Transplantation of Unique, Newly Discovered Stem Cells May Lead to Promising Stroke Therapy


Stroke treatments have seen some remarkable advances in the past few years. Stem cell treatments for stroke have even seen some successes in clinical trials, showing that stem cell transplantation aimed at neural repair after a stroke is a possible way to ameliorate the effects of stroke.

Now, collaboration between teams of American and Japanese researchers has shown that a newly-identified stem cell has the ability to successfully treat stroke in rats. When administered to rats who have suffered from an experimentally-induced stroke, MUSE or multilineage-differentiating stress-enduring cells induced the regeneration of neurons and resulted in “significant improvements in neurological and motor functions” compared to control groups that were not transplanted with MUSE cells. MUSE cells also do not cause tumors.

The study has increased the number of therapeutic arrows in the quiver of neurologists and neuroscientists and lengthens the list of cells that might one day be considered for human clinical trials if continued pre-clinical tests prove successful. Future clinical studies aimed at regenerating neurological and motor function in patients who have suffered ischemic stroke.

The paper describing this study appeared in a recent issue of Stem Cells (Sept. 2015).

“Muse cells are unique stem cells that are able to self-renew and display high-efficiency for differentiating into neuron-like cells,” explained lead author Dr. Cesar V Borlongan, Distinguished Professor and Vice-Chairman for Research at the University of South Florida (USF) College of Medicine Department of Neurosurgery and Brain Repair and Director of USF’s the Center of Excellence for Aging and Brain Repair. “Unlike mesenchymal stem cells (MSCs) that have previously been used in stem cell transplantation in stroke-related clinical trials, in the present study Muse cells were found to possess functional characteristics of neurons as they attain the attributes of the host microenvironment. When MUSEcells were transplanted into to the brains of rats modeled with stroke, they attained neuronal characteristics.”

MUSE cells are found in many different tissues, including bone marrow, skin and fat. Since these cells can be derived from dermal fibroblasts (a type of connective tissue cell that provides the structural framework for animal tissues and plays a critical role in wound healing), they can be accessed with relative ease, without the need for the painful, invasive procedures required for obtaining other kinds of stem cells. Furthermore, while some stem cells used in stem cell transplantation studies have been found to cause cancer, MUSE cells do not produce tumors and exhibit exceptional tissue repair potential when introduced into the blood stream.

Some researchers think that fetal stem cells might be better candidates for replacing lost neural circuitry. The main reason in favor of fetal stem cells is that they preferentially differentiate into neuronal cells. However, the accessibility to fetal stem cells is limited and, like embryonic stem cells, the immaturity of these cells may present safety issues, such as tumor development. Additionally, the use of fetal and embryonic stem cells has many ethical difficulties to say the least. Since MUSE cells can be derived from adult tissue rather than fetal or embryonic tissue, the ethical quandaries associated with using them is minimal.

Not only do MUSE cells also have the practical advantage of being non-tumorigenic, they are readily accessed commercially and can also be easily collected from patient skin biopsies. MUSE cells also do not have to be “induced,” or genetically manipulated in order to be used, since they already display inherent stem cell properties after isolation. MUSE cells also spontaneously home toward the stroke-damaged sites.

“Ours is the first study to show that human skin fibroblast-derived Muse cells can have neuron-like function, possess an inherent ability to assume ‘stemness’ properties, and to readily differentiate into neural-lineage cells after integration into the stroke brain,” said co-lead author Dr. Mari Dezawa, Department of Stem Cell Biology and Histology, Tohoku University Graduate School of Medicine in Sendai, Japan. “Our results show that Muse cells are a feasible and promising source for cell-based approaches to ischemic stroke therapy.”

Intravenous Bone Marrow For Stroke: Clinical Trial


Akihiko Taguchi from the Institute of Biomedical Research and Innovation in Kobe, Japan, in collaboration with a whole host of colleagues from various places treated stroke with their own bone marrow. This is a Phase 1/2 clinical trial but it is a very small trial that was neither blinded not placebo-controlled. Therefore, while this trial is useful, the results are of limited value.

In this clinical trial, 12 stroke patients were divided into two groups, one of which received 25 milliliters and the other of which received 50 milliliters of bone marrow cells 7-10 days after their strokes. The bone marrow cells were administered intravenously. To isolate bone marrow cells, the so-called “mononuclear fraction” was isolated from whole bone marrow samples that came from bone marrow aspirations. Patients were evaluated by means of brain imaging to measure blood flow in their brains, and a series of neurological tests. The National Institute of Health Stroke Scale or NIHSS scores were used to grade the neurological capabilities of each patient. Patients were examined 1 month and then 6 months after treatment.

All treated patients were compared with the records of other stroke patients in the past who were not treated with bone marrow cells. These comparisons showed that the bone marrow-treated patients showed a trend towards improved neurological outcomes. Statistically, the bone marrow-treated patients had significantly better blood flow and oxygen consumption in their brains 6 months after treatment compared to the historic controls. Also, the NIHSS scores of the bone marrow-treated patients were also significantly better than those of the historic controls. Patients who received the higher doses of bone marrow cells did better than those who received the lower doses.

There were also no apparent adverse effects to administering the bone marrow cells. One patient experienced pneumonia and sepsis 3 months after cell therapy, but data monitoring largely eliminated the cell therapy as being a contributing factor to this issue. Another patient experienced a seconded stroke that was detected the day after the cell therapy. Because the patient had shown signs of a stroke the day before treatment, the association between the cell therapy and the recurrent stroke is rather unclear. None of the other patients showed any worsening of their present strokes, seizures, or other complications.

All in aloe, it seems as though this procedure is safe, and there is a trend towards increased metabolic and neurological recovery. However, this is a very small study and these trends may not hold in a larger study. Secondly, these patients must be followed for an extended period of time in order to determine if these improvements are durable or transient. Finally, these improvements must be compared with a placebo if there are going to convince the FDA.

Bone marrow cells contain a variety of stem cells and other types of cells that may release cocktails of healing molecules that help cells survive, make new blood vessels, and tamp down inflammation. Additionally, bone marrow cells might stimulate resident populations of stem cells to proliferate and make new neurons and glial cells. Until these positive results can be reproduced in larger, better controlled studies, these results will remain interesting and hopeful, but ultimately inconclusive.

These results were published in Stem Cells and Development 2015 DOI: 10.1089/scd.2015.0160.

Stem Cell Treatments for Stroke: A Tale of Two Trials


Two different clinical trials that examined the efficacy of stem cell treatments after a stroke have yielded very different results.

“Stroke” refers to a serious medical condition that occurs when the blood supply to the brain is disrupted by blockage of or injury to blood vessels that supply the brain with blood. Strokes cause a loss of, or reduction in, brain function. There are two main types of strokes. Ischemic stroke accounts for about 80% of strokes. Ischemic strokes result from the cessation of blood flow to an area of the brain because of a blood clot. Hemorrhagic stroke occurs if there is a leakage of blood into the brain because a blood vessel has burst. The bleed into the brain increases the pressure on the brain and leads to brain damage.

In the two clinical trials discussed in this post, both treatments were designed to address ischemic strokes, which disrupt the blood supply to the brain and starve brain cells of oxygen, causing them to die. Brain scans of patients who have suffered from an ischemic stroke may reveal large areas of damaged brain tissue. People who have had a stroke may experience difficulties with speech and language, orientation and movement, or memory. Such problems can be permanent or temporary.

Any advances in the treatment of stroke are particularly Currently, the only available treatment is to administer anti-clotting agents to dissolve the clot that has blocked the blood flow to the brain. Unfortunately, this treatment must be provided early and only a small proportion of patients get to hospital in time to be treated in this way.

There are no existing treatments for an ischemic stroke beyond the initial acute phase. However, rehabilitation can alleviate the disabilities caused by a stroke.

The European Stroke Organization released the results of large clinical trials on the treatment of strokes with CTX0E03 human neural stem cells. The PISCES trial, as it is known, is a phase I trial, and such trials usually involve giving a small number of people a new treatment to see if it is safe. Phase I trials are not designed to test if the treatment is effective, so any positive results from a Phase I trial should be treated with some caution.

This study examined the safety and tolerability of a stem cell therapy called ReN001 in the treatment of ischemic stroke.

11 males with long-term disability between 6 and 60 months after a stroke. None of the patients showed any cell-related or immunological adverse events. Patients did show sustained reductions in neurological impairment and spasticity compared to their stable pre-treatment baseline performance.

This clinical trial is a win for ReNeuron, the company that developed, makes and markets, ReN001. A Phase II is being planned.

A second clinical trial examined the efficacy of Athersys, Inc. MultiStem treatment for ischemic stroke. This phase II trial was designed to evaluate the efficacy of the product in stroke patients. 65 patients were treated with MultiStem and 61 were given the placebo. Unfortunately, even though the MultiStem treatment was safe as well tolerated, the cell therapy did not produce any statistically significant differences at 90 days in patients compared with a placebo.

Even though the data was disappointing, a second look at the data showed something interesting. When the 27 stroke patients who had received the MultiStem treatment 24-26 hours after the stroke were compared with all the other patients, it became clear that these patients did the best. Therefore, this trial seems to indicate that the window of treatment for MultiStem after a stroke is 24-36 hours and after 36 hours it works no better than placebo.

“Unfortunately, we just didn’t have the window right for this study,” Athersys Chief Operating Officer William Lehmann Reuters News Service. “We believe investors should see this as a sign that MultiStem works.”

The MultiStem treatment was also associated with lower rates of mortality and life threatening adverse effects, infections and lung-related events. Nine patients who had received the placebo died during the 90 day period (14.8%) while only four who received the MultiStem treatment died (6.2%).

The CEO of Athersys, Gil Van Bokkelen, said: “While the trial did not achieve the primary or component secondary endpoints, we believe the evidence indicating that patients who received MultiStem treatment early appeared to exhibit meaningfully better recovery is important and promising.”

This randomized, double-blind, placebo-controlled Phase 2 study is being conducted at sites in the United States and the United Kingdom.

Stroke Patients Improve After Stem Cell Treatments


Neurologists at Imperial College, London have conducted a small pilot study in stroke patients who received stem cell treatments after their strokes. To date, their patients have shown tentative signs of neurological recovery six months after receiving the stem cell treatment.

According to the physicians attending these patients, all five patients who participated in the study have improved after the therapy. Even though these results are hopeful, larger and better controlled trials are required to confirm if the implanted stem cells are responsible for the improvements in these patients. Brain scans of the patients showed that damage caused by the stroke had reduced over time. However, similar improvements are seen in stroke patients as part of the normal recovery process.

When assessed after their six-month check ups, all of the participating patients fared better on standard measures of disability and impairment that are normally caused by stroke. Once again, it is difficult to determine if these improvements result from the stem cell treatments or from standard hospital care.

This pilot study was designed to assess only the safety of the experimental therapy (phase I clinical trial) and with so few patients and no control group to compare them with, it is impossible to draw conclusions about the effectiveness of the treatment at this time.

Paul Bentley is a consultant neurologist at Imperial College London, and his group is presently applying for funding to run a more powerful randomized, controlled trial on this stem cell therapy, which, Bentley hopes, could include at least 50 patients by next year.

“The improvements we saw in these patients are very encouraging, but it’s too early to draw definitive conclusions about the effectiveness of the therapy,” said Soma Banerjee, a lead author and consultant in stroke medicine at Imperial College Healthcare National Health System (NHS) Trust. “We need to do more tests to work out the best dose and timescale for treatment before starting larger trials.”

All five patients who participated in this study were treated within seven days of suffering a severe stroke. Each patient had a bone marrow sample extracted from their hip bones, and these bone marrow cells were processed in the laboratory to isolated the stem cells that give rise to blood cells and blood vessel lining cells (so-called CD34+ cells). These stem cells were infused into one of the main arteries that supplies blood to the brain.

CD34+ cells do not grow into fresh brain tissue, but they might release pro-healing chemicals that suppress inflammation and recruit and stimulate other cells to grow within the damaged brain tissue. Some of the implanted CD34+ cells might also form new blood vessels, said Bentley.

Four out of five of the patients had the most serious type of stroke, and typically, only 4% of these patients survive and are able to live independently after six months. In the pilot study, published in Stem Cells Translational Medicine, all four were alive and three were independent six months later.

“Although they mention some improvement of some of the patients, this could be just chance, or wishful thinking, or due to the special care these patients may have received simply because they were in a trial,” said Robin Lovell-Badge, head of developmental genetics at the MRC’s National Institute for Medical Research in London.

Caution is certainly required in the interpretation of this pilot study, but I think that these results definitely merit a Phase II trial to determine if the improvements are stem cell-independent or stem cell-dependent.

Meta Study Shows that Mesenchymal Stem Cells Promote Healing in Animal Models of Stroke


Two scientists from my alma mater, UC Irvine, have examined experiments that treated stroke with bone marrow-derived stem cells. Their analysis has shown that infusions of these stem cells trigger repair mechanisms and limit inflammation in the brains of stroke patients.

UC Irvine neurologist Dr. Steven Cramer and biomedical engineer Weian Zhao identified 46 studies that examined the use of a specific type of bone marrow stem cells called mesenchymal stromal cells to treat stroke. Mesenchymal stromal cells are a type of multipotent adult stem cells that are found in many locations in the body. The best-known examples of mesenchymal stem cells are from bone marrow. When purified from whole bone marrow and used to treat stroke in animal models of stroke, Cramer and Zhao found that mesenchymal stromal cells (MSCs) were significantly better than control therapy in 44 of the 46 studies that were examined.

Further data culling of these studies showed that functional recovery from stroke were robust regardless of the MSC dosage or the time when MSCs were administered relative to the onset of the stroke, or the method of administration (whether introduced directly into the brain or injected via a blood vessel).

“Stroke remains a major cause of disability, and we are encouraged that the preclinical evidence shows [MSCs’] efficacy with ischemic stroke,” said Cramer, a professor of neurology and leading stroke expert. “MSCs are of particular interest because they come from bone marrow, which is readily available, and are relatively easy to culture. In addition, they already have demonstrated value when used to treat other human diseases.”

Another theme of these studies is that MSCs do not differentiate into brain-specific. MSCs have the capacity to differentiate into bone, cartilage and fat cells. “But they do their magic as an inducible pharmacy on wheels and as good immune system modulators, not as cells that directly replace lost brain parts,” he said.

In an earlier Cramer and Zhao examined the mechanism by which MSCs promote brain repair after stroke. These cells have the ability to home to the damages areas in the brain and release chemicals that stimulate healing. By releasing their cornucopia of healing-promoting molecules, MSCs orchestrate blood vessel creation to enhance circulation, the protection of moribund cells on the verge of death, and the growth of existing brain cells. Additionally, when MSCs reach the bloodstream, they settle in those parts of the body that control the immune system and they suppress the inflammatory response that can augment tissue damage. In this way, MSCs foster an environment more conducive to brain repair.

“We conclude that MSCs have consistently improved multiple outcome measures, with very large effect sizes, in a high number of animal studies and, therefore, that these findings should be the foundation of further studies on the use of MSCs in the treatment of ischemic stroke in humans,” said Cramer, who is also clinical director of the Sue & Bill Gross Stem Cell Research Center.

Human Neural Stem Cells Heal Damaged Limbs


The term “ischemia” refers to conditions under which a part of your body, organ, or tissue is deprived of oxygen. Without life-giving cells begin to die. Therefore, ischemia is usually a very bad thing.

Critical limb ischemia or CLI results when blood vessels to the legs, feet or arms are severely obstructed. The results of CLI are never pretty, and CLI remains a medical condition that presents few treatment options.

A study from a research team and the University of Bristol’s School of Clinical Sciences has used stem cells in a trial that uses laboratory mice to treat CLI. The success of this study provides a new direction and new hope for procedures that relieve symptoms and prolong the life of the limb.

Autologous stem cells treatments, or those stem treatments that utilize a patient’s own stem cells care subject to clear limitations. After collection from bone marrow, fat, or other source, the stem cells must be expanded in culture after stimulation with chemicals called cytokines. After growth in culture, the cells typically contain a collection of different types of stem cells of variable quality and potency. Also, if the patients has had a heart attack or has diabetes, then the quality and potency of their own stem cells are seriously compromised.

To circumvent this problem, Paulo Madeddu and his team at the Bristol Heart Institute have used an immortalized human neural stem cell line called CTX to treat animals who suffered from diabetes mellitus and CLI.

The CTX cell line comes from a biotechnology company called ReNeuron. This company is using this cell line in a clinical trial for stoke patients, and wants to use the CTX cell line in a clinical trial for CLI patients in the future.

When CTX cells are injected into the muscle of diabetic mice with CLI, the cells promote recovery from CLI. The CTX cells do so by promoting the growth of new blood vessels.

Madeddu said, “There are not effective drug interventions to treat CLI. The consequences are a very poor quality of life, possible major amputation and a life expectancy of less than one year from diagnosis in 50 percent of all CLI patients.”

Dr. Madeddu continued: “Our findings have shown a remarkable advancement towards more effective treatments for CLI and we have also demonstrated the importance of collaborations between universities and industry that can have a social and medical impact.”

Stem-Based Treatment of Stoke


When blood flow to the brain ceases as the result of a blood clot, trauma, or injury, the brain suffers from a shortage of oxygen. Such an incident is known as a stroke and it can result in the death of neurons and the loss of those functions to which the dead neurons contributed. Treatment for stroke is largely supportive, but regenerative treatments that replace the dead neurons would be the most ideal treatment.

A research consortium at Lund University in Lund, Sweden has found that neurons made from induced pluripotent stem cells integrate into the brains of mice that had suffered strokes. This experiment takes a closer step towards the development of a regenerative treatment for strokes.

Strategies for stem cell-based regenerative therapy in neurodegenerative diseases.
Strategies for stem cell-based regenerative therapy in neurodegenerative diseases.

In the aftermath of a stroke, nerve cells in the brain die. At the Lund Stem Cell Center, the research groups of Zaal Kokaia and Olle Lindvall teamed up to develop a stem cell-based method to treat stroke patients.

After a stroke, the cerebal cortex tends to take the bulk of the damage and neuron loss from the cerebral cortex underlies many of the symptoms following a stroke, such a paralysis and speech problems. The method developed by the Lund Institute scientists should make it possible to generate nerve cells for transplantation from the patient’s own skin cells.

Transient-Ischemic-Attack

First, the Lund team isolated skin fibroblasts from the afflicted mice and used genetic engineering techniques to convert them into induced pluripotent stem cells (iPSCs), which have many of the differentiation capabilities of embryonic stem cells. These iPSC lines were differentiated into cortical neurons, which tend to populate the cerebral cortex. However, transplanting fully differentiated neurons into the brain tend to not work terribly well because the mature neurons are unable to divide and have poor abilities to connect with other cells. Therefore, the neuron progenitor cells that will give rise to cortical neurons are a better candidate for transplantation.

After generating long-term self-renewing neuroepithelial-like stem cells from iPSCs in the laboratory, the Lund group scientists showed that these stem cells could give rise to neural progenitors that expressed the types of genes found in mature cortical neurons. When these neural progenitor cells were transplanted into rats that had suffered strokes, two months after transplantation, the cortically fated cells showed less proliferation and more efficient differentiation into mature neurons with the right shape, size, and structure of cortical neurons and expressed the same proteins as cortical neurons. These tranplanted cells also extended more axons than those cells that were not fated to form cortical neurons. Transplantation of both the cortical neuron-fated and non-cortical neuron-fated cells caused recovery of the impaired function in the stepping test in comparison to controls. At 5 months after stroke, there was no tumor formation and the grafted cells had all the electrophysiological properties of mature neurons and showed full evidence that they had integrated into the existing neural circuitry.

These results are very promising and represent a very early but important step towards a stem cell-based treatment for stroke in patients. Further experimental studies are necessary if these experiments are to be translated into the clinic in a responsible way.