generations of researchers have worked their way through to you. They have investigated every lead and every RUB meticulously and mapped. What, if not the bones, the basic structure of our body, were all of the short-lived medical Knowledge is a constant? But now it turns out that Our skeleton may consist of more than we have previously believed. Much more than this.
In the tibia bones of mice, scientists from Germany have discovered a new blood vessel system. In a network of fine tubules through the capillaries pull the bone cortex, and connect the bone marrow Inside the blood circulation. And this System is obviously tremendously important: the previously undiscovered tubules, the majority of the blood, this happens to the bones flows. The letter from the immunologist Matthias Gunzer, University of Duisburg-Essen and his colleagues in the journal “Nature Metabolism”.
On the field of battle drugs work in seconds
the Long tubular bones such as the tibia or humerus consist of several layers. The whole of the outside, the periosteum, the periosteum of the Os (=lat. Bone). Inside the bone cortex, and finally the marrow cavity close to a sponge and the finest bone trabeculae, in the microscopic cavities of the bone marrow is located. There are formed when people from the fourth month of life, almost all of the blood cells. Accordingly, it is also supplied with blood. Previously, scientists assumed that only a few arteries supply the bone marrow with nutrients and also a few veins, flooding the blood cells in the systemic circulation. The vessels need to penetrate the hard outer layer of the bone. Most of these blood vessels are located at the ends of bone, a few in the middle, on the bone shaft.
“There was evidence from previous studies that there must be in addition to these few blood vessels yet another System, the the bones pulls through”, says Matthias Gunzer, head author of the study, day-to-day level.
This theory came recently from observations on the field of battle. The wounded soldiers, whose veins are not good enough to, as the Doctors administer an injection could you get this directly in the bone injected. The required fluid or medication to be injected with a steel cannula into the tibia. In the meantime, this intraosseous injection operations is a common practice not only in Wars, but also in the case of Emergency. The effect of the medication, often after only seconds. So it had to be a way, how the materials arrive quickly from the bone marrow into the bloodstream, acts as a kind of shortcut through the bone case. Previously, such structures could, however, with no technology to prove. Gunzer and his colleagues have now found a suitable method of making the bone just transparent.
The idea is that the bones simply transparent
is called Clearing. By Inserting in a solution of the fat-containing cell membranes are, as it were, washed away, the view to the underlying structures. Whole organs can investigate, “but the bone was because of its hard outer layer is a very difficult task”, says Gunzer. What is crucial is the addition of a colorless liquid called cinnamic acid ethyl ester – a compound that is actually approved as a fragrance for Christmas cookies. Inserted in such a solution, the bony exterior of the mouse skin glass bones within a day and gave views of the Interior of the bone. With a new method of x-Ray microscopy, the researchers were able to create on a Computer a three-dimensional Image of the mouse vascular system.
in addition to the already well-known supply vessels, the scientists found tiny capillaries, which is moved perpendicular to the bone case. Connect the bone marrow directly with the vessels on the outer side of the bone. They found up to a Thousand of these tubules in a single bone. “And since we are talking of a mouse bone, which is roughly the size of a matchstick,” says Gunzer. Because the fine tubules pass through the bone shell, the cortical bone, called Gunzer and his colleagues, they TRANS-cortical vessels (TCVs).
Through the TCVs, the majority of the blood
flows With a microscope, the researchers measured the blood flow through individual TCVs and were expecting the result. “Through the vessels, about 80 percent of the arterial and almost 60 percent of the venous blood flow in the mice,” says Gunzer. Apparently, the channels have with the mouse so a Central function. One of them could be to bring in the bone marrow formed of inflammatory cells quickly on the spot. The scientists in mice that were artificially to rheumatoid Arthritis develop in people with frequent joint inflammation observed. Within a few weeks, the number of TCVs to be increased massively. It is the researchers to observe immune cells in their migration through the capillaries.
By means of light sheet microscopy combined with a green blood vessel staining, the researchers were able to the blood vessels in the bones…source: Anja Hasenberg/University of Duisburg-Essen
So that you can grow through the compact bone, for each of the vessels a tiny channel through the hard outer skin of the bone is required: These channels have to Gunzers measurements, a diameter of about 10 to 15 micro-meters and more than 100 micro-meters in length. Be bored by osteoclasts – bone degrading cells, which play also at the osteoporosis has a role.
The big question is whether there is this System of vessels in humans. “Human bones are built much more complicated than mice,” says Gunzer. Unlike the rodents of the man in the broad bone cortex already has a System of the smallest vertical and horizontal canaliculi. But none of them by the bark extracts completely – how TCVs. For the presence of the people, in turn, is some evidence.
The Professor under the own tibia
After injuries, long bone, such as a broken leg, seemed to have sought out surgeons to observe again and again the smallest spot-like hemorrhages beneath the periosteum. “You could be the exit points of the TCVs,” says Gunzer. Because the is not fit to be alone of course, as evidence, put the Professor, his leg seemed to be for hours under a 7-Tesla MRI, the recordings of the blood flow in his bones. Also here are notes on the smallest of Openings in the bone cortex. The ultimate proof would be but of course, if you could be the channels themselves. Since human bones are too thick to make it by means of Clearing-method transparent, the researchers not only to examine bone fragments, in this case those from the femoral neck of patients from the trauma surgery. And in fact, they discovered the vessels that were the TCVs are structurally very similar, even if they were thicker than those in mice. “Our results suggest that also human bones, at least in some regions, over such a connection, the tubules have”, says Gunzer.
According to the pride of the researchers: “in addition to the fact that in the 21st century. Century not every day a new anatomical structure, we now have a completely new concept of how the blood supply in long bones vessel looks like.” As a possible beginning of a new Era of bone biology, the work also looks Jan Tuckermann, Director of the Institute for Molecular endocrinology at the University of Ulm. “It has been found for the first Time in cortical bone is a dynamic vascular network, the changes in both inflammation as well as in fractures.”
“We must learn to understand the network better now”
The discovery could be, so you could really transmitted to humans, is of great importance. “By regulating the blood flow in the bone with medication, could affect various aspects of bone biology, such as the process of osteoporosis, or repair after an injury,” says Tucker man. Gunter goes even further: “We would not perhaps understand for the first time properly, what happens during a bone marrow transplant”. If, for example, the stem cells of the recipient from the blood to immigrate circulation to the bone marrow, could play the TCVs a role. Also, some types of cancer secondary growths form in the skeleton. Also, you could use the capillaries to reach the bone and proliferate there. “If we know how this works, we can prevent it, perhaps one day”, says Gunzer.
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stem cells and osteoporosis young bone
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First, you must learn the network now but it is better to understand, says Tucker man. You must demonstrate the extent to which it really exists in humans. Tomography with even better resolution could be the method of choice. And it could be that not only the long tube to hide bones more than science has previously assumed. Recently a group of researchers at Harvard University had demonstrated the existence of similar tubules in the cranial bone of mice. The microscopic structures that connect the outer side of the skull directly to the brain surface. So maybe the Chapter is “the skeletal system needs to be rewritten” in the anatomy books in the not-too-distant future.
