Therapeutic Cloning: Derivation and Propagation of Embryonic Stem Cells by Somatic Cell Nuclear Transfer

Embryonic stem cells (ESCs) can grow infinitely and give rise to all types of cells in human body, thus of tremendous therapeutic potentials for a variety of diseases, such as Parkinson’s disease, spinal cord injury, and diabetes. Moreover, the combination of gene modification and directed differentiation of ESCs provides perfect tool for disease modelling and drug discovery. However, tissue rejection following ESCs derivatives transplantation greatly hinders its application. Under such circumstances, the idea of “therapeutic cloning” was proposed, indicating the generation of ESCs from SCNT embryos for therapeutic purpose.

Mouse nuclear transfer embryonic stem cells (NT-ESCs) were first established in 2000, and then proved to be able to differentiate either in vivo or in vitro, and give rise to individual tissues through germ line transmission or tetraploid complementation. Fully reprogrammed NT-ESCs are indistinguishable from ESCs derived from fertilized eggs functionally and substantially. What is more, by deriving NT-ESCs from patient cells, the problem of immune rejection may be avoided. However, the derivation of human NT-ESCs goes with the destruction of clone embryos, leading to fierce ethical disputes. There has not been report of successful establishment of human NT-ES cells so far, and the limited resource of human eggs used for nuclear transfer cumbers the future application of NT-ESCs.

In this chapter, we will introduce therapeutic cloning in two aspects as SCNT and NT-ESCs, and the history, nowadays status and prospects of them will be reviewed.

Keywords: Therapeutic cloning, somatic cell nuclear transfer, NT-ES cells, differentiation, ethical concerns.