Bo Wei1, Fengyong Mao1, Yang Guo1, Qingqiang Yao1, Cheng Tang1, Yan Xu1, Chengzhe Jin1, Fengchao Zang2, Shaoxiang Zhang3, Liming Wang4. 1. Department of Orthopaedics, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, China; Cartilage Regeneration Center, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, China. 2. Department of Radiology, Jiangsu Key Laboratory of Molecule Imaging and Functional Imaging, Zhong Da Hospital, Medical School of Southeast University, Nanjing, Jiangsu, China. 3. Institute of Computing Medicine, Third Military Medical University, Chongqing, China. Electronic address: zhangsx1021@yahoo.com. 4. Department of Orthopaedics, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, China; Cartilage Regeneration Center, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, China. Electronic address: limingwang99@hotmail.com.
Abstract
OBJECTIVE: The goal of this study was to detect early changes in the cartilage matrix caused by immobilization in a rabbit model of immobilization-induced osteoarthritis (OA) by T2 mapping with 7.0T MRI. MATERIALS AND METHODS: Left knee joints of 28 mature rabbits were immobilized at 180° of extension with orthopedic casting tape for 1, 2, or 3weeks (n=7 rabbits each). No immobilization was performed in the control group (n=7 rabbits). T2 mapping was performed after 1, 2, and 3weeks. Osteochondral specimens harvested from the trochlea groove (TG) and medial femoral condyle (MFC) were subjected to histologic, immunohistochemical, and microscopic evaluation, followed by biochemical assays for water, glycosaminoglycan (GAG), and collagen. The ability of T2 mapping to reveal changes in the cartilage matrix was further assessed. RESULTS: Rabbits demonstrated elevated T2 values (9.9% in TG, 10.6% in MFC), a dulled cartilage surface, reduced Safranin-O staining, and decreased GAG content (14.2% in TG and MFC) after 2weeks, with cartilage surface softening, irregularity, and markedly reduced GAG content by 3weeks. T2 values were correlated positively with water (r=0.836 in TG, r=0.821 in MFC) and negatively with GAG content (r=-0.945 in TG, r=-0.957 in MFC), but had no discernible relationship with collagen content (r=-0.196 in TG, r=-0.213 in MFC). CONCLUSIONS: 7.0T MRI T2 mapping can be used to detect early changes of the cartilage matrix caused by immobilization in an immobilization-induced OA model.
OBJECTIVE: The goal of this study was to detect early changes in the cartilage matrix caused by immobilization in a rabbit model of immobilization-induced osteoarthritis (OA) by T2 mapping with 7.0T MRI. MATERIALS AND METHODS: Left knee joints of 28 mature rabbits were immobilized at 180° of extension with orthopedic casting tape for 1, 2, or 3weeks (n=7 rabbits each). No immobilization was performed in the control group (n=7 rabbits). T2 mapping was performed after 1, 2, and 3weeks. Osteochondral specimens harvested from the trochlea groove (TG) and medial femoral condyle (MFC) were subjected to histologic, immunohistochemical, and microscopic evaluation, followed by biochemical assays for water, glycosaminoglycan (GAG), and collagen. The ability of T2 mapping to reveal changes in the cartilage matrix was further assessed. RESULTS:Rabbits demonstrated elevated T2 values (9.9% in TG, 10.6% in MFC), a dulled cartilage surface, reduced Safranin-O staining, and decreased GAG content (14.2% in TG and MFC) after 2weeks, with cartilage surface softening, irregularity, and markedly reduced GAG content by 3weeks. T2 values were correlated positively with water (r=0.836 in TG, r=0.821 in MFC) and negatively with GAG content (r=-0.945 in TG, r=-0.957 in MFC), but had no discernible relationship with collagen content (r=-0.196 in TG, r=-0.213 in MFC). CONCLUSIONS: 7.0T MRI T2 mapping can be used to detect early changes of the cartilage matrix caused by immobilization in an immobilization-induced OA model.