Quantitative analysis of the degree of inflammatory lesions in rabbit rheumatoid arthritis model by contrast-enhanced ultrasound

Objective To quantitatively analyze the degree of inflammatory lesions in rabbit rheumatoid arthritis models using contrast-enhanced ultrasonography. Methods Total 32 rabbits, purchased from the Animal Experiment Center of Bengbu Medical College, were randomly divided into model group and control group according to the random number table, 16 cases in each group. The model group were induced by injecting ovalbumin into the knee joint cavity. Conventional ultrasound examination and contrast-enhanced ultrasonography were performed at 4 weeks after the last injection. The experimental rabbits were euthanized after the ultrasound examination, and synovium specimens were harvested for histological staining of haematoxylin-eosin to calculate the pathological synovitis score, and for histological staining of CD31 to obtain the density of neovascularization. Pearson correlation was used to assess the association between enhancement intensity and synovitis pathological score, and histological neovascularization density. Results The maximum thickness of knee synovium in the model group was significantly greater than that of the control group [(3.53±0.49) mm vs.(0.89±0.15) mm, P<0.001]. The synovium of the model group was significantly enhanced [(12.06±2.40) dB], while the synovium of the control group was not enhanced. The pathological synovitis score in the model group was [(5.19±1.47) points], and the density of synovial neovascularization was [(23.00±4.05) microvessels per 200 × magnification microscopic field]. There were good correlation between contrast-enhanced ultrasound intensity and synovitis pathological score(r=0.758, P=0.001) and synovial neovascularization density(r=0.761, P=0.001). There was a certain correlation between the maximum thickness of knee joint synovium and pathological score of synovitis in model group(r=0.513, P=0.042). Conclusion The contrast-enhanced ultrasonography can not only quantitatively evaluate the neovascularization of rheumatoid arthritis synovium, but also sensitively and effectively evaluate the degree of synovial inflammatory lesions.