Saturday, January 26, 2008

Replacement Body Parts

Since 1967, when Christiaan Barnard successfully performed the first successful human to human heart transplant, it has been painfully obvious that there are not enough human hearts available to meet the demand. Surgeons have tried various approaches to replacing damaged and worn out hearts--including baboon hearts, refrigerator sized machine replacement hearts, and most reacently, the AbioCor totally implantable artificial heart system. While the AbioCor's batteries can be rechared through the skin, they will eventually have to be replaced. Machine hearts are subject to failure of various types, and experience with them is still only short term.

Eventually, hearts will be "printed", along with other replacement organs. Other organs, such as the urinary bladder, have already been synthetically produced and implanted. But the heart's fibrous skeleton is too complex for scientists to mimic in the lab--to this point.

So lab scientists are learning how to scavenge heart skeletons wherever they can. University of Minnesota scientists have taken dead animal hearts and removed the dead cells--leaving the fibrous infrastructure. By injecting immature heart cells into the scaffolding--in a stepwise manner--they were able to revitalize the heart to the point of beating.
The team took a whole heart and removed cells from it. Then, with the resulting architecture, chambers, valves and the blood vessel structure intact, repopulated the structure with new cells.

"We just took nature's own building blocks to build a new organ," says Dr Harald Ott, a co-investigator who now works at Massachusetts General Hospital. "When we saw the first contractions we were speechless."

The work has huge implications: "The idea would be to develop transplantable blood vessels or whole organs that are made from your own cells," said Prof Doris Taylor, director of the Centre for Cardiovascular Repair, Minnesota, principal investigator.

The method could be used to grow liver, kidney, lung and pancreas, indeed virtually any organ with a blood supply.

In the meantime, researchers continue to work on alternatives--including artificial hearts that spin like a turbine, producing a constant blood pressure rather than a pulse. Such turbine hearts are said to be efficient in small sizes, making it easier to fit size constraints. Such hearts would still have the problem of requiring a power supply.

Rather than replacing the heart, methods of regenerating the existing heart are being developed. Techniques of injecting stem cells into the patient's heart have already produced positive results in some cases. Likewise, procedures that attach "sheets of muscle blasts" to the patient's heart have been successful in Japan. Clearly, it would be preferable if the patient's own heart can serve as a scaffold for cell replacement.

In several pathological processes, however, the underlying structure of the patient's heart has been rendered dysfunctional. Without extensive remodeling surgery, the heart's infrastructure has to be replaced.

In approaching heart replacement, patients, physicians, and families have to weigh the benefits and risks. With the rapid growth in viable choices for replacement, this process will necessarily become more detailed and informed.

Bioprinting organs, and other ways of regenerating or synthetically reproducing human organs, will be very expensive for a long time. That expense will push experimentation in different directions.

Originally published in Al Fin

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Wednesday, January 09, 2008

Mainstream Media Coverage of SENS

Most readers of Al Fin blog want to live long, happy, prosperous lives. Otherwise, why read this blog? I consider Aubrey de Grey's SENS program for radical life extension to be the best ongoing approach to significant improvement in human lifespan. Now the mainstream periodical, The Economist, takes a look at de Grey's regimen:
Dr de Grey, who is an independent researcher working in Cambridge, England, is a man who provokes strong opinions. He is undoubtedly a visionary, but many biologists think that his visions are not so much insights as mischievous mirages, for he believes that anti-ageing technology could come about in a future that many now alive might live to see.

Vision or mirage, Dr de Grey has defined the problem precisely. Unlike most workers in the field, he has an engineering background, and is thus ideally placed to look into the biological repair shop. As he sees things, ageing has seven components; deal with all seven, and you stop the process in its tracks. He refers to this approach as strategies for engineered negligible senescence (SENS).

The seven sisters that Dr de Grey wishes to slaughter with SENS are cell loss, apoptosis-resistance (the tendency of cells to refuse to die when they are supposed to), gene mutations in the cell nucleus, gene mutations in the mitochondria (the cell's power-packs), the accumulation of junk inside cells, the accumulation of junk outside cells and the accumulation of inappropriate chemical links in the material that supports cells.

It is quite a shopping list. But it does, at least, break the problem into manageable parts. It also suggests that multiple approaches to the question may be needed. Broadly, these are of two sorts: to manage the process of wear and tear to slow it down and mask its consequences, or to accept its inevitability and bring the body in for servicing at regular intervals to replace the worn-out parts.

The writers at The Economist seem to understand that the key to getting anywhere in science is to "break a problem into manageable parts". Then define hypotheses which are falsifiable. Then test your hypotheses, one by one.

Because this is the approach that de Grey and his program are taking--and since no one else has attempted anything else nearly so ambitious or logical--it is to de Grey, SENS, the Methuselah Foundation etc. that most interested parties look for advances in this area. Of course, breakthroughs can occur at unexpected times and places. The radar scope must still sweep a broad circle. But reading de Grey's book, Ending Aging, and following the progress of SENS, is a good place to start.

Hat tip Brian Wang

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