Body parts - Bone marrow: the body's repair kit
Bone marrow is our elixir of life. Found in the center of the larger bones of the body, marrow is a gelatinous substance, reddish or yellow in color. Yellow marrow stores fat tissue, while red marrow produces the oxygen-carrying red blood cells, the infection-fighting white blood cells, and platelets, which help blood clot.
In recent years, scientists have also discovered that red bone marrow is also the body's Swiss Army repair kit. It contains a traveling laboratory of cells that can heal the liver, heart, kidneys, leg arteries, pancreas, and even ovaries and the brain.
Up to 40 percent of the liver can be regrown from stem cells found in bone marrow, researchers at New York University School of Medicine, Yale University School of Medicine and Sloan-Kettering Cancer Center found. They published their findings in the July issue of the journal Hepatology.
The researchers used a clever method: they studied liver tissue in women who had received bone marrow transplants from men. They stained the tissue so that Y chromosomes, found only in men, glowed fluorescent green. They could deduce that the cells with the green glowing Y chromosomes must have come from the male-derived bone marrow.
The same trick was used by New York University School of Medicine researchers to prove that mouse bone marrow cells can regenerate the insulin-secreting beta cells found in the pancreas. The study was reported in the March 14 issue of the Journal of Clinical Investigation.
Several studies, including one in humans, indicate that bone marrow cells migrate to the brain to repair damage. The study in humans, using the same cross-gender identification method, found evidence that transplanted bone marrow cells had reached the brain, possibly as a universal "repair squad," said researcher Helen Blau of the Stanford University Medical Center. She was quoted in a press release about the study, published online by the Proceedings of the National Academy of Sciences in February 2003.
Discovery of a "universal stem cell clone" in adult bone marrow was reported in November 2003 at a meeting of the American Heart Association's Scientific Sessions in Orlando. These cells were implanted into animals, and were found to improve the function of damaged hearts by forming new heart muscle and blood vessels. At another meeting held two years earlier in Anaheim, researchers reported using a patient's own bone marrow cells to improve blood circulation in damaged coronary arteries.
Similar bone marrow stem cell magic in mice reversed kidney damage, described in a paper released online last month in the Proceedings of the National Academy of Sciences. Mice were genetically engineered to develop a disease corresponding to Alport syndrome, in which missing genes harm the kidney's filtration system, eventually causing kidney failure. They were then given bone marrow transplants. In about a month, transplanted cells had moved into the damaged areas and began repairing them.
And also in mice, stem cells replenish ovaries with new egg cells, as reported in July 2005 in the journal Cell.
But there's bad along with the good. Bone marrow cells can develop a particularly deadly form of cancer, called multiple myeloma. And bone marrow stem cells can produce cancer in the stomach, according to a 2004 study from Columbia University Medical Center, published in the journal Science.
As with other organs, bone marrow stem cells move to the stomach to repair damage, in this case caused by a common bacterial infection. The infection and inflammation kills the normal cells, and the stem cells turn into stomach cells to replace them. But these replacement cells can at times become cancerous. The researchers said they plan to develop screening methods to detect people at higher risk for stomach cancer.
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