WASHINGTON - Chinese researchers said Thursday they have developed an "easy and safe way" to create stem cells, a breakthrough that could greatly promote the development of so-called therapeutic cloning to generate tissues and organs for treatment of diseases.

The method, described in the US journal Science, involved a cocktail of small-molecule compounds to reprogram somatic cells to a pluripotent state with the ability to differentiate into any other type of cell in the body.

Previously, the genetic manipulation required to induce this pluripotent state, via nuclear transfer into oocytes or through the ectopic expression of defined factors, is complicated, a fact that has limited the cells' clinical applications so far.

In this study, Professor Deng Hongkui of Peking University said his team validated "a whole new route" to pluripotent stem cells by inducing a pluripotent state in mouse somatic cells with a combination of seven small-molecule compounds.

"Small molecules have advantages because they can be cell permeable, non-immunogenic, more cost-effective, and can be more easily synthesized, preserved, and standardized," the researchers wrote in their paper.

"Moreover, their effects on inhibiting and activating the function of specific proteins are often reversible and can be finely tuned by varying the concentrations," they said.

In total, pluripotent stem cells can be generated from mouse somatic cells at a frequency up to 0.2 percent using the combination of small-molecule compounds, the researchers found.

To characterize their differentiation potential, they injected the chemically induced pluripotent stem cells (CiPSCs) into immunodeficient mice and found that the cells were able to differentiate into tissues of all three germ layer.

Unlike mice generated through traditional methods, the mice generated from CiPSCs were "100 percent viable and apparently healthy for up to 6 months," they said.

Using the CiPSCs technology, the researchers have successfully created several healthy laboratory mice from fibroblastic cells in the adult mouse lung, including one called QingQing, Deng wrote in an email.

"QingQing has been living for more than 100 days up to now. It develops well and it's lively and healthy. What's more, QingQing has already got its own 'babies' and they no longer need to worry about their health," Deng said.

The researchers believed that these findings "open up the possibility of generating functionally desirable cell types in regenerative medicine by cell fate reprogramming using specific chemicals or drugs, instead of genetic manipulation and difficult- to-manufacture biologics."

"To date, the complete chemical reprogramming approach remains to be further improved to reprogram human somatic cells and ultimately meet the needs of regenerative medicine," they wrote.