Leading U.S. stem cell expert Gerald Schatten wants specific guidelines and regulations on egg donations for research.

The University of Pittsburgh professor on Friday released a statement in response to the news conference of his former research partner Hwang Woo-suk.

Hwang admitted to reporters ethical lapses in his research and announced his resignation from all official posts.

Schatten also urged a debate on ethical issues on egg donations and thorough regulation of the donation processed, but added the scientific conclusions of Hwang's research remain valid.

The statement, however, did not mention Hwang's resignation as World Stem Cell Bub chief or if Schatten was willing to mend ties with his former partner.

A source close to Schatten said Hwang's news conference was an apparent attempt to clear up why Schatten ended the partnership, adding Schatten is optimistic that stem cell research will continue and advance responsibly.