Fabrication Of Scaffolds With Different Pore Sizes And Investigation On Effects Of Pore Size On Cellular Fates During In Vitro Culture

Tissue engineering holds great potential for tissue regeneration. The idea is by combining cells, materials and soluble factors, to fabricate tissue alternatives mimicking both structure and function of native ones. Cell homeostasis is regulated in a specific microenvironment in vivo, so called niche, which should be recapitulated by researchers when devising biomaterial scaffolds for tissue regeneration. Recently, it has been recognized that both topographical architectures and mechanical properties of biomaterials are important in dictating cellular fates. Among these, pore size of scaffolds represents one of the most important parameters. However, how pore size can affect tissue formation is still poorly understood.In this study, three-dimensional porous scaffolds with different pore sizes (100-200μm,200-300μm,300-450μm and450-600μm) were prepared using polycaprolactone (PCL), which is of good biocompatibility and biodegradability. Subsequently, the behaviors of human amniotic membrane-derived mesenchymal stem cells (hAMSCs), rabbit articular chondrocytes (rACs) as well as human umbilical endothelial cells (HUVEC) in coculture with hAMSCs in porous scaffolds were investigated. The following findings were obtained:(i) three-dimensional porous scaffolds with four types of pore sizes were fabricated successfully through the combination of solvent case/particle leaching and thermal induced phase separation. These scaffolds had good pore interconnectivity and high porosity (>95%);(ii) All scaffolds could well support both adhesion and proliferation of hAMSCs and rACs. However, proliferation of hAMSCs declined as pore size increased, and the migration of hAMSCs into scaffolds increased with pore size;(iii) scaffolds with small pore size (100-300μm) were more favorable to osteogenic differentiation of hAMSCs;(iv) scaffolds with pore size of200-450μm were better for chondrogenic differentiation of hAMSCs and rACs (passage3), while large pore size (450-600μm) could maintain the phenotype of rACs (passage1);(v) coculture of hAMSCs and HUVEC at a ratio of3:1was optimal to obtain both osteogenic and angiogenic differentiation. However, HUVEC is how to regulate osteogenic differentiation of hAMSCs that remains to be unraveled further.In conclusion, pore size of porous scaffolds exerts significant impact on cellular behavior. However, molecular mechanisms that pore size regulates cell behavior remains to be unraveled further.