Conditional knockout of ephrinB1 in osteogenic progenitors delays the process of endochondral ossification during fracture repair

Arthur, Agnieszka; Paton, Sharon; Zannettino, Andrew C. W.; Gronthos, Stan

Affiliations

¹Mesenchymal Stem Cell Laboratory, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia

²Cancer Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia

³Myeloma Research Laboratory, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia

Abstract and keywords

The Eph receptor tyrosine kinase ligand, ephrinB1 (EfnB1) is important for correct skeletal and cartilage development, however, the role of EfnB1 in fracture repair is unknown. This study investigated the role of EfnB1 during fracture repair where EfnB1 expression increased significantly at 1 and 2 weeks post fracture in C57Bl/6 wildtype mice, coinciding with the haematoma, soft callus formation/remodelling stages, respectively. To investigate the specific role of EfnB1 within the osteogenic lineage during fracture repair, male mice with a conditional deletion of EfnB1 in the osteogenic lineage (EfnB1_OB^fl/O), driven by the Osterix (Osx) promoter, and their male Osx:Cre counterparts were subject to a femoral fracture with internal fixation. Two weeks post fracture micro computed tomography (μCT) analysis revealed that EfnB1_OB^fl/O mice displayed a significant decrease in bone volume relative to tissue volume within the fracture callus. This was attributed to an alteration in the distribution of osteoclasts within the fracture site, a significant elevation in cartilaginous tissue and reduction in the osteoprogenitor population and calcein labelled bone within the fracture site of EfnB1_OB^fl/O mice. Supportive in vitro studies demonstrated that under osteogenic conditions, cultured EfnB1_OB^fl/O stromal cells derived from the 2 week fracture site exhibited a reduced capacity to produce mineral and decreased expression of the osteogenic gene, Osterix, when compared to Osx:Cre controls. These findings suggest that the loss of EfnB1 delays the fracture repair process. The present study confirmed that EFNB1 activation in human BMSC, following stimulation with soluble-EphB2 resulted in de-phosphorylation of TAZ, demonstrating similarities in EfnB1 signalling between human and mouse stromal populations. Overall, the present study provides evidence that loss of EfnB1 in the osteo/chondrogenic lineages delays the soft callus formation/remodelling stages of the fracture repair process.

Keywords: Eph/ephrin receptor tyrosine kinases; Bone remodelling; Fracture repair; Osteoblasts; Osteoclasts

Links

DOI: 10.1016/j.bone.2019.115189

PubMed: 31863961

WoS: 000510529200019

History

Received: 2019-08-26

Revised: 2019-11-29

Accepted: 2019-12-11

Online: 2019-12-19

Cited Works (5)

Year	Entry
2015	Einhorn TA, Gerstenfeld LC. Fracture healing: mechanisms and interventions. Nat Rev Rheumatol. 2015;11(1):45-54.
2006	Rodda SJ, McMahon AP. Distinct roles for Hedgehog and canonical Wnt signaling in specification, differentiation and maintenance of osteoblast progenitors. Development. August 15, 2006;133(16):3231-3244.
2002	Nakashima K, Zhou X, Kunkel G, Zhang Z, Deng JM, Behringer RR, de Crombrugghe B. The novel zinc finger-containing transcription factor osterix is required for osteoblast differentiation and bone formation. Cell. January 11, 2002;108(1):17-29.
2006	Zhao C, Irie N, Takada Y, Shimoda K, Miyamoto T, Nishiwaki T, Suda T, Matsuo K. Bidirectional ephrinB2-EphB4 signaling controls bone homeostasis. Cell Metab. August 2006;4(2):111-121.
2008	Schindeler A, McDonald MM, Bokko P, Little DG. Bone remodeling during fracture repair: the cellular picture. Semin Cell Dev Biol. October 2008;19(5):459-466.

Cited By (1)

Year	Entry
2021	Abeynayake N, Arthur A, Gronthos S. Crosstalk between skeletal and neural tissues is critical for skeletal health. Bone. January 2021;142:115645.