Lung microbes and bone marrow transplants
Optimal lung health is especially important for children about to undergo a bone marrow transplant to treat incurable blood diseases such as leukemia. Also called a hematopoietic cell transplant (HCT), this procedure offers a “hard reset” that uses chemotherapy to wipe out all the patient’s blood cells before replacing them with a new set of donor blood cells.
The problem is that HCT puts a lot of stress on the entire body, and about 12% to 39% of patients develop life-threatening infections and organ dysfunction, often affecting the lungs. Pulmonary disease accounts for 16% of deaths after this procedure in kids. Therefore, making sure the lungs are as healthy as possible before the procedure is important to ensuring success.
My research team and I were interested in discovering how the pulmonary microbiome might relate to lung health in children preparing to undergo this kind of transplant. To do this, we had 104 children breathe into a machine to test their lung function. Then, we measured the composition of their lung microbiome through a bronchoalveolar lavage. This process circulates a saline solution through the lungs of a patient under sedation. We then examine the fluid under a microscope and sequence the genomes of any microbes it contains to identify what types of microorganisms are present.
We found that patients with lungs depleted of their normal bacteria had higher amounts of potentially harmful bacteria that aren’t usually present in healthy lungs. Patients with depleted lung microbiomes also had worse lung function, including signs of scarring, trouble absorbing oxygen and damage at the cellular level.
This study also confirms our previous finding that children with depleted lung microbiomes are two to three times more likely to die from bone marrow transplantation than children without depleted microbiomes. Knowing the composition of the lung microbiome allowed us to more accurately predict who would survive the treatment procedure better than lung function tests alone.
We don’t yet know whether microbiome depletion causes or results from lung disease. But our study suggests that the lung microbiome may be important in predicting bone marrow transplant outcomes. Ultimately, we hope to use this information to develop treatments that restore or strengthen the lungs of high-risk children before they undergo transplantation.
