Our bodies are colonized by a teeming, ever-changing mass of microbes that help power countless biological processes. Now, a groundbreaking study has identified how these microorganisms get to work shaping the brain even before birth. Researchers at Georgia State University have conducted a study using newborn mice specifically bred in a germ-free environment to prevent any microbe colonization. Some of these mice were immediately placed with mothers with normal microbiota, leading to a rapid transfer of microbes.
This experiment allowed the study authors to pinpoint just how early microbes begin influencing the developing brain. Their focus was on the paraventricular nucleus (PVN), a region of the hypothalamus tied to stress and social behavior, already known to be partly influenced by microbe activity in mice later in life.
Microbes and Brain Development: The Early Connection
“At birth, a newborn body is colonized by microbes as it travels through the birth canal,” says behavioral neuroscientist Alexandra Castillo Ruiz. “Birth also coincides with important developmental events that shape the brain. We wanted to further explore how the arrival of these microbes may affect brain development.”
When the germ-free mice were just a few days old, researchers found fewer neurons in their PVN, even when microbes were introduced after birth. This suggests that the changes caused by these microorganisms occur in the uterus during development. The neural modifications last into adulthood: the PVN remained neuron-light in adult mice raised germ-free. However, the cross-fostering experiment was not continued into adulthood (around eight weeks).
The Role of Maternal Microbes
The details of this relationship still need to be worked out and researched in greater detail, but the takeaway is clear: microbes, specifically the mix of microbes in the mother’s gut, can play a notable role in the brain development of their offspring. “Rather than shunning our microbes, we should recognize them as partners in early life development,” says Castillo-Ruiz. “They’re helping build our brains from the very beginning.”
While this has only been shown in mouse models so far, there are enough biological similarities between mice and humans to suggest that humans might also be shaped by their mother’s microbes before birth. This raises important questions about practices like Cesarean sections and the use of antibiotics around birth, which are known to disrupt certain types of microbe activity, potentially affecting the health of newborns.
Implications for Human Health
In particular, these disruptions could lead to changes in stress and social behavior, as managed by the PVN part of the brain. However, it’s too early to make any definitive conclusions. As the researchers note, this area “merits further investigation.” An obvious follow-up would be to investigate how the microbiota of mothers-to-be can be altered. Previous research has already linked these gut microbes to changes in diet, sleep patterns, alcohol intake, and overall health.
“Our study shows that microbes play an important role in sculpting a brain region that is paramount for body functions and social behavior,” says Castillo-Ruiz. “In addition, our study indicates that microbial effects start in the womb via signaling from maternal microbes.”
The research has been published in the journal Hormones and Behavior. As science continues to uncover the complex interplay between microbes and human development, this study adds a crucial piece to the puzzle, suggesting that the microbial environment of the womb could have lasting effects on brain development.
This development follows a broader scientific interest in the human microbiome and its impact on health. As researchers delve deeper into this field, the potential for new therapeutic approaches and preventive measures becomes increasingly apparent. The move represents a significant step forward in understanding the intricate connections between our biological processes and the microscopic world within us.
