The protocol and procedure for western blotting were as described in our previous reports 30 (link), 44 (link), 45 (link). The anti-p-YAP (Ser127), anti-YAP, anti-RalA and anti-β-actin primary antibodies were obtained from Cell Signalling Technology (Danvers, MA, USA). The anti-Wnt5a, anti-Wnt5b, anti-Aggrecan and anti-SOX9 primary antibodies were obtained from Abcam (Cambridge, MA, USA). The anti-CD63, anti-CD9, anti-CD81 and anti-Alix were obtained from System Biosciences (Palo Alto, CA, USA). Based on previous research 46 (link), 47 (link), collagen type II was analysed using 5% (wt/vol) SDS-PAGE with anti-collagen type II primary antibodies (Chemicon®, Merck-Millipore).