Femke Mathot

3 MSC-seeding on processed nerve allografts 51 group’ analyses did not show any significant differences. ‘Within group’ analyses showed a significant interaction between seeding efficiency and seeding duration for undifferentiated MSCs (p=0.021) and differentiated MSCs (p=0.007). Pairwise comparisons revealed that the increase between 6 and 12 hours of seeding (p=0.029) undifferentiated MSCs was statistically significant, but not between 12 and 24 hours (p=0.486). The increased seeding efficiency between 6 and 12 hours and the decrease between 12 and 24 hours of seeding of differentiated MSCs were statistically significant (both p=0.029). Considering a shorter seeding duration is more cost effective and time efficient, the optimal dynamic seeding duration was determined to be 12 hours for both groups. The seeding efficiencies at different time points are shown in figure 3 . Cell distribution and migration Dynamic seeding resulted in a layer of viable cells on the surface of the processed nerve allograft with no major differences in distribution between the cell-types and different seeding durations. Virtually no dead cells were apparent on the processed nerve allograft during dynamic seeding, which suggests that only viable cells are able to attach to the nerve. Although subjective, the differentiated MSCs seem to seed in a more clustered fashion than undifferentiated MSCs ( figure 4a-b ). Hoechst stain (not shown) and SEM of the surface of the seeded nerve grafts showed a similar distribution and illustrated that the cells retain their typical shapes during dynamic seeding ( figure 4c-f ). None of the cross-sectional segments of the proximal and mid-portion of the nerves showed migration of both undifferentiated MSCs and differentiated MSCs into the nerve graft ( figure 4g-h ). Figure 2. Metabolic activity of undifferentiated and differentiated MSCs after a processed nerve allograft was introduced to their well. The activity is expressed as a ratio of the metabolic activity of MSCs without a processed nerve allograft. Undifferentiated MSCs had a significantly higher metabolic ratio after 3 (p=0.009) and 7 (p=0.026) days of culture. Error bars = SEM. **=p<0.01, *=p<0.05