ObjectiveTo determine the effect of hyaluronic acid (HA) degradation by hyaluronidase (HYAL) in inhibiting collagen fiber production by rat periodontal ligament cells (rPDLCs). DesignPrimary rPDLCs were isolated from the euthanized rats and used for in vitro experiments. The appropriate HYAL concentration was determined through CCK-8 testing for cytotoxicity detection and Alizarin red staining for mineralization detection. RT-qPCR and western blot assays were conducted to assess the effect of HYAL, with or without TGF-β, on generation of collagen fiber constituents and expression of actin alpha 2, smooth muscle (ACTA2) of rPDLCs. ResultsNeither cell proliferation nor mineralization were significantly affected by treatment with 4 U/mL HYAL. HYAL (4 U/mL) alone downregulated type I collagen fiber (Col1a1 and Col1a2) and Acta2 mRNA expression; however, ACTA2 and COL1 protein levels were only downregulated by HYAL treatment after TGF-β induction. ConclusionsTreatment of rPDLCs with HYAL can inhibit TGF-β-induced collagen matrix formation and myofibroblast transformation.