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Deletion of Runx1 in osteoclasts impairs murine fracture healing through progressive woven bone loss and delayed cartilage remodeling
Author(s) -
Paglia David N.,
DiazHernandez Martha E.,
Roberts Joseph L.,
Kalinowski Judy,
Lorenzo Joseph,
Drissi Hicham
Publication year - 2020
Publication title -
journal of orthopaedic research®
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.24537
Subject(s) - osteoclast , runx1 , bone resorption , cartilage , bone healing , resorption , bone remodeling , callus , endocrinology , medicine , chemistry , anatomy , microbiology and biotechnology , biology , stem cell , haematopoiesis , genetics , receptor
Conditional deletion of the transcription factor Runt‐related transcription factor 1 ( Runx1 ) in myeloid osteoclast precursors promotes osteoclastogenesis and subsequent bone loss. This study posits whether Runx1 regulates clastic cell‐mediated bone and cartilage resorption in the fracture callus. We first generated mice, in which Runx1 was conditionally abrogated in osteoclast precursors ( LysM ‐ Cre ; Runx1 F/F ; Runx1 cKO). Runx1 cKO and control mice were then subjected to experimental mid‐diaphyseal femoral fractures. Our study found differential resorption of bony and calcified cartilage callus matrix by osteoclasts and chondroclasts within Runx1 cKO calluses, with increased early bony callus resorption and delayed calcified cartilage resorption. There was an increased number of osteoclasts and chondroclasts in the chondro‐osseous junction of Runx1 cKO calluses starting at day 11 post‐fracture, with minimal woven bone occupying the callus at day 18 post‐fracture. LysM ‐ Cre ; Runx1 F/F mutant mice had increased bone compliance at day 28, but their strength and work to failure were comparable with controls. Taken together, these results indicate that Runx1 is a critical transcription factor in controlling osteoclastogenesis that negatively regulates bone and cartilage resorption in the fracture callus. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:1007‐1015, 2020