Hypoxic Preconditioning Augments the Therapeutic Efficacy of Bone Marrow Stromal Cells in a Rat Ischemic Stroke Model

Bibliometric Analysis and Visualized Study of Research on Mesenchymal Stem Cells in Ischemic Stroke

BACKGROUND

One of the major global causes of death and disability is ischemic stroke (IS). Mesenchymal stem cells (MSCs) emerge as a cell-based therapy for numerous diseases. Recently, research on the role of MSCs in ischemic stroke has developed rapidly worldwide. Bibliometric analysis of MSCs for IS has not yet been published, though.

AIM

Through bibliometric analysis, the aim of this study was to assess the current state of research on MSCs in the field of ischemic stroke research worldwide and to identify important results, major research areas, and emerging trends.

METHODS

Publications related to MSCs in ischemic stroke from January 1, 2002, to December 31, 2022, were obtained from the Web of Science Core Collection (WoSCC). We used HistCite, VOSViewer, CiteSpace, and Bibliometrix for bibliometric analysis and visualization. We employed the Total Global Citation Score (TGCS) to assess the impact of publications.

RESULTS

The bibliometric analysis included a total of 2,048 publications. The 1,386 papers used in this study were authored by 200 individuals across 200 organizations in 72 countries, published in 202 journals. Cesar V Borlongan published the most documents among high-productivity authors. Michael Chopp was the author with the highest average number of citations per paper, with an average paper citation time of 118.54. We found that research of MSCs in ischemic stroke developed rapidly starting in 2008. Neurosciences were the most productive journals, and Chinese researchers have produced the most research papers in this subject. The most cited article is "Systemic administration of exosomes released from mesenchymal stromal cells promotes functional recovery and neurovascular plasticity after stroke in rats".

CONCLUSION

This study uses both numbers and descriptions to thoroughly review the research on MSCs related to IS. This information provides valuable experience for researchers to carry out MSCs' work on IS.

Hypoxic Preconditioning Enhances the Potential of Mesenchymal Stem Cells to Treat Neonatal Hypoxic-Ischemic Brain Injury

BACKGROUND

Neonatal hypoxic-ischemic (HI) brain injury is one of the leading causes of long-term neurological morbidity in newborns. Current treatment options for HI brain injury are limited, but mesenchymal stem cell (MSC) therapy is a promising strategy to boost neuroregeneration after injury. Optimization strategies to further enhance the potential of MSCs are under development. The current study aimed to test the potency of hypoxic preconditioning of MSCs to enhance the therapeutic efficacy in a mouse model of neonatal HI injury.

METHODS

HI was induced on postnatal day 9 in C57Bl/6 mouse pups. MSCs were cultured under hypoxic (hypoxic-preconditioned MSCs [HP-MSCs], 1% O2) or normoxic-control (normoxic-preconditioned MSCs, 21% O2) conditions for 24 hours before use. At 10 days after HI, HP-MSCs, normoxic-preconditioned MSCs, or vehicle were intranasally administered. Gold nanoparticle-labeled MSCs were used to assess MSC migration 24 hours after intranasal administration. At 28 days post-HI, lesion size, sensorimotor outcome, and neuroinflammation were assessed by hematoxylin and eosin staining, cylinder rearing task, and IBA1 staining, respectively. In vitro, the effect of HP-MSCs was studied on transwell migration, neural stem cell differentiation and microglia activation, and the MSC intracellular proteomic content was profiled using quantitative LC-MS/ms.

RESULTS

Intranasally administered HP-MSCs were superior to normoxic-preconditioned MSCs in reducing lesion size and sensorimotor impairments post-HI. Moreover, hypoxic preconditioning enhanced MSC migration in an in vitro set-up, and in vivo to the lesioned hemisphere after intranasal application. In addition, HP-MSCs enhanced neural stem cell differentiation into more complex neurons in vitro but had similar anti-inflammatory effects compared with normoxic-preconditioned MSCs. Lastly, hypoxic preconditioning led to elevated abundances of proteins in MSCs related to extracellular matrix remodeling.

CONCLUSIONS

This study shows for the first time that hypoxic preconditioning enhanced the therapeutic efficacy of MSC therapy in a mouse model of neonatal HI brain injury by increasing the migratory and neuroregenerative capacity of MSCs.

Hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect neurons from cardiac arrest-induced pyroptosis

JOURNAL/nrgr/04.03/01300535-202504000-00027/figure1/v/2024-07-06T104127Z/r/image-tiff Cardiac arrest can lead to severe neurological impairment as a result of inflammation, mitochondrial dysfunction, and post-cardiopulmonary resuscitation neurological damage. Hypoxic preconditioning has been shown to improve migration and survival of bone marrow-derived mesenchymal stem cells and reduce pyroptosis after cardiac arrest, but the specific mechanisms by which hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect against brain injury after cardiac arrest are unknown. To this end, we established an in vitro co-culture model of bone marrow-derived mesenchymal stem cells and oxygen-glucose deprived primary neurons and found that hypoxic preconditioning enhanced the protective effect of bone marrow stromal stem cells against neuronal pyroptosis, possibly through inhibition of the MAPK and nuclear factor κB pathways. Subsequently, we transplanted hypoxia-preconditioned bone marrow-derived mesenchymal stem cells into the lateral ventricle after the return of spontaneous circulation in an 8-minute cardiac arrest rat model induced by asphyxia. The results showed that hypoxia-preconditioned bone marrow-derived mesenchymal stem cells significantly reduced cardiac arrest-induced neuronal pyroptosis, oxidative stress, and mitochondrial damage, whereas knockdown of the liver isoform of phosphofructokinase in bone marrow-derived mesenchymal stem cells inhibited these effects. To conclude, hypoxia-preconditioned bone marrow-derived mesenchymal stem cells offer a promising therapeutic approach for neuronal injury following cardiac arrest, and their beneficial effects are potentially associated with increased expression of the liver isoform of phosphofructokinase following hypoxic preconditioning.

Role of intracranial bone marrow mesenchymal stem cells in stroke recovery: A focus on post-stroke inflammation and mitochondrial transfer

Stem cell therapy has become a hot research topic in the medical field in recent years, with enormous potential for treating a variety of diseases. In particular, bone marrow mesenchymal stem cells (BMSCs) have wide-ranging applications in the treatment of ischemic stroke, autoimmune diseases, tissue repair, and difficult-to-treat diseases. BMSCs can differentiate into multiple cell types and exhibit strong immunomodulatory properties. Although BMSCs can regulate the inflammatory response activated after stroke, the mechanism by which BMSCs regulate inflammation remains unclear and requires further study. Recently, stem cell therapy has emerged as a potentially effective approach for enhancing the recovery process following an ischemic stroke. For example, by regulating post-stroke inflammation and by transferring mitochondria to exert therapeutic effects. Therefore, this article reviews the therapeutic effects of intracranial BMSCs in regulating post-stroke inflammation and mitochondrial transfer in the treatment of stroke, providing a basis for further research.

Preconditioning of MSCs for Acute Neurological Conditions: From Cellular to Functional Impact-A Systematic Review

This systematic review aims to gather evidence on the mechanisms triggered by diverse preconditioning strategies for mesenchymal stem cells (MSCs) and their impact on their potential to treat ischemic and traumatic injuries affecting the nervous system. The 52 studies included in this review report nine different types of preconditioning, namely, manipulation of oxygen pressure, exposure to chemical substances, lesion mediators or inflammatory factors, usage of ultrasound, magnetic fields or biomechanical forces, and culture in scaffolds or 3D cultures. All these preconditioning strategies were reported to interfere with cellular pathways that influence MSCs' survival and migration, alter MSCs' phenotype, and modulate the secretome and proteome of these cells, among others. The effects on MSCs' phenotype and characteristics influenced MSCs' performance in models of injury, namely by increasing the homing and integration of the cells in the lesioned area and inducing the secretion of growth factors and cytokines. The administration of preconditioned MSCs promoted tissue regeneration, reduced neuroinflammation, and increased angiogenesis and myelinization in rodent models of stroke, traumatic brain injury, and spinal cord injury. These effects were also translated into improved cognitive and motor functions, suggesting an increased therapeutic potential of MSCs after preconditioning. Importantly, none of the studies reported adverse effects or less therapeutic potential with these strategies. Overall, we can conclude that all the preconditioning strategies included in this review can stimulate pathways that relate to the therapeutic effects of MSCs. Thus, it would be interesting to explore whether combining different preconditioning strategies can further boost the reparative effects of MSCs, solving some limitations of MSCs' therapy, namely donor-associated variability.

Fisetin alleviates cerebral ischemia/reperfusion injury by regulating Sirt1/Foxc1/Ubqln1 pathway-mediated proteostasis

BACKGROUND

Cerebral ischemia/reperfusion injury (IRI) is pathologically associated with protein damage. The flavonoid fisetin has good therapeutic effects on cerebral IRI. However, the role of fisetin in regulating protein damage during cerebral IRI development remains unclear. This study investigated the pharmacological effects of fisetin on protein damage during cerebral IRI progression and defined the underlying mechanism of action.

METHODS

In vivo and in vitro models of cerebral IRI were established by middle cerebral artery occlusion/reperfusion (MACO/R) and oxygen-glucose deprivation/reperfusion (OGD/R) treatment, respectively. Triphenyl tetrazolium chloride staining was performed to detect cerebral infarct size, and the modified neurologic severity score was used to examine neurological deficits. LDH activity and protein damage were assessed using kits. HT22 cell vitality and apoptosis were examined using CCK-8 assay and TUNEL staining, respectively. Interactions between Foxc1, Ubqln1, Sirt1, and Ezh2 were analyzed using CoIP, ChIP and/or dual-luciferase reporter gene assays.

RESULTS

Fisetin alleviated protein damage and ubiquitinated protein aggregation and neuronal death caused by MCAO/R and OGD/R. Ubqln1 knockdown abrogated the inhibitory effect of fisetin on OGD/R-induced protein damage, ubiquitinated protein aggregation, and neuronal death in HT22 cells. Further experiments demonstrated that Foxc1 functions as a transcriptional activator of Ubqln1 and that Sirt1 promotes Foxc1 expression by deacetylating Ezh2 and inhibiting its activity. Furthermore, Sirt1 knockdown abrogated fisetin-mediated biological effects on OGD/R-treated HT22 cells.

CONCLUSION

Fisetin improved proteostasis during cerebral IRI by regulating the Sirt1/Foxc1/Ubqln1 signaling axis. Our findings strongly suggest that fisetin-mediated inhibition of protein damage after ischemic stroke is a part of the mechanism through which fisetin is neuroprotective in cerebral IRI.

Research hotspots and frontiers of preconditioning in cerebral ischemia: A bibliometric analysis

Background

Preconditioning is a promising strategy against ischemic brain injury, and numerous studies in vitro and in vivo have demonstrated its neuroprotective effects. However, at present there is no bibliometric analysis of preconditioning in cerebral ischemia. Therefore, a comprehensive overview of the current status, hot spots, and emerging trends in this research field is necessary.

Materials and methods

Studies on preconditioning in cerebral ischemia from January 1999-December 2022 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace was used for data mining and visual analysis.

Results

A total of 1738 papers on preconditioning in cerebral ischemia were included in the study. The annual publications showed an upwards and then downwards trend but currently remain high in terms of annual publications. The US was the leading country, followed by China, the most active country in recent years. Capital Medical University published the largest number of articles. Perez-Pinzon, Miguel A contributed the most publications, while KITAGAWA K was the most cited author. The focus of the study covered three areas: (1) relevant diseases and experimental models, (2) types of preconditioning and stimuli, and (3) mechanisms of ischemic tolerance. Remote ischemic preconditioning, preconditioning of mesenchymal stem cells (MSCs), and inflammation are the frontiers of research in this field.

Conclusion

Our study provides a visual and scientific overview of research on preconditioning in cerebral ischemia, providing valuable information and new directions for researchers.

Stem Cell Therapies for Restorative Treatments of Central Nervous System Ischemia-Reperfusion Injury

Ischemic damage to the central nervous system (CNS) is a catastrophic postoperative complication of aortic occlusion subsequent to cardiovascular surgery that can cause brain impairment and sometimes even paraplegia. Over recent years, numerous studies have investigated techniques for protecting and revascularizing the nervous system during intraoperative ischemia; however, owing to a lack of knowledge of the physiological distinctions between the brain and spinal cord, as well as the limited availability of testing techniques and treatments for ischemia-reperfusion injury, the cause of brain and spinal cord ischemia-reperfusion injury remains poorly understood, and no adequate response steps are currently available in the clinic. Given the limited ability of the CNS to repair itself, it is of great clinical value to make full use of the proliferative and differentiation potential of stem cells to repair nerves in degenerated and necrotic regions by stem cell transplantation or mobilization, thereby introducing a novel concept for the treatment of severe CNS ischemia-reperfusion injury. This review summarizes the most recent advances in stem cell therapy for ischemia-reperfusion injury in the brain and spinal cord, aiming to advance basic research and the clinical use of stem cell therapy as a promising treatment for this condition.

Stem Cell- and Cell-Based Therapies for Ischemic Stroke

Stroke is the second cause of disability worldwide as it is expected to increase its incidence and prevalence. Despite efforts to increase the number of patients eligible for recanalization therapies, a significant proportion of stroke survivors remain permanently disabled. This outcome boosted the search for efficient neurorestorative methods. Stem cells act through multiple pathways: cell replacement, the secretion of growth factors, promoting endogenous reparative pathways, angiogenesis, and the modulation of neuroinflammation. Although neural stem cells are difficult to obtain, pose a series of ethical issues, and require intracerebral delivery, mesenchymal stem cells are less immunogenic, are easy to obtain, and can be transplanted via intravenous, intra-arterial, or intranasal routes. Extracellular vesicles and exosomes have similar actions and are easier to obtain, also allowing for engineering to deliver specific molecules or RNAs and to promote the desired effects. Appropriate timing, dosing, and delivery protocols must be established, and the possibility of tumorigenesis must be settled. Nonetheless, stem cell- and cell-based therapies for stroke have already entered clinical trials. Although safe, the evidence for efficacy is less impressive so far. Hopefully, the STEP guidelines and the SPAN program will improve the success rate. As such, stem cell- and cell-based therapy for ischemic stroke holds great promise.

NGF/TrkA promotes the vitality, migration and adhesion of bone marrow stromal cells in hypoxia by regulating the Nrf2 pathway

BACKGROUND

Bone marrow stromal cells (BMSCs) transplantation is a treatment strategy for ischemic stroke (IS) with great potential. However, the vitality, migration and adhesion of BMSCs are greatly impaired due to the harsh environment of the ischemic area, which affects the therapeutic effects. Herein, we aimed to investigate the roles of nerve growth factor (NGF) in regulating cell behaviors of BMSCs in IS.

METHODS

The mRNA and protein expressions were assessed using qRT-PCR and western blot, respectively. To simulate ischemic-like conditions in vitro, Brain microvascular (bEnd.3) cells were exposed to oxygen and glucose deprivation (OGD). Cell viability and cell proliferation were evaluated by MTT assay and BrdU assay, respectively. Transwell migration and cell adhesion assays were carried out to determine cell migration and adhesion of BMSCs, respectively, coupled with flow cytometry to evaluate cell apoptosis of bEnd.3 cells. Finally, angiogenesis assay was performed to assess the angiogenesis ability of bEnd.3 cells.

RESULTS

NGF overexpression resulted in increased cell vitality, adhesion and migration of BMSCs, while NGF knockdown presented the opposite effects. We subsequently discovered that TrkA was a receptor for NGF, and TrkA knockdown significantly inhibited the cell viability, migration and adhesion of BMSCs. Besides, Nrf2 was confirmed as the downstream target of NGF/TrkA to promote the viability, adhesion and migration of BMSC cells. Finally, NGF-silenced BMSCs could not effectively restore the OGD-induced brain microvascular cell damage.

CONCLUSIONS

NGF/TrkA promoted the viability, migration and adhesion of BMSCs in IS via activating Nrf2 pathway.

Preconditioning Methods to Improve Mesenchymal Stromal Cell-Derived Extracellular Vesicles in Bone Regeneration—A Systematic Review

Simple Summary

The evidence of the therapeutic effects of mesenchymal stromal cells (MSCs), so-called stem cells, in several diseases relies mostly on the substances they secrete, including their extracellular vesicles (EVs). EVs are an important component of cell communication and they carry a cargo that is similar to their parent cell. Cells respond differently based on their microenvironment, and so it is expected that the therapeutic potential of these vesicles can be modulated by the enrichment of their parent cell microenvironment. With this in mind, we conducted a systematic search for papers that preconditioned MSCs and collected their EVs to assess their potential to favor bone formation. The results showed different methods for MSC preconditioning, including chemical induction, culture conditions, and genetic modifications. All methods were able to improve the therapeutic effects of the derived EVs for bone formation. However, the heterogeneity among studies—regarding the type of cell, EV concentration, and scaffolds—made it difficult to compare fairly the types of preconditioning methods. In summary, the microenvironment greatly influences MSCs, and using preconditioning methods can potentially improve the therapeutic effects of their derived EVs in bone regeneration and other bone diseases.

Abstract

Mesenchymal stromal cells (MSCs) have long been used in research for bone regeneration, with evidence of their beneficial properties. In the segmental area of MSC-based therapies, MSC-derived extracellular vesicles (EVs) have also shown great therapeutic effects in several diseases, including bone healing. This study aimed to assess whether the conditioning of MSCs improves the therapeutic effects of their derived extracellular vesicles for bone regeneration. Electronic research was performed until February 2021 to recover the studies in the following databases: PubMed, Scopus, and Web of Science. The studies were screened based on the inclusion criteria. Relevant information was extracted, including in vitro and in vivo experiments, and the animal studies were evaluated for risk of bias by the SYRCLE tool. A total of 463 studies were retrieved, and 18 studies met the inclusion criteria (10 studies for their in vitro analysis, and 8 studies for their in vitro and in vivo analysis). The conditioning methods reported included: osteogenic medium; dimethyloxalylglycine; dexamethasone; strontium-substituted calcium silicate; hypoxia; 3D mechanical microenvironment; and the overexpression of miR-375, bone morphogenetic protein-2, and mutant hypoxia-inducible factor-1α. The conditioning methods of MSCs in the reported studies generate exosomes able to significantly promote bone regeneration. However, heterogeneity regarding cell source, conditioning method, EV isolation and concentration, and defect model was observed among the studies. The different conditioning methods reported in this review do improve the therapeutic effects of MSC-derived EVs for bone regeneration, but they still need to be addressed in larger animal models for further clinical application.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

Mesenchymal Stromal Cells Preconditioning: A New Strategy to Improve Neuroprotective Properties

Neurological diseases represent one of the main causes of disability in human life. Consequently, investigating new strategies capable of improving the quality of life in neurological patients is necessary. For decades, researchers have been working to improve the efficacy and safety of mesenchymal stromal cells (MSCs) therapy based on MSCs’ regenerative and immunomodulatory properties and multilinear differentiation potential. Therefore, strategies such as MSCs preconditioning are useful to improve their application to restore damaged neuronal circuits following neurological insults. This review is focused on preconditioning MSCs therapy as a potential application to major neurological diseases. The aim of our work is to summarize both the in vitro and in vivo studies that demonstrate the efficacy of MSC preconditioning on neuronal regeneration and cell survival as a possible application to neurological damage.

Hormesis and bone marrow stem cells: Enhancing cell proliferation, differentiation and resilience to inflammatory stress

This paper identifies and provides the first detailed assessment of hormetic dose responses by bone marrow stem cells (BMSCs) from a broad range of animal models and humans with particular emphasis on cell renewal (proliferation), cell differentiation and enhancing resilience to inflammatory stress. Such hormetic dose responses are commonly reported, being induced by a broad range of chemicals, including pharmaceuticals (e.g., caffeine, dexamethasone, nicotine), dietary supplements (e.g., curcumin, Ginkgo biloba, green tea extracts. resveratrol, sulforaphane), endogenous agents (e.g., hydrogen sulfide, interleukin 10), environmental contaminants (e.g., arsenic, PFOS) and physical stressor agents (e.g., EMF, shockwaves). Hormetic dose responses reported here for BMSCs are similar to those induced with other stem cell types [e.g., adipose-derived stem cells (ADSCs), dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), neuro stem cells (NSCs), embryonic stem cells (ESCs)], indicating a substantial degree of generality for hormetic responses in stem cells. The paper assesses both the underlying mechanistic foundations of BMSC hormetic responses and their potential therapeutic implications.

Inspiration for the prevention and treatment of neuropsychiatric disorders: New insight from the bone-brain-axis

Bone is the main supporting structure of the body and the main organ involved in body movement and calcium and phosphorus metabolism. Recent studies have shown that bone is also a potential new endocrine organ that participates in the physiological and pathophysiological processes of the cardiovascular, digestive, and endocrine systems through various bioactive cytokines secreted by bone cells and bone marrow. Bone-derived active cytokines can also directly act on the central nervous system and regulate brain function and individual behavior. The bidirectional regulation of the bone-brain axis has gradually attracted attention in the field of neuroscience. This paper reviews the regulatory effects of bone-derived active cytokines and bone-derived cells on individual brain function and brain diseases, as well as the occurrence and development of related neuropsychiatric diseases. The central regulatory mechanism function is briefly introduced, which will broaden the scope for mechanistic research and help establish prevention and treatment strategies for neuropsychiatric diseases based on the bone-brain axis.

Strategies to Improve the Efficiency of Transplantation with Mesenchymal Stem Cells for the Treatment of Ischemic Stroke: A Review of Recent Progress

Cerebral ischemia is a common global disease that is characterized by a loss of neurological function and a poor prognosis in many patients. However, only a limited number of treatments are available for this condition at present. Given that the efficacies of these treatments tend to be poor, cerebral ischemia can create a significant burden on patients, families, and society. Mesenchymal stem cell (MSC) transplantation treatment has shown significant potential in animal models of ischemic stroke; however, the specific mechanisms underlying this effect have yet to be elucidated. Furthermore, clinical trials have yet to yield promising results. Consequently, there is an urgent need to identify new methods to improve the efficiency of MSC transplantation as an optimal treatment for ischemic stroke. In this review, we provide an overview of recent scientific reports concerning novel strategies that promote MSC transplantation as an effective therapeutic approach, including physical approaches, chemical agents, traditional Chinese medicines and extracts, and genetic modification. Our analyses showed that two key factors need to be considered if we are to improve the efficacy of MSC transplantation treatments: survival ability and homing ability. We also highlight the importance of other significant mechanisms, including the enhanced activation of MSCs to promote neurogenesis and angiogenesis, and the regulation of permeability in the blood-brain barrier. Further in-depth investigations of the specific mechanisms underlying MSC transplantation treatment will help us to identify effective methods that improve the efficiency of MSC transplantation for ischemic stroke. The development of safer and more effective methods will facilitate the application of MSC transplantation as a promising adjuvant therapy for the treatment of poststroke brain damage.

Hypoxic preconditioning rejuvenates mesenchymal stem cells and enhances neuroprotection following intracerebral hemorrhage via the miR-326-mediated autophagy

BACKGROUND

Intracerebral hemorrhage (ICH) is a major public health concern, and mesenchymal stem cells (MSCs) hold great potential for treating ICH. However, the quantity and quality of MSCs decline in the cerebral niche, limiting the potential efficacy of MSCs. Hypoxic preconditioning is suggested to enhance the survival of MSCs and augment the therapeutic efficacy of MSCs in ICH. MicroRNAs (miRNAs) are known to mediate cellular senescence. However, the precise mechanism by which miRNAs regulate the senescence of hypoxic MSCs remains to be further studied. In the present study, we evaluated whether hypoxic preconditioning enhances the survival and therapeutic effects of olfactory mucosa MSC (OM-MSC) survival and therapeutic effects in ICH and investigated the mechanisms by which miRNA ameliorates hypoxic OM-MSC senescence.

METHODS

In the in vivo model, ICH was induced in mice by administration of collagenase IV. At 24 h post-ICH, 5 × 10⁵ normoxia or hypoxia OM-MSCs or saline was administered intracerebrally. The behavioral outcome, neuronal apoptosis, and OM-MSC survival were evaluated. In the in vitro model, OM-MSCs were exposed to hemin. Cellular senescence was examined by evaluating the expressions of P16INK4A, P21, P53, and by β-galactosidase staining. Microarray and bioinformatic analyses were performed to investigate the differences in the miRNA expression profiles between the normoxia and hypoxia OM-MSCs. Autophagy was confirmed using the protein expression levels of LC3, P62, and Beclin-1.

RESULTS

In the in vivo model, transplanted OM-MSCs with hypoxic preconditioning exhibited increased survival and tissue-protective capability. In the in vitro model, hypoxia preconditioning decreased the senescence of OM-MSCs exposed to hemin. Bioinformatic analysis identified that microRNA-326 (miR-326) expression was significantly increased in the hypoxia OM-MSCs compared with that of normoxia OM-MSCs. Upregulation of miR-326 alleviated normoxia OM-MSC senescence, whereas miR-326 downregulation increased hypoxia OM-MSC senescence. Furthermore, we showed that miR-326 alleviated cellular senescence by upregulating autophagy. Mechanistically, miR-326 promoted the autophagy of OM-MSCs via the PI3K signaling pathway by targeting polypyrimidine tract-binding protein 1 (PTBP1).

CONCLUSIONS

Our study shows that hypoxic preconditioning delays OM-MSC senescence and augments the therapeutic efficacy of OM-MSCs in ICH by upregulating the miR-326/PTBP1/PI3K-mediated autophagy.

Neuroprotective effects and mechanisms of ischemic/hypoxic preconditioning on neurological diseases

As the organ with the highest demand for oxygen, the brain has a poor tolerance to ischemia and hypoxia. Despite severe ischemia/hypoxia induces the occurrence and development of various central nervous system (CNS) diseases, sublethal insult may induce strong protection against subsequent fatal injuries by improving tolerance. Searching for potential measures to improve brain ischemic/hypoxic is of great significance for treatment of ischemia/hypoxia related CNS diseases. Ischemic/hypoxic preconditioning (I/HPC) refers to the approach to give the body a short period of mild ischemic/hypoxic stimulus which can significantly improve the body's tolerance to subsequent more severe ischemia/hypoxia event. It has been extensively studied and been considered as an effective therapeutic strategy in CNS diseases. Its protective mechanisms involved multiple processes, such as activation of hypoxia signaling pathways, anti-inflammation, antioxidant stress, and autophagy induction, etc. As a strategy to induce endogenous neuroprotection, I/HPC has attracted extensive attention and become one of the research frontiers and hotspots in the field of neurotherapy. In this review, we discuss the basic and clinical research progress of I/HPC on CNS diseases, and summarize its mechanisms. Furthermore, we highlight the limitations and challenges of their translation from basic research to clinical application.

Progress in Mesenchymal Stem Cell Therapy for Ischemic Stroke

Ischemic stroke (IS) is a serious cerebrovascular disease with high morbidity and disability worldwide. Despite the great efforts that have been made, the prognosis of patients with IS remains unsatisfactory. Notably, recent studies indicated that mesenchymal stem cell (MSCs) therapy is becoming a novel research hotspot with large potential in treating multiple human diseases including IS. The current article is aimed at reviewing the progress of MSC treatment on IS. The mechanism of MSCs in the treatment of IS involved with immune regulation, neuroprotection, angiogenesis, and neural circuit reconstruction. In addition, nutritional cytokines, mitochondria, and extracellular vesicles (EVs) may be the main mediators of the therapeutic effect of MSCs. Transplantation of MSCs-derived EVs (MSCs-EVs) affords a better neuroprotective against IS when compared with transplantation of MSCs alone. MSC therapy can prolong the treatment time window of ischemic stroke, and early administration within 7 days after stroke may be the best treatment opportunity. The deliver routine consists of intraventricular, intravascular, intranasal, and intraperitoneal. Furthermore, several methods such as hypoxic preconditioning and gene technology could increase the homing and survival ability of MSCs after transplantation. In addition, MSCs combined with some drugs or physical therapy measures also show better neurological improvement. These data supported the notion that MSC therapy might be a promising therapeutic strategy for IS. And the application of new technology will promote MSC therapy of IS.

Hypoxic Preconditioning Enhances the Efficacy of Mesenchymal Stem Cells-Derived Conditioned Medium in Switching Microglia toward Anti-inflammatory Polarization in Ischemia/Reperfusion

Activation of pro-inflammatory microglia is an important mechanism of the cerebral ischemia-reperfusion (I/R)-induced neuronal injury and dysfunction. Mesenchymal stem cells (MSCs) together with their paracrine factors demonstrated curative potential in immune disorders and inflammatory diseases, as well as in ischemic diseases. However, it remains unclear whether conditioned medium from MSCs could effectively regulate the activation and polarization of microglia exposed to I/R stimulation. In this study, we investigated the effects of conditioned medium from bone marrow MSCs (BMSCs-CM) on I/R-stimulated microglia and the potential mechanism involved, as well as the way to obtain more effective BMSCs-CM. First, cell model of oxygen-glucose deprivation/reoxygenation (OGD/R) was established in microglia to mimic the I/R. BMSCs-CM from different culture conditions (normoxic: 21% O2; hypoxic: 1% O2; hypoxia preconditioning: preconditioning with 1% O2 for 24 h) was used to treat the microglia. Our results showed that BMSCs-CM effectively promoted the survival and alleviated the injury of microglia. Moreover, in microglia exposed to OGD/R, BMSCs-CM inhibited significantly the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), CD86 and inducible nitric oxide synthase, whereas upregulated the levels of anti-inflammatory cytokine (IL-10), CD206 and Arginase-1. These results suggested that BMSCs-CM promoted the polarization of anti-inflammatory microglia. In particular, BMSCs-CM from cultures with hypoxia preconditioning was more effective in alleviating cell injury and promoting anti-inflammatory microglia polarization than BMSCs-CM from normoxic cultures and from hypoxic cultures. Furthermore, inhibition of exosomes secretion could largely mitigate these effects of BMSCs-CM. In conclusion, our results suggested that hypoxia preconditioning of BMSCs could enhance the efficacy of BMSCs-CM in alleviating OGD/R-induced injury and in promoting the anti-inflammatory polarization of microglia, and these beneficial effects of BMSCs-CM owed substantially to exosomes.

Lithium and Copper Induce the Osteogenesis-Angiogenesis Coupling of Bone Marrow Mesenchymal Stem Cells via Crosstalk between Canonical Wnt and HIF-1α Signaling Pathways

The combination of osteogenesis and angiogenesis dual-delivery trace element-carrying bioactive scaffolds and stem cells is a promising method for bone regeneration and repair. Canonical Wnt and HIF-1α signaling pathways are vital for BMSCs' osteogenic differentiation and secretion of osteogenic factors, respectively. Simultaneously, lithium (Li) and copper (Cu) can activate the canonical Wnt and HIF-1α signaling pathway, respectively. Moreover, emerging evidence has shown that the canonical Wnt and HIF signaling pathways are related to coupling osteogenesis and angiogenesis. However, it is still unclear whether the lithium- and copper-doped bioactive scaffold can induce the coupling of the osteogenesis and angiogenesis in BMSCs and the underlying mechanism. So, we fabricated a lithium- (Li+-) and copper- (Cu2+-) doped organic/inorganic (Li 2.5-Cu 1.0-HA/Col) scaffold to evaluate the coupling osteogenesis and angiogenesis effects of lithium and copper on BMSCs and further explore its mechanism. We investigated that the sustained release of lithium and copper from the Li 2.5-Cu 1.0-HA/Col scaffold could couple the osteogenesis- and angiogenesis-related factor secretion in BMSCs seeding on it. Moreover, our results showed that 500 μM Li+ could activate the canonical Wnt signaling pathway and rescue the XAV-939 inhibition on it. In addition, we demonstrated that the 25 μM Cu2+ was similar to 1% oxygen environment in terms of the effectiveness of activating the HIF-1α signaling pathway. More importantly, the combination stimuli of Li+ and Cu2+ could couple the osteogenesis and angiogenesis process and further upregulate the osteogenesis- and angiogenesis-related gene expression via crosstalk between the canonical Wnt and HIF-1α signaling pathway. In conclusion, this study revealed that lithium and copper could crosstalk between the canonical Wnt and HIF-1α signaling pathways to couple the osteogenesis and angiogenesis in BMSCs when they are sustainably released from the Li-Cu-HA/Col scaffold.

Mesenchymal stem cells from a hypoxic culture improve nerve regeneration

Repairing the peripheral nerves following a segmental defect injury remains surgically challenging. Because of some disadvantages of nerve grafts, nerve regeneration, such as conduits combined with bone marrow-derived mesenchymal stem cells (BMSCs), may serve as an alternative. BMSCs expand under hypoxic conditions, decrease in senescence, and increase in proliferation and differentiation potential into the bone, fat, and cartilage. The purpose of this study was to investigate whether BMSCs increased the neuronal differentiation potential following expansion under hypoxic conditions. Isolated human BMSCs (hBMSCs) expand under hypoxia or normoxia, and neuronal differentiation proceeds under normoxia. in vitro tests revealed hypoxia culture enhanced the RNA and protein expression of neuronal markers. The electrophysiology of hBMSC-differentiated neuron-like cells was also enhanced by the hypoxia culturing. Our animal model indicated that the potential treatment of hypoxic rat BMSCs (rBMSCs) was better than that of normoxic rBMSCs because the conduit with the hypoxic rBMSCs injection demonstrated the highest recovery rate of gastrocnemius muscle weights. There were more toluidine blue-stained myelinated nerve fibers in the hypoxic rBMSCs group than in the normoxic group. To sum up, BMSCs cultured under hypoxia increased the potential of neuronal differentiation both in vivo and in vitro.

Hypoxic preconditioning ameliorated neuronal injury after middle cerebral artery occlusion by promoting neurogenesis

OBJECTIVES

Sequelae of stroke were mainly caused by neuronal injury. Oxygen is a key factor affecting the microenvironment of neural stem cells (NSCs), and oxygen levels are used to promote NSC neurogenesis. In this study, effects of intermittent hypoxic preconditioning (HPC) on neurogenesis were investigated in a rat model of middle cerebral artery occlusion (MCAO).

METHODS

SD rats were used to establish the MCAO model. Nissl staining and Golgi staining were used to confirm the neuronal injury status in the MCAO model. Immunofluorescence, transmission electron microscopy, Western blot, and qPCR were used to observe the effects of HPC on neurogenesis. At the same time, the hypothesis that HPC could affect proliferation, apoptosis, differentiation, and migration of NSC was verified in vitro.

RESULTS

Hypoxic preconditioning significantly ameliorated the neuronal injury induced by MCAO. Compared with MCAO group, the dendrites, Edu⁺ /SOX2⁺ , Edu⁺ /DCX⁺ , Edu⁺ /NeuN⁺ , Edu⁺ /GFAP⁺ , and Edu⁺ /Tubulin⁺ positive cells in the HPC + MCAO group exhibited significantly difference. Similarly, axonal and other neuronal injuries in the HPC + MCAO group were also ameliorated. In the in vitro experiments, mild HPC significantly enhanced the viability of NSCs, promoted the migration of differentiated cells, and reduced apoptosis.

CONCLUSIONS

Our results showed that HPC significantly promotes neurogenesis after MCAO and ameliorates neuronal injury.

Intracerebral transplantation of HLA-homozygous human iPSC-derived neural precursors ameliorates the behavioural and pathological deficits in a rodent model of ischaemic stroke

OBJECTIVES

Human-induced pluripotent stem cells (hiPSCs) are a promising cell source for treating ischaemic stroke. Although autologous hiPSCs provide the advantage of avoiding immune rejection, their practical limitations, such as substantial amount of time and costs to generate individual iPSC lines, have hampered their widespread application in clinical settings. In this study, we investigated the therapeutic potential of neural precursor cells derived from human HLA-homozygous induced pluripotent stem cells (hiPSC-NPCs) following intracerebral transplantation into a rodent model of middle cerebral artery occlusion (MCAo).

MATERIALS AND METHODS

We differentiated a GMP-grade HLA-homozygous hiPSC line (CMC-hiPSC-004) into neural precursor cells for transplantation into rats at the subacute stage of ischaemic stroke (ie at 7 days after the induction of MCAo). To investigate functional recovery, the transplanted animals were subjected to five behavioural tests, namely the rotarod, stepping, mNSS, staircase and apomorphine-induced rotation tests, for up to 12 weeks, followed by histological analyses.

RESULTS

We observed that the hiPSC-NPC transplantation produced significant behavioural improvements. At 12 weeks post-transplantation, a high proportion of transplanted cells survived and had differentiated into MAP2⁺ mature neurons, GABAergic neurons and DARPP32⁺ medium spiny neurons. The transplanted cells formed neuronal connections with striatal neurons in the host brain. In addition, hiPSC-NPC transplantation gave rise to enhanced endogenous repair processes, including decreases of post-stroke neuroinflammation and glial scar formation and an increase of proliferating endogenous neural stem cells in the subventricular zone as well as the perilesional capillary networks.

CONCLUSIONS

These results strongly suggest that HLA-homozygous hiPSC-NPCs may be useful for treating ischaemic stroke patients.

Effects of the Insulted Neuronal Cells-Derived Extracellular Vesicles on the Survival of Umbilical Cord-Derived Mesenchymal Stem Cells following Cerebral Ischemia/Reperfusion Injury

Umbilical cord-derived mesenchymal stem cells (UC-MSCs) engraftment is a potential therapy for cerebral ischemic stroke. However, the harsh microenvironment induced by cerebral ischemia/reperfusion restricts the survival rate and therapeutic efficiency of the engrafted UC-MSCs. In this study, we explored whether small extracellular vesicles (EVs) derived from injured neuronal cells following exposure to cerebral ischemia/reperfusion insult affect the survival of transplanted UC-MSCs. To establish a simulation of cerebral ischemia/reperfusion microenvironment comprising engrafted UC-MSCs and neuronal cells, we cocultured EVs derived from injured N2A cells, caused by exposure to oxygen-glucose deprivation and reperfusion (OGD/R) insult, with UC-MSCs in a conditioned medium. Coculture of UC-MSCs with EVs exacerbated the OGD/R-induced apoptosis and oxidative stress. Suppression of EVs-release via knock-down of Rab27a effectively protected the UC-MSCs from OGD/R-induced insult. Moreover, hypoxia preconditioning not only elevated the survival of UC-MSCs but also improved the paracrine mechanism of injured N2A cells. Altogether, these results show that EVs from injured N2A cells exacerbates OGD/R-induced injury on transplanted UC-MSCs in vitro. Hypoxia preconditioning enhances the survival of the engrafted-UC-MSCs; hence, thus could be an effective approach for improving UC-MSCs therapy in ischemic stroke.

Hypoxic preconditioning enhances the differentiation of bone marrow stromal cells into mature oligodendrocytes via the mTOR/HIF-1α/VEGF pathway in traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) results not only in gray matter damage, but also in severe white matter injury (WMI). Previous findings support hypoxic preconditioning (HP) could augment the efficacy of bone marrow stromal cell (BMSC) transplantation in a TBI mouse model. However, whether HP-treated BMSCs (H-BMSCs) could overcome remyelination failure after WMI is unclear, and the molecular mechanisms remain to be explored. Here, we focused on the therapeutic benefits of H-BMSC transplantation for treating WMI, as well as its underlying mechanisms.

METHODS

In vitro, BMSCs were incubated at passage 4 in the hypoxic preconditioning (1.0% oxygen) for 8 hr. In vivo, a TBI mouse model was established, and DMEM cell culture medium (control), normal cultured BMSCs (N-BMSCs), or H-BMSCs were transplanted to mice 24 hr afterward. Neurobehavioral function, histopathological changes, and oligodendrogenesis were assessed for up to 35 days post-TBI.

RESULTS

Compared with the control group, improvement of cognitive functions and smaller lesion volumes was observed in the two BMSC-transplanted groups, especially the H-BMSC group. H-BMSC transplantation resulted in a greater number of neural/glial antigen 2 (NG2)-positive and adenomatous polyposis coli (APC)-positive cells than N-BMSC transplantation in both the corpus callosum and the striatum. In addition, we observed that the expression levels of hypoxia-inducible factor-1a (HIF-1α), phosphorylated mechanistic target of rapamycin (p-mTOR), and vascular endothelial growth factor (VEGF) were all increased in H-BMSC-transplanted mice. Furthermore, the mTOR pathway inhibitor rapamycin attenuated the impact of HP both in vivo and in vitro.

CONCLUSION

The results provided mechanistic evidences suggesting that HP-treated BMSCs promoted remyelination partly by modulating the pro-survival mTOR/HIF-1α/VEGF signaling pathway.

In Search of a Dose: The Functional and Molecular Effects of Exercise on Post-stroke Rehabilitation in Rats

Although physical exercise has been demonstrated to augment recovery of the post-stroke brain, the question of what level of exercise intensity optimizes neurological outcomes of post-stroke rehabilitation remains unsettled. In this study, we aim to clarify the mechanisms underlying the intensity-dependent effect of exercise on neurologic function, and thereby to help direct the clinical application of exercise-based neurorehabilitation. To do this, we used a well-established rat model of ischemic stroke consisting of cerebral ischemia induction through middle cerebral artery occlusion (MCAO). Ischemic rats were subsequently assigned either to a control group entailing post-stroke rest or to one of two exercise groups distinguished by the intensity of their accompanying treadmill regimens. After 24 h of reperfusion, exercise was initiated. Infarct volume, apoptotic cell death, and neurological defects were quantified in all groups at 3 days, and motor and cognitive functions were tracked up to day-28. Additionally, Western blotting was used to assess the influence of our interventions on several proteins related to synaptogenesis and neuroplasticity (growth-associated protein 43, a microtubule-associated protein, postsynaptic density-95, synapsin I, hypoxia-inducible factor-1α, brain-derived neurotrophic factor, nerve growth factor, tyrosine kinase B, and cAMP response element-binding protein). Our results were in equal parts encouraging and surprising. Both mild and intense exercise significantly decreased infarct volume, cell death, and neurological deficits. Motor and cognitive function, as determined using an array of tests such as beam balance, forelimb placing, and the Morris water maze, were also significantly improved by both exercise protocols. Interestingly, while an obvious enhancement of neuroplasticity proteins was shown in both exercise groups, mild exercise rats demonstrated a stronger effect on the expressions of Tau (p < 0.01), brain-derived neurotrophic factor (p < 0.01), and tyrosine kinase B (p < 0.05). These findings contribute to the growing body of literature regarding the positive effects of both mild and intense long-term treadmill exercise on brain injury, functional outcome, and neuroplasticity. Additionally, the results may provide a base for our future study regarding the regulation of HIF-1α on the BDNF/TrkB/CREB pathway in the biochemical processes underlying post-stroke synaptic plasticity.

Synergistic Effects of Mesenchymal Stem Cell Transplantation and Repetitive Transcranial Magnetic Stimulation on Promoting Autophagy and Synaptic Plasticity in Vascular Dementia

Repetitive transcranial magnetic stimulation (rTMS) and mesenchymal stem cells (MSCs) transplantation both showed therapeutic effects on cognition impairment in vascular dementia (VD) model rats. However, whether these two therapies have synergistic effects and the molecular mechanisms remain unclear. In our present study, rats were randomly divided into six groups: control group, sham operation group, VD group, MSC group, rTMS group, and MSC+rTMS group. The VD model rats were prepared using a modified 2VO method. rTMS treatment was implemented at a frequency of 5 Hz, the stimulation intensity for 0.5 Tesla, 20 strings every day with 10 pulses per string and six treatment courses. The results of the Morris water maze test showed that the learning and memory abilities of the MSC group, rTMS group, and MSC+rTMS group were better than that of the VD group, and the MSC+rTMS group showed the most significant effect. The protein expression levels of brain-derived neurotrophic factor, NR1, LC3-II, and Beclin-1 were the highest and p62 protein was the lowest in the MSC+rTMS group. Our findings demonstrated that rTMS could further enhance the effect of MSC transplantation on VD rats and provided an important basis for the combined application of MSC transplantation and rTMS to treat VD or other neurological diseases.

HIF‑1α attenuates neuronal apoptosis by upregulating EPO expression following cerebral ischemia‑reperfusion injury in a rat MCAO model

Hypoxia-inducible factor-1α (HIF-1α) is a key transcriptional factor in response to hypoxia and is involved in ischemic stroke. In the present study, the potential for HIF-1α to inhibit neuronal apoptosis through upregulating erythropoietin (EPO) was investigated in a transient middle cerebral artery occlusion (tMCAO) rat stroke model. For this purpose, a recombinant adenovirus expressing HIF-1α was engineered (Ad-HIF-1α). Control adenovirus (Ad group), Ad-HIF-1α (Ad-HIF-1α group) or Ad-HIF-1α in addition to erythropoietin mimetic peptide-9 (EMP9), an EPO-receptor (-R) antagonist (Ad-HIF-1α+EMP9 group), were used for an intracranial injection into rat ischemic penumbra 1 h following MCAO. All rats demonstrated functional improvement following tMCAO, while the improvement rate was faster in rats treated by Ad-HIF-1α compared with all other groups. The EPO-R inhibitor partially reversed the benefits of Ad-HIF-1α. Apoptosis induced by tMCAO was significantly inhibited by Ad-HIF-1α (P<0.05). The expression of HIF-1α, evaluated by immunohistochemistry either in neurons or astrocytes, was upregulated by Ad-HIF-1α. Both EPO mRNA and protein expression were increased by Ad-HIF-1α, however, there was no significant change of EPO-R either on an mRNA level or protein level. Furthermore, EMP9 did not change the EPO expression which was upregulated by Ad-HIF-1α. Activated caspase 3 in neurons was suppressed by Ad-HIF-1α. Activated caspase 3 downregulated by HIF-1α was partially blocked by EMP9. Altogether, the present data demonstrated that HIF-1α attenuates neuronal apoptosis partially through upregulating EPO following cerebral ischemia in rat. Thus, upregulating HIF-1α subsequent to a stroke may be a potential treatment for ischemic stroke.

Recent Advances in Mono- and Combined Stem Cell Therapies of Stroke in Animal Models and Humans

Following the failure of acute neuroprotection therapies, major efforts are currently made worldwide to promote neurological recovery and brain plasticity in the subacute and post-acute phases of stroke. Currently, there is hope that stroke recovery might be promoted by cell-based therapies. The field of stem cell therapy for cerebral ischemia has made significant progress in the last five years. A variety of stem cells have been tested in animal models and humans including adipose stem cells, human umbilical cord blood-derived mesenchymal stem cells, human amnion epithelial cells, human placenta amniotic membrane-derived mesenchymal stem cells, adult human pluripotent-like olfactory stem cells, human bone marrow endothelial progenitor cells, electrically-stimulated human neuronal progenitor cells, or induced pluripotent stem cells (iPSCs) of human origin. Combination therapies in animal models include a mix of two or more therapeutic factors consisting of bone marrow stromal cells, exercise and thyroid hormones, endothelial progenitor cells overexpressing the chemokine CXCL12. Mechanisms underlying the beneficial effects of transplanted cells include the “bystander” effects, paracrine mechanisms, or extracellular vesicles-mediated restorative effects. Mitochondria transfer also appears to be a powerful strategy for regenerative processes. Studies in humans are currently limited to a small number of studies using autologous stem cells mainly aimed to assess tolerability and side-effects of human stem cells in the clinic.

Three-Dimensional Printed Titanium Scaffolds Enhance Osteogenic Differentiation and New Bone Formation by Cultured Adipose Tissue-Derived Stem Cells Through the IGF-1R/AKT/Mammalian Target of Rapamycin Complex 1 (mTORC1) Pathway

Background

This study aimed to investigate the effects of three-dimensional (3D) printed titanium (3DTi) scaffolds on osteogenic differentiation and new bone formation by 3D cultured adipose tissue-derived stem cells (ADSCs) in vitro, and the effects of bone regeneration in vivo using a full-thickness mandibular defect rat model, and the mechanisms involved.

Material/Methods

Alpha-beta titanium alloy (Ti6Al4V) 3DTi scaffolds were prepared with Cellmatrix hydrogel and 3D culture medium. ADSCs were impregnated into the 3DTi scaffolds. ADSC viability and proliferation were assessed using the cell counting kit-8 (CCK-8) assay, and alkaline phosphatase (ALP) levels were measured. Real-time polymerase chain reaction (RT-PCR) and Western blot were performed to assess the expression of osteogenesis-related mRNA for RUNX2, OPN, OCN, and IGF-1 genes and proteins. A rat model of full-thickness mandibular defect was evaluated with micro-computed tomography (microCT) scanning, and histochemistry with Alizarin red and von Giesen’s stain were used to evaluate osteogenesis.

Results

ADSC viability and proliferation were not affected by culture with 3DTi scaffolds. Expression of osteogenesis-related mRNA and proteins for RUNX2, OPN, OCN, and IGF-1, expression of ALP, and histochemical findings showed that the use of 3DTi scaffolds enhanced osteogenic differentiation and new bone formation by ADSCs, with upregulation of components of the IGF-1R/AKT/mTORC1 pathway.

Conclusions

The 3D culture of ADSCs with 3DTi scaffolds enhanced osteogenic differentiation and new bone formation through the IGF-1R/AKT/mTORC1 pathway. This improved method of osteointegration may have clinical application in the preparation of bone grafts before implantation for improved repair of mandibular bone defects.

Understanding and leveraging cell metabolism to enhance mesenchymal stem cell transplantation survival in tissue engineering and regenerative medicine applications

In tissue engineering and regenerative medicine, stem cell-specifically, mesenchymal stromal/stem cells (MSCs)-therapies have fallen short of their initial promise and hype. The observed marginal, to no benefit, success in several applications has been attributed primarily to poor cell survival and engraftment at transplantation sites. MSCs have a metabolism that is flexible enough to enable them to fulfill their various cellular functions and remarkably sensitive to different cellular and environmental cues. At the transplantation sites, MSCs experience hostile environments devoid or, at the very least, severely depleted of oxygen and nutrients. The impact of this particular setting on MSC metabolism ultimately affects their survival and function. In order to develop the next generation of cell-delivery materials and methods, scientists must have a better understanding of the metabolic switches MSCs experience upon transplantation. By designing treatment strategies with cell metabolism in mind, scientists may improve survival and the overall therapeutic potential of MSCs. Here, we provide a comprehensive review of plausible metabolic switches in response to implantation and of the various strategies currently used to leverage MSC metabolism to improve stem cell-based therapeutics.

Enhanced Migration of Bone Marrow-Derived Mesenchymal Stem Cells with Tetramethylpyrazine and Its Synergistic Effect on Angiogenesis and Neurogenesis After Cerebral Ischemia in Rats

Bone marrow-derived mesenchymal stem cells (BMSCs) hold great promise for treating ischemic stroke owing to their capacity to secrete various trophic factors with potent angiogenic and neurogenic potentials. However, the relatively poor migratory capacity of BMSCs toward infarcted regions limits effective therapies for the treatment of stroke. The combination of BMSCs and pharmacological agent can promote the migration of BMSCs toward infarcted regions and improve the therapeutic effects after stroke. In this study, we aimed to investigate whether BMSCs combined with tetramethylpyrazine (TMP) enhanced BMSC migration into the ischemic brain, which had better therapeutic effect in the treatment of stroke. In a rat stroke model, we found that combination treatment significantly upregulated ischemic brain stromal-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) expressions, and promoted BMSCs homing toward the ischemic regions than BMSC monotherapy. Moreover, BMSCs combined with TMP synergistically increased the expression of vascular endothelial growth factor and brain-derived neurotrophic factor, promoted angiogenesis and neurogenesis, and improved functional outcome after stroke. These results suggest that combination treatment could not only enhance the migration of BMSCs into the ischemic brain but also act in a synergistic way to potentiate endogenous repair processes and functional recovery after ischemic stroke.

Rotating and Neurochemical Activity of Rats Lesioned with Quinolinic Acid and Transplanted with Bone Marrow Mononuclear Cells

Huntington’s disease (HD) is an inherited, neurodegenerative disorder that results from the degeneration of striatal neurons, mainly GABAergic neurons. The study of neurochemical activity has provided reliable markers to explain motor disorders. To treat neurodegenerative diseases, stem cell transplants with bone marrow (BM) have been performed for several decades. In this work we determine the effect of mononuclear bone marrow cell (mBMC) transplantation on the rotational behavior and neurochemical activity in a model of Huntington’s disease in rats. Four experimental groups were organized: Group I: Control animals (n = 5); Group II: Lesion with quinolinic acid (QA) in the striatum (n = 5); Group III: Lesion with QA and transplant with mBMC (n = 5); Group IV: Lesion with QA and transplant with culture medium (Dulbecco’s modified Eagle’s medium (DMEM) injection) (n = 5). The rotational activity induced by D-amphetamine was evaluated and the concentration of the neurotransmitter amino acids (glutamate and GABA) was studied. The striatal cell transplantation decreases the rotations induced by D-amphetamine (p < 0.04, Wilcoxon matched pairs test) and improves the changes produced in the levels of neurotransmitters studied. This work suggests that the loss of GABAergic neurons in the brain of rats lesioned with AQ produces behavioral and neurochemical alterations that can be reversed with the use of bone marrow mononuclear cell transplants.

3D Culture of Bone Marrow-Derived Mesenchymal Stem Cells (BMSCs) Could Improve Bone Regeneration in 3D-Printed Porous Ti6Al4V Scaffolds

Mandibular bone defect reconstruction is an urgent challenge due to the requirements for daily eating and facial aesthetics. Three-dimensional- (3D-) printed titanium (Ti) scaffolds could provide patient-specific implants for bone defects. Appropriate load-bearing properties are also required during bone reconstruction, which makes them potential candidates for mandibular bone defect reconstruction implants. However, in clinical practice, the insufficient osteogenesis of the scaffolds needs to be further improved. In this study, we first encapsulated bone marrow-derived mesenchymal stem cells (BMSCs) into Matrigel. Subsequently, the BMSC-containing Matrigels were infiltrated into porous Ti6Al4V scaffolds. The Matrigels in the scaffolds provided a 3D culture environment for the BMSCs, which was important for osteoblast differentiation and new bone formation. Our results showed that rats with a full thickness of critical mandibular defects treated with Matrigel-infiltrated Ti6Al4V scaffolds exhibited better new bone formation than rats with local BMSC injection or Matrigel-treated defects. Our data suggest that Matrigel is able to create a more favorable 3D microenvironment for BMSCs, and Matrigel containing infiltrated BMSCs may be a promising method for enhancing the bone formation properties of 3D-printed Ti6Al4V scaffolds. We suggest that this approach provides an opportunity to further improve the efficiency of stem cell therapy for the treatment of mandibular bone defects.

Hypoxic conditioned medium derived from bone marrow mesenchymal stromal cells protects against ischemic stroke in rats

In recent years, studies have shown that the secretome of bone marrow mesenchymal stromal cells (BMSCs) contains many growth factors, cytokines, and antioxidants, which may provide novel approaches to treat ischemic diseases. Furthermore, the secretome may be modulated by hypoxic preconditioning. We hypothesized that conditioned medium (CM) derived from BMSCs plays a crucial role in reducing tissue damage and improving neurological recovery after ischemic stroke and that hypoxic preconditioning of BMSCs robustly improves these activities. Rats were subjected to ischemic stroke by middle cerebral artery occlusion and then intravenously administered hypoxic CM, normoxic CM, or Dulbecco modified Eagle medium (DMEM, control). Cytokine antibody arrays and label-free quantitative proteomics analysis were used to compare the differences between hypoxic CM and normoxic CM. Injection of normoxic CM significantly reduced the infarct area and improved neurological recovery after stroke compared with administering DMEM. These outcomes may be associated with the attenuation of apoptosis and promotion of angiogenesis. Hypoxic preconditioning significantly enhanced these therapeutic effects. Fourteen proteins were significantly increased in hypoxic CM compared with normoxic CM as measured by cytokine arrays. The label-free quantitative proteomics analysis revealed 163 proteins that were differentially expressed between the two groups, including 107 upregulated proteins and 56 downregulated proteins. Collectively, our results demonstrate that hypoxic CM protected brain tissue from ischemic injury and promoted functional recovery after stroke in rats and that hypoxic CM may be the basis of a potential therapy for stroke patients.

Transplantation of Hypoxic-Preconditioned Bone Mesenchymal Stem Cells Retards Intervertebral Disc Degeneration via Enhancing Implanted Cell Survival and Migration in Rats

OBJECTIVE

Special hypoxic and hypertonic microenvironment in intervertebral discs (IVDs) decreases the treatment effect of cell transplantation. We investigated the hypothesis that hypoxic preconditioning (HP) could improve the therapeutic effect of bone mesenchymal stem cells (BMSCs) to IVD degeneration.

METHODS

BMSCs from green fluorescent protein-transgenic rats were pretreated with cobalt chloride (CoCl2, 100 μM, 24 h) for hypoxic conditions in vitro. Apoptosis (related pathways of caspase-3 and bcl-2) and migration (related pathways of HIF-1α and CXCR4) were detected in BMSCs. In vivo, BMSCs and HP BMSCs (H-BMSCs) were injected into the rat model of IVD degeneration. The IVD height, survival, migration, and differentiation of transplanted BMSCs and matrix protein expression (collagen II, aggrecan, and MMP-13) were tested.

RESULTS

H-BMSCs could extensively decrease IVD degeneration by increasing IVD height and collagen II and aggrecan expressions when compared with BMSCs. Significantly, more GFP-positive BMSCs were observed in the nucleus pulposus and annulus fibrosus regions of IVD. HP could significantly decrease BMSC apoptosis (activating bcl-2 and inhibiting caspase-3) and improve BMSC migration (increasing HIF-1α and CXCR4) in vitro.

CONCLUSION

HP could significantly enhance the capacity of BMSCs to repair DDD by increasing the survival and migration of implanted cells and increasing matrix protein expression.