Embryonic stem cells used to grow cartilage

Rice method is first to yield cartilage-like cells, engineer human cartilage

HOUSTON, Sept. 6, 2007 – Rice University biomedical engineers have developed a new technique for growing cartilage from human embryonic stem cells, a method that could be used to grow replacement cartilage for the surgical repair of knee, jaw, hip, and other joints.

“Because native cartilage is unable to heal itself, researchers have long looked for ways to grow replacement cartilage in the lab that could be used to surgically repair injuries,” said lead researcher Kyriacos A. Athanasiou, the Karl F. Hasselmann Professor of Bioengineering. “This research offers a novel approach for producing cartilage-like cells from embryonic stem cells, and it also presents the first method to use such cells to engineer cartilage tissue with significant functional properties.”

The results are available online and slated to appear in the September issue of the journal Stem Cells. The study involved cells from an NIH-sanctioned stem cell line.

Using a series of stimuli, the researchers developed a method of converting the stem cells into cartilage cells. Building upon this work, the researchers then developed a process for using the cartilage cells to make cartilage tissue. The results show that cartilages can be generated that mimic the different types of cartilage found in the human body, such as hyaline articular cartilage — the type of cartilage found in all joints — and fibrocartilage — a type found in the knee meniscus and the jaw joint. Athanasiou said the results are exciting, as they suggest that similar methods may be used to convert the stem cell-derived cartilage cells into robust cartilage sections that can be of clinical usefulness.

Tissue engineers, like those in Athanasiou’s research group, are attempting to unlock the secrets of the human body’s regenerative system to find new ways of growing replacement tissues like muscle, skin, bone and cartilage. Athanasiou’s Musculoskeletal Bioengineering Laboratory at Rice University specializes in growing cartilage tissues.

The idea behind using stem cells for tissue engineering is that these primordial cells have the ability to become more than one type of cell. In all people, there are many types of “adult” stem cells at work. Adult stem cells can replace the blood, bone, skin and other tissues in the body. Stem cells become specific cells based upon a complex series of chemical and biomechanical cues, signals that scientists are just now starting to understand.

Unlike adult stem cells, which can become only a limited number of cell types, embryonic stem cells can theoretically become any type of cell in the human body.

Athanasiou’s group has been one of the most successful in the world at studying cartilage cells and, especially, engineering cartilage tissues. He said that for his research the primary advantage that embryonic stem cells have over adult stem cells is their ability to remain malleable.

“Identifying a readily available cell source has been a major obstacle in cartilage engineering,” Athanasiou said. “We know how to convert adult stem cells into cartilage-like cells. The more problematic issue comes in trying to maintain a ready stock of adult stem cells to work with. These cells have a strong tendency to convert from stem cells into a more specific type of cell, so the clock is always ticking when we work with them.”

By contrast, Athanasiou said his research group has found it easier to grow and maintain a stock of embryonic stem cells. Nonetheless, he is quick to point out that there is no clear choice about which type of stem cell works best for cartilage engineering.

“We don’t know the answer to that,” Athanasiou said. “It’s extremely important that we study all potential cell candidates, and then compare and contrast those studies to find out which works best and under what conditions. Keep in mind that these processes are very complicated, so it may well be that different types of cells work best in different situations.”

Athanasiou began studying embryonic stem cells in 2005. Since funding for the program was limited, he asked two new graduate students in his group if they were interested in pursuing the work as a secondary project to their primary research. Those students, Eugene Koay and Gwen Hoben, are co-authors of the newly published study. Both are enrolled in the Baylor College of Medicine Medical Scientist Training Program, a joint program that allows students to concurrently earn their medical degree from Baylor while undertaking Ph.D. studies at Rice.

“Eugene and Gwen are both outstanding students,” Athanasiou said. “Each earned their undergraduate degree from Rice and each worked in my laboratory as undergraduate students. They have chosen to do this research because they think this may represent the future of regenerative medicine.”

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The research was funded by Rice University.

Contact: Jade Boyd
jadeboyd@rice.edu
713-348-6778
Rice University

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US soldiers in Iraq fighting drug-resistant bacteria after injuries

Contact: Amy Jenkins
amy@jenkinspr.com
312-836-0613
University of Chicago Press Journals

ALEXANDRIA, Va. — US soldiers in Iraq do not carry the bacteria responsible for difficult-to-treat wound infections found in military hospitals treating soldiers wounded in Iraq, according to an article to be published electronically on Wednesday, May 16, 2007, in Infection Control and Hospital Epidemiology. The article will appear in the June issue of the journal.

Investigator Matthew E. Griffith, MD, (Brooke Army Medical Center at Fort Sam Houston, San Antonio, Texas) and colleagues found that drug-resistant strains of Acinetobacter calcoaceticus-baumannii complex are not present on the skin of uninjured soldiers in Iraq, as had been expected.

A. calcoaceticus-baumannii complex is an important cause of trauma-associated and hospital-acquired infection throughout the world, and multidrug-resistant strains of the bacteria have been infecting injured soldiers treated in US military hospitals in Iraq.

“We need to know where these infections are coming from,” explains Dr. Griffith. “One of the possibilities was that A. calcoaceticus-baumannii was on the soldiers’ skin before injury and simply traveled to the wound site to cause the infection. However, our research shows that this is not the case.”

Although the consequences of the outbreak A. calcoaceticus-baumannii infection in US military hospitals serving soldiers wounded in Iraq are well described, the source of the outbreak is unknown.

To determine whether A. calcoaceticus-baumannii complex is carried on the skin of healthy US Army soldiers, investigators cultured skin swab specimens from 102 active military soldiers stationed at a base in Iraq. The base is in an environment representative of all Iraqi environments with desert, irrigated farmland and an urban area nearby.

Several previous reports have described skin carriage of Acinetobacter species in healthy people. The carriage rates have been found to vary with climate and geography. These reports may not be generalizable to US Army soldiers in Iraq, which has an extremely dry climate.

“If skin carriage is not the source of A. calcoaceticus-baumannii complex infection, then the other possibility is that the bacteria contaminates the wounds after injury,” explains Dr. Griffith. “This could happen while an injured soldier is awaiting treatment or in the hospital during or after receiving medical care.”

“This observation refutes the concept that the bacterium is acquired prior to injury among soldiers deployed to Iraq,” Dr. Griffith says. “In addition, this observation adds to the ever growing body of evidence implicating nosocomial transmission as the cause of the ongoing military outbreak.”

Because of this and similar research, an increased emphasis on infection control has been put in place in the US military’s combat hospitals.

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Infection Control and Hospital Epidemiology provides original, peer-reviewed scientific articles for anyone involved with an infection control or epidemiology program in a hospital or healthcare facility. Written by infection control practitioners and epidemiologists and guided by an editorial board composed of the nation’s leaders in the field, ICHE provides a critical forum for this vital information.

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