Children's Hospital and University of Pittsburgh researchers have identified a group of stem cells derived from adult human muscle that they believe may eventually lead to treatments for such problems as heart attacks and muscular dystrophy.

"This is a major discovery for us," said Johnny Huard, corresponding author of the study published in this month's edition of the journal Nature Biotechnology. He noted that his group's previous research has focused on cells found in mouse muscles.

Though much work remains to be done before a treatment could be developed, the findings bring researchers "much closer to a clinical application of this therapy," said Dr. Huard, a professor and vice chairman of research in orthopedic surgery at the Pitt School of Medicine.

Stem cells have the potential to develop into different cell types and in theory can divide without limit. Among other sites, they can be found in circulating blood and in bone marrow.

In the study, researchers obtained human stem cells from 26 muscle biopsy samples, then injected them into the injured skeletal muscles of mice.

Researchers found that certain stem cells located near the walls of blood vessels, known as myoendothelial cells, were much more efficient at forming skeletal muscle than some other types of stem cells.

Myoendothelial cells also showed no propensity to form tumors, a concern with other stem cell therapies.

Among the issues for further study, Dr. Huard said, are the age group and gender that might produce the best results. Previous research has suggested that stem cells derived from female muscle tissue make more muscle cells than those that come from males.

Eventually, researchers hope that muscle biopsies could be obtained from patients with muscle injuries or disease. The myoendothelial cells could be removed and treated in the lab. The stem cells could then be reinjected into the patient to repair the muscle damage.

By treating patients with their own stem cells, the risk of rejection posed by using stem cells from another source would be eliminated.

Besides Dr. Huard, other study authors were Bo Zheng, the lead author; Bruno Peault; Baohong Cao; Mihaela Crisan; Bin Sun; Guang heng Li; Alison Logar; Solomon Yap; Jonathan Pollett; Lauren Drowley; Theresa Cassino; Burhan Gharaibeh; and Bridget Deasy.