 Dr. Szivek is using small, plastic scaffolds to grow replacement tissues for damaged joints. |
Scientists at The University of Arizona College of Medicine are investigating a potential new way to help patients with arthritis who normally would have total-joint replacement.
Since the first joint-replacement procedures more than 40 years ago, damaged knees, hips, shoulders and other joints have been repaired with a variety of durable materials, including ceramics, metals and plastics. Instead of replacing damaged joints with these materials, John A. Szivek, PhD, and his team of researchers are working on growing replacement tissues in his laboratory. These tissues, which are grown from the patient's cells, are grown on a plastic that will begin to dissolve after a year in the patient's body. Dr. Szivek is a professor in the UA Department of Orthopaedic Surgery, director of the Orthopaedic Research Lab and a senior scientist at the Arizona Arthritis Center. With a $1.1 million grant awarded in 2002 by the National Institutes of Health and an additional $368,000 grant from the National Science Foundation, he and members of the UA Department of Orthopaedic Surgery and the UA Biomedical Engineering Interdisciplinary Program have been developing technology to grow new cartilage tissue to replace damaged joints and to actively monitor loading on the joints when patients exercise. |
One key component of the research is a high-tech plastic carrier, or scaffold. Designed to support the growth of new bone and cartilage, the scaffold also carries the load-sensing devices and the radio transmitter that allows researchers to monitor the new tissue's response to load.
The scaffold will be placed into the joint to be repaired, Dr. Szivek explains. It is manufactured using a highly sophisticated imaging device that scans the bone in tiny increments of just one one-hundredth of a millimeter. These exact measurements of the bone are relayed to a rapid prototyping machine that builds the scaffold, making it the exact shape of the patient's bone. When placed, the scaffold, which is porous on the inside, allows new bone tissue to grow into it.
The top of the scaffold is rounded to support the growth of new cartilage in the lab, and the rounded shape will conform to the surface of the patient's joint. After a year, the plastic device will begin to dissolve, eventually leaving only the new tissue.
Dr. Szivek currently is concentrating on two aspects of the project. One is the telemetry, or data-transmission process. "We are the only people in the world working with the sensor technology," he says. "We have developed the software that allows us to collect data and transmit it to a Palm device, rather than a desktop or laptop computer. But we need a faster, more powerful hand-held computer to collect the measurements. We currently are able to collect measurements with an existing Palm device but will be writing code for a hand-held computer running a Windows operating system that has more functionality and memory."
The other major focus this year is growing cartilage tissue from various types of cells. "The bone will grow into the scaffold by itself once the scaffold is in the patient," Dr. Szivek says. "However, we must grow the cartilage tissue in the lab before we implant it into the patient." The process currently requires removing a small piece of cartilage from the patient's affected joint, under anesthesia, and extracting cells in the lab in order to grow new tissue on the scaffold. Unlike the cartilage in a person's ear or nose, "hyaline articular cartilage" - the cartilage that protects bone in joints - is complex and highly structured. It consists of three layers of cells and tissue, with the cells distributed differently in each. The cells do not divide or reproduce readily. If tissue forms, it forms very slowly.
This summer, Dr. Szivek is taking a new approach to the problem. He is hoping to grow cartilage tissue from the stem cells in fat, converting them to cartilage cells with the addition of proteins. "I have hopes that these cells will be easier to work with than cartilage cells," he says. "There are several advantages. One is the availability - everyone has enough fat to do this, and harvesting fat from a patient is a relatively simple procedure that is done under a local anesthetic. There are no problems with tissue rejection, as the cells come from the same patient we plan to implant the tissue into, and there are no embryonic stem cell issues."
While it is likely to be several years before this technology is ready for clinical applications, it could replace artificial-joint surgery for arthritis patients and others whose cartilage has been damaged through trauma or sports, restoring the joint to more normal function. It also will enable health-care professionals to monitor patients during rehabilitation as well as providing an alert mechanism for patients if they overload their tissue-engineered cartilage.
For more information, please contact the Department of Orthopaedic Surgery, (520) 626-4024, or the Arizona Arthritis Center at The University of Arizona, (520) 626-5026.
