspring. Their novel methodology and results may have several clinical applications in humans, particularly in the area of male infertility.
“An in vitro system of mammalian spermatogenesis has never been established in our history,” said Takehiko Ogawa, a reproductive biologist at Yokohama National University in Japan and one of the authors of the Nature paper. “Our paper is the first example of such success and that is exciting.”
The challenge of manufacturing sperm
Since every cell in our body relies on many complex chemical signals to function, our ability to produce mature cells in laboratories is, to some extent, a matter of being able to compensate for these signals by adding or subtracting different factors in the dish – like mixing a biological cocktail.
The signal requirements vary for each organ and cell type, and so biologists attempting to recreate processes like sperm production end up focussing much of their energy on mixing and matching different supplementary products.
Spermatogenesis – the process wherein immature, neonatal germ cells develop into functioning sperm cells – is a long and complex procedure, persisting throughout most of adulthood. Reaching complete maturation itself is a process that usually takes more than a month in most mammals.
Finding the right chemical cocktail
Because sperm development takes so long, scientists haven't been able to produce the precise laboratory conditions that would support the entire process.
In the 1960s, a process called 'organ-culture methods' allowed the immature germ cells to progress to meiosis – the intermediary, cell-division phase in sperm production – but no further.
Now, Ogawa and colleagues believe they have found the right chemical cocktail for sperm production, using their cultured sperm to produce fertile male and female offspring through in vitro fertilisation.
