title: Injectable tissue-engineered bone repair of a rat calvarial defect.
abstract: OBJECTIVE
  Advances in bone repair have focused on the minimally-invasive delivery of tissue-engineered bone (TEB). A promising injectable biopolymer of chitosan and inorganic phosphates was seeded with mesenchymal stem cells (MSCs) and a bone growth factor (BMP-2), and evaluated in a rat calvarial critical size defect (CSD). Green fluorescent protein (GFP)-labeled MSCs are used to evaluate patterns of cell viability and proliferation.
  
  
  METHODS
  Prospective, controlled trial in an animal model.
  
  
  METHODS
  In 30 male rats, 8-mm calvarial CSDs were created, and divided into five groups of six animals each. In the experimental groups, the defects were injected with either chitosan gel, gel loaded with MSCs (0.3 x 10(6) cells/defect), gel loaded with BMP-2 (2 microg/defect), or gel loaded with both MSC and BMP-2. In the control group, the defect was left untreated. At 4 weeks, in vivo microcomputed tomography (micro-CT) analysis was performed. At 8 weeks, calvarial specimens were examined by micro-CT, histology, and immunohistochemistry.
  
  
  RESULTS
  New areas of bone growth were seen in the defects of all treated animals. Micro-CT analysis revealed a significant (P < .001) time-dependent increase in the regeneration of bone volume and bone area in defects treated with gel/MSC/BMP-2 as compared to all other groups. Histological analysis confirmed this difference. GFP-labeled TEB was detected within the areas of new bone, indicating cell viability and contribution to new bone growth by the injected MSC.
  
  
  CONCLUSIONS
  This study demonstrates that an injectable form of TEB using a chitosan gel, MSC, and BMP-2 can enhance bone formation in a rat calvarial CSD.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, University of Virginia, PO Box 800713, Charlottesville, VA 22908, USA. scott.stephan@virginia.edu
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Stephan
authors.forename: Sunil S
authors.initials: SS
authors.lastname: Tholpady
authors.forename: Brian
authors.initials: B
authors.lastname: Gross
authors.forename: Caren E
authors.initials: CE
authors.lastname: Petrie-Aronin
authors.forename: Edward A
authors.initials: EA
authors.lastname: Botchway
authors.forename: Lakshmi S
authors.initials: LS
authors.lastname: Nair
authors.forename: Roy C
authors.initials: RC
authors.lastname: Ogle
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Park
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage*; D001861:Bone Regeneration / Q000502:physiology; D048271:Chitosan; D005782:Gels; D007091:Image Processing, Computer-Assisted; D007267:Injections; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods*; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D010710:Phosphates; D051381:Rats; D017207:Rats, Sprague-Dawley; D019651:Plastic Surgery Procedures / Q000379:methods*; D012886:Skull / Q000473:pathology / Q000601:surgery*; D023822:Tissue Engineering / Q000379:methods*; D055114:X-Ray Microtomography
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D005782:Gels; D010710:Phosphates; D048271:Chitosan