Broadly defined, tissue engineering is the development and manipulation of laboratory-grown molecules, cells, tissues and organs to replace or support the function of defective or injured body parts.

Why is tissue engineering important?

The human body is a superbly engineered biological specimen. It is a community of 100 trillion cells. From inception, through embryogenesis and development, from the neonate to toddler, teenager, adult, and the geriatric - in sickness and in health - the human body is a phenomenon and mystery.

Operational success and failure of human physiology conjures up more questions than answers. We currently understand less about how we as humans work, than we may care to admit. By understanding why our bodies are functioning optimally and why things go amuck (for example, why we get osteoporosis or why we get cancer), we may be able to correct "malfunctions" or even interdict before they occur.

Tissue engineering focuses on ways to make our lives better by developing products to help people. Products can consist of treatments to build deficient osteoporotic bone. The products can include treatments to choke off the blood supply to malignant cells, stopping cancer in its tracks.

Tissue engineering also can include technologies to improve surgical operations, diagnoses, and to predict clinical outcomes. For example, will you be likely to develop prostate cancer? Breast cancer? Osteoporosis? If the answer is yes, tissue engineering may offer a way to short circuit these diseases.

Will tissue engineering replace organ transplantation?

Tissue engineering cannot grow whole organs. At least not yet. While tissue engineering can be used to grow skin or bone or cartilage and will soon be successful in growing blood vessels, it is not yet possible to grow large, three-dimensional objects such as a heart, liver or kidney. However, such organs are the goal of the LIFE initiative (Living Implants from Engineering), which is a global project directed at addressing the donor organ shortage through tissue engineering. LIFE wants to create an unlimited supply of vital organs so that patients will not need to wait for organs to become available before they can be treated.

Growing an organ like a heart will require technical advances in a number of areas, including vascularization (to supply the cells of the organ with nutrients), controlling the immune response or alternatively learning how to grow large numbers of cells from a patients own stem cells, and preparing scaffolds with the required strength and flexibility. Progress is being made in all these areas, so that LIFE believes that growing hearts can be achieved in a decade of intensive (but unfortunately expensive) research.

How does Tissue engineering differ from cloning?

Human cloning is generally used to describe the isolation of cells from an adult, and extraction of the nucleus from one of these cells. This nucleus is then injected into an embryonic cell and therefore all the embryos derived from this will be identical to the adult where the first cells are being isolated. This is in sharp contrast to tissue engineering that aims at using cells from human tissue - muscle, for example - to regenerate another human tissue for the repair or replacement of that tissue. While stem cells can be used, they are not implanted into embryos, nor is the goal of tissue engineering to reproduce an exact copy of the "donor".

How does tissue engineering differ from gene therapy?

Tissue engineering includes distinct, or at least additional steps as compared with gene therapy. For example, for some disease states, a tissue engineering approach could involve the following steps: 1) the affected cells are isolated from the patient; 2) the cells are treated by a gene therapy technique to express a particular protein of interest; 3) the treated cells are transplanted back into the pateint. Gene therapy involves only step #2, i.e. the technique to introduce an exogenous gene within a new cell.

What does the future hold for tissue engineering?

Tissue engineering will likely have a significant impact in several areas of science and medicine in the future. One important area of impact will be clinical medicine.
Tissue engineering products (e.g., skin, cartilage) based on cell transplantation approaches are already available for clinical use. Regeneration of skin, bone, and blood vessels using delivery of recombinant growth factors will likely be routine in the near (5-10 years) future as well. We will undoubtedly see additional engineered tissues used in a variety of clinical applications in the future.

The engineering of complete internal organs (e.g., liver) is an ambitious goal, but one that researchers will continue to pursue over the coming decades due to the urgent need for additional organs for transplantation.

Tissue engineering is already an interdisciplinary field, but this field will need to integrate even more basic biology and fundamental engineering to solve the complex biological problems faced by this field.

The knowledge gained from the current genomics and proteomics work will give tissue engineering a number of new molecular targets for therapies. A variety of engineering design elements, including biomechanics and mass transport, will be critically important to the long-term success of this field.

Tissue engineering is currently, and will continue to provide novel experimental systems to study basic developmental, pathologic, and regenerative processes. The standard model system of today, two-dimensional cell culture, clearly fails to mimic many critical features of normal tissues.

Tissue engineering systems allow one to precisely define the microenvironment (e.g., cell types, matrix, growth factors) in which tissues are developing. The use of these systems in basic biological studies will likely be invaluable in the future. This role for the field may even be more important than the direct clinical application of engineered tissues, as it may lead to scientific advances on many fronts.