Functional innervation in tissue engineered models for in vitro study and testing purposes.

The biotechnology industry is rapidly expanding and the emerging field of tissue engineering is projected to have a high impact in the near future. Recently the field of cellular, drug, and prosthetic delivery has melded with the field of tissue engineering to make simulated tissues. In addition to their roles as tissue substitutes for transplantation, these simulated tissues may provide more accurate models and environments for toxicology testing and the study of peripheral nerves. The current study demonstrates the importance of innervation, in general, for the function of engineered tissues. We observe that the presence of nerves in a tissue engineered (TE) human cornea model enhances the growth of the epithelium and the formation of its protective mucin layer. Innervation also confers protection to the epithelium from chemical insult, as determined by the level of post-treatment epithelial cell death. We demonstrate differential responses of the nerves to chemical stimuli by changes in intracellular sodium as measured by 2-photon microscopy. The 2-photon imaging techniques also allow for the visualization and study of the fine sensory axon fibers within the 3-dimensional tissue. This work demonstrates a role for innervation in the protective quality and function of the engineered tissue, and the potential to use the nerves themselves as indicators of the severity of an insult. These results are important to consider for the development of any optimized TE models for in vitro study and testing purposes.