In the 16th century, so the story goes, the Hungarian countess Elizabeth B谩thory bathed in the blood of young girls in a bid for eternal youth. More recently we have learned that the telomeres of our chromosomes become shorter as we get older, and this seems to be related to ageing. Without wishing to condone B谩thory鈥檚 deplorable sadism, if one were to take a blood sample from an infant, store it perfectly for 50 years, then reintroduce it to the body of the adult, could it have any positive effect?
Not really. Even if we knew what role the shortening of telomeres plays in ageing, telomere transfusions could hardly help. Telomeres are repetitive sequences of base pairs that act as disposable buffers at the end of chromosomes. In somatic cells, the telomeres undergo shortening during division, shortening that in reproductive cells would cost genetically useful material.
Cells with long telomeres do nothing to protect other cells that have lost their own telomeres. Each telomere affects only its own end of its own chromosome in its own cell.
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In reproductive cells such as oocytes and spermatogonia, a special enzyme called telomerase extends the telomeres to a good starting length. The process continues at least to the early stages of embryonic development and persists in some classes of stem cells. In particular, most blood cells are short-lived, so they have to be continually replenished from stem cells in the spleen, marrow and so on. This means a frozen autograft from these structures might serve to replace the stem cells of some critical tissues late in life, but blood transfusion would not. Stimulating telomerase production might work better, but it also could be risky because this is how some kinds of cancers survive.
鈥淪timulating telomerase production is risky 鈥� this is how some cancers survive鈥�
Jon Richfield, Somerset West, South Africa
There are really two separate questions here. The first is, what are the causes of ageing? Telomere shortening is one theory but it can鈥檛 really explain ageing because many animals such as the nematode worm age and die without undergoing cell division at all. Conversely, cancerous cells can effectively be immortal, undergoing thousands of cycles of cell division without any reduction of potency. Ageing is a complex interplay of many different phenomena including a gradual decrease in mitochondrial function because of oxidative stress and the build-up of misshapen proteins resulting from transcription mistakes and accumulated DNA damage.
The second question is whether a transfusion would work. The answer is no. Replenishing 鈥渁ged鈥� blood with 鈥測oung鈥� blood would not ameliorate any of the cellular phenomena that lead to ageing. The most probable outcome would be negative: the person involved would quickly become sick after the transfusion because the replaced blood would lack the circulating antibodies that the individual had built up over the preceding 50 years. As a result, germs that had not been a problem prior to the transfusion would suddenly find a new and easy target in the new blood circulating through the body.
鈥淕erms would suddenly find a new and easy target in the transfused blood鈥�
Allan Lees, Chief information officer, Buck Institute for Age Research, Novato, California, US