- Mucus coats the body’s internal surfaces, where it acts as a barrier against pathogens and a food source for friendly bacteria.
- Its main constituents are mucins — proteins studded with sugar molecules in distinct patterns that determine how the mucus interacts with beneficial and pathogenic microorganisms.
- Scientists have now created a cell-based platform for producing these mucins with specific properties to order.
- Researchers could use the platform to develop mucin-based treatments for viral and bacterial infections.
Mucus is a slimy material with a wide range of vital functions at the interface between the body and the outside world.
It coats the cells that line the lungs, gut, and genital tract, where it provides a barrier against noxious substances and acts as a lubricant.
In the gut, as in the other body surfaces, mucus also serves as a gatekeeper, excluding pathogens and admitting beneficial microorganisms.
The main constituents of mucus are mucins, which are proteins decorated with distinctive patterns of sugar molecules.
These not only provide a food source for bacteria, but can also act as anchors to hold them in place when they bind to molecules in bacterial cell walls called adhesins.
By binding to the adhesins of pathogens, mucins secreted into fluids such as saliva and tears can prevent these microbes from clumping together. Mucins can also dissolve the pathogens’ “biofilms.”
Biofilms are an aggregation of bacteria that have collaborated to form thin coatings on teeth and other tissue surfaces. In some cases, biofilms can have a negative impact on health.
The patterns of sugar molecules on mucins therefore play a vital role in determining how the body interacts with microorganisms.
Mucins are tricky to isolate and study, however, so our understanding of how they work has been limited.
Now, a team of researchers has developed a way to create human mucins that display particular patterns of sugar molecules.
A team led by researchers at the Copenhagen Center for Glycomics can now genetically program laboratory cultures of human embryonic kidney cells to produce mucins that bind to specific bacterial adhesins.
Their work appears in Nature Communications.
The authors believe that doctors could one day prescribe mucins that either promote the growth of beneficial species or inhibit disease-causing species.
“An incredible number of diseases have a connection to the intestinal flora, but we still know very little about how we can control the intestinal flora in the treatment of diseases. This is where synthetic mucins could open up new treatment options,” says Yoshiki Narimatsu, an associate professor of glycobiology at the University of Copenhagen and one of the study’s lead authors.
“Ultimately, one can imagine using mucins as a prebiotic material, that is, as molecules that help the good bacteria in the body,” he adds.
The researchers also speculate that artificial mucins could be used instead of antibiotics to treat bacterial infections.
For example, doctors could deploy synthetic versions of the mucins in saliva and tears to flush away bacteria that would otherwise form harmful biofilms.
“We imagine that instead of using antibiotics, you might produce, for example, eye drops with the mucin that normally removes the bacteria in the treatment of eye infections,” says Dr. Narimatsu.
Mucins could even be deployed to compete with the common flu virus and prevent it from infecting cells that line the nose, windpipe, and lungs.
To infect cells in the respiratory tract, the virus latches onto sugar molecules called sialic acids in the cells’ membranes.
But to release newly created virus particles and continue the infection, the virus has to use an enzyme to break its attachment to the sialic acids.
“Mucins contain vast quantities of sialic acids,” co-lead author Prof. Henrik Clausen told Medical News Today.
These acids not only bind to free virus particles, which prevents them from locking onto host cells in the nose, lungs, or both — they also compete for the use of the enzyme that liberates new virus particles.
“In this paper, we only study the effect on [the] release of the virus, and we find that specific mucins with sialic acids block [the] release of the influenza virus and hence its ability to propagate and spread the infection,” Prof. Clausen explained.