"As opposed to a single value, our data indicate that normal bone contains a distribution of collagen fibril spacings," Wallace said.
Next, the team wanted to know if the distribution of fibril spacings differed in bone from healthy and diseased individuals. To address that question, they collaborated with Clifford Les of Henry Ford Hospital, who has been studying how bone changes when estrogen wanes, as it does in menopause. To model the age-related estrogen depletion that occurs in humans, Les uses sheep that have had their ovaries removed. The sheep exhibit some of the same symptoms as menopausal women, and they undergo some bone remodeling, but they don't develop osteoporosis.
When the researchers compared bone from normal and ovariectomized sheep, they found striking differences in fibril spacing distributions, suggesting that estrogen depletion has a significant effect on the spacing.
"This ability to measure fibril spacing and to distinguish between normal and diseased bone not only gives us a powerful method to study the mechanism of disease at the nanoscale, but it also has important implications to the future diagnosis of disease in bone and perhaps other collagenous tissues," said Banaszak Holl. "Collagen is the most common protein in the mammalian body. It's in bones, teeth, tendons, skin, arteries. We basically don't work well when it's not working well, so there are many diseases related to problems with collagen. We're very excited about developing this method as a diagnostic for all kinds of diseases of structural collagen."
The technique could be a powerful complement to the current gold standard for diagnosing osteoporosis: measuring bone mineral density (BMD) with dual energy X-ray absorptiometry (DEXA). Although widely used, DEXA isn't ideal, because
|Contact: Nancy Ross-Flanigan|
University of Michigan