The Dark Side of the Force - Constraints and Complications of Cell Therapies for Stroke

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

Glial Cell Reprogramming in Ischemic Stroke: A Review of Recent Advancements and Translational Challenges

Ischemic stroke, the second leading cause of death worldwide and the leading cause of long-term disabilities, presents a significant global health challenge, particularly in aging populations where the risk and severity of cerebrovascular events are significantly increased. The aftermath of stroke involves neuronal loss in the infarct core and reactive astrocyte proliferation, disrupting the neurovascular unit, especially in aged brains. Restoring the balance between neurons and non-neuronal cells within the perilesional area is crucial for post-stroke recovery. The aged post-stroke brain mounts a fulminant proliferative astroglial response, leading to gliotic scarring that prevents neural regeneration. While countless therapeutic techniques have been attempted for decades with limited success, alternative strategies aim to transform inhibitory gliotic tissue into an environment conducive to neuronal regeneration and axonal growth through genetic conversion of astrocytes into neurons. This concept gained momentum following discoveries that in vivo direct lineage reprogramming in the adult mammalian brain is a feasible strategy for reprogramming non-neuronal cells into neurons, circumventing the need for cell transplantation. Recent advancements in glial cell reprogramming, including transcription factor-based methods with factors like NeuroD1, Ascl1, and Neurogenin2, as well as small molecule-induced reprogramming and chemical induction, show promise in converting glial cells into functional neurons. These approaches leverage the brain's intrinsic plasticity for neuronal replacement and circuit restoration. However, applying these genetic conversion therapies in the aged, post-stroke brain faces significant challenges, such as the hostile inflammatory environment and compromised regenerative capacity. There is a critical need for safe and efficient delivery methods, including viral and non-viral vectors, to ensure targeted and sustained expression of reprogramming factors. Moreover, addressing the translational gap between preclinical successes and clinical applications is essential, emphasizing the necessity for robust stroke models that replicate human pathophysiology. Ethical considerations and biosafety concerns are critically evaluated, particularly regarding the long-term effects and potential risks of genetic reprogramming. By integrating recent research findings, this comprehensive review provides an in-depth understanding of the current landscape and future prospects of genetic conversion therapy for ischemic stroke rehabilitation, highlighting the potential to enhance personalized stroke management and regenerative strategies through innovative approaches.

BMSCs-derived small extracellular vesicles antagonize cerebral endothelial Caveolin-1 driven autophagic degradation of tight-junction proteins to protect blood-brain barrier post-stroke

Bone marrow mesenchymal stem cells (BMSCs) -derived extracellular vesicles (EVs), especially small EVs (sEVs), were vastly reported to enable multiple restorative effects on ischemic stroke, yet the protective mechanism of blood-brain barrier (BBB) has not been fully illustrated. In the present study, we investigated the therapeutic effects and mechanism of BMSCs-derived sEVs on BBB injury after ischemic stroke. In-vivo, administering sEVs to transient middle cerebral artery occlusion (tMCAo) mice mitigated the brain infarct volume, BBB permeability and neural apoptosis, and improved the cerebral blood flow perfusion and neurological function. Simultaneously, cerebral vascular endothelial overexpressed Caveolin-1 (Cav-1) together with its strong co-localization with autophagosome protein LC3B were suppressed, and ZO-1 and Occludin expressions were enhanced, whose results were consistent with those of oxygen-glucose-deprivation/reperfusion (OGD/R)-insulted brain endothelial cells (BECs) in vitro. Furthermore, by employing Cav-1 siRNA and pcDNA3.1 transfection, Co-immunoprecipitation, cycloheximide assay, and molecular docking, it proved that brain endothelial Cav-1 was an essential upstream of autophagy activation, contributing to tight-junction proteins delegation via the autophagy-lysosomal pathway. Altogether, our study demonstrates the novel mechanism of Cav-1-dependent tight-junction proteins autophagic disruption on BBB integrity after ischemic stroke, and BMSC-sEVs treatment can reverse such hazard cascades.

Cutting-edge regenerative therapy for Hirschsprung disease and its allied disorders

Hirschsprung disease (HSCR) and its associated disorders (AD-HSCR) often result in severe hypoperistalsis caused by enteric neuropathy, mesenchymopathy, and myopathy. Notably, HSCR involving the small intestine, isolated hypoganglionosis, chronic idiopathic intestinal pseudo-obstruction, and megacystis-microcolon-intestinal hypoperistalsis syndrome carry a poor prognosis. Ultimately, small-bowel transplantation (SBTx) is necessary for refractory cases, but it is highly invasive and outcomes are less than optimal, despite advances in surgical techniques and management. Thus, regenerative therapy has come to light as a potential form of treatment involving regeneration of the enteric nervous system, mesenchyme, and smooth muscle in affected areas. We review the cutting-edge regenerative therapeutic approaches for managing HSCR and AD-HSCR, including the use of enteric nervous system progenitor cells, embryonic stem cells, induced pluripotent stem cells, and mesenchymal stem cells as cell sources, the recipient intestine's microenvironment, and transplantation methods. Perspectives on the future of these treatments are also discussed.

The application of mesenchymal stem cells in the treatment of traumatic brain injury: Mechanisms, results, and problems

Mesenchymal stem cells (MSCs) are multipotent stromal cells that can be derived from a wide variety of human tissues and organs. They can differentiate into a variety of cell types, including osteoblasts, adipocytes, and chondrocytes, and thus show great potential in regenerative medicine. Traumatic brain injury (TBI) is an organic injury to brain tissue with a high rate of disability and death caused by an external impact or concussive force acting directly or indirectly on the head. The current treatment of TBI mainly includes symptomatic, pharmacological, and rehabilitation treatment. Although some efficacy has been achieved, the definitive recovery effect on neural tissue is still limited. Recent studies have shown that MSC therapies are more effective than traditional treatment strategies due to their strong multi-directional differentiation potential, self-renewal capacity, and low immunogenicity and homing properties, thus MSCs are considered to play an important role and are an ideal cell for the treatment of injurious diseases, including TBI. In this paper, we systematically reviewed the role and mechanisms of MSCs and MSC-derived exosomes in the treatment of TBI, thereby providing new insights into the clinical applications of MSCs and MSC-derived exosomes in the treatment of central nervous system disorders.

Secretome of brain microvascular endothelial cells promotes endothelial barrier tightness and protects against hypoxia-induced vascular leakage

Cell-based therapeutic strategies have been proposed as an alternative for brain and blood vessels repair after stroke, but their clinical application is hampered by potential adverse effects. We therefore tested the hypothesis that secretome of these cells might be used instead to still focus on cell-based therapeutic strategies. We therefore characterized the composition and the effect of the secretome of brain microvascular endothelial cells (BMECs) on primary in vitro human models of angiogenesis and vascular barrier. Two different secretome batches produced in high scale (scHSP) were analysed by mass spectrometry. Human primary CD34+-derived endothelial cells (CD34+-ECs) were used as well as in vitro models of EC monolayer (CMECs) and blood-brain barrier (BBB). Cells were also exposed to oxygen-glucose deprivation (OGD) conditions and treated with scHSP during reoxygenation. Protein yield and composition of scHSP batches showed good reproducibility. scHSP increased CD34+-EC proliferation, tubulogenesis, and migration. Proteomic analysis of scHSP revealed the presence of growth factors and proteins modulating cell metabolism and inflammatory pathways. scHSP improved the integrity of CMECs, and upregulated the expression of junctional proteins. Such effects were mediated through the activation of the interferon pathway and downregulation of Wnt signalling. Furthermore, OGD altered the permeability of both CMECs and BBB, while scHSP prevented the OGD-induced vascular leakage in both models. These effects were mediated through upregulation of junctional proteins and regulation of MAPK/VEGFR2. Finally, our results highlight the possibility of using secretome from BMECs as a therapeutic alternative to promote brain angiogenesis and to protect from ischemia-induced vascular leakage.

Therapeutic potential of extracellular vesicles derived from human amniotic epithelial cells for perinatal cerebral and pulmonary injury

Lung and brain injury that occurs during the perinatal period leads to lifelong disability and is often driven and/or exacerbated by inflammation. Human amniotic epithelial cells (hAEC), which demonstrate immunomodulatory, anti-fibrotic, and regenerative capabilities, are being explored as a therapeutic candidate for perinatal injury. However, limitations regarding scalable manufacturing, storage, transport, and dose-related toxicity have impeded clinical translation. Isolated therapeutic extracellular vesicles (EVs) from stem and stem-like cells are thought to be key paracrine mediators of therapeutic efficacy. The unique characteristics of EVs suggest that they potentially circumvent the limitations of traditional cell-based therapies. However, given the novelty of EVs as a therapeutic, recommendations around ideal methods of production, isolation, storage, and delivery have not yet been created by regulatory agencies. In this concise review, we discuss the pertinence and limitations of cell-based therapeutics in perinatal medicine. We also review the preclinical evidence supporting the use of therapeutic EVs for perinatal therapy. Further, we summarize the arising considerations regarding adequate cell source, biodistribution, isolation and storage methods, and regulatory roadblocks for the development of therapeutic EVs.

Adipose Tissue-Derived Mesenchymal Stromal Cells Modulate Inflammatory Response and Improve Allograft Islet Transplant in Mice Model of Type 1 Diabetes

OBJECTIVE

Type 1 diabetes mellitus (T1DM) is an autoimmune disease where immune cells attack insulin-producing beta cells. Islet transplantation is a promising treatment for T1DM. This study aims to evaluate the effects of adipose tissue-derived mesenchymal stem cells (AT-MSCs) in combination with pancreatic islet transplantation using hydrogel.

METHODS

T1DM mouse model was established using streptozotocin (STZ). Islets and AT-MSCs were co-embedded in a hydrogel and transplanted into diabetic mice. Five groups with six animals in each (control, hydrogel alone, AT-MSCs embedded hydrogel, islet embedded in hydrogel, and islet + AT-MSCs co-imbedded into a hydrogel) were evaluated in terms of blood glucose, insulin levels and serum and lavage cytokine production.

RESULTS

During 32 days, blood glucose levels decreased from over 400 mg/dl to less than 150 mg/dl in the transplanted mice. Analysis showed increased transformation growth factor beta (TGF-β1) and IL-4 levels, while IL-17 and IFN-γ levels significantly decreased in the MSC-treated groups.

CONCLUSION

These findings suggest that using AT-MSCs with hydrogel could be a beneficial alternative for enhancing pancreatic islet engraftment and function.

Macrophage based drug delivery: Key challenges and strategies

As a natural immune cell and antigen presenting cell, macrophages have been studied and engineered to treat human diseases. Macrophages are well-suited for use as drug carriers because of their biological characteristics, such as excellent biocompatibility, long circulation, intrinsic inflammatory homing and phagocytosis. Meanwhile, macrophages' uniquely high plasticity and easy re-education polarization facilitates their use as part of efficacious therapeutics for the treatment of inflammatory diseases or tumors. Although recent studies have demonstrated promising advances in macrophage-based drug delivery, several challenges currently hinder further improvement of therapeutic effect and clinical application. This article focuses on the main challenges of utilizing macrophage-based drug delivery, from the selection of macrophage sources, drug loading, and maintenance of macrophage phenotypes, to drug migration and release at target sites. In addition, corresponding strategies and insights related to these challenges are described. Finally, we also provide perspective on shortcomings on the road to clinical translation and production.

Neurorestorative Approaches for Ischemic StrokeChallenges, Opportunities, and Recent Advances

Despite recent advances in acute stroke management, most patients experiencing a stroke will suffer from residual brain damage and functional impairment. Addressing those residual deficits would require neurorestoration, i.e., rebuilding brain tissue to repair the structural brain damage caused by stroke. However, there are major pathobiological, anatomical and technological hurdles making neurorestorative approaches remarkably challenging, and true neurorestoration after larger ischemic lesions could not yet be achieved. On the other hand, there has been steady advancement in our understanding of the limits of tissue regeneration in the adult mammalian brain as well as of the fundamental organization of brain tissue growth during embryo- and ontogenesis. This has been paralleled by the development of novel animal models to study stroke, advancement of biomaterials that can be used to support neurorestoration, and in stem cell technologies. This review gives a detailed explanation of the major hurdles so far preventing the achievement of neurorestoration after stroke. It will also describe novel concepts and advancements in biomaterial science, brain organoid culturing, and animal modeling that may enable the investigation of post-stroke neurorestorative approaches in translationally relevant setups. Finally, there will be a review of recent achievements in experimental studies that have the potential to be the starting point of research and development activities that may eventually bring post-stroke neurorestoration within reach.

Pericyte derivation and transplantation for blood-CNS barrier reconstitution in CNS disorders

Disruption of the blood-central nervous system barrier (BCB) is increasingly recognized as a pathological factor in diseases and trauma of the central nervous system. Despite the neuropathological impact, current treatment modalities do not target the BCB; strategies to reconstitute the impaired BCB have been restricted to nutritional and dietary remedies. As an integral cell type in the neurovascular unit, pericytes are crucial to the development, maintenance, and repair of the BCB. As such, pericytes are well poised as cellular agents for reconstitution of the impaired BCB. Here, we summarize recent revelations regarding the role of BCB disruption in diseases and trauma of the central nervous system and highlight how pericytes are harnessed to provide targeted therapeutic effect in each case. This review will also address how recent advances in pericyte derivation strategies can serve to overcome practical hurdles in the clinical use of pericytes.

Pulmonary passage of canine adipose tissue-derived mesenchymal stem cells through intravenous transplantation in mouse model

IMPORTANCE

The intravenous administration of adipose tissue-derived mesenchymal stem cells (AdMSCs) in veterinary medicine is an attractive treatment option. On the other hand, it can result in severe complications, including pulmonary thromboembolism (PTE).

OBJECTIVE

The present study assessed the occurrence of PTE after the intravenous infusion of canine AdMSCs (cAdMSCs) into experimental animals.

METHODS

Five-week-old male BALB/c hairless mice were categorized into groups labeled A to G. In the control group (A), fluorescently stained 2 × 106 cAdMSCs were diluted in 200 μL of suspension and injected into the tail vein as a single bolus. The remaining groups included the following: group B with 5 × 106 cells, group C with 3 × 106 cells, group D with 1 × 106 cells, group E with 1 × 106 cells injected twice with a one-day interval, group F with 2 × 106 cells in 100 μL of suspension, and group G with 2 × 106 cells in 300 μL of suspension.

RESULTS

Group D achieved a 100% survival rate, while none of the subjects in groups B and C survived (p = 0.002). Blood tests revealed a tendency for the D-dimer levels to increase as the cell dose increased (p = 0.006). The platelet count was higher in the low cell concentration groups and lower in the high cell concentration groups (p = 0.028). A histological examination revealed PTE in most deceased subjects (96.30%).

CONCLUSIONS AND RELEVANCE

PTE was verified, and various variables were identified as potential contributing factors, including the cell dose, injection frequency, and suspension volume.

Safety and efficacy of bone marrow mononuclear cell therapy for ischemic stroke recovery: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Cell-based therapy represents a potential treatment for ischemic stroke (IS). Here, we performed a systematic review and meta-analysis to summarize the evidence provided by randomized controlled trials (RCTs) for the transplantation of bone marrow mononuclear cells (BMMNCs) in patients with IS in any phase after stroke.

METHODS

We searched several databases for relevant articles up to the 10th of March 2023, including MEDLINE, EMBASE, the Cochrane Library, and ClinicalTrials.gov. Subgroup analyses were implemented to evaluate the dose and route of BMMNC administration. Statistical data were analyzed by Review Manager version 5.3 software.

RESULTS

Six RCTs were included in this article, including 177 patients who were treated by the transplantation of BMMNCs and 166 patients who received medical treatment. The three-month National Institutes of Health Stroke Scale (NIHSS) score indicated a favorable outcome for the BMMNC transplantation group (standardized mean difference (SMD), - 0.34; 95% confidence interval (CI), - 0.57 to - 0.11; P = 0.004). There were no significant differences between the two groups at six months post-transplantation with regards to NIHSS score (SMD 0.00; 95% CI - 0.26 to 0.27; P = 0.97), modified Rankin Scale (risk ratio (RR) 1.10; 95% CI 0.75 to 1.63; P = 0.62), Barthel Index change (SMD 0.68; 95% CI - 0.59 to 1.95; P = 0.29), and infarct volume change (SMD - 0.08; 95% CI - 0.42 to 0.26; P = 0.64). In addition, there was no significant difference between the two groups in terms of safety outcome (RR 1.24; 95% CI 0.80 to 1.91; P = 0.33).

CONCLUSION

Our meta-analysis demonstrated that the transplantation of BMMNCs was safe; however, the efficacy of this procedure requires further validation in larger RTCs.

Extracellular Vesicles Maintain Blood-Brain Barrier Integrity by the Suppression of Caveolin-1/CD147/VEGFR2/MMP Pathway After Ischemic Stroke

Background

Ischemic stroke (IS) causes tragic death and disability worldwide. However, effective therapeutic interventions are finite. After IS, blood-brain barrier (BBB) integrity is disrupted, resulting in deteriorating neurological function. As a novel therapeutic, extracellular vesicles (EVs) have shown ideal restorative effects on BBB integrity post-stroke; however, the definite mechanisms remain ambiguous. In the present study, we investigated the curative effects and the mechanisms of EVs derived from bone marrow mesenchymal stem cells and brain endothelial cells (BMSC-EVs and BEC-EVs) on BBB integrity after acute IS.

Methods

EVs were isolated from BMSCs and BECs, and we investigated the therapeutic effect in vitro oxygen-glucose deprivation (OGD) insulted BECs model and in vivo rat middle cerebral artery occlusion (MCAo) model. The cell monolayer leakage, tight junction expression, and metalloproteinase (MMP) activity were evaluated, and rat brain infarct volume and neurological function were also analyzed.

Results

The administration of two kinds of EVs not only enhanced ZO-1 and Occludin expressions but also reduced the permeability and the activity of MMP-2/9 in OGD-insulted BECs. The amelioration of the cerebral infarction, BBB leakage, neurological function deficits, and the increasing ZO-1 and Occludin levels, as well as MMP activity inhibition was observed in MCAo rats. Additionally, the increased levels of Caveolin-1, CD147, vascular endothelial growth factor receptor 2 (VEGFR2), and vascular endothelial growth factor A (VEGFA) in isolated brain microvessels were downregulated after EVs treatment. In vitro, the employment of Caveolin-1 and CD147 siRNA partly suppressed the expressions of VEGFR2, VEGFA and MMP-2/9 activity and reduced the leakage of OGD insulted BECs and enhanced ZO-1 and Occludin expressions.

Conclusion

Our study firstly demonstrates that BEC and BMSC-EVs administrations maintain BBB integrity via the suppression of Caveolin-1/CD147/VEGFR2/MMP pathway after IS, and the efficacy of BMSC-EVs is superior to that of BEC-EVs.

Mesenchymal stem cells in the treatment of ischemic stroke

Over the past two decades, multiple preclinical studies have shown that transplantation of mesenchymal stem cells leads to a pronounced positive effect in animals with experimental stroke. Based on the promising results of preclinical studies, several clinical trials on the transplantation of mesenchymal stem cells to stroke patients have also been conducted. In this review, we present and analyze the results of completed clinical trials dedicated to the mesenchymal stem cells transplantation in patients with ischemic stroke. According to the obtained results, it can be concluded that transplantation of mesenchymal stem cells is safe and feasible from the economic and biomedical point of view. For the further implementa-tion of this promising approach into the clinical practice, randomized, placebo-controlled, multicenter clinical trials are needed with a large sample of patients and optimized cell transplantation protocols and patient inclusion criteria. In this review we also discuss possi-ble strategies to enhance the effectiveness of cell therapy with the use of mesenchymal stem cells.

Recent advances in tissue repair of the blood-brain barrier after stroke

The selective permeability of the blood-brain barrier (BBB) enables the necessary exchange of substances between the brain parenchyma and circulating blood and is important for the normal functioning of the central nervous system. Ischemic stroke inflicts damage upon the BBB, triggering adverse stroke outcomes such as cerebral edema, hemorrhagic transformation, and aggravated neuroinflammation. Therefore, effective repair of the damaged BBB after stroke and neovascularization that allows for the unique selective transfer of substances from the BBB after stroke is necessary and important for the recovery of brain function. This review focuses on four important therapies that have effects of BBB tissue repair after stroke in the last seven years. Most of these new therapies show increased expression of BBB tight-junction proteins, and some show beneficial results in terms of enhanced pericyte coverage at the injured vessels. This review also briefly outlines three effective classes of approaches and their mechanisms for promoting neoangiogenesis following a stroke.

Mononuclear cell therapy of neonatal hypoxic-ischemic encephalopathy in preclinical versus clinical studies: a systematic analysis of therapeutic efficacy and study design

Background

Hypoxic-ischemic encephalopathy (HIE) is a devastating condition affecting around 8.5 in 1000 newborns globally. Therapeutic hypothermia (TH) can reduce mortality and, to a limited extent, disability after HIE. Nevertheless, there is a need for new and effective treatment strategies. Cell based treatments using mononuclear cells (MNC), which can be sourced from umbilical cord blood, are currently being investigated. Despite promising preclinical results, there is currently no strong indicator for clinical efficacy of the approach. This analysis aimed to provide potential explanations for this discrepancy.

Methods

A systematic review and meta-analysis was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. Preclinical and clinical studies were retrieved from PubMed, Web of Science, Scopus, and clinicaltrials.gov using a predefined search strategy. A total of 17 preclinical and 7 clinical studies were included. We analyzed overall MNC efficacy in preclinical trials, the methodological quality of preclinical trials and relevant design features in preclinical versus clinical trials.

Results

There was evidence for MNC therapeutic efficacy in preclinical models of HIE. The methodological quality of preclinical studies was not optimal, and statistical design quality was particularly poor. However, methodological quality was above the standard in other fields. There were significant differences in preclinical versus clinical study design including the use of TH as a baseline treatment (only in clinical studies) and much higher MNC doses being applied in preclinical studies.

Conclusions

Based on the analyzed data, it is unlikely that therapeutic effect size is massively overestimated in preclinical studies. It is more plausible that the many design differences between preclinical and clinical trials are responsible for the so far lacking proof of efficacy of MNC treatments in HIE. Additional preclinical and clinical research is required to optimize the application of MNC for experimental HIE treatment.

Comparative study of the efficacy of intra-arterial and intravenous transplantation of human induced pluripotent stem cells-derived neural progenitor cells in experimental stroke

Background

Cell therapy using neural progenitor cells (NPCs) is a promising approach for ischemic stroke treatment according to the results of multiple preclinical studies in animal stroke models. In the vast majority of conducted animal studies, the therapeutic efficacy of NPCs was estimated after intracerebral transplantation, while the information of the effectiveness of systemic administration is limited. Nowadays, several clinical trials aimed to estimate the safety and efficacy of NPCs transplantation in stroke patients were also conducted. In these studies, NPCs were transplanted intracerebrally in the subacute/chronic phase of stroke. The results of clinical trials confirmed the safety of the approach, however, the degree of functional improvement (the primary efficacy endpoint) was not sufficient in the majority of the studies. Therefore, more studies are needed in order to investigate the optimal transplantation parameters, especially the timing of cell transplantation after the stroke onset. This study aimed to evaluate the therapeutic effects of intra-arterial (IA) and intravenous (IV) administration of NPCs derived from induced pluripotent stem cells (iNPCs) in the acute phase of experimental stroke in rats. Induced pluripotent stem cells were chosen as the source of NPCs as this technology is perspective, has no ethical concerns and provides the access to personalized medicine.

Methods

Human iNPCs were transplanted IA or IV into male Wistar rats 24 h after the middle cerebral artery occlusion stroke modeling. Therapeutic efficacy was monitored for 14 days and evaluated in comparison with the cell transplantation-free control group. Additionally, cell distribution in the brain was assessed.

Results

The obtained results show that both routes of systemic transplantation (IV and IA) significantly reduced the mortality and improved the neurological deficit of experimental animals compared to the control group. At the same time, according to the MRI data, only IA administration led to faster and prominent reduction of the stroke volume. After IA administration, iNPCs transiently trapped in the brain and were not detected on day 7 after the transplantation. In case of IV injection, transplanted cells were not visualized in the brain. The obtained data demonstrated that the systemic transplantation of human iNPCs in the acute phase of ischemic stroke can be a promising therapeutic strategy.

Repeat-dose toxicity study of human umbilical cord mesenchymal stem cells in cynomolgus monkeys by intravenous and subcutaneous injection

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are proposed for the treatment of acute lung injury and atopic dermatitis. To advance hUC-MSC entry into clinical trials, the effects of hUC-MSCs on the general toxicity, immune perturbation and toxicokinetic study of hUC-MSCs in cynomolgus monkeys were assessed. hUC-MSCs were administered to cynomolgus monkeys by intravenous infusion of 3.0 × 106 or 3.0 × 107cells/kg or by subcutaneous injection of 3.0 × 107cells/kg twice a week for 3 weeks followed by withdrawal and observation for 6 weeks. Toxicity was assessed by clinical observation, clinical pathology, ophthalmology, immunotoxicology and histopathology. Moreover, toxicokinetic study was performed using a validated qPCR method after the first and last dose. After 3rd or 4th dosing, one or three the monkeys in the intravenous high-dose group exhibited transient coma, which was eliminated by slow-speed infusion after 5th or 6th dosing. In all dose groups, hUC-MSCs significantly increased NEUT levels and decreased LYMPH and CD3+ levels, which are related to the immunosuppressive effect of hUC-MSCs. Subcutaneous nodules and granulomatous foci were found at the site of administration in all monkeys in the subcutaneous injection group. Other than above abnormalities, no obvious systemic toxicity was observed in any group. The hUC-MSCs was detectable in blood only within 1 h after intravenous and subcutaneous administration. The present study declared the preliminary safety of hUC-MSCs, but close monitoring of hUC-MSCs for adverse effects, such as coma induced by intravenous infusion, is warranted in future clinical trials.

Systemic administration of clinical-grade multilineage-differentiating stress-enduring cells ameliorates hypoxic-ischemic brain injury in neonatal rats

Multilineage-differentiating stress-enduring (Muse) cells are endogenous reparative pluripotent stem cells present in the bone marrow, peripheral blood, and organ connective tissues. We assessed the homing and therapeutic effects of systemically administered nafimestrocel, a clinical-grade human Muse cell-based product, without immunosuppressants in a neonatal hypoxic-ischemic (HI) rat model. HI injury was induced on postnatal day 7 (P7) and was confirmed by T2-weighted magnetic resonance imaging on P10. HI rats received a single dose nafimestrocel (1 × 106 cells/body) or Hank's balanced salt solution (vehicle group) intravenously at either three days (on P10; M3 group) or seven days (on P14; M7 group) after HI insult. Radioisotope experiment demonstrated the homing of chromium-51-labeled nafimestrocel to the both cerebral hemispheres. The cylinder test (M3 and M7 groups) and open-field test (M7 group) showed significant amelioration of paralysis and hyperactivity at five weeks of age compared with those in the vehicle group. Nafimestrocel did not cause adverse events such as death or pathological changes in the lung at ten weeks in the both groups. Nafimestrocel attenuated the production of tumor necrosis factor-α and inducible nitric oxide synthase from activated cultured microglia in vitro. These results demonstrate the potential therapeutic benefits and safety of nafimestrocel.

Therapeutic Efficacy and Migration of Mesenchymal Stem Cells after Intracerebral Transplantation in Rats with Experimental Ischemic Stroke

We studied therapeutic efficacy and migration characteristics of mesenchymal stem cells isolated from the human placenta after their intracerebral (stereotactic) administration to rats with the experimental ischemic stroke. It was shown that cell therapy significantly improved animal survival rate and reduced the severity of neurological deficit. New data on the migration pathways of transplanted cells in the brain were obtained.

Mn-Based Methacrylated Gellan Gum Hydrogels for MRI-Guided Cell Delivery and Imaging

This work aims to engineer a new stable injectable Mn-based methacrylated gellan gum (Mn/GG-MA) hydrogel for real-time monitored cell delivery into the central nervous system. To enable the hydrogel visualization under Magnetic Resonance Imaging (MRI), GG-MA solutions were supplemented with paramagnetic Mn2+ ions before its ionic crosslink with artificial cerebrospinal fluid (aCSF). The resulting formulations were stable, detectable by T1-weighted MRI scans and also injectable. Cell-laden hydrogels were prepared using the Mn/GG-MA formulations, extruded into aCSF for crosslink, and after 7 days of culture, the encapsulated human adipose-derived stem cells remained viable, as assessed by Live/Dead assay. In vivo tests, using double mutant MBPshi/shi/rag2 immunocompromised mice, showed that the injection of Mn/GG-MA solutions resulted in a continuous and traceable hydrogel, visible on MRI scans. Summing up, the developed formulations are suitable for both non-invasive cell delivery techniques and image-guided neurointerventions, paving the way for new therapeutic procedures.

A Simplified and Effective Approach for the Isolation of Small Pluripotent Stem Cells Derived from Human Peripheral Blood

Pluripotent stem cells are key players in regenerative medicine. Embryonic pluripotent stem cells, despite their significant advantages, are associated with limitations such as their inadequate availability and the ethical dilemmas in their isolation and clinical use. The discovery of very small embryonic-like (VSEL) stem cells addressed the aforementioned limitations, but their isolation technique remains a challenge due to their small cell size and their efficiency in isolation. Here, we report a simplified and effective approach for the isolation of small pluripotent stem cells derived from human peripheral blood. Our approach results in a high yield of small blood stem cell (SBSC) population, which expresses pluripotent embryonic markers (e.g., Nanog, SSEA-3) and the Yamanaka factors. Further, a fraction of SBSCs also co-express hematopoietic markers (e.g., CD45 and CD90) and/or mesenchymal markers (e.g., CD29, CD105 and PTH1R), suggesting a mixed stem cell population. Finally, quantitative proteomic profiling reveals that SBSCs contain various stem cell markers (CD9, ITGA6, MAPK1, MTHFD1, STAT3, HSPB1, HSPA4), and Transcription reg complex factors (e.g., STAT5B, PDLIM1, ANXA2, ATF6, CAMK1). In conclusion, we present a novel, simplified and effective isolating process that yields an abundant population of small-sized cells with characteristics of pluripotency from human peripheral blood.

Comparative study of extracellular vesicles derived from mesenchymal stem cells and brain endothelial cells attenuating blood-brain barrier permeability via regulating Caveolin-1-dependent ZO-1 and Claudin-5 endocytosis in acute ischemic stroke

BACKGROUND

Blood-brain barrier (BBB) disruption is a major adverse event after ischemic stroke (IS). Caveolin-1 (Cav-1), a scaffolding protein, played multiple roles in BBB permeability after IS, while the pros and cons of Cav-1 on BBB permeability remain controversial. Numerous studies revealed that extracellular vesicles (EVs), especially stem cells derived EVs, exerted therapeutic efficacy on IS; however, the mechanisms of BBB permeability needed to be clearly illustrated. Herein, we compared the protective efficacy on BBB integrity between bone marrow mesenchymal stem cells derived extracellular vesicles (BMSC-EVs) and EVs from brain endothelial cells (BEC-EVs) after acute IS and investigated whether the mechanism was associated with EVs antagonizing Cav-1-dependent tight junction proteins endocytosis.

METHODS

BMSC-EVs and BEC-EVs were isolated and characterized by nanoparticle tracking analysis, western blotting, and transmission electron microscope. Oxygen and glucose deprivation (OGD) treated b. End3 cells were utilized to evaluate brain endothelial cell leakage. CCK-8 and TRITC-dextran leakage assays were used to measure cell viability and transwell monolayer permeability. Permanent middle cerebral artery occlusion (pMCAo) model was established, and EVs were intravenously administered in rats. Animal neurological function tests were applied, and microvessels were isolated from the ischemic cortex. BBB leakage and tight junction proteins were analyzed by Evans Blue (EB) staining and western blotting, respectively. Co-IP assay and Cav-1 siRNA/pcDNA 3.1 vector transfection were employed to verify the endocytosis efficacy of Cav-1 on tight junction proteins.

RESULTS

Both kinds of EVs exerted similar efficacies in reducing the cerebral infarction volume and BBB leakage and enhancing the expressions of ZO-1 and Claudin-5 after 24 h pMCAo in rats. At the same time, BMSC-EVs were outstanding in ameliorating neurological function. Simultaneously, both EVs treatments suppressed the highly expressed Cav-1 in OGD-exposed b. End3 cells and ischemic cerebral microvessels, and this efficacy was more prominent after BMSC-EVs administration. Cav-1 knockdown reduced OGD-treated b. End3 cells monolayer permeability and recovered ZO-1 and Claudin-5 expressions, whereas Cav-1 overexpression aggravated permeability and enhanced the colocalization of Cav-1 with ZO-1 and Claudin-5. Furthermore, Cav-1 overexpression partly reversed the lower cell leakage by BMSC-EVs and BEC-EVs administrations in OGD-treated b. End3 cells.

CONCLUSIONS

Our results demonstrated that Cav-1 aggravated BBB permeability in acute ischemic stroke, and BMSC-EVs exerted similar antagonistic efficacy to BEC-EVs on Cav-1-dependent ZO-1 and Claudin-5 endocytosis. BMSC-EVs treatment was superior in Cav-1 suppression and neurological function amelioration.

Dynamic MRI of the Mesenchymal Stem Cells Distribution during Intravenous Transplantation in a Rat Model of Ischemic Stroke

Systemic transplantation of mesenchymal stem cells (MSCs) is a promising approach for the treatment of ischemia-associated disorders, including stroke. However, exact mechanisms underlying its beneficial effects are still debated. In this respect, studies of the transplanted cells distribution and homing are indispensable. We proposed an MRI protocol which allowed us to estimate the dynamic distribution of single superparamagnetic iron oxide labeled MSCs in live ischemic rat brain during intravenous transplantation after the transient middle cerebral artery occlusion. Additionally, we evaluated therapeutic efficacy of cell therapy in this rat stroke model. According to the dynamic MRI data, limited numbers of MSCs accumulated diffusely in the brain vessels starting at the 7th minute from the onset of infusion, reached its maximum by 29 min, and gradually eliminated from cerebral circulation during 24 h. Despite low numbers of cells entering brain blood flow and their short-term engraftment, MSCs transplantation induced long lasting improvement of the neurological deficit, but without acceleration of the stroke volume reduction compared to the control animals during 14 post-transplantation days. Taken together, these findings indicate that MSCs convey their positive action by triggering certain paracrine mechanisms or cell-cell interactions or invoking direct long-lasting effects on brain vessels.

Thrombus Inhibition and Neuroprotection for Ischemic Stroke Treatment through Platelet Regulation and ROS Scavenging

Ischemic stroke is caused by cerebrovascular stenosis or occlusion. Excessive reactive oxygen species (ROS) are the focus-triggering factor of irreversible injury in ischemic regions, which result in harmful cascading effects to brain tissue, such as inflammation and microthrombus formation. In the present work, we designed nanodelivery systems (NDSs) based on MnO₂ loaded with Ginkgolide B (GB) for restoring the intracerebral microenvironment in ischemic stroke, such as ROS scavenging, O₂ elevation, thrombus inhibition and damage repair. GB can activate the endogenous antioxidant defense of cells by enhancing the nuclear factor-E2-related factor 2 (Nrf2) signalling pathway, thus protecting brain tissue from oxidative damage. However, the blood-brain barrier (BBB) is also a therapeutic obstacle for the delivery of these agents to ischemic regions. MnO₂ nanoparticles have an inherent BBB penetration effect, which enhances the delivery of therapeutic agents within brain tissue. MnO₂ , with mimicking enzymatic activity, can catalyze the decomposition of overproduced H₂ O₂ in the ischemic microenvironment to O₂ , meanwhile releasing platelet-antagonizing GB molecules, thus alleviating cerebral hypoxia, oxidative stress damage, and microthrombus generation. This study may provide a promising therapeutic route for regulating the microenvironment of ischemic stroke through a combined function of ROS scavenging, microthrombus inhibition, and BBB penetration.

Editing a gateway for cell therapy across the blood-brain barrier

Stem cell therapy has been shown to improve stroke outcomes in animal models and is currently advancing towards clinical practice. However, uncertainty remains regarding the optimal route for cell delivery to the injured brain. Local intracerebral injections are effective in precisely delivering cells into the stroke cavity but carry the risk of damaging adjacent healthy tissue. Systemic endovascular injections, meanwhile, are minimally invasive, but most injected cells do not cross CNS barriers and become mechanically trapped in peripheral organs. Although the blood-brain barrier and the blood-CSF barrier tightly limit the entrance of cells and molecules into the brain parenchyma, immune cells can cross these barriers especially under pathological conditions, such as stroke. Deciphering the cell surface signature and the molecular mechanisms underlying this pathophysiological process holds promise for improving the targeted delivery of systemic injected cells to the injured brain. In this review, we describe experimental approaches that have already been developed in which (i) cells are either engineered to express cell surface proteins mimicking infiltrating immune cells; or (ii) cell grafts are preconditioned with hypoxia or incubated with pharmacological agents or cytokines. Modified cell grafts can be complemented with strategies to temporarily increase the permeability of the blood-brain barrier. Although these approaches could significantly enhance homing of stem cells into the injured brain, cell entrapment in off-target organs remains a non-negligible risk. Recent developments in safety-switch systems, which enable the precise elimination of transplanted cells on the administration of a drug, represent a promising strategy for selectively removing stem cells stuck in untargeted organs. In sum, the techniques described in this review hold great potential to substantially improve efficacy and safety of future cell therapies in stroke and may be relevant to other brain diseases.

Mesenchymal stem cell aggregation mediated by integrin α4/VCAM-1 after intrathecal transplantation in MCAO rats

Background

Mesenchymal stem cells (MSCs) have shown immense therapeutic potential for various brain diseases. Intrathecal administration of MSCs may enhance their recruitment to lesions in the central nervous system, but any impact on cerebrospinal fluid (CSF) flow remains unclear.

Methods

Rats with or without middle cerebral artery occlusion (MCAO) received intrathecal injections of 2D cultured MSCs, 3D cultured MSCs or an equal volume of artificial cerebrospinal fluid (ACSF). Ventricle volume was assessed by MRI on Days 2 and 14 post-MCAO surgery. A beam walking test was used to assess fine motor coordination and balance. Aggregation of MSCs was evaluated in CSF and frozen brain tissue. Differential expression of cell adhesion molecules was evaluated by RNA-Seq, flow cytometry and immunofluorescence analyses. The influence of VCAM-1 blockade in mediating the aggregation of 2D MSCs was investigated in vitro by counting cells that passed through a strainer and in vivo by evaluating ventricular dilation.

Results

MSC expanded in 2D culture formed aggregates in the CSF and caused ventricular enlargement in both MCAO and normal rats. Aggregates were associated with impaired motor function. 2D MSCs expressed higher levels of integrin α4 and VCAM-1 than 3D MSCs. Blockade of VCAM-1 in 2D MSCs reduced their aggregation in vitro and reduced lateral ventricular enlargement after intrathecal infusion. 3D MSCs exhibited lower cell aggregation and reduced cerebral ventricular dilation after intrathecal transplantation

Conclusions

The aggregation of 2D MSCs, mediated by the interaction of integrin α4 and VCAM-1, is a potential risk for obstruction of CSF flow after intrathecal transplantation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03189-0.

Potential effects of commonly applied drugs on neural stem cell proliferation and viability: A hypothesis-generating systematic review and meta-analysis

Neural stem cell (NSC) transplantation is an emerging and promising approach to combat neurodegenerative diseases. While NSCs can differentiate into neural cell types, many therapeutic effects are mediated by paracrine, "drug-like" mechanisms. Neurodegenerative diseases are predominantly a burden of the elderly who commonly suffer from comorbidities and thus are subject to pharmacotherapies. There is substantial knowledge about drug-drug interactions but almost nothing is known about a potential impact of pharmacotherapy on NSCs. Such knowledge is decisive for designing tailored treatment programs for individual patients. Previous studies revealed preliminary evidence that the anti-depressants fluoxetine and imipramine may affect NSC viability and proliferation. Here, we derive a hypothesis on how commonly applied drugs, statins and antihypertensives, may affect NSC viability, proliferation, and differentiation. We conducted a systematic review and meta-analysis looking at potential effects of commonly prescribed antihypertensive and antihyperlipidemic medication on NSC function. PubMed and Web of Science databases were searched on according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Publications were assessed against a priori established selection criteria for relevancy. A meta-analysis was then performed on data extracted from publications eligible for full text review to estimate drug effects on NSC functions. Our systematic review identified 1,017 potential studies, 55 of which were eligible for full text review. Out of those, 21 were included in the qualitative synthesis. The meta-analysis was performed on 13 publications; the remainder were excluded as they met exclusion criteria or lacked sufficient data to perform a meta-analysis. The meta-analysis revealed that alpha-2 adrenoceptor agonists, an anti-hypertensive drug class [p < 0.05, 95% confidence intervals (CI) = -1.54; -0.35], and various statins [p < 0.05, 95% CI = -3.17; -0.0694] had an inhibiting effect on NSC proliferation. Moreover, we present preliminary evidence that L-type calcium channel blockers and statins, particularly lovastatin, may reduce NSC viability. Although the data available in the literature is limited, there are clear indications for an impact of commonly applied drugs, in particular statins, on NSC function. Considering the modes of action of the respective drugs, we reveal plausible mechanisms by which this impact may be mediated, creating a testable hypothesis, and providing insights into how future confirmative research on this topic may be conducted.

Targeted delivery of nanomedicines for promoting vascular regeneration in ischemic diseases

Ischemic diseases, the leading cause of disability and death, are caused by the restriction or blockage of blood flow in specific tissues, including ischemic cardiac, ischemic cerebrovascular and ischemic peripheral vascular diseases. The regeneration of functional vasculature network in ischemic tissues is essential for treatment of ischemic diseases. Direct delivery of pro-angiogenesis factors, such as VEGF, has demonstrated the effectiveness in ischemic disease therapy but suffering from several obstacles, such as low delivery efficacy in disease sites and uncontrolled modulation. In this review, we summarize the molecular mechanisms of inducing vascular regeneration, providing the guidance for designing the desired nanomedicines. We also introduce the delivery of various nanomedicines to ischemic tissues by passive or active targeting manner. To achieve the efficient delivery of nanomedicines in various ischemic diseases, we highlight targeted delivery of nanomedicines and controllable modulation of disease microenvironment using nanomedicines.

Exosomes in craniofacial tissue reconstruction

BACKGROUND

Mesenchymal stem cell (MSC) therapy gained interest among scientists following the discovery of its therapeutic potential. However, their clinical use has been hindered due to their immunogenicity and tumorigenicity. Relatively recently, it has been unveiled that the mechanism by which MSC promote healing is by secreting exosomes. This raised the interest in developing cell-free therapy, avoiding the obstacles that deterred the translation of MSC therapy into clinical practice.

REVIEW

This comprehensive narrative review summarises the current understanding of exosome biogenesis and content. Moreover, the existing research on exosome use in bone tissue engineering is discussed.

CONCLUSIONS

Exosome-based therapy may provide excellent potential in the field of bone tissue engineering and craniofacial reconstructive surgery. Further investigation is required before the technology can be translated into clinical practice.

Human Multipotent Mesenchymal Stromal Cell–Derived Extracellular Vesicles Enhance Neuroregeneration in a Rat Model of Sciatic Nerve Crush Injury

Peripheral nerve injury remains a serious problem for medicine, with no effective method of treatment at the moment. The most prominent example of this problem is neonatal brachial plexus palsy, which results from the stretching of the brachial plexus nerves in the birth or perinatal period. Multipotent mesenchymal cells (MSCs) and the extracellular vesicles (EVs) they produce are known to have a marked neuroprotective effect in central nervous system injuries. We suggested that the use of MSCs-derived EVs may be an effective approach to the regeneration of peripheral nerves after injury. Sciatic nerve injury was modeled in rats via crushing, and then a gel containing MSCs–EVs was applied to the injured area. After 15 and 30 days, a histological, physiological, and functional assessment of nerve, dorsal root ganglia (DRG), and innervated muscles’ recovery was performed. Transplantation of EVs to the area of sciatic nerve injury significantly reduced muscle atrophy as compared to the control group. Functional recovery of the innervated muscles, as measured by the extensor postural thrust test, was revealed 30 days after the surgery. We associate the obtained results with EVs-induced neuroprotective mechanisms, which were expressed in a decrease in apoptotic neuronal death and an increase in regeneration-associated proteins NF-200 and GAP-43, as well as in DRG and damaged nerve. We suggest that the therapeutic scheme we used is efficient for the treatment of acute peripheral nervous system injuries and can be transferred to the clinics. However, additional studies are required for a more detailed analysis of neuroprotection mechanisms.

Genetically engineered and enucleated human mesenchymal stromal cells for the targeted delivery of therapeutics to diseased tissue

Targeting the delivery of therapeutics specifically to diseased tissue enhances their efficacy and decreases their side effects. Here we show that mesenchymal stromal cells with their nuclei removed by density-gradient centrifugation following the genetic modification of the cells for their display of chemoattractant receptors and endothelial-cell-binding molecules are effective vehicles for the targeted delivery of therapeutics. The enucleated cells neither proliferate nor permanently engraft in the host, yet retain the organelles for energy and protein production, undergo integrin-regulated adhesion to inflamed endothelial cells, and actively home to chemokine gradients established by diseased tissues. In mouse models of acute inflammation and of pancreatitis, systemically administered enucleated cells expressing two types of chemokine receptor and an endothelial adhesion molecule enhanced the delivery of an anti-inflammatory cytokine to diseased tissue (with respect to unmodified stromal cells and to exosomes derived from bone-marrow-derived stromal cells), attenuating inflammation and ameliorating disease pathology. Enucleated cells retain most of the cells' functionality, yet acquire the cargo-carrying characteristics of cell-free delivery systems, and hence represent a versatile delivery vehicle and therapeutic system.

Reproductive and Developmental Toxicity Assessment of Human Umbilical Cord Mesenchymal Stem Cells in Rats

Objective: Human umbilical cord mesenchymal stem cells (hUC-MSCs) have shown very attractive potential in clinical applications for the treatment of various diseases. However, the data about the reproductive and developmental toxicity of hUC-MSCs remains insufficient. Thus, we assessed the potential effects of intravenous injection of hUC-MSCs on reproduction and development in Sprague-Dawley rats. Methods: In the fertility and early embryonic development study, hUC-MSCs were administered at dose levels of 0, 6.0 × 106, 8.5 × 106, and 1.2 × 107/kg to male and female rats during the pre-mating, mating and gestation period. In the embryo-fetal development study, the pregnant female rats received 0, 6.0 × 106, 1.2 × 107, and 2.4 × 107/kg of hUC-MSCs from gestation days (GD) 6-15. Assessments made included mortality, clinical observations, body weight, food consumption, fertility parameters of male and female, litter, and fetus parameters, etc. Results: No hUC-MSCs-related toxicity was observed on the fertility of male and female rats, and no teratogenic effect on fetuses. hUC-MSCs at 1.2 × 107/kg caused a mildly decrease in body weight gain of male rats, transient listlessness, tachypnea, and hematuria symptoms in pregnant female rats. Death was observed in part of the pregnant females at a dose of 2.4 × 107/kg, which could be due to pulmonary embolism. Conclusion: Based on the results of the studies, the no-observed-adverse-effect levels (NOAELs) are 8.5 × 106/kg for fertility and early embryonic development, 1.2 × 107/kg for maternal toxicity and 2.4 × 107/kg for embryo-fetal development in rats intravenous injected with hUC-MSCs, which are equivalent to 8.5-fold, 12-fold, and 24-fold respectively of its clinical dosage in humans. These findings may provide a rational basis for human health risk assessment of hUC-MSCs.

Stem Cell Homing in Intrathecal Applications and Inspirations for Improvement Paths

A transplanted stem cell homing is a directed migration from the application site to the targeted tissue. Intrathecal application of stem cells is their direct delivery to cerebrospinal fluid, which defines the homing path from the point of injection to the brain. In the case of neurodegenerative diseases, this application method has the advantage of no blood–brain barrier restriction. However, the homing efficiency still needs improvement and homing mechanisms elucidation. Analysis of current research results on homing mechanisms in the light of intrathecal administration revealed a discrepancy between in vivo and in vitro results and a gap between preclinical and clinical research. Combining the existing research with novel insights from cutting-edge biochips, nano, and other technologies and computational models may bridge this gap faster.

Hyperacute transplantation of umbilical cord mesenchymal stromal cells in a model of severe intracerebral hemorrhage

Aim:

Intracerebral hemorrhage (ICH) has limited therapeutic options. We have shown that an intravenous injection of human umbilical cord-derived mesenchymal stromal cells (hUC-MSC) 24 h after an ICH in rats reduced the residual hematoma volume after a moderate hemorrhage but was inefficient in severe ICH. Here, we investigated whether a treatment in the hyperacute phase would be more effective in severe ICH.

Materials & methods:

Wistar rats were randomly selected to receive an intravenous injection of hUC-MSC or the vehicle 1 h after a severe ICH.

Results:

The hyperacute treatment with hUC-MSC did not affect the 22-day survival rate, the motor function or the residual hematoma volume.

Conclusion:

These results indicate the need for optimization of hUC-MSC-based therapies for severe ICH.

Hemorrhagic stroke, caused by the leakage of blood from blood vessels to the brain, is a life-threatening condition that reduces the quality of life of a large number of patients worldwide without effective treatments. Here, we induced a severe hemorrhagic stroke in rats to study the effects of a treatment using mesenchymal stromal cells, stem cells obtained from the umbilical cord tissue capable of producing protective molecules for the brain. The treatment; however, did not improve some aspects of the disease, such as the motor ability and the size of the brain lesion, indicating that further studies are still necessary.

MSCs in Space: Mesenchymal Stromal Cell Therapeutics as Enabling Technology for Long-Distance Manned Space Travel

Purpose of Review

Advancements in space travel, such as space tourism into Earth’s orbit, but also the prospect of long-distance manned space travel to other celestial bodies such as Mars, has generated a clinical need for new enabling technologies to support the long-term well-being of humans during their passage. Here, we will give an outline on the clinical need and practical considerations to MSC therapy as enabling technology for long-distance manned space travel.

Recent Findings

Long-distance space travel entails a threat to the health of astronaut crews due to the low gravity environment and exposure to toxic radiation in space. Multi-organ-system degenerative changes, such as decline in musculoskeletal, hematopoietic, immune system function, and in particular risk of genetic mutations and cancer, are major health concerns. Physical training, pharmacological agents, and protective shielding are among the currently available methods to counteract harmful effects. However, a potential lack of adequate shielding, side effects of pharmacological compounds, and limitations to physical training suggest a need for new countermeasures, to protect space travellers to the best extent. Here, the prospect of cell-based therapy, e.g. mesenchymal stromal/stem cells (MSCs), has been subject to intense research, due to their potent regenerative and immunomodulatory properties. Off-the-shelf MSC therapeutics can be easily maintained in space due to the ambient extremely low-temperature environment, and cryorecovery and even culturing of MSCs under microgravity were shown to be feasible.

Summary

Designing new therapy against harmful radiation is urgent need in space travel. Here we will discuss aspects related to clinical MSC administration to optimize their therapeutic benefit. MSC-based therapy may aid in evolving protective countermeasures for space travellers.

OUP accepted manuscript

The number of mesenchymal stromal/stem cell (MSC) therapeutics and types of clinical applications have greatly diversified during the past decade, including rapid growth of poorly regulated “Stem Cell Clinics” offering diverse “Unproven Stem Cell Interventions.” This product diversification necessitates a critical evaluation of the reliance on the 2006 MSC minimal criteria to not only define MSC identity but characterize MSC suitability for intravascular administration. While high-quality MSC therapeutics have been safely administered intravascularly in well-controlled clinical trials, repeated case reports of mild-to-more-severe adverse events have been reported. These are most commonly related to thromboembolic complications upon infusion of highly procoagulant tissue factor (TF/CD142)-expressing MSC products. As TF/CD142 expression varies widely depending on the source and manufacturing process of the MSC product, additional clinical cell product characterization and guidelines are needed to ensure the safe use of MSC products. To minimize risk to patients receiving MSC therapy, we here propose to supplement the minimal criteria used for characterization of MSCs, to include criteria that assess the suitability of MSC products for intravascular use. If cell products are intended for intravascular delivery, which is true for half of all clinical applications involving MSCs, the effects of MSC on coagulation and hemocompatibility should be assessed and expression of TF/CD142 should be included as a phenotypic safety marker. This adjunct criterion will ensure both the identity of the MSCs as well as the safety of the MSCs has been vetted prior to intravascular delivery of MSC products.

Cell Therapy of Stroke: Do the Intra-Arterially Transplanted Mesenchymal Stem Cells Cross the Blood-Brain Barrier?

Animal model studies and first clinical trials have demonstrated the safety and efficacy of the mesenchymal stem cells' (MSCs) transplantation in stroke. Intra-arterial (IA) administration looks especially promising, since it provides targeted cell delivery to the ischemic brain, is highly effective, and can be safe as long as the infusion is conducted appropriately. However, wider clinical application of the IA MSCs transplantation will only be possible after a better understanding of the mechanism of their therapeutic action is achieved. On the way to achieve this goal, the study of transplanted cells' fate and their interactions with the blood-brain barrier (BBB) structures could be one of the key factors. In this review, we analyze the available data concerning one of the most important aspects of the transplanted MSCs' action-the ability of cells to cross the blood-brain barrier (BBB) in vitro and in vivo after IA administration into animals with experimental stroke. The collected data show that some of the transplanted MSCs temporarily attach to the walls of the cerebral vessels and then return to the bloodstream or penetrate the BBB and either undergo homing in the perivascular space or penetrate deeper into the parenchyma. Transmigration across the BBB is not necessary for the induction of therapeutic effects, which can be incited through a paracrine mechanism even by cells located inside the blood vessels.

Secretome of endothelial progenitor cells from stroke patients promotes endothelial barrier tightness and protects against hypoxia-induced vascular leakage

BACKGROUND

Cell-based therapeutic strategies have been proposed as an alternative for brain repair after stroke, but their clinical application has been hampered by potential adverse effects in the long term. The present study was designed to test the effect of the secretome of endothelial progenitor cells (EPCs) from stroke patients (scCM) on in vitro human models of angiogenesis and vascular barrier.

METHODS

Two different scCM batches were analysed by mass spectrometry and a proteome profiler. Human primary CD34+-derived endothelial cells (CD34+-ECs) were used for designing angiogenesis studies (proliferation, migration, and tubulogenesis) or in vitro models of EC monolayer (confluent monolayer ECs-CMECs) and blood-brain barrier (BBB; brain-like ECs-BLECs). Cells were treated with scCM (5 μg/mL) or protein-free endothelial basal medium (scEBM-control). CMECs or BLECs were exposed (6 h) to oxygen-glucose deprivation (OGD) conditions (1% oxygen and glucose-free medium) or normoxia (control-5% oxygen, 1 g/L of glucose) and treated with scCM or scEBM during reoxygenation (24 h).

RESULTS

The analysis of different scCM batches showed a good reproducibility in terms of protein yield and composition. scCM increased CD34+-EC proliferation, tubulogenesis, and migration compared to the control (scEBM). The proteomic analysis of scCM revealed the presence of growth factors and molecules modulating cell metabolism and inflammatory pathways. Further, scCM decreased the permeability of CMECs and upregulated the expression of the junctional proteins such as occludin, VE-cadherin, and ZO-1. Such effects were possibly mediated through the activation of the interferon pathway and a moderate downregulation of Wnt signalling. Furthermore, OGD increased the permeability of both CMECs and BLECs, while scCM prevented the OGD-induced vascular leakage in both models. These effects were possibly mediated through the upregulation of junctional proteins and the regulation of MAPK/VEGFR2 activity.

CONCLUSION

Our results suggest that scCM promotes angiogenesis and the maturation of newly formed vessels while restoring the BBB function in ischemic conditions. In conclusion, our results highlight the possibility of using EPC-secretome as a therapeutic alternative to promote brain angiogenesis and protect from ischemia-induced vascular leakage.

Exosomes in the Tumor Microenvironment: From Biology to Clinical Applications

Cancer is one of the most important health problems and the second leading cause of death worldwide. Despite the advances in oncology, cancer heterogeneity remains challenging to therapeutics. This is because the exosome-mediated crosstalk between cancer and non-cancer cells within the tumor microenvironment (TME) contributes to the acquisition of all hallmarks of cancer and leads to the formation of cancer stem cells (CSCs), which exhibit resistance to a range of anticancer drugs. Thus, this review aims to summarize the role of TME-derived exosomes in cancer biology and explore the clinical potential of mesenchymal stem-cell-derived exosomes as a cancer treatment, discussing future prospects of cell-free therapy for cancer treatment and challenges to be overcome.

The Need for New Biomarkers to Assist with Stroke Prevention and Prediction of Post-Stroke Therapy Based on Plasma-Derived Extracellular Vesicles

The risk of having a stroke event doubles each decade after the age of 55. Therefore, it is of great interest to develop neurorestorative therapies of stroke which occurs mostly in elderly people. However, to date, patients at risk for these sequels of stroke are not duly diagnosed and treated due to the lack of reliable biomarkers. Extracellular vesicles (EVs) are lipid bilayer-delimited particles that are shed by the brain cells and are able to cross the blood–brain barrier and enter the blood stream; thus, they may be used to interrogate molecular and cellular events in the brain damaged area. In this review, we summarize the major molecular and cellular responses of astroglia and neurons to cerebral ischemia and assess their impact on post-stroke recovery and rehabilitation. In particular, we ask if EVs secreted by brain cells are responses to cerebral ischemia, and they may shed new light on the interplay between exosomes-mediated interactions between brain cells and the question of how to exploit it in order to predict the individual course of the disease and to introduce specific preventive or therapeutic strategies. Given these findings, we are left with two options: either to (i) transplant neuronal precursors into the damaged cortical area or (ii) to covert abundantly present proliferating astrocytes in the perilesional area into neurons by using recently developed genetic technologies. However, given the complexity of molecular and cellular responses to cerebral ischemia and our limited capabilities to restore brain structure and function, we are left with only one realistic aim: to invest more in prevention.

A Bibliometric Analysis of Exosomes in Cardiovascular Diseases From 2001 to 2021

Background: Exosomes in cardiovascular diseases (CVDs) have become an active research field with substantial value and potential. Nevertheless, there are few bibliometric studies in this field. We aimed to visualize the research hotspots and trends of exosomes in CVDs using a bibliometric analysis to help understand the future development of basic and clinical research.

Methods: The articles and reviews regarding exosomes in the CVDs were culled from the Web of Science Core Collection, and knowledge maps were generated using CiteSpace and VOSviewer software.

Results: A total of 1,039 articles were included. The number of exosome articles in the CVDs increased yearly. These publications came from 60 countries/regions, led by the US and China. The primary research institutions were Shanghai Jiao Tong University and Nanjing Medical University. Circulation Research was the journal and co-cited journal with the most studies. We identified 473 authors among which Lucio Barile had the most significant number of articles and Thery C was co-cited most often. After analysis, the most common keywords are myocardium infarction, microRNA and mesenchymal stem cells. Ischemic heart disease, pathogenesis, regeneration, stem cells, targeted therapy, biomarkers, cardiac protection, and others are current and developing areas of study.

Conclusion: We identified the research hotspots and trends of exosomes in CVDs using bibliometric and visual methods. Research on exosomes is flourishing in the cardiovascular medicine. Regenerative medicine, exosome engineering, delivery vehicles, and biomarkers will likely become the focus of future research.

Enhancement of angiogenesis and neurogenesis by intracerebroventricular injection of secretome from human embryonic stem cell-derived mesenchymal stem cells in ischemic stroke model

It is well accepted that the success of mesenchymal stem cells (MSCs) therapy against experimental stroke is mainly due to cellular paracrine manners rather than to replace lost tissue per se. Given such "bystander" effects, cell-free therapeutics manifest as a promising approach in regenerative medicine. Here we aimed at evaluating the effect of conditioned medium (CM) derived from human embryonic MSCs (hESC-MSC) on the neurological deficit, neurogenesis, and angiogenesis in experimental stroke. Adult male Wistar rats subjected to middle cerebral artery occlusion (MCAO), were treated with intracerebroventricular CM either one time (1 h post MCAO) or three times (1, 24, and 48 h post MCAO). Motor performance was assessed by the cylinder test on days 3 and 7. Cerebral samples were obtained for infarct size and molecular analysis on day 7 post-injury. Neurogenesis was evaluated by probing Nestin, Ki67, DCX, and Reelin transcripts and protein levels in the striatum, cortex, subventricular zone, and corpus callosum. The mRNA and protein expression of CD31 were also assessed in the striatum and cortical region to estimate angiogenesis post MCAO. Our findings demonstrate that CM treatment could significantly ameliorate neurological deficits and infarct volume in MCAO rats. Furthermore, ischemic stroke was associated with higher levels of neurogenesis and angiogenesis markers. Following treatment with CM, these markers were further potentiated in the brain regions. This study suggests that the therapeutic benefits of CM obtained from hESC-MSCs at least partly are mediated through improved neurogenesis and angiogenesis to accelerate the recovery of cerebral ischemia insult.

Biological, chemical and mechanical factors regulating migration and homing of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a population of primary and non-specialized cells, which can be isolated from various tissues. Currently, MSCs are key players in cellular therapy and regenerative medicine. However, the possibility of using MSCs in the treatment of many diseases needs to be preceded, though, by in-depth analysis of their properties, especially by determining the mechanism of tissue homing as well as the mechanism, due to which cells contribute to tissue regeneration. This review is intended to present information on recent findings regarding the mechanism of recruitment and tissue homing by MSCs and discuss current hypotheses for how MSCs can reach target tissues.

Are We Ready for Cell Therapy to Treat Stroke?

Clinical trials of cell therapies that target stroke started at the beginning of this century and they have experienced a significant boost in recent years as a result of promising data from basic research studies. The increase in the information available has paved the way to carry out more innovative and varied human studies. Efforts have focused on the search for a safe and effective treatment to stimulate neuro-regeneration in the brain and to reduce the sequelae of stroke in patients. Therefore, this review aims to evaluate the clinical trials using cell therapy to treat stroke published to date and assess their limitations. From 2000 to date, most of the published clinical trials have focused on phases I or II, and the vast majority of them demonstrate that stem cells are essentially safe to use when administered by different routes, with transient and mild adverse events that do not generally have severe consequences for health. In general, there is considerable variation in the trials in terms of statistical design, sample size, the cells used, the routes of administration, and the functional assessments (both at baseline and follow-up), making it difficult to compare the studies. From this general description, possibly the experimental protocol is the main element to improve in future studies. Establishing an adequate experimental and statistical design will be essential to obtain favorable and reliable results when conducting phase III clinical trials. Thus, it is necessary to standardize the criteria used in these clinical trials in order to aid comparison. Shortly, cell therapy will be a key approach in the treatment of stroke if adequate and comprehensive levels of recovery are to be achieved.

Extracellular Vesicle Application as a Novel Therapeutic Strategy for Ischemic Stroke

Ischemic stroke (IS) accounts for most of the cases of stroke onset, and due to short therapeutic time window for thrombolysis and numerous limited treatment measures and contraindications, lots of patients cannot receive satisfying therapeutic effects resulting in high disability and mortality worldly. In recent years, extracellular vesicles (EVs), as nanosized membrane-structured vesicles secreted from almost all cells, especially from stem/progenitor cells, have been reported to exert significant beneficial effects on IS from multiple approaches and notably ameliorate neurological outcome. Moreover, based on nano-size and lipid bilayer structure, EVs can easily penetrate the blood-brain barrier and migrate into the brain. In this review, we mainly systematically summarize the therapeutic effects of EVs on IS and explore their potential applications. Simultaneously, we also discuss administration routines, dosages, experimental observation time, and some key issues of EV application during IS treatment. It contributes to a comprehensive understanding of the progress of EV treatment for IS and providing confident evidence for further EV clinical application widely.

Mesenchymal Stem Cells for Neurological Disorders

Neurological disorders are becoming a growing burden as society ages, and there is a compelling need to address this spiraling problem. Stem cell-based regenerative medicine is becoming an increasingly attractive approach to designing therapies for such disorders. The unique characteristics of mesenchymal stem cells (MSCs) make them among the most sought after cell sources. Researchers have extensively studied the modulatory properties of MSCs and their engineering, labeling, and delivery methods to the brain. The first part of this review provides an overview of studies on the application of MSCs to various neurological diseases, including stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, Parkinson's disease, and other less frequently studied clinical entities. In the second part, stem cell delivery to the brain is focused. This fundamental but still understudied problem needs to be overcome to apply stem cells to brain diseases successfully. Here the value of cell engineering is also emphasized to facilitate MSC diapedesis, migration, and homing to brain areas affected by the disease to implement precision medicine paradigms into stem cell-based therapies.

Potential Mechanisms and Perspectives in Ischemic Stroke Treatment Using Stem Cell Therapies

Ischemic stroke (IS) remains one of the major causes of death and disability due to the limited ability of central nervous system cells to regenerate and differentiate. Although several advances have been made in stroke therapies in the last decades, there are only a few approaches available to improve IS outcome. In the acute phase of IS, mechanical thrombectomy and the administration of tissue plasminogen activator have been widely used, while aspirin or clopidogrel represents the main therapy used in the subacute or chronic phase. However, in most cases, stroke patients fail to achieve satisfactory functional recovery under the treatments mentioned above. Recently, cell therapy, especially stem cell therapy, has been considered as a novel and potential therapeutic strategy to improve stroke outcome through mechanisms, including cell differentiation, cell replacement, immunomodulation, neural circuit reconstruction, and protective factor release. Different stem cell types, such as mesenchymal stem cells, marrow mononuclear cells, and neural stem cells, have also been considered for stroke therapy. In recent years, many clinical and preclinical studies on cell therapy have been carried out, and numerous results have shown that cell therapy has bright prospects in the treatment of stroke. However, some cell therapy issues are not yet fully understood, such as its optimal parameters including cell type choice, cell doses, and injection routes; therefore, a closer relationship between basic and clinical research is needed. In this review, the role of cell therapy in stroke treatment and its mechanisms was summarized, as well as the function of different stem cell types in stroke treatment and the clinical trials using stem cell therapy to cure stroke, to reveal future insights on stroke-related cell therapy, and to guide further studies.