(680d) Flow Perfusion Culture of Marrow Stromal Cells on Electrospun Polycaprolactone Scaffolds

We have shown previously that the differentiation of marrow stromal cells (MSCs) can be influenced by fluid shear stress using a flow perfusion bioreactor. We demonstrated that the fluid mechanical environment is critical for the osteoblastic differentiation of MSCs using commercially available, titanium microfiber scaffolds. In this work, we have produced electrospun biodegradable, polycaprolactone (PCL) scaffolds as a means to modulate the fluid mechanical environment. To do so, we reproducibly and homogeneously fabricated microfiber scaffolds comprised of 2 to 10 micron fibers; scaffolds were then characterized with respect to pore size and porosity. Doing so allowed for the fluid mechanical environment to be systemically varied. Additionally, to better mimic the nanoscale features of native ECM and to enhance the fluid shear experienced by the MSCs, we fabricated morphologically bi-modal scaffolds containing alternating layers of PCL microfibers and nanofibers. This approach capitalizes on both the larger pore sizes generated by the microfiber layers and the nano-scale dimensions of the nanofiber layers. In order to investigate the effect of nanofibers on cell infiltration into three dimensional scaffolds, nanofiber layers of different thicknesses were spun onto a microfiber layer containing pore sizes larger than the diameter of a cell. The extent of nanofiber deposition, and thereby thickness, of the nanofiber layers was modulated by changing the length of spinning time. These layered scaffolds were seeded with MSCs and cultured in a flow perfusion bioreactor. In addition to determining cellular infiltration into the scaffold, the constructs were also analyzed to investigate the effect of the fluid mechanical environment on the osteoblastic differentiation of the MSCs.