Cellular and molecular mechanisms of accelerated fracture healing by COX2 gene therapy. Studies in a mouse model of multiple fractures.

K. H.William Lau*, Vishal Kothari, Amitava Das, Xiao Bing Zhang, David J. Baylink

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

This study sought to determine the cellular and molecular mechanisms of cyclooxygenase-2 (COX2) gene therapy to accelerate fracture repair in a mouse multiple tibial fractures model. The lenti-COX2 (or lenti-gfp control vector) was injected into fractures on day 1 post-fracture. At days 3-7, the COX2 treatment increased Sdf1-, Cxcr4-, Nes-, and Podxl-expressing mesenchymal stem cells (MSCs) within fracture calluses, suggesting an enhanced MSC recruitment or expansion. The COX2-treated mice formed smaller cartilaginous calluses that had less cartilage tissues than control mice. The expression of Sox9 mRNA was 7-fold less in COX2-treated than in control calluses at day 14, implying that COX2 reduces chondrocytic differentiation of MSCs. The therapy also enhanced angiogenesis as reflected by increased immunostaining of CD31, vWF, and α-SMA over controls in the cartilaginous callus at day 14-21. At which time, the COX2 gene therapy promoted bony remodeling of the cartilaginous callus to bridge the fracture gap that was accompanied by 2-fold increase in osteoclasts along the surface of the woven bone and an onset of osteogenesis. Blocking angiogenesis with daily injection of endostatin from day 4 to day 10 into fracture sites blocked the COX2-mediated reduction of callus size that was associated with an increase in hypertrophic chondrocytes and concomitant reduction in osteoclasts. In conclusion, COX2 accelerates fracture healing in part through three biological actions: 1) increased recruitment/expansion of MSCs; 2) decreased cartilaginous callus formation; and 3) increased angiogenesis-dependent cartilage remodeling. These effects were associated with an earlier onset of bony bridging of the fracture gap.

Original languageEnglish (US)
Pages (from-to)369-381
Number of pages13
JournalBone
Volume53
Issue number2
DOIs
StatePublished - Apr 1 2013

Keywords

  • Angiogenesis
  • COX2
  • Cartilage remodeling
  • Fracture healing
  • Gene therapy
  • Mesenchymal stem cells

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Histology

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