A growth factor isolated from human stem cells shows promising results in a mouse model of multiple sclerosis.

Human mesenchymal stem cells (hMSCs) have become a popular potential therapy for numerous autoimmune and neurological disorders. But while these bone marrow-derived stem cells have been studied in great detail in the dish, scientists know little about how they modulate the immune system and promote tissue repair in living organisms.

Now, one research team has uncovered a molecular mechanism by which hMSCs promote recovery in a mouse model of multiple sclerosis (MS).

According to research, published online Sunday (May 20) in Nature Neuroscience, a growth factor produced by hMSCs fights MS in two ways: blocking a destructive autoimmune response and repairing neuronal damage. The finding could help advance ongoing clinical trials testing hMSCs as a therapy for MS.

The researchers have identified a unique factor that has surprisingly potent activity mediating neuron repair, said Jacques Galipeau, a cell therapy researcher at Emory University in Atlanta, Georgia, who was not involved in the research. The magnitude of the effect on a mouse model of MS is a big deal.

MS is an autoimmune disease in which the immune system attacks myelin sheaths that surround and protect nerve cells. The attack leaves nerves exposed and unable to send signals to the brain and back, resulting in the loss of motor skills, coordination, vision, and cognitive abilities. There is no cure for MS, and most current therapies work to simply suppress the immune system, preventing further neuronal damage. None have demonstrated an ability to also repair damaged myelin and promote recovery.

In 2009, Robert Miller and colleagues at Case Western Reserve University in Cleveland, Ohio, demonstrated that hMSCs dramatically reversed the symptoms of multiple sclerosis in a mouse model of the disorder. The animals got better, recalled Miller. The team hypothesized that the stem cells suppress the immune response and promote remyelination.

But Miller wanted to know exactly what the cells were doing. To find out, his team isolated the medium on which the hMSCs were grown to determine if the cells or something they secreted was responsible for the observed recovery. The medium alone was enough to induce recovery in mice, pointing to the latter.

To find out exactly which molecule or molecules in the medium were responsible, the researchers separated the proteins in the fluid based on the molecular weight and injected each isolate into mice exhibiting symptoms of MS. The mid-weight solution, of proteins with masses between 50 and 100 kilodaltons (kDa), caused recovery. That eliminated a huge number of potential candidates, said Miller.

The researchers then narrowed the field again with a literature search for a molecule that fit their criteria: secreted by hMSCs, 50-100 kDa in size, and involved in tissue repair. They identified hepatocyte growth factor (HGF), a cytokine made by mesenchymal cells that has been shown to promote tissue regeneration and cell survival in numerous experiments. Sure enough, HGF alone was enough to promote recovery in the MS mouse models, and blocking the receptor for HGF in those mice blocked recovery. The team also demonstrated that HGF suppresses immune responses in vivo and accelerates remyelination of neurons in vitro. Finally, they saw that HGF causes remyelination in rats with a lesion on their spinal cord.

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Could Stem Cells Cure MS?

Public release date: 23-May-2012 [ | E-mail | Share ]

Contact: Kate McAlpine kmca@umich.edu 734-763-4386 University of Michigan

ANN ARBOR, Mich.University of Michigan researchers have proven that a special surface, free of biological contaminants, allows adult-derived stem cells to thrive and transform into multiple cell types. Their success brings stem cell therapies another step closer.

To prove the cells' regenerative powers, bone cells grown on this surface were then transplanted into holes in the skulls of mice, producing four times as much new bone growth as in the mice without the extra bone cells.

An embryo's cells really can be anything they want to be when they grow up: organs, nerves, skin, bone, any type of human cell. Adult-derived "induced" stem cells can do this and better. Because the source cells can come from the patient, they are perfectly compatible for medical treatments.

In order to make them, Paul Krebsbach, professor of biological and materials sciences at the U-M School of Dentistry, said, "We turn back the clock, in a way. We're taking a specialized adult cell and genetically reprogramming it, so it behaves like a more primitive cell."

Specifically, they turn human skin cells into stem cells. Less than five years after the discovery of this method, researchers still don't know precisely how it works, but the process involves adding proteins that can turn genes on and off to the adult cells.

Before stem cells can be used to make repairs in the body, they must be grown and directed into becoming the desired cell type. Researchers typically use surfaces of animal cells and proteins for stem cell habitats, but these gels are expensive to make, and batches vary depending on the individual animal.

"You don't really know what's in there," said Joerg Lahann associate professor of chemical engineering and biomedical engineering.

For example, he said that human cells are often grown over mouse cells, but they can go a little native, beginning to produce some mouse proteins that may invite an attack by a patient's immune system.

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Stem-cell-growing surface enables bone repair

People who suffer from heart failure could someday be able to use their own skin stem cells to regenerate their damaged heart tissue, according to a new Israeli study.

Researchers took stem cells from the skin of two patients with heart failure and genetically programmed them to become new heart muscle cells. They then transplanted the new cells into healthy rats and found that the cells integrated with cardiac tissue that already existed.

The study, published in European Heart Journal, marks the first time ever that scientists could use skin cells from people with heart failure and transform damaged heart tissue this way.

The newly generated cells turned out to be similar to embryonic stem cells, which can potentially be programmed to grow into any type of cell.

"What is new and exciting about our research is that we have shown that it's possible to take skin cells from an elderly patient with advanced heart failure and end up with his own beating cells in a laboratory dish that are healthy and young the equivalent to the stage of his heart cells when he was just born," Dr. Lior Gepstein, lead researcher and a senior clinical electrophysiologist at Rambam Medical Center in Haifa, Israel, said in a news release.

The findings open up the possibility, the authors wrote, that people can use their own skin cells to repair their damaged hearts, which could prevent the problems associated with using embryonic stem cells.

"This approach has a number of attractive features," said Dr. Tom Povsic, an interventional cardiologist at Duke University Medical Center. "We can get the cells that you start with from the patient himself or herself. It avoids the ethical dilemma associated with embryonic stem cells and it removes the possibility of rejection of foreign stem cells by the immune system." Povsic was not involved with the Israeli study.

Another advantage of using skin cells is that other types of cells taken from patients themselves, such as bone marrow cells, could potentially lead to the development of unhealthy tissue.

"If a patient is already sick with heart disease, one of the reasons it may develop is that stem cells weren't able to repair the heart the way they should," Povsic added. Skin cells, he explained, are generally healthy.

"It is very exciting and very interesting, but we are far away from taking this to patients," said Dr. Marrick Kukin, director of the Heart Failure Program at St. Luke's-Roosevelt Hospital who was also not involved in the Israeli study.

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Can Stem Cells Repair Heart Tissue?

May 23, 2012 12:00pm

Replacing dead or dysfunctional nerve cells with new, healthy ones derived from stem cells eases chronic pain in mice, a new study found.

Researchers from the University of California, San Francisco coaxed mouse embryonic stem cells into becoming mature nerve cells that could bridge gaps in the circuitry that triggers neuropathic pain.

One of the major causes of neuropathic pain is the loss of inhibitory control at the level of the spinal cord because of nerve loss or dysfunction, said study author Allan Basbaum, chairman of UCSFs department of anatomy. The idea was to replace or repopulate the spinal cord cells that provide that inhibition.

The same stem cells, destined to become inhibitory neurons that dampen the signals that cause pain, were previously shown to improve symptoms in a mouse model of epilepsy, Basbaum said. The question was whether we could take the exact same cells and put them in the spinal cord.

Before injecting the cells into the spinal cords of mice with neuropathic pain, the researchers labeled them with a fluorescent tracer to track the connections they made.

We were able to show how these cells integrate beautifully, Basbaum said, describingthe waythe transplanted cells looked and behaved like the mouses own.

Not only did the cells set up shop in the spinal cord, sending and receiving signals through a complex network of neurons, they also eased the neuropathic pain.

In four weeks, the animals condition completely disappeared, Basbaum said, adding that transplanted control cells that lacked the inhibitory properties of the stem-cell-derived neurons failed to ease the pain.

The clinical significance is that we think were actually modifying the disease, not just treating the symptoms, Basbaum said, adding that drugs currently used to ease neuropathic pain fail to treat the underlying problem. Instead of taking a drug to suppress the pain, were trying to normalize the circuit that was damaged by the disease or the injury. The cells repopulate, they integrate, and basically they treat the disease.

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Stem Cells Curb Chronic Pain in Mice