Figure 1.

Exogenous hyaluronic acid (HA) promotes extracellular matrix (ECM) metabolism under hypoxic conditions. Rat articular cartilage was cultured in the presence of 4000 µg/mL HA for 72 h under hypoxia (1% oxygen). The expression of type II collagen and aggrecan mRNA was analyzed using real-time reverse transcription-polymerase chain reaction (RT-PCR) (A,B); and HA-binding protein 2 (HABP2) protein expression was analyzed by Western blotting (C,D); β-actin protein were used as loading controls. The total amount of glycosaminoglycans (GAG) in each sample was quantified using the dimethylmethylene blue (DMMB) assay (E); The DNA level was measured, and total GAG accumulation was normalized relative to DNA level (F,G). * p < 0.05.