1. Cartilage Engineering+ Regeneration; ETH Zurich; Otto-Stern-Weg 7 8093 Zurich Switzerland
2. Department of Biotechnology; Norwegian University of Science and Technology; Sem Saelands vei 6/8 7034 Trondheim Norway
3. Department of Materials; Polymer Technology Laboratory; ETH Zurich; Vladimir-Prelog-Weg 1-5/10 8093 Zurich Switzerland
4. Department of Developmental Biology; Washington University School of Medicine; St. Louis MO 63110 USA