Engineering stem cells for therapy. 
The differentiation of a stem cell is dependent on the environmental cues that it receives and can be modulated by the expression of different master regulators or by secreted factors or inducers.  The use of genetically modified stem cells to express the required factors can direct differentiation along the requisite pathway.  This approach to the engineering of stem cells is important, as control of the pluripotentiality of stem cells is necessary in order to avoid unwanted growth, migration or differentiation to nontarget tissues.  The authors provide an overview of the stem cell engineering field, highlighting challenges and solutions, and focusing on recent developments in therapeutic applications in areas such as autoimmunity, CNS lesions, bone and joint diseases, cancer and myocardial infarction.