HA is a unique linear mucopolysaccharide, which is cross-linked by N-ethylphthalide-glucosamine and D-glucuronic acid. It is widely distributed in the extracellular matrix (such as the vitreous body, joint synovial fluid, cartilage, etc.) of human tissues. It has strong hydrophilicity and high viscoelasticity.
There are two kinds of sodium hyaluronate: Endogenous HA and exogenous HA. Endogenous HA is secreted by the human body, whose molecular weight is about 4-10*106 Da, and its concentration in synovial fluid is about 3.5 g/L; exogenous HA is exogenous supplementary HA, including low molecular weight HA (LMW HA, 0.5-1.5*106 Da) and high molecular weight HA (HMW HA, 6-7*106 Da). Exogenous HA can be supplemented when endogenous HA production and metabolism are abnormal, leading to tissue and organ dysfunction.

Hyaluronic Acid in the Treatment of Osteoarthropathy

At present, hyaluronic acid has been widely used in the treatment of osteoarthritis. Its mechanism is mainly reflected in the following three aspects:
(1) Covering, lubricating, and cushioning stress: HA in the synovial fluid has high viscoelasticity and plays a protective role in shock absorption and lubrication of articular cartilage; in addition, hyaluronic acid has a barrier effect on bacteria, toxins, and immune complexes, and can protect cartilage from the effects of enzymes, chemicals, and toxins. For example, Yasuda and other studies have found that the increase of inflammatory cytokines and matrix degradation products in osteoarthritis patients can induce the production of catabolic enzymes (such as collagenase and desaturase) leading to articular cartilage degeneration, while HA can inhibit the degradation of catabolic enzymes to cartilage, thus protecting cartilage.
(2) Alleviating inflammation: The combination of HA and HA receptors CD44 and CD168 can reduce the number of inflammatory cells and the synthesis and release of interleukin-1 (IL-1), prostaglandin E2 (PGE-2), matrix metalloproteinase, thus achieving the anti-inflammatory effect.
(3) Promoting the synthesis of endogenous macromolecule: By promoting the synthesis of endogenous macromolecule HA to improve the properties of the pathological joint fluid, to achieve the role of sustained relief of symptoms and delaying the progress of osteoarthritis; and by promoting the synthesis of proteoglycan and collagen to promote cartilage regeneration. Because of the short half-life of HA, it is speculated that the continuous improvement of symptoms after the injection of exogenous HA may be related to its promotion of endogenous HA synthesis.

Security

Sodium hyaluronate has good biocompatibility, complete metabolism in vivo, non-toxic, aseptic, non-chemotaxis, and good safety. At present, no systemic adverse reactions have been reported. The most common adverse reactions are mild pain and swelling in the injection area and joints, occasionally accompanied by a headache, fever, and drug eruption.

The patients can tolerate it without special treatment. Generally, the symptoms disappear after 2 to 7 days without affecting the daily activities of patients. For example, those with severe pain symptoms can take it orally and apply external analgesics. The complications of vascular and nerve injuries have not been reported in the literature.

Allergic reactions and joint suppurative infections are rare. However, patients with allergies to poultry and eggs should be cautious in using HA. If allergies are found, the drug should be stopped immediately and the corresponding anti-allergic treatment should be taken.

Sodium hyaluronate is safe and effective in the treatment of bone and joint diseases. It can relieve symptoms and improve joint function. In particular, intra-articular injection of HA is especially suitable for patients who are not well treated with analgesics or have drug contraindications and intolerable side effects. The application of HA greatly reduces the dosage of NSAIDs, medical expenses, and side effects.

The post How Much is Hyaluronic Acid for Joints appeared first on Stanford Chemicals.