Scientists say they have uncovered a new factor behind the detrimental effects of binge drinking on bone health, a discovery they say could eventually help speed up the slow healing caused by excessive alcohol.

A recent study by Loyola University Medical Center researchers shows that too much alcohol blocks a key protein from "recruiting" stem cells needed to create cartilage for healing.

In the study, mice were injected with an alcohol/saltwater solution for several days before scientists gave them bone fractures. Mice in a control group were given equal amounts of a saltwater solution containing no alcohol. All the mice received one solution or the other for up to seven days after the break, until they were euthanized. The mice that received the solution containing alcohol showed about 50 percent less protein needed to "recruit" stem cells to the break site. Those mice also showed less mineralized callus — cartilaginous material that forms around the fracture — and more oxidative stress, which impairs healing.

Under normal conditions without excessive alcohol, a fracture site would be inundated with cartilage, said John Callaci, senior study author and assistant professor of orthopedic surgery and rehabilitation at Loyola. Callaci pointed out there is no cartilage actually in the bone, only in joints, but that the cartilage that forms at the fracture site from stem cells helps strengthen the bone.

"What we see in (animals given alcohol) is less of that material, and cells stay generally in a kind of undifferentiated state," Callaci said. "This study explored how alcohol may inhibit recruitment or homing of cells to the fracture site."

Callaci said alcohol might also be preventing stem cells from differentiating into cartilage cells needed for fracture healing.

"We are seeing that when a bone breaks, the body's response to that is to try to build material around it to try to stabilize it, and then the bone will remodel itself to a normal anatomical shape," Callaci said. "It's regenerative."

The study was presented recently at an American Society for Bone and Mineral Research conference in Baltimore. The research was done in the Molecular and Cellular Bone Biology Laboratory at the Loyola University Medical Center, which Callaci directs. The other authors are Dr. Roman Natoli and Rachel Mauer.

"Despite the fact that we know alcohol has a negative effect on fracture healing, some people are probably going to drink anyway," Callaci said. "If we know why, we may at some point have a targeted therapeutic treatment that could help heal."

Dr. Martin Ronis, professor in the department of pediatrics at the University of Arkansas for Medical Sciences, said while researchers have known for about a decade that excessive alcohol impedes fracture healing, the new study helped show that the key protein in the study, osteopontin, played an important role.

"It follows very nicely from what people have done in past," said Ronis, who was not involved in the study. "Binge drinking is increasing among young people, and (Callaci's) data suggest that continuous alcohol exposure is not required to produce deficits in fracture healing."

Ronis, who has published a number of studies on alcohol and bone loss, is also searching for a way to block alcohol from interfering with fracture healing.

"The consensus seems to be, at this point, … is that alcohol is preventing the normal formation of new bone cells from stem cells in the bone marrow," Ronis said. "It appears to be doing that as a result of the generation of oxidative stress and inflammation."

A follow-up study planned for Callaci's lab will examine possible treatment for alcohol's toxic effects on bones. Researchers in that study will inject mice with stem cells and an antioxidant. Two of Callaci's studies have found binge drinking can cause both temporary and long-term skeletal damage in adolescent rats, and that antioxidant therapy can help strengthen bones after a break.