AWARD NUMBER: W81XWH-13-1-0244 TITLE: Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells

This study aimed to quantify the biomechanical properties of murine meniscus surface. Atomic forcemicroscopy (AFM)-based nanoindentation was performed on the central region, proximal side of meniscifrom 6to 24-week old male C57BL/6 mice using microspherical tips(RtipE5 mm) in PBS. A unique,linear correlation between indentation depth, D, and response force, F, was found on menisci from allage groups. This non-Hertzian behavior is likely due to the dominance of tensile resistance by thecollagen fibril bundles on meniscus surface that are mostly aligned along the circumferential direction.The indentation resistance was calculated as both the effective modulus, Eind, via the isotropic Hertzmodel, and the effective stiffness, Sind 1⁄4 dF/dD. Values of Sind and Eind were found to depend onindentation rate, suggesting the existence of poro-viscoelasticity. These values do not significantly varywith anatomical sites, lateral versus medial compartments, or mouse age. In addition, Eind of meniscussurface (e.g., 6.170.8 MPa for 12 weeks of age, mean7SEM, n1⁄413) was found to be significantly higherthan those of meniscus surfaces in other species, and of murine articular cartilage surface (1.470.1 MPa,n1⁄46). In summary, these results provided the first direct mechanical knowledge of murine kneemeniscus tissues. We expect this understanding to serve as a mechanics-based benchmark for furtherprobing the developmental biology and osteoarthritis symptoms of meniscus in various murine models.& 2015 Elsevier Ltd. All rights reserved.