Jeremy J. Lemoine

Flow Perfusion Enhances the Calcified Matrix Deposition of Marrow Stromal Cells in Biodegradable Nonwoven Fiber Mesh Scaffolds

In this study, we report on the ability of resorbable poly(L-lactic acid) (PLLA) nonwoven scaffolds to support the attachment, growth, and differentiation of marrow stromal cells (MSCs) under fluid flow. Rat MSCs were isolated from young male Wistar rats and expanded using established methods. The cells were then seeded on PLLA nonwoven fiber meshes. The PLLA nonwoven fiber meshes had 99% porosity, 17 μm fiber diameter, 10 mm scaffold diameter, and 1.7-mm thickness. The nonwoven PLLA meshes were seeded with a cell suspension of 5 × 105 cells in 300 μl, and cultured in a flow perfusion bioreactor and under static conditions. Cell/polymer nonwoven scaffolds cultured under flow perfusion had significantly higher amounts of calcified matrix deposited on them after 16 days of culture. Microcomputed tomography revealed that the in vitro generated extracellular matrix in the scaffolds cultured under static conditions was denser at the periphery of the scaffold while in the scaffolds cultured in the perfusion bioreactor the extracellular matrix demonstrated a more homogeneous distribution. These results show that flow perfusion accelerates the proliferation and differentiation of MSCs, seeded on nonwoven PLLA scaffolds, toward the osteoblastic phenotype, and improves the distribution of the in vitro generated calcified extracellular matrix.

In vitro degradation of in situ crosslinkable poly(propylene fumarate-co-ethylene glycol)-based macroporous hydrogels

The effect of crosslinking density and porosity on the degradation of macroporous hydrogels (MPHs) was evaluated in this study. MPHs were synthesized from aqueous solutions of poly(propylene fumarate-co-ethylene glycol) (P(PF-co-EG)) and poly(ethylene glycol)-diacrylate (PEG-DA) with concurrent free-radical initiation and pore formation reactions involving ammonium persulfate (APS), L-ascorbic acid (AH), and sodium bicarbonate (SB). The crosslinking density was controlled by the ratio of P(PF-co-EG):PEG-DA to obtain molecular weights between crosslinks (M/sub c/) of 1000/spl plusmn/100 and 1880/spl plusmn/320 g/mol. Porosity was controlled by sodium bicarbonate and ascorbic acid concentrations and ranged between 78/spl plusmn/2 and 89/spl plusmn/3%. In vitro degradation was carried out in phosphate buffer saline (PBS) at 37/spl deg/C and a pH of 7.4. MPHs degradation was assessed at 0, 2, 4, 8, and 12-weeks by evaluating the mass loss, volume change, elastic modulus under confined compression, and porosity via /spl mu/CT. Both Mc and porosity had a significant effect on the modulus at the initial time-point. The Mc had the greatest effect on the degradation of these MPHs with percent mass loss up to 62/spl plusmn/8% after 12 weeks.