Determination of Mechanical Properties of Chondrocytes in Articular Cartilage Using Atomic Force Microscopy

Abstract

Atomic Force Microscopy (AFM) based nanoindentation is a widely used technique for measuring mechanical properties of living cells, providing information for understanding their mechanobiological behavior. However, very local properties of cell surfaces have not been characterized earlier. The goal of this study was to develop an AFM-based technique to determine local elastic properties of bovine articular chondrocytes. The Youngs modulus of chondrocytes was 19.3 ± 5.6 kPa for spread cells and 10 ± 4.1 kPa for the round cells. The results were compared to previous studies in which different techniques were used to obtain more global properties of chondrocytes. Our findings suggest that using nanosized AFM tips, the very local cell properties can be measured.

Biomechanics of Chondrocytes and Chondrons in Healthy Conditions and Osteoarthritis: A Review of the Mechanical Characterisations at the Microscale

“…The chondrocytes considered for the experimental tests were primary cells and they were isolated from human and animal cartilage. The main method used for cell harvesting appears to be the enzymatic digestion of cartilage with pronase [41], collagenases [34,38,[44][45][46]50] or with both enzymes [35,36,39,41,42,49,[51][52][53][54]. More details are reported in Section 5.1.…”

“…Linear elastic E = 0.61 ± 0.34 viscoelastic E 0 = 0.29 ± 0.14 E ∞ = 0.17 ± 0.09 µ = 0.61 ± 0.69 [34] femoral condyles;…”

“…The deflection of the cantilever beam, which represents cell deformation, is measured by a laser. AFM has become quite popular for cell mechanical testing as it combines three-dimensional imaging at the nanoscale with the nanoindentation of cells and allows measurements of various cell regions, such as its surface, its subcomponents or the whole cell [34]. When referring to chondrocytes, Darling et al reports a mean constant displacement of about 1 ± 0.3 µm which is applied to the cell using a microscopic cantilever tip made of glass or silicon nitride, usually designed ad hoc.…”

“…Chondrocytes were isolated from cartilage harvested from different sites, such as knees and hips [36,39,51,53,54], for human cells (donors aged between 20-86 years), while animal cells were harvested from femoral condyles and distal metatarsal joints from different sources, such as rat [62], dog [57], pig [35,41] and cattle, which included cows, calves and steers [34,38,42,[44][45][46][47][48][49][50]52,[63][64][65].…”

Comparison of cell mechanical measurements provided by Atomic Force Microscopy (AFM) and Micropipette Aspiration (MPA)

“…1964, Jiao et al 2009, Dulińska et al 2006, neutrophils (Roca-Cusachs et al 2006, Derganc et al 2000, chondrocytes (Allen and Mao. 2004, Florea et al 2014 or lymphocytes (Daza et al 2015, Schmidschonbein et al 1981, Schneider et al 1987, Rosenbluth et al 2006). However, although both techniques were developed to characterize cell mechanical behavior, significant differences in the underlying deformational mechanisms cast doubts on the equivalence of numerical results obtained by both techniques.…”