Skin tissue engineering using cyclic strain bioreactor and gelatin/PLCL scaffolds

Abstract

The skin is exposed to continuous mechanical stimulus at the air-tissue interface. Early work has shown that the mechanical stretching regulates many signal transduction pathways, and thereby controlling proliferation and differentiation of skin-forming cells. Therefore, understanding of the effect of mechanical stimulation on the behavior of skin cells (keratinocytes and/or fibroblasts) cultured onto artificial substrates is essential for designing biologically functional tissue-engineered skin grafts. In this study, we utilized a novel home-made bioreactor that is able to apply cyclic strain to 3-D cultured cells, and examined the influence of the cyclic strain on fibroblast proliferation, matrix production, and mechanical properties of the cell/scaffold construct. Human dermal fibroblasts (HDF) were cultured in 3-D gelatin/PLCL nanofiber scaffold that was fabricated using electrospinning method. Contact-angle measurement and tensile tests indicated that the gelatin/PLCL complex fibrous scaffold exhibited improved mechanical properties as well as more favorable wet ability than that obtained from either gelatin or PLCL alone. In order to investigate the effect of mechanical stimulus on cell function, fibroblasts were seeded onto gelatin/PLCL scaffold and the cell culture was maintained under a static condition and a model regime of continuous cyclic strain (5% strain, 0.25 Hz, 7 day). After one week, the samples under the cyclic strain showed greater elastic modulus relative to those under no mechanical stimulus. Furthermore, the cyclic strain alone was significantly increased the fibroblast proliferation. Application of the cyclic straining to 3-D cultured fibroblasts also increased type IV collagen and fibronectin matrix production. These results suggest that the combination of the bioreactor and the 3-D nanofiber scaffold composed of the polymeric elastomer and natural ECM can be a good candidate for producing biologically robust artificial skin constructs.