Biomechanical properties of murine TMJ articular disc and condyle cartilage via AFM-nanoindentation

Abstract

This study aims to quantify the biomechanical properties of murine temporomandibular joint (TMJ) articular disc and condyle cartilage using AFM-nanoindentation. For skeletally mature, 3-month old mice, the surface of condyle cartilage was found to be significantly stiffer (306 ± 84 kPa, mean ± 95% CI) than those of the superior (85 ± 23 kPa) and inferior (45 ± 12 kPa) sides of the articular disc. On the disc surface, significant heterogeneity was also detected across multiple anatomical sites, with the posterior end being the stiffest and central region being the softest. Using SEM, this study also found that the surfaces of disc are composed of anteroposteriorly oriented collagen fibers, which are sporadically covered by thinner random fibrils. Such fibrous nature results in both an F-D3/2 indentation response, which is a typical Hertzian response for soft continuum tissue under a spherical tip, and a linear F-D response, which is typical for fibrous tissues, further signifying the high degree of tissue heterogeneity. In comparison, the surface of condyle cartilage is dominated by thinner, randomly oriented collagen fibrils, leading to Hertzian-dominated indentation responses. As the first biomechanical study of murine TMJ, this work will provide a basis for future investigations of TMJ tissue development and osteoarthritis in various murine TMJ models.

Cyclophilin B control of lysine post-translational modifications of skin type I collagen

“…Samples were embedded in optimum cutting temperature medium (OCT) to produce 40 μm-thick, unfixed cross-sections using Kawamoto’s tape-assisted cryo-sectioning [54]. To quantify the modulus of each anatomical region on the cross-section, AFM-based nanoindentation was performed with a microspherical tip ( R ≈ 5 μm, k ≈ 1 N/m, μMasch) and a Dimension Icon AFM (Bruker) in PBS with protease inhibitors (Sigma-Aldrich), following our established procedures [55]. The effective indentation modulus ( E ind ) was calculated by fitting the loading portion of force-indentation depth curve with the finite thickness-corrected Hertz model (Dimitriadis Ref 65) by assuming the Poisson’s ratio ν ≈ 0.45 [56].…”

Roles of Ihh signaling in chondroprogenitor function in postnatal condylar cartilage

“…The TMJ is composed by the glenoid fossa in the temporal bone, the articular disc and the mandibular condyle. The mandibular condylar cartilage has attracted a great deal of attention from researchers and clinicians owing to its unique biological features and essential roles for proper joint mechanics by providing both tensile and compressive strength, respectively [2, 3]. Articular cartilage constituting other synovial joints in the body is classified as hyaline and exhibits poor repair capacity when damaged [4–7].…”

Multidimensional mechanics: Performance mapping of natural biological systems using permutated radar charts

“…Their tensile properties are plotted in Fig 4A , illustrating the profiles occupy distinct regions of the property space correlated with form and function, as summarized in Box 2 . Fig 4B shows representative microstructures of each material; for details readers are referred to the image sources [ 42 – 46 ].…”

“… (a) Normalized, permutated radar charts comparing five collagenous tissues (see Box 2 ), where the profile averages (lines) and standard deviations/ranges (shaded regions) are shown on the outer edges; the center plot illustrates a trade-off between stiffness (E) and extensibility (ε). (b) Micrographs illustrating key microstructural features correlating each material with its unique property profile; images adapted from literature [ 42 – 46 ] or provided by J. McKittrick (dentin and bone), for illustrative purposes only. Scale bars : (from left to right, top to bottom) 5 μm; 150 μm; 5 μm; 25 μm; 2 μm.…”