The present invention describes an in vitro/ex vivo method for the cultivation of connective tissue cells or progenitor cells (e.g. chondrogenic cells) in matrix comprising polysulphated alginate. These cultivated cells can be used in the preparation of a medicament for the treatment or prevention of osteochondral defects. The invention also describes a matrix comprising polysulphated alginate and mammalian connective tissue cells or progenitor cells thereof.