Scientists Advance Lab-Grown Human Sperm to Early Development Stage

A research team led by Eoin Whelan and Kotaro Sasaki at the University of Pennsylvania reported that human induced-pluripotent stem (iPS) cells, combined with mouse testicular cells and transplanted into a kidney-capsule pouch of living mice, self-organized into tubular structures resembling testicular tissue. Six months after transplantation the human cells had progressed to spermatogonia, an early sperm precursor found in fetal development. The cells did not advance beyond this stage, and mature sperm have not yet been produced.

Nature

The investigators first reprogrammed human blood-derived iPS cells into cells that mimic early embryonic precursors of eggs and sperm. These immature cells were mixed with non-reproductive cells harvested from mouse testicles, which supply nutrients and structural support. The mixture was placed in a well-vascularized region of a mouse kidney, a site known to sustain transplanted tissue. Within a month the graft formed tubular structures; after six months the human component had differentiated into spermatogonia.

Nature

Whelan emphasized the basic-science focus of the work, noting that the current achievement is far from clinical use. Sasaki highlighted the lag in human reproductive-cell research compared with other species, underscoring the experimental nature of the findings.

Nature

While the technique could eventually illuminate causes of male infertility—about 40 % of cases lack a known origin—it also raises ethical questions. Critics warn that lab-grown gametes might enable genetic modification of embryos, potentially facilitating “designer babies.” The prospect of creating reproductive cells outside the body therefore sparks debate over regulatory oversight and societal impact.

Nature

• “We are approaching this from a basic science perspective,” — Eoin Whelan, reproductive biologist, University of Pennsylvania

Nature

• “We are a long way from clinical application.” — Eoin Whelan

Nature

• “In humans, the work is so behind,” — Kotaro Sasaki, developmental biologist, University of Pennsylvania

Nature