Longitudinal analysis of osteogenic and angiogenic signaling factors in healing models mimicking atrophic and hypertrophic non-unions in rats

PLoS One. 2015 Apr 24;10(4):e0124217. doi: 10.1371/journal.pone.0124217. eCollection 2015.

Abstract

Impaired bone healing can have devastating consequences for the patient. Clinically relevant animal models are necessary to understand the pathology of impaired bone healing. In this study, two impaired healing models, a hypertrophic and an atrophic non-union, were compared to physiological bone healing in rats. The aim was to provide detailed information about differences in gene expression, vascularization and histology during the healing process. The change from a closed fracture (healing control group) to an open osteotomy (hypertrophy group) led to prolonged healing with reduced mineralized bridging after 42 days. RT-PCR data revealed higher gene expression of most tested osteogenic and angiogenic factors in the hypertrophy group at day 14. After 42 days a significant reduction of gene expression was seen for Bmp4 and Bambi in this group. The inhibition of angiogenesis by Fumagillin (atrophy group) decreased the formation of new blood vessels and led to a non-healing situation with diminished chondrogenesis. RT-PCR results showed an attempt towards overcoming the early perturbance by significant up regulation of the angiogenic regulators Vegfa, Angiopoietin 2 and Fgf1 at day 7 and a further continuous increase of Fgf1, -2 and Angiopoietin 2 over time. However µCT angiograms showed incomplete recovery after 42 days. Furthermore, lower expression values were detected for the Bmps at day 14 and 21. The Bmp antagonists Dan and Twsg1 tended to be higher expressed in the atrophy group at day 42. In conclusion, the investigated animal models are suitable models to mimic human fracture healing complications and can be used for longitudinal studies. Analyzing osteogenic and angiogenic signaling patterns, clear changes in expression were identified between these three healing models, revealing the importance of a coordinated interplay of different factors to allow successful bone healing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atrophy / diagnostic imaging
  • Atrophy / genetics
  • Atrophy / metabolism*
  • Atrophy / pathology*
  • Bone Morphogenetic Proteins / genetics
  • Bone Morphogenetic Proteins / metabolism
  • Disease Models, Animal
  • Female
  • Fracture Healing*
  • Gene Expression
  • Hypertrophy / diagnostic imaging
  • Hypertrophy / genetics
  • Hypertrophy / metabolism*
  • Hypertrophy / pathology*
  • Neovascularization, Pathologic*
  • Osteogenesis*
  • Rats
  • Signal Transduction*
  • X-Ray Microtomography

Substances

  • Bone Morphogenetic Proteins

Grants and funding

This study was supported by the Oskar-Helene-Heim foundation (Oskar-Helene Medizinpreis 2011) and the Elsa- Neumann foundation, and partially by the Bundesministerium für Bildung und Forschung (BMBF, FKZ 1315848A) and the Berlin-Brandenburg Center for Regenerative Therapies (BCRT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.