Approaches to Tissue Engineering

The first part of this book has proposed that tissue engineering is a modern realization of a practice with ancient origins. Tissue engineering is different because technologies that are now available permit generation of synthetic materials that mimic biological materials as well as clinically useful quantities of biological components (such as proteins and cells). These technologies have emerged from rapid advances in the biological sciences and engineering over the past few decades. Since tissue engineering is new, however, few examples of successful tissue engineering are available. The reader, upon recognizing this early stage of development, might presume that the prospects for a compelling chapter on “Approaches to Tissue Engineering” are bleak. Instead, I am convinced that this is the most exciting of times to write such a chapter, because the precedents are not yet assembled and the field has not yet been reduced to systematic divisions. But there are many challenges. The challenge begins with organization of information. Written reviews of tissue engineering to date adopt different organizational structures. For example, an early influential review was organized around replacement strategies for different organ or tissue systems. A similar, although more encyclopedic, approach was used in the first two editions of an edited textbook. This is a sensible arrangement, given that tissue engineering is an interdisciplinary area of study that has emerged in response to rather specific clinical needs, such as the shortage of donor livers and the paucity of grafts for skin. But it is a difficult arrangement for the teacher and student, as it does not require reconciliation between approaches used to solve different problems. For example, although regeneration of skin and liver differs in many essential ways, there are important areas of intersection. As a consequence, an organ or tissue-based approach does not easily allow for assimilation of new knowledge that is acquired by successes made on particular problems. What is tissue engineering and how can the basic principles, which are developed in Part 2 of this book, be integrated into a strategy for the engineering of replacement tissues? The previous three chapters describe important, but focused, elements of tissue engineering practice: cell delivery, agent delivery, and cell interactions with synthetic materials.