15502-m-pleumeekers

ABSTRACT Cartilage has limited self-regenerative capacity. Tissue engineering can offer promising solutions for reconstruction of missing or damaged cartilage. A major challenge herein is to define an appropriate cell source that is capable of generating a stable and functional matrix. This study evaluated the performance of culture-expanded human chondrocytes from ear, nose and articular joint as well as bone-marrow-derived and adipose-tissue-derived mesenchymal stem cells both in vitro and in vivo . All cells (at least three donors per source) were culture-expanded, encapsulated in alginate and cultured for five weeks. Subsequently, constructs were implanted subcutaneously for eight additional weeks. Before and after implantation, glycosaminoglycan (sGAG) and collagen content were measured using biochemical assays. Mechanical properties were determined using stress-strain-indentation tests. Hypertrophic differentiation was evaluated with qRT-PCR and subsequent endochondral ossification with histology. Articular chondrocytes had higher chondrogenic potential in vitro than the other cell sources, as assessed by gene-expression and sGAG-content ( p <0.001). However, after implantation, articular chondrocytes did not further increase their matrix. In contrast, ear and nasal chondrocytes continued producing matrix in vivo leading to higher sGAG-content ( p <0.001) and elastic modulus. For constructs containing nasal chondrocytes, matrix- deposition was associated with the elastic modulus ( R 2 =0.477, p =0.039). Although all cells - except articular chondrocytes - expressed markers for hypertrophic differentiation in vitro , there was no bone formed in vivo . Our work shows that cartilage formation and functionality depends on the cell source used. Articular chondrocytes possess the highest chondrogenic capacity in vitro , while ear and nasal chondrocytes are most potent in vivo , making them attractive cell sources for cartilage repair. 60 CHAPTER 4