Stem Cell Therapy Repairs Brain Damage Hours After Stroke Occurs


According to the Center for Disease Control, stroke is a leading cause of death in the United States. Fortunately stroke has been the subject of significant research efforts, but unfortunately, developing treatments that ensure complete recovery for stroke patients is extremely challenging. The challenge increase when more than a few hours have passed between onset of the stroke and administration of treatment.

Thus a new study released in STEM CELLS Translational Medicine has generated more than a little excitement. This study indicates that indicates that endothelial precursor cells (EPCs), which are found in the bone marrow, umbilical cord blood, and rarely in peripheral blood, can make a significant difference for these patients’ recovery. The contribution of EPCs even extends to the later stages of stroke. In animal studies, EPC implantation into the brain after a stroke minimized the initial brain injury and helped repair the stroke damage.

“Previous studies indicated that stem/progenitor cells derived from human umbilical cord blood (hUCB) improved functional recovery in stroke models,” noted Branislava Janic, Ph.D., a member of Henry Ford Health System’s Cellular and Molecular Imaging Laboratory in Detroit and lead author of the study. “We wanted to examine the effect of hUCB-derived AC133+ endothelial progenitor cells (EPCs) on stroke development and resolution in rats.”

Dr. Janic and his team injected EPCs into the brains of rats that had suffered strokes. When they later examined the animals using MRI, they found that the transplanted EPCs had selectively migrated to the injured area, stopped the tissue damage from spreading, initiated regeneration, and affected the time course for stroke resolution. The lesion size in the brain was significantly decreased at a dose of 10 million cells, if the cells were given as early as seven days after the onset of the stroke.

“This led us to conclude that cord blood-derived EPCs can significantly contribute to developing more effective treatments that allow broader time period for intervention, minimize the initial brain injury and help repair the damage in later post-stroke phases,” Dr. Janic said.

“The early signs of stroke are often unrecognized, and many patients cannot take advantage of clot-busting treatments within the required few hours after stroke onset,” said Anthony Atala, M.D., editor of STEM CELLS Translational Medicine and director of the Wake Forest Institute for Regenerative Medicine. “In this animal study, a combination of stem cells shows promise for healing stroke damage when administered 24 hours after the stroke.”

Recovery of the Brain After a Stroke


A stroke results when the brain suffers from “ischemia” or a lack of blood flow for an extended period of time. Blockage in the small vessels that feed blood to the brain can cause a trans-ischemic attack (TIA) or stroke. The lack of oxygen causes localized death of brain cells. The dying cells dump a whole gaggle of molecules into the spaces surrounding nearby brain cells, and these cell-derived molecules can actually poison surrounding cells, thus increasing the area that dies as a result of a stroke.

Stroke pathology

New work from by Henry Ford Hospital researchers in Detroit, Michigan suggests that some of the molecules released by brain cells during a stroke might actually help the brain heal after a stroke. Small RNA molecules or microRNAs that are packaged into lipid-bound vesicles in cells known as exosomes are released by stem cells after a stroke and seem to contribute to neurological recovery.

Exosomes are secreted vesicles that were first discovered nearly 30 years ago. They were, at first, considered little more than garbage cans whose job was to discard unwanted cellular components. However, once cell biologists began to study these little structures, evidence began to accumulate that these dumpsters also act as messengers that convey information to distant tissues. Exosomes contain cell-specific payloads of proteins, lipids, and genetic material that are transported to other cells, where they alter function and physiology.

Exosome_Basics

Therefore, it is little wonder that exosomes can also transport microRNAs. In this present study from the laboratory of Michael Chopp, rats were given experimentally induced strokes, and then the neurological recovery of the rats was examined at the molecular level.

Chopp and his colleagues first isolated mesenchymal stem cells (MSCs) from the bone marrow of their laboratory rats. Then they genetically engineered these MSCs to release exosomes laden with specific microRNAs; in particular miR-133b.

MicroRNAs are a class of post-transcriptional regulators. Since they are usually only about 22 base pairs in length, they are far too short to encode anything. microRNAs usually bind to complementary sequences in the 3’ untranslated region of messenger RNAs, and this binding silences the RNA, which simply means that the RNA cannot be recognized by ribosomes and will not be translated into protein, or that the RNA is degraded by special enzymes that target RNAs bound by microRNAs. Single microRNAs target hundreds genes at a time, and some 60% of all genes are regulated by microRNAs. MicroRNAs are abundantly present in all human cells. They are also highly conserved in organisms ranging from the unicellular algae Chlamydomonas reinhardtii to mitochondria in vertebrates, which suggest that they are a vital part of genetic regulation throughout the plant and animal kingdoms.

The Actions of Small Silencing RNAs (A) Messenger RNA cleavage specified by a miRNA or siRNA. Black arrowhead indicates site of cleavage. (B) Translational repression specified by miRNAs or siRNAs. (C) Transcriptional silencing, thought to be specified by heterochromatic siRNAs.
The Actions of Small Silencing RNAs
(A) Messenger RNA cleavage specified by a miRNA or siRNA. Black arrowhead indicates site of cleavage.
(B) Translational repression specified by miRNAs or siRNAs.
(C) Transcriptional silencing, thought to be specified by heterochromatic siRNAs.

The microRNA known as miR-133b has been shown to enhance the death of prostate cancer cells when they are delivered to them (see Patron JP, Fendler A, Bild M, Jung U, Müller H, et al. (2012) MiR-133b Targets Antiapoptotic Genes and Enhances Death Receptor-Induced Apoptosis. PLoS ONE 7(4): e35345. doi:10.1371/journal.pone.0035345). However, because different cell types show different responses to the same reagents, exposing brain cells to this microRNA after a stroke might elicit a very different response.

By raising or lowering the amount of miR-133b in MSCs, Chopp and his colleagues were able to determine the effects of miR-133b on brains cells after a stroke. Chopp and others injected their genetically engineered MSCs into the bloodstream of rats 24 hours after inducing a stroke in these animals. When the exosomes of the MSCs were enriched in miR-133b, the neurological recovery in the rats was amplified, but when injected MSCs were deprived of miR-133b, the neurological recovery was substantially less.

To measure neurological recovery, researchers separated the disabled rats into several groups and injected each groups with saline, nongenetically-engineered MSCs, MSCs with low levels of miR-133b, and MSCs with high levels of miR-133b. The rats were given behavioral tests 3, 7, and 14 days after treatment. These tests measured the gait of the animals on a grid to determine if the rats could walk on an unevenly spaced grid (foot-fault test). The second test determined how long it took the rats to remove a piece of adhesive tape that was stuck to their front paws.

in every test, the rats injected with miR-133b-enriched MSCs showed superior levels of neurological recovery. Autopsies of these same animals revealed that the rats treated with miR-133b-enriched MSCs had enhanced rewiring of the brain and axonal outgrowth. In the areas of the brain adversely affected by the stroke, the rats showed increased axonal plasticity and neurite remodeling.

Most stroke victims recover some ability to use their hands and other body parts on a voluntary basis, but almost half of all stroke victims are left with some weakness on one side of their body and many are permanently disabled by the stroke.

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

Chopp said, “This study may have solved one of these mysteries by showing how certain stem cells play a role in the brain’s ability to heal itself to differing degrees after stroke or other trauma. Chopp also serves as the scientific director of the Henry Ford Neuroscience Institute.

A Stem Cell Treatment for Stroke


A new clinical trial is enrolling people who are dealing with the disabling effects of stroke.

Every year approximately 800,000 Americans suffer a stroke. Strokes or TIAs for “trans-ischemic attacks” result from blockage of a blood vessel in the brain. The lack of blood flow to the brain results in the death of those cells that starve from oxygen, and the aftermath of a stroke is remarkably unpleasant; long-term disability, permanent brain damage, and even death. Stroke is the leading cause of adult disability and extracts an annual burden of $62 billion on the US economy. Physical therapy can improve the deficits caused by a stroke, but there are, to date, no good treatments to ameliorate the condition of a stroke patient.

In the hopes of creating new options for stroke patients, researchers at Northwestern Medicine are examining a new regenerative treatment for stroke that utilizes a novel stem cell line called SB623. This stem cell line might provide increased motor function to stroke victims.

Northwestern is only one of three sites in the nation enrolling patients in a clinical study to evaluate the efficacy and safety of adult stem cell therapy in stroke patients. Patient who have suffered from so-called “ischemic stroke” suffer from impaired bodily functions that includes such conditions as paralysis, weakness on one side, difficulty with speech and language, vision issues, and cognitive deficits.

Joshua Rosenow, the principal investigator of this clinical trial, is the director of Functional Neurosurgery at Northwestern Memorial Hospital. Rosenow had this to say of this clinical study: “Two million brain cells die each minute during a stroke making it critical to get treatment fast at the earliest sign of symptoms once brain damage occurs, there’s very little that can be done medically to reverse it. While this study is only a preliminary step towards understanding the healing potential of these cells, we are excited about what a successful trial could do for a patient population that hs very limited therapeutic options.”

The primary purpose of this study is to examine the safety of SB623 stem cells. However, there is an added motive behind this study, and that is to determine if SB623 cells are efficacious as a treatment for stroke patients. SB623 cells are genetically engineered mesenchymal stem cells from adult bone marrow.

Richard Bernstein, the director of Northwestern Memorial’s Stroke Center, weighed in: “Although not proven in humans, these stem cells (SB623) have been shown to promote healing and improve function when administered in animal models of stable stroke. The cells did not replace the neurons destroyed by stroke, but instead they appeared to encourage the brain to heal itself and promote the body’s natural regenerative process. Eventually, the implanted stem cells disappeared.”

Rosenow added, “In this study, the cells are transplanted into the brain using brain mapping technology and scans, allowing us to precisely deposit the cells in the brain adjacent to the area damaged by the stroke.”

The first participants have received injections of 25 million cells, but as the study progresses, the dose will escalate to 5 million and eventually 10 million cells. Since SB623 cells are allogeneic, which is to say that they come from someone other than the patient, a single donor’s cells can be used to treat as many other patients. All subjects in this study will be followed for up to two years with periodic evaluations for safety and effectiveness in improving motor function.

Bernstein explained, “Stroke can be a very disabling and life-changing event. Even just a slight improvement in function could make a huge difference for a person impacted [sic] by stroke. To potentially regain movement or speech is a very exciting prospect. In the animal models, the improvements appeared to remain even after the implanted stem cells disappeared.

Even at this early stage in this clinical trial, there is a great deal of excitement over the potential for stem cell therapy. Rosenow echoed this excitement when he said, “Of these cells are proven effective in improving, or even reversing brain damage, the implications of a successful outcome reach far beyond just stroke. Stem cell therapy may hold the key to treating a wide range of neurological disorders that do not have many available therapies. The Northwestern team is very excited to be a part of this groundbreaking trial.”

Participants for this trial must be between the ages of 18 and 75 years old, must have had an ischemic stroke in the last six to 36 months. They should have moderate to severe symptoms with impaired motor function. Full inclusion and exclusion criteria are available online. Full inclusion and exclusion criteria are available online. The FDA-approved phase 1-11 study is expected to enroll 18 subjects nationwide and this study is slated to last up to two years.

Other sites participating in the trial are the University of Pittsburgh Medical Center and Stanford University School of Medicine. The trial is funded by SanBio, Inc., a regenerative medicine company that developed the SB623 stem cell line.

SB623 papers:

1. Extracellular matrix produced by bone marrow stromal cells and by their derivative, SB623 cells, supports neural cell growth.  Aizman I, Tate CC, McGrogan M, Case CC.

  • J Neurosci Res. 2009, 87(14):3198-206.

2. Notch-induced rat and human bone marrow stromal cell grafts reduce ischemic cell loss and ameliorate behavioral deficits in chronic stroke animals. Yasuhara T, Matsukawa N, Hara K, Maki M, Ali MM, Yu SJ, Bae E, Yu G, Xu L, McGrogan M, Bankiewicz K, Case C, Borlongan CV.  Stem Cells Dev. 2009, 18(10):1501-14

3. Reversal of dopaminergic degeneration in a parkinsonian rat following micrografting of human bone marrow-derived neural progenitors. Glavaski-Joksimovic A, Virag T, Chang QA, West NC, Mangatu TA, McGrogan MP, Dugich-Djordjevic M, Bohn MC.  Cell Transplant. 2009, 18(7):801-14.

4.

Tate CC, Fonck C, McGrogan M, Case CC. Cell Transplant. 2010,19(8):973-84.

5. Glial cell line-derived neurotrophic factor-secreting genetically modified human bone marrow-derived mesenchymal stem cells promote recovery in a rat model of Parkinson’s disease.  Glavaski-Joksimovic A, Virag T, Mangatu TA, McGrogan M, Wang XS, Bohn MC. J Neurosci Res. 2010, 88(12):2669-81.

6. Comparing the immunosuppressive potency of naive marrow stromal cells and Notch-transfected marrow stromal cells.

  • Dao MA, Tate CC, Aizman I, McGrogan M, Case CC.

J Neuroinflammation. 2011, 8(1):133.

7.

Tate CC and Case CC.

  • Chapter in “Neurological Disorders”, InTech, 2012.