Santa Monica, CA -- (SBWIRE) -- 03/05/2010 -- The National Institutes of Health is proposing to expand its definition of human embryonic stem cells, enabling the university researchers it finances to work with cells derived from a very early human egg.

The proposal will benefit several academic researchers and a company, Advanced Cell Technology, that has filed a request with the Food and Drug Administration to test a treatment for macular degeneration, an eye disease. If approved, it would be among the first clinical tests of embryonic stem cells, which were first discovered in 1998.

Most human embryonic stem cell lines are generated from the blastocyst, an embryonic stage reached five days after fertilization. Government-financed researchers are forbidden by Congress to generate such cell lines because the blastocyst is destroyed, but were allowed by President George W. Bush to work on lines already in existence as of Aug. 9, 2001.

Researchers chafed under these limits because they could derive new lines only with private money. In December, President Obama said federally supported researchers could use many of these privately derived cell lines in their research.

The N.I.H. now proposes to add to its list of approved cell lines those created from blastomeres, the cells generated after the fertilized egg's first few divisions.

"We thought it made no sense to exclude these," said Lana R. Skirboll, an adviser to the director of the agency.

Dr. Robert Lanza, chief scientific officer of Advanced Cell Technology, said the company hopes to start clinical trials this year in which blastomere-derived cells will be used to treat macular degeneration. The company is now responding to F.D.A. requests for further safety data.

As a private company, Advanced Cell itself is not bound by N.I.H. rules, but its clinical trial, to be conducted with the Foundation Fighting Blindness, will be supported by the Department of Defense, so the institutes' approval of the cells is required, Dr. Lanza said.

Researchers at Advanced Cell pioneered the development of embryonic stem cells from blastomeres and have learned how to convert these cells into the special cells that form the basement of the retina. In animal tests, the blastomere-derived retinal cells grew well and allowed the light-detecting rod and cone cells to regenerate, improving the animals' vision, Dr. Lanza said.

Another company, Geron, has received F.D.A. approval for a clinical trial to test human embryonic stem cells to treat spinal cord injury but the trial has been postponed.