Figure 4. Wnt7a reduces joint MMP activity during OA development, but has no effect on subchondral bone.

(a) Representative images of Collagen II IHC analysis 5 or 7 weeks post DMM surgery in mouse knees injected with lenti-GFP or lenti-Wnt7a-GFP. Quantification analysis based on total Collagen II fluorescence of the femur and tibia from at least 4 sections/treatment indicated there were no significant differences among groups. (b) Representative images and semi-quantitative analysis of picrosirius red staining showing collagen fiber thickness and organization of articular cartilage from knee joints at 5 or 7 weeks post DMM surgery, as viewed under polarized light. Areas used for subsequent quantification of birefringence signals are delineated by dashed lines. (c) Representative in vivo near infrared fluorescence (NIRF) images taken two hours after 4 μL intraarticular injection of MMPSense680 in each knee. Each lenti-GFP and lenti-Wnt7a-GFP-infected mouse was imaged serially at 5 and 7 weeks post surgery. The average radiance efficiency emitted from each knee was quantified from the collected NIRF images and the DMM average radiance efficiency was divided by the sham average radiance efficiency to internally calibrate each signal. Quantification analysis demonstrated that mice ectopically expressing Wnt7a in the joint have reduced NIRF signals compared to lenti-GFP controls. (d) Representative histological images of osteophyte development with safraninO/hematoxylin staining and scoring of osteophyte maturity at 5 or 7 weeks post DMM surgery in mouse knees injected with lenti-GFP or lenti-Wnt7a-GFP. Arrows indicate osteophytes. Osteophyte maturity was quantified. (e) Representative micro-CT cross-sections of the knee joint and quantification of medial and lateral tibial subchondral bone plate thickness at 7 weeks post DMM surgery in mouse knees injected with lenti-GFP or lenti-Wnt7a-GFP. Micro-CT quantification demonstrated no differences between the lenti-GFP and lenti-Wnt7a-GFP groups. n = 7 mice/group for NIRF imaging and 6 mice/group for microCT imaging and histology. A student’s t-test was used for evaluating the statistical significance between GFP and Wnt7a mice at each individual time point. All data are shown as mean ± SEM. *p < 0.05.