Early Characterization of Blast-related Heterotopic Ossification in a Rat Model

Ammar T. Qureshi, Erica K. Crump, Gabriel J. Pavey, Donald N. Hope, Jonathan A. Forsberg, Thomas A. Davis

Research output: Contribution to journalArticle

Abstract

Background: Heterotopic ossification (HO) affects the majority of combat-related lower extremity wounds involving severe fracture and amputation. Defining the timing of early osteogenic-related genes may help identify candidate prophylactic agents and guide the timing of prophylactic therapy after blast and other combat-related extremity injuries. Questions/purposes: Using a recently developed animal model of combat-related HO, we sought to determine (1) the timing of early chondrogenesis, cartilage formation, and radiographic ectopic bone development; and (2) the early cartilage and bone-related gene and protein patterns in traumatized soft tissue. Methods: We used an established rat HO model consisting of blast exposure, controlled femur fracture, crush injury, and transfemoral amputation through the zone of injury. Postoperatively, rats were euthanized on Days 3 to 28. We assessed evidence of early ectopic bone formation by micro-CT and histology and performed proteomic and gene expression analysis. Results: All rats showed radiographic evidence of HO within 28 days. Key chondrogenic (collagen type I alpha 1 [COL1α1], p = 0.016) and osteogenic-related genes (Runt-related transcription factor 2 [RUNX-2], p = 0.029; osteoclacin [OCN], p = 0.032; phosphate-regulating neutral endopeptidase, X-linked [PHEX], p = 0.0290, and POU domain class 5 transcription factor [POU5F], p = 0.016) and proteins (Noggin [NOG], p = 0.04, OCN, p = 0.02, RUNX- 2, p = 0.04, and substance P-1 [SP-1], p = 0.01) in the injured soft tissue, normalized to the contralateral limb and/or sham-treated naïve rats, increased on Days 3 to 14 postinjury. By 14 days, foci of hypertrophic chondrocytes, hyaline cartilage, and woven bone were present in the soft tissue surrounding the amputation site. Conclusions: We found that genes that regulate early chondrogenic and osteogenic signaling and bone development (COL1α1, RUNX-2, OCN, PHEX, and POU5F1) are induced early during the tissue reparative/healing phase in a rat model simulating a combat-related extremity injury. Clinical Relevance: The ability to correlate molecular events with histologic and morphologic changes will assist researchers and clinicians to understand HO and hence formulate therapeutic interventions.

Original languageEnglish (US)
Pages (from-to)2831-2839
Number of pages9
JournalClinical orthopaedics and related research
Volume473
Issue number9
DOIs
StatePublished - Sep 5 2015

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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    Qureshi, A. T., Crump, E. K., Pavey, G. J., Hope, D. N., Forsberg, J. A., & Davis, T. A. (2015). Early Characterization of Blast-related Heterotopic Ossification in a Rat Model. Clinical orthopaedics and related research, 473(9), 2831-2839. https://doi.org/10.1007/s11999-015-4240-y