Figure 4.

Histological findings in synovial tissue and articular cartilage: haematoxylin and eosin (HE) staining (a, c, e, g, and h) for acute inflammation (arrowheads), chronic inflammation (*), and cartilage damage (arrows), as well as Safranin O staining (b, d, and f) for proteoglycan depletion (arrows). Images are shown for non-arthritic rats (a and b), untreated antigen-induced arthritis (AIA) rats (day 8, c and d; day 29, g), and hyaluronic acid hyaluronic acid (HA)-treated AIA rats (day 8, e and f; day 29, h). The bar indicates the distance in the histological section. SM, synovial membrane; P, patella; FE, femur. Safranin O staining: S, superficial layer; M, middle layer; D, deep layer; and C, calcified cartilage. N, non-arthritic rats; US, untreated AIA, short-term test; HS, HA-treated AIA, short-term test; UL, untreated AIA, long-term test; HL, HA-treated AIA, long-term test.