Osteoarthritis, a degenerative joint ailment that impacts more than 35 million adults in the United States, occurs due to the deterioration of cartilage. While the exact process behind the breakdown of cartilage in osteoarthritis remains unclear, mechanical stress with inadequate self-repair is thought to be the primary factor responsible for the damage.
According to a new study, the composition of joint lubricant may be a potential cause of osteoarthritis.
The use of neutron and light scattering, atomic force microscopy, and quartz crystal microbalance has led to the discovery of a mechanism that explains the “vicious circle” of osteoarthritis.
Despite affecting over 35 million adults in the U.S., the precise process of cartilage breakdown in osteoarthritis remains unclear, although mechanical stress with inadequate self-repair is thought to be the primary factor.
The concentration and molecular weight of hyaluronic acid, a component of synovial fluid or joint lubricant, decrease substantially in cases of osteoarthritis and are often utilized as a diagnostic tool for the disease.
A recent study conducted by an international group of researchers and published in AIP Publishing’s AVS journal Biointerphases delved into the breakdown of hyaluronan and the potential implications of these changes on joint lubrication and wear.
According to Rosa Maria Espinosa-Marzal, a co-author from the University of Illinois Urbana-Champaign, the viscosity of synovial fluid is one of its most critical properties.
Viscosity refers to a fluid’s resistance to flow and is measured by the internal frictional force between adjacent layers of the fluid in relative motion.
High molecular weight polymers like hyaluronic acid are crucial for maintaining the fluid’s high viscosity, which, in turn, helps sustain a fluid film and decreases friction between articulating surfaces during motion.
The team conducted an analysis using neutron and light scattering, performed by Changwoo Do and Tooba Shoaib at Oak Ridge National Laboratory, which revealed that the structure of lipid-hyaluronic-acid complexes in the bulk solution is influenced by its concentration and molecular weight.
Kangdi Sun and Espinosa-Marzal from the University of Illinois Urbana-Champaign, in partnership with Mark Rutland from the KTH Royal Institute of Technology, discovered that both the concentration and molecular weight of hyaluronic acid are significant factors that impact how the lubricant interacts with various surfaces.
The findings of the study “show low molecular weight hyaluronic acid, which mimics osteoarthritis-diseased joints, hinders the adsorption of the hyaluronic-acid-lipid complex,” adds Espinosa-Marzal. “The lack of the formation of an amorphous film on the surface may reflect a consequence of osteoarthritis, since this film should help reduce friction and wear.”
The researchers’ theory suggests that the absence of this amorphous film may accelerate the wear and tear of the cartilage surface. Conversely, high molecular weight hyaluronic-acid-lipid complexes generate an amorphous film that helps sustain the mechanical integrity and durability of effective lubrication in healthy cartilage.
Espinosa-Marzal stated that the studies on hyaluronic acid and hyaluronic-acid-lipid complexes do not entirely support the theory that hyaluronic acid provides high lubricity to the articular surface of cartilage, which remains a somewhat controversial topic.
However, the researchers’ findings suggest that low molecular weight hyaluronic acid likely plays a crucial role in this regard.
By investigating the intricate interplay between phospholipid and hyaluronic acid self-assembly and the impact of molecular weight on surface affinity, Rutland affirmed that their study sheds light on a mechanism that explains the “vicious circle” of osteoarthritis.
Source: 10.1116/6.0002502
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