Neural regeneration by regionally induced stem cells within poststroke brains: Novel therapy perspectives for stroke patients

Ischemic stroke is a critical disease which causes serious neurological functional loss such as paresis. Hope for novel therapies is based on the increasing evidence of the presence of stem cell populations in the central nervous system(CNS) and the development of stem-cell-based therapies for stroke patients. Although mesenchymal stem cells(MSCs) represented initially a promising cell source,only a few transplanted MSCs were present near the injured areas of the CNS.Thus, regional stem cells that are present and/or induced in the CNS may be ideal when considering a treatment following ischemic stroke. In this context, we have recently showed that injury/ischemia-induced neural stem/progenitor cells(i NSPCs) and injury/ischemia-induced multipotent stem cells(i SCs) are present within post-stroke human brains and post-stroke mouse brains. This indicates that i NSPCs/i SCs could be developed for clinical applications treating patients with stroke. The present study introduces the traits of mouse and human i NSPCs,with a focus on the future perspective for CNS regenerative therapies using novel i NSPCs/i SCs.     

Mesenchymal stem cell therapy of brain ischemic stroke in rats

Mesenchymal stem cell (MSCs)-based therapy is a promising attempt to improve the recovery after stroke. Our experiments were carried out on inbred Wistar-Kyoto rats. MSCs were isolated, expanded in culture, and labeled with vital fluorescent dye PKH-26. Animals were subjected to middle cerebral artery occlusion (MCAO). After three days, MCAO 5 × 10⁶ isolated MSCs were injected into the tail vein of the experimental rats. The control animal group received PBS injections (negative control). Therapy results were evaluated by the following parameters: behavioral and neurological testing, the inured brain areas, damaged brain structures, neuron state, and vessel quantity in the region close to with necrosis zone. It was shown that control animals (PBS injection) did not return to their initial behavioral and neurological state within 6 weeks, while the experimental animals (MSCs injection), within 2–3 weeks after MCAO, had parameters like intact rats. The size of the damaged region in the control group was larger than in the experimental group by a factor of approximately 1.3. The damage in MSC-treated rats was limited to the neocortex; caudate nucleus, capsula externa and piriform cortex remained uninjured. The small vessel quantity in the “border” regions was twice as high as compared to the control group and approximately equal to the number of vessels in an intact brain. For the first time, we demonstrated that the vessel quantity in the neocortex and caudate nucleus of the contralateral hemisphere after MSC transplantation was twice as high as in control rats. It is concluded that the MSC transplantation exerts a beneficial influence upon the brain tissue reparation after stroke.     

Immunomodulation: The next target of mesenchymal stem cell-derived exosomes in the context of ischemic stroke

Ischemic stroke(IS) is the most prevalent form of brain disease, characterized by high morbidity, disability, and mortality. However, there is still a lack of ideal prevention and treatment measures in clinical practice. Notably, the transplantation therapy of mesenchymal stem cells(MSCs) has been a hot research topic in stroke. Nevertheless, there are risks associated with this cell therapy, including tumor formation, coagulation dysfunction, and vascular occlusion. Also, a growing number of st...     

Neural stem cell therapy for brain disease

Brain diseases, including brain tumors, neurodegenerative disorders, cerebrovascular diseases, and traumatic brain injuries, are among the major disorders influencing human health, currently with no effective therapy. Due to the low regeneration capacity of neurons, insufficient secretion of neurotrophic factors, and the aggravation of ischemia and hypoxia after nerve injury, irreversible loss of functional neurons and nerve tissue damage occurs. This damage is difficult to repair and regenerate the central nervous system after injury. Neural stem cells (NSCs) are pluripotent stem cells that only exist in the central nervous system. They have good self-renewal potential and ability to differentiate into neurons, astrocytes, and oligodendrocytes and improve the cellular microenvironment. NSC transplantation approaches have been made for various neurodegenerative disorders based on their regenerative potential. This review summarizes and discusses the characteristics of NSCs, and the advantages and effects of NSCs in the treatment of brain diseases and limitations of NSC transplantation that need to be addressed for the treatment of brain diseases in the future.     

Fetal stem cell transplantation: Past,present, and future

Since 1928, human fetal tissues and stem cells have been used worldwide to treat various conditions. Although the transplantation of the fetal midbrain substantia nigra and dopaminergic neurons in patients suffering from Parkinson's disease is particularly noteworthy, the history of other types of grafts, such as those of the fetal liver, thymus, and pancreas, should be addressed as there are many lessons to be learnt for future stem cell transplantation. This report describes previous practices and complications that led to current clinical trials of isolated fetal stem cells and embryonic stem(ES) cells. Moreover, strategies for transplantation are considered, with a particular focus on donor cells, cell processing, and the therapeutic cell niche, in addition to ethical issues associated with fetal origin. With the advent of autologous induced pluripotent stem cells and ES cells, clinical dependence on fetal transplantation is expected to gradually decline due to lasting ethical controversies, despite landmark achievements.     

神经干细胞脑内移植后的存活、迁移和分化

从胚胎或成体大鼠脑组织、人胚脑组织均能分离到神经干细胞 ,将它们进行体外原代培养扩增或永生化后植入脑内 ,均能观察到其在脑内的迁移和分化现象。其分化能力主要取决于移植部位的脑内微环境 ,但这种影响作用是相对的。同时 ,体外培养环境如培养时间和细胞融合程度、维甲酸类诱导分化剂处理、NGF转导处理再移植或与嗜铬细胞 (分泌NGF)共移植等 ,也能决定神经干细胞脑内移植后向神经元方向分化的能力。神经干细胞移植为中枢神经系统功能重建和神经再生带来新的希望。     

The stem cell secretome and its role in brain repair

Compelling evidence exists that non-haematopoietic stem cells, including mesenchymal (MSCs) and neural/progenitor stem cells (NPCs), exert a substantial beneficial and therapeutic effect after transplantation in experimental central nervous system (CNS) disease models through the secretion of immune modulatory or neurotrophic paracrine factors.     

Regenerative therapy for neuronal diseases with transplantation of somatic stem cells

Pluripotent stem cells, which are capable of differentiating in various species of cells, are hoped to be donor cells in transplantation in regenerative medicine. Embryonic stem (ES) cells and induced pluripotent stem cells have the potential to differentiate in approximately all species of cells. However, the proliferating ability of these cells is high and the cancer formation ability is also recognized. In addition, ethical problems exist in using ES cells. Somatic stem cells with the ability to differentiate in various species of cells have been used as donor cells for neuronal diseases, such as amyotrophic lateral sclerosis, spinal cord injury, Alzheimer disease, cerebral infarction and congenital neuronal diseases. Human mesenchymal stem cells derived from bone marrow, adipose tissue, dermal tissue, umbilical cord blood and placenta are usually used for intractable neuronal diseases as somatic stem cells, while neural progenitor/stem cells and retinal progenitor/stem cells are used for a few congenital neuronal diseases and retinal degenerative disease, respectively. However, non-treated somatic stem cells seldom differentiate to neural cells in recipient neural tissue. Therefore, the contribution to neuronal regeneration using non-treated somatic stem cells has been poor and various differential trials, such as the addition of neurotrophic factors, gene transfer, peptide transfer for neuronal differentiation of somatic stem cells, have been performed. Here, the recent progress of regenerative therapies using various somatic stem cells is described.     

Dynamics of morphological changes after transplantation of mesenchymal stem cells in rat brain provoked by stroke

The study of the dynamic of morphological changes in the brain after ischemic stroke is very important for the preclinical trial of mesenchymal stem cell (MSC) therapy for this widespread disease. Experiments were carried out in inbred Wistar-Kyoto rats. MSCs were isolated, expanded in culture, and labeled with the vital fluorescent dye PKH-26. Animals were subjected to middle cerebral artery occlusion (MCAO), followed by an injection of 5 × 10⁶ rat MSCs into the tail vein on the day of MCAO. Control group animals received PBS injection (negative control). Animals were sacrificed at 1, 2, 3, and 5 days and 1, 2, 4, and 6 weeks after the operation. MSCs were revealed in the brain on the third day after transplantation as being distributed around brain vessels both in the ipsilateral and contralateral hemispheres. This pattern of distribution remained unchanged throughout six weeks of observation. It was demonstrated that the inflammation process and scar formation in the cell therapy group were progressing at a rate 25–30% faster than in the control group. MSC transplantation stimulated endogenous stem cell proliferation in the subependimal zone of lateral ventricles (subventricular zone). In addition, MSC injection caused a neuroprotecting effect; most penumbra neurons retained their structure in cell therapy group, whereas in control group, animal penumbra neurons died or showed signs of serious damage.     

Kallikrein-kinin in stem cell therapy

The tissue kallikrein-kinin system exerts a wide spectrum of biological activities in the cardiovascular, renal and central nervous systems. Tissue kallikrein-kinin modulates the proliferation, viability, mobility and functional activity of certain stem cell populations, namely mesenchymal stem cells(MSCs), endothelial progenitor cells(EPCs), mononuclear cell subsets and neural stem cells. Stimulation of these stem cells by tissue kallikrein-kinin may lead to protection against renal, cardiovascular and neural damage by inhibiting apoptosis, inflammation, fibrosis and oxidative stress and promoting neovascularization. Moreover, MSCs and EPCs genetically modified with tissue kallikrein are resistant to hypoxia- and oxidative stress-induced apoptosis, and offer enhanced protective actions in animal models of heart and kidney injury and hindlimb ischemia. In addition, activation of the plasma kallikrein-kinin system promotes EPC recruitment to the inflamed synovium of arthritic rats. Conversely, cleaved high molecular weight kininogen, a product of plasma kallikrein, reduces the viability and vasculogenic activity of EPCs. Therefore, kallikrein-kinin provides a new approach in enhancing the efficacy of stem cell therapy for human diseases.     

Bone marrow mesenchymal stem cell therapy regulates gut microbiota to improve post-stroke neurological function recovery in rats

BACKGROUNDAs a cellular mode of therapy, bone marrow mesenchymal stem cells (BMSCs) are used to treat stroke. However, their mechanisms in stroke treatment have not been established. Recent evidence suggests that regulation of dysregulated gut flora after stroke affects stroke outcomes.AIMTo investigate the effects of BMSCs on gut microbiota after ischemic stroke.METHODSA total of 30 Sprague-Dawley rats were randomly divided into three groups, including sham operation control group, transient middle cerebral artery occlusion (MCAO) group, and MCAO with BMSC treatment group. The modified Neurological Severity Score (mNSS), beam walking test, and Morris water maze test were used to evaluate neurological function recovery after BMSC transplantation. Nissl staining was performed to elucidate on the pathology of nerve cells in the hippocampus. Feces from each group of rats were collected and analyzed by 16s rDNA sequencing.RESULTSBMSC transplantation significantly reduced mNSS (P < 0.01). Rats performed better in the beam walking test in the BMSC group than in the MCAO group (P < 0.01). The Morris water maze test revealed that the BMSC treatment group exhibited a significant improvement in learning and memory. Nissl staining for neuronal damage assessment after stroke showed that in the BMSC group, cells were orderly arranged with significantly reduced necrosis. Moreover, BMSCs regulated microbial structure composition. In rats treated with BMSCs, the abundance of potential short-chain fatty acid producing bacteria and Lactobacillus was increased.CONCLUSIONBMSC transplantation is a potential therapeutic option for ischemic stroke, and it promotes neurological functions by regulating gut microbiota dysbiosis.     

Heat shock protein 27 as a neuroprotective biomarker and a suitable target for stem cell therapy and pharmacotherapy in ischemic stroke

Ischemic stroke is a major common cause of death and long‐term disability worldwide. Several pathophysiological events including excitotoxicity, oxidative/nitrative stress, inflammation, and apoptosis are involved in ischemic injuries. Recently, the molecular mechanisms involved in cerebral ischemia through a focus on a member of small heat shock proteins family, Hsp27, has been developed. Notably, following exposure to ischemia, Hsp27 expression in the brain could be increased rather than the normal condition and it may play an important role in neuroprotection after ischemic stroke. The neuroprotection effects of Hsp27 may arise from its anti‐oxidant, anti‐inflammatory, anti‐apoptotic, and chaperonic properties. Moreover, some therapeutic strategies such as stem cell therapy and pharmacotherapy have been developed with Hsp27 targeting. In this review, we describe the function and structure of Hsp27 and its possible role in neuroprotection after ischemic stroke. Finally, we present current studies in stroke therapy, which focused on Hsp27 targeting.     

The roles of mesenchymal stem cells (MSCs) therapy in ischemic heart diseases

Growing cell-based myocardial therapies which could lead to successful myocardial repair attracts medical interest. Even more intriguing is the observation that MSCs appears to be a more potent material among kinds of stem cells for the transplantation, the mechanism for this benefit remains unclear. However, the therapeutic contribution of MSCs to myocardial repair can be caused by multiple factors including: direct differentiation into cardiac tissue including cardiomyocytes, smooth muscle cell, and vascular endothelial cells; secreting a variety of cytokines and growth factors that have paracrine activities; spontaneous cell fusion; and stimulating endogenous repair. In addition, MSCs possess local immunosuppressive properties, and MSCs mobilization is widely used clinically for transplantation. We will discusses the potential mechanisms of MSCs repair for ischemic heart diseases.     

Exosomes for drug delivery — a novel application for the mesenchymal stem cell

Exosomes are the most extensively characterized class of secreted membrane vesicles that carry proteins and RNAs for intercellular communication. They are increasingly seen as possible alternatives to liposomes as drug delivery vehicles. Like liposomes, they could deliver their cargo across the plasma membrane and provide a barrier against premature transformation and elimination. In addition, these naturally-occurring secreted membrane vesicles are less toxic and better tolerated in the body as evidenced by their ubiquitous presence in biological fluids, and have an intrinsic homing ability. They are also amenable to in vivo and in vitro loading of therapeutic agents, and membrane modifications to enhance tissue-specific homing. Here we propose human mesenchymal stem cells as the ideal cell source of exosomes for drug delivery. Mesenchymal stem cell transplantation for various disease indications has been extensively tested and shown to be safe in numerous clinical trials. These cells are also prolific producers of immunologically inert exosomes. Immortalization of these cells does not compromise the quantity or quality of exosome production, thus enabling infinite and reproducible exosome production from a single cell clone.     

Adult stem cells in neural repair: Current options,limitations and perspectives

Stem cells represent a promising step for the future of regenerative medicine. As they are able to differentiate into any cell type, tissue or organ, these cells are great candidates for treatments against the worst diseasesthat defy doctors and researchers around the world. Stem cells can be divided into three main groups:(1) embryonic stem cells;(2) fetal stem cells; and(3) adult stem cells. In terms of their capacity for proliferation, stem cells are also classified as totipotent, pluripotent or multipotent. Adult stem cells, also known as somatic cells, are found in various regions of the adult organism, such as bone marrow, skin, eyes, viscera and brain. They can differentiate into unipotent cells of the residing tissue, generally for the purpose of repair. These cells represent an excellent choice in regenerative medicine, every patient can be a donor of adult stem cells to provide a more customized and efficient therapy against various diseases, in other words, they allow the opportunity of autologous transplantation. But in order to start clinical trials and achieve great results, we need to understand how these cells interact with the host tissue, how they can manipulate or be manipulated by the microenvironment where they will be transplanted and for how long they can maintain their multipotent state to provide a full regeneration.     

Treatment of acute ischemic stroke by minimally manipulated umbilical cord-derived mesenchymal stem cells transplantation: A case report

BACKGROUNDStroke is one of the major causes of disability and death worldwide. Some treatments for stroke exist, but existing treatment methods have limitations such as difficulty in the regeneration of damaged neuronal cells of the brain. Recently, mesenchymal stem cells (MSCs) have been studied as a therapeutic alternative for stroke, and various preclinical and case studies have been reported.CASE SUMMARYA 55-year-old man suffered an acute stroke, causing paralysis in the left upper and lower limbs. He intravenously transplanted the minimally manipulated human umbilical cord-derived MSCs (MM-UC-MSCs) twice with an 8-d interval. At 65 wk after transplantation, the patient returned to his previous occupation as a veterinarian with no adverse reactions.CONCLUSIONMM-UC-MSCs transplantation potentially treats patients who suffer from acute ischemic stroke.     

Recovery of neurological function of ischemic stroke by application of conditioned medium of bone marrow mesenchymal stem cells derived from normal and cerebral ischemia rats

Background

Several lines of evidence have demonstrated that bone marrow-derived mesenchymal stem cells (BM-MSC) release bioactive factors and provide neuroprotection for CNS injury. However, it remains elusive whether BM-MSC derived from healthy donors or stroke patients provides equal therapeutic potential. The present work aims to characterize BM-MSC prepared from normal healthy rats (NormBM-MSC) and cerebral ischemia rats (IschBM-MSC), and examine the effects of their conditioned medium (Cm) on ischemic stroke animal model.

Results

Isolated NormBM-MSC or IschBM-MSC formed fibroblastic like morphology and expressed CD29, CD90 and CD44 but failed to express the hematopoietic marker CD34. The number of colony formation of BM-MSC was more abundant in IschBM-MSC than in NormBM-MSC. This is in contrast to the amount of Ficoll-fractionated mononuclear cells from normal donor and ischemic rats. The effect of cm of BM-MSC was further examined in cultures and in middle cerebral artery occlusion (MCAo) animal model. Both NormBM-MSC Cm and IschBM-MSC Cm effectively increased neuronal connection and survival in mixed neuron-glial cultures. In vivo, intravenous infusion of NormBM-MSC Cm and IschBM-MSC Cm after stroke onset remarkably improved functional recovery. Furthermore, NormBM-MSC Cm and IschBM-MSC Cm increased neurogenesis and attenuated microglia/ macrophage infiltration in MCAo rat brains.

Conclusions

Our data suggest equal effectiveness of BM-MSC Cm derived from ischemic animals or from a normal population. Our results thus revealed the potential of BM-MSC Cm on treatment of ischemic stroke.     

对比不同类型干细胞对于缺血性脑卒中治疗的研究进展

成人中枢神经系统存在着一定量的神经干细胞,其具有两大关键能力;自我更新和多向分化潜能。缺血性脑卒中是一种由于由脑血流的缺失或减少引起的脑动脉闭塞,进而导致脑组织梗死的脑血管疾病。虽然对于脑损伤的药物治疗已经取得了一定的成果,但目前以干细胞为基础的治疗方法仍成为了研究热点。无论是内源性神经干细胞还是外源性神经干细胞移植均可在脑损伤后向远端损伤区迁移并分化成新的神经细胞,从而在中枢神经系统疾病尤其是脑梗死后进行组织修复和功能恢复。因此在这篇综述中,我们主要探讨不同类型的干细胞对脑梗死介导的脑损伤的应用潜能,对比不同类型干细胞对缺血性脑卒中的治疗优缺点。     

Stem cell-based cell therapy for neuroprotection in stroke: A review

Neurological disorders, such as stroke, are triggered by a loss of neurons and glial cells. Ischemic stroke remains a substantial problem for industrialized countries. Over the previous few decades our understanding about the pathophysiology of stroke has enhanced, nevertheless, more awareness is required to advance the field of stroke recovery. Existing therapies are incapable to adequately relief the disease outcome and are not appropriate to all patients. Meanwhile, the majority of patients continue to show neurological deficits even subsequent effective thrombolysis, recuperative therapies are immediately required that stimulate brain remodeling and repair once stroke damage has happened. Cell therapy is emergent as a hopeful new modality for increasing neurological recovery in ischemic stroke. Numerous types of stem cells from various sources have been identified and their possibility and efficiency for the treatment of stroke have been investigated. Stem cell therapy in patients with stroke using adult stem cells have been first practiced in clinical trials since 15 years ago. Even though stem cells have revealed a hopeful role in ischemic stroke in investigational studies besides early clinical pilot studies, cellular therapy in human is still at a primary stage. In this review, we summarize the types of stem cells, various delivery routes, and clinical application of stem cell-based therapy for stroke treatment.