What is tissue engineering?
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.
Pittsburgh Tissue Engineering Initiative, Inc.
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.
Asking the right questions about our bodies and problem solving requires an integrated, multidisciplinary biological and engineering focus. Fundamental to tissue engineering is a systems approach buttressed by biologists and engineers. The biologists and engineers are a team of human problem solvers and the ultimate "body builders"!
We all age. We all will probably become osteoporotic; a significant number of us will get cancer (it is estimated that one in 10 women will get breast cancer and one in 10 men will get prostate cancer); a significant number of us will break a bone.
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.
A multidisciplinary group can propose solutions and answer questions. For example, can insulin-like growth factor be administered locally to selected osteoporotic bone and boost new bone growth? How can we engineer a polymer to deliver a precise, known dose of this growth factor to a specific bone? What imaging technology will be needed to guide the surgeon to the exact location of the bone to be treated?
Jeffrey O. Hollinger, DDS, PhD
Center, Bone Tissue Engineering Center
Carnegie Mellon University
Email:
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.
Michael V. Sefton, ScD
Institute of Biomaterials and Biomedical Engineering
Department of Chemical Engineering and Applied Chemistry
University of Toronto
Email:
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".
Johnny Huard, PhD
Assistant Professor, Department of Orthopaedic Surgery
University of Pittsburgh
Email: jhuard+@pitt.edu
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.
David A. Vorp, PhD
Assistant Professor of Surgery, Bioengineering and Mechanical Engineering
Director, Vascular Surgery and Vascular Biomechanics Research Laboratory
University of Pittsburgh
Email:
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.
David J. Mooney, PhD
Associate Professor, Biologic & Materials Sciences,
Chemical Engineering, and Biomedical Engineering
University of Michigan
Email:
The future of tissue engineering lies in the development of key technologies in the biological sciences and engineering. Although the first focus was on the use of one's own cells, harvest of cells from others will continue and technology will develop beyond skin cells into other areas such as liver, pancreas, muscle and nerve. Stem cell research will play an important role in advancing our understanding of a cell's potential, mechanisms of control and may serve as a viable cell source for various cell therapies and tissue engineering applications. Human mesenchymal stem cells are already being testing in clinical trials with the promise of much more to come. Because cell sourcing is a principle issue limiting feasibility of many commercial applications of tissue engineering, knowledge and technical capability in this area will enable and propel the field of tissue engineering forward in the next ten years.
As more is learned about the biology of cell proliferation and regulation, the chemical engineers will utilize knowledge of the extracellular matrix and cell signaling mechanisms to design better, more mimetic surfaces and scaffolds to promote appropriate tissue formation. More sophisticated biocompatible and bioactive materials will be used as active components of medical devices, targeted towards reformation or regeneration of tissues.
We will become less naïve as to the role of inflammation, wound repair, and tissue response to injury and disease. Rather than being one-dimensional, we will seek the effective combination of a variety of technologies to achieve the goal of regeneration. Supplemental factors, genetic manipulation, biomaterials and cells and tissues formed by cells, will be used in concert to control the native response where undesirable, re-establish lost function and regenerate effective tissue replacements.
Nancy L. Parenteau, PhD
Senior Vice President and Chief Scientific Officer
Organogenesis Inc.
Email: