1. Medical Clinic and Polyclinic I, University Hospital "Carl Gustav Carus," D-01307, Dresden, Germany.
2. Tissue Engineering Laboratories, BIOTEC Technische Universität Dresden, D-01307, Dresden, Germany.
3. Max Bergmann Center of Biomaterials Dresden, D-01069, Dresden, Germany.
4. Present address: Forschungszentrum Rossendorf, Bautzner Landstrasse 128, D-01328 Dresden, Germany.