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

• Su 87 pazienti di una banca di tessuto testicolare infantile della Mayo Clinic, 16 (18%) avevano disforia di genere. Tutti i 16 avevano assunto bloccanti della pubertà, e 9 (56%) li stavano assumendo al momento dell'intervento di preservazione della fertilità.
• I farmaci considerati «bloccanti della pubertà» comprendevano veri bloccanti (leuprolide, istrelina, triptorelina) ma anche estrogeni e altri farmaci ormonali (medrossiprogesterone, spironolattone), assunti per 3-52 mesi. L'età media all'intervento era 12,5 anni.
• Tutti i pazienti con disforia di genere hanno scelto l'intervento di prelievo del tessuto anziché fornire un campione di sperma, perché non volevano o non potevano eiaculare. 2 dei 9 pazienti trattati avevano anomalie testicolari all'esame.
• Esaminando circa 50 tubuli per donatore in 19 donatori senza cancro, la densità delle cellule nei tubuli aumentava con l'età nei bambini non trattati, ma non mostrava alcun cambiamento con l'età nei bambini trattati. Un dodicenne in terapia con un bloccante più estrogeni da 14 mesi aveva il 59% dei tubuli completamente ristretti, con minuscoli depositi di calcio.
• Test genetici dettagliati su singole cellule di un quattordicenne dopo oltre 52 mesi di trattamento (11.199 cellule, combinate con dati pubblici fino a 130.100 cellule) hanno rilevato oltre il 90% delle cellule che formano spermatozoi bloccate in una fase iniziale, e stati insoliti nelle cellule di sostegno che nutrono gli spermatozoi in sviluppo.
• Un modello informatico addestrato su sole 10 persone (5 bambini prima della pubertà, 5 giovani adulti) ha giudicato il tessuto del quattordicenne trattato simile a quello di un bambino prima della pubertà. Gli autori stessi riconoscono che il piccolo gruppo di addestramento è un limite importante.
• Gli autori concludono che il restringimento e le cellule immature «sollevano una potenziale preoccupazione» sulla piena reversibilità e sulla fertilità futura. Lo studio non ha verificato il recupero dopo l'interruzione né misurato la fertilità.

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.'