Thursday, August 9, 2012

Technology for healing hearts...

Just read an article in Science Translation Medicine, where researchers have used nanofibers to repair heart. Here is what they did:

Currently, there are no approved therapies in regenerative
medicine for heart failure. In this work, scientists have used nanotechnology materials to repair vital tissues damaged by heart attacks in animals. The experiments, done in rats and pigs, led to the growth of fresh blood vessels and improved heart function without harmful side effects.
To promote blood-vessel growth in the heart, a protein called vascular endothelial growth factor, or VEGF was delivered. Previously this method hasn't worked well because the heart's blood circulation tends to rapidly wash away the VEGF. In this work the researchers developed an engineering fix for the problem. They made fibers from bits of protein and then assembled them into a lattice-like structure. Each fiber is just five nanometers wide and 100 nanometers long. The lattice structure is in the form of a sticky gel. The scientists mixed it with the VEGF and injected the combination into the hearts of two groups of test animals, rats and pigs, in which they had induced heart attacks. (Pig hearts bear significant similarities to human ones.) In both cases, instead of being washed away, the VEGF stayed on the lattice and slowly got released over several weeks.

Source: WSJ

Bone-marrow stem cells normally circulate in the blood and are part of the "repair crew" for damaged tissue. In the animal experiments, when those cells sensed the release of VEGF, they relocated to the heart and began to grow tiny blood vessels known as capillaries. The nanofibers create a special microenvironment in the heart for recruiting stem cells. However, fresh capillary formation isn't enough to help a failing heart. For regeneration to continue, stem cells from both the bone marrow and the heart itself must be coaxed to grow a second layer of tissue that is necessary for the formation of arteries, which are bigger and thicker than capillaries.

To the scientists' surprise, the prolonged release of VEGF achieved that result. The researchers also detected the creation of fresh heart muscle. This, too, is significant because the "scarring" tissue that naturally forms after a heart attack is thin and can get stretched in ways that alter the shape of the heart. In the latest experiments, the nanofiber gel appeared to strengthen these weak areas of the heart.
While the beneficial results in pig hearts were particularly important due to their resemblance to human ones, two challenges remain before the same technique can be safely attempted in people:
1. long-term effect in animals, and
2. determine the optimal time window" when the VEGF nanofibers need to be administered

Long live science...
For the aficionados, here is the full paper. 

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