1. Institute of Macromolecular Chemistry, v. v. i., Academy of Sciences of the Czech Republic, Heyrovský Sq. 2, 162 06 Prague 6, Czech Republic, Center for Cell Therapy and Tissue Repair, Charles University, V Úvalu 84, 150 06 Prague 5, Czech Republic, Institute of Experimental Medicine, v. v. i., Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20 Prague 4, Czech Republic, and Institute of Clinical and Experimental Medicine, Vídeňská 1958/9, 140 21 Prague 4, Czech Republic