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.