HAS1 (hyaluronan synthase 1) catalyzes the synthesis of hyaluronan (HA) by adding GlcNAc and GlcUA monosaccharides to the nascent polymer 1. As one of three hyaluronan synthase isozymes, HAS1 is essential for extracellular matrix (ECM) assembly and regulates critical cellular processes including adhesion, migration, and differentiation 2. Beyond its canonical role in ECM synthesis, HAS1 localizes to both cytoplasmic and nuclear compartments, where it influences cell cycle progression, motility, and gene transcription 32. In wound healing, HAS1-expressing fibroblasts exhibit fetal-like phenotypes and enhanced migratory capacity through the PIEZO1-calcium-HIF1α pathway 4. Clinically, HAS1 dysregulation associates with multiple pathologies: aberrant splice variants promote B-lineage cancer through dominant-negative effects on wild-type HAS1 protein 5; elevated HAS1 expression in cancer-associated fibroblasts drives ECM remodeling and oral squamous cell carcinoma invasion 6; and reduced HAS1 transcription in Alzheimer's disease, mediated by phosphorylated tau-induced nuclear translocation, contributes to perineuronal net degradation 3. Therapeutically, apigenin induces HAS1 expression in keratinocytes, enhancing skin barrier function and offering potential benefits for inflammatory skin diseases 7.