title: Surface microcracks signal osteoblasts to regulate alignment and bone formation.
abstract: Microcracks are present in bone and can result from fatigue damage due to repeated, cyclically applied stresses. From a mechanical point, microcracks can dissipate strain energy at the advancing tip of a crack to improve overall bone toughness. Physiologically, microcracks are thought to trigger bone remodeling. Here, we examine the effect of microcracks specifically on osteoblasts, which are bone-forming cells, by comparing cell responses on microcracked versus non-microcracked hydroxyapatite (HA) specimens. Osteoblast attachment was found to be greater on microcracked HA specimens (p<0.05). More importantly, we identified the preferential alignment of osteoblasts in the direction of the microcracks on HA. Cells also displayed a preferential attachment that was 75 to 90 μm away from the microcrack indent. After 21 days of culture, osteoblast maturation was notably enhanced on the HA with microcracks, as indicated by increased alkaline phosphatase activity and gene expression. Furthermore, examination of bone deposition by confocal laser scanning microscopy indicated preferential mineralization at microcrack indentation sites. Dissolution studies indicate that the microcracks increase calcium release, which could contribute to osteoblast responses. Our findings suggest that microcracks signal osteoblast attachment and bone formation/healing.
authors.affiliation: Chemical Engineering and Materials Science Department, Michigan State University, United States; The College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, People's Republic of China.
authors.forename: Yutian
authors.initials: Y
authors.lastname: Shu
authors.affiliation: Chemical Engineering and Materials Science Department, Michigan State University, United States; Department of Mechanical Engineering, Auburn University, Auburn, AL 36849, United States. Electronic address: MJB0041@auburn.edu.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Baumann
authors.affiliation: Chemical Engineering and Materials Science Department, Michigan State University, United States.
authors.forename: Eldon D
authors.initials: ED
authors.lastname: Case
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, MI 48824, United States; Department of Radiology, Michigan State University, East Lansing, MI 48824, United States.
authors.forename: Regina K
authors.initials: RK
authors.lastname: Irwin
authors.affiliation: Chemical Engineering and Materials Science Department, Michigan State University, United States.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Meyer
authors.affiliation: Chemical Engineering and Materials Science Department, Michigan State University, United States.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Pearson
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, MI 48824, United States; Department of Radiology, Michigan State University, East Lansing, MI 48824, United States. Electronic address: mccabel@msu.edu.
authors.forename: Laura R
authors.initials: LR
authors.lastname: McCabe
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D016723:Bone Remodeling / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D017886:Durapatite / Q000494:pharmacology; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D010012:Osteogenesis / Q000187:drug effects*; D010316:Particle Size; D013048:Specimen Handling; D013499:Surface Properties; D054457:Tissue Scaffolds / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D017886:Durapatite
keywords: Alignment; Attachment; Maturation; Microcracks; Osteoblast