Chondrogenic Differentiation of Human Chondrocytes and Stem Cells inDifferent Cell Culture Systems Using IGF-1-Coupled Particles

Various cell-based therapies use the transplantation of ex vivo cultured chondrocytes or stem cells to support repair of cartilage defects. Cell expansion in vitro is required prior to transplantation accompanied by cell dedifferentiation, resulting in unwanted fibrocartilage formation in vivo. Targeted application of growth factors during in vitro cultivation is intended to enhance chondrogenic differentiation of cells. In previous studies, collagen-based scaffolds enriched with silica particles coupled with the insulin-like growth factor (IGF) 1 were tested, concerning their suitability to increase the in vitro redifferentiation of human chondrocytes. Accordingly, in the present study chondrogenic differentiation potential of IGF-1-coupled particles was investigated using human chondrocytes cultured in scaffold-free spheroid pellet culture. Further, influence of IGF-1-coupled particles on mesenchymal stem cells derived from bone marrow (BM-MSCs) cultured onto collagen–based scaffold or in pellet culture was examined as well pellet culture was examined. Chondrogenic differentiation was induced by the growth factor IGF-1 applied as I) soluble IGF-1 or II) conjugated to red fluorescent silica particles. In addition, control silica particles conjugated with NH2 were used to exclude adverse side effects. Besides cell proliferation, collagen type II and glycosaminoglycan synthesis was quantified and histological staining performed to investigate the chondrogenic differentiation. In pellet culture, IGF-1-coupled particles were applied during the pellet formation only. Traceable red fluorescent particles showed homogenous distribution within the pellets. Adverse effects were not detected. Human chondrocyte pellets displayed significantly increased collagen type II synthesis using IGF-1-coupled particles, compared to soluble IGF-1. Independent of the application mode, induction of chondrogenic differentiation of BM-MSCs cultured in pellets was not suitable with the addition of IGF-1 only. However, BM-MSCs cultivation onto collagen-based scaffold enriched with IGF-1-coupled particle showed superior glycosaminoglycan synthesis, compared to soluble IGF-1 application. Using IGF-1 coupled to particles within a three-dimensional matrix resulted in an increased stimulatory chondrogenic effect, indicating a promising tool for controlled growth factor delivery during treatment of cartilage lesion.