*2.1. Reagents*

All reagents were purchased at Sigma (Munich, Germany) unless otherwise indicated. The anti-SOX9 (C-20) and anti-TGF-β(V) antibodies were from Santa Cruz Biotechnology (Heidelberg, Germany), the anti-type-II collagen (II-II6B3) from the NIH Hybridome Bank (University of Iowa, Ames, IA, USA), the anti-type-I collagen (AF-5610) antibody from Acris (Hiddenhausen, Germany), and the anti-type-X collagen (COL-10) antibody from Sigma. The biotinylated secondary antibodies and ABC reagent were from Vector Laboratories (Alexis Deutschland GmbH, Grünberg, Germany). The AAVanced

Concentration Reagent was from System Bioscience (Heidelberg, Germany) and the Cy3 Ab Labeling Kit from Amersham/GE Healthcare (Munich, Germany). The AAV titration ELISA was from Progen (Heidelberg, Germany). The β-gal staining kit and the Cell Proliferation Reagent WST-1 were purchased at Roche Applied Science (Mannheim, Germany), the Beta-Glo® Assay System at Promega (Mannheim, Germany), and the TGF-β Quantikine ELISA at R&D Systems (Wiesbaden, Germany).
