Molecular glue in human bone capable of preventing fracture: study

A sort of natural "glue" in the human bone is capable of helping bones resist fracture, US scientists reported on Tuesday.

This startling find may lead to new therapies for bone fractures, or even to prevention, according to the researchers at the University of California, Santa Barbara. The scientists described their findings in the August issue of the journal Nature Materials.

This glue appears to contain "springs" that uncoil when the bone is stressed, helping the bone absorb shock. When the stress is relaxed, they coil back to their original structure. The scientists spent several years tracking down where in the bone the glue is located, and how it works.

"Before this research, it was well known that the mechanical properties of bone depended on mineral particles and on collagen fibrils," said Paul Hansma, a professor who led this study.

"The picture of bone was that it consisted of these collagen fibrils coated with tiny mineral crystals only a few atoms thick. What we found is that there is a glue in bone that holds these mineralized collagen fibrils together, and this glue works along the same principles that our group found in abalone shells. This glue involves sacrificial bonds (with hidden length) that uncoil when the bone is stressed."

They discovered these "molecular shock absorbers" providing a kind of self-healing glue holding biological mineralized structures together when studying the abalone shell six years ago. Now they have found the same fundamental mechanisms operating in human bone.

The tiny molecular structures were found when the researchers observed bone tissue with the Atomic Force Microscope (AFM), which can look at the nano-scale level of biological materials.

These mechanisms give young healthy bone its tremendous resiliency and resistance to fracture, and actually help heal small microcracks soon after they're formed, according to the researchers. But the molecules will change and become depleted with age, as well as being affected by certain diseases.

When the exact molecules of this glue are identified, they can then become therapeutic targets, the researchers said. This fundamental discovery is important for understanding previously unknown features of bone fracture resistance.

Bone fractures cause serious problems for elderly people, especially those with osteoporosis. Bone fracture is one of the leading factors in decreasing quality of life for the elderly.

Measuring bone mineral density reveals how much bone a person has left. The amount of an individual's bone mineral density peaks around age 30, then decreases for the rest of his or her life. By the time a person becomes elderly, very serious bone loss may have occurred.

Moreover, the quality of bone will also decrease with the age, weakening the resistance against fracture. And the material properties of the bone are linked with the newly discovered molecular glue, noted the researchers.

"Not only is there less bone, but what exists is less strong. The cause of this is not well understood. Our research is aimed at understanding that," said Hansma.

Source: Xinhua