Good news! Why did men have to wait for so many decades since the contraceptive pill for women came out!
"A proof of principle study in mice, six years in the making, shows how targeting a natural checkpoint in meiosis, the process by which sex cells reproduce, safely stopped sperm production. ...
The researchers made use of JQ1, a small molecule inhibitor that was developed as a research tool to study cancer and inflammatory disease. Because of its neurological side effects, it wasn't a viable therapy for disease, or as a final contraceptive, but it's known to disrupt a stage of meiosis called prophase 1. This enabled Cornell researchers to provide the first proof of principle that meiosis – and sperm production – can be targeted safely and reversibly. ..."
"... In the study, the researchers administered JQ1 in male mice for three weeks. They found that the mice produced no sperm, and that all the molecular parameters of meiosis were disrupted, including chromosomal behavior during prophase 1.
Then they stopped delivering JQ1, and within six weeks, most of the healthy parameters of prophase 1 returned, along with normal sperm production. They then bred those mice and found they were all fertile, and bred the pups to show that they too were fertile, yielding healthy offspring. ..."
From the significance and abstract:
"Significance
Few reversible male contraceptives have advanced toward clinical translation, largely because the optimal biological stage for safe intervention remains undefined.
Meiosis represents a natural checkpoint in sperm production where transient inhibition could achieve precise and reversible fertility control.
Using the small-molecule BRDT inhibitor (+)-JQ1, we demonstrate that brief suppression of meiotic prophase I halts spermatogenesis yet permits complete recovery of germ-cell differentiation, recombination fidelity, and fertility after withdrawal. While acknowledging the need for robust future safety assessments of any candidate drugs, these studies provide a blueprint for developing new contraceptive approaches that act safely and selectively within the germline.
Abstract
Developing safe, reversible, and nonhormonal male contraceptives has been hindered by the lack of defined biological windows that can be transiently interrupted without compromising long-term fertility.
Here, we tested whether meiotic prophase I can serve as such a window by pharmacologically inhibiting the testis-specific chromatin reader BRDT using the small-molecule bromodomain inhibitor (+)-JQ1 as proof-of-principle.
Short-term JQ1 administration (3 wk) selectively disrupted the pachytene transcriptional program, depleted postmeiotic germ cells, and induced a reversible arrest in spermatogenesis.
Upon drug withdrawal, prophase I cytological markers normalized within 6 wk, accompanied by restoration of testis architecture and germ-cell composition. Crossover metrics and transcriptional programs recovered more gradually, reaching full normalization by 30 wk alongside complete restoration of fertility and fecundity.
These results demonstrate that meiotic prophase I can be transiently inhibited to suppress spermatogenesis reversibly without inducing lasting genomic or reproductive defects, defining a stage-specific framework for the rational design of nonhormonal male contraceptives."
Meiotic prophase I disruption as a strategy for nonhormonal male contraception using small-molecule inhibitor JQ1 (open access)
Fig. 1 Three-week JQ1 treatment causes postmeiotic cell loss with full recovery after withdrawal.
Cross‑section of testis tubules showing stages of spermatogenesis: green meiotic cells, pink developing sperm (dots in top right corner) and pink mature sperm (long cells in middle left), and the pre-meiotic white/gray spermatogonia along the basement membrane (lower left) are stem cells the researchers aim to preserve.
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