Artificial Red Cells Show Promise : Blood Substitute Breakthrough?

Artificial red blood cells made from outdated human blood have been shown to be safe and effective when used as oxygen carriers in animals, according to researchers at the University of California, San Francisco.

The artificial cells meet all the requirements of a blood substitute, study leader C. Anthony Hunt said. The substitute could be stored longer than whole blood, could be given to people of any blood type and has potential uses in surgery and trauma care for both humans and animals.

The researchers may do human trials when a sufficient supply of the artificial cells has been produced, Hunt said.

According to a report in the Dec. 6 issue of Science magazine, Hunt and his colleagues make the cells by extracting hemoglobin--the oxygen carrier in real blood--from outdated blood and encasing it in bubbles of fat. Hunt is a professor of pharmaceutical chemistry and pharmacy.

Because everything in the outdated blood except hemoglobin is filtered out--including any viruses that may be present--the substitute would not carry the risk of spreading blood-borne diseases such as AIDS, acquired immune deficiency syndrome, the researchers said.

Smaller Than Natural Cells

The fat bubbles, known as liposomes, are only about 1/20th the diameter of natural red blood cells and therefore are capable of carrying oxygen to places in the body that the larger natural cells cannot reach, Hunt said.

In addition to their application for surgical or trauma patients, some researchers believe that the small size of the artificial red cells, which Hunt calls neohemocytes, could be useful in treating heart attack patients. The substitute cells, they say, could carry oxygen into areas of the heart that are deprived of oxygen because of occluded blood vessels.

The use of neohemocytes as artificial red cells is one of several approaches being taken by scientific groups to develop artificial blood products. Neohemocytes are radically different from another approach that uses perfluorocarbon, a synthetic material, to carry oxygen.

According to the university researchers, the decision last summer by the federal Food and Drug Administration not to approve a perfluorocarbon product called Fluosol has led to increased interest in hemoglobin-based oxygen carriers.

Another approach that uses chemically treated hemoglobin instead of liposome-encased hemoglobin is being researched by the Army and by several private companies, Hunt said in a telephone interview.

In the animal studies, 50% of the blood of rats was replaced with neohemocytes, and various organs were examined at intervals up to one month afterwards. There was little sign of damage to the organs, researchers said, indicating that the artificial cells had been able to pick up oxygen from the lungs and deliver it to the body.