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

• メイヨー・クリニックの小児の精巣組織バンクにある87人の患者のうち、16人（18%）に性別違和がありました。16人全員が思春期ブロッカーを使用しており、9人（56%）は妊孕性温存手術の時点でも使用中でした。
• 「思春期ブロッカー」として数えられた薬には、本来のブロッカー（リュープロレリン、ヒストレリン、トリプトレリン）のほか、エストロゲンやその他のホルモン薬（メドロキシプロゲステロン、スピロノラクトン）も含まれ、使用期間は3～52か月でした。手術時の平均年齢は12.5歳でした。
• 性別違和のある患者は全員、射精したくない、またはできないという理由で、精液の提供ではなく組織を摘出する手術を選びました。治療を受けた9人のうち2人は、診察時に精巣の異常がありました。
• がんのない提供者19人について、1人あたり約50本の管を調べたところ、治療を受けていない子どもでは年齢とともに管の中の細胞密度が上がりましたが、治療を受けた子どもでは年齢による変化は見られませんでした。ブロッカーとエストロゲンを14か月使用した12歳の1人は、管の59%が完全に萎縮しており、小さなカルシウム沈着が見られました。
• 52か月を超える治療を受けた14歳1人の単一細胞の詳しい遺伝子検査（11,199個の細胞、公開データと合わせて130,100個）では、精子を形成する細胞の90%以上が初期段階で止まっており、発達中の精子を育てる支持細胞にも異常な状態が見られました。
• わずか10人（思春期前の子ども5人、若い成人5人）で訓練したコンピューターモデルは、治療を受けた14歳の組織を思春期前の子どもの組織に似ていると判定しました。著者自身が、訓練に使った集団の小ささは大きな弱点だと述べています。
• 著者は、萎縮と未成熟な細胞が、完全な可逆性と将来の妊孕性について「潜在的な懸念を生じさせる」と結論づけています。この研究では、治療をやめた後の回復は検証されておらず、妊孕性も測定されていません。

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.'