Biomechanical properties of murine meniscus surface via AFM-based nanoindentation

Abstract

This study aimed to quantify the biomechanical properties of murine meniscus surface. Atomic force microscopy (AFM)-based nanoindentation was performed on the central region, proximal side of menisci from 6-to 24-week old male C57BL/6 mice using microspherical tips (R tip ≈ 5 μm) in PBS. A unique, linear correlation between indentation depth, D, and response force, F, was found on menisci from all age groups. This non-Hertzian behavior is likely due to the dominance of tensile resistance by the collagen fibril bundles on meniscus surface that are mostly aligned © 2015 Published by Elsevier Ltd. *Correspondence and requests for materials should be addressed to: Dr. Lin Han Phone: (215)571-3821 Fax: (215)895-4983 lh535@drexel.edu.. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conflict of interest statementThe authors of this study have no personal or financial conflicts of interest with this work. All authors were fully involved in the study and preparation of this manuscript and the material within has not been and will not be submitted for publication elsewhere. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript along the circumferential direction observed on 12-week old menisci. The indentation resistance was calculated as both the effective stiffness, S ind = dF/dD, and the effective modulus, E ind , via the isotropic Hertz model. Values of S ind and E ind were found to depend on indentation rate, suggesting the existence of poro-viscoelasticity. These values do not significantly vary with anatomical sites, lateral versus medial compartments, or mouse age. In addition, E ind of meniscus surface (e.g., 6.1 ± 0.8 MPa for 12 weeks of age, mean ± SEM, n = 13) was found to be significantly higher than those of meniscus surfaces in other species, and of murine articular cartilage surface (1.4 ± 0.1 MPa, n = 6). In summary, these results provided the first direct mechanical knowledge of murine knee meniscus tissues. We expect this understanding to serve as a mechanics-based benchmark for further probing the developmental biology and osteoarthritis symptoms of meniscus in various murine models.

Nanoindentation modulus of murine cartilage: a sensitive indicator of the initiation and progression of post-traumatic osteoarthritis

“…The effective moduli of the Sham knee menisci were similar to our previously reported values of age-matched, normal murine menisci. 24 By contrast, for the synovium, histology did not reveal appreciable signs of inflammation and hyperplasia, such as synovial lining thickening, increased cellularity or inflammatory cell infiltration (Fig. 6b).…”

“…23 Comparing the modulus measured at the same rate amongst different conditions, such as Sham versus DMM, can therefore identify relative differences in their mechanical behaviors. In addition, following the same procedure, 24 nanoindentation was performed on the non-ossified, central region, proximal surfaces of medial and lateral menisci at 8 weeks after surgery ( n = 5).…”

Determining Tension–Compression Nonlinear Mechanical Properties of Articular Cartilage from Indentation Testing

“…Since commercial nano-indenters recently became readily available, nano-indentation has been widely used for the characterization of cartilage. 16, 24, 33 When the indenter size is on the same scale as collagen fibrils or chondrocytes, 10 the continuum assumption is no longer valid, and the technique developed here is therefore not suitable for estimation of mechanical properties at the nano-scale. Secondly, articular cartilage has a much more complicated structure than that described by the two nonlinear models here.…”

“…25 When cartilage is treated as linear elastic material, the Hertzian contact solution on an infinite half space is widely used, which is specifically suitable for nano- or micro-indentation tests. 24 For larger-scale indenters, Hayes solution 17 is often used since it removes the infinite half-space assumption in the Hertzian contact problem. In the early 1980's, Mow and coworkers 32 developed a porous elastic model for articular cartilage.…”

Meniscus mechanics and mechanobiology

“…Using such methods, Danso et al (2015) suggested that the medial meniscus is more inhomogeneous than the lateral meniscus and that the nonlinearities in material properties are due to the density of collagen fibers and the associated fluid content. In contrast, it would appear that the surface layer of the meniscus is relatively homogeneous (Li et al, 2015) and poro-viscoelastic, unlike the deep zones of the tissue. Wheatley et al (2015) utilized the inverse FE approach to demonstrate that menisci subjected to a traumatic compressive load had decreased material properties at twelve weeks post-impact compared to control.…”