Viscoelastic recovery time of chondrocytes from monolayer and alginate cultures

This study uses a 3D-printed variable-height flow cellto investigate the viscoelastic properties of in vitro cultured chondrocytes that have synthesized an endogenous neomatrix surrounding the cells. It was hypothesized that chondrocytes could be distinguished by phenotype associated with their culture environment using viscoelastic recovery time, owing to variation in the pericellular matrix (PCM) produced by chondrocytes from different culture methods. The chondrocyte plasma membrane was imaged with confocal microscopy during applied deformation and subsequent recovery. The projected cell area was fitted with a Burgers mechanical model to extract the viscoelastic recovery time. No difference in recovery time between bovine and primary OA cells from monolayer or neotissue-rich alginate cultures was observed. However, a statistically significant difference in recovery time was observed between cells from monolayer and alginate cultures in both the bovine (31 s vs. 13 s) and primary OA (34 s vs. 13 s) groups. This work shows that viscoelastic recovery time is influenced by the culture method used for chondrocytes and further demonstrates the role of the chondrocyte-secreted neotissue as amechanical protector of chondrocytes.