* Corresponding address: Department of Orthopedics, University Medical Centrum Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. Tel.: #31-24-3614932; fax: #31-24-3540230. E-mail address: p.buma@orthp.azn.nl (P. Buma). Biomaterials 22 (2001) 2359}2369 Linkage of chondroitin-sulfate to type I collagen sca!olds stimulates the bioactivity of seeded chondrocytes in vitro Job L.C. van Susante, Jeroen Pieper, Pieter Buma*, Toin H. van Kuppevelt, Henk van Beuningen, Peter M. van der Kraan, Jacques H. Veerkamp, Wim B. van den Berg, Rene H P.H. Veth Orthopaedic Research Laboratory, University Hospital Nijmegen, Netherlands Laboratory of Experimental Rheumatology, University Hospital Nijmegen, Netherlands Department of Biochemistry, University Hospital Nijmegen, Netherlands Received 8 June 2000; accepted 24 November 2000 Abstract An increasing amount of interest is focused on the potential use of tissue-engineered articular cartilage implants, for repair of defects in the joint surface. In this perspective, various biodegradable sca!olds have been evaluated as a vehicle to deliver chondrocytes into a cartilage defect. This cell}matrix implant should eventually promote regeneration of the traumatized articular joint surface with hyaline cartilage. Successful regeneration can only be achieved with such a tissue-engineered cartilage implant if the seeded cells reveal an appropriate proliferation rate in the biodegradable sca!old together with the production of a new cartilage-speci"c extracellular matrix. These metabolic parameters can be in#uenced by the biochemical composition of a cell-delivery sca!old. Further elucidation of speci"c cell}matrix interactions is important to de"ne the optimal biochemical composition of a cell-delivery vehicle for cartilage repair. In this in vitro study, we investigated the e!ect of the presence of cartilage-speci"c glycosaminoglycans in a type I collagen sca!old on the metabolic activity of seeded chondrocytes. Isolated bovine chondrocytes were cultured in porous type I collagen matrices in the presence and absence of covalently attached chondroitin sulfate (CS) up to 14 days. CS did indeed in#uence the bioactivity of the seeded chondrocytes. Cell proliferation and the total amount of proteoglycans retained in the matrix, were signi"cantly higher ( p(0.001) in type I collagen sca!olds with CS. Light microscopy showed the formation of a more dense cartilaginous layer at the matrix periphery. Scanning electron microscopy revealed an almost complete surfacing of the initially porous surface of both matrices. Histology and reverse transcriptase PCR for various proteoglycan subtypes suggested a good preservation of the chondrocytic phenotype of the seeded cells during culture. The stimulatory potential of CS on both the cell-proliferation and matrix retention, turns this GAG into an interesting biochemical component of a cell-delivery sca!old for use in tissue-engineering articular cartilage.  2001 Elsevier Science Ltd. All rights reserved. Keywords: Type I collagen; Sca!old; Chondrocyte; Tissue engineering 1. Introduction The highly limited potential of articular cartilage to regenerate damages to the joint surface is a recognized phenomenon. Extensive research on stimulation of this repair response has been performed and various procedures have been described. However, the eventual evolvement of the repair tissue into qualitatively inferior "brous cartilage remains the most important limiting factor [1}6]. In the last decade, the transplantation of precultured autologous chondrocytes to an articular cartilage defect has been introduced as a new surgical procedure to deal with articular cartilage defects, and has in fact become a clinically accepted treatment modality [7}10]. Since there is only a limited harvesting source for autologous chondrocytes, a small number of cartilage biopsies have to be obtained arthroscopically from which chondrocytes can be isolated by enzymatic digestion. After expansion in monolayer culture, an exponentially increased number 0142-9612/01/$-see front matter  2001 Elsevier Science Ltd. All rights reserved. PII:S0142-9612(00)00423-3