Tissue models

The hypes and hopes of tissue engineering and associated efforts of researchers to succeed in this area have resulted in many attempts to produce living tissue and organs outside the human body. These include the creation of skin, cartilage, bone, tendon, skeletal muscles, heart muscle, blood vessels, heart valves and bladder tissue, in which the degree of success is mainly evaluated on the basis of structural similarities with native or ‘the original’ human tissue. Despite their envisioned and highly recommended potential as tissue replacements inside the human body, many of these types of tissue still only function outside the human body and have not passed the stage of laboratory prototype or small-scale implantation studies in animals. Thus, the broad-scale clinical application of tissue engineered products lies far ahead and, apart from commercial and regulatory problems, very much depends on scientific progress.Notwithstanding these drawbacks, a decade of intensive and interdisciplinary research, converging knowledge from biology, material science, bioengineering and medicine, has brought scientific and technological progress in the field of regenerative medicine. In line with all this, a more immediate and directly assessable application of tissue engineering has been the creation of three-dimensional (3-D) laboratory models of tissues and organs. Even in those areas where clinically relevant tissues are decades away, the tissues that are currently being made provide powerful ‘living’ biological models. These 3-D models are far more realistic than existing two-dimensional (2-D) cell culture models and can be used to study or test a specific aspect of interest at tissue level with a higher level of experimental control and with less ethical considerations than animal models. Tissue model systems find their application in studying normal and pathological tissue functioning and the associated testing of potential therapies. In addition, they represent useful tools for the development of technologies for regenerative medicine and early diagnosis and tissue screenin