192 BEHAVIOR OF PORCINE MESENCHYMAL STEM CELLS ON A COLLAGEN-GLYCOSAMINOGLYCAN HYDROGEL SCAFFOLD FOR BONE AND CARTILAGE TISSUE ENGINEERING

Abstract

The pig is an ideal species for use in tissue engineering studies of bone and cartilage defect repair. Novel collagen-glycosaminoglycan hydrogel (CG) scaffolds have shown promise for supporting bone and cartilage growth from mesenchymal stem cells. In order to determine the suitability of these scaffolds for use in porcine models for bone and cartilage tissue engineering, we have begun to investigate the behaviour of porcine mesenchymal stem cells on this material. The purpose of this study was to determine if mesenchymal stem cells from fat (ASC) or bone marrow (BMSC) displayed better adherence and penetration into the CG scaffold material. The BMSC and ASC isolated from young adult Yorkshire pigs were cultured in DMEM with 10% fetal bovine serum. The ASC and BMSC were then trypsinized and used to seed ~3 mm diameter CG scaffolds with 140,000 cells/scaffold. Scaffolds were then cultured for 10 days by 3 different methods: roller culture, free-floating non-adherent dishes (floating), or attached to tissue culture-treated dishes (static). At the conclusion of the incubation period, the scaffold pieces were then fixed with 4% paraformaldehyde, embedded for cryosectioning, and sliced into 10 µm cryosections. Sections were stained for vimentin and 4’,6-diamidino-2-phenylindole (DAPI) to label cells. Stained sections were observed on a Leica DMB4200 microscope (Leica Microsystems, Wetzlar, Germany) and images acquired using ImagePro Plus software (Media Cybernetics Inc., Rockville, MD, USA). The DAPI-stained cells were counted to determine cell density and expressed as average number of nuclei per millimeter squared for each cell and culture type. Data were analysed by ANOVA utilising a post hoc Holm multiple comparison analysis. Samples from roller cultures did not display adhered cells for either BMSC or ASC. In contrast, floating and static culture allowed both ASC and BMSC to adhere to the scaffold and migrate to the centre of the scaffold equally well. However, significant differences in cell densities were noted between ASC and BMSC on CG scaffolds, with BMSC growing to higher densities than ASC in both floating and static culture. For floating cultures, BMSC-loaded scaffolds exhibited a cell density of 105.7 compared with 53.3 cells/mm² for ASC (n = 4; P < 0.05). For static cultures, BMSC-loaded scaffolds exhibited a cell density of 128.3 compared with 36.8 cells/mm² for ASC-loaded samples (n = 3; P < 0.01). Thus, BMSC grow to greater densities more rapidly than ASC and may be more efficient for use in forming bone and cartilage on these scaffolds. Current experiments underway will compare osteogenic and chondrogenic differentiation potential of ASC and BMSC on CG scaffolds, and will attempt to engineer osteochondral interface tissue on CG scaffolds from co-cultures of chondrocytes and stem cells.