Five generations of cell preparation: a translational framework for categorizing regenerative stem cell therapies

A description of a proposed categorization scheme of regenerative stem cell therapies illustrated by review of basic science and clinical studies involving the clinical application of mesenchymal stem cells (MSCs) is proposed. The aim of this review is to provide a novel framework for categorizing MSCs according to preparation strategy. Selected basic science studies and clinical trials were used to illustrate the applications in each category of stem cells. A review of the literature regarding stem cell sources and preparation makes apparent that there are five generations of stem cells in various states of study and clinical application, ranging from therapies currently being used in officebased practice to stem cell generations that hold considerable promise but with persistent concerns regarding safety and feasibility. In the last decade, stem cell research has spread to many different branches of regenerative medicine. Basic science and clinical studies examining the use of stem cell transplantation in the treatment of a wide range of human diseases have exponentially increased. The Five Generations Model may be a helpful way to describe stem cells in research and in clinical application. Describing stem cells in terms of cell preparation strategy, rather than source, may facilitate a greater understanding of this therapy by physicians and patients, and provides an opportunity for researchers to incorporate this helpful framework into a description of their background and findings.