title: Chitosan nanofiber scaffold improves bone healing via stimulating trabecular bone production due to upregulation of the Runx2/osteocalcin/alkaline phosphatase signaling pathway.
abstract: Osteoblasts play critical roles in bone formation. Our previous study showed that chitosan nanofibers can stimulate osteoblast proliferation and maturation. This translational study used an animal model of bone defects to evaluate the effects of chitosan nanofiber scaffolds on bone healing and the possible mechanisms. In this study, we produced uniform chitosan nanofibers with fiber diameters of approximately 200 nm. A bone defect was surgically created in the proximal femurs of male C57LB/6 mice, and then the left femur was implanted with chitosan nanofiber scaffolds for 21 days and compared with the right femur, which served as a control. Histological analyses revealed that implantation of chitosan nanofiber scaffolds did not lead to hepatotoxicity or nephrotoxicity. Instead, imaging analyses by X-ray transmission and microcomputed tomography showed that implantation of chitosan nanofiber scaffolds improved bone healing compared with the control group. In parallel, microcomputed tomography and bone histomorphometric assays further demonstrated augmentation of the production of new trabecular bone in the chitosan nanofiber-treated group. Furthermore, implantation of chitosan nanofiber scaffolds led to a significant increase in the trabecular bone thickness but a reduction in the trabecular parameter factor. As to the mechanisms, analysis by confocal microscopy showed that implantation of chitosan nanofiber scaffolds increased levels of Runt-related transcription factor 2 (Runx2), a key transcription factor that regulates osteogenesis, in the bone defect sites. Successively, amounts of alkaline phosphatase and osteocalcin, two typical biomarkers that can simulate bone maturation, were augmented following implantation of chitosan nanofiber scaffolds. Taken together, this translational study showed a beneficial effect of chitosan nanofiber scaffolds on bone healing through stimulating trabecular bone production due to upregulation of Runx2-mediated alkaline phosphatase and osteocalcin gene expressions. Our results suggest the potential of chitosan nanofiber scaffolds for therapy of bone diseases, including bone defects and bone fractures.
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan ; Cell Physiology and Molecular Image Research Center, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan.
authors.forename: Ming-Hua
authors.initials: MH
authors.lastname: Ho
authors.affiliation: Department of Internal Medicine, School of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chih-Jung
authors.initials: CJ
authors.lastname: Yao
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Mei-Hsiu
authors.initials: MH
authors.lastname: Liao
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Pei-I
authors.initials: PI
authors.lastname: Lin
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Shing-Hwa
authors.initials: SH
authors.lastname: Liu
authors.affiliation: Cell Physiology and Molecular Image Research Center, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan ; Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan ; Anesthetics and Toxicology Research Center, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Ruei-Ming
authors.initials: RM
authors.lastname: Chen
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001847:Bone Diseases / Q000378:metabolism; D001842:Bone and Bones / Q000187:drug effects* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D048271:Chitosan / Q000737:chemistry*; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D057139:Nanofibers / Q000737:chemistry; D010006:Osteoblasts / Q000187:drug effects; D015675:Osteocalcin / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D054457:Tissue Scaffolds; D015854:Up-Regulation / Q000187:drug effects; D055114:X-Ray Microtomography
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C493716:Runx2 protein, mouse; D015675:Osteocalcin; D048271:Chitosan; D000469:Alkaline Phosphatase
keywords: Runx2/OCN/ALP; bone healing; bone histomorphometry; chitosan nanofibers; micro-computed tomography