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Mater Sci Eng C Mater Biol Appl. 2014 Nov;44:191-200. doi: 10.1016/j.msec.2014.08.036. Epub 2014 Aug 16.

Surface microcracks signal osteoblasts to regulate alignment and bone formation.

Author information

1
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.
2
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.
3
Chemical Engineering and Materials Science Department, Michigan State University, United States.
4
Department of Physiology, Michigan State University, East Lansing, MI 48824, United States; Department of Radiology, Michigan State University, East Lansing, MI 48824, United States.
5
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.

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.

KEYWORDS:

Alignment; Attachment; Maturation; Microcracks; Osteoblast

PMID:
25280696
PMCID:
PMC4186695
DOI:
10.1016/j.msec.2014.08.036
[Indexed for MEDLINE]
Free PMC Article

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