In this chapter the major alternative non-pharmacological, non-synthetic replacement methods to treat disease and injury are introduced. These are various methods of regenerative medicine, which incorporate cell therapies, gene therapies and tissue engineering. The first two of these are mentioned briefly since they involve biomaterials only minimally. Tissue engineering concerns the regeneration of tissues or organs through the stimulation of cells so that they recapitulate the power that they have during tissue development, but which they substantially lose once tissues become mature. This recapitulation may be achieved by either molecular and mechanical signaling, or usually by both. The conventional tissue engineering paradigm involves harvesting cells and stimulating them ex vivo, and implanting the resulting construct into the patient at the appropriate time. Other techniques attempt to use the environment of the patient’s own body as the location for regeneration. We discuss here the types of materials that are used in the so-called scaffolds and matrices that form the template of the regenerated tissue and the interactions between these materials and the target cells. Tissue engineering processes have not yet become used in routine clinical practice and cannot at this stage be defined and classified as clearly as with implantable medical devices, but we do discuss their scientific and clinical status in a wide variety of situations.

Introduction to regenerative medicine

There are two stark conclusions that arise from the discussion of implantable medical devices given in the last chapter. First, although they can give very good performance, they will always be limited to situations involving mechanical or physical functions and will not, by themselves, be able to deal with conditions that require biological solutions. Secondly, even in those situations where the performance is good, it will always be less than 100% effective because so many variables impose themselves on the process, especially in the context of biocompatibility and the influence of clinical skills and patient compliance. Outcomes are variable and often unpredictable.