Stem-cell therapy: The cure for all our ills?

Stem-cell therapy offers the prospect of revolutionary treatments for everything from broken bones and diabetes to cancer. Roger Dobson reports

Stem-cell therapy, once the stuff of science fiction, may soon be a reality for patients suffering from conditions as diverse as cancer, heart disease, broken bones and paralysis. The latest figures show that stem cells are involved in around 600 clinical trials worldwide, and with President Bush banning federal funding for research using one type of stem cell - embryonic - and Tony Blair championing the science in California this week, the UK looks set to attract much more research.

California is one of only a handful of states to fund work on stem-cell lines grown from embryos, and Blair, who was due to meet the chiefs of West Coast biotech firms yesterday, is keen to promote co-operation between California and the UK.

While bone-marrow transplants have been used for some time as a treatment for leukaemia, new uses for stem cells, both embryonic and adult, include treating diseases that are the biggest killers and causes of long-term disability. Future uses of stem cells range from growing new heart cells, and creating new faces, to growing sperm, building replacement limbs, and growing new retina tissue for the visually impaired.

Bones

The treatment of broken bones has not changed much for centuries, and splints and bandages or casts remain the mainstay. A clinical trial in the use of stem cells to repair fractured bones is now under way and could lead to a shake-up in treatment. Researchers are looking at the concept of repairing fractures with stem cells and a growth factor to speed up bone healing. Stem cells are also being looked at to combat osteoporosis, which causes brittle bones. As we age, bone loss exceeds production leading to osteoporosis, and stem-cell therapy could restore the balance.

Brain injury

Around one in four children who suffer brain injury die as a result. There is currently no therapy to reverse the effects of brain injury, but studies on animals have shown that stem cells from bone marrow can improve outcomes. The University of Texas has begun a clinical trial involving children aged five to 14 with a serious head injury. The children will be given injections of stem cells within 36 hours of their injury to see how it affects recovery. The hope is that the cells will help with repairs.

Cancer

Cancer is the disease against which stem-cell therapy has been most widely used. Leukaemia treatment is especially important, as success depends on getting rid of cancerous white blood cells and replacing them with healthy ones - usually achieved through a bone-marrow transplant. The use of stem cells to tackle cancer has been widened, and with more than 400 clinical trials under way, almost every kind of malignancy is being looked at. In many of the trials, stem cells are used to replace those killed by chemotherapy.

Crohn's disease

This bowel disorder is thought to be caused by immune cells attacking tissue. A trial is looking at the use of chemotherapy followed by an infusion of the patient's own stem cells. "The purpose of the chemotherapy is to destroy the immune system completely. The purpose of the stem cell infusion is to restore the body's blood production,'' say Northwestern University researchers.

Plastic surgery

This is an area that has potential for radical change due to stem cells. Researchers hope that stem cells can be injected on to specially shaped scaffolds in order to help fill defects in the face - they have already been used on a small number of patients. And at the University of Brescia in Italy, dental researchers have been investigating the idea of using stem cells taken from the hip bone to close the bone defect in cleft palate patients.

Neurological

Stem-cell therapy offers hope for Parkinson's and a number of other neurological diseases. The idea is to coax stem cells into becoming dopamine-producing nerve cells to replace cells lost to the disease. Dopamine is a chemical that allows messages to be sent to the parts of the brain that co-ordinate movement. The treatment being explored is transplanting stem cells into the target sites of the brain that need dopamine. Animal studies are under way.

What are stem cells?

Think of them as blank microchips before they have been programmed. Stem cells are the building blocks of our bodies that have not yet been assigned specialist tasks. Given particular chemical signals, they can be transformed into anything from a heart cell to a nerve cell. Embryonic stem cells, harvested from embryonic tissue, are the most versatile, and can be developed into almost every kind of cell type in the body.

Adult stem cells exist in a wide range of tissues including bone marrow, muscle, the brain and liver. They are already halfway down the career path to becoming a certain type of cell. Adult stem cells have restricted potential and can give rise only to a few cell types.

Heart disease

Almost three million people in the UK have heart disease. Stem-cell therapy is already being used in trials to tackle the damage caused by a heart attack, and to grow new blood vessels to get around blockages.

The idea is that injections of stem cells after a heart attack will help limit the amount of damage, grow new heart muscle, and increase the pumping ability of the heart. A second goal is to inject stem cells to grow new blood vessels and re-route blood and oxygen around damaged areas - a so-called grow-your-own bypass.

Rheumatoid arthritis

Around 700 patients with autoimmune diseases, such as rheumatoid arthritis, where the immune system attacks healthy tissue, have been treated with stem-cell therapy. In this therapy, the old marrow is removed, chemotherapy given to zap any remaining cells, and stem cells are used to build a new immune system.

Research at Leiden University in Holland shows that remission has been achieved in around one in three cases. In most cases, the patient's own cells are used, but immunologists in America have reported the first case of a woman being treated with stem cells from her sister. A year after transplantation the 52-year-old was in remission and not needing any drugs.

Paralysis

Superman actor Christopher Reeve, paralysed in a horse-riding accident, was one of the leading campaigners for stem-cell research. Although large clinical trials are some way off, researchers are reporting successes with small numbers of paralysed patients. The idea behind the therapy is that the stem cells can grow into nerve cells to replace those permanently damaged, and bridge the gap between the severed pieces of the spinal cord. Researchers in Argentina are reporting the restoration of movement in two patients.

Diabetes

With type one diabetes, which usually develops in childhood, the body does not produce its own insulin and daily injections are needed. It's caused by the destruction of insulin-producing cells by the body's immune system, and the aim of stem-cell therapy is to replace those immune cells. In a trial being run by Northwest University in Chicago, patients are being given chemotherapy and then infused with stem cells from bone marrow: "We hypothesise that reprogramming the immune system will stop immune aggression to the insulin-producing cells, allowing their regeneration," say researchers.

Dental

While the distant prospect of growing teeth is the most tantalising image of stem-cell potential in dentistry, changes are closer in other areas.

Orthodontists in Naples have found they can get stem cells from dental pulp in extracted molars, while Nippon Dental University researchers in Japan have shown that injecting stem cells into the area where a tooth has been extracted can strengthen the bone and support surrounding healthy teeth.

Multiple sclerosis

In MS, myelin, the protective coat that surrounds nerve cells, is damaged or destroyed by immune-system cells. The aim of stem-cell therapy is to use chemotherapy to destroy the malfunctioning immune system, and repopulate it with stem cells. According to the US National Institute of Allergy and Infectious Diseases and the Immune Tolerance Network, who are sponsoring one trial, a pilot study found that 18 of 19 MS patients stabilised or improved after treatment.