New nano-‘tracking devices’ allow doctors to visualize stem cells inside hearts

Heart stem cell therapy after a major heart attack holds the promise of helping to repair severely damaged cells by encouraging the growth of new ones. However, the process which involves infusing healthy stem cells into the heart to replace the damaged tissue has had limited success in clinical trials.

In order to get the most benefit from heart stem cell treatment, it is essential for doctors to properly place the cells in the heart. But, once the stem cells are injected, its difficult to determine exactly where they wind up, and many scientists believe faulty placement is ultimately the culprit of the therapys disappointing results.

Now, that problem could be potentially solved with a new visualization technique developed by Dr. Sam Gambhir and fellow researchers at Stanford University School of Medicine in California. Their study, published in Science Translational Medicine, details the invention of silica nanoparticles, which can be injected inside stem cells, acting as tiny tracking devices that allow doctors to see the stem cells path inside the body.

According to the studys researchers, the most encouraging results from heart stem cell therapy have been seen after bypass surgery, which is done right after a patient has suffered a heart attack. If performed correctly, stem cell injections can encourage new cell proliferation and help increase blood flow up to 10 percent.

To get the most benefit, doctors have to find the perfect place in which the cells will do the most work.

The best place is the region (in the heart) between the damaged tissue and the healthy tissue, Jesse Jokerst, a postdoctoral fellow in the Stanford Molecular Imaging Scholars Program and one of the studys authors, told Thats where the most therapeutic benefit can occur. When placed there, the stem cells can take advantage of the blood flow in the healthy region, but can effect a change in the diseased region.

In order to determine where to place the cells, physicians currently take images of the heart through magnetic resonance imaging (MRI) one image before the injection to estimate placement, and a second image after the injection to see how the cells have developed. But the time period between the capture of those pictures leaves a lot to be desired, as the stem cells do not have a unique signature that allows doctors to differentiate between them and the normal heart cells.

Feeling somewhat blind, the doctors have many questions once the stem cells are injected. Did they reach their intended target? Did they remain at the heart wall? How many cells actually stayed and how many diffused or died? Inevitably, the doctors have to wait weeks following the stem cell injection to get their questions answered, by observing if heart function improved.

Making a stem cell 'movie'

Frustrated by those time constraints, the researchers realized all their questions could be answered a lot faster and much more accurately through ultrasound imaging.

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New nano-'tracking devices' allow doctors to visualize stem cells inside hearts

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