Building Organs and Other Body Parts
Breaking a bone is never a pleasant experience – on top of the excruciating pain at the time of the accident, more pain and discomfort accompany the relatively long healing time. Nevertheless, bone is a “fortunate” body part to break: it does eventually get fixed, as opposed to other tissues in the body that do not heal at all, or may not regenerate fast enough to prevent death. One important example is cartilage, the hard part of the nose and ears. Cartilage also sits in between bones in the joints, and once it wears off, either because of ageing or from an injury, it will not grow back. This leads to a condition called osteoarthritis, caused by the contact between the bones in a joint, which leads to pain and stiffening of the limbs. Current treatments for osteoarthritis, such as a joint replacement, do not restore the original mobility to the joint. A new paradigm in medicine, called tissue engineering, has emerged in the past two decades as a solution to regenerate tissues that may heal too slowly, or not heal at all.
The idea behind tissue engineering consists in extracting cells from the injured person and growing them within a sponge-like material, called a cellular scaffold. This is generally made from types of biodegradable plastics that have been known for long to not provoke an immune response from the body. Sometimes it is even fabricated from natural materials like collagen, a protein which composes a large part of our body. The cells attach to the scaffold and proliferate, surviving and increasing in number. Eventually, these cells begin producing their own surrounding tissue, the extra-cellular matrix made of collagen and other proteins. At this point the cellular scaffold is inserted in the body, which recognizes it as its own and grows through it while the synthetic part slowly disappears, finally achieving complete regeneration of the natural tissue.
Tissue engineering, or regenerative medicine, has just made the news when a wheelchair-bound former firefighter was made to walk again. In this case, the scaffold was part of the man’s own body, extracted from the ankle and seeded with cells from the nose that are specialized in healing nerves. The scaffold was inserted in the damaged spinal cord of the patient and gradually regenerated the lesion, effectively curing paralysis for the first time and bringing hope to many other people whose quality of life has been significantly impacted by this condition. Other applications of tissue engineering have been out there for a while. For example, several patients have already successfully received transplanted, man-made bladders, which had been grown in a lab. Recently, a baby born without a wind pipe and forced to live in a hospital under intensive care for years was implanted with an artificial trachea containing her own cells. Finally, collagen skin grafts are regularly used to treat burn victims. These are all examples of tissues engineered to replace relatively simple parts of our bodies.
The natural complexity of most organs in our body makes it difficult to fabricate scaffolds that possess the same intricate arrangement of material. At the same time, reproducing the mechanical (flexibility, strength) and biological (material-cells interface) properties of natural tissues remains a challenge in many cases. Following fabrication, any new material needs to undergo through testing before being given approval for use on humans by the regulatory institutions involved. Yet, despite these complications, the potential of tissue engineering is clear, and the experts believe that through the next five to fifteen years our health care standards will change as a number of broken organs will be replaced with personal spare parts.