title: Burn injury enhances bone formation in heterotopic ossification model.
abstract: OBJECTIVE
  To demonstrate the pro-osteogenic effect of burn injury on heterotopic bone formation using a novel burn ossicle in vivo model.
  
  
  BACKGROUND
  Heterotopic ossification (HO), or the abnormal formation of bone in soft tissue, is a troubling sequela of burn and trauma injuries. The exact mechanism by which burn injury influences bone formation is unknown. The aim of this study was to develop a mouse model to study the effect of burn injury on heterotopic bone formation. We hypothesized that burn injury would enhance early vascularization and subsequent bone formation of subcutaneously implanted mesenchymal stem cells.
  
  
  METHODS
  Mouse adipose-derived stem cells were harvested from C57/BL6 mice, transfected with a BMP-2 adenovirus, seeded on collagen scaffolds (ossicles), and implanted subcutaneously in the flank region of 8 adult mice. Burn and sham groups were created with exposure of 30% surface area on the dorsum to 60°C water or 30°C water for 18 seconds, respectively (n = 4/group). Heterotopic bone volume was analyzed in vivo by micro-computed tomography for 3 months. Histological analysis of vasculogenesis was performed with platelet endothelial cell adhesion molecule staining. Osteogenic histological analysis was performed by Safranin O, Picrosirius red, and aniline blue staining. Qualitative analysis of heterotopic bone composition was completed with ex vivo Raman spectroscopy.
  
  
  RESULTS
  Subcutaneously implanted ossicles formed heterotopic bone. Ossicles from mice with burn injuries developed significantly more bone than sham control mice, analyzed by micro-computed tomography at 1, 2, and 3 months (P < 0.05), and had enhanced early and late endochondral ossification as demonstrated by Safranin O, Picrosirius red, and aniline blue staining. In addition, burn injury enhanced vascularization of the ossicles (P < 0.05). All ossicles demonstrated chemical composition characteristic of bone as demonstrated by Raman spectroscopy.
  
  
  CONCLUSIONS
  Burn injury increases the predilection to osteogenic differentiation of ectopically implanted ossicles. Early differences in vascularity correlated with later bone development. Understanding the role of burn injury on heterotopic bone formation is an important first step toward the development of treatment strategies aimed to prevent unwanted and detrimental heterotopic bone formation.
authors.affiliation: *Department of Surgery, University of Michigan Medical School †Department of Biologic and Materials Sciences, University of Michigan School of Dentistry ‡Department of Chemistry, University of Michigan Medical School §Department of Surgery, Division of Plastic and Reconstructive Surgery, University of Michigan Medical School, Ann Arbor, MI.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Peterson
authors.forename: Sara
authors.initials: S
authors.lastname: De La Rosa
authors.forename: Hongli
authors.initials: H
authors.lastname: Sun
authors.forename: Oluwatobi
authors.initials: O
authors.lastname: Eboda
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Cilwa
authors.forename: Alexis
authors.initials: A
authors.lastname: Donneys
authors.forename: Michael
authors.initials: M
authors.lastname: Morris
authors.forename: Steven R
authors.initials: SR
authors.lastname: Buchman
authors.forename: Paul S
authors.initials: PS
authors.lastname: Cederna
authors.forename: Paul H
authors.initials: PH
authors.lastname: Krebsbach
authors.forename: Stewart C
authors.initials: SC
authors.lastname: Wang
authors.forename: Benjamin
authors.initials: B
authors.lastname: Levi
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000473:pathology; D002056:Burns / Q000150:complications* / Q000473:pathology; D002454:Cell Differentiation; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009999:Ossification, Heterotopic / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D055114:X-Ray Microtomography