Mesenchymal stromal cell‐derived extracellular vesicles as cell‐free biologics for the ex vivo expansion of hematopoietic stem cells

Neurological efficacy and safety of mesenchymal stem cells (MSCs) therapy in people with multiple sclerosis (pwMS): An updated systematic review and meta-analysis

BACKGROUND

Current therapeutic strategies for multiple sclerosis (MS) aim to suppress the immune response and reduce relapse rates. As alternative treatments, mesenchymal stem cells (MSCs) are being explored. MSCs show promise in repairing nerve tissue and reducing autoimmune responses in people with MS (pwMS).

OBJECTIVE

This review delves into the literature on the efficacy and safety of MSC therapy for pwMS.

METHODS

A comprehensive search strategy was employed to identify relevant articles from five databases until January 2024. The inclusion criteria encompassed interventional studies. Efficacy and safety data concerning MSC therapy in relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), and primary progressive MS (PPMS) groups were extracted and analyzed.

RESULTS

A comprehensive analysis encompassing 30 studies revealed that individuals who underwent intrathecal (IT) protocol-based transplantation of MSCs experienced a noteworthy improvement in their expanded disability status scale (EDSS) compared to the placebo group. Weighted mean difference (WMD) was -0.28; 95 % CI -0.53 to -0.03, I2 = 0 %, p-value = 0.028); however, the intravenous (IV) group did not show significant changes in EDSS scores. The annualized relapse rate (ARR) did not significantly decrease among pwMS (WMD = -0.34; 95 % CI -1.05 to 0.38, I2 = 98 %, p-value = 0.357). Favorable results were observed in magnetic resonance imaging (MRI), with only 19.11 % of pwMS showing contrast-enhanced lesions (CEL) in the short term and no long-term MRI activity. The most common complications in both short-term and long-term follow-ups were infection, back pain, and gastrointestinal symptoms.

CONCLUSIONS

The study highlights the safety potential of MSC therapy for pwMS. While MRI-based neural regeneration shows significant treatment potential, the effectiveness of MSC therapy remains uncertain due to study limitations and ineffective outcome measures. Further research is needed to establish efficacy and optimize evaluation methods for MSC therapy on pwMS.

The Therapeutic Effects of Blueberry-Treated Stem Cell-Derived Extracellular Vesicles in Ischemic Stroke

An ischemic stroke, one of the leading causes of morbidity and mortality, is caused by ischemia and hemorrhage resulting in impeded blood supply to the brain. According to many studies, blueberries have been shown to have a therapeutic effect in a variety of diseases. Therefore, in this study, we investigated whether blueberry-treated mesenchymal stem cell (MSC)-derived extracellular vesicles (B-EVs) have therapeutic effects in in vitro and in vivo stroke models. We isolated the extracellular vesicles using cryo-TEM and characterized the particles and concentrations using NTA. MSC-derived extracellular vesicles (A-EVs) and B-EVs were round with a lipid bilayer structure and a diameter of ~150 nm. In addition, A-EVs and B-EVs were shown to affect angiogenesis, cell cycle, differentiation, DNA repair, inflammation, and neurogenesis following KEGG pathway and GO analyses. We investigated the protective effects of A-EVs and B-EVs against neuronal cell death in oxygen-glucose deprivation (OGD) cells and a middle cerebral artery occlusion (MCAo) animal model. The results showed that the cell viability was increased with EV treatment in HT22 cells. In the animal, the size of the cerebral infarction was decreased, and the behavioral assessment was improved with EV injections. The levels of NeuN and neurofilament heavy chain (NFH)-positive cells were also increased with EV treatment yet decreased in the MCAo group. In addition, the number of apoptotic cells was decreased with EV treatment compared with ischemic animals following TUNEL and Bax/Bcl-2 staining. These data suggested that EVs, especially B-EVs, had a therapeutic effect and could reduce apoptotic cell death after ischemic injury.

Therapeutic targeting and HSC proliferation by small molecules and biologicals

Hematopoietic stem cells (HSCs) have considerably therapeutic value on autologous and allogeneic transplantation for many malignant/non-malignant hematological diseases, especially with improvement of gene therapy. However, acquirement of limited cell dose from HSC sources is the main handicap for successful transplantation. Therefore, many strategies based on the utilization of various cytokines, interaction of stromal cells, modulation of several extrinsic and intrinsic factors have been developed to promote ex vivo functional HSC expansion with high reconstitution ability until today. Besides all these strategies, small molecules become prominent with their ease of use and various advantages when they are translated to the clinic. In the last two decades, several small molecule compounds have been investigated in pre-clinical studies and, some of them were evaluated in different stages of clinical trials for their safety and efficiencies. In this chapter, we will present an overview of HSC biology, function, regulation and also, pharmacological HSC modulation with small molecules from pre-clinical and clinical perspectives.

Cell-intrinsic factors governing quiescence vis-à-vis activation of adult hematopoietic stem cells

Hematopoiesis is a highly complex process, regulated by both intrinsic and extrinsic factors. Often, these two regulatory arms work in tandem to maintain the steady-state condition of hematopoiesis. However, at times, certain intrinsic attributes of hematopoietic stem cells (HSCs) override the external stimuli and dominate the outcome. These could be genetic events like mutations or environmentally induced epigenetic or transcriptomic changes. Since leukemic stem cells (LSCs) share molecular pathways that also regulate normal HSCs, identifying specific, dominantly acting intrinsic factors could help in the development of novel therapeutic approaches. Here we have reviewed such dominantly acting intrinsic factors governing quiescence vis-à-vis activation of the HSCs in the face of external forces acting on them. For brevity, we have restricted our review to the articles dealing with adult HSCs of human and mouse origin that have been published in the last 10 years. Hematopoietic stem cells (HSCs) are closely associated with various stromal cells in their microenvironment and, thus, constantly receive signaling cues from them. The illustration depicts some dominantly acting intrinsic or cell-autonomous factors operative in the HSCs. These fall into various categories, such as epigenetic regulators, transcription factors, cell cycle regulators, tumor suppressor genes, signaling pathways, and metabolic regulators, which counteract the outcome of extrinsic signaling exerted by the HSC niche.

Genetic profiling of human bone marrow mesenchymal stromal cells after in vitro expansion in clinical grade human platelet lysate

Mesenchymal stromal cells (MSCs) are non-hematopoietic cells that have a broad therapeutic potential. To obtain sufficient cells for clinical application, they must be expanded ex vivo. In the initial expansion protocols described, fetal calf serum (FCS) was used as the reference growth supplement, but more recently different groups started to replace FCS with platelet lysate (PL). We investigated in this study the impact of the culture supplement on gene expression of MSCs. Human bone marrow derived MSCs were expanded in vitro in FCS and PL supplemented medium. We found that MSCs expanded in PL-containing medium (PL-MSCs) express typical MSC immunomorphological features and can migrate, as their counterparts expanded in FCS-containing medium, through a layer of endothelial cells in vitro. Additionally, they show an increased proliferation rate compared to MSCs expanded in FCS medium (FCS-MSCs). RNA sequencing performed for MSCs cultured in both types of expansion medium revealed a large impact of the choice of growth supplement on gene expression: 1974 genes were at least twofold up- or downregulated. We focused on impact of genes involved in apoptosis and senescence. Our data showed that PL-MSCs express more anti-apoptotic genes and FCS-MSCs more pro-apoptotic genes. FCS-MSCs showed upregulation of senescence-related genes after four passages whereas this was rarer in PL-MSCs at the same timepoint. Since PL-MSCs show higher proliferation rates and anti-apoptotic gene expression, they might acquire features that predispose them to malignant transformation. We screened 10 MSC samples expanded in PL-based medium for the presence of tumor-associated genetic variants using a 165 gene panel and detected only 21 different genetic variants. According to our analysis, none of these were established pathogenic mutations. Our data show that differences in culture conditions such as growth supplement have a significant impact on the gene expression profile of MSCs and favor the use of PL over FCS for expansion of MSCs.

17β-Estradiol promotes angiogenesis of bone marrow mesenchymal stem cells by upregulating the PI3K-Akt signaling pathway

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The role and mechanism of 17β -estradiol in the regulation of BMSC promoting angiogenesis were analyzed by bioinformatics techniques for the first time.

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Combined with FN1, MCM2, XPO1, NTRK1 and other proteins, 17β-estradiol is able to activate PI3K-Akt, MAPK and other signaling pathways to regulate BMSCs to promote or remodel angiogenesis.

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17β-estradiol upregulates the PI3K-Akt signaling pathway to promote the BMSC angiogenesis process of differentiation.

Objective

Estrogen is an important hormone affecting angiogenesis in women and is important for female physical development. Menopausal women are prone to serious cardiovascular and cerebrovascular diseases when estrogen is significantly reduced. Bone marrow mesenchymal stem cells (BMSC) have potential roles in processes such as angiogenesis and remodeling. This study is to investigate the effect of 17β-estradiol on BMSC angiogenic differentiation and its underlying molecular mechanism, and to provide a basis for the treatment of microvascular diseases.

Methods

Enrichment analysis of apoptosis, migration or angiogenesis processes and molecular mechanisms of BMSC treated with 17β-estradiol was performed to screen core proteins and perform molecular docking validation. Human MSCs were cultured in vitro to examine the effect of 17β-estradiol on BMSC migration or angiogenic differentiation.

Results

17β-estradiol acted on 48 targets of BMSC and was involved in regulating 52 cell migration processes or 17 angiogenesis processes through 66 KEGG pathways such as PI3K-Akt, MAPK, etc. 17β-estradiol bound tightly to 10 core proteins including APP, NTRK1, EGFR, and HSP90AA1. 17β-estradiol promoted cell scratch area closure rate and CD31 expression in BMSCs, downregulated BMSC apoptosis rate, and promoted Akt and p-Akt protein expression in BMSC.

Conclusion

17β-estradiol binds to FN1, MCM2, XPO1, NTRK1 and other proteins to initiate PI3K-Akt, MAPK and other signaling pathways, so as to regulate BMSC to promote or remodel angiogenesis, verifying that 17β-estradiol up-regulates PI3K-Akt signaling pathway to promote BMSC angiogenic differentiation.

Mesenchymal stromal cell-derived extracellular vesicles: novel approach in hematopoietic stem cell transplantation

Bone marrow mesenchymal stromal cells (MSCs) play a crucial role in the regulation of hematopoiesis. These cells affect the process through direct cell–cell contact, as well as releasing various trophic factors and extracellular vehicles (EVs) into the bone marrow microenvironment. MSC-derived EVs (MSC-EVs) are prominent intercellular communication tolls enriched with broad-spectrum bioactive factors such as proteins, cytokines, lipids, miRNAs, and siRNAs. They mimic some effects of MSCs by direct fusion with hematopoietic stem cells (HSC) membranes in the bone marrow (BM), thereby affecting HSC fate. MSC-EVs are attractive scope in cell-free therapy because of their unique capacity to repair BM tissue and regulate proliferation and differentiation of HSCs. These vesicles modulate the immune system responses and inhibit graft-versus-host disease following hematopoietic stem cell transplantation (HSCT). Recent studies have demonstrated that MSC-EVs play an influential role in the BM niches because of their unprecedented capacity to regulate HSC fate. Therefore, the existing paper intends to speculate upon the preconditioned MSC-EVs as a novel approach in HSCT.

New Insights into Hematopoietic Stem Cell Expansion to Stimulate Repopulation of the Adult Blood System for Transplantation

Successful engraftment of hematopoietic stem cells (HSCs) and progenitor cells (HSPCs) may be considered as a basis for the repopulation of the blood cells after transplantation in adults. Therefore, in vivo and ex vivo expansion of HSCs holds great promise for clinical applications. In this review, the mechanisms of HSC expansion will be discussed, considering the previous studies and works of literature. This is aimed to identify the signaling pathways that regulate HSC expansion and improve the application of engraftment in disease management. The following aspects will be included: (i) Stimulation of HSCs growth in vivo through gene regulation and cytokines activation; (ii) direct or indirect induction of HSC expansion by regulating signaling pathways; (iii) addition to assisting cells to help in the proliferation of HSCs; (iv) changing of living environment in the HSCs cultures via adjusting components and forms of cultures; (v) enhancement of HSC expansion by incorporating substances, such as extracellular vesicles (EVs), UM171, among others. In this review, recent new findings that provide us with new insights into HSC expansion methods have been summarized. Furthermore, these findings will also provide more possibilities for the development of some novel strategies for expanding and engrafting HSCs applied for treatments of some hematopoietic disorders.

Mesenchymal stromal cells-derived secretome protects Neuro-2a cells from oxidative stress-induced loss of neurogenesis

Neurodegenerative diseases (ND) are characterized by debilitating medical conditions that principally affect the neuronal cells in the human brain. One of the major reasons that there are no effective drugs for the treatment of ND is because researchers face technical challenges while conducting studies to understand the molecular mechanism behind ND. Although various studies have established in vitro neurodegenerative model systems, we feel that these model systems are not physiologically relevant, as they do not mimic the in vivo situation of chronic insult. Therefore, the primary aim of this study was to establish an in vitro neurodegenerative model system by inducing oxidative stress in such a way that the neuronal cells remain viable, but lose their structural and functional characteristics. Using a murine neuroblastoma cell line, Neuro-2a, we demonstrate that induction of oxidative stress significantly affects various neurite outgrowth parameters and reduces the expression of neuronal and autophagy markers without causing apoptosis in them. Previously, we have discussed the possible therapeutic applications of mesenchymal stromal cells (MSCs) and their secretome in the treatment of ND. Here, using two distinct approaches, we show that when Neuro-2a cells subjected to oxidative stress are exposed to MSC-derived conditioned medium (secretome), they exhibit a significant improvement in various neuronal parameters and in the expression of neuronal markers. Overall, our findings support the salutary role of MSC-derived secretome in rescuing the oxidative stress-induced loss of neurogenesis using a physiologically relevant in vitro model system. Our data underscore the propensity of the MSC-secretome in reversing ND.

The Intercellular Communication Between Mesenchymal Stromal Cells and Hematopoietic Stem Cells Critically Depends on NF-κB Signalling in the Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) regulate the fate of the hematopoietic stem cells (HSCs) through both cell-cell interactions and paracrine mechanisms involving multiple signalling pathways. We have previously shown that co-culturing of HSCs with CoCl₂-treated MSCs expands functional HSCs. While performing these experiments, we had observed that the growth of CoCl₂-treated MSCs was significantly stunted. Here, we show that CoCl₂-treated MSCs possess activated NF-κB signalling pathway, and its pharmacological inhibition significantly relieves their growth arrest. Most interestingly, we found that pharmacological inhibition of NF-κB pathway in both control and CoCl₂-treated MSCs completely blocks their intercellular communication with the co-cultured hematopoietic stem and progenitor cells (HSPCs), resulting in an extremely poor output of hematopoietic cells. Mechanistically, we show that this is due to the down-regulation of adhesion molecules and various HSC-supportive factors in the MSCs. This loss of physical interaction with HSPCs could be partially restored by treating the MSCs with calcium ionophore or calmodulin, suggesting that NF-κB regulates intracellular calcium flux in the MSCs. Importantly, the HSPCs co-cultured with NF-κB-inhibited-MSCs were in a quiescent state, which could be rescued by re-culturing them with untreated MSCs. Our data underscore a critical requirement of NF-κB signalling in the MSCs in intercellular communication between HSCs and MSCs for effective hematopoiesis to occur ex vivo. Our data raises a cautionary note against excessive use of anti-inflammatory drugs targeting NF-κB.

Wharton's jelly-derived stromal cells and their cell therapy applications in allogeneic haematopoietic stem cell transplantation

For decades, mesenchymal stromal cells (MSCs) have been of great interest in the fields of regenerative medicine, tissue engineering and immunomodulation. Their tremendous potential makes it desirable to cryopreserve and bank MSCs to increase their accessibility and availability. Postnatally derived MSCs seem to be of particular interest because they are harvested after delivery without ethical controversy, they have the capacity to expand at a higher rate than adult‐derived MSCs, in which expansion decreases with ageing, and they have demonstrated immunological and haematological supportive properties similar to those of adult‐derived MSCs. In this review, we focus on MSCs obtained from Wharton's jelly (the mucous connective tissue of the umbilical cord between the amniotic epithelium and the umbilical vessels). Wharton's jelly MSCs (WJ‐MSCs) are a good candidate for cellular therapy in haematology, with accumulating data supporting their potential to sustain haematopoietic stem cell engraftment and to modulate alloreactivity such as Graft Versus Host Disease (GVHD). We first present an overview of their in‐vitro properties and the results of preclinical murine models confirming the suitability of WJ‐MSCs for cellular therapy in haematology. Next, we focus on clinical trials and discuss tolerance, efficacy and infusion protocols reported in haematology for GVHD and engraftment.

Pharmacological Inhibition of p38 MAPK Rejuvenates Bone Marrow Derived-Mesenchymal Stromal Cells and Boosts their Hematopoietic Stem Cell-Supportive Ability

The therapeutic value of mesenchymal stromal cells (MSCs) for various regenerative medicine applications, including hematopoietic stem cell transplantations (HSCT), has been well-established. Owing to their small numbers in vivo, it becomes necessary to expand them in vitro, which leads to a gradual loss of their regenerative capacity. Stress-induced mitogen-activated protein kinase p38 (p38 MAPK) signaling has been shown to compromise the MSC functions. Therefore, we investigated whether pharmacological inhibition of p38 MAPK signaling rejuvenates the cultured MSCs and boosts their functionality. Indeed, we found that the ex vivo expanded MSCs show activated p38 MAPK signaling and exhibit increased oxidative stress. These MSCs show a decreased ability to secrete salutary niche factors, thereby compromising their ability to support hematopoietic stem cell (HSC) self-renewal, proliferation, and differentiation. We, therefore, attempted to rejuvenate the cultured MSCs by pharmacological inhibition of p38 MAPK - a strategy broadly known as "priming of MSCs". We demonstrate that priming of MSCs with a p-38 MAPK inhibitor, PD169316, boosts their niche-supportive functions via upregulation of various HSC-supportive transcription factors. These primed MSCs expand multipotent HSCs having superior homing and long-term reconstitution ability. These findings shed light on the significance of non-cell-autonomous mechanisms operative in the hematopoietic niche and point towards the possible use of pharmacological compounds for rejuvenation of ex vivo cultured MSCs. Such approaches could improve the outcome of regenerative therapies involving in vitro cultured MSCs.

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

Extracellular Vesicles of Mesenchymal Stem Cells: Therapeutic Properties Discovered with Extraordinary Success

Mesenchymal stem cells (MSCs), the cells distributed in the stromas of the body, are known for various properties including replication, the potential of various differentiations, the immune-related processes including inflammation. About two decades ago, these cells were shown to play relevant roles in the therapy of numerous diseases, dependent on their immune regulation and their release of cytokines and growth factors, with ensuing activation of favorable enzymes and processes. Such discovery induced great increase of their investigation. Soon thereafter, however, it became clear that therapeutic actions of MSCs are risky, accompanied by serious drawbacks and defects. MSC therapy has been therefore reduced to a few diseases, replaced for the others by their extracellular vesicles, the MSC-EVs. The latter vesicles recapitulate most therapeutic actions of MSCs, with equal or even better efficacies and without the serious drawbacks of the parent cells. In addition, MSC-EVs are characterized by many advantages, among which are their heterogeneities dependent on the stromas of origin, the alleviation of cell aging, the regulation of immune responses and inflammation. Here we illustrate the MSC-EV therapeutic effects, largely mediated by specific miRNAs, covering various diseases and pathological processes occurring in the bones, heart and vessels, kidney, and brain. MSC-EVs operate also on the development of cancers and on COVID-19, where they alleviate the organ lesions induced by the virus. Therapy by MSC-EVs can be improved by combination of their innate potential to engineering processes inducing precise targeting and transfer of drugs. The unique properties of MSC-EVs explain their intense studies, carried out with extraordinary success. Although not yet developed to clinical practice, the perspectives for proximal future are encouraging.

Placenta: A gold mine for translational research and regenerative medicine

Stem cell therapy has gained much impetus in regenerative medicine due to some of the encouraging results obtained in the laboratory as well as in translational/clinical studies. Although stem cells are of various types and their therapeutic potential has been documented in several studies, mesenchymal stromal/stem cells (MSCs) have an edge, as in addition to being multipotent, these cells are easy to obtain and expand, pose fewer ethical issues, and possess immense regenerative potential when used in a scientifically correct manner. Currently, MSCs are being sourced from various tissues such as bone marrow, cord, cord blood, adipose tissue, dental tissue, etc., and, quite often, the choice depends on the availability of the source. One such rich source of tissue suitable for obtaining good quality MSCs in large numbers is the placenta obtained in a full-term delivery leading to a healthy child's birth. Several studies have demonstrated the regenerative potential of human placenta-derived MSCs (hPMSC), and most show that these MSCs possess comparable, in some instances, even better, therapeutic potential as that shown by human bone marrow-derived (hBMSC) or human umbilical cord-derived (hUC-MSC) MSCs. The placenta can be easily sourced from the OB/GYN department of any hospital, and if its derivatives such as hPMSC or their EVs are produced under GMP conditions, it could serve as a gold mine for translational/clinical research. Here, we have reviewed recent studies revealing the therapeutic potential of hPMSC and their extracellular vesicles (EVs) published over the past three years.

Research progress on exosomes derived from mesenchymal stem cells in hematological malignancies

Mesenchymal stem cells (MSCs) are a subset of multifunctional stem cells with self-renewal and multidirectional differentiation properties that play a pivotal role in tumor progression. MSCs are reported to exert biological functions by secreting specialized vesicles, known as exosomes, with tumor cells. Exosomes participate in material and information exchange between cells and are crucial in multiple physiological and pathological processes. This study provides a comprehensive overview of the roles, mechanisms of action and sources of MSC exosomes in hematological malignancies, and different tumor types.

Mesenchymal Stromal Cells in Viral Infections: Implications for COVID-19

Mesenchymal stromal cells (MSCs) constitute a heterogeneous population of stromal cells with immunomodulatory and regenerative properties that support their therapeutic use. MSCs isolated from many tissue sources replicate vigorously in vitro and maintain their main biological properties allowing their widespread clinical application. To date, most MSC-based preclinical and clinical trials targeted immune-mediated and inflammatory diseases. Nevertheless, MSCs have antiviral properties and have been used in the treatment of various viral infections in the last years. Here, we revised in detail the biological properties of MSCs and their preclinical and clinical applications in viral diseases, including the disease caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection (COVID-19). Notably, rapidly increasing numbers of MSC-based therapies for COVID-19 have recently been reported. MSCs are theoretically capable of reducing inflammation and promote lung regeneration in severe COVID-19 patients. We critically discuss the rationale, advantages and disadvantages of MSC-based therapies for viral infections and also specifically for COVID-19 and point out some directions in this field. Finally, we argue that MSC-based therapy may be a promising therapeutic strategy for severe COVID-19 and other emergent respiratory tract viral infections, beyond the viral infection diseases in which MSCs have already been clinically applied.

The Potential of Mesenchymal Stromal Cells in Neuroblastoma Therapy for Delivery of Anti-Cancer Agents and Hematopoietic Recovery

Neuroblastoma is one of the most common pediatric cancers and a major cause of cancer-related death in infancy. Conventional therapies including high-dose chemotherapy, stem cell transplantation, and immunotherapy approach a limit in the treatment of high-risk neuroblastoma and prevention of relapse. In the last two decades, research unraveled a potential use of mesenchymal stromal cells in tumor therapy, as tumor-selective delivery vehicles for therapeutic compounds and oncolytic viruses and by means of supporting hematopoietic stem cell transplantation. Based on pre-clinical and clinical advances in neuroblastoma and other malignancies, we assess both the strong potential and the associated risks of using mesenchymal stromal cells in the therapy for neuroblastoma. Furthermore, we examine feasibility and safety aspects and discuss future directions for harnessing the advantageous properties of mesenchymal stromal cells for the advancement of therapy success.

Cryopreservation of mesenchymal stromal cell-derived extracellular vesicles using trehalose maintains their ability to expand hematopoietic stem cells in vitro

The multitude of clinical trials using mesenchymal stromal cells (MSCs) has underscored their significance as a promising cell source for regenerative therapies. Most studies have however shown that MSCs get entrapped into the microvasculature of lungs, liver and spleen. In addition to intercellular communication, MSCs exert their effects in a paracrine manner by secretion of extracellular vesicles (EVs). The therapeutic effects of MSC-derived EVs have been examined in several diseases such as hepatic failure, liver injury, hematopoiesis etc. Therefore, optimization of cryopreservation strategies for the long-term storage of functional EVs could help in the development of off-the-shelf biologics. The aim of this study was to develop an optimal cryopreservation strategy for the efficient storage of both types of EVs - Microvesicles (MVs) and exosomes, independently, and to further examine the effect of the cryopreserved EVs on the ex vivo expansion of HSCs. MVs and exosomes were separately cryopreserved at different temperatures using PBS or PBS supplemented with trehalose (pTRE), and these cryopreserved EVs were then assessed for their functionality after revival. We found that addition of trehalose during cryopreservation helped in maintaining the morphology and functionality of the EVs, as assessed by their HSC-supportive potential, ability to expand phenotypically defined HSCs and ability to maintain the chemotactic migration potential of the HSCs co-cultured with them. This strategy could prove to be beneficial for facilitating the use of EVs as cell-free ready-to-use biologics for the ex vivo expansion of HSCs and in regenerative medicine.

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.

Effect of Aging and 5-Fluorouracil Treatment on Bone Marrow Stem Cell Dynamics

Lifelong homeostasis of bone marrow is maintained by the resident stem cells that include the quiescent very small embryonic-like stem cells (VSELs) and lineage restricted, tissue committed 'progenitors' hematopoietic stem cells (HSCs). Niche providing mesenchymal stromal cells (MSCs) regulate the function of VSELs/HSCs by providing crucial paracrine support. Any dysfunction of stem cells and/or their niche leads to disease state. The stem cells biology gets affected with age leading to a myeloid bias in differentiation of HSCs and increased incidence of myeloid leukemia. Present study was undertaken to enumerate VSELs, HSCs and MSCs and evaluate their response on D4 and D10 after chemotherapy with 5-Fluorouracil (5-FU) in young and aged mouse bone marrow. Stem cells were activated in response to 5-FU induced stress in an attempt to restore homeostasis. Although absolute numbers of VSELs and HSCs did not differ much between young and aged mice, their tendency to proliferate was higher on D4 in aged mice. However, ability to revert back to basal numbers and their differentiation was affected on D10 in aged marrow. Stem cells from aged bone marrow showed greater ability to form CFUs on D10 after 5-FU treatment. CD44 positive aged MSCs also showed increased proliferation on D10. Transplanting MSCs from young mice in 5-FU treated aged marrow helped improve hematopoiesis. The results suggest that no significant intrinsic changes occur as proliferative ability of stem cells remains unaffected but the niche gets affected with age leading to excessive self-renewal and compromised differentiation. This may explain increased incidence of leukemia with age.