Genetic variations-mutations that affect drug receptors, pathways and metabolizing enzymes-are thought to underlie most of the racial, ethnic and geographic differences in drug response, making the field ripe for biotech-style personalized medicine. NitroMed, for example, is collecting genetic material with the hope of developing a test to identify all patients-irrespective of race-likely to respond to BiDil®.
Some companies are exploring the concept of gender-based medicine to take into account the differences in male and female response to medicine. Aspirin, for example, prevents heart attacks in men but not in women. At least one biotech company is developing a lung cancer drug that shows greater promise in women.
Biotechnology permits the use of the human body's natural capacity to repair and maintain itself. The body's toolbox for self-repair and maintenance includes many different proteins and various populations of stem cells that have the capacity to cure diseases, repair injuries and reverse age-related wear and tear.
Tissue engineering combines advances in cell biology and materials science, allowing us to create semi-synthetic tissues and organs in the lab. These tissues consist of biocompatible scaffolding material, which eventually degrades and is absorbed, plus living cells grown using cell culture techniques. Ultimately the goal is to create whole organs consisting of different tissue types to replace diseased or injured organs.
The most basic forms of tissue engineering use natural biological materials, such as collagen, for scaffolding. For example, two-layer skin is made by infiltrating a collagen gel with connective tissue cells, then creating the outer skin with a layer of tougher protective cells. In other methods, rigid scaffolding, made of a synthetic polymer, is shaped and then placed in the body where new tissue is needed. Other synthetic polymers, made from natural compounds, create flexible scaffolding more appropriate for soft-tissue structures, like blood vessels and bladders. When the scaffolding is placed in the body, adjacent cells invade it. At other times, the biodegradable implant is seeded with cells grown in the laboratory prior to implantation.
Simple tissues, such as skin and cartilage, were the first to be engineered successfully. Recently, however, physicians have achieved remarkable results with a biohybrid kidney that maintains patients with acute renal failure until the injured kidney repairs itself. A group of patients with only a 10 to 20 percent probability of survival regained normal kidney function and left the hospital in good health because the hybrid kidney prevented the events that typically follow kidney failure: infection, sepsis and multi-organ failure. The hybrid kidney is made of hollow tubes seeded with kidney stem cells that proliferate until they line the tube's inner wall. These cells develop into the type of kidney cell that releases hormones and is involved with filtration and transportation. In addition to carrying out these expected metabolic functions, the cells in the hybrid kidney also responded to signals produced by the patient's other organs and tissues.
The human body produces an array of small proteins known as growth factors that promote cell growth, stimulate cell division and, in some cases, guide cell differentiation. These natural regenerative proteins can be used to help wounds heal, regenerate injured tissue and advance the development of tissue engineering described in earlier sections. As proteins, they are prime candidates for large-scale production by transgenic organisms, which would enable their use as therapeutic agents.
Some of the most common growth factors are epidermal growth factor, which stimulates skin cell division and could be used to encourage wound healing; erythropoietin, which stimulates the formation of red blood cells and was one of the first biotechnology products; fibroblast growth factor, which stimulates cell growth and has been effective in healing burns, ulcers and bone and growing new blood vessels in patients with blocked coronary arteries; transforming growth factor-beta, which helps fetal cells differentiate into different tissue types and triggers the formation of new tissue in adults; and nerve growth factors, which encourage nerve cells to grow, repair damage and could be used in patients with head and spinal cord injuries or degenerative diseases such as Alzheimer's Disease.
Vaccines help the body recognize and fight infectious diseases. Conventional vaccines use weakened or killed forms of a virus or bacteria to stimulate the immune system to create the antibodies that will provide resistance to the disease. Usually only one or a few proteins on the surface of the bacteria or virus, called antigens, trigger the production of antibodies. Biotechnology is helping us improve existing vaccines and create new vaccines against infectious agents, such as the viruses that cause cervical cancer and genital herpes.