*2.8. Evaluation of Cell Proliferation and Viability*

Proliferation of chondrocytes in monolayer cultures was estimated using the Cell Proliferation Reagent WST-1, with optical density (OD) values proportional to the cell numbers [22,23,30]. Controls included the same conditions depicted in 2.5. ODs at 450 nm were registered using a GENios spectrophotometer (Tecan) and the percent's of cell viability were calculated as follows:

$$\text{Viability (\%)} = \text{[(OD sample)/(OD negative control)]} \times 100\tag{1}$$
