There are now several methods of producing pluripotent cells from a patient's tissue. These are cells that are similar to embryonic stem cells in that they can be used to produce any type of cell in the body. A supply of patient-matched cells enables a broader range of more effective regenerative therapies to be developed. The earliest methodology for the production of pluripotent cells is known as somatic cell nuclear transfer (SCNT), and over the years has proven to be technically challenging. Few groups even now can reliably use these techniques. A much easier method called induced pluripotency was developed more recently and has captured most of the effort in this field in recent years. However, there are some indications that SCNT produces better cells, free from some classes of abnormality that can be introduced by the induced pluripotency reprogramming process:
Human pluripotent stem cells hold potential for regenerative medicine, but available cell types have significant limitations. Although embryonic stem cells (ES cells) from in vitro fertilized embryos (IVF ES cells) represent the 'gold standard', they are allogeneic to patients. Autologous induced pluripotent stem cells (iPS cells) are prone to epigenetic and transcriptional aberrations.
To determine whether such abnormalities are intrinsic to somatic cell reprogramming or secondary to the reprogramming method, genetically matched sets of human IVF ES cells, iPS cells and nuclear transfer ES cells (NT ES cells) derived by somatic cell nuclear transfer (SCNT) were subjected to genome-wide analyses. Both NT ES cells and iPS cells derived from the same somatic cells contained comparable numbers of de novo copy number variations. In contrast, DNA methylation and transcriptome profiles of NT ES cells corresponded closely to those of IVF ES cells, whereas iPS cells differed and retained residual DNA methylation patterns typical of parental somatic cells. Thus, human somatic cells can be faithfully reprogrammed to pluripotency by SCNT and are therefore ideal for cell replacement therapies.