1. ¹Tissue Engineering, VA Boston Healthcare System, Boston, MA, USA
2. ²Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
3. ³Department of Orthopaedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA

Correspondence: M Spector, Tissue Engineering, VA Boston Healthcare System, 150 S. Huntington Ave., MS 151, Boston, MA 02130, USA. E-mail: mspector@rics.bwh.harvard.edu

Received 7 September 2006; Revised 14 November 2006; Accepted 13 December 2006; Published online 22 February 2007.

Abstract

This study investigated the use of a type II collagen-glycosaminoglycan (CG) scaffold as a nonviral gene delivery vehicle for facilitating gene transfer to seeded adult articular chondrocytes to produce an elevated, prolonged and local expression of insulin-like growth factor (IGF)-1 for enhancing cartilage regeneration. Gene-supplemented CG (GSCG) scaffolds were synthesized by two methods: (1) soaking a pre-cross-linked CG scaffold in a plasmid solution followed by a freeze-drying process, and (2) chemically cross-linking the plasmid DNA to the scaffold. Two different plasmid solutions were also compared: (1) naked plasmid IGF-1 alone, and (2) plasmid IGF-1 with a lipid transfection reagent. Plasmid release studies revealed that cross-linking the plasmid to the CG scaffold prevented passive bolus release of plasmid and resulted in vector release controlled by scaffold degradation. In chondrocyte-seeded GSCG scaffolds, prolonged and elevated IGF-1 expression was enhanced by using the cross-linking method of plasmid incorporation along with the addition of the transfection reagent. The sustained level of IGF-1 overexpression resulted in significantly higher amounts of tissue formation, chondrocyte-like cells, GAG accumulation, and type II collagen production, compared to control scaffolds. These findings demonstrate that CG scaffolds can serve as nonviral gene delivery vehicles of microgram amounts of IGF-1 plasmid (<10 g per scaffold) to provide a locally sustained therapeutic level of overexpressed IGF-1, resulting in enhanced cartilage formation.