Fig. 2

A Structure of hyaluronic acid. B Schematic diagram illustrating the key steps involved in hyaluronic acid (HA) synthesis and degradation. The diagram shows that the synthesis of HA is regulated by various factors, such as growth factors, cytokines, kinases, and other proteins that modulate the activity of HA synthases (HAS1, HAS2, and HAS3). These enzymes are responsible for synthesizing HA chains, which are then bound by HAS protein complexes and extruded onto the cell surfaces and into the extracellular matrix (ECM). The biological actions of HA are tightly regulated by its degradation, which is carried out by several hyaluronidase enzymes, including HYAL-1, HYAL-2, HYAL-3, HYAL-4, PH20/SPAM1, HYAL-P1, and ROS. These enzymes cleave the HA chains into smaller fragments, which can be metabolized or eliminated from the body