Until now, it was not fully clear why
coughing is unable to clear the mucus in
and similar lung conditions.
The study team comprising members from a host of scientific disciplines ranging
from cell biology to materials science
and whether these could be responsible for difficulties in
clearing out the secretions by coughing.
Physicochemical Properties of Normal and Disease-Associated Mucus
cough reflex creates high-velocity airflow that breaks apart the mucus and
simultaneously tears it free from the airway lining which then enables it to be
coughed out. This process seems to be affected
in lung conditions such
as asthma, COPD, cystic fibrosis and chronic
- The team at UNC developed a sophisticated system to
test the mechanical force needed to dislodge and break up normal as
well as cystic fibrosis (CF) type mucus.
- They obtained
airway-lining cells from the lungs of transplant patients and grew them in
laboratory dishes. These cells were then able to produce their own mucus and appeared
like miniature versions of actual airway lining cells
- Since, mucus is a soft sticky substance, the team developed a method to embed tiny meshes, which bind
firmly to the mucus.
- Using a silk
thread, this mesh was then connected to a motor having a force
sensor to quantify the force required to tear apart the mucus from the
lining of the airways
- This arrangement enabled testing of the adhesive and
cohesive forces of mucus and comparing these forces in normal mucus
and disease associated mucus.
Brian Button, PhD, associate professor of biochemistry and biophysics and
member of the UNC Cystic Fibrosis Research and Treatment Center at UNC-Chapel
Hill, "We found that the adhesive and cohesive strengths of mucus
increase dramatically when the ratio of mucins to water is higher than normal.
In CF mucus, those strengths exceeded the forces produced by coughing. That
means coughing would have a substantially reduced ability to clear mucus."
Testing the Efficacy
of Popular Cystic Fibrosis Treatments in Altering the Property of Mucus
The UNC and
Duke scientists also used this experimental design at the same time, to test
the efficacy of two popular forms of CF treatments
properties mucus in cystic fibrosis.
- First treatment - inhaled
saline and hypertonic saline (more salt content than body water) -
increases the water content in mucus to make it thinner.
- Other types of treatments or "mucolytic"
agents decrease viscoelasticity of mucus by cutting up or separating
mucin molecules, thereby reducing the stiffness of the mucus
showed that both forms of treatment are equally efficient in reducing the
adhesive and cohesive strengths
of CF mucus.
Michael Rubinstein, professor in the Department of Mechanical Engineering and
Materials Science at Duke University, said, "We measured the adhesive
forces that bind mucus to the airway lining and the cohesive forces that hold
mucus together, and identified several agents that show promise in reducing the
strength of mucus's adhesive and cohesive interactions."
patients and for minor respiratory ailments, either of these therapies will
work, but since their effects are additive, combining the two treatments
will be of benefit in patients with severe airway diseases.
To use the
experimental system, it is
necessary to study in detail the properties of mucus and
response to therapies in other respiratory diseases as well and see how mucus
clearance can be improved with newer strategies.
- Can Scientists Change Mucus to Make It Easier to Clear, Limiting Harm to Lungs? - (http://news.unchealthcare.org/news/2018/november/can-scientists-change-mucus-to-make-it-easier-to-clear-limiting-harm-to-lungs)