New insights into the structural changes associated with osteoarthritis


Date:
July 5, 2023
Source:
Carl R. Woese Institute for Genomic Biology, University of Illinois
at Urbana-Champaign
Summary:
Osteoarthritis is the most common degenerative joint disease,
affecting 22% of adults over 40 globally. Although the condition
has been extensively studied through a medical perspective, the
molecular changes associated with osteoarthritis remain unclear. In
a new study, researchers have used a combination of techniques to
track the progression of the disease and the changes associated
with it.


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FULL STORY ========================================================================== Osteoarthritis is the most common degenerative joint disease,
affecting 22% of adults over 40 globally. Although the condition has
been extensively studied through a medical perspective, the molecular
changes associated with osteoarthritis remain unclear. In a new study, researchers have used a combination of techniques to track the progression
of the disease and the changes associated with it.

The cartilage in the joints, along with a lubricant known as the synovial fluid, provides a smooth surface that helps withstand weight-bearing
movements.

The fluid contains several molecules, including hyaluronan (HA) and phospholipids. Since the cartilage environment cannot be quickly healed
or repaired, researchers have tried to diagnose the early stages of
joint disease by monitoring the molecular weight and concentration of HA.

"Although we know that in healthy joints there is very low friction,
it is unclear which other molecules are involved and how they change
during osteoarthritis," said Rosa Espinosa-Marzal (EIRH), Donald Biggar
Willett Faculty Scholar and a professor of environmental engineering &
science, and materials science & engineering. "During the early stages
of osteoarthritis, cartilage starts degrading, and previous research has
shown that the molecular composition of the synovial fluid changes. We
wanted to see if the two changes are related to each other." In a
healthy joint, the molecular weight of HA varies between 2-20 MDa with
a concentration ranging from 1-4 mg/ml. However, in diseased joints, HA
is broken down resulting in a lower molecular weight. Additionally, its concentration is also reduced by ten times. Based on these observations,
made by other researchers, the study looked at how the concentration
and molecular weight of HA influences the structure of healthy and
diseased joints.

To do so, the researchers combined vesicles with high and low molecular
weight HA. Using neutron scattering and light scattering, they discovered
that the molecular weight of HA can vastly change the structure of the vesicles. Lower molecular weight HA, which mimics osteoarthritis-diseased joints, results in larger vesicle size. They also observed that the
molecular weight of HA changes the thickness of the phospholipid layers
in the joints.

The researchers also studied how these differences can influence the
formation of a protective film; in joints this film is responsible for the
very low friction we need for unhindered motion. Once again, they used a combination of techniques, quartz crystal microbalance and atomic force microscopy, to examine how these molecules assemble on gold surfaces.

"The formation of a film is possible only when there is an optimal concentration of HA and phospholipids. Even though the gold surfaces have
very little in common with cartilage, our studies indicate that there
could also be an optimum concentration under biological conditions," Espinosa-Marzal said.

"This is an important observation because we can use the concentration
changes as a diagnostic tool." "We are at a point where you need
to use multiple techniques on a complex system like this," said Mark
Rutland, a professor of surface science at the KTH Royal Institute of Technology. "None of these techniques alone would have given us any
insight. The key was to look at all the different effects and put the
pieces together to show that the molecular weight of HA has a huge effect
on the characteristics of the layer that is formed with phospholipids."
The researchers are now working on using cartilage to understand whether
their observations with gold surfaces also hold true in a biologically
relevant system. They are also interested in studying the other molecular components that are found in joints to build a more comprehensive model
of the changes that are associated with osteoarthritis.

* RELATED_TOPICS
o Health_&_Medicine
# Diet_and_Weight_Loss # Joint_Health #
Arthritis # Obesity # Medical_Imaging # Fitness #
Diseases_and_Conditions # Lupus
* RELATED_TERMS
o Arthritis o Osteoarthritis o Delirium o Molecular_biology
o Stem_cell_treatments o Hodgkin's_lymphoma o
Infectious_mononucleosis o Nutrition_and_pregnancy

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========================================================================== Journal Reference:
1. Kangdi Sun, Tooba Shoaib, Mark W. Rutland, Joesph Beller,
Changwoo Do,
Rosa M. Espinosa-Marzal. Insight into the assembly
of lipid-hyaluronan complexes in osteoarthritic
conditions. Biointerphases, 2023; 18 (2) DOI: 10.1116/6.0002502 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230705143002.htm

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