Hemophilia would appear to be one of the best candidates among genetic diseases for gene therapy. Victims are missing one of two enzymes, called Factor VIII and Factor IX, that are crucial for the clotting of blood. Various studies have shown that inducing production of as little as 5% of the normal amount of either enzyme is sufficient to reduce bleeding and other symptoms and greatly improve the quality of life.
But attempts at gene therapy have had little overall success. Researchers have been able to use viruses to insert the gene for either of the proteins into hemophilia patients, but the results have been modest at best. Even when the gene is present, it has been difficult to turn it on to produce the protein. But safety trials with an alternative approach look quite promising and have even shown some therapeutic benefit.
A team led by Dr. David A. Roth of the Beth Israel Deaconess Medical Center in Boston has tested the technique in six patients with severe hemophilia A, in which the subjects are missing the gene for Factor VIII. Using a technique developed by Transkaryotic Therapies Inc. of Cambridge, Mass., the researchers removed skin cells from each of the patients' arms and used an electrical current to insert a segment of DNA containing the Factor VIII gene into the cells.
After growing the cells in the laboratory, they injected them into fatty tissue in the abdomens of the six patients. The researchers reported in the June 7 New England Journal of Medicine (http://content.nejm.org) that they observed no adverse effects from the injections, which was the primary aim of the trial. But they also observed increased production of Factor VIII in four of the six patients. That increased production was accompanied by reduced episodes of bleeding and a decreased need for externally administered Factor VIII. The researchers plan eventually to inject larger numbers of cells to see if they can eliminate the need for external Factor VIII.
Iron Deficiency Might Affect Math Scores
A team of researchers from the University of Rochester School of Medicine and Dentistry in New York may have an important clue about why adolescent girls typically score lower on standardized tests of aptitude in mathematics.
Dr. Jill S. Halterman and her colleagues studied 5,398 children, ages 6 to 16, who had participated in the National Health and Nutrition Examination Survey III conducted between 1988 and 1994. As part of that study, the children's blood iron levels were measured, as was their performance on standardized tests.
The team reported in the June 6 issue of Pediatrics (http://www.pediatrics.org) that 3% of the children overall were iron-deficient. But 8.7% of the girls were iron-deficient, a state generally attributed to loss of blood during menstruation. They found, moreover, that children who were iron-deficient were 2.3 times as likely to score below average on the mathematics test as those who had normal levels. They did not score lower on reading tests, however.
Researchers have offered a variety of theories about the causes of girls' poor performance on math tests, ranging from poor instruction to lack of attention paid to female students by math instructors.
The current researchers did not recommend that parents give iron supplements to children. They did call, however, for further studies to confirm their findings. And if they are confirmed, Halterman said, then controlled trials of iron supplements should be undertaken to see if they provide a benefit.
Heart Cells Have Ability to Replicate After Attack
Contradicting a long-standing belief, New York researchers have found that heart cells have the ability to replicate after a heart attack. Although that spontaneous replication is clearly not sufficient to overcome the effects of a heart attack, cardiologists hope that they can now find ways to stimulate further replication.
Studies in animals have shown that new cells--particularly stem cells from a donor--can restore heart muscle after a heart attack. The new study suggests that it may not be necessary to add cells to the heart if the heart's own cells can be stimulated to divide.
Dr. Piero Anversa and his colleagues from New York Medical College in Valhalla studied heart tissue from 13 patients who had died within four to 12 days after a heart attack, as well as from 10 patients who died from other causes. They reported in the June 7 issue of the New England Journal of Medicine (http://content.nejm.org) that they found clear evidence of cellular replication in the heart attack victims--both in tissues immediately adjacent to the damaged heart muscle and at sites further removed. In contrast, they found virtually no evidence of replication in the patients without cardiovascular disease.
"With this landmark study, we have a new understanding of the heart that opens up the possibility of repairing heart muscle damage after a heart attack," said Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute.
Medical writer Thomas H. Maugh II can be reached at firstname.lastname@example.org.