title: Optimizing Collagen Scaffolds for Bone Engineering: Effects of Cross-linking and Mineral Content on Structural Contraction and Osteogenesis.
abstract: BACKGROUND
  Osseous defects of the craniofacial skeleton occur frequently in congenital, posttraumatic, and postoncologic deformities. The field of scaffold-based bone engineering emerged to address the limitations of using autologous bone for reconstruction of such circumstances. In this work, the authors evaluate 2 modifications of three-dimensional collagen-glycosaminoglycan scaffolds in an effort to optimize structural integrity and osteogenic induction.
  
  
  METHODS
  Human mesenchymal stem cells (hMSCs) were cultured in osteogenic media on nonmineralized collagen-glycosaminoglycan (C-GAG) and nanoparticulate mineralized collagen-glycosaminoglycan (MC-GAG) type I scaffolds, in the absence and presence of cross-linking. At 1, 7, and 14 days, mRNA expression was analyzed using quantitative real-time -reverse-transcriptase polymerase chain reaction for osteocalcin (OCN) and bone sialoprotein (BSP). Structural contraction was measured by the ability of the scaffolds to maintain their original dimensions. Mineralization was detected by microcomputed tomographic (micro-CT) imaging at 8 weeks. Statistical analyses were performed with Student t-test.
  
  
  RESULTS
  Nanoparticulate mineralization of collagen-glycosaminoglycan scaffolds increased expression of both OCN and BSP. Cross-linking of both C-GAG and MC-GAG resulted in decreased osteogenic gene expression; however, structural contraction was significantly decreased after cross-linking. Human mesenchymal stem cells-directed mineralization, detected by micro-CT, was increased in nanoparticulate mineralized scaffolds, although the density of mineralization was decreased in the presence of cross-linking.
  
  
  CONCLUSIONS
  Optimization of scaffold material is an essential component of moving toward clinically translatable engineered bone. Our current study demonstrates that the combination of nanoparticulate mineralization and chemical cross-linking of C-GAG scaffolds generates a highly osteogenic and structurally stable scaffold.
authors.affiliation: *Division of Plastic and Reconstructive Surgery, UCLA David Geffen School of Medicine †Division of Plastic and Reconstructive Surgery ‡Research Service, Greater Los Angeles VA Healthcare System, Los Angeles, CA §Department of Chemical and Biomolecular Engineering, Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL.
authors.forename: Justine C
authors.initials: JC
authors.lastname: Lee
authors.forename: Clifford T
authors.initials: CT
authors.lastname: Pereira
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Ren
authors.forename: Weibiao
authors.initials: W
authors.lastname: Huang
authors.forename: David
authors.initials: D
authors.lastname: Bischoff
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Weisgerber
authors.forename: Dean T
authors.initials: DT
authors.lastname: Yamaguchi
authors.forename: Brendan A
authors.initials: BA
authors.lastname: Harley
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Miller
mesh_terms: D001861:Bone Regeneration / Q000502:physiology*; D002113:Calcification, Physiologic / Q000502:physiology; D017610:Calcium Compounds / Q000737:chemistry; D002126:Calcium Hydroxide / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D002809:Chondroitin Sulfates / Q000737:chemistry*; D024042:Collagen Type I / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D006801:Humans; D058574:Integrin-Binding Sialoprotein / Q000032:analysis; D059630:Mesenchymal Stem Cells / Q000502:physiology; D008903:Minerals / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry; D015675:Osteocalcin / Q000032:analysis; D010012:Osteogenesis / Q000502:physiology*; D010756:Phosphoric Acids / Q000737:chemistry; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry*; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D017610:Calcium Compounds; D002130:Calcium Phosphates; D024042:Collagen Type I; D003432:Cross-Linking Reagents; D058574:Integrin-Binding Sialoprotein; D008903:Minerals; D009566:Nitrates; D010756:Phosphoric Acids; D015675:Osteocalcin; D002809:Chondroitin Sulfates; C020243:calcium phosphate; C030242:phosphoric acid; C059948:calcium nitrate; D002126:Calcium Hydroxide