A research team from McGill University in Montreal, Canada, reported that heart function in mice was preserved when monocytes—a type of infection-fighting white blood cell produced in the bone marrow—were implanted following a heart attack. Monocytes also stimulate the growth of new blood vessels, or angiogenesis.

Angiogenesis is important for the repair of damaged heart tissue. The researchers therefore chose to grow monocytes derived from mouse blood under angiogenic conditions prior to transplantation, in order to determine if these so-called monocyte derivatives (MDs) could be beneficial. They found that when MDs were transplanted into animal models of myocardial infarction, simulating a heart attack, the MDs secreted high levels of a variety of beneficial growth factors that have anti-inflammatory properties and that stimulated the growth of endothelial cells that comprise the inner lining of blood vessels.

“In this study, we demonstrated that myocardial protection following infarction can be induced in part by growth factors released by MDs,” said the study’s lead author Dr. Jacques Galipeau, associate professor of medicine at McGill University’s Lady Davis Institute for Medical Research. “This finding strongly suggests that these released proteins reduce cardiac cell (death) and enhance (blood vessel) cell proliferation in vitro, and reduce (scarring) in vivo.”

The researchers also noted that the majority of MDs did not persist more than two weeks when grown outside of the body, suggesting that the benefits created by the cells occured shortly after injection. The study was published in the Journal Cell Transplantation.