Vascular tissue engineering of the middle layer of natural arteries requires contractile smooth muscle cells (SMC) which can be differentiated from adipose-derived mesenchymal stem cells (ASC) by treatment with transforming growth factor-β, sphingosylphosphorylcholine and bone morphogenetic protein-4 (TSB). Since mechanical stimulation may support or replace TSB-driven differentiation, we investigated its effect plus TSB-treatment on SMC orientation and contractile protein expression. Tubular fibrin scaffolds with incorporated ASC or pre-differentiated SMC were exposed to pulsatile perfusion for 10 days with or without TSB. Statically incubated scaffolds served as controls. Pulsatile incubation resulted in collagen-I expression and orientation of either cell type circumferentially around the lumen as shown by alpha smooth muscle actin (αSMA), calponin and smoothelin staining as early, intermediate and late marker proteins. Semi-quantitative Westernblot analyses revealed strongly increased αSMA and calponin expression by either pulsatile (12.48-fold; p < 0.01 and 38.15-fold; p = 0.07) or static incubation plus TSB pre-treatment (8.91-fold; p < 0.05 and 37.69-fold; p < 0.05). In contrast, contractility and smoothelin expression required both mechanical and TSB stimulation since it was 2.57-fold increased (p < 0.05) only by combining pulsatile perfusion and TSB. Moreover, pre-differentiation of ASC prior to pulsatile perfusion was not necessary since it could not further increase the expression level of any marker.
Keywords: Bioreactor technique; Contractile phenotype; Mechanical strain.