The problem with lengthening telomeres with telomerase is that this is exactly what many cancer cells do to get around the limit of cell proliferation set by the limited length of telomeres.

I have a suspicion that just lengthening telomeres would cause a higher incidence of cancer.. potentially much higher. The research is important, however, and should be tested in mice to see what happens. I doubt this is the silver bullet, as you likely agree.

[Posted by: Dan C at January 19, 2010 8:38 AM]

I don't think telemere extension therapy will increase the incidence of cancer. Ways to increase telemere lengths in mice have been developed that do not cause cancer.

However, why do we think telemere shortening, in and of itself, is a cause of aging? I think its more of a bio-marker than a cause. Telemere lengths seems to be a regulated function. Whatever causes the regulatory mechanism to fail, allowing the telemeres to shorten, is the underlying cause of aging, not the telemere shortening itself. At least that how I see it.

[Posted by: kurt9 at January 20, 2010 4:34 PM]

I'm an employee of Sierra Sciences; however, I'm not on the scientific staff, and I don't speak for the scientists.

However, to answer kurt9's question, there are several reason we believe telomere shortening is a fundamental cause of aging. One of the most compelling is the paper by Bodnar, et al., "Extension of life-span by introduction of telomerase into normal human cells," Science, 1998. In that experiment, scientists at Geron Corporation inserted the telomerase gene into normal human cells.

As most of you probably know, there is a limit to the number of times our cells can divide before they senesce - the so-called "Hayflick limit." What this team found is that hTERT-positive human cells did not observe the Hayflick limit; they continued to divide indefinitely.

In other words, it's already established that you can essentially immortalize a human cell by activating telomerase. The question is whether this also applies to organisms.

But there are some compelling reasons to believe that it will. A follow-up experiment in 2000 at Geron demonstrated that when you take elderly skin cells and grow them on the back of a mouse, you see visibly old skin; when you then telomerize those cells and grow them on the back of a mouse, you see visibly young skin.

Further, to address Dan C's point about animal testing, perhaps most exciting of all is a 2008 experiment at Maria Blasco's lab at the CNIO in Spain; Blasco's team found that, by overexpressing telomerase in mice, they could create a strain of mice that lived 40% longer and were still completely youthful and healthy at the point the control mice were losing their dexterity.

Of course, mice don't age in exactly the same way as humans, and Dr. Blasco's techniques would not work on an already-living organism, so there's no way to move this technique into clinical trials - but it's an important demonstration of concept.

At Sierra Sciences, we wouldn't assert that telomere shortening is the *sole* cause of aging, but we do believe that the science is very clear that it's a fundamental cause of aging, and we think any permanent cure for aging is absolutely going to need to include a mechanism for maintaining telomere length.

[Posted by: Jon Cornell at February 8, 2010 12:57 PM]