コロナ感染、男性の生殖機能に影響か　独研究

【パリＡＦＰ＝時事】男性が新型コロナウイルス感染症（COVID-19）に感染すると精子の細胞死や炎症、酸化ストレスが増加する恐れがあり、生殖能力が低下するかもしれないと指摘する研究が29日、生殖医学専門誌「リプロダクション」に発表された。（写真は資料写真）
　研究者らは、「男性の生殖器系がＣＯＶＩＤ-１９の影響を受け、損傷を受ける可能性を示す直接的な実験証拠が初めて得られた」と結論づけている。ただし、複数の専門家からは、新型コロナが男性生殖機能に影響を及ぼす「決定的な証拠」はまだ見つかっていないとして、研究結果の解釈に注意を促す声が上がっている。
　新型コロナウイルスが男性の生殖器にも感染し、精子形成や生殖ホルモンの分泌を阻害する恐れがあることは、これまでの複数の研究で分かっている。新型コロナウイルスが肺の細胞に侵入する入り口となる受容体が、精巣内にも見つかっている。だが、生殖機能への影響は明らかになっていない。
　独ユストゥス・リービッヒ大学ギーセンのベザド・ハジザデ・マレキ氏とバフティヤル・タルティビアン氏は、生殖機能への悪影響を示唆し得る生物学的マーカー（指標）を求めて実験を実施。新型コロナに感染した男性８４人を対象に６０日間にわたって１０日ごとに分析を行い、健康な男性１０５人のデータと比較した。
　感染者の精子細胞では、炎症と酸化ストレスを示すマーカーが著しく高かった。酸化ストレスとは体内の活性酸素と抗酸化作用のバランスが崩れた状態を指し、ＤＮＡやたんぱく質を損傷させる可能性がある。
　マレキ氏は、「精子細胞へのこれらの影響は、精子の質や生殖能力の低下に関連する」と説明。感染者の男性における値は「時間の経過とともに改善傾向が見られたが、依然として著しく、また異常に高いままだった」だったと述べている。また、症状が重かった人ほど数値が高かったとも指摘した。
　ただ、研究に参加していない専門家からは、さらなる研究が必要だとの声が出ている。英ケア・ファティリティ・グループの発生学専門家、アリソン・キャンベル医師は「現在のところ、ＣＯＶＩＤ-１９が精子や男性生殖機能に長期的な損傷を与えるとの決定的な証拠はない」と述べ、「男性は過度に警戒すべきではない」との見方を示した。
　英シェフィールド大学の男性生殖医療の専門家、アラン・ペイシー氏も、データの解釈について「強い注意喚起」を呼び掛けた。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2021/02/01-12:26）

Covid19 may damage sperm quality and reduce fertility in men, according to a new study based on experimental evidence.
The viral disease -- which has swept the globe, claiming nearly 2.2 million lives -- can cause increased sperm cell death, inflammation and so-called oxidative stress, researchers reported Friday in the journal Reproduction.
These findings provide the first direct experimental evidence that the male reproductive system could be targeted and damaged by Covid-19, the authors concluded.
Experts commenting on the research, however, said the capacity of the virus to compromise fertility in men remains unproven.
Covid-19 causes respiratory illness, especially in older people and those with underlying medical problems.
The world has seen more than 100 million confirmed cases since the disease emerged in central China at the end of 2019.
Transmitted through respiratory droplets, the disease attacks the lungs, kidneys, intestines and heart.
It can also infect male reproductive organs, impairing sperm cell development and disrupting reproductive hormones, earlier studies have shown. The same receptors the virus uses to access lung tissue are also found in the testicles.
But the effects of the virus on the ability of men to reproduce remained unclear.
Behzad Hajizadeh Maleki and Bakhtyar Tartibian from Justus-Liebig-University in Germany searched for biological markers that might indicate a negative impact on fertility.
Analysis done at 10-day intervals for 60 days in 84 men with Covid-19 was compared to data for 105 healthy men.
In the Covid-19 patients, sperm cells showed a significant increase in markers of inflammation and oxidative stress, a chemical imbalance that can damage DNA and proteins in the body.
- 'Strong note of caution' -
These effects on sperm cells are associated with lower sperm quality and reduced fertility potential, said Maleki in a statement.
Although these effects tended to improve over time, they remained significantly and abnormally higher in the Covid-19 patients.
The more severe the disease, the bigger the changes, he added.
The male reproductive system should be considered a vulnerable route of Covid-19 infection and declared a high-risk organ by the World Health Organisation, Maleki said.
Experts not involved in the study welcomed the research, but cautioned that more was needed before drawing hard and fast conclusions.
Men should not be unduly alarmed, noted Alison Campbell, director of embryology of the CARE Fertility Group in Britain.
There is currently no definitive evidence of long-lasting damage caused by Covid-19, to sperm or male reproductive potential, she told the London-based Science Media Centre.
The results could have been skewed, she added, by the fact that men recovering from Covid were treated with corticosteroids and antiviral therapies, while the control group was not.
Allan Pacey, a specialist in male reproductive medicine at the University of Sheffield, raised a stong note of caution on how the data was interpreted.
Some of the indicators of decreased sperm quality could be due to factors besides Covid-19, he said, noting that more men in the Covid-19 group were overweight.
The simple fact that only one group was very sick -- no matter the cause -- also needed to be taken into account, he added.
We already know that a febrile illness can impact on sperm production, regardless of what caused it.