SanBio, Inc., has announced the randomization of the first patient in their STEMTRA Phase 2 clinical trial study for traumatic brain injury. The STEMTRA trial is presently enrolling patients in both the United States and Japan, and the first patient was randomized at Emory University Hospital in Atlanta, Ga.
STEMTRA stands for “Stem cell therapy for traumatic brain injury,” and this trial will examine the effects of SB623 stem cells to treat patients with chronic motor deficits that result from traumatic brain injury (TBI).
SB623, a proprietary product of SanBio, are bone marrow-derived mesenchymal stem cells that have been genetically engineered to express the intracellular domain of Notch-1. When injected into neural tissue, SB623 cells seem to reverse neural damage. Since SB623 cells come from donors, a single donor’s cells can be used to treat thousands of patients. In cell culture and animal models, SB623 cells restore function to neurons damaged by strokes, spinal cord injury and Parkinson’s disease. There have been no serious adverse events attributable to the cell therapy product and patients benefit on all three stroke scales.
Traumatic brain injuries (TBIs) can be caused by a wide range of events, including falls, fights, car accidents, gunshot wounds to the head, blows to the head from falling objects, and battlefield injuries. These events often result in permanent damage, including significant motor deficits; leaving more than 5.3 million people living with disabilities in the United States alone.
Damien Bates of SanBio, said, “This modified stem cell treatment has improved outcomes in patients with persistent limb weakness secondary to ischemic stroke. Our preclinical data suggest it may also help TBI patients. For people suffering from the often debilitating effects of TBI, this milestone brings us one step closer to proving whether it’s an effective treatment option.”
The STEMTRA trial follows a Phase 1/2a clinical trial in patients afflicted with chronic motor deficit secondary as a result of an ischemic stroke were treated with SB623 cells. In this trial, SB623 cells statistically significantly improved motor function following implantation. The STEMTRA study will evaluate the tolerability, efficacy, and safety of the SB623 cell treatment and the administration process in those patients who have suffered a TBI. As a Phase 2 trial, STEMTRA will evaluate the clinical efficacy and safety of intracranial administration of SB623 cells in patients with chronic motor deficit from TBI.
STEMTRA will be conducted across approximately 25 clinical trial sites throughout the United States and five sites in Japan. Total enrollment is expected to reach 52 patients in total, and all enrolled patients must have suffered their TBI at least 12 months ago.
Traumatic brain injuries can result from a variety of causes, ranging from car accidents, falls, occupational hazards, and sports injuries. The cause of traumatic brain injury (TBI) differs from that of ischemic stroke, but many of the clinical manifestations are somewhat similar (motor deficits). Such injuries can cause lifelong motor deficits, and there are currently no approved medicines for the treatment of persistent disability from traumatic brain injury.
SanBio, Inc., has completed the regulatory requirements to conduct a clinical trial using their proprietary SB623 regenerative cell therapy to treat patients who suffer from TBI. The obligatory 30-day review period of clinical trial notification by the Japanese Pharmaceuticals and Medical Devices Agency (PMDA) was completed on March 7, 2016. No safety concerns were voiced, and the trial can proceed.
SanBio’s clinical trial is entitled “Stem cell therapy for traumatic brain injury” or STEMTRA, and it will study the safety and efficacy of SB623 cell therapy in treating patients who suffer from chronic motor impairments following a TBI.
Enrollment in this clinical trial started in the United States in October, 2015. The trial will include clinical sites and patients in Japan and will enroll ~52 patients. The enrollment of Japanese patients is expected to accelerate the overall enrollment of human subjects.
SanBio spokesperson, Damien Bates, the Chief Medical Officer and Head of Medical Research at SanBio, said: “SanBio’s regenerative cell medicine, SB623, has improved outcomes in patients with persistent motor deficits due to ischemic stroke, and our preclinical data suggest that it may also help TBI patients. This is the first global Phase 2 clinical trial for TBI allogeneic stem cells, and the approval to conduct the trial in Japan, as well as in the United States, brings us one step closer to determining SB623’s efficacy for treatment whose who suffer from the effects of traumatic brain injury.”
SB623 are modified mesenchymal stem cells that transiently express a modified human Notch1 gene that only contains the intracellular domain of the Notch1 protein. This activated gene drives mesenchymal stem cells to form a cell type that habitually supports neural cells and promotes their health, survival, and healing. When administered into damaged neural tissue, SB623 reverses neural damage. Since SB623 cells are allogeneic (from a donor), a single donor’s cells can be used to treat many patients. In cell culture and animal models, SB623 cells restore function to damaged neurons associated with stroke, traumatic brain injury, retinal diseases, and Parkinson’s disease. SB623 cells function by promoting the body’s natural regenerative process.
Since the therapeutic mechanism of action of SB623 cells and the proposed route of administration are similar in the two trials (the stroke and TBI trials), the results of the TBI trial should be similar to those of the stroke trial.
The Japanese regulatory agencies grant marketing approval for regenerative medicines earlier countries as a result of an amendment to the Pharmaceutical Affairs Law in 2014. This particular amendment defined regenerative medicine products as a new category in addition to conventional drugs and medical devices, and the conditional and term-limited accelerated approval system for regenerative medicine products has started.
Two regenerative medicine products have already gained marketing approval under this new system, and the government-led industrialization of regenerative medicine products has gradually been realized.
SanBio has begun the preparation of clinical trial facilities in Japan and expects the launch of the clinical trial in 2016. the company hopes to market the medicine in Japan by taking advantage of the accelerated approval system.
Injecting stem cells into the brain has serious risks. In the a case of patients who have experienced traumatic brain injury (TBI), intracranial injections of stem cells can cause intracranial hemorrhage. Also, the injected stem cells often fail to find their way to the injured parts of the brain. Therefore, you have a high-risk procedure that may yield few benefits.
However a new technique for getting stem cells into the brain has been designed and tested by Paul Yarowsky and his colleagues at the University of Maryland and the Veterans Administration Maryland Healthcare System.
Yarowsky and his coworkers labeled human neural progenitor cells with iron oxide “superparamagnetic nanoparticles” and directed team to the site of a brain injury by means of a magnetic field.
They tested this technique in rats that had suffered TBI and discovered that the delivery methods has no deleterious effects on the viability of the stem cells and not only increases stem cell homing to the site of injury, but also increased stem cell retention.
“Magnetic cell targeting is ideally suited to augmenting cell therapies. The external magnetic field and field gradient can guide cells to sites of injury and, using MRI, the iron-oxide superparamagnetic nanoparticles can be visualized as they travel to the site of injury. The goal when employing this method is not only guiding the particles to the site of injury, but also enhancing entry into the brain and the subsequent retention of the transplanted cells,” said Yarowsky.
The intensity of the magnetic field neither affects the viability of the cells in culture, nor their proliferation nor differentiation. This is also the case when the cells are loaded with iron oxide nanoparticles. These results suggest that this is indeed a promising technique for cell delivery in TBI patients and might also be useful for treating other neurological injuries and neurodegenerative diseases as well.
A critical question is, “what happens to the cells when the magnetic field is no longer present?”. Also, the patient must wear a magnetic hat in order to subject the cells to a magnetic field, but what is the minimum time the patient must wear it in order for the procedure to be successful? All of these questions must be addressed to some degree if they this technique is to be properly understood. For now, Yarowsky and his colleagues assume that the optimized magnetic intensity observed in experiments with rodents must be extrapolated to larger animals, which may or may not be a legitimate extrapolation. Until larger animal experiments are conducted, this will remain a speculation.
Even though a good deal of work remains to be done, Yarowsky and his colleagues are still optimistic that their ingenious iron oxide nanoparticle procedure has promise and might, some day, be translated to human clinical trials.
This work was published in the journal Cell Transplantation, 21 September 2015.
Approximately 2 million Americans experience a traumatic brain injury every year. Most of these are individuals who employed in high-risk jobs such as the military, firefighting, police work and others types of essential but highly dangerous jobs. No matter how small the injury, individuals who have suffered a traumatic brain injury (TBI) can suffer from a whole host of motor, behavioral, intellectual and cognitive disabilities over the short or long-term. Unfortunately, there are few clinical treatments for TBI, and the few we have are rather ineffective.
In order to design better, more effective treatments for TBI, neuroscientists at the Center of Excellence for Aging and Brain Repair, Department of Neurosurgery in the USF Health Morsani College of Medicine, University of South Florida, have used umbilical cord stem cells in combination with growth factors to treat TBIs in mice.
This study investigated the ability of several strategies, both by themselves and in combination with other therapies, to treat rats with a laboratory form of TBI. In particular, the USF team discovered that a combination of human umbilical cord blood cells (hUBCs) and granulocyte colony stimulating factor (G-CSF), a growth factor, was more therapeutic than either administered alone, or each with saline, or saline alone.
“Chronic TBI is typically associated with major secondary molecular injuries, including chronic neuroinflammation, which not only contribute to the death of neuronal cells in the central nervous system, but also impede any natural repair mechanism,” said study lead author Cesar V. Borlongan, PhD, professor of neurosurgery and director of USF’s Center of Excellence for Aging and Brain Repair. “In our study, we used hUBCs and G-CSF alone and in combination. In previous studies, hUBCs have been shown to suppress inflammation, and G-CSF is currently being investigated as a potential therapeutic agent for patients with stroke or Alzheimer’s disease.”
In previous studies, Borlongan and his team showed that G-CSF can mobilize stem cells from bone marrow and induce them to home to and infiltrate injured tissues. While there, the cells promote neural cell self-repair. Cells from human umbilical cord blood also have the ability to suppress inflammation and promote cell growth.
“Our results showed that the combined therapy of hUBCs and G-CSF significantly reduced the TBI-induced loss of neuronal cells in the hippocampus,” said Borlongan. “Therapy with hUBCs and G-CSF alone or in combination produced beneficial results in animals with experimental TBI. G-CSF alone produced only short-lived benefits, while hUBCs alone afforded more robust and stable improvements. However, their combination offered the best motor improvement in the laboratory animals.”
“This outcome may indicate that the stem cells had more widespread biological action than the drug therapy,” said Paul R. Sanberg, distinguished professor at USF and principal investigator of the Department of Defense funded project. “Regardless, their combination had an apparent synergistic effect and resulted in the most effective amelioration of TBI-induced behavioral deficits.”
This particular study examined motor improvements or improvements in movement, but the USF group suggested that future combination therapy research should also include analysis of cognitive improvement in the laboratory animals with TBI.
In short, umbilical cord cell and growth factor treatments tested in animal models could offer hope for millions, including U.S. war veterans with traumatic brain injuries.
Post-script: On Twitter, Alexey Bersenev made some very helpful observations about this paper. In this paper, the authors used whole human umbilical cord blood. They did not attempt to separate any of the different cell types from the cord blood. Now when such whole blood is used, it is easy to assume that the stem cells in the blood that are doing the regenerative work. However, as Alexey graciously pointed out, you cannot assume that the stem cells are responsible for the therapeutic effects for at least two main reasons: 1) the number of stem cells in the cord blood is quite small relative to the other cells; 2) some of the non-stem cells in the blood turn out to have therapeutic effects. See here and here. I have seen some of these papers before, but I did not think much of them. Therefore, until the cell populations in the umbilical cord blood are dissected out and studied, all we can say with any confidence is SOMETHING in the cord blood is conveying a therapeutic effect, but the identity of the therapeutic culprit remains unclear at this time.
A study at the Texas Health Science Center has shown that stem cell treatments that quash inflammation soon after traumatic brain injury (TBI) might also offer lasting cognitive gains.
TBI sometimes causes severe brain damage, and it can also lead to recurrent inflammation of the brain. This ongoing inflammation can extend the damage to the brain. Only a few drugs help (anti-inflammatory drugs for example). Up to half of patients with serious TBI need surgery, but some stem cells like a sub group of mesenchymal stem cells called multipotent adult progenitor cells (MAPCs) can reduce short-term inflammation, and induce functional improvement in mice with TBI. Unfortunately, few groups have gauged the long-term effects of MAPCs on TBI.
In an article that appeared in the journal Stem Cells Translational Medicine, a research team led by the Director of the Children’s Program in Regenerative Medicine, Charles Cox, reported the use of human MAPCs in mice that had suffered TBI.
In this study, Cox and his colleagues infused MAPCs into the bloodstream of two groups of mice 2, and 24 hours after suffering a TBI. The first group of mice received two million cells per kilogram, and mice in the other group received an MAPC dose five times stronger.
Four months after MAPC administration, those mice that had received the stronger dose continued to experience less brain inflammation and better cognition. Spatial learning was increased and motor deficits had decreased.
According to Cox, the intravenously administered MAPCs did not cross the blood/brain barrier. Since immune cells can cross the blood/brain barrier for a short period of time after a TBI and cause autoimmunity, this result shows that the MAPCs are quelling inflammation through “paracrine” mechanisms (paracrine means that molecules are secreted by the cells and these secreted molecules elicit various responses from nearby cells). Cox made this clear: “We spent 18 months looking for them in the brain. There was little to no engraftment there.”
Rather than entering the brain, the MAPCs “set up shop in the spleen, a giant reservoir of T and B cells. The MAPCs change the spleen’s output to anti-inflammatory cells and cytokines, which communicate with immune cells in the brain—microglia—and change their response to injury from hyper-to-anti- inflammatory. The cells alter the innate immune response to injury. We have shown this in a sequence of papers.”
University of Cambridge neurologist, Stefano Pluchino, has worked with immune regulatory stem cells. Pluchino said that Cox’s study shows a “good dose response” on disability and behavior “after hyperacute, or acute, intravenous injection of MAPCs.” However, Pluchino noted that the description of the effects of MAPCs on microglia (white blood cells in the brain that gobble up foreign matter and cell debris) is “speculative.” Pluchino continued: “It is not clear whether these counts have been done on the injured brain hemisphere, and whether MAPC effects were observable on the unaffected hemisphere. The distribution and half-life of these MAPCs is not clear” and has never been demonstrated convincingly in Athersys papers (side note: Athersys is the company that isolates and grows the human MAPCs). “It is also not clear if effects in the Cox study were a ‘false positive,’ secondary to a paradoxical immune suppression the xenograft modulates.” That is, a false positive could occur because human cells in animal bodies rouse immune reactions. “It is not clear where in the body these MAPCs would work, either out or into the injured brain.” Additionally the mechanism by which these cells act does not seem to be clear, according to Pluchino.
But, Pluchino added: “Athersys is already in clinic with MAPCs in graft vs. host disease, myocardial infarction, stroke, progressing towards a phase I/II clinical trial in multiple sclerosis, and completing the pre-clinical work in traumatic brain and spinal cord injuries. Everything looks great. The company is solid. The data is convincing in terms of behavioral and pathological analyses. But the points I have raised are far from clarified.”
Cox admitted that Pluchino’s points are valid. He pointed out that human cells were used in rodents, since the FDA wants pre-clinical studies in laboratory animals in order to first evaluate the safety and efficacy of the exact cells to be used in a proposed therapy before they head to the clinic. “As we are not seeking engraftment of these cells, and would not plan to immunosuppress a trauma patient, we have not pursued animal models that use immunosuppression. Our study was designed with translationally relevant end-points, recognizing the limitations of not having a final mechanism of action determined. The growing consensus is there are many mechanism(s) of action in cell therapies.”
Cox also agreed that the suggested effects of MAPCs on microglia, “is not truly a proof of mechanism.” However, Cox and his co-workers have developed a protocol that can potentially more accurately quantify microglia in mice. “We ultimately plan more mechanistic studies to define endogenous microglia versus infiltrating microglia and the effects of various cell therapies. “
Additionally, Cox also said that: “We have published work showing the majority of acutely infused MSCs and MAPCs are lodged in the lung after intravenous delivery. This was an acute study in non-injured animals, but others have shown similar data.” In another study, Cox’s research group showed that the cells cluster in the spleen, which corroborates work by other research groups that have used umbilical cord cells to treat stroke.
Finally, Cox disagrees that the suppression of immune cell function in animals by human cells is appropriately characterized as “a false positive.” Cox explained that the infused cells induce a “modulation of the innate immune response, and typically, the immune rejection of a transplant is associated with immune activation, not suppression. So it well may be a ‘true positive.’”
In order for MAPCs to make to the clinical trial stage, Cox will need to investigate the mechanisms by which MAPCs suppress inflammation and if their purported effects on microglia in the central nervous system are real. He will also need to show that these cells work in other types of laboratory animals beside mice. Rats will probably be next, and after that, my guess is that the FDA would allow Athersys to apply for a New Drug Application.
University of South Florida (USF) scientists have suggested a new strategy for stem cell-mediated brain repair following trauma.
In several preclinical experiments, the USF group found that transplanted stem cells build a “biobridge” that links an injured site in the brain to a site where neural stem cells form.
Principal investigator, Cesar Borlongan, professor and director of the USF Center for Aging and Brain Repair, said: “The transplanted stem cells serve as migratory cues for the brain’s own neurogenic cells, guiding the exodus of these formed host cells from their neurogenic niche towards the injured brain.”
On the strength of these preclinial studies in laboratory animals, the US Food and Drug Administration recently approved a limited clinical trial to transplant SanBio Inc.’s SB632 cells into patients with traumatic brain injuries. SB632 cells are a proprietary product of SanBio, Inc., and SB632 cells are derived from mesenchymal stem cells but they have been genetically engineered to express the intracellular domain of the Notch protein (NICD; see C. Tate, et al., Cell Transplantation, Vol. 19, pp. 973–984, 2010). If the Notch protein, which functions as a signaling protein and normally sits in the cell membrane, has its outer piece removed, the protein is constitutively activated. This full-time activation of the Notch protein and its downstream targets drive SB632 cells to form neural cells; something that mesenchymal stem cells typically do not readily make.
While this over-simplifies the field to some extent, there are two views on how stem cells heal brain damage caused by injury or neurodegenerative disorders. One view postulates that stem cells implanted into the brain directly replace dead or dying cells by differentiating into neurons and glial cells. The other view is that transplanted stem cells secrete growth factors that indirectly rescue the injured tissue. This present USF study argues for a third view, namely that implanted stem cells for a causeway in the brain between damaged areas and those anatomical structures that give birth to neural stem cells.
In this USF study, Borlongan and his group randomly assigned rats with traumatic brain injury and confirmed neurological impairment to one of two groups. The first group received transplants of SB632 cells into the region of the brain affected by traumatic injury. The second group received a sham procedure in which solution alone was infused into the brain with no implantation of stem cells.
At one and three months post-TBI (traumatic brain injury), the rats that had received SB632 transplants showed significantly better motor and neurological function and reduced brain tissue damage when compared to rats that had received no stem cells. These robust improvements despite the fact that the transplanted stem cells showed fair to poor survival that diminished over time.
Next, Borlongan’s laboratory workers examined the brain tissue of these rats. At three months post-TBI, the brains of transplanted rats showed massive cell proliferation and differentiation of stem cells into neuron-like cells in the area of injury. This was accompanied by a solid stream of stem cells that had migrated from the brain’s uninjured subventricular zone (where many new stem cells are formed) to the brain’s site of injury.
In contrast, those rats that had received solution alone showed limited proliferation and neural-commitment of stem cells, and only showed scattered migration to the site of brain injury and almost no expression of newly formed cells in the subventricular zone. Thus, without the addition of transplanted stem cells, the brain’s self-repair process appeared insufficient to mount a defense against the cascade of TBI-induced cell death.
Borlongan concluded that the transplanted stem cells create a neurovascular matrix that bridges the gap between the region in the brain where host neural stem cells arise and the site of injury. This pathway, or “biobridge,” ferries the newly emerging host cells to the specific place in the brain in need of repair, and helps them to promote functional recovery from traumatic brain injury.
Research led by Charles Cox at the University of Texas Health Science Center has shown that stem cell therapy given during the critical time window after traumatic brain injury promotes lasting cognitive improvement. These experiments, which were published in the latest issue of the journal Stem Cells Translational Medicine, provide a pre-clinical model for experiments with larger animals.
After the brain has suffered a traumatic injury, there are few treatment options. Damage to the brain can be severe, and can also cause ongoing neurological impairment. Approximately half of all patients with severe head injuries need surgery to remove or repair ruptured blood vessels or bruised brain tissue.
In this work from Cox’s lab, stem cells from bone marrow known as multipotent adult progenitor cells (MAPCs) were used. MAPCs seem to be a subpopulation of mesenchymal stem cells, and they have a documented ability to reduce inflammation in mice immediately after traumatic brain injury. Unfortunately, no one has measured the ability of MAPCs to improve the condition of the brain over time.
Cox, Distinguished Professor of Pediatric Surgery at the UTHealth Medical School and in collaboration with the Children’s Fund, Inc., injected two groups of brain-injured mice with MAPCs two hours after injury and then once again 24 hours later. One group received a dose of 2 million cells per kilogram and the other a dose five times greater.
After four months, those mice that had received the stronger dose not only continued to have less inflammation, but they also showed significant gains in cognitive function. Laboratory examination of the brains of these rodents confirmed that those that had received the higher dose of MAPCs had better brain function than those that had received the lower dose.
According to Cox, “Based on our data, we saw improved spatial learning, improved motor deficits and fewer active antibodies in the mice that were given the stronger concentration of MAPCs.” Cox also indicated that this study indicates that intravenous injection of MAPCs might very well become a viable treatment for people with traumatic brain injury in the future.
Cox, who directs the Pediatric Surgical Translational Laboratories and Pediatric Program in Regenerative Medicine at UTHealth, is a leader in the field of autologous and blood cord stem cells for traumatic brain injury in children and adults. Results from a phase 1 study were published in a March 2011 issue of Neurosurgery, the journal of the Congress of Neurological Surgeons. Cox also directs the Pediatric Trauma Program at Children’s Memorial Hermann Hospital.
Mesenchymal stem cells (MSCs) are found in multiple tissues and locations throughout our bodies, and they have the ability to differentiate into bone, fat, cartilage, and smooth muscle. MSCs also have the ability to suppress unwanted immune responses and inflammation. Therefore, MSCs are prime candidates for regenerative medical treatments.
MSCs have been used to experimentally treat traumatic brain injury (for example, Galindo LT et al., Neurol Res Int 2011;2011:564089). One of the main concerns after traumatic brain injury is damage to the blood brain barrier (BBB). BBB damage allows inflammatory cells to access the brain and further damage it. Therefore, healing the damage to the BBB or protecting the BBB after a traumatic brain injury is vital to the brain after a traumatic brain injury.
After a traumatic brain injury, the vascular system suffers damage and begins to leak. When blood leaks into tissues, it tends to irritate the tissues and damage them. MSCs release a soluble factor known as TIMP3 (tissue metalloproteinase-3) that degrades blood-based proteins known to cause damage to tissues when blood vessels leak. TIMP3 production by MSCs can also protect the BBB from degradation after a traumatic brain injury.
Researchers from the University of Texas Health Sciences Center, UC San Francisco, and two biotechnology companies have examined the protective role of MSCs and one particular protein secreted by MSCs in protecting the BBB after traumatic brain injury.
Shibani Pati, from UC San Francisco, and his collaborators from the University of Texas, Houston, MD Anderson Cancer Center, Amgen, and Blood Systems Research Institute (San Francisco) used MSCs to staunch the increased permeability the BBB after a traumatic brain injury.
They used a mouse model in these experiments and induced traumatic brain injuries in these mice. Then they gave MSCs to some, and soluble TIMP3 to others, and buffer to another group as a control. They discovered that the MSCs mitigated BBB damage after a traumatic brain injury. However, they also found that soluble TIMP3 could also protect the BBB approximately as well as MSCs. This suggested that the TIMP3 secretion by MSCs is the main mechanism by which MSCs protect the BBB after a traumatic brain injury.
To test this hypothesis, Pati and his colleagues administered MSCs to mice that had experienced traumatic brain injury, but they also co-administered a soluble inhibitor to TIMP3. They discovered that this inhibitor completely abolished the ability of MSCs to protect the BBB after a traumatic brain injury. They also found that the main target of TIMP3 was vascular endothelial growth factor. Apparently after a traumatic brain injury, massive release of vascular endothelial growth factor causes the breakdown of BBB structures. TIMP3 degrades vascular endothelial growth factor, which prevents BBB breakdown.
These findings suggest that administration of recombinant proteins such as TIMP3 after a traumatic brain injury can protect the BBB and decrease brain damage. Clinical trial anyone?
A research group at the Salk Institute in San Diego has discovered a new protocol for converting umbilical cord blood cells into neuron-like cells. These new cells could prove valuable for the treatment of a wide variety of neurological conditions, including stroke, traumatic brain injury and spinal cord injury.
Physicians have used umbilical cord blood for more than 20 years to treat many different types of illnesses, including cancer, immune disorders, and blood and metabolic diseases. However, these Salk Institute researchers demonstrated that cord blood (CB) cells can be differentiated into cell types from which brain, spinal and nerve cells arise.
Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory, who led the research team, said: “This study shows for the first time the direct conversion of a pure population of human cord blood cells into cells of neuronal lineage by the forced expression of a single transcription factor.”
Izpisua Belmonte’s group used an engineered retrovirus to introduce a gene called Sox2, a transcription factor that acts as a switch inside cells that converts them into neurons. Therefore, by introducing Sox2 into CB cells, and culturing them in the lab, the cells formed colonies that expressed genes normally found in neurons.
Were these cells actual neurons or faux neurons? Cells might make neuron-specific genes, but they do not assemble those gene products into neuron-specific machinery, then they are not neurons. To if such cells are neurons, they should be able to manipulate the electrical charges across their cell membranes. But subjecting cells to electrophysiological tests, they determined that these new cells, which they called induced neuronal-like cells or iNCs, could transmit electrical impulses. This shows that the iNCs were mature and functional neurons. Next, they implanted these Sox2-transformed CB cells to a mouse brain and found that they integrated into the existing mouse neuronal network and were capable of transmitting electrical signals like mature functional neurons.
Mo Li, a scientist in Belmonte’s lab and a co-first author on the paper, said: “We also show that the CB-derived neuronal cells can be expanded under certain conditions and still retain the ability to differentiate into more mature neurons both in the lab and in a mouse brain. Although the cells we developed were not for a specific lineage-for example, motor neurons or mid-brain neurons-we hope to generate clinically relevant neuronal subtypes in the future.”
Scientists can use these cells in the future to model neurological diseases such as autism, schizophrenia, Parkinson’s or Alzheimer’s disease.
CB cells offer several advantages over other types of stem cells. First, they are not embryonic stem cells and are not controversial. They are more plastic, or flexible, than adult stem cells from sources like bone marrow, which may make them easier to convert into specific cell lineages. The collection of CB cells is safe and painless and poses no risk to the donor, and they can be stored in blood banks for later use.
“If our protocol is developed into a clinical application, it could aid in future cell-replacement therapies,” said Li. “You could search all the cord blood banks in the country to look for a suitable match.”
The injection of stem cells into the carotid artery of brain-injured rats allows the stem cells to move directly to the brain where they greatly enhance brain repair and healing, speeding functional neurological recovery.
In this experiment, traumatic brain injuries were induced in laboratory rats, and seven days later, bone marrow stem cells were isolated and injected into the carotid arteries. Since injections directly into the brain are dangerous and can cause further brain damage, a technique that places stem cells into the peripheral circulation is preferable. However, many animal and clinical studies have shown that stem cells placed into the peripheral circulation tend to get stuck in the lungs, spleen, liver, and other places. For example, Wang W, et al Cell Transplant 2010;19(12):1599-1607 injected bone marrow mesenchymal stem cells into the heart of rats that had recently experienced a heart attack, and found the many of the injected stem cells stayed in the heart, but many others spread to the lungs, spleen, and lungs. This finding has been confirmed by several other studies as well (Zhang H, et al J Thorac Cardiovasc Surg. 2007;134(5):1234-40 & Wang W, et al, Regen Med. 2011;6(2):179-90). Therefore, Osanai’s research group decided to inject stem cells into the blood vessels that directly feed the brain. This way, the stem cells should find their way to the brain without getting lost in general circulation.
Before injection, the bone marrow stem cells were labeled with “quantum dots,” which are a biocompatible, fluorescent semiconductor created using nanotechnology. The quantum dots emit near-infrared light. Near-infrared light has very long wavelengths that penetrate bone and skin, which allowed the researchers to noninvasively monitor the stem cells for four weeks after transplantation.
Using this in vivo combination of optical imaging and carotid injection, Osanai and colleagues observed the bone marrow-derived stem cells enter the brain on the “first pass,” without entering general circulation. Within three hours, the stem cells began to migrate from the smallest brain blood vessels (capillaries) into the area of brain injury.
After four weeks, rats treated with stem cells showed significant recovery of motor function (movement), while untreated rats showed no such recovery. Examination of the treated brains confirmed that the stem cells had transformed into different types of brain cells and participated in healing of the injured brain area.
Stem cells from bone marrow are likely to become an important new treatment for patients with traumatic brain injuries and stroke. Bone marrow stem cells, like the ones used in this study, are a promising source of donor cells. However, despite the many questions that remain regarding the optimal timing, dose, and route of stem cell delivery.
In the new animal experiments, stem cell transplantation was performed one week after a traumatic brain injury, which is a “clinically relevant” time, since it takes at least that long to develop stem cells from bone marrow. Injecting such stem cells into the carotid artery is a relatively simple procedure that delivers the cells directly to the brain.
These experiments also add to the evidence that stem cell treatment can promote healing after traumatic brain injury, with significant recovery of function. Osanai and colleagues wrote that, with the use of in vivo optical imaging, “The present study was the first to successfully track donor cells that were intra-arterially transplanted into the brain of living animals over four weeks.”
Some similar form of imaging technology might be useful in monitoring the effects of stem cell transplantation in humans. However, tracking stem cells in human patients will pose challenges, as the skull and scalp are much thicker in humans than in rats. Clearly further studies are warranted to apply in vivo optical imaging clinically.