HSCs are the precursors of ECM-producing myofibroblasts in liver fibrosis and the main cellular source of HA in the liver.4,32 HA is synthesized by a membrane-bound enzyme, HA synthase (HAS).3 HAS synthesizes HA using uridine diphosphate (UDP)-α-D-glucuronate (UDP-GlcUA) and UDP-α-N-acetyl-D-glucosamine (UDP-GlcUAc) as substrates (Figure 3A). The gene discussed is HAS1; the disease is Hepatic fibrosis.