Evidence of Microbiome in Fetal Lungs

Introduction to Fetal Microbiome Research

Recent research indicates that fetal lungs can harbor a microbiome as early as 11 weeks of gestation. It has been established that babies are born with a bacterial microbiome already present in their lungs. However, the timeline and mechanism of how bacteria colonize the lungs remained unclear. This prompted researchers at the University of Alabama to investigate the possibility of microbiome formation occurring in utero.

Study Publication

The findings of this study were published in the American Journal of Respiratory and Critical Care Medicine.

Research Methodology

Sample Collection

To explore this hypothesis, researchers collected 31 samples from the placenta, intestine, and lungs of fetuses ranging from 11 to 20 weeks of gestation. The analysis of bacterial DNA was conducted both at the University of Alabama and the Lee Kong Chian School of Medicine in Singapore.

Analysis of Microbiota

The initial analysis performed in Singapore revealed 48 unique taxa in the lung samples, 11 unique taxa in the placenta, and 24 taxa that were shared between the lungs and the placenta. The follow-up analysis from Alabama corroborated these results and identified two distinct groups within the lung microbiomes based on gestational age: 11-15 weeks and 16-20 weeks, indicating a change in microbiome diversity over time.

Understanding Bacterial Colonization

Possible Sources of Bacteria

The exact process by which bacteria colonize the fetal lungs remains a topic of discussion. Given that the placenta microbiome showed overlapping bacteria with the lung microbiome, researchers speculate that bacterial DNA may pass from the mother through the placenta to the fetus. Early bacterial presence might serve to “prime” the immune system, preparing the fetus for future bacterial encounters.

Future Directions in Fetal Microbiome Research

Unanswered Questions

While this study confirmed the existence of a microbiome in fetal lungs, several questions warrant further investigation. Researchers are eager to understand the dynamics of fetal microbiome evolution, the factors contributing to its diversification over weeks, and alternative pathways for bacterial entry into the lungs if not from the mother.

Implications for Immune System Development

Future studies may provide insights into how the formation of the microbiome influences the development of the immune system. If the hypothesis regarding bacteria “priming” the immune system proves correct, it raises intriguing questions about the potential for microbiome manipulation. This could lead to strategies aimed at enhancing immunity to specific diseases.

References

Al Alam D, Danopoulos S, Grubbs B, et al. Human fetal lungs harbor a microbiome signature. Am J Respir Crit Care Med. 2020;201(8):1002-1006. doi:10.1164/rccm.201911-2127LEEurekAlert!. (2020). Human fetal lungs harbor a microbiome signature. [online] Available at: https://www.eurekalert.org/pub_releases/2020-01/uoaa-hfl011720.php [Accessed 23 Jan. 2020].