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自由論壇 > 研究發現造血幹細胞量影響人壽

研究發現造血幹細胞量影響人壽

26-04-2014

 科學 – 研究發現造血幹細胞量影響人壽

 

荷蘭一位女人瑞在二零零五年過身的時候,答應把遺體捐給科學界研究,有關成果近日首度公開,研究發現一個人的造血幹細胞數量,可能影響一個人的天然壽命上限。 

她名叫安德爾席佩爾,是荷蘭著名女人瑞,於二零零五年逝世,享年一百一十五歲,是當時全球有紀錄以來最長壽的人。安德爾席佩爾臨終前提出,希望將自己的遺體捐出來,給科學界做研究。 

安德爾席佩爾是個珍貴的案例,因為她一百一十五歲依然很健康,例如她臨終前血管都沒有任何疾病,亦沒有患上癌症,而且頭腦到最後仍很清晰,可以說她純粹是肉體衰老至死,稱得上是享盡天年。 

所以科學家認為,安德爾席佩爾可以幫助他們了解所謂「天年」是什麼,即是沒有受意外和重病影響的話,一個人的壽命的天然上限,會由哪些因素決定?專家從安德爾席佩爾身上得到啟示,關鍵之一是造血幹細胞。 

人們血液的所有細胞,包括紅血球和白血球,都是由造血幹細胞分化而成,隨著每天新陳代謝,造血幹細胞會不斷分裂耗損。 

一般人與生俱來的造血幹細胞,大約有二萬個左右,而專家發現安德爾席佩爾過身時,全身的血液細胞大部份都是來自兩個幹細胞,即是她的造血幹細胞只是剩下兩個。 

由於身體是不會自己補充幹細胞,它們的數量只會跌不會升,所以安德爾席佩爾的個案反映,當一個人的造血幹細胞消耗殆盡,可能就是他油盡燈枯之時。 

不過專家強調,造血幹細胞可能只是其中一個影響壽命上限的先天條件,而且一個人最終可以活多久,後天的生活習慣亦很重要,但此次發現對於日後的幹細胞療法始終很有幫助。 

———————————————-
 

Stem cell 'exhaustion' may play role in human lifespan

Stem cell “exhaustion” may play a role in defining the limit of human lifespan, a study of blood from a dead Dutch super-centenarian suggests.

 

Analysis of white blood cells from 115-year-old Hendrikje van Andel-Schipper showed they were derived from just two related stem cell clones.

In a younger adult an estimated population of 10,000-20,000 “haematopoietic” stem cells produce “offspring” that replenish all the different kinds of blood cell.

Mrs van Andel-Schipper’s white blood cells also had much shorter “telomeres” − protective caps on the ends of chromosomes that shorten with age − than her brain cells.

“Most haematopoietic stem cells may have died from ‘stem cell exhaustion’”

Henne Hostege

When telomeres get sufficiently short, cells stop renewing themselves and may die.

“Because these blood cells had extremely short telomeres, we speculate that most haematopoietic stem cells may have died from ‘stem cell exhaustion’, reaching the upper limit of stem cell divisions,” said lead scientist Dr Henne Hostege, from Cold Spring Harbor Laboratory in the US.

Future studies were needed to see whether stem cell exhaustion might be a cause of death at extreme ages, said the scientists, whose findings are published in the journalGenome Research.

The researchers also identified more than 400 genetic mutations in the white blood cells which appeared to be harmless, unlike those found in patients with blood cancers such as leukaemia.

Hendrikje van Andel-Schipper

Hendrikje van Andel-Schipper

At the same time, they were not thought to confer any advantage that might have helped Mrs van Andel-Schipper to live such a long life.

The “somatic” mutations which are not passed on to offspring were mainly in non-coding regions of DNA not associated with disease.

At the time of her death in 2005, Mrs van Andel-Schipper, known as “Henny”, was officially the oldest person in the world. At the age of 82, she gave written consent for her body to be donated to science after her death.

A study of her brain found little sign of the changes normally associated with great age and no trace of Alzheimer’s disease. Scientists have also sequenced the whole of her genetic code.

Mrs van Andel-Schipper had surgery for breast cancer at the age of 100, and died 15 years later as a result of a gastric tumour that spread to her abdomen.

Since she never received mutation-inducing chemotherapy, the mutations seen in her DNA were purely due to normal ageing, said the scientists.

 

www.nursingtimes.net/stem-cell-exhaustion-may-play-role-in-human-lifespan/5070222.article

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