Stem Cell Factories - the Rebirth of Tissue Engineering and Regenerative Medicine

Uncountable dreams, myths and excitements on artificial generation of tissues, organs, and even whole organisms accompany mankind's history to master health and disease. The creation of Eve out of Adam's rip, the generation of Prometheus without sexual reproduction in the Greek mythology, and the failing trial by Doctor Faustus in Goethe's poetry to build a living Homunculus illustrate the desire of mankind to overcome sickness and perishability [1]. With the emergence of empirical sciences during and after the Enlightenment era, the physicochemical understanding of man and his failures led to the discoveries of modern developmental biology [2], which were culminating in seismic achievements such as cloning of the sheep Dolly, growing of a human ear on a mouse - the so-called auriculosaurus - or the isolation of omnipotent human embryonic stem cells [2,3]. Although tissue engineering (TE) and regenerative medicine (RM) - often reflected by the acronym ‘TERM’ - are used synonymously and interchangeably in literature, the two areas of medical science pursue different focus and at the same time are complementary to each other [4]. TE goes back to early work by Vacanti, Langer, Green, Matapurkar and many others, combining in vitro isolated and expanded organ-specific cells in co-existence with artificial biodegradable matrix scaffolds to replace diseased, defect or missing organ tissue such as bone, cartilage, liver, ureter and others in attempt to generate in vivo engineered (induced) organ tissue [5,6,7,8]. Publications on TE started to appear as early as 1990 while the more comprehensive entity of RM appeared in the literature only by 2000 and thereafter [9]. There are many, ever changing definitions of RM in the literature reflecting evolving science and technologies involved but also taking care of society's needs driven by population growth and demographic changes. One of the most comprehensive outline of today's RM is given by Greenwood et al. [10] in 2006 which covers also the progresses made since then: ‘Regenerative Medicine is an emerging interdisciplinary field of research and clinical application focused on the repair, replacement or regeneration of cells, tissue or organs to restore impaired function resulting from any cause, including congenital defects, disease, trauma and aging. It uses a combination of several technological approaches that moves it beyond traditional transplantation and replacement therapies. These approaches may include, but are not limited to, the use of soluble molecules, gene therapy, stem cell transplantation, tissue