Fig. 4.

Representative images of safranin-O staining carried out on formaldehyde-fixed sections from the femoral articular cartilage of 24-week-old rats treated with Cu in organic (Cu-Gly) and inorganic form (S-Cu) after 12 weeks of the duration of the study. a The control group (S-Cu). b 100% Cu-Gly. c 75% Cu-Gly. d 50% Cu-Gly. The cartilage from the OG50 group displayed a lower proteoglycan content (exhibiting very weak red staining), while the other rats treated with Cu-Gly demonstrated moderate to very strong red staining linked with a high content of proteoglycans. The concentration of proteoglycans exhibited a gradual increase with the distance from the periphery of the cartilage and loss of SO staining in the control rats supplemented with S-Cu. The description of the groups as in the Fig. 1. Red lines indicate the bottom border of articular cartilage whereas white arrow indicated its thickness. Magnification ×200