Sircol collagen assay

The manufacturer’s protocol was followed for the Sircol collagen assay (SCA) (Biocolor Life Science Assays, UK). In brief, 200 μl of conditioned medium was added to 1 ml of the colorimetric reagent and centrifuged for 30 min at 5000 × g for 20 min. The sample was released from the pellet with an alkali reagent (1.5 N NaOH) and was measured at 500 nm on a high-performance monochromator multimode microplate reader (BMG Labtech, Offenburg, Germany). Absolute values were obtained with a standard graph composed from collagen type I standard, which was supplied with the kit in the range of 5–100 μg/ml.