Figure 4. α-Klotho expression is reduced in osteoarthrosis models. (A) ACAN, secreted α-KL, SLC39A8 and MMP13 mRNA expression analysis by RT-qPCR of human chondrocytes incubated or not with IL-1β for 10 days. (B) Secreted α-KL and MMP13 expression levels in human OA (n=4) versus healthy cartilage (n=4). (C) α-Klotho expression by immunostaining (bottom panel) in joint knee cartilage at day 43 after intra-articular injection of PBS (n=5 mice) or collagenase (contralateral knee). Top panels show Safranin-O Fast-Green (SOFG) staining of the same joints. (C) OARSI scoring of cartilage degradation and (D) quantification of α-Klotho-positive chondrocytes in joints at day 43 after intra-articular injection of PBS or collagenase. Data are represented as mean -/+ SEM. *=p<0.05; **=p<0.01.