title: Bone tissue engineering by way of allograft revitalization: mechanistic and mechanical investigations using a porcine model.
abstract: OBJECTIVE
  "Allograft revitalization" is a process in which cadaveric bone is used to generate well-vascularized living bone. We had previously found that porcine allograft hemimandibles filled with autologous adipose-derived stem cells (ASCs) and recombinant human bone morphogenetic protein-2-soaked absorbable collagen sponge (rhBMP-2/ACS) were completely replaced by vascularized bone, provided the construct had been incubated within a periosteal envelope. The present study sought to deepen our understanding of allograft revitalization by investigating the individual contributions of ASCs and rhBMP-2 in the process and the mechanical properties of the revitalized allograft.
  
  
  METHODS
  Porcine allograft hemimandible constructs were implanted bilaterally into rib periosteal envelopes in 8 pigs. To examine the contributions of ASCs and rhBMP-2, the following groups were assessed: group 1, periosteum alone; group 2, periosteum+ASCs; group 3, periosteum+rhBMP-2/ACS; and group 4, periosteum+ASCs+rhBMP-2/ACS. After 8 weeks, the allograft constructs were harvested for micro-computed tomography (CT) and histologic analyses and 3-point bending to assess the strength.
  
  
  RESULTS
  On harvesting, the constructs receiving rhBMP-2/ACS had significantly greater bone shown by micro-CT than those receiving periosteum only (51,463 vs. 34,310 mm3; P = .031). The constructs receiving ASCs had increased bone compared to group 1 (periosteum only), although not significantly (P = .087). The combination of rhBMP-2/ACS with ASCs produced bone (50,399 mm3) equivalent to that of the constructs containing rhBMP-2/ACS only. The 3-point bending tests showed no differences between the 4 groups and a nonimplanted allograft or native mandible (P = .586), suggesting the absence of decreased strength of the allograft bone when revitalized.
  
  
  CONCLUSIONS
  These data have shown that rhBMP-2/ACS significantly stimulates new bone formation by way of allograft revitalization and that the revitalized allograft has equivalent mechanical strength to native bone.
authors.affiliation: Resident, Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Runyan
authors.affiliation: Medical Student, Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
authors.forename: Samantha T
authors.initials: ST
authors.lastname: Ali
authors.affiliation: Resident, Department of Plastic Surgery, University of Pittsburgh, Pittsburgh, PA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Chen
authors.affiliation: Resident, Department of Surgery, Medical University of South Carolina, Charleston, SC.
authors.forename: Bennet W
authors.initials: BW
authors.lastname: Calder
authors.affiliation: Medical Student, Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
authors.forename: Aaron E
authors.initials: AE
authors.lastname: Rumburg
authors.affiliation: Attending Surgeon, Division of Plastic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OH.
authors.forename: David A
authors.initials: DA
authors.lastname: Billmire
authors.affiliation: Attending Surgeon, Division of Plastic Surgery, Children's Hospital of Philadelphia, Philadelphia, PA. Electronic address: Taylorj5@email.chop.edu.
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Taylor
mesh_terms: D020341:Absorbable Implants; D000273:Adipose Tissue / Q000166:cytology; D064591:Allografts / Q000502:physiology*; D000818:Animals; D064592:Autografts / Q000637:transplantation; D001696:Biomechanical Phenomena; D055396:Bone Morphogenetic Protein 2 / Q000627:therapeutic use; D001861:Bone Regeneration / Q000502:physiology*; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000502:physiology; D020219:Chondrogenesis / Q000502:physiology; D003094:Collagen; D005260:Female; D006801:Humans; D008334:Mandible / Q000473:pathology; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D023421:Models, Animal; D010012:Osteogenesis / Q000502:physiology; D010521:Periosteum / Q000601:surgery; D018583:Pliability; D011994:Recombinant Proteins / Q000627:therapeutic use; D013314:Stress, Mechanical; D013552:Swine; D023822:Tissue Engineering / Q000379:methods*; D014021:Tissue Preservation / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry; D020858:Tissue and Organ Harvesting; D016212:Transforming Growth Factor beta / Q000627:therapeutic use; D055114:X-Ray Microtomography
chemical_list: D055396:Bone Morphogenetic Protein 2; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D003094:Collagen