Cell Volume Changes in Intact Articular Cartilage and Cartilage Explants Following Hypo-osmotic Challenge

INTRODUCTION: Osteoarthritis (OA) is characterized by reduced extracellular osmolarity, i.e. hypo-osmolarity, and increased cell volume. Some studies suggest that deformation behavior of chondrocytes following hypo-osmotic challenge is not affected by the extraor pericellular matrix (ECM/PCM) while others suggest the opposite. Cell responses following hypotonic challenge have been earlier studied by measuring chondrocytes through cut surfaces of tissue explants. However, cutting of the sample may alter the 3D structure of cartilage in the proximity of the cut edge, which could affect cell mechanics. A direct comparative study on the effect of sample preparation (fully intact cartilage vs. cartilage explants) on cell volume behavior is still lacking. We imaged superficial zone (SZ) chondrocytes 1) through intact surfaces of cartilage samples and 2) through cut surfaces of cartilage explants before and after a hypo-osmotic challenge (Figure 1). We hypothesized that cell volume changes following hypo-osmotic challenge near the cut edge of cartilage explants differ significantly from those of cartilage samples with fully intact surfaces.