Lubricin

Lubricin is a glycoprotein that is secreted by synovial cells and superficial zone chondrocytes. It is also known as Proteoglycan 4 (PRG4), Superficial Zone Protein (SZP), and Mucin-like Protein. Lubricin plays a crucial role in biolubrication and wear protection of articular cartilage in joints.

Structure

Lubricin is a large, water-soluble glycoprotein with a molecular weight of approximately 345 kDa. It is composed of a protein core with numerous O-linked oligosaccharide chains attached. The protein core contains multiple tandem repeat sequences, which are thought to contribute to its lubricating properties.

Function

Lubricin functions primarily as a lubricant and wear protector in the joints. It is secreted into the synovial fluid, where it adheres to the surface of articular cartilage. This forms a thin, slippery layer that reduces friction and wear between the cartilage surfaces during movement. In addition to its lubricating properties, lubricin also has anti-adhesive and anti-inflammatory effects, and it may play a role in preventing cartilage degradation and osteoarthritis.

Clinical significance

Deficiency or dysfunction of lubricin can lead to increased friction and wear in the joints, which can result in joint pain and the development of osteoarthritis. Lubricin levels in the synovial fluid are often reduced in individuals with osteoarthritis, and this reduction is thought to contribute to the disease process. Conversely, increasing lubricin levels in the joints, either through injection or by stimulating the body's own production, may have therapeutic potential for treating osteoarthritis.

Research

Research into the role of lubricin in joint health and disease is ongoing. Studies have shown that lubricin has potential as a biomarker for osteoarthritis, as its levels in the synovial fluid can indicate the health of the joint. Additionally, research is being conducted into the potential use of lubricin as a therapeutic agent for osteoarthritis, with some promising results.

See also

• Synovial fluid
• Articular cartilage
• Osteoarthritis
• Glycoprotein
• Proteoglycan

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