Friday, April 2, 2010

How to mend a broken heart

Nope, this isn’t advice for the forlorn. I am referring to an actual physically broken heart. And, this represents cool science at its finest.

Researchers have long been interested in animals that can repair themselves. Lizards and salamanders can drop their tails if they are caught by a predator, and then re-grow them. Fish can repair damaged fins. But, we humans cannot re-grow a limb if lost. Can we figure out how these other animals do this and put it to work?

Recent work at the Salk Institute in San Diego purposely maimed the hearts of zebrafish (cute little aquarium fish you can find at your local pet store), and found they could regenerate up to 20% of that organ. That is a lot of heart to re-grow.

The heart is probably the most important organ in your body. I say probably because your brain is right up there in terms of keeping things going from minute to minute. If your heart is damaged, and you are losing blood, you’ve got only a few minutes left. But, zebrafish can stop the bleed, and then slowly, over days, repair the damage eventually producing a heart that was as good as the former.

How are they doing this? Science has long speculated that this is the work of stem cells. Stem cells are those cells that are not ‘determined’, meaning the kind of cell they are to become has not been decided yet by the body. They do not know yet what their job in life will be, be it bone cell or skin cell. Therefore, theoretically, we can use stem cells to initiate repairs.

Stem cell research has gotten a lot of attention lately, much of it controversial. The problem is, philosophically, where stem cells come from. We have some stem cells as adults, such as in our bone barrow; they don’t divide as well, cannot turn into as many things, and do not initiate repair as well as embryonic stem cells. Back in the 70’s scientists were able to make embryonic stem cells divide, meaning they can make more of them. Embryonic stem cells are completely undetermined, as opposed to adult stem cells, and most of our understanding of organ development and tissue repair has come from this line of work. Though, we have made breakthroughs in the last couple of years with adult stem cells. There is terrific coverage of this research and the controversy at the NIH website.

But, the amazing thing about this heart research is that it is not stem cells initiating the repair. Adult heart cells are doing the work. The adult heart cells initiate a repair response, much like a stem cell, and then divide rapidly to do the work. Other researchers tried this study in mice, to see if mammals could do what the fish could. They found out that the mammalian adult heart cells went back into a sort of stem cell like state and began to initiate repairs, but the cells did not proliferate, they did not divide. So, there were not enough of them to do the job. The trick now is getting them to proliferate. And, that is probably going to take some more research on stem cells to figure out how and why they proliferate, when the adult cells cannot.

In the meantime, try to keep your heart intact for a little while longer. We don’t have the fix quite yet.


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