Innervated human corneal equivalents as in vitro models for nerve-target cell interactions.

A sensory nerve supply is crucial for optimal tissue function. However, the mechanisms for successful innervation and the signaling pathways between nerves and their target tissue are not fully understood. Engineered tissue substitutes can provide controllable environments in which to study tissue innervation. We have therefore engineered human corneal substitutes that promote nerve in-growth in a pattern similar to in vivo re-innervation. We demonstrate that these nerves (a) are morphologically equivalent to natural corneal nerves; (b) make appropriate contact with target cells; (c) can generate action potentials; (d) respond to chemical and physical stimuli; and (e) play an important role in the overall functioning of the bioengineered tissue. This model can be used for studying the more general topics of nerve ingrowth or regeneration and the interaction between nerves and their target cells and, more specifically, the role of nerves in corneal function. This model could also be used as an in vitro alternative to animals for safety and efficacy testing of chemicals and drugs.