Femke Mathot

4 Interaction between MSCs and a nerve allograft 67 (-0.111 ± 0.019; p<0.001) and no significant changes in the expression of PMP22 and PTN . Gene expression over time In general, expression of NGF , GDNF and PMP22 in undifferentiated MSCs appeared to increase after 3 days of culture and remained elevated over the subsequent days until day 7, while expression of GAP43 and PTN remained low. In differentiated MSCs, expression of NGF , GDNF and GAP43 was especially high during the first 3 days after seeding, while the PTN and PMP22 expression in differentiated MSCs increased after 7 days of culture. All neurotrophic expression curves are displayed in figure 2 with asterisks demonstrating significant differences between groups. Angiogenic gene expression Baseline gene expression Baseline CD31 expression did not significantly differ between undifferentiated and differentiated MSCs (p=0.414). VEGF1 expression was significantly higher in differentiated MSCs than in undifferentiated MSCs before seeding (19.351 ± 3.138, p=0.003). Interaction Seeding the different cell-groups on a decellularized nerve allograft led to enhanced expression of CD31 but this trend in mRNA levels was not statistically significant. Enhanced VEGF1 expression for both undifferentiated MSCs (+67.121 ± 9.064; p<0.001) and differentiated MSCs (+36.522 ± 9.064; p=0.004) after seeding was statistically significant. Gene expression over time Generally, CD31 expression in undifferentiated and differentiated MSCs peaked 24 hours after seeding and declined to minimal expression at 7 days after which the expression remained low. ANOVA analysis did not demonstrate a significant interaction between culture duration, cell type and CD31 expression (p=0.094). ANOVA analysis showed a significant interaction between cell-type, time and VEGF1 expression (p=0.001). The VEGF1 expression curve followed the same pattern in both groups: it peaked directly after seeding and reached a plateau phase from 7 days onwards. All angiogenic expression curves are depicted in figure 3 . Extracellular matrix gene expression Baseline gene expression The baseline expression of COL1A1 (p=0.134) and LAMB2 (p=0.232) did not significantly differ between undifferentiated and differentiated MSCs. Differentiated MSCs had a significantly higher expression of COL3A1 (13.119 ± 5.492, p=0.049), while undifferentiated MSCs showed significantly higher FBLN1 expression (1.767 ± 0.446, p=0.013). Interaction The interaction with the ECM of decellularized nerve allografts led to significantly enhanced