(534a) Effect of Adhesion Peptide Incorporation in Poly (L-Lactic Acid) Scaffolds on the Osteoblastic Differentiation of Mesemchymal Stem Cells under Conditions of Flow Perfusion

The presence of RGD on the surface of biomaterials has been demonstrated to affect mesemchymal stem cell (MSC) osteoblastic differentiation in a dose-dependent manner when cultured under static conditions, but no dynamic cultures have been carried out to date. We have been able to culture MSC in the presence of RGD under flow perfusion, which has also been shown to enhance osteoblastic differentiation, thus combining biomimetic chemical and mechanical stimulations in the development of bone tissue engineering constructs. The object of this study was to evaluate the effect of the incorporation of RGD in poly (L-lactic acid) (PLLA) on MSC osteoblastic differentiation under flow perfusion conditions. Modification of PLLA foams with RGD peptides and scaffold seeding using oscillating flow perfusion have been previously characterized in our laboratory. PLLA foams were soaked in an acetone-water mixture, and then incubated in a solution of poly (L-lysine) (polyK). RGDC peptides were linked to the polyK through a disulfide bond, using SPDP as the linker. RGDC surface concentration was varied by changing the polyK incubation concentration. MSC were seeded on the modified scaffolds using oscillating flow perfusion. Inoculated cell suspensions were placed on top of scaffolds accommodated in the chambers of a flow perfusion bioreactor and oscillating flow was applied at 0.15 ml/min for 2h. Cells were allowed to condition for 2h without flow; unidirectional flow was incorporated at 0.15 ml/min and increased after 2h to different flow rates. These flow rates included 0.15, 0.5 and 1.0 ml/min. Seeding of RGDC-modified scaffolds was previously characterized so as to start long term cultures with the same initial scaffold cellularity for all the groups in this study. Cells were culture under these conditions for 8, 12 and 16 days. RGDC surface concentration and flow rate had a direct effect on scaffold cellularity, alkaline phosphatase activity and calcium deposition. Deposition of the osteogenic extracellular matrix also depended on the time of culture, both statically and dynamically.