*2.3. The IA Administration of 7 rh Slows the Articular Cartilage Degradation*

To evaluate the efficacy of 7 rh on ACLT-induced OA progression, the loss of GAG, and the structural integrity of the articular cartilage were examined by the Safranin O-Fast Green staining and OARSI histology grading scores. As shown in Figure 3A, there was no obvious structure destruction or GAG loss identified in the sham-operated knees that were treated either with normal saline or 7 rh 13.8 nM. In contrast, we observed apparent damages to articular cartilage with a marked loss of proteoglycans in the ACLT mice at 5 weeks, indicating the successful induction of OA. The IA injection of 7 rh (6.9 nM and 13.8 nM) attenuated the cartilage degeneration and reduced the GAG loss after ACLT compared with the sham-operated knees. These results were further confirmed by the OARSI scores. The articular cartilage in the sham-operated knees did not exhibit obvious OA pathological changes in the articular cartilage and had an average OARSI score of 3.2 ± 0.9 in saline group and 3.3 ±1.0 in 7 rh 13.8 nM group (Figure 3B). The cartilage in the ACLT-OA knees exhibited significant GAG loss, cartilage erosion, and chondrocyte clustering with a mean OARSI score 9.2 ± 0.9, which was significantly higher compared to the sham-operated knees (*p* < 0.01). In contrast, the cartilage in the 7 rh-treated mice revealed a less cartilage fibrillation and proteoglycans loss and the mean OARSI scores (4 ± 0.9 in 6.9 nM of 7 rh, and 2.8 ± 1 in 13.8 nM of 7 rh) were also significantly lower compared to ACLT-OA mice (*p* < 0.01 in both concentrations).

**Figure 3.** Intra-articular injection of 7 rh attenuated cartilage degradation in anterior cruciate ligament transection (ACLT)-induced osteoarthritis (OA). (**A**) The representative Safranin O-Fast Green stained articular cartilages micrographs of the proximal tibia from the right knee joints of mice in the sham control groups (sham+ saline and sham+ 7 rh 13.8 nM), ACLT, and two 7 rh treated groups. (**B**) Osteoarthritis Research Society International (OARSI) scores of articular cartilage at 5 weeks after ACLT surgery. (\*\* *p* < 0.01 versus the sham control groups; ## *p* < 0.01 versus the ACLT group).
