Mechanical Characteristics of Electrospun Aligned PCL/PLLA Nanofibrous Scaffolds Conduct Cell Differentiation in Human Bladder Tissue Engineering

Certain features of electrospun PCL/PLLA nanofibrous scaffolds such as thickness, cross section density, strength, and elastisity can be tailored to mimic the native microenvironment required for bladder tissue engineering. In this study the differentiation of human bladder smooth muscle cells (hBSMCs) cultured on electrospun scaffolds was studied. The scaffolds of aligned PCL/PLLA fibrous with a thickness of about 100 nm, used to implement different mechanical stimulation. Longitudinal (0.7 MPa) and traverse (0.02 MPa) Young's modulus of the constructed hybrid aligned PCL/PLLA scaffolds showed anisotropic orientation of the electrospun fibers. Based on the elastic limit strain, the aligned scaffolds were selected and SEM micrographs used to reveal the outcomes. The application of mechanical forces on seeded scaffolds at physiologic and 0.1 Hz frequencies played crucial role in the differentiation of hBSMCs. Scaffolds were stretched to 2% below the deformation point and the effects of the physiologic and 0.1 Hz stretching frequencies on hBSMCs seeded scaffolds were investigated at gene transcription level. The application of 0.1 Hz stretching forces increased transcriptions of collagen type I/III/IV, elastin, alpha-smooth muscle actin and caldesmon, while at physiologic rate, all of the mentioned genes were down-regulated. On the other hand, exposing human bladder urothelial cells (hBUCs) to 0.1 Hz stretching frequencies promoted transcription of certain functional markers including cytokeratin 8 and 18. We found that mechanical forces with different frequencies exert different regulatory effects on extracellular matrices and contractile genes in hBSMCs and hBUCs that should be considered in tissue engineering strategies.