Rock Inhibitor Y-27632 Partially Shields Mouse Testes from Chemotherapy Damage

A single experimental drug has partially protected the sperm-producing machinery of young mice from the damaging effects of a common chemotherapy agent, according to an original research article published in Reproductive Sciences. The study tested Y-27632, a small-molecule inhibitor of Rho-associated coiled-coil–containing protein kinase (ROCK), against busulfan-induced testicular injury and reported measurable gains in the structural hallmarks of spermatogenesis, even though it could not restore sperm output to normal levels.

The motivation behind the work is a growing clinical problem. Advances in cancer therapy have markedly improved patient survival, increasing the need for effective fertility preservation strategies. Chemotherapeutic agents commonly induce apoptosis in rapidly proliferating cells, including spermatogonia—the stem cells that continually replenish sperm production—resulting in long-term testicular damage.

Y-27632 acts on a specific signaling pathway. It blocks ROCK enzymes, and the compound has previously been shown to suppress apoptosis in various stem cell populations by modulating Rho GTPase–dependent signaling. The researchers asked whether that anti-apoptotic effect could translate into protection of the seminiferous tubules, the structures within the testes where sperm are manufactured.

To find out, the team studied eighteen four-week-old male C57BL/6 mice, randomly assigned to three groups: an untreated control group, a group receiving busulfan at 40 milligrams per kilogram, and a combined group receiving busulfan plus Y-27632 at 5 milligrams per kilogram. Seventy days after treatment, the researchers measured sperm parameters including count, motility, viability and plasma membrane integrity, alongside testicular outcomes such as seminiferous tubule diameter, germinal epithelium thickness, the tubular differentiation index, the spermatogenesis index, the Johnsen score, apoptotic gene expression, malondialdehyde levels, total antioxidant capacity and TUNEL-positive cells.

The histological results were the clearest success. Compared with mice given busulfan alone, those that also received Y-27632 had significantly wider seminiferous tubules and thicker germinal epithelium, the layered tissue that houses the developing germ cells. The treated animals also scored higher on the tubular differentiation index, the spermatogenesis index and the Johnsen score, a standard pathological grading system for testicular tissue.

Molecular readouts moved in the same direction. Y-27632 treatment was associated with reduced ERK gene expression and fewer TUNEL-positive cells, a laboratory marker used to identify cells undergoing apoptosis. The busulfan-plus-Y-27632 group therefore showed both better preserved architecture and fewer dead cells than the busulfan-only group.

The protection, however, was incomplete. Sperm parameters—count, motility, viability and plasma membrane integrity—along with testicular weight remained significantly below control values despite Y-27632 treatment. The drug also showed no significant effect on several other measures: malondialdehyde levels, total antioxidant capacity and sperm DNA integrity did not differ significantly among the three groups.

The authors conclude that Y-27632 partially attenuated busulfan-induced testicular damage by improving histological indices of spermatogenesis and reducing apoptosis, and they suggest that ROCK inhibition may represent a potential adjunct strategy for fertility preservation following gonadotoxic cancer therapies. The caveat is important: these are findings from a mouse model using a defined busulfan protocol, not from human trials, and partial structural protection did not translate into normalized sperm quality or testicular weight. Whether ROCK inhibition could help preserve fertility in patients treated with gonadotoxic therapies would need to be established in further studies.

Subject of Research: Protective effect of the ROCK inhibitor Y-27632 against busulfan-induced testicular injury in a mouse model of azoospermia

Article Title: Effect of Rho Kinase Inhibitor (Y27632) on Spermatogenesis in Azoospermic Mice Model

Article References: Bolboleh, S., Peirouvi, T., Karimipour, S., Abedpour, N., & Topraggaleh, T. R. (2026). Effect of Rho Kinase Inhibitor (Y27632) on Spermatogenesis in Azoospermic Mice Model. Reproductive Sciences. https://doi.org/10.1007/s43032-026-02244-y

Image Credits: AI Generated

DOI: 10.1007/s43032-026-02244-y

Keywords: ROCK inhibitor, Y-27632, spermatogenesis, busulfan, azoospermia, fertility preservation, apoptosis, seminiferous tubules, mouse model, chemotherapy, testicular injury, ERK