Mesenchymal stem/stromal cell extracellular vesicles: From active principle to next generation drug delivery system

Stem Cell-Engineered Nanovesicles Exert Proangiogenic and Neuroprotective Effects

As a tissue regeneration strategy, the utilization of mesenchymal stem cells (MSCs) has drawn considerable attention. Comprehensive research using MSCs has led to significant preclinical or clinical outcomes; however, improving the survival rate, engraftment efficacy, and immunogenicity of implanted MSCs remains challenging. Although MSC-derived exosomes were recently introduced and reported to have great potential to replace conventional MSC-based therapeutics, the poor production yield and heterogeneity of exosomes are critical hurdles for their further applications. Herein, we report the fabrication of exosome-mimetic MSC-engineered nanovesicles (MSC-NVs) by subjecting cells to serial extrusion through filters. The fabricated MSC-NVs exhibit a hydrodynamic size of ~120 nm, which is considerably smaller than the size of MSCs (~30 μm). MSC-NVs contain both MSC markers and exosome markers. Importantly, various therapeutic growth factors originating from parent MSCs are encapsulated in the MSC-NVs. The MSC-NVs exerted various therapeutic effects comparable to those of MSCs. They also significantly induced the angiogenesis of endothelial cells and showed neuroprotective effects in damaged neuronal cells. The results collectively demonstrate that the fabricated MSC-NVs can serve as a nanosized therapeutic agent for tissue regeneration.

The Benefits and Hazards of Intravitreal Mesenchymal Stem Cell (MSC) Based-Therapies in the Experimental Ischemic Optic Neuropathy

Mesenchymal stem cell (MSC) therapy has been investigated intensively for many years. However, there is a potential risk related to MSC applications in various cell niches. Methods: The safety of intravitreal MSC application and the efficacy of MSC-derived conditioned medium (MDCM) were evaluated in the normal eye and the diseased eye, respectively. For safety evaluation, the fundus morphology, visual function, retinal function, and histological changes of the retina were examined. For efficacy evaluation, the MDCM was intravitreally administrated in a rodent model of anterior ischemic optic neuropathy (rAION). The visual function, retinal ganglion cell (RGC) density, and neuroinflammation were evaluated at day 28 post-optic nerve (ON) infarct. Results: The fundus imaging showed that MSC transplantation induced retinal distortion and venous congestion. The visual function, retinal function, and RGC density were significantly decreased in MSC-treated eyes. MSC transplantation induced astrogliosis, microgliosis, and macrophage infiltration in the retina due to an increase in the HLA-DR-positive MSC proportion in vitreous. Treatment with the MDCM preserved the visual function and RGC density in rAION via inhibition of macrophage infiltration and RGC apoptosis. Conclusions: The vitreous induced the HLA-DR expression in the MSCs to cause retinal inflammation and retina injury. However, the MDCM provided the neuroprotective effects in rAION.

Extracellular Vesicle (EV) biohybrid systems for cancer therapy: Recent advances and future perspectives

Extracellular vesicles (EVs) are a class of cell-derived lipid-bilayer membrane vesicles secreted by almost all mammalian cells and involved in intercellular communication by shuttling various biological cargoes. Over the last decade, EVs - namely exosomes and microvesicles - have been extensively explored as next-generation nanoscale drug delivery systems (DDSs). This is in large due to their endogenous origin, which enables EVs to circumvent some of the limitations associated with existing cancer therapy approaches (i.e. by preventing recognition by the immune system and improving selectivity towards tumor tissue). However, successful translation of these cell-derived vesicles into clinical applications has been hindered by several factors, among which the loading of exogenous therapeutic molecules still represents a great challenge. In order to address this issue and to further advance these biologically-derived systems as drug carriers, EV-biohybrid nano-DDSs, obtained through the fusion of EVs with conventional synthetic nano-DDSs, have recently been proposed as a valuable alternative as DDSs. Building on the idea of "combining the best of both worlds", a combination of these two unique entities aims to harness the beneficial properties associated with both EVs and conventional nano-DDSs, while overcoming the flaws of the individual components. These biohybrid systems also provide a unique opportunity for exploitation of new synergisms, often leading to improved therapeutic outcomes, thus paving the way for advancements in cancer therapy. This review aims to describe the recent developments of EV-biohybrid nano-DDSs in cancer therapy, to highlight the most promising results and breakthroughs, as well as to provide a glimpse on the possible intrinsic targeting mechanisms of EVs that can be bequeathed to their hybrid systems. Finally, we also provide some insights in the future perspectives of EV-hybrid DDSs.

Therapeutic Effects of Conditioned Medium of Neural Differentiated Human Bone Marrow-Derived Stem Cells on Rotenone-Induced Alpha-Synuclein Aggregation and Apoptosis

Mesenchymal stem cells (MSCs) have been used against several diseases. Their potential mainly appears from its secreted biomolecules. Human bone marrow-derived stem cells (hBMSC) displayed neuronal functional characteristics after differentiation by basic fibroblast growth factor (bFGF) and forskolin. PD is a chronic age-related neurodegenerative disease (NDD) characterized by loss of dopaminergic neurons in the substantia nigra (SN) and abnormal accumulation of α-synuclein (α-syn) aggregations. In this present study, we evaluated the therapeutic effects of neural differentiated hBMSC (NI-hBMSC) conditioned medium (NI-hBMSC-CM) to a rotenone- (ROT-) induced Parkinson's disease (PD) model in SH-SY5Y cells. NI-hBMSC-CM treatment (50% diluted) in the last 24 h of 48 h ROT (0.5 μM) toxicity showed a significant increase in cell survival. The decreased tyrosine hydroxylase (TH) expression as a hallmark of PD was increased by NI-hBMSC-CM. The Triton X-100-soluble and Triton X-100-insoluble cell lysate fractions were used in Western blotting. The oligomeric, dimeric, and monomeric phosphorylated serine129 (p-S129) α-syn and total monomeric α-syn were decreased during ROT toxicity in the Triton X-100-soluble fraction. The Triton X-100-insoluble fraction revealed that ROT toxicity significantly increased the oligomeric but decreased the dimeric and monomeric p-S129 α-syn expressions while all forms of total α-syn were increased in SH-SY5Y cells. NI-hBMSC-CM stabilized the physiological α-syn monomers and reduced aggregated insoluble p-S129 α-syn against ROT. The cytoskeletal proteins, neurofilament-H (NF-H), β3-tubulin (Tuj1), neuronal nuclei (NeuN), and synaptophysin (SYP) were significantly decreased during ROT toxicity. In addition, proapoptotic Bax was increased by ROT with decreased antiapoptotic Bcl-2 and Mcl-1 as well as proforms of caspase-9, caspase-3, caspase-7, and PARP-1. NI-hBMSC-CM ameliorated the neurotrophic protein expressions, controlled the Bax/Bcl-2 ratio, upregulated procaspases, and inactivated PARP-1. From our results, we conclude that NI-hBMSC-CM containing released biomolecules during neural differentiation employs regenerative effects on the ROT model of PD in SH-SY5Y cells.

Mesenchymal stem cell (MSC)-derived exosomes as a cell-free therapy for patients Infected with COVID-19: Real opportunities and range of promises

There are no commercially available effective antiviral medications or vaccines to deal with novel coronavirus disease (COVID-19). Hence there is a substantial unmet medical need for new and efficacious treatment options for COVID-19. Most COVID-19 deaths result from acute respiratory distress syndrome (ARDS). This virus induces excessive and aberrant inflammation so it is important to control the inflammation as soon as possible. To date, results of numerous studies have been shown that mesenchymal stem cells and their derivatives can suppress inflammation. Exosomes function as intercellular communication vehicles to transfer bioactive molecules (based on their origins), between cells. In this review, the recent exosome-based clinical trials for the treatment of COVID-19 are presented. Potential therapy may include the following items: First, using mesenchymal stem cells secretome. Second, incorporating specific miRNAs and mRNAs into exosomes and last, using exosomes as carriers to deliver drugs.

The Functional Heterogeneity of Neutrophil-Derived Extracellular Vesicles Reflects the Status of the Parent Cell

Similar to other cell types, neutrophilic granulocytes also release extracellular vesicles (EVs), mainly medium-sized microvesicles/microparticles. According to published data, authors have reached a consensus on the physical parameters (size, density) and chemical composition (surface proteins, proteomics) of neutrophil-derived EVs. In contrast, there is large diversity and even controversy in the reported functional properties. Part of the discrepancy may be ascribed to differences in the viability of the starting cells, in eliciting factors, in separation techniques and in storage conditions. However, the most recent data from our laboratory prove that the same population of neutrophils is able to generate EVs with different functional properties, transmitting pro-inflammatory or anti-inflammatory effects on neighboring cells. Previously we have shown that Mac-1 integrin is a key factor that switches anti-inflammatory EV generation into pro-inflammatory and antibacterial EV production. This paper reviews current knowledge on the functional alterations initiated by neutrophil-derived EVs, listing their effects according to the triggering agents and target cells. We summarize the presence of neutrophil-derived EVs in pathological processes and their perspectives in diagnostics and therapy. Finally, the functional heterogeneity of differently triggered EVs indicates that neutrophils are capable of producing a broad spectrum of EVs, depending on the environmental conditions prevailing at the time of EV genesis.

Feasibility of Mesenchymal Stem Cell Therapy for COVID-19: A Mini Review

Patients infected with SARS-CoV-2 carry the coronavirus disease 2019 (COVID-19) which involves multiple systems and organs with acute respiratory distress syndrome (ARDS) as the most common complication, largely due to cytokine storms or dysregulated immunity. As such, there are many severe patients with complications such as cytokine storm syndrome (CSS), who have a high fatality rate. Neither specific anti-SARS-CoV-2 drugs nor vaccines exist currently. Current treatment relies mainly on self-recovery through patients' immune function. Mesenchymal stem cells (MSCs) is a kind of multipotent tissue stem cells, which have powerful anti-inflammatory and immune regulatory functions, inhibiting the cytokine storms. In addition, MSCs have a strong ability to repair tissue damage and reduce the risk of severe complications such as acute lung injury and ARDS, and hopefully, reduce the fatality rate in these patients. There are several clinical types of research completed for treating COVID-19 with MSCs, all reporting restoration of T cells and clinical safety. Here we discuss the clinical prospect and conclude the therapeutic effects and potential mechanism for MSCs in treating COVID-19.

Clinical Applications of Mesenchymal Stem/Stromal Cell Derived Extracellular Vesicles: Therapeutic Potential of an Acellular Product

In the last decade, the secreting activity of mesenchymal stem/stromal cells (MSCs) has been widely investigated, due to its possible therapeutic role. In fact, MSCs release extracellular vesicles (EVs) containing relevant biomolecules such as mRNAs, microRNAs, bioactive lipids, and signaling receptors, able to restore physiological conditions where regenerative or anti-inflammatory actions are needed. An actual advantage would come from the therapeutic use of EVs with respect to MSCs, avoiding the possible immune rejection, the lung entrapment, improving the safety, and allowing the crossing of biological barriers. A number of concerns still have to be solved regarding the mechanisms determining the beneficial effect of MSC-EVs, the possible alteration of their properties as a consequence of the isolation/purification methods, and/or the best approach for a large-scale production for clinical use. Most of the preclinical studies have been successful, reporting for MSC-EVs a protecting role in acute kidney injury following ischemia reperfusion, a potent anti-inflammatory and anti-fibrotic effects by reducing disease associated inflammation and fibrosis in lung and liver, and the modulation of both innate and adaptive immune responses in graft versus host disease (GVHD) as well as autoimmune diseases. However, the translation of MSC-EVs to the clinical stage is still at the initial phase. Herein, we discuss the therapeutic potential of an acellular product such as MSC derived EVs (MSC-EVs) in acute and chronic pathologies.

Paclitaxel Priming of TRAIL Expressing Mesenchymal Stromal Cells (MSCs-TRAIL) Increases Antitumor Efficacy of Their Secretome

BACKGROUND

Adipose tissue derived MSCs engineered with the tumor necrosis factor-related apoptosis-inducing ligand protein (MSCs-TRAIL) have a significant anticancer activity. MSCs, without any genetic modifications, exposed to high doses of chemotherapeutic agents are able to uptake the drug and release it in amount affecting tumor proliferation. The purpose of this study was to verify the ability of MSCs-TRAIL to uptake and release paclitaxel (PTX) by providing an increased antitumor efficacy.

METHODS

MSCs and MSCs-TRAIL were tested for their sensitivity to Paclitaxel (PTX) by MTT assay and the cells were loaded with PTX according to a standardized procedure. The secretome was analysed by HPLC for the presence of PTX, microarray assay for soluble TRAIL (s-TRAIL) and tested for in vitro anticancer activity.

RESULTS

MSCs-TRAIL were resistant to PTX and able to incorporate and then release the drug. The secretion of s-TRAIL by PTX loaded MSCs-TRAIL was not inhibited and the PTX delivery together with s-TRAIL secretion resulted into an increased antitumor efficacy of cell secretoma as tested in vitro on human pancreatic carcinoma (CFPAC-1) and glioblastoma (U87-MG).

CONCLUSIONS

Our result is the first demonstration of the possible merging of two new MSCs therapy approaches based on genetic manipulation and drug delivery. If confirmed in vivo, this could potentiate the efficacy of MSCs-TRAIL and strongly contribute to reduce the toxicity due to the systemic treatment of PTX.

Long noncoding RNA repressor of adipogenesis negatively regulates the adipogenic differentiation of mesenchymal stem cells through the hnRNP A1-PTX3-ERK axis

BACKGROUND

Mesenchymal stem cells (MSCs) are pluripotent stem cells that can differentiate via osteogenesis and adipogenesis. The mechanism underlying MSC lineage commitment still remains incompletely elucidated. Understanding the regulatory mechanism of MSC differentiation will help researchers induce MSCs toward specific lineages for clinical use. In this research, we intended to figure out the long noncoding RNA (lncRNA) that plays a central role in MSC fate determination and explore its application value in tissue engineering.

METHODS

The expression pattern of lncRNAs during MSC osteogenesis/adipogenesis was detected by microarray and qRT-PCR. Lentivirus and siRNAs were constructed to regulate the expression of lncRNA repressor of adipogenesis (ROA). MSC osteogenesis/adipogenesis was evaluated by western blot and alizarin red/oil red staining. An adipokine array was used to select the paracrine/autocrine factor PTX3, followed by RNA interference or recombinant human protein stimulation to confirm its function. The activation of signaling pathways was also detected by western blot, and a small molecule inhibitor, SCH772984, was used to inhibit the activation of the ERK pathway. The interaction between ROA and hnRNP A1 was detected by RNA pull-down and RIP assays. Luciferase reporter and chromatin immunoprecipitation assays were used to confirm the binding of hnRNP A1 to the PTX3 promotor. Additionally, an in vivo adipogenesis experiment was conducted to evaluate the regulatory value of ROA in tissue engineering.

RESULTS

In this study, we demonstrated that MSC adipogenesis is regulated by lncRNA ROA both in vitro and in vivo. Mechanistically, ROA inhibits MSC adipogenesis by downregulating the expression of the key autocrine/paracrine factor PTX3 and the downstream ERK pathway. This downregulation was achieved through transcription inhibition by impeding hnRNP A1 from binding to the promoter of PTX3.

CONCLUSIONS

ROA negatively regulates MSC adipogenesis through the hnRNP A1-PTX3-ERK axis. ROA may be an effective target for modulating MSCs in tissue engineering.

Cross talk between mesenchymal and glioblastoma stem cells: Communication beyond controversies

Mesenchymal stem cells (MSCs) can be isolated from bone marrow or other adult tissues (adipose tissue, dental pulp, amniotic fluid, and umbilical cord). In vitro, MSCs grow as adherent cells, display fibroblast-like morphology, and self-renew, undergoing specific mesodermal differentiation. High heterogeneity of MSCs from different origin, and differences in preparation techniques, make difficult to uniform their functional properties for therapeutic purposes. Immunomodulatory, migratory, and differentiation ability, fueled clinical MSC application in regenerative medicine, whereas beneficial effects are currently mainly ascribed to their secretome and extracellular vesicles. MSC translational potential in cancer therapy exploits putative anti-tumor activity and inherent tropism toward tumor sites to deliver cytotoxic drugs. However, controversial results emerged evaluating either the therapeutic potential or homing efficiency of MSCs, as both antitumor and protumor effects were reported. Glioblastoma (GBM) is the most malignant brain tumor and its development and aggressive nature is sustained by cancer stem cells (CSCs) and the identification of effective therapeutic is required. MSC dualistic action, tumor-promoting or tumor-targeting, is dependent on secreted factors and extracellular vesicles driving a complex cross talk between MSCs and GBM CSCs. Tumor-tropic ability of MSCs, besides providing an alternative therapeutic approach, could represent a tool to understand the biology of GBM CSCs and related paracrine mechanisms, underpinning MSC-GBM interactions. In this review, recent findings on the complex nature of MSCs will be highlighted, focusing on their elusive impact on GBM progression and aggressiveness by direct cell-cell interaction and via secretome, also facing the perspectives and challenges in treatment strategies.

Role of the CXCR4-SDF1-HMGB1 pathway in the directional migration of cells and regeneration of affected organs

In recent years, several studies have reported positive outcomes of cell-based therapies despite insufficient engraftment of transplanted cells. These findings have created a huge interest in the regenerative potential of paracrine factors released from transplanted stem or progenitor cells. Interestingly, this notion has also led scientists to question the role of proteins in the secretome produced by cells, tissues or organisms under certain conditions or at a particular time of regenerative therapy. Further studies have revealed that the secretomes derived from different cell types contain paracrine factors that could help to prevent apoptosis and induce proliferation of cells residing within the tissues of affected organs. This could also facilitate the migration of immune, progenitor and stem cells within the body to the site of inflammation. Of these different paracrine factors present within the secretome, researchers have given proper consideration to stromal cell-derived factor-1 (SDF1) that plays a vital role in tissue-specific migration of the cells needed for regeneration. Recently researchers recognized that SDF1 could facilitate site-specific migration of cells by regulating SDF1-CXCR4 and/or HMGB1-SDF1-CXCR4 pathways which is vital for tissue regeneration. Hence in this study, we have attempted to describe the role of different types of cells within the body in facilitating regeneration while emphasizing the HMGB1-SDF1-CXCR4 pathway that orchestrates the migration of cells to the site where regeneration is needed.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: Opportunities and Challenges for Clinical Translation

Extracellular vesicles (EVs), including exosomes and microvesicles, derived from mesenchymal stem/stromal cells (MSCs) exert similar effects as their parental cells, and are of interest for various therapeutic applications. EVs can act through uptake by the target cells followed by release of their cargo inside the cytoplasm, or through interaction of membrane-bound ligands with receptors expressed on target cells to stimulate downstream intracellular pathways. EV-based therapeutics may be directly used as substitutes of intact cells or after modification for targeted drug delivery. However, for the development of EV-based therapeutics, several production, isolation, and characterization requirements have to be met and the quality of the final product has to be tested before its clinical implementation. In this review, we discuss the challenges associated with the development of EV-based therapeutics and the regulatory specifications for their successful clinical translation.

Assessment of extracellular vesicles using IFC for application in transfusion medicine

Extracellular vesicles (EVs) have been shown to be involved in various physiological and pathophysiological processes. With respect to Transfusion Medicine, the accumulation of EVs in blood products during hypothermic storage is an indicator of the storage lesion and reportedly correlates with adverse effects after transfusion, including but not limited to immunomodulation, activation of coagulation, endothelial activation, and others. To optimally reduce such an impact on blood product quality degradation and improve post-transfusion outcomes, better methods for detection, enumeration, characterisation by size and phenotype, and functional involvement of EVs in different pathophysiological and physiological processes are required. Currently, Imaging Flow Cytometry (IFC) technology provides the most comprehensive assessment of EV subsets in different body fluids. The unique ability of IFC to detect EVs of 20 nm size by registration of a single pixel of fluorescence signal makes this approach highly promising for comprehensive studies of EVs. In this review, we will focus on the recent breakthrough and advantages of using the ImageStream^X MKII IFC platform for the detection and characterisation of EVs and its future prospects for routine application of IFC in Transfusion Medicine.

Immunomodulatory effect of mesenchymal stem cells and mesenchymal stem-cell-derived exosomes for COVID-19 treatment

The world has witnessed unimaginable damage from the coronavirus disease-19 (COVID-19) pandemic. Because the pandemic is growing rapidly, it is important to consider diverse treatment options to effectively treat people worldwide. Since the immune system is at the hub of the infection, it is essential to regulate the dynamic balance in order to prevent the overexaggerated immune responses that subsequently result in multiorgan damage. The use of stem cells as treatment options has gained tremend-ous momentum in the past decade. The revolutionary mea-sures in science have brought to the world mesenchymal stem cells (MSCs) and MSC-derived exosomes (MSC-Exo) as thera-peutic opportunities for various diseases. The MSCs and MSC-Exos have immunomodulatory functions; they can be used as therapy to strike a balance in the immune cells of patients with COVID-19. In this review, we discuss the basics of the cyto-kine storm in COVID-19, MSCs, and MSC-derived exosomes and the potential and stem-cell-based ongoing clinical trials for COVID-19.

The Delivery of Extracellular Vesicles Loaded in Biomaterial Scaffolds for Bone Regeneration

Extracellular vesicles (EVs) are heterogeneous nanoparticles actively released by cells that comprise highly conserved and efficient systems of intercellular communication. In recent years, numerous studies have proven that EVs play an important role in the field of bone tissue engineering (BTE) due to several advantages, such as good biosafety, stability and efficient delivery. However, the application of EVs therapies in bone regeneration has not been widely used. One of the major challenges for the application of EVs is the lack of sufficient scaffolds to load and control the release of EVs. Thus, in this review, we describe the most advanced current strategies for delivering EVs with various biomaterials for the use in bone regeneration, the role of EVs in bone regeneration, the distribution of EVs mediated by biomaterials and common methods of promoting EVs delivery efficacy with a focus on biomaterial properties.

MSC-derived exosomes protect against oxidative stress-induced skin injury via adaptive regulation of the NRF2 defense system

Oxidative stress is a major cause of skin injury induced by damaging stimuli such as UV radiation. Currently, owing to their immunomodulatory properties, mesenchymal stem cell-derived exosomes (MSC-Exo), as a nanotherapeutic agent, have attracted considerable attention. Here, we investigated the therapeutic effects of MSC-Exo on oxidative injury in H₂O₂-stimulated epidermal keratinocytes and UV-irradiated wild type and nuclear factor-erythroid 2-related factor-2 (Nrf2) knocked down cell and animal models. Our findings showed that MSC-Exo treatment reduced reactive oxygen species generation, DNA damage, aberrant calcium signaling, and mitochondrial changes in H₂O₂-stimulated keratinocytes or UV-irradiated mice skin. Exosome therapy also improved antioxidant capacities shown by increased ferric ion reducing antioxidant power and glutathione peroxidase or superoxide dismutase activities in oxidative stress-induced cell and skin injury. In addition, it alleviated cellular and histological responses to inflammation and oxidation in cell or animal models. Furthermore, the NRF2 signaling pathway was involved in the antioxidation activity of MSC-Exo, while Nrf2 knockdown attenuated the antioxidant capacities of MSC-Exo in vitro and in vivo, suggesting that these effects are partially mediated by the NRF2 signaling pathway. These results indicate that MSC-Exo can repair oxidative stress-induced skin injury via adaptive regulation of the NRF2 defense system. Thus, MSC-Exo may be used as a potential dermatological nanotherapeutic agent for treating oxidative stress-induced skin diseases or disorders.

Extracellular vesicles carrying miR-193a derived from mesenchymal stem cells impede cell proliferation, migration and invasion of colon cancer by downregulating FAK

MicroRNA (miR) deregulation is frequently seen in colon cancer. In this study, we sought to investigate biological effects of miR-193a on colon cancer and its underlying mechanism. Microarray analysis was conducted to obtain the differentially expressed miRs and their target genes in colon cancer. Bone-marrow derived mesenchymal stem cells (MSCs) and extracellular vesicles (EVs) were obtained. The functional roles of miR-193a and FAK in colon cancer were determined using loss- and gain-function experiments. The cell proliferation, and migration and invasion were evaluated by CCK-8 and Transwell assay respectively. Dual-luciferase reporter assay was performed to confirm the targeting relationship between miR-193a and FAK. Furthermore, in vivo experiment was conducted to test the roles of EV miR-193a in colon cancer growth, followed by determination of PCNA, MMP-2, and MMP-9 protein expression using Western blot analysis. MiR-193a was downregulated, whereas FAK was upregulated in colon cancer. MiR-193a upregulation or FAK downregulation inhibited proliferation, migration and invasion of colon cancer cells. miR-193a could downregulate FAK. Upregulation of EV miR-193a was observed to impede proliferation, migration and invasion of colon cancer cells in vitro and in vivo, accompanied by decreased PCNA, MMP-2, and MMP-9 expression. In summary, EV miR-193a derived from MSCs impeded colon cancer progression by targeting FAK, thus suggesting a new potential strategy for colon cancer treatment.

Veterinary Regenerative Medicine for Musculoskeletal Disorders: Can Mesenchymal Stem/Stromal Cells and Their Secretome Be the New Frontier?

Regenerative medicine aims to restore the normal function of diseased or damaged cells, tissues, and organs using a set of different approaches, including cell-based therapies. In the veterinary field, regenerative medicine is strongly related to the use of mesenchymal stromal cells (MSCs), which belong to the body repair system and are defined as multipotent progenitor cells, able to self-replicate and to differentiate into different cell types. This review aims to take stock of what is known about the MSCs and their use in the veterinary medicine focusing on clinical reports on dogs and horses in musculoskeletal diseases, a research field extensively reported in the literature data. Finally, a perspective regarding the use of the secretome and/or extracellular vesicles (EVs) in the veterinary field to replace parental MSCs is provided. The pharmaceuticalization of EVs is wished due to the realization of a Good Manufacturing Practice (GMP product suitable for clinical trials.

Adipose-Derived Stem Cells Primed with Paclitaxel Inhibit Ovarian Cancer Spheroid Growth and Overcome Paclitaxel Resistance

Adipose-derived stem cells (ADSCs) primed with paclitaxel (PTX) are now hypothesized to represent a potential Trojan horse to vehicle and deliver PTX into tumors. We analyzed the anticancer activity of PTX released by ADSCs primed with PTX (PTX-ADSCs) (~20 ng/mL) in a panel of ovarian cancer (OvCa) cells sensitive or resistant to PTX. We used two (2D) and three dimensional (3D) in vitro models (multicellular tumor spheroids, MCTSs, and heterospheroids) to mimic tumor growth in ascites. The coculture of OvCa cells with PTX-ADSCs inhibited cell viability in 2D models and in 3D heterospheroids (SKOV3-MCTSs plus PTX-ADSCs) and counteracted PTX-resistance in Kuramochi cells. The cytotoxic effects of free PTX and of equivalent amounts of PTX secreted in PTX-ADSC-conditioned medium (CM) were compared. PTX-ADSC-CM decreased OvCa cell proliferation, was more active than free PTX and counteracted PTX-resistance in Kuramochi cells (6.0-fold decrease in the IC50 values). Cells cultivated as 3D aggregated MCTSs were more resistant to PTX than 2D cultivation. PTX-ADSC-CM (equivalent-PTX) was more active than PTX in MCTSs and counteracted PTX-resistance in all cell lines. PTX-ADSC-CM also inhibited OvCa-MCTS dissemination on collagen-coated wells. In conclusion, PTX-ADSCs and PTX-MSCs-CM may represent a new option with which to overcome PTX-resistance in OvCa.

Mesenchymal Stromal Cell Secretome for Severe COVID-19 Infections: Premises for the Therapeutic Use

From the end of 2019, the world population has been faced the spread of the novel coronavirus SARS-CoV-2 responsible for COVID-19 infection. In approximately 14% of the patients affected by the novel coronavirus, the infection progresses with the development of pneumonia that requires mechanical ventilation. At the moment, there is no specific antiviral treatment recommended for the COVID-19 pandemic and the therapeutic strategies to deal with the infection are only supportive. In our opinion, mesenchymal stem cell secretome could offer a new therapeutic approach in treating COVID-19 pneumonia, due to the broad pharmacological effects it shows, including anti-inflammatory, immunomodulatory, regenerative, pro-angiogenic and anti-fibrotic properties.

Mesenchymal stem cells induced regulatory dendritic cells from hemopoietic progenitor cells through Notch pathway and TGF-β synergistically

Mesenchymal stem cells (MSCs) are one of the attractive candidates in regenerative medicine of many clinical applications because of their low immunogenicity and immunomodulatory property. Our previous studies provided that mouse bone marrow-derived Sca-1⁺MSCs could drive the differentiation of regulatory DC (regDCs) (Scal-1⁺ BM-MSC-driven DC [sBM-DCs]) from hemopoietic progenitor cells (HPCs) and the Notch pathway played a critical role in maintaining the immunomodulatory property. However, the detailed mechanisms of their immunoregulatory capacity are not fully defined. In the present study, we show that BM-MSCs expressed high levels of Jagged 1 while sBM-DCs expressed high levels of Notch1. Jagged1 expressed on the surface of BM-MSCs initiated Notch signaling to maintain the immunomodulatory property of the sBM-DCs. The level of TGF-β is high in MSCs, either alone or coculture with HPCs medium. TGF-β plays a vital role in the proliferation and differentiation of sBM-DCs and inhibition of TGF-β reduce the number and increase the percentage of CD34, CD117, CD135 of generation cells. Thus, MSCs induced the regDCs from HPCs via the Notch signaling pathway and TGF-β synergistically. This study further broadens our understanding of the immunomodulatory mechanism and the potential therapeutic efficacy of MSCs.

Regeneration-Related Functional Cargoes in Mesenchymal Stem Cell-Derived Small Extracellular Vesicles

Mesenchymal stem cell-derived small extracellular vesicles (MSC-sEV) are the primary effective source in stem cell-dependent regenerative medicine due to their preponderances over direct MSC implantation. An increasing number of studies have been carried out on MSC-sEV derived from different types of cells, and their function of accelerating tissue repair was proved. However, only a few researches were able to demonstrate the functional cargoes in MSC-sEV or their mechanisms in promoting tissue recovery. In this review, we present current achievements in discovering MSC-sEV-carried RNAs and proteins as promoters in tissue regeneration. Their therapeutic function includes modulating immune reactivity, promoting angiogenesis, and accelerating cell proliferation and migration through orchestrates of cell signaling pathways.

Extracellular vesicles derived from human Wharton's jelly mesenchymal stem cells protect hippocampal neurons from oxidative stress and synapse damage induced by amyloid-β oligomers

Background

Mesenchymal stem cells (MSCs) have been explored as promising tools for treatment of several neurological and neurodegenerative diseases. MSCs release abundant extracellular vesicles (EVs) containing a variety of biomolecules, including mRNAs, miRNAs, and proteins. We hypothesized that EVs derived from human Wharton’s jelly would act as mediators of the communication between hMSCs and neurons and could protect hippocampal neurons from damage induced by Alzheimer’s disease-linked amyloid beta oligomers (AβOs).

Methods

We isolated and characterized EVs released by human Wharton’s jelly mesenchymal stem cells (hMSC-EVs). The neuroprotective action of hMSC-EVs was investigated in primary hippocampal cultures exposed to AβOs.

Results

hMSC-EVs were internalized by hippocampal cells in culture, and this was enhanced in the presence of AβOs in the medium. hMSC-EVs protected hippocampal neurons from oxidative stress and synapse damage induced by AβOs. Neuroprotection by hMSC-EVs was mediated by catalase and was abolished in the presence of the catalase inhibitor, aminotriazole.

Conclusions

hMSC-EVs protected hippocampal neurons from damage induced by AβOs, and this was related to the transfer of enzymatically active catalase contained in EVs. Results suggest that hMSC-EVs should be further explored as a cell-free therapeutic approach to prevent neuronal damage in Alzheimer’s disease.

Silencing of GFP expression in human mesenchymal stem cells using quaternary polyplexes of siRNA-PEI with glycosaminoglycans and albumin

In recent years evidence has been mounting for a role for mesenchymal stem cells (MSCs) in immunomodulation, anti-inflammatory processes, and paracrine signaling via secreted extracellular vesicles. In order to exploit these biological functions, systems to efficiently deliver genetic material into MSCs would therefore be highly desirable. In this study, efficient silencing of GFP expression by combining high N/P ratio siRNA and branched PEI (bPEI) polyplexes (siRNA-bPEI) polyplexes with glycosaminoglycans (GAGs), namely hyaluronic acid (HA), chondroitin sulfate (CS) and heparin sulfate (HS), and human serum albumin (HSA) is reported. These quaternary systems were characterized using surface charge, size and morphology and applied to MSCs, which represent a challenge due to their typically low transfection efficiency. The quaternary polyplexes promoted efficient charge shielding and release of siRNA in the cytoplasm with reduced toxicity. A high silencing efficiency of >90% (i.e., less than 10% remaining GFP expression) was achieved with noticeably reduced cellular toxicity, especially with siRNA-bPEI polyplexes modified with HA and HA + HSA. In general addition of GAGs led to more compact polyplexes. Endocytosis studies point to improved endosomal escape at high N/P ratios as a reason for high transfection efficiency and a role for hyaluronic acid in the uptake mechanism likely via CD44 interactions. Co-localization studies showed the polyplexes are stable in the cytosol over time, which correlates with a proper disassembly and subsequent silencing of GFP. Furthermore, GAG containing polyplexes were frequently co-localized with the nucleus. These findings in sum suggest that PEI/HSA/GAG based quaternary polyplexes are promising as transfection agents for MSCs. STATEMENT OF SIGNIFICANCE: Since mesenchymal stem cells (MSCs) are recruited to the site of tissue repair and play a role in immunomodulation, anti-inflammatory processes, and paracrine signaling, they present an excellent target for genetic engineering. However, delivery of genetic material into MSCs is challenging. In this study, >97% silencing of constitutive green fluorescent protein expression in human MSCs (hMSCs) using high N/P ratio polyplexes of branched-PEI-siRNA incorporating glycosaminoglycan as a charge neutralizer and human serum albumin as co-complexing agent is demonstrated. In addition to possessing good cytocompatibility and excellent cytosolic stability; polyplexes incorporating GAGs also showed altered endocytic uptake, with incorporation of hyaluronic acid promoting caveolae-mediated entry. Our system highlights the importance of physiologically derived macromolecules in delivery of genetic material into hMSCs.

Cell membrane and bioactive factors derived from mesenchymal stromal cells: Cell-free based therapy for inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract associated with multifactorial conditions such as ulcerative colitis and Crohn’s disease. Although the underlying mechanisms of IBD remain unclear, growing evidence has shown that dysregulated immune system reactions in genetically susceptible individuals contribute to mucosal inflammation. However, conventional treatments have been effective in inducing remission of IBD but not in preventing the relapse of them. In this way, mesenchymal stromal cells (MSC) therapy has been recognized as a promising treatment for IBD due to their immunomodulatory properties, ability to differentiate into several tissues, and homing to inflammatory sites. Even so, literature is conflicted regarding the location and persistence of MSC in the body after transplantation. For this reason, recent studies have focused on the paracrine effect of the biofactors secreted by MSC, especially in relation to the immunomodulatory potential of soluble factors (cytokines, chemokines, and growth factors) and extracellular vehicles that are involved in cell communication and in the transfer of cellular material, such as proteins, lipids, and nucleic acids. Moreover, treatment with interferon-γ, tumor necrosis factor-α, and interleukin-1β causes MSC to express immunomodulatory molecules that mediate the suppression via cell-contact dependent mechanisms. Taken together, we present an overview of the role of bioactive factors and cell membrane proteins derived from MSC as a cell-free therapy that can improve IBD treatment.

Adipose Mesenchymal Extracellular Vesicles as Alpha-1-Antitrypsin Physiological Delivery Systems for Lung Regeneration

Accumulating evidence shows that Mesenchymal Stem/Stromal Cells (MSCs) exert their therapeutic effects by the release of secretome, made of both soluble proteins and nano/microstructured extracellular vesicles (EVs). In this work, for the first time, we proved by a proteomic investigation that adipose-derived (AD)-MSC-secretome contains alpha-1-antitrypsin (AAT), the main elastase inhibitor in the lung, 72 other proteins involved in protease/antiprotease balance, and 46 proteins involved in the response to bacteria. By secretome fractionation, we proved that AAT is present both in the soluble fraction of secretome and aggregated and/or adsorbed on the surface of EVs, that can act as natural carriers promoting AAT in vivo stability and activity. To modulate secretome composition, AD-MSCs were cultured in different stimulating conditions, such as serum starvation or chemicals (IL-1β and/or dexamethasone) and the expression of the gene encoding for AAT was increased. By testing in vitro the anti-elastase activity of MSC-secretome, a dose-dependent effect was observed; chemical stimulation of AD-MSCs did not increase their secretome anti-elastase activity. Finally, MSC-secretome showed anti-bacterial activity on Gram-negative bacteria, especially for Klebsiellapneumoniae. These preliminary results, in addition to the already demonstrated immunomodulation, pave the way for the use of MSC-secretome in the treatment of AAT-deficiency lung diseases.

Mesenchymal stem/stromal cell secretome for lung regeneration: The long way through "pharmaceuticalization" for the best formulation

Pulmonary acute and chronic diseases, such as chronic obstructive pulmonary disease, pulmonary fibrosis and pulmonary hypertension, are considered to be major health issues worldwide. Cellular therapies with Mesenchymal Stem Cells (MSCs) offer a new therapeutic approach for chronic and acute lung diseases related to their anti-inflammatory, immunomodulatory, regenerative, pro-angiogenic and anti-fibrotic properties. Such therapeutic effects can be attributed to MSC-secretome, made of free soluble proteins and extracellular vesicles (EVs). This review summarizes the recent findings related to the efficacy and safety of MSC-derived products in pre-clinical models of lung diseases, pointing out the biologically active substances contained into MSC-secretome and their mechanisms involved in tissue regeneration. A perspective view is then provided about the missing steps required for the secretome "pharmaceuticalization" into a high quality, safe and effective medicinal product, as well as the formulation strategies required for EV non-invasive route of administration, such as inhalation.

Exosomes: Diagnostic Biomarkers and Therapeutic Delivery Vehicles for Cancer

Exosomes are described as nanoscale extracellular vesicles (EVs) secreted by multiple cell types and extensively distributed in various biological fluids. They contain multifarious bioactive molecules and transfer them to adjoining or distal cells through systemic circulation, participating in intracellular and intercellular communication, and modulating host-tumor cell interactions. Recent research has indicated that exosomes obtained from different biological fluids and their contents (proteins, nucleic acids, glycoconjugates, and lipids) can serve as biomarkers for cancer diagnosis, prognosis, and therapeutic response. Furthermore, the discovery of exosomes as therapeutic delivery vehicles has drawn much attention in antineoplastic drug delivery. They can be utilized for therapeutic delivery of proteins, genetic drugs, and chemotherapeutic drugs. Herein, this review summarizes the biogenesis, structure, and components of exosomes, focusing primarily on their two possible applications as diagnostic biomarkers and therapeutic delivery vehicles for cancers.

Paclitaxel-Loaded Silk Fibroin Nanoparticles: Method Validation by UHPLC-MS/MS to Assess an Exogenous Approach to Load Cytotoxic Drugs

The aim of this work was to load an anticancer drug, paclitaxel (PTX), on Silk Fibroin Nanoparticles (SFNs) by using an exogenous approach. SFNs were produced, freeze-dried and then loaded with PTX. An exogenous method allowed us to reduce both drug loss and environmental impact. In order to quantify PTX loaded in SFNs, a simple and reliable method using reversed phase liquid chromatography coupled to tandem mass spectrometry (rp-UHPLC-MS/MS) was developed. This methodology was validated by the determination of spiked QC samples in three consecutive days. Good accuracy and precision of the method were obtained, while the intra-day and inter-day precisions were less than 10.3%. For PTX, the limit of quantitation (LOQ) was 5.0 ng/mL. Recovery from the matrix (SFNs-PTX pellets) was calculated (81.2% at LOQ value) as PTX was entrapped in a new matrix like the polymer silk fibroin-based. This method was successfully applied to determine the encapsulation efficiency (1.00 ± 0.19%) and the nanoparticle loading (0.12 ± 0.02% w/w). The in vitro anticancer activity of SFNs-PTX was tested against CFPAC-1 cancer cells; results demonstrated a very high cytotoxic activity of SFNs-PTX, with a dose dependent inhibition of CFPAC-1 proliferation, confirmed by the IC50 value of 3450 ± 750 ng/mL.

Taxol-Loaded MSC-Derived Exosomes Provide a Therapeutic Vehicle to Target Metastatic Breast Cancer and Other Carcinoma Cells

MSC-derived exosomes display, among others, an efficient biocompatibility and a reduced intrinsic immunogenicity, representing a valuable vehicle for drug delivery in a tumor-therapeutic approach. Following treatment of several human mesenchymal stroma/stem-like cell (MSC) populations with sub-lethal concentrations of taxol for 24 h, exosomes were isolated and applied to different human cancer populations including A549 lung cancer, SK-OV-3 ovarian cancer, and MDA-hyb1 breast cancer cells. While MSC control exosomes revealed little if any growth inhibition on the tumor cells, exposure to taxol-loaded MSC-derived exosomes was associated with 80–90% cytotoxicity. A similar application of taxol-loaded exosomes from HuVEC displayed much fewer effects. Quantification by LC-MS/MS analysis demonstrated a 7.6-fold reduced taxol concentration in MSC exosomes when compared to equivalent cytotoxic in vitro effects achieved with taxol substances, indicating a specific and more efficient tumor-targeting property. Consequently, MSC-derived taxol exosomes were tested in vivo. Highly metastatic MDA-hyb1 breast tumors were induced in NODscid mice, and systemic intravenous application of MSC-derived taxol exosomes revealed a more than 60% reduction of subcutaneous primary tumors. Moreover, the amount of distant organ metastases observed at least in lung, liver, spleen, and kidney was reduced by 50% with MSC taxol exosomes, similar to the effects observed with taxol, although the concentration of taxol in exosomes was about 1000-fold reduced. Together, these findings in different cancer cell populations and in vivo provide promising future perspectives for drug-loaded MSC-derived exosomes in efficiently targeting primary tumors and metastases by reducing side effects.

Challenges and Controversies in Human Mesenchymal Stem Cell Therapy

Stem cell therapy is being intensely investigated within the last years. Expectations are high regarding mesenchymal stem cell (MSC) treatment in translational medicine. However, many aspects concerning MSC therapy should be profoundly defined. Due to a variety of approaches that are investigated, potential effects of stem cell therapy are not transparent. On the other hand, most results of MSC administration in vivo have confirmed their safety and showed promising beneficial outcomes. However, the therapeutic effects of MSC-based treatment are still not spectacular and there is a potential risk related to MSC applications into specific cell niche that should be considered in long-term observations and follow-up outcomes. In this review, we intend to address some problems and critically discuss the complex nature of MSCs in the context of their effective and safe applications in regenerative medicine in different diseases including graft versus host disease (GvHD) and cardiac, neurological, and orthopedic disorders.

Cell membrane capsule: a novel natural tool for antitumour drug delivery

INTRODUCTION

Chemotherapy plays an important role in antitumour therapy, but causes serious adverse reactions. So, drug delivery system (DDS) with cell-targeting ability is an important method to reduce adverse reactions while ensuring the effectiveness of chemotherapy. Synthetic drug carriers and DDSs based on cells have proven safety and efficacy, but they also have many deficiencies or limitations. Cell membrane capsules (CMCs), which are based on extracellular vesicles (EVs), are a promising biomimetic DDS that retains some cell membrane channels and cytoplasmic functions, with escape macrophage phagocytosis.

AREAS COVERED

The EVs for constructing CMCs can be prepared by natural secretion, chemical-induced budding, nanofilter membrane extrusion and similar methods and are isolated and purified by a variety of methods such as centrifugation and liquid chromatography. CMCs can target the tumour cells either spontaneously or through targeting modifications using proteins or aptamers to actively target the tumour cells. CMCs can be directly wrapped with chemicals, photosensitizers, RNA, proteins and other ingredients, or they can be loaded with antitumour agent-loaded synthetic nanoparticles, which are delivered to the target cells to play a specific role.

EXPERT OPINION

This review describes the concept, function, characteristics, origins, and manufacturing methods of CMCs and their application in antitumour therapy.

Freeze-dried and GMP-compliant pharmaceuticals containing exosomes for acellular mesenchymal stromal cell immunomodulant therapy

Aim: To validate the use of ultrafiltration (UF) as an alternative applicable industrial method to replace ultracentrifugation (UC) in the purification of mesenchymal stromal cell (MSC)-secretome. Materials & methods: Pharmaceutical formulations containing secretome and/or extracellular vesicles were extracted from adipose-MSCs and bone marrow-MSCs by combining UF or UC with lyophilization. Results & conclusion: UF led to higher protein, lipid, cytokine and exosomes yields compared with UC. The isolation procedure and cell source influenced immunomodulatory activity, which was in vitro evaluated by inhibition of phytohemagglutinin-activated peripheral blood mononuclear cell proliferation, and by modulation of IL-10, IFN-γ and IL-6. A secretome dosage was identified to obtain the same immunomodulatory activity of MSCs, paving the way for cell-free therapy.

Exploring the roles of MSCs in infections: focus on bacterial diseases

Despite human healthcare advances, some microorganisms continuously react evolving new survival strategies, choosing between a commensal fitness and a pathogenic attitude. Many opportunistic microbes are becoming an increasing cause of clinically evident infections while several renowned infectious diseases sustain a considerable number of deaths. Besides the primary and extensively investigated role of immune cells, other cell types are involved in the microbe-host interaction during infection. Interestingly, mesenchymal stem cells (MSCs), the current leading players in cell therapy approaches, have been suggested to contribute to tackling pathogens and modulating the host immune response. In this context, this review critically explores MSCs' role in E. coli, S. aureus, and polymicrobial infections. Summarizing from various studies, in vitro and in vivo results support the mechanistic involvement of MSCs and their derivatives in fighting infection and in contributing to microbial spreading. Our work outlines the double face of MSCs during infection, disease, and sepsis, highlighting potential pitfalls in MSC-based therapy due to the MSCs' susceptibility to pathogens' weapons. We also identify potential targets to improve infection treatments, and propose the potential applications of MSCs for vaccine research.

In Vitro Anticancer Activity of Extracellular Vesicles (EVs) Secreted by Gingival Mesenchymal Stromal Cells Primed with Paclitaxel

Interdental papilla are an interesting source of mesenchymal stromal cells (GinPaMSCs), which are easy to isolate and expand in vitro. In our laboratory, GinPaMSCs were isolated, expanded, and characterized by studying their secretome before and after priming with paclitaxel (PTX). The secretome of GinPaMSCs did not affect the growth of cancer cell lines tested in vitro, whereas the secretome of GinPaMSCs primed with paclitaxel (GinPaMSCs/PTX) exerted a significant anticancer effect. GinPaMSCs were able to uptake and then release paclitaxel in amounts pharmacologically effective against cancer cells, as demonstrated in vitro by the direct activity of GinPaMSCs/PTX and their secretome against both human pancreatic carcinoma and squamous carcinoma cells. PTX was associated with extracellular vesicles (EVs) secreted by cells (EVs/PTX), suggesting that PTX is incorporated into exosomes during their biogenesis. The isolation of mesenchymal stromal cells (MSCs) from gingiva is less invasive than that from other tissues (such as bone marrow and fat), and GinPaMSCs provide an optimal substrate for drug-priming to obtain EVs/PTX having anticancer activity. This research may contribute to develop new strategies of cell-mediated drug delivery by EVs that are easy to store without losing function, and could have a superior safety profile in therapy.

Extracellular Vesicle Quantification and Characterization: Common Methods and Emerging Approaches

Extracellular vesicles (EVs) are a family of small membrane vesicles that carry information about cells by which they are secreted. Growing interest in the role of EVs in intercellular communication, but also in using their diagnostic, prognostic and therapeutic potential in (bio) medical applications, demands for accurate assessment of their biochemical and physical properties. In this review, we provide an overview of available technologies for EV analysis by describing their working principles, assessing their utility in EV research and summarising their potential and limitations. To emphasise the innovations in EV analysis, we also highlight the unique possibilities of emerging technologies with high potential for further development.

Engineering Bioactive Self-Healing Antibacterial Exosomes Hydrogel for Promoting Chronic Diabetic Wound Healing and Complete Skin Regeneration

Rationale: Chronic nonhealing diabetic wound therapy and complete skin regeneration remains a critical clinical challenge. The controlled release of bioactive factors from a multifunctional hydrogel was a promising strategy to repair chronic wounds. Methods: Herein, for the first time, we developed an injectable, self-healing and antibacterial polypeptide-based FHE hydrogel (F127/OHA-EPL) with stimuli-responsive adipose-derived mesenchymal stem cells exosomes (AMSCs-exo) release for synergistically enhancing chronic wound healing and complete skin regeneration. The materials characterization, antibacterial activity, stimulated cellular behavior and in vivo full-thickness diabetic wound healing ability of the hydrogels were performed and analyzed. Results: The FHE hydrogel possessed multifunctional properties including fast self-healing process, shear-thinning injectable ability, efficient antibacterial activity, and long term pH-responsive bioactive exosomes release behavior. In vitro, the FHE@exosomes (FHE@exo) hydrogel significantly promoted the proliferation, migration and tube formation ability of human umbilical vein endothelial cells (HUVECs). In vivo, the FHE@exo hydrogel significantly enhanced the healing efficiency of diabetic full-thickness cutaneous wounds, characterized with enhanced wound closure rates, fast angiogenesis, re-epithelization and collagen deposition within the wound site. Moreover, the FHE@exo hydrogel displayed better healing outcomes than those of exosomes or FHE hydrogel alone, suggesting that the sustained release of exosomes and FHE hydrogel can synergistically facilitate diabetic wound healing. Skin appendages and less scar tissue also appeared in FHE@exo hydrogel treated wounds, indicating its potent ability to achieve complete skin regeneration. Conclusion: This work offers a new approach for repairing chronic wounds completely through a multifunctional hydrogel with controlled exosomes release.

Pilot Production of Mesenchymal Stem/Stromal Freeze-Dried Secretome for Cell-Free Regenerative Nanomedicine: A Validated GMP-Compliant Process

In this paper, a pilot production process for mesenchymal stem/stromal freeze-dried secretome was performed in a validated good manufacturing practice (GMP)-compliant cell factory. Secretome was purified from culture supernatants by ultrafiltration, added to cryoprotectant, lyophilized and characterized. We obtained a freeze-dried, "ready-off-the-shelf" and free soluble powder containing extracellular vesicles and proteins. In the freeze-dried product, a not-aggregated population of extracellular vesicles was detected by nanoparticle tracking analysis; Fourier transform infrared spectra showed the simultaneous presence of protein and lipids, while differential scanning calorimetry demonstrated that lyophilization process successfully occurred. A proteomic characterization allowed the identification of proteins involved in immune response, response to stress, cytoskeleton and metabolism. Moreover, the product was not cytotoxic up to concentrations of 25 mg/mL (on human fibroblasts, chondrocytes and nucleus pulposus cells by MTT assay) and was blood compatible up to 150 mg/mL. Finally, at concentrations between 5 and 50 mg/mL, freeze-dried secretome showed to in vitro counteract the oxidative stress damage induced by H₂O₂ on nucleus pulposus cells by MTT assay.

Extracellular vesicles: intelligent delivery strategies for therapeutic applications

Extracellular vesicles (EV), in particular exosomes, have been the object of intense research, due to their potential to mediate intercellular communication, modulating the phenotype of target cells. The natural properties and functions of EV are being exploited as biomarkers for disease diagnosis and prognosis, and as nano-bio-carriers for the development of new therapeutic strategies. EV have been particularly examined in the field of cancer, but are also increasingly investigated in other areas, like immune-related diseases and regenerative medicine. In this review, the therapeutic use of EV as drug delivery systems is described, balancing the advantages and drawbacks of different routes for their in vivo administration. Systemic and local delivery of EV are discussed, tackling the persisting difficulties in the assessment of their pharmacokinetics, pharmacodynamics and biodistribution in vivo. Finally, we discuss the future perspectives for incorporating EV into delivery systems and their use for an improved and controlled release of EV in vivo.

Could hypoxia influence basic biological properties and ultrastructural features of adult canine mesenchymal stem /stromal cells?

The aim of the present study was to compare canine adipose tissue mesenchymal stem cells cultured under normoxic (20% O₂) and not severe hypoxic (7% O₂) conditions in terms of marker expression, proliferation rate, differentiation potential and cell morphology. Intra-abdominal fat tissue samples were recovered from 4 dogs and cells isolated from each sample were cultured under hypoxic and normoxic conditions. Proliferation rate and adhesion ability were determined, differentiation towards chondrogenic, osteogenic and adipogenic lineages was induced; the expression of CD44, CD34, DLA-DQA1, DLA-DRA1 was determined by PCR, while flow cytometry analysis for CD90, CD105, CD45 and CD14 was carried out. The morphological study was performed by transmission electron microscopy. Canine AT-MSCs, cultured under different oxygen tensions, maintained their basic biological features. However, under hypoxia, cells were not able to form spheroid aggregates revealing a reduction of their adhesivness. In both conditions, MSCs mainly displayed the same ultrastructural morphology and retained the ability to produce membrane vesicles. Noteworthy, MSCs cultivated under hypoxya revealed a huge shedding of large complex vesicles, containing smaller round-shaped vesicles. In our study, hypoxia partially influences the basic biological properties and the ultrastructural features of canine mesenchymal stem /stromal cells. Further studies are needed to clarify how hypoxia affects EVs production in term of amount and content in order to understand its contribution in tissue regenerative mechanisms and the possible employment in clinical applications. The findings of the present work could be noteworthy for canine as well as for other mammalian species.

Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response

Mesenchymal stem cells (MSCs) have been reported to exert therapeutic effects on immunoregulation, tissue repair, and regeneration from the bench to the bedside. Increasing evidence demonstrates that extracellular vesicles (EVs) derived from MSCs could contribute to these effects and are considered as a potential replacement for stem cell-based therapies. However, the efficacy and underlying mechanisms of EV-based treatment in hepatic ischemia-reperfusion injury (IRI) remain unclear. Here, we demonstrated that human umbilical cord MSC-EVs (huc-MSC-EVs) could protect against IRI-induced hepatic apoptosis by reducing the infiltration of neutrophils and alleviating oxidative stress in hepatic tissue in vivo. Meanwhile, huc-MSC-EVs reduced the respiratory burst of neutrophils and prevented hepatocytes from oxidative stress-induced cell death in vitro. Interestingly, we found that the mitochondria-located antioxidant enzyme, manganese superoxide dismutase (MnSOD), was encapsulated in huc-MSC-EVs and reduced oxidative stress in the hepatic IRI model. Knockdown of MnSOD in huc-MSCs decreased the level of MnSOD in huc-MSC-EVs and attenuated the antiapoptotic and antioxidant capacities of huc-MSC-EVs, which could be partially rescued by MnSOD mimetic manganese (III) 5,10,15,20-tetrakis (4-benzoic acid) porphyrin (MnTBAP). In summary, these findings provide new clues to reveal the therapeutic effects of huc-MSC-EVs on hepatic IRI and evaluate their preclinical application.-Yao, J., Zheng, J., Cai, J., Zeng, K., Zhou, C., Zhang, J., Li, S., Li, H., Chen, L., He, L., Chen, H., Fu, H., Zhang, Q., Chen, G., Yang, Y., Zhang, Y. Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response.

The therapeutic potential of the mesenchymal stem cell secretome in ischaemic stroke

Mesenchymal stem cells (MSCs) hold great potential as a regenerative therapy for stroke, leading to increased repair and functional recovery in animal models of cerebral ischaemia. While it was initially hypothesised that cell replacement was an important mechanism of action of MSCs, focus has shifted to their paracrine actions or the so called "bystander" effect. MSCs secrete a wide array of growth factors, chemokines, cytokines and extracellular vesicles, commonly referred to as the MSC secretome. There is evidence suggesting the MSC secretome can promote repair through a number of mechanisms including preventing cell apoptosis, modulating the inflammatory response and promoting endogenous repair mechanisms such as angiogenesis and neurogenesis. In this review, we will discuss the in vitro approaches currently being employed to drive the MSC secretome towards a more anti-inflammatory and regenerative phenotype. We will then examine the role of the secretome in promoting repair and improving recovery in preclinical models of cerebral ischaemia.

Concise Review: Mesenchymal Stem Cell-Based Drug Delivery: The Good, the Bad, the Ugly, and the Promise

The development of mesenchymal stem cells (MSCs) as cell‐based drug delivery vectors for numerous clinical indications, including cancer, has significant promise. However, a considerable challenge for effective translation of these approaches is the limited tumor tropism and broad biodistribution observed using conventional MSCs, which raises concerns for toxicity to nontarget peripheral tissues (i.e., the bad). Consequently, there are a variety of synthetic engineering platforms in active development to improve tumor‐selective targeting via increased homing efficiency and/or specificity of drug activation, some of which are already being evaluated clinically (i.e., the good). Unfortunately, the lack of robust quantification and widespread adoption of standardized methodologies with high sensitivity and resolution has made accurate comparisons across studies difficult, which has significantly impeded progress (i.e., the ugly). Herein, we provide a concise review of active and passive MSC homing mechanisms and biodistribution postinfusion; in addition to in vivo cell tracking methodologies and strategies to enhance tumor targeting with a focus on MSC‐based drug delivery strategies for cancer therapy. Stem Cells Translational Medicine2018;1–13