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Posts Tagged ‘Duchenne muscular dystrophy’

MUSCLE REPAIR THROUGH STEM CELLS

In SCIENCE & STEM CELLS, STEM CELLS IN THE NEWS on March 13, 2013 at 9:00 am

Researchers from the University of Minnesota Use Genetically Corrected Stem Cells To Repair Muscles

University of Minnesota researchers from the Lillehei Heart Institute have combined genetic engineering techniques to repair mutations in abnormal muscle cells with cellular reprogramming to generate stem cells that can repair and regenerate muscle regeneration in a mouse model for Duchenne Muscular Dystrophy (DMD). This research is a proof-of-principle experiment that determines the feasibility of combining induced pluripotent stem cell technology and genetic engineering techniques that correct mutations to treat muscular dystrophy. Experimental strategies such as these could represent a major step forward in autologous cell-based therapies for DMD. Furthermore, it might pave the way for clinical trials to test this approach in reprogrammed human pluripotent cells from muscular dystrophy patients.

University of Minnesota researchers combined three groundbreaking technologies to achieve effective muscular dystrophy therapy in a mouse model of DMD. First, researchers reprogrammed skin cells into induced pluripotent stem cells (iPSCs). iPSCs are capable of differentiating into any of the mature cell types within an adult organism. In this case, the University of Minnesota researchers generated pluripotent cells from the skin of mice that carry mutations in two genes; the dystrophin and utrophin genes. Mice with mutations in both the dystrophin and utrophin genes develop a severe case of muscular dystrophy that resembles the type of disease observed in human DMD patients. This provided a model system platform that successfully mimicked what would theoretically occur in humans.

The second technology employed is a genetic correction tool developed at the University of Minnesota. In this case, they used a transposon, which is a segment of DNA that can jump from one location to another within the genome. The specific transposon used is the “Sleeping Beauty Transposon.” The use of this transposon allowed them to transport genes into cells in a convenient manner. The Lillehei Heart Institute researchers used the Sleeping Beauty transposon to deliver a gene called “micro-utrophin” into the iPSCs made from the DMD mice.

Sleeping Beauty Transposon

Human micro-utrophin can support muscle fiber strength and prevent muscle fiber injury throughout the body. However, there is one essential difference micro-utrophin and dystrophin: dystrophin is absent in muscular dystrophy patients, but if it is introduced into the bodies of DMD patients, their immune system will initiate a devastating immune response against it. However, in those same patients, utrophin is active and functional, which makes it essentially “invisible” to the immune system. This invisibility allows the micro-utrophin to replace dystrophin build and repair muscle fibers within the body.

Utrophin

The third technology utilized is a method to produce skeletal muscle stem cells from pluripotent cells. This procedure was developed in the laboratory of Rita Perlingeiro, who is also the principal investigator of this latest study.

Perlingeiro’s technology gives pluripotent cells a short pulse of a muscle stem cell protein called Pax3, which nudges the pluripotent cells to become skeletal muscle stem cells, which can then be exponentially expanded in culture. These Pax3-induced muscle stem cells were then transplanted back into the same strain of DMD mice from which the pluripotent stem cells were originally derived.

Pax3 and 7

When combined, these platforms created muscle-generating stem cells that would not be rejected by the body’s immune system. According to Perlingeiro, the transplanted cells performed very well in the dystrophic mice, and they generated functional muscle and responded to muscle fiber injury.

“We were pleased to find the newly formed myofibers expressed the markers of the correction, including utrophin,” said Perlingeiro, a Lillehei endowed scholar within the Lillehei Heart Institute and an associate professor in the University of Minnesota Medical School. “However, a very important question following transplantation is if these corrected cells would self-renew, and produce new muscle stem cells in addition to the new muscle fibers.”

By injuring the transplanted muscle and watching it repair itself, the researchers demonstrated that the transplanted muscle stem cells endowed the recipient mice with fully functional muscle cells. This latest project provides the proof-of-principle for the feasibility of combining induced pluripotent stem cell technology and genetic correction to treat muscular dystrophy.

“Utilizing corrected induced pluripotent stem cells to target this specific genetic disease proved effective in restoring function,” said Antonio Filareto, Ph.D., a postdoctoral fellow in Perlingeiro’s laboratory and the lead author on the study. “These are very exciting times for research on muscular dystrophy therapies.”

These studies pave the way for testing this approach in a clinical trial that would use reprogrammed human pluripotent cells from muscular dystrophy patients.

According to Perlingeiro, “Developing methods to genetically repair muscular dystrophy in human cells, and demonstrating efficacy of muscle derived from these cells are critical near-term milestones, both for the field and for our laboratory. Testing in animal models is essential to developing effective technologies, but we remained focused on bringing these technologies into use in human cells and setting the stage for trials in human patients.”

This research was published in Nature Communications.

Article written by: mburatov

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STEM CELL TREATMENTS TO BATTLE DMD (DUCHENNE MUSCULAR DYSTROPHY)

In ALL ARTICLES, SCIENCE & STEM CELLS, STEM CELLS IN THE NEWS on January 15, 2013 at 9:00 am

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Stem-Cell Approach Shows Promise for Duchenne Muscular Dystrophy

“Researchers have shown that transplanting stem cells derived from normal mouse blood vessels into the hearts of mice that model the pathology associated with Duchenne muscular dystrophy (DMD) prevents the decrease in heart function associated with DMD.”

Their findings appear in the journal Stem Cells Translational Medicine.

Duchenne muscular dystrophy is a genetic disorder caused by a mutation in the gene for dystrophin, a protein that anchors muscle cells in place when they contract. Without dystrophin, muscle contractions tear cell membranes, leading to cell death. The lost muscle cells must be regenerated, but in time, scar tissue replaces the muscle cells, causing the muscle weakness and heart problems typical of DMD.

The U.S. Centers for Disease Control and Prevention estimates that DMD affects one in every 3,500 males. The disease is more prevalent in males because the dystrophin mutation occurs on the X chromosome; males have one X and one Y chromosome, so a male with this mutation will have DMD, while females have two X chromosomes and must have the mutation on both of them to have the disease. Females with the mutation in one X chromosome sometimes develop muscle weakness and heart problems as well, and may pass the mutation on to their children.  Although medical advances have extended the lifespans of DMD patients from their teens or 20s into their early 30s, disease-related damage to the heart and diaphragm still limits their lifespan.

“Almost 100 percent of patients develop dilated cardiomyopathy,” in which a weakened heart with enlarged chambers prevents blood from being properly pumped throughout the body, said University of Illinois comparative biosciences professor Suzanne Berry-Miller, who led the study. “Right now, doctors are treating the symptoms of this heart problem by giving patients drugs to try to prolong heart function, but that can’t replace the lost or damaged cells,” she said.

In the new study, the researchers injected stem cells known as aorta-derived mesoangioblasts (ADM) into the hearts of dystrophin-deficient mice that serve as a model for human DMD. The ADM stem cells have a working copy of the dystrophin gene.  This stem cell therapy prevented or delayed heart problems in mice that did not already show signs of the functional or structural defects typical of Duchenne muscular dystrophy, the researchers report.

Berry-Miller and her colleagues do not yet know why the functional benefits occur, but proposed three potential mechanisms. They observed that some of the injected stem cells became new heart muscle cells that expressed the lacking dystrophin protein. The treatment also caused existing stem cells in the heart to divide and become new heart muscle cells, and the stem cells stimulated new blood vessel formation in the heart. It is not yet clear which of these effects is responsible for delaying the onset of cardiomyopathy, Berry-Miller said.

“These vessel-derived cells might be good candidates for therapy, but the more important thing is the results give us new potential therapeutic targets to study.  Activating stem cells that are already present in the body to repair tissue would avoid the potential requirement to find a match between donors and recipients and potential rejection of the stem cells by the patients.”

Despite the encouraging results that show that stem cells yield a functional benefit when administered before pathology arises in DMD mouse hearts, a decline in function was seen in mice that already showed the characteristics of dilated cardiomyopathy. One of these characteristics is the replacement of muscle tissue with connective tissue, known as fibrosis.

This difference may occur, Berry-Miller said, as a result of stem cells landing in a pocket of fibrosis rather than in muscle tissue. The stem cells may then become fibroblasts that generate more connective tissue, increasing the amount of scarring and making heart function worse. This shows that the timing of stem cell insertion plays a crucial role in an increase in heart function in mice lacking the dystrophin protein.

She remains optimistic that these results provide a stepping-stone toward new clinical targets for human DMD patients.

“This is the only study so far where a functional benefit has been observed from stem cells in the dystrophin-deficient heart, or where endogenous stem cells in the heart have been observed to produce new muscle cells that replace those lost in DMD, so I think it opens up a new area to focus on in pre-clinical studies for DMD,” Berry-Miller said.

The Illinois Regenerative Medicine Institute supported this research.

http://www.sciencedaily.com/releases/2013/01/130114133350.htm

SNOWMEN RECEIVING STEM CELLS

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