*2.8. Transgene Expression*

*lacZ* expression was assessed using X-Gal staining for monitoring under light microscopy (Olympus BX45) and using the Beta-Glo® Assay System to provide an estimation of the β-gal activity (values expressed as relative luminescence units—RLU—with normalization to the number of cells) [25]. Expression of SOX9 and TGF-β was monitored using immunohistochemical analysis with specific primary antibodies, a biotinylated secondary antibody, and using the ABC method with diaminobenzidine (DAB) as a chromogen for monitoring under light microscopy (Olympus BX45) [44,45]. TGF-β expression was also measured using specific ELISA [45]. All measurements were performed using a GENios spectrophotometer/fluorometer (Tecan, Crailsheim, Germany).
