Artificial Joint Cartilage Mimics Structure and Function of Natural Tissue

Originally Published MDDI January 2002

R&D DIGEST

Artificial Joint Cartilage Mimics Structure and Function of Natural Tissue

Individuals afflicted with cartilage damage associated with joint injuries, congenital defects, arthritis, or age-related degeneration could benefit from the research of bioengineers at the University of California, San Diego (UCSD). The researchers say they have fabricated the first artificial cartilage tissue capable of simulating the multilayered structure and cellular functions of natural articular cartilage. The fabrication technique is described as a modified version of one developed at Rush-Presbyterian-St. Luke's Medical Center (Chicago).

According to Robert Sah, professor of bioengineering at the UCSD Jacobs School of Engineering and leader of the study, "We've designed a tissue made up of different types of juvenile cartilage cells with the notion that the tissue could be implanted into a patient and grow up to conform to the specific geometry of the individual's joint." He suggests that the next research phase will include animal studies to determine the efficacy of treatment using an implant made from the cartilage material.

Using data from earlier studies, the UCSD researchers developed a "map" for organizing different types of chondrocytes to mimic the stratified structure of cartilage tissue. This cell mixture was then grown using the alginate recovered chondrocyte method developed at Rush. This technique suspends cells in a gel until they begin to form their own matrix, or scaffolding. When the gel is removed, an entirely biological tissue remains.

Results of additional studies suggest that the cells at the surface of the engineered tissue effectively secreted a key molecule required for joint lubrication. Cells at the surface were also found to make tissue that was softer and had a less dense matrix, while the cells in deeper regions were spaced farther apart and had a more densely packed matrix that made the tissue stiffer.

The bioengineered tissue resembles immature cartilage, which the researchers believe will be beneficial because it will enable an implant to continue to spread out as cartilage does naturally in children. This will allow the implant to integrate well with surrounding cartilage and joint tissue. In contrast, mature cartilage is stiffer and less active.

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