Study Reveals How Imaging Technology Can Track Stem Cell …

When you buy a replacement alternator for your 88 Toyota Corolla, its easy enough to see the new part. The same cannot always be said for the replacement cells that are being tested for healing or replacing diseased tissue. These cells, derived from various kinds of stem cells, have great healing potential, but as they enter clinical trials, scientists need better ways to identify the transplanted cellsand the daughter cells they spawn.

In a lab at the Wisconsin Institutes for Medical Research, PhD student Christina Lewis examines an MRI scan of a rat brain to determine how quickly a specific contrast agent gets distributed throughout the organ. Her findings will establish a baseline for future tests involving stem cells transplants. (Photo: Nik Hawkins)

Cell therapies are beginning to be tested in clinics, and we need a way to explain why we see the results we see, says Christina Lewis, a PhD student in the lab of Masatoshi Suzuki, assistant professor of comparative biosciences at the UW School of Veterinary Medicine.

For example, neural cells grown from stem cells are being tested to treat ALS, the fatal nerve-muscle disorder sometimes called Lou Gehrigs disease, Lewis says. If we dont see an improvement, we need to understand what went wrong. Did the cells die? Did they migrate somewhere else?

And if the patient does improve, knowing that the transplanted cells are present and alive helps document that the treatment works.

Lewis, Suzuki, and colleague Stephen Graves, a research assistant in the UW-Madison Department of Medical Physics, have tested a solution to the problem in the form of a gene in the stem cells that picks up a manganese isotope that can be seen by both PET (positron emission tomography) and MRI (magnetic resonance imaging) scanners. The isotope serves as a beacon for the transplanted cells, revealing their location in the body.

PET and MRI are both useful, says Lewis, and this combination gives us flexibility, depending on what is available in the clinic. MRI gives great soft-tissue contrast and good detail and shows the surrounding anatomy. PET can detect a very small amount of the manganese contrast agent so we can reduce the dose of the agent.

Finally, because the detection rests on a genetic alteration of the stem cell, subsequent generations of cells can also be seen, says Suzuki, an expert in neural stem cells. We can potentially monitor cell survival and behavior for months or even years.

The new technique would need approval from the Food and Drug Administration before entering human clinical trials.

Lewis and Suzuki published the results of their study in the journal Theranostics. Other collaborators include medical physics professors M. Elizabeth Meyer and Robert Nickles.

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Study Reveals How Imaging Technology Can Track Stem Cell ...