Initial Challenges to Consider

In recent years the approach to rebuilding tissues inside of the body or creating tissues outside of the body as in vitro models or for implantation has been focused on using tissue-engineering principles. Tissue building during development can be imitated by combining cells and/or biological factors with a biomaterial that acts as a scaffold for tissue development. Cells can synthesize new tissue as well as provide the signals needed for tissue formation. Biomaterials can be designed in forms that imitate the natural organization of the extracellular matrix. Signaling molecules can be bound or incorporated into the scaffolds to aid in morphogenesis, pattern formation, and cell differentiation. Currently, however, the quality and function of many tissue-engineered prostheses still need to be improved to fully address the clinical need. For example, skin can be replaced by the use of allogeneic keratinocytes and dermal fibroblasts on a collagen scaffold. This construct can form an epidermis, stratum corneum with barrier properties and a basal lamina in vivo. However, the secondary structures, such as hair follicles and sebaceous and sweat glands, do not develop. Many tissues have complex primary and secondary structures and functions. The goal is to design better tissue prostheses that mimic or model tissue