Method: SDF-1α release kinetics was examined by loading SCSs with 0-1000 ng/mL rmSDF-1α, followed by lyophilization. Chemokine-loaded SCSs were placed in culture wells containing bovine serum albumin-supplemented PBS. Supernatant was collected after 0-30 days; rmSDF-1α released at each time-point was determined with ELISA. In-vitro chemotaxis was examined using transwell migration assay by placing MSCs/EPCs in the upper chamber of Costar transwells. Chemokine-loaded SCS, the negative control (no SCS and rmSDF-1α), or the positive control (no SCS, 100 ng/mL rmSDF-1α in culture medium), was placed in the lower chamber of the transwells (N=3). Cells that migrated to the lower chamber were stained and counted in 5 randomly-selected fields of each transwell. Data were analyzed using one-way ANOVA and Holm-Sidak multiple comparison procedures (α=0.05).
Result: For each rmSDF-1α concentration, chemokine-release was characterized by an initial phase of burst release followed by a period of sustained release, and could be represented by a two-phase exponential association model. For both MSCs and EPCs, SCSs loaded with a minimum of 800 ng/mL of rmSDF-1α exhibited a homing effect that was equivalent to 100 ng/mL of free rmSDF-1α (p>0.05).
Conclusion: SCSs with sustained rmSDF-1α release represent a less costly and less complex alternative to contemporary cell seeding approaches, and provides new therapeutic options for in-situ hard tissue regeneration. Supported, in part, by grant NSFC 81130078 from China.