Few things are probably as scary as learning you need a heart transplant. But then picture hearing that, after a suitable organ has been identified and transplanted, you'll need to undergo regular heart biopsies, in which surgeons snip off pieces of your new healthy organ for testing. Says cardiologist Hannah Valantine, MD:
Patients are very fearful of the biopsies; they hate having them done. They are also very expensive and carry risks of medical complications.
Now Valantine and bioengineer Stephen Quake, PhD, have come up with a new way to assess the health of a transplanted heart through a simple blood test. This is the second such blood test devised by Valantine; last year she published results showing that a blood test she help develop called AlloMap could be used to assess the health of transplanted hearts. The new technique, however, plays on a novel concept - that of looking for increasing levels of DNA from the donor in the blood of the recipient. It’s interesting because it springs from a unique way of looking at organ transplants, according to Quake:
Basically, when you get a new organ, you’re also getting a genome transplant. Someone else’s genome is put into your body, packaged in the donated tissue. So now we can use advances in genetic sequencing to identify which bits of DNA in the blood come from the recipient and which come from the donor.
The research will be published this week in the Proceedings of the National Academy of Sciences. The hope is that this type of ‘genome transplant dynamics’ study can be used in conjunction with the AlloMap to eliminate the need for invasive biopsies and - by diagnosing rejection in its very early stages - the use of high doses of immunosuppressants to treat advanced rejection episodes of nearly every organ.
You might remember Quake from previous news reports in which he first (in 2009) used technology he invented to sequence his own genome quickly and cheaply, and then (in 2010) collaborated with Euan Ashley, MD, at Stanford to come up with clinical recommendations for himself based on that sequence. He has also published widely covered research showing that it’s possible to identify fetal genetic abnormalities from a maternal blood sample. It was that research that attracted Valantine's attention:
When I saw that, I thought wow, this could probably be applicable to monitoring rejection. After all, transplanted organs are a completely foreign tissue. If he can detect DNA from a fetus, maybe we can use the same technique to find donor DNA in the patient's blood.
The researchers have now received a three-year, $2 million NIH grant to prospectively study heart and lung transplant recipients. Quake, Valantine and Thomas Snyder, PhD, (the paper’s first author) have filed for a patent on the use of this technique.