Valverde-Franco Gladys, Lussier Bertrand, Hum David, Wu Jiangping, Hamadjida Adjia, Dancause Numa, Fahmi Hassan, Kapoor Mohit, Pelletier Jean-Pierre, Martel-Pelletier Johanne
Osteoarthritis Research Unit, University of Montreal Hospital Research Centre (CRCHUM), 900 Saint-Denis, R11.412B, Montreal, QC, H2X 0A9, Canada.
Faculty of Veterinary Medicine, Clinical Science, University of Montreal, Saint-Hyacinthe, QC, Canada.
Arthritis Res Ther. 2016 Mar 15;18:65. doi: 10.1186/s13075-016-0965-6.
Ephrins and their related receptors have been implicated in some developmental events. We have demonstrated that ephrin-B2 (EFNB2) could play a role in knee joint pathology associated with osteoarthritis (OA). Here, we delineate the in vivo role of EFNB2 in musculoskeletal growth, development, and in OA using a cartilage-specific EFNB2 knockout (EFNB2(Col2)KO) mouse model.
EFNB2(Col2)KO was generated with Col2a1-Cre transgenic mice. The skeletal development was evaluated using macroscopy, immunohistochemistry, histomorphometry, radiology, densitometry, and micro-computed tomography. Analyses were performed at P0 (birth) and on postnatal days P15, P21, and on 8-week- and 1-year-old mice.
EFNB2(Col2)KO mice exhibited significant reduction in size, weight, length, and in long bones. At P0, the growth plates of EFNB2(Col2)KO mice displayed increased type X collagen, disorganized hyphertrophic zone, and decreased mineralization. At P15, mutant mice demonstrated a significant reduction in VEGF and TRAP at the chondro-osseous junction and a delay in the secondary ossification, including a decrease in bone volume and trabecular thickness. At P21 and 8 weeks old, EFNB2(Col2)KO mice exhibited reduced bone mineral density in the total skeleton, femur and spine. One-year-old EFNB2(Col2)KO mice demonstrated OA phenotypic features in both the knee and hip. By P15, 27 % of the EFNB2(Col2)KO mice developed a hip locomotor phenotype, which further experiments demonstrated reflected the neurological midline abnormality involving the corticospinal tract.
This in vivo study demonstrated, for the first time, that EFNB2 is essential for normal long bone growth and development and its absence leads to a knee and hip OA phenotype in aged mice.
Ephrins及其相关受体参与了一些发育过程。我们已经证明，ephrin-B2（EFNB2）可能在与骨关节炎（OA）相关的膝关节病理中发挥作用。在此，我们使用软骨特异性EFNB2基因敲除（EFNB2(Col2)KO）小鼠模型来描述EFNB2在肌肉骨骼生长、发育以及骨关节炎中的体内作用。
利用Col2a1-Cre转基因小鼠构建EFNB2(Col2)KO模型。通过大体观察、免疫组织化学、组织形态计量学、放射学、骨密度测定和微计算机断层扫描评估骨骼发育。在出生后第0天（出生时）、出生后第15天、第21天以及8周龄和1岁小鼠时进行分析。
EFNB2(Col2)KO小鼠的体型、体重、长度和长骨均显著减小。在出生后第0天，EFNB2(Col2)KO小鼠的生长板显示X型胶原蛋白增加、肥大带紊乱以及矿化减少。在出生后第15天，突变小鼠在软骨-骨交界处的VEGF和TRAP显著减少，次级骨化延迟，包括骨体积和小梁厚度减小。在出生后第21天和8周龄时，EFNB2(Col2)KO小鼠的全身骨骼、股骨和脊柱的骨密度降低。1岁的EFNB2(Col2)KO小鼠在膝关节和髋关节均表现出骨关节炎的表型特征。到出生后第15天，27%的EFNB2(Col2)KO小鼠出现髋关节运动表型，进一步实验表明这反映了涉及皮质脊髓束的神经中线异常。
这项体内研究首次证明，EFNB2对正常长骨生长发育至关重要，缺乏EFNB2会导致老年小鼠出现膝关节和髋关节骨关节炎表型。
