Therapeutic cloning: status and prospects.

Embryonic stem cells (ESCs) offer a new and remarkable potential for treating and curing a wide range of genetic diseases such as diabetes and muscular dystrophy, degenerative diseases such as Parkinson's disease, renal disease and heart disease, and traumatic injury such as spinal cord injury. Therapeutic cloning, wherein patient-specific ESCs can be derived from pre-implantation stage embryos produced by somatic cell nuclear transfer, constitutes one approach of obtaining histocompatible cells for engraftment. Recent improvements in the production of cloned embryos in non-human primate models, combined with advances in the ability to establish human ESC lines and direct their differentiation along specific pathways support the notion that therapeutic cloning may soon be feasible. This review summarizes the status and current feasibility of the approach and the technical hurdles that must be addressed, and discusses the ethical issues that have arisen as a result.