Embryonic and adult stem cell therapy.

There are many types of stem cells. All share the characteristics of being able to self-renew and to give rise to differentiated progeny. Over the last decades, great excitement has been generated by the prospect of being able to exploit these properties for the repair, improvement, and/or replacement of damaged organs. However, many hurdles, both scientific and ethical, remain in the path of using human embryonic stem cells for tissue-engineering purposes. In this report we review current strategies for isolating, enriching, and, most recently, inducing the development of human pluripotent stem cells. In so doing, we discuss the scientific and ethical issues associated with this endeavor. Finally, progress in the use of stem cells as therapies for type 1 diabetes mellitus, congestive heart failure, and various neurologic and immunohematologic disorders, and as vehicles for the delivery of gene therapy, is briefly discussed.