Smurf1 Knocked-Down, Mesenchymal Stem Cells and BMP-2 in an Electrospun System for Bone Regeneration

A sandwich-like system, fabricated with electrospun, poly(lactic-co-glycolic-acid) (PLGA) membranes incorporating either human recombinant bone morphogenetic protein 2 (BMP-2) enriched microspheres, rat bone marrow mesenchymal stem cells (rMSC), or rMSC with their Smurf1 (SMAD ubiquitin regulatory factor-1) expression knocked down by means of siRNA (rMSC573) at varying densities was evaluated in a rat calvarial, critical-size defect. The behavior of four membrane varieties, fabricated with different PLGA copolymers, was initially studied in rMSC cultures to decide on optimal membrane degradation and cell proliferation and differentiation characteristics. PLGA75:25 provided the most stable structure, and favored the cell environment. Radiological and histological analyses indicated bone repair in animals treated with the PLGA75:25 bioactivated systems. We found no synergist interaction between BMP-2 and rMSC 8 to 12 weeks postimplantation. By contrast, synergistic defect repair of around 85% was detected after 8 weeks of combined BMP-2 and rMSCS73 treatment.