## 3 Results
### hUC-MSCs-HA Combinatorial Treatment Reduced Cartilage Damage in KOA Rats  
To investigate the therapeutic effects of the hUC-MSCs and HA treatments in KOA, we established MIA-induced KOA rat models as shown in Figure 5A. Briefly, eight-week-old male Wistar rats were injected with MIA to induce cartilage damage. A knee edema was observed on the right-hand knee of each rat after MIA injection, which indicated that an inflammatory response had occurred within the affected joint. At week 3, randomly divided rats were treated with a single dose of HA, hUC-MSCs, hUC-MSCs combined with HA or 0.9% normal saline (vehicle control). For the hUC-MSC treatments, a dose level of  
Figure 4: HA enhanced the antioxidant capacity of hUC-MSCs on human chondrocyte cells. Human chondrocyte cells were damaged by 200-\(\mu\)M H\({}_{2}\)O\({}_{2}\) for 4 h and replaced with MEM\(\alpha\)-only as the control, MSC-CM-only, 0–0.2% HA-only or MSC-CM (mesenchymal stem cell conditioned medium) with 0–0.2% HA for 48 h. Cell viability was analyzed by CCK-8 and normalized to the control and calculated as a fold of relative cell recovery. **_p_ < 0.01 compared with the control, and #_p_ < 0.05 compared with the 0.1% or 0.2% HA-only groups, respectively. $_p_ < 0.05 compared with the MSC-CM-only group. Data shown as the mean \(\pm\) S.D of five independent experiments.  
2.5 \(\times\) 10\({}^{6}\) cells/knee joint was used in this study. All rats were sacrificed at 16 weeks after treatment, and the knee joints were processed for a histological analysis and OARSI scoring.  
Figure 5: Effects of different treatments on MIA-induced cartilage damage. (**A**) Experimental design of mono-iodoacetate (MIA)-induced osteoarthritis rats. (**B**) Hematoxylin and eosin (H&E) staining of the cartilage of rats 16 weeks after treatment. Representative articular pathology image of the vehicle control, HA, hUC-MSCs, and hUC-MSCs combined with HA groups at 10\(\times\), 40\(\times\) and 100\(\times\) amplification. AC, articular cartilage; CB, cancellous bone; CC, calcified cartilage; F, femur; M, meniscus; S, synovial membrane; SB, subchondral bone and T, tibial. (**C**) Comparison of the OARSI scores in different treatment groups. Data are presented as the mean \(\pm\) SD. * \(p\) < 0.05, ** \(p\) < 0.01 and *** \(p\) < 0.0001 comparisons by groups using one-way ANOVA.  
As shown in Figure 5B, H&E staining revealed cartilage damage and structural degradation in the vehicle group. The cartilage tissue was denuded and broken down to shatter and almost eroded into subchondral bone (SB). These results together suggested that an injection of MIA successfully induced OA. In contrast, the hUC-MSC and HA treatments respectively reduced the cartilage damage significantly caused by MIA. In the hUC-MSC-HA combinatorial treatment, the degree of cartilage damage was significantly reduced, where the superficial and mid and deep zones were not damaged compared to the vehicle control, hUC-MSC-alone and the HA-alone groups.  
The OARSI scoring system, with a scale ranging from 0 (normal architecture) to 24 (over 50% joint involvement with deformation), was used to evaluate the extent of MIA-induced articular cartilage degeneration in this study.  
The highest degree of cartilage damage was evident in the vehicle group, with a mean OARSI score of 12.14 \(\pm\) 2.04, which was significantly decreased when compared to the hUC-MSC-only group (7.14 \(\pm\) 2.97), HA-only group (9.50 \(\pm\) 2.26) and hUC-MSC + HA group (4.43 \(\pm\) 1.81). It was noted that the hUC-MSC + HA group reduced the articular cartilage degeneration, which, induced by MIA, was superior to the hUC-MSC- or HA-only groups (Figure 5C). Taken together, our results suggested that all the treatment groups successfully attenuated the articular cartilage damage induced by MIA, whereas the combination of hUC-MSCs and HA exhibited the highest potential therapeutic benefits in the MIA-induced knee OA animal model.