Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Reversal cells may tip the balance between bone formation and resorption in health and disease

06.06.2013
Investigators report on a possible 'missing link' in The American Journal of Pathology

By analyzing biopsy specimens from patients with postmenopausal osteoporosis and primary hyperparathyroidism, investigators have begun to pay increasing attention to "reversal cells," which prepare for bone formation during bone remodeling.

The hope is that these reversal cells will become critical therapeutic targets that may someday prevent osteoporosis and other bone disorders. This study is published in the July 2013 issue of The American Journal of Pathology.

In adults, bones are maintained healthy by a constant remodeling of the bone matrix. This bone remodeling consists of bone resorption by osteoclasts and bone formation by osteoblasts. A failure in the delicate balance between these two processes leads to pathologies such as osteoporosis. How these two processes are coupled together is poorly understood.

"Reversal cells may represent the missing link necessary to understand coupling between bone resorption and formation and to prevent osteoporosis," says Jean-Marie Delaisse, PhD, professor of clinical cell biology at the Institute of Regional Health Services Research at the University of Southern Denmark and Vejle-Lillebaelt Hospital in Vejle.

Reversal cells actually cover more than 80% of the resorbed bone surfaces. Using histomorphometry and immunohistochemistry on human bone biopsies, researchers found that the reversal cells colonizing the resorbed bone surfaces are immature osteoblastic cells which gradually mature into bone forming osteoblasts during the reversal phase, and prepare the bone surface for bone formation.

Researchers also found that some reversal cells display characteristics that suggest an "arrested" physiological status. These arrested reversal cells showed no physical connection with bone forming surfaces, a reduced cellular density, and a reduced expression of osteoblastic markers.

Biopsies from postmenopausal patients with osteoporosis showed a high proportion of arrested cells, but no such cells were found in biopsies from patients with primary hyperparathyroidism, in which the transition between bone resorption and formation is known to occur optimally. Negative correlations were found between the proportion of arrested cells in biopsies from patients with osteoporosis and trabecular bone volume or bone formation parameters.

In other words, larger arrested cell surfaces were associated with bone loss. Other findings suggest that the reversal phase is longer in those with postmenopausal osteoporosis compared to those with primary hyperparathyroidism.

Investigators describe three concurrent types of bone remodeling cycles. Their respective prevalence depends on the pathophysiological situation.

All bone remodeling processes start with bone resorption, but differ by the degree of restitution of the bone matrix. In coupled and balanced bone remodeling, the bone matrix is completely restituted as primarily observed in healthy and primary hyperparathyroidism bone. In coupled and unbalanced bone remodeling, bone formation occurs, but the resorbed cavity is not completely restituted. In uncoupled bone remodeling, the resorbed cavity remains completely unfilled, as an arrest of the reversal phase, with no new bone formation. Coupled and unbalanced bone remodeling and uncoupled bone remodeling both appear to contribute to bone loss in osteoporosis.

"Our observations suggest that arrested reversal cells reflect aborted remodeling cycles which did not progress to the bone formation step," says Dr. Delaisse. "We therefore propose that bone loss in postmenopausal osteoporosis does not only result from a failure of bone formation as commonly believed, leading to incomplete filling of resorption cavities, but also from a failure at the reversal phase, uncoupling bone formation from resorption."

David Sampson | EurekAlert!
Further information:
http://www.elsevier.com

More articles from Health and Medicine:

nachricht Team discovers how bacteria exploit a chink in the body's armor
20.01.2017 | University of Illinois at Urbana-Champaign

nachricht Rabies viruses reveal wiring in transparent brains
19.01.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Bodyguards in the gut have a chemical weapon

20.01.2017 | Life Sciences

SF State astronomer searches for signs of life on Wolf 1061 exoplanet

20.01.2017 | Physics and Astronomy

Treated carbon pulls radioactive elements from water

20.01.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>