Glial cells support nerve cells throughout our bodies.
Researchers have now found that, in our gut, the proper
organisation of glial cells depends on the presence of the
microorganisms that live there - and these cells play an important
role in responding to changes in the make-up of these
microorganisms.
The findings, from the Medical Research Council's National
Institute for Medical Research (NIMR; now part of the Francis
Crick Institute), help to explain how changes to gut
microorganisms such as after antibiotic treatment or recurrent
intestinal infections can predispose people to bowel disorders.
Dr Vassilis Pachnis from NIMR explained: "Our
intestine is inhabited by a vast number of microorganisms, known
collectively as microbiota. We have a symbiotic, or mutually
beneficial, relationship with these microbial communities. There's
clear evidence that they influence the function of several organs
including our brain, but we don't yet understand how this
happens.
To shed light on the issue, the scientists studied
the interaction between the neural networks in mouse intestines and
the microbiota inside their gut lumen.
Surprisingly, the team found that the networks of
neurons and glial cells in the intestine are highly dynamic and can
reorganise themselves in response to changes in gut microbiota.
They showed that these glial cells are continuously
renewed - and that this replenishment depends on the presence of
the microbiota. When the scientists reared mice in sterile
conditions (with no microorganisms present), no glial cells
developed in the mucosa, the innermost layer of the gut that is
closest to the intestinal contents. And when the team treated adult
mice with antibiotics, these glial cells were lost.
The findings suggest a possible mechanism for
communication between the inside of the gut, the enteric nervous
system and the brain.
Dr Pachnis said: "Our findings could have
far-reaching implications. Previous studies have shown that glial
cells in the enteric nervous system play a crucial role in
maintaining balance by keeping the fitness of the intestinal
epithelial barrier - a layer of cells that protects the inside of
our bodies from the often harmful contents of the intestine -and by
regulating the immune responses of the gut. Our current experiments
extend these studies and demonstrate that glial cells in the
intestine are well positioned to sense and respond to changes in
the gut microbiota.
"Therefore, our work provides a rational explanation
as to why changes in the composition of gut microbiota, such as
following the extensive use of antibiotics or recurrent intestinal
infections, could affect the organisation and function of the
enteric nervous system and beyond and predispose people to bowel
and other disorders.
"The next step is identifying and characterising the
signals used for communication between the microbiota and the
enteric glial cells. This could lead to the development of new
treatments to help protect the enteric nervous system, and in
particular its glial cells, against disease-causing microorganisms
and inflammatory gut conditions."
The paper, Microbiota controls the
homeostasis of glial cells in the gut lamina propria, is
published in Neuron.