Femke Mathot

Chapter 3 52 Figure 3. Seeding efficiency of three different seeding durations. The efficiency is expressed as a percentage of the cells provided per nerve (1 million cells). The increase between 6 and 12 hours of seeding (p=0.029) undifferentiated MSCs was statistically significant. The increased seeding efficiency of differentiated MSCs between 6 and 12 hours and the decrease between 12 and 24 hours were also statistically significant (both p=0.029). Error bars = SEM. *=statistical significance, p<0.05 DISCUSSION The overall purpose of this study was to determine (I) the influence of processed nerve grafts on the viability of differentiated MSCs, (II) the seeding potential and optimal seeding duration of differentiated MSCs on processed nerve grafts, and (III) the survivability, distribution and migration of differentiated MSCs after seeding. The reagents used to process the nerve allografts in this study 30 did not influence the metabolic activity of either differentiated MSCs or undifferentiated MSCs. Similar to undifferentiated MSCs, the differentiated MSCs were successfully seeded on a processed nerve allograft using a previously reported dynamic seeding strategy 29 , without compromising the quality of the inner nerve ultrastructure. The optimal dynamic seeding time for both groups was 12 hours, which led to the attachment of viable undifferentiated MSCs and differentiated MSCs to the surface of the processed nerve allograft. Both types of MSCs distributed among the nerve allograft in a uniform manner and did not migrate into the ultrastructure of the nerve allograft. In vitro, Schwann-like MSCs support superior neurite outgrowth when co-cultured with motor- neurons and express higher levels of neurotrophic and angiogenic genes compared to undifferentiated MSCs. 18, 19, 24, 25 The potential for uncontrolled proliferation or differentiation of MSCs into non-neural lineages is another argument to differentiate MSCs before implementation. The pluripotency of undifferentiated MSCs makes them difficult to control in vivo. The concern that their potential to promote neoangiogenesis and to regulate the immune response may lead to tumor growth or metastasis has been described, but has not been confirmed yet. 34, 35 The disadvantages of differentiating MSCs into Schwann-like cells include the additional effort and extended preparation time which may delay the period between