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differences could be observed in comparison with constructs cultured in ‘basic medium’ (both Transwell® system and h BMSC-conditioned medium p >0.05). (Figure 7D) This indicates that h MSCs have the ability to improve cartilage matrix formation in co- culture, by improving b AC-proliferation capacity as well as increasing b AC-sGAG-production. Moreover, when exposed to paracrine factors of h BMSC, hypertrophic differentiation was not significantly enhanced compared to untreated b ACs. In pellet co-culture, matrix production was similarly produced as in 3D-alginate constructs, meaning that direct cell-cell contact is not required for co-cultures of h MSCs and b ACs. (Figure 7C) Figure 6. Paracrine effect of b ACs on h AMSCs and h BMSCs. (A) Schematic overview. In purple: h MSCs ; in green: b ACs. (B) The DNA and sGAG content of h AMSCs and h BMSCs in the presence of paracrine factors of b ACs via Transwell® system or b AC-conditioned medium. The DNA content after 3 weeks of culture was compared to the initial DNA content prior to cell-culture (dotted line). *, ** or *** indicates p -values smaller than 0.05, 0.01 or 0.001 respectively compared to the amount of DNA prior to cell culture. Data are shown as box-whisker plots of 6 samples of one experiment. For statistical evaluation, a Kruskal-Wallis followed by the Mann-Whitney-U test was use followed by a Bonferroni's post-hoc comparisons test. TW = Transwell ; CM = Conditioned Medium ; h AMSC = human Adipose-tissue-derived Mesenchymal Stem Cell ; h BMSC = human Bone-marrow-derived Mesenchymal Stem Cell ; b AC = bovine Articular Chondrocyte. 100 CHAPTER 5