Effect of Plasminogen Activator Inhibitor-1 on extracellular matrix homeostasis in scaffold-free spheroids from human chondrocytes Carlos Suarez-Ahedo; Carlos Martinez-Armenta; Laura E. Martínez-Gómez; Oswaldo González-Mendoza; María de Jesús Hernández Rocha; Gabriela A. Martínez-Nava; Carlos Pineda; Alberto López-Reyes;