Researchers gain new molecular-level understanding of the brain's recovery after stroke

June 13, 2013

A specific MicroRNA, a short set of RNA (ribonuclease) sequences, naturally packaged into minute (50 nanometers) lipid containers called exosomes, are released by stem cells after a stroke and contribute to better neurological recovery according to a new animal study by Henry Ford Hospital researchers.

The important role of a specific microRNA transferred from stem cells to via the exosomes to enhance functional recovery after a stroke was shown in lab rats. This study provides fundamental new insight into how stem cells affect injured tissue and also offers hope for developing novel treatments for stroke and , the leading cause of long-term disability in adult humans.

The study, to be published in the journal Stem Cells, is available at http://www.ncbi.nlm.nih.gov/pubmed/23630198.

Although most stroke victims recover some ability to voluntarily use their hands and other body parts, nearly half are left with weakness on one side of their body, while a substantial number are permanently disabled.

Currently no treatment exists for improving or restoring this lost motor function in , mainly because of mysteries about how the brain and nerves repair themselves.

"This study may have solved one of those mysteries by showing how certain play a role in the brain's ability to heal itself to differing degrees after stroke or other trauma," says study author Michael Chopp, Ph.D., scientific director of the Henry Ford Neuroscience Institute and vice chairman of the department of Neurology at Henry Ford Hospital.

The researchers noted that Henry Ford's Institutional Animal Care and Use Committee approved all the experimental procedures used in the new study.

The experiment began by isolating (MSCs) from the bone marrow of . These MSCs are then genetically altered to release exosomes that contain specific microRNA molecules. The MSCs then become "factories" producing exosomes containing specific microRNAs. These microRNAs act as master switches that regulate biological function.

The new study showed for the first time that a specific , miR-133b, carried by these exosomes contributes to functional recovery after a stroke.

The researchers genetically raised or lowered the amount of miR-133b in MSCs and, respectively, treated the rats. When these MSCs are injected into the bloodstream 24 hours after stroke, they enter the brain and release their exosomes. When the exosomes were enriched with the miR-133b, they amplified neurological recovery, and when the exosomes were deprived of the miR-133b, the neurological recovery was substantially reduced.

Stroke was induced under anesthesia by inserting a nylon thread up the carotid artery to occlude a major artery in the brain, the middle cerebral artery. MSCs were then injected 24 hours after the induction of in these animals and neurological recovery was measured.

As a measure on neurological recovery, rats were given two types of behavioral tests to measure the normal function of their front legs and paws – a "foot-fault test," to see how well they could walk on an unevenly spaced grid; and an "adhesive removal test" to measure how long it took them to remove a piece of tape stuck to their front paws.

Researchers then separated the disabled rats into several groups and injected each group with a specific dosage of saline, MSCs and MSCs with increased or decreased miR-133b, respectively. The two behavioral tests were again given to the rats three, seven and 14 days after treatment.

The data demonstrated that the enriched miR-133b exosome package greatly promoted neurological recovery and enhanced axonal plasticity, an aspect of brain rewiring, and the diminished miR-133b exosome package failed to enhance neurological recovery

While the research team was careful to note that this was an , its findings offer hope for new ways to address the single biggest concern of as well as those with neural injury such as traumatic brain injury and spinal cord damage – regaining neurological function for a better quality of life.

Explore further: Microscopic packets of stem cell factors could be key to preventing lung disease in babies

Related Stories

Stem cells aid recovery from stroke

January 27, 2013

Stem cells from bone marrow or fat improve recovery after stroke in rats, finds a study published in BioMed Central's open access journal Stem Cell Research & Therapy. Treatment with stem cells improved the amount of brain ...

Virus-like particles provide vital clues about brain tumors

April 17, 2013

Exosomes are small, virus-like particles that can transport genetic material and signal substances between cells. Researchers at Lund University, Sweden, have made new findings about exosomes released from aggressive brain ...

Recommended for you

New 'Tissue Velcro' could help repair damaged hearts

August 28, 2015

Engineers at the University of Toronto just made assembling functional heart tissue as easy as fastening your shoes. The team has created a biocompatible scaffold that allows sheets of beating heart cells to snap together ...

Fertilization discovery: Do sperm wield tiny harpoons?

August 26, 2015

Could the sperm harpoon the egg to facilitate fertilization? That's the intriguing possibility raised by the University of Virginia School of Medicine's discovery that a protein within the head of the sperm forms spiky filaments, ...

Research identifies protein that regulates body clock

August 26, 2015

New research into circadian rhythms by researchers at the University of Toronto Mississauga shows that the GRK2 protein plays a major role in regulating the body's internal clock and points the way to remedies for jet lag ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.