Bad to the bone: UD research to shed light on os...(can tell whether a person is using his o...),Health

Date:11/15/2007

can tell whether a person is using his or her bones or not. If the person is physically active, the osteocytes tell cells on the surface that it's okay to put on more bone. Otherwise, they signal the surface cells to remove bone at a rate that can be as high as 3 percent bone mass per month, which is the case for patients confined to long-term bed rest and for astronauts, she notes.

The osteocytes lie in tiny pits or holes, called lacunae, within the bone. These living cells have many long arms that connect them to surface bone cells and the bone's vascular system. The narrow channels housing the osteocyte's arms (canaliculi) and the lacunae form a network through which a mixture of water, nutrients and other bioactive molecules flows.

Although it is hard as cement, bone is actually like a stiff sponge, Wang says. It's porous and has water inside. When we have mechanical loading, when you run, for example, a part of the leg bone is compressed, and water is pushed through gaps, less than a micrometer in size, between the osteocytes and the bone cement that surrounds them.

This powerful wave of fluid keeps the osteocytes happy and functioning well, Wang says, delivering nutrients to them from nearby blood vessels and quickly dispersing signaling molecules, such as calcium ions, from one cell to its neighbors.

Using a novel microscopic imaging method that Wang developed, which is based on fluorescence recovery after photobleaching (FRAP), the research team hopes to do what no one has done before: see inside living bone and determine how rapidly these signaling and nutrient molecules are transferred between the cells when a bone is at rest and when it is at work.

A high-powered laser-scanning microscope will be used to assess the movement of molecules in the tibia of an anesthetized mouse. A harmless green fluorescent dye, tagged to various-sized proteins, signaling molecules and cell nutrients, will be injected into the animal's
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Contact: Tracey Bryant tbryant@udel.edu 302-831-8185 University of Delaware   Source:Eurekalert

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