Synovitis is a driver of osteoarthritis. Imaging of the synovial vasculature is essential for osteoarthritis assessment, while traditional imaging techniques like contrast-enhanced MRI/CT and conventional ultrasonography have limitations such as invasive manipulation, radiation and subjective results. In this study, an emerging non-invasive ultrasound imaging technique – optoacoustic molecular imaging (OA) was applied to evaluate the synovial vasculature in a mouse model of knee joint osteoarthritis. 16 male Balb/c mice undertook destabilization of medial meniscus surgery (DMM), 8 were intact as baseline controls. Three-dimensional high-frequency ultrasonography, including B mode, Power Doppler (PD) and OA, was performed to the knees of live mice at baseline (n=8), 1 month (n=8), and 4 months (n=7) after DMM, before tissue harvest. We found that OA vascular density increased significantly at 1 month (p=0.028) and remained high at 4 months (p=0.541), indicating synovial neovascularization during osteoarthritis progression, which was consistent with uCT-based angiography and histological findings. Meanwhile, OA could also evaluate the function of the synovial vasculature by measuring blood oxygen saturation (sO2). We found OA sO2 declined significantly at 4 months compared to baseline (p=0.043) and 1 month (p=0.027), indicating vascular dysfunction at late stage osteoarthritis. Moreover, OA sO2 was found closely related with histological cartilage damage (p=0.028). In this study, we demonstrated that OA was reliable to evaluate the small vasculatures in the knee joint of DMM mouse model. Our findings provided a new technique for the non-invasive monitoring of both structure and function of the synovial vasculature during osteoarthritis progression.
Zhongyu LIU, Xuan Wang, Manting Au, Duojia Li, Yongping Zheng, Chunxiao Luo, Limin Rong, and Chunyi Wen, "In-vivo three-dimensional optoacoustic molecular imaging of the synovial vasculature in a mouse model of knee joint osteoarthritis (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 104940L (Presented at SPIE BiOS: January 28, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2299658.5752212560001.
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