Summary

Puberty blockers (drugs that pause puberty) are often called a reversible pause, but little is known about their effect on the testicles. Mayo Clinic researchers examined tissue stored from children having surgery to preserve fertility. All 16 born-male patients with gender dysphoria in their tissue bank had taken puberty blockers. Treated children's tissue showed mild to severe shrinking of the sperm-making tubes; one 12-year-old on a blocker plus oestrogen had 59% of tubes completely shrunken. Detailed cell tests on one 14-year-old after more than four years on blockers found sperm-forming cells stuck at an early stage, and computer models judged the tissue to be like a child's before puberty. The authors say this raises 'a potential concern' about full reversibility. It is an early, unchecked signal: few treated patients, mixed drugs, no follow-up after stopping, no fertility measure.

Key findings

• De 87 pacientes de un banco de tejido testicular infantil de la Clínica Mayo, 16 (18 %) tenían disforia de género. Los 16 habían tomado bloqueadores de la pubertad, y 9 (56 %) los estaban tomando en el momento de la cirugía de preservación de la fertilidad.
• Los fármacos contados como 'bloqueadores de la pubertad' incluían bloqueadores propiamente dichos (leuprolida, histrelina, triptorelina) pero también estrógeno y otros fármacos hormonales (medroxiprogesterona, espironolactona), tomados durante 3 a 52 meses. La edad media en la cirugía era de 12,5 años.
• Todos los pacientes con disforia de género eligieron cirugía para extraer tejido en lugar de dar una muestra de esperma, porque no querían o no podían eyacular. 2 de los 9 pacientes tratados tenían anomalías testiculares al ser examinados.
• Al observar unos 50 túbulos por donante en 19 donantes sin cáncer, la densidad de células en los túbulos aumentaba con la edad en los niños sin tratar, pero no mostraba cambios con la edad en los tratados. Un niño de 12 años con un bloqueador más estrógeno durante 14 meses tenía el 59 % de los túbulos completamente reducidos, con diminutos depósitos de calcio.
• Pruebas genéticas detalladas en células individuales de un joven de 14 años tras más de 52 meses de tratamiento (11.199 células, combinadas con datos públicos hasta 130.100 células) hallaron más del 90 % de las células formadoras de esperma detenidas en una fase temprana, y estados inusuales en las células de sostén que nutren el esperma en desarrollo.
• Un modelo informático entrenado con solo 10 personas (5 niños antes de la pubertad, 5 adultos jóvenes) juzgó que el tejido del joven de 14 años tratado era como el de un niño antes de la pubertad. Los propios autores dicen que el pequeño grupo de entrenamiento es una debilidad importante.
• Los autores concluyen que la reducción y las células inmaduras 'plantean una posible preocupación' sobre la reversibilidad total y la fertilidad futura. El estudio no probó la recuperación tras dejar el tratamiento ni midió la fertilidad.

Abstract

Spermatogonial stem cell (SSC) acquisition of meiotogenetic state during puberty to produce genetically diverse gametes is blocked by drugs collectively referred as 'puberty blocker' (PB). Investigating the impact of PB on juvenile SSC state and function is challenging due to limited tissue access and clinical data. Herein, we report largest clinically annotated juvenile testicular biorepository with all children with gender dysphoria on chronic PB treatment highlighting shift in pediatric patient demography in US. At the tissue level, we report mild-to-severe sex gland atrophy in PB treated children. We developed most extensive integrated single-cell RNA dataset to date (>100K single cells; 25 patients), merging both public and novel (52 month PB-treated) datasets, alongside innovative computational approach tailed for germ cells and evaluated the impact of PB and aging on SSC. We report novel constitutional ranges for each testicular cell type across the entire age spectrum, distinct effects of treatments on prepubertal vs adult SSC, presence of spermatogenic epithelial cells exhibiting post-meiotic-state, irrespective of age, puberty status, or PB treatment. Further, we defined distinct effects of PB and aging on testicular cell lineage composition, and SSC meiotogenetic state and function. Using single cell data from prepubertal and young adult, we were able to accurately predict sexual maturity based both on overall cell type proportions, as well as on gene expression patterns within each major cell type. Applying these models to a PB-treated patient that they appeared pre-pubertal across the entire tissue. This combined with the noted gland atrophy and abnormalities from the histology data raise a potential concern regarding the complete 'reversibility' and reproductive fitness of SSC. The biorepository, data, and research approach presented in this study provide unique opportunity to explore the impact of PB on testicular reproductive health.

Conclusion

The authors report mild-to-severe testicular tubule atrophy in puberty-blocker-treated children and an immature, prepubertal-like profile in the testis of a patient treated for more than 52 months. They conclude that, combined with the gland atrophy and histological abnormalities, this raises 'a potential concern regarding the complete reversibility and reproductive fitness' of spermatogonial stem cells. They also report rare post-meiotic (spermatid-like) cells in prepubertal tissue, irrespective of age, puberty status or treatment. They say the biorepository, data and research approach 'provide unique opportunity to explore the impact of PB on testicular reproductive health.'