Discovered Protein ‘Glue’ in Bones Helps Prevent Fractures, Heal
Their research, and that of a Brazilian collaborator,
made the cover of a recent issue of the international journal Nature
Materials. Included with the article are the highest resolution
images of bone ever published, which reveal the location of the
adhesive or “glue” that holds together mineralized collagen fibrils
(protein fibers) of bone.
The glue appears to contain “springs” that uncoil
when the bone is stressed, helping the bone to absorb shock. The
springs return to their original structures when the stressed bone
The possible implications for human health are
important, explained Georg E. Fantner, a UCSB physics doctoral student
and first author of the report. “The findings may lead to therapy
for bone fracture, or even to prevention,” he said.
Working in the laboratory of physicist Paul K.
Hansma, in collaboration with the UCSB labs of molecular geneticist
Daniel E. Morse, and biochemist Galen D. Stucky, the interdisciplinary
group of scientists spent years tracking where the glue was located
in bone and how it worked.
“Before this research, it was well known that the
mechanical properties of bone depended on mineral particles and
on collagen fibrils,” said Hansma. “What we found is that there
is a glue in bone that holds these mineralized collagen fibrils
together. This glue involves sacrificial bonds (of hidden length)
that uncoil when the bone is stressed.”
This is “a fundamental and new discovery in an
old and well-studied field,” Hansma added.
Said co-author Morse, director of UCSB’s Institute
for Collaborative Biotechnologies: “It’s especially exciting for
us to find the profound medical significance of our discoveries
for human bone.” Six years ago, he described finding “molecular
shock absorbers” that provided a self-healing glue holding together
biological mineralized structures in the shells of abalone.
“It’s truly remarkable to find the same fundamental
mechanisms operating in bone,” said Morse.
He noted that these mechanisms give young, healthy
bone tremendous resiliency and resistance to fracture, and help
heal small microcracks soon after they’ve formed. “We’re especially
interested in learning how these molecules change and become depleted
with age as well as in certain diseases,” said Morse.
Hansma explained, “The thing that’s exciting about
this research is that we’ve identified a mechanically important
component of bone.” When the exact molecules are identified, these
can become therapeutic targets, for example, of diet or drug therapy.
Bone fracture is one of the leading factors in
a decreased quality of life for the elderly. “Less than one-third
of elderly women who have a hip fracture return to previous function,”
Hansma said. “More women die within a year of hip fracture than
die after a heart attack.”
And although bone is extensively studied, little
is known about how bone works at the molecular level. “Our paper
is the beginning research on this,” added Hansma.
In addition to Fantner, Hansma, Stucky and Morse,
co-authors from UCSB include Tue Hassenkam, Johannesh H. Kindt,
Leonid Pechenik, Jacqueline A. Cutroni, James C. Weaver, and Henrik
Birkedal. Geraldo A. G. Cidade of the Biophysics Institute Carlos
Chagas Filho at the Federal University of Rio de Janeiro also contributed.