Assessment of tissue responses to tissue-engineered devices

Tissue-engineered devices are functional substitutes for damaged, dysfunctional or lost tissues. The basic structural framework for these devices is provided by biodegradable biomaterials. In some instances, the biomaterials are used alone, especially when the materials are capable of recruiting host cells that will, in time, proliferate and differentiate to form desired functional tissues. However, for most tissue-engineering applications, biomaterials are commonly combined with biological components like cells, proteins, polysaccharides or DNA to facilitate the desired tissue regeneration. Such devices that combine biomaterial and biological components are referred to as combination devices. In an in-vivo environment, the various components of the combination devices could cause complex tissue responses that require rigorous pre-clinical testing. Nevertheless, before commencing any tests, it is essential to understand and define the necessary parameters required to detect the possible tissue responses. Hence, the objective of this chapter is to provide a fundamental overview of tissue responses to tissueengineered devices, outline the tests needed to assess these responses and, finally, give recommendations for testing.