Aug. 3 : Scientists have proved that the disputed Korean stem cell line called SCNT-hES-1, the first human embryonic stem (ES) cell line, came from an unfertilised egg, not from cloning.

Embryonic stem cells can be made using different methods. Human ES cells are typically made from embryos that are donated by couples that have undergone in vitro fertilization as a form of assisted reproduction therapy for infertility. Whereas, parthenogenetic ES (pES) cells are derived from embryos created by artificial activation of eggs in the absence of sperm.

ES cells generated by somatic nuclear transfer (ntES) are derived from embryos that are created when the nucleus of an egg is replaced by the nucleus from a body cell.

The creation of human ntES are pES particularly interests researchers because they may provide stem cells that are nearly genetically identical to the donor, and particularly well suited for customized, rejection-proof cell transplantation therapies.

With a view to understand whether the specific genetic recombination events that occur in ES cells derived by the various methods, Dr. George Q. Daley of Children’s Hospital Boston and the Harvard Stem Cell Institute directed a team of researchers to carry out a thorough genome-wide analysis of five novel pES cells, 30 mouse ntES.

The researchers also included the SCNT-hES-1 cell line, which was purportedly generated by Korean scientists using human eggs and somatic cell nuclear transfer, in their analysis.

Although the original paper describing the SCNT-hES-1 cell line was retracted after an investigation by the Seoul National University revealed research misconduct, the derivation of the cell line was never fully resolved.

The new study, published online in the journal Cell Stem Cell, has shown that ntES and pES cells have distinct DNA recombination signatures. Those made from parthenogenetic embryos display a telltale genetic pattern close to the centre of chromosomes.

It has also revealed that the SCNT-hES-1 cell line was not derived by somatic nuclear transfer as was previously claimed.

“Our analysis shows that the recombination pattern of SCNT-hES-1 is distinct from that of an ntES line and is consistent with its derivation from a parthenogenetic embryo. Thus, we conclude that the derivation of SCNT-hES-1 represented the first successful isolation of human pES cells,” says Dr. Daley.

The authors conclude that though there are still significant obstacles to overcome in the generation of pES cells, parthenogenesis is an efficient way of generating embryos, and that it may someday be feasible to generate patient-specific pES cells from females.

“If careful genetic and functional analysis of tissues derived from human pES cells show them to be safe and effective, then pES cells might represent a favourable source for tissue replacement therapies,” says Dr. Daley. (ANI)