| Rather than avoiding detection and "doing no harm," next generation biomaterials will have signals incorporated into their structure that interact with the body, enhancing healing and integration. Knowledge of appropriate ligands, receptors, signaling pathways, and target genes will allow for application specific biomaterials. In a simplified view, this bioactive system consists of a cell, a signal, and a scaffold. This project has endeavored to define each component of this scheme, leading to a bioactive scaffold that controls epithelial differentiation with direct application in percutaneous devices, tissue engineering, and wound healing. The epithelial cell is a perfect model cell-type for studying how exogenous signals influence physical and biochemical behavior. Ubiquitously expressed and associated with many disease processes, the epithelial cell has a distinct differentiation profile with phenotypic markers at each stage of the progression. As a first step towards developing a model system, rat esophageal epithelial cells were isolated and characterized for their epithelial identity, adhesion characteristics, and ability to generate an epithelium on a variety of natural and synthetic materials. One signaling pathway shown to influence epithelial differentiation is Notch. Evolutionarily conserved, Notch influences development and normal cell function in a range of species and cell types. Though normally a cell-to-cell signaling pathway, we considered an alternative possibility of using a biomaterial-immobilized Notch ligand to control epithelial differentiation. Jagged-1, a Notch ligand, was successfully immobilized to a tissue culture dish and retained its bioactivity. Plating epithelial cells on the ligand resulted in enhanced differentiation, manifested by expression of intermediate- and late-stage differentiation markers, as well as profound agglomeration and stratification. The scaffold, poly (2-hydroxyethyl methacrylate) (polyHEMA), has seen widespread use in medical applications. Its low protein adsorption, tissue-like properties, and hydroxyethyl side chain make it an excellent choice for use as a bioactive scaffold. The final aspect of this project was to modify polyHEMA with Jagged-1 to induce Notch signaling. This included various immobilization approaches (direct and indirect) and bioactive moieties (short peptide and full-length Jagged-1). After surface characterization and cell interaction studies, this bioactive construct was tested in an in vitro organ culture model for percutaneous devices. |
