Researchers at the School of Medicine have found that an increase in the presence of a heart donor’s DNA in a recipient’s blood is an early indicator of organ rejection.
“In the patients who never rejected, we saw a very constant low level of donor DNA in the recipients’ blood, in marked contrast to patients who rejected,” said Hannah Valantine, professor of cardiovascular medicine.
Valantine co-authored the study with professor of bioengineering Stephen Quake. Their findings were published Monday in the Proceedings of the National Academy of Sciences.
Over the last 40 years, rejection in heart transplant patients has been monitored by taking small heart biopsies and analyzing them for evidence that the body is attacking the heart, Valantine said. This procedure is performed up to 12 times in the year following the transplant and is quite uncomfortable for the patient.
The study implies that an ordinary blood test could eventually replace these surgical biopsies.
“The beauty of this new test is that it bypasses the need to monitor the immune response,” Valantine said.
The team discovered that the level of a donor’s DNA rises considerably before a heart biopsy shows evidence of a problem.
“We think we can pick up the rejection a lot earlier, and we can see how it improves after a patient has been treated for rejection,” Valantine said.
“This has huge implications for the patient,” she said, noting that treating heart rejection has many side effects. “If we were to pick this up early, we would not need to treat the patient with such heavy anti-rejection therapy.”
The research team also included Thomas Snyder, a research associate in Quake’s lab, and Kiran Khush, an instructor in cardiovascular medicine.
Stanford’s collaborative atmosphere played an important role in Valantine and Quake’s research.
“This is a very interesting demonstration of the huge advantage of being at Stanford with the opportunity to collaborate,” Valantine said.
When Valantine read Quake’s publication on detecting fetal abnormalities by examining fetal cells in the mother’s blood, she noticed parallels with organ transplant, since both involve the presence of a foreign protein in the blood.
The researchers’ approach, which they call genome transplant dynamics (GTD), can be applied to other organ transplants, reducing the need for invasive techniques, Valantine said.
“There has been very little progress in reducing chronic rejection,” Valantine said. “We now have the potential to pick up early markers of chronic rejection and thereby intervene and reduce chronic rejection and organ lapse.”