Biomedical Engineering

Athanasiou Receives Large R01 Grant to Improve Engineered Cartilage for TMJ

Jaw x-ray.

Kyriacos Athanasiou has received an R01 to refine his tissue engineered cartilage for use to treat the temporomandibular meniscus and mandibular cartilage surfaces. He will receive $1.4 million over the next four years for the project, “Regenerating the fibrocartilage spectrum of the TMJ: from disc to condyle.” The award began on Oct. 5, 2010.

Following trauma (such as sports injuries) or pathologic affliction (such as osteoarthritis), cartilage cannot heal itself in a way that allows it to function properly under its strenuous and biomechanically difficult environment. Professor Athanasiou uses adult stem cells from bone marrow and skin as well as human embryonic stem cells, to grow cartilage tissue in the lab. The new R01 will further his experiments with various chemical and mechanical stimuli to improve its properties.

“Afflictions of the jaw joint or TMJ are complex and unresolved despite the fact that they reduce a patient’s quality of life significantly.  After all, the jaw joint controls important daily activities, such as eating and talking, and it also is a significant component of one’s appearance.  Almost 90% of these afflictions are primarily found in young, pre-menopausal women for reasons that are still not understood,” says Dr. Athanasiou.

Tissue engineered cartilage from Dr. Athanasiou's Lab.

Successful generation of biomimetic fibrocartilage would be a great stride toward the treatment of injuries or degeneration of the TMJ meniscus and mandibular cartilage surfaces, but much needs to be accomplished before this goal can be reached. Native fibrocartilages contain a variety of compositional and mechanical properties. Thus, a range of engineered tissues need to be developed.

“Central to jaw problems is destruction of the various types of fibrocartilage that are found in the joint.  We are proposing to  tissue engineer a spectrum of fibrocartilage types using approaches that we have developed using principles of regenerative medicine,” Dr. Athanasiou explains.

Dr. Jerry Hu, a scientific Co-Investigator and collaborator on this project, says that “in the course of identifying the optimal chondroitinase ABC, growth factor, and mechanical stimulation treatments, one for each of three cell ratio groups, this proposal will yield insight into the process of generating a spectrum of fibrocartilages with varying mechanical and compositional properties, biomimetically recreating the range of properties seen in the TMJ fibrocartilages.” Microarray analysis will elucidate the roles of these exogenous stimuli. Finally, the engineered constructs will be implanted in the nude mouse to examine viability and stability. The technologies generated by this proposal can then be applied not only to tissue engineering other fibrocartilaginous systems (e.g., knee meniscus) as well.

The National Institutes of Health awards R01 grants to institutions to provide support for health-related research and development. It funds individual, clearly defined and limited studies performed by an investigator within his or her particular area of expertise. Unlike many other grants, R01s can be renewed, allowing scientists to continue a particular line of investigation over a longer period of time.

“I would like to highlight the fact that UC Davis, in general, and our department of Biomedical Engineering, in particular, exhibit exceptional strengths in regenerative medicine.  We are fortunate to be able to establish collaborative teams from Engineering, Medicine, Veterinary Medicine, and Biological Sciences to address one of the most vexing problems of regenerative medicine. Our group is in the good position of having support from the National Institutes of Health using the R01 funding mechanism for our work in tissue engineering of articular cartilage, the knee meniscus, the TMJ disc, and now TMJ fibrocartilages,” Dr. Athanasiou says.

TMJ disc, knee meniscus, articular cartilage and chondrogenically-differentiated hESCs engineered in Dr. Athanasiou's lab.

Project Details

Public Health Relevance statement:

Successful generation of biomimetic fibrocartilage would be a great stride toward the treatment of injuries or degeneration of the TMJ meniscus and mandibular cartilage surfaces, but much needs to be accomplished before this goal can be reached. The compositional and mechanical property heterogeneity of native fibrocartilages, further mirrored in their varying functions, necessitates development of a range of tissues for regeneration. In the course of identifying the optimal chondroitinase ABC, growth factor, and mechanical stimulation treatments, one for each of three cell ratio groups, this proposal will yield insight into the process of generating a spectrum of fibrocartilages with varying mechanical and compositional properties, biomimetically recreating the range of properties seen in the TMJ fibrocartilages. Furthermore, microarray analysis will elucidate the roles of these exogenous stimuli. The viability and stability of the engineered constructs will also be investigated in an immunodeficient animal model. The enabling technologies generated by this proposal can then be applied not only to tissue engineering one particular region of the TMJ meniscus or mandibular cartilage, but also to other fibrocartilaginous systems (e.g., knee meniscus) as well.

Project Description:

The objective of this design-driven proposal is to optimize and employ scaffold-free co-cultures for the generation of biomimetic fibrocartilages for the repair or replacement of the temporomandibular joint meniscus and the mandibular cartilage surfaces. Using co-cultures of fibrochondrocytes and articular chondrocytes, we recently generated large constructs of clinically relevant dimensions that were fibrocartilage-like in appearance and composed of extracellular matrix (ECM) suggestive of fibrocartilage. Moreover, constructs similar to native tissue were achieved with fibrochondrocytes. Motivated by these findings, it is our hypothesis that the cocultures can be optimized using bioactive agents and mechanical stimuli to form biomimetic fibrocartilage constructs. To address this hypothesis, we propose the following specific aims: 1) to optimize the use of chondroitinase ABC and the growth factors transforming growth factor -1 (TGF-1) and insulin-like growth factor 1 (IGF-I) using serum-containing medium or chemically defined medium in the scaffold-free co-culture of fibrocartilage; 2) to enhance the biomimetic fibrocartilage constructs with mechanical stimulation; and 3) to examine synergistic effects of bioactive agents and mechanical stimuli. Chondroitinase ABC has been found in preliminary studies to significantly increase construct tensile properties. Our group has also demonstrated that TGF-1 and IGF-I significantly increase ECM production in fibrocartilage constructs. The use of hydrostatic pressure and direct compression stimulation has been shown by our laboratory to have beneficial effects on articular cartilage and fibrocartilage constructs, and we will apply these stimuli individually and in combination to further enhance the constructs. Constructs will be examined histologically for glycosaminoglycan (GAG) and collagen, and immunohistochemically for collagen I and II. GAG, collagen, and DNA content will be quantified, followed by ELISA to measure collagen I and II. Biomechanical evaluation will include compression, tension, and creep indentation testing. Furthermore, microarray analysis will be used to study potential synergisms that may arise in the use of the exogenous stimuli. Finally, the engineered constructs will be implanted in the nude mouse to examine viability and stability.

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