Abstract
Adult stem cells are found in most tissues, where they are thought to participate in natural turnover and regeneration. Under defined conditions, some of these cells can also be significantly expanded and differentiated along specific lineages. This chapter is focused on mesenchymal stem cells (MSCs), which can be isolated from virtually every organ of the human body. While MSCs have a well-proven potential to give rise to connective tissues (e.g., bone, cartilage, fat, etc.), their ability to differentiate into endodermal cell types (and particularly insulin-producing beta cells) is not as clear. However, there is significant evidence that specific treatments may induce insulin expression, even if doubts remain about the true nature of the end product. At any rate, MSCs have other extraordinary features that go beyond their differentiation potential, as they may provide other cells with appropriate engraftment/differentiation niches.