Have you ever had the thought of living forever, the hope of being as young and energetic as you are now forty years down the line, or a desire to be free from the pain of a long, hard day? As we trudge through the physical hardships of our daily lives, we create a great deal of stress, and consequently a great deal of pain. This pain can often be felt in the bones and cartilage of our bodies. For some, the pressure creates deleterious effects that can impinge the quality of life in future years. For others, being born with a genetic disease or deformity imposes an obstacle in leading a normal life. From bone fractures, osteoarthritis, or even congenital diseases such as limb deformities or craniofacial anomalies, we hope to one day fully restore these abnormalities to their proper states. Tissue engineering plays a major role in this endeavor, and researchers from the University of Illinois at Chicago, in particular, are exploring the many ways in which tissue engineering can improve and potentially save human lives.

Tissue engineering of bone and cartilage is an ongoing mission for researchers at UIC. Dr. Jeremy Mao, Director and Clinical Associate Professor of the UIC Department of Orthodontics, has several current projects. Various approaches are used in his research, including the use of mesenchymal stem cells, mechanical stimuli, and an understanding of the expression of different genes in bone and cartilage tissues.

Mesenchymal stem cells can be used in different engineering constructs to replace defects caused by trauma or congenital defects in bone and cartilage. Mesenchymal stem cells are the progenitor cells for virtually all connective tissue components such as bone, cartilage, skin, dentin, and cementum. They reside in the bone marrow of adult mammals, including adult humans. These stem cells are easily extracted, thus avoiding the controversial extraction procedure present with embryonic stem cells. After a rather uncomplicated procedure of repeated cell culture, the use of growth factors, such as bone mocogenetic proteins or TGFâ, will induce these embryonic progenitor cells to grow, with the potential for numerous differentiations, into cells of tissues such as bone and cartilage.

Due to the nature of bone and cartilage tissues, which are designed to withstand mechanical forces, Dr. Mao is a strong believer that "mechanical stimuli will play a critical role in tissue engineering." The purpose of mechanical stimuli is to induce bone and cartilage formation by bypassing the stem cell stage completely. What is involved is subjecting tissue or an organ to mechanical forces of different characteristics on a daily set schedule for a period of time. An advantage of using this technique is that it can be used in vivo and can induce chrondrogenesis and osteogenesis without even causing trauma in the patient. Another benefit is that it is not dependent on the supply of bone and cartilage tissues if there were ever a shortage. The use of mechanical stimuli is not a new procedure as it already has an extensive history in orthopedic medicine as well as in many dental procedures. A paper published in Nature on August 9, 2001 discovered that applying mechanical stimuli to the femur of sheep increased the density of the bone by 34.2%. The paper claims, as an applicable benefit for humans, that there is potential for treatment of crippling disorders such as osteoporosis.

An additional approach to the tissue engineering of bone and cartilage is through understanding the expression of various genes in the tissues. In this method, insight into the fundamental mechanisms that are responsible for what we see in tissue engineering is possible. Dr. Mao's team is interested in several molecules and their genes, such as tissue metiloproteases and protoenzymes, and in particular, mapping out the expression of these genes. This would then allow them to see how they could pursue either the tissue engineering approach or the biomechanical approach of the engineering of bone and cartilage.

Tissue engineering has come a long way since its original debut over three decades ago. The field now is at a stage where tissue engineered skin has made its way to the market. In many publications such as Nature, Scientific American, and Time, it is predicted that the next breakthrough in tissue engineering will take place in the context of bone and cartilage. These tissues are more easily recreated in a scientific setting as opposed to the more complex tissues of organs, which involve complicated procedures as well as utilizing technology that is not available. With the breakthrough in bone and cartilage engineering, many people will be able to receive treatment and improve ailments. Perhaps in the future, a long, hard day will not seem nearly as long and hard, individuals will feel much younger than they actually are, and even if not forever, the thought of living longer with less complications will be a genuine possibility.

James is a third-year student majoring in biological sciences. He plans to enter the field of dentistry.