A U.S. stem cell institute has upheld the validity of the research of stem cell pioneer Hwang Woo-suk despite the controversy over his ethical lapses.

The latest edition of Science magazine quoted said the institute at the University of California in San Francisco as saying the controversy is a blow to Hwang, not to stem cell research.

The institute once tried to set up a U.S. branch of the World Stem Cell Hub headed by Hwang, but its director Arnold Kriegstein decided against it due to lack of clarity in ethical guidelines.

Meanwhile, the magazine described the nationwide campaign in South Korea to support Hwang in the wake of his resignation from all official posts.

Hwang was quoted as saying he is having second thoughts over his resignation.