Cartilage-specific deletion of ephrin-B2 in mice results in early developmental defects and an osteoarthritis-like phenotype during aging in vivo

Gladys Valverde-Franco,David Hum,Johanne Martel-Pelletier,Numa Dancause,Jean-Pierre Pelletier,Jiangping Wu,Hassan Fahmi,Adjia Hamadjida,Mohit Kapoor,Bertrand Lussier

doi:10.1186/s13075-016-0965-6

Abstract

BackgroundEphrins 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 (EFNB2Col2KO) mouse model.MethodsEFNB2Col2KO 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.ResultsEFNB2Col2KO mice exhibited significant reduction in size, weight, length, and in long bones. At P0, the growth plates of EFNB2Col2KO 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, EFNB2Col2KO mice exhibited reduced bone mineral density in the total skeleton, femur and spine. One-year-old EFNB2Col2KO mice demonstrated OA phenotypic features in both the knee and hip. By P15, 27 % of the EFNB2Col2KO mice developed a hip locomotor phenotype, which further experiments demonstrated reflected the neurological midline abnormality involving the corticospinal tract.ConclusionThis 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-0965-6) contains supplementary material, which is available to authorized users.

Highlights

Ephrins and their related receptors have been implicated in some developmental events
As both EphB4/EFNB2 are present in the growth plate [8], in vivo EphB4 enhances the process of endochondral ossification bone repair [11], and their presence and activity in adult articular chondrocytes have been demonstrated [12], we further investigated the in vivo role of EFNB2 in skeletal growth and development
Characterization of EFNB2Col2KO cartilage conditional mice The genotyping demonstrated the presence of the Cre transgene in P0 heterozygous and homozygous knockout mice and its absence in wild type mice (Fig. 1b)

Summary

Introduction

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). At P21 and 8 weeks old, EFNB2Col2KO mice exhibited reduced bone mineral density in the total skeleton, femur and spine. One-year-old EFNB2Col2KO mice demonstrated OA phenotypic features in both the knee and hip. The Eph/EFN system was first demonstrated to be essential in the development of neuronal connections, circuit plasticity and repair. Their presence and functions have been shown in many organs and tissues in which they were shown to play a role in a number of biological processes [5]. The role of EFNB2 in skeletal growth and development has never been investigated, likely due to the fact that germ-line mutation of EFNB2 in mice leads to embryonic lethality in homozygous nulls [9, 10]

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Results

Discussion

Conclusion