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Optimizing Collagen Scaffolds For Bone Engineering: Effects Of Crosslinking And Nanoparticulate Mineralization On Structural Contraction And Osteogenesis
Justin Maxhimer, MD1, Clifford T. Pereira, MD1, Xiaoyan Ren, MD, PhD1, Daniel W. Weisgerber, BA2, David Bischoff, PhD1, Dean T. Yamaguchi, MD, PhD1, Brendan A.C. Harley, ScD2, Timothy A. Miller, MD, PhD1, Justine C. Lee, MD, PhD1.
1University of California Los Angeles, Los Angeles, CA, USA, 2University of Illinois Urbana Champaign, Urbana, IL, USA.

PURPOSE:
Osseous defects of the craniofacial skeleton occur frequently in congenital, post-traumatic, and post-oncologic 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, we evaluate two 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 non-mineralized (C-GAG) and nanoparticulate mineralized (MC-GAG) type I collagen-glycosaminoglycan scaffolds in the absence and presence of crosslinking. At 1, 7 and 14 days, mRNA expression was analyzed using quantitative real-time RT-PCR 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 micro-computed tomographic (micro-CT) imaging at 8 weeks. Statistical analyses were performed with Student’s t-test.
RESULTS:
Nanoparticulate mineralization of collagen-GAG scaffolds (MC-GAG) increased expression of both OCN and BSP. Crosslinking of both C-GAG an MC-GAG resulted in modestly decreased osteogenic gene expression, however, structural contraction was significantly decreased after crosslinking. hMSC-directed mineralization, detected by micro-CT, was increased in nanoparticulate mineralized scaffolds, although the density of mineralization is decreased in the presence of crosslinking.
CONCLUSION:
Optimization of scaffold material is an essential component of moving towards clinically-translatable engineered bone. Our current study demonstrates that the combination of nanoparticulate mineralization and chemical crosslinking of collagen-GAG scaffolds generates a highly osteogenic and structurally stable scaffold.


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