One theory may be the cause of the difference in circulation. But the new findings suggest an alternative for cancer care, spinal fusion surgery and osteoporosis, a disease that weakens the bones. About 10 million Americans.
Stem cells are like the body’s raw materials. Many stem cells can divide and form or develop to a specific fate, such as skin, red blood cells, neurons, or any of the estimated 200 different cell types in the human body.
In the journal Nature, researchers from Weill Cornell Medicine and the Hospital for Special Surgery in New York report the discovery of what they call spinal cord stem cells in the spinal cord. These cells make a protein that acts as a “come hither” signal to tumor cells, a discovery that opens up new treatment possibilities.
“We hypothesize that this finding will allow us to target these cells to disrupt their function and ultimately reduce the spread of cancer to the spine,” said study author Matthew B. Greenblatt, a pathologist at Weill Cornell Medicine.
Scientists found the cells first in mice, then in humans, within five years. In the spinal cord, the cells responsible for bone formation appear as the bone becomes stronger.
To demonstrate the vital role of vertebrate stem cells, researchers created mice in which they extracted some of the DNA. Using an enzyme, they removed a specific bone-forming gene from the newly-discovered vertebrate stem cells. Mice with the gene removed showed obvious spinal deformities, confirming the need for new stem cells to form the spinal cord.
The scientists then transplanted the stem cells into the mouse leg muscles. The transplanted cells made new tiny bones from scratch and produced all the types of bone cells found in the spine. Researchers have found that spinal cord stem cells help form the spine before birth, and then help maintain it after birth.
To find similar stem cells in humans, researchers studied very small pieces of spinal cord removed during laminectomies, which are surgeries that relieve pressure on nerves and spinal cord.
“Finding a new stem cell is very rare, and that’s one of the things that makes us excited about it,” Greenblatt said. “We think there’s something more recognizable.”
When they compared the stem cells that make up the spinal cord to those that make up the bones in the limbs, they found a protein that was present at much higher levels in the spinal cord. Mice deficient in this protein have much less cancer spreading to their spines.
Feiny Koo, director of the Washington Institute for Stem Cell and Regenerative Medicine, called the study “a discovery that will help us understand the developmental origins of the spinal cord.” Ku, who was not involved in the project, added that the study “may help us understand ways to be more creative” in delaying or stopping spinal metastasis.
Shawn Morrison, MD, director of the Children’s Research Institute at UT Southwestern Medical Center in Dallas, said the cells identified by the researchers are believed to be bone stem cells, whose existence has been known for years.
But Morrison, an investigator at the Howard Hughes Medical Institute, added that the paper still shows that bone stem cells in different parts of the body behave somewhat differently.
“The skeletal stem cells in the spinal cord have an amazing ability to attract cancer cells that you don’t see in other bone stem cells,” he said.
C. Rory Goodwin, MD, a neurosurgeon and spine surgeon at Duke Health, praised the paper’s authors and said the discovery of stem cells could help researchers improve the poor prognosis for cancer patients who have spread to the spine.
“When patients have a vertebral metastases, that’s usually toward the end of the line,” Goodwin said. After cancer spreads to the spine, the average survival time is 10 to 14 months, and “some patients survive less than that,” he said.
The findings also provide an explanation for why osteoporosis varies greatly in the spine compared to other parts of the skeleton. This knowledge can help doctors to plan treatment when the disease appears in the spine.
In separate work, Greenblatt and co-author on the Nature paper Servist Iyer, a spine surgeon at the Hospital for Special Surgery, are investigating the role of the new stem cell response to spinal fusion surgery. They want to determine if the new stem cell transplant can improve the integration during the surgery.
The two scientists suspect that a second type of vertebrate stem cell may exist. When they shut down the new stem cell’s ability to make bone, they still found small amounts of bone in some regions of the spine, raising the question of whether a second type of stem cell might be responsible.