Role of stem-cell-derived microvesicles in the paracrine action of stem cells. Biochem Soc Trans. 2013;41:283-287. [PMID: 23356298 DOI: 10.1042/bst20120192]

Therapeutic Potential of Stem Cell-Derived Extracellular Vesicles in Liver Injury

Liver injury caused by various factors significantly impacts human health. Stem cell transplantation has potential for enhancing liver functionality, but safety concerns such as immune rejection, tumorigenesis, and the formation of emboli in the lungs remain. Recent studies have shown that stem cells primarily exert their effects through the secretion of extracellular vesicles (EVs). EVs have been shown to play crucial roles in reducing inflammation, preventing cell death, and promoting liver cell proliferation. Additionally, they can function as carriers to deliver targeted drugs to the liver, thereby exerting specific physiological effects. EVs possess several advantages, including structural stability, low immunogenicity, minimal tumorigenicity targeting capabilities, and convenient collection. Consequently, EVs have garnered significant attention from researchers and are expected to become alternative therapeutic agents to stem cell therapy. This article provides a comprehensive review of the current research progress in the use of stem cell-derived EVs in the treatment of liver injury.

MSC Exosomes Containing Valproic Acid Promote Wound Healing by Modulating Inflammation and Angiogenesis

PURPOSE

Chronic wounds that are difficult to heal pose a major challenge for clinicians and researchers. Currently, common treatment methods focus on isolating the wound from the outside world, relying on the tissue at the wound site to grow and heal unaided. Umbilical cord mesenchymal stem cell (MSC) exosomes can promote wound healing by enhancing new blood vessel growth at the wound site. Valproic acid (VPA) reduces the inflammatory response and acts on macrophages to accelerate wound closure. In this study, VPA was loaded into umbilical cord MSC exosomes to form a drug carrier exosome (VPA-EXO) with the aim of investigating the effect of VPA-EXO on wound healing.

METHODS

This study first isolated and obtained umbilical cord MSC exosomes, then added VPA to the exosomes and explored the ability of VPA-EXO to promote the proliferation and migration of human skin fibroblasts (HSFs) and human umbilical vein endothelial cells (HUVECs), as well as the ability to promote the angiogenesis of HUVECs, by using scratch, Transwell, and angiogenesis assays. An in vitro cell model was established and treated with VPA-EXO, and the expression levels of inflammation and pro-angiogenesis-related proteins and genes were examined using Western blot and qRT-PCR. The therapeutic effect of VPA-EXO on promoting wound healing in a whole skin wound model was investigated using image analysis of the wound site, H&E staining, and immunohistochemical staining experiments in a mouse wound model.

RESULTS

The in vitro model showed that VPA-EXO effectively promoted the proliferation and migration of human skin fibroblast cells and human umbilical vein endothelial cells; significantly inhibited the expression of MMP-9, IL-1β, IL-8, TNF-α, and PG-E2; and promoted the expression of vascular endothelial growth factors. In the mouse wound model, VPA-EXO reduced inflammation at the wound site, accelerated wound healing, and significantly increased the collagen content of tissue at the wound site.

CONCLUSIONS

As a complex with dual efficacy in simultaneously promoting tissue regeneration and inhibiting inflammation, VPA-EXO has potential applications in tissue wound healing and vascular regeneration. In future studies, we will further investigate the mechanism of action and application scenarios of drug-loaded exosome complexes in different types of wound healing and vascular regeneration.

Bone marrow stromal and anterior cruciate ligament remnant cell co-culture-derived extracellular vesicles promote cell activity in both cell types

The significance of anterior cruciate ligament (ACL) remnants during reconstruction remains unclear. Co-culturing ACL remnant cells and bone marrow stromal cells (BMSCs) may reduce apoptosis and enhance hamstring tendon activity. This study investigated whether extracellular vesicles (EVs), which facilitate cell-cell interactions, act as the active components, improving graft maturation in this co-culture. The effects of EVs on cell viability, proliferation, migration and gene expression in the rabbit ACL remnant cells and BMSCs were assessed using control (BMSC-only culture), co-culture (ACL remnant cells and BMSCs, CM) and co-culture without EVs (CM ∆ EVs) media. EVs were isolated from control (BMSC-EV) and co-culture (CM-EV) media and characterized. CM significantly enhanced the proliferation, migration and expression of transforming growth factor (TGF-β)-, vascular endothelial growth factor (VEGF)-, collagen synthesis- and tenogenesis-related genes. However, CM-induced effects were reversed by the CM ∆ EVs treatment. CM-EV treatment exhibited higher potential to enhance proliferation, migration and gene expression in the ACL remnant cells and BMSCs than BMSC-EV and non-EV treatments. In conclusion, EVs, secreted under the coexistence of ACL remnant cells and BMSCs, primarily increase the cell viability, proliferation, migration and gene expression of collagen synthesis-, TGF-β-, VEGF- and tenogenesis-related genes in both cell types.

Epigenetic Mechanisms in Sepsis-Associated Acute Kidney Injury

Sepsis, the dysregulated immune response of the host to infections, leads to numerous complications, including multiple organ dysfunction with sepsis-associated acute kidney injury (SA-AKI) being a frequent complication associated with increased risk of mortality and the progression toward chronic kidney disease (CKD). Several mechanisms have been widely investigated in understanding the complex pathophysiology of SA-AKI, including hemodynamic alterations, inflammation, oxidative stress, and direct cellular injury driven by pathogens or cell-derived products (pathogen-associated molecular patterns and damage-associated molecular patterns). Despite advancements in the management of septic patients, the prognosis of SA-AKI patients remains significantly poor and is associated with high in-hospital mortality and adverse long-term outcomes. Therefore, recent research has focused on the early identification of specific SA-AKI endotypes and subphenotypes through epigenetic analysis and the use of potential biomarkers, either alone or in combination with clinical data, to improve prognosis. Epigenetic regulation, such as DNA methylation, histone modifications, and noncoding RNA modulation, is crucial in modulating gene expression in response to stress and renal injury in SA-AKI. At the same time, these modifications are dynamic and reversible processes that can alter gene expression in several pathways implicated in the context of SA-AKI, including inflammation, immune response, and tolerance status. In addition, specific epigenetic modifications may exacerbate renal damage by causing persistent inflammation or cellular metabolic reprogramming, leading to progression toward CKD. This review aims to provide a comprehensive understanding of the epigenetic characteristics that define SA-AKI, also exploring targeted therapies that can improve patient outcomes and limit the chronic progression of this syndrome.

From mesenchymal stem cells to their extracellular vesicles: Progress and prospects for asthma therapy

Asthma is a widespread public health concern, with an increasing incidence. Despite the implementation of current treatment strategies, asthma control, particularly for severe cases, remains suboptimal. Recent research has revealed the encouraging prospects of extracellular vesicles (EVs) secreted by mesenchymal stem cells (MSCs) as a viable therapeutic option for alleviating asthma symptoms. Therefore, the present review aims to provide an overview of the current progress and the therapeutic mechanisms of using MSC-derived EVs (MSC-EVs) for asthma treatment. Additionally, different administration approaches for EVs and their impacts on biodistribution and the curative outcomes of EVs are summarized. Notably, the potential benefits of nebulized inhalation of MSC-EVs are addressed. Also, the possibilities and challenges of using MSC-EVs for asthma treatment in clinics are highlighted. Overall, this review is intended to give new insight into the utilization of MSC-EVs as a potential biological drug for asthma treatment.

Transitioning from static to suspension culture system for large-scale production of xeno-free extracellular vesicles derived from mesenchymal stromal cells

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) have shown increasing therapeutic potential in the last years. However, large production of EV is required for therapeutic purposes. Thereby, scaling up MSC cultivation in bioreactors is essential to allow culture parameters monitoring. In this study, we reported the establishment of a scalable bioprocess to produce MSC-EV in suspension cultures using spinner flasks and human collagen-coated microcarriers (3D culture system). We compared the EV production in this 3D culture system with the standard static culture using T-flasks (2D culture system). The EV produced in both systems were characterized and quantify by western blotting and nanoparticle tracking analysis. The presence of the typical protein markers CD9, CD63, and CD81 was confirmed by western blotting analyses for EV produced in both culture systems. The cell fold-increase was 5.7-fold for the 3D culture system and 4.6-fold for the 2D culture system, signifying a fold-change of 1.2 (calculated as the ratio of fold-increase 3D to fold-increase 2D). Furthermore, it should be noted that the total cell production in the spinner flask cultures was 4.8 times higher than that in T-flask cultures. The total cell production in the spinner flask cultures was 5.2-fold higher than that in T-flask cultures. While the EV specific production (particles/cell) in T-flask cultures (4.40 ± 1.21 × 108 particles/mL, p < 0.05) was higher compared to spinner flask cultures (2.10 ± 0.04 × 108 particles/mL, p < 0.05), the spinner flask culture system offers scalability, making it capable of producing enough MSC-EV at a large scale for clinical applications. Therefore, we concluded that 3D culture system evaluated here serves as an efficient transitional platform that enables the scaling up of MSC-EV production for therapeutic purposes by utilizing stirred tank bioreactors and maintaining xeno-free conditions.

Human umbilical cord mesenchymal stem cell-derived exosomes ameliorate renal fibrosis in diabetic nephropathy by targeting Hedgehog/SMO signaling

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease globally. Currently, there are no effective drugs for the treatment of DN. Although several studies have reported the therapeutic potential of mesenchymal stem cells, the underlying mechanisms remain largely unknown. Here, we report that both human umbilical cord MSCs (UC-MSCs) and UC-MSC-derived exosomes (UC-MSC-exo) attenuate kidney damage, and inhibit epithelial-mesenchymal transition (EMT) and renal fibrosis in streptozotocin-induced DN rats. Strikingly, the Hedgehog receptor, smoothened (SMO), was significantly upregulated in the kidney tissues of DN patients and rats, and positively correlated with EMT and renal fibrosis. UC-MSC and UC-MSC-exo treatment resulted in decrease of SMO expression. In vitro co-culture experiments revealed that UC-MSC-exo reduced EMT of tubular epithelial cells through inhibiting Hedgehog/SMO pathway. Collectively, UC-MSCs inhibit EMT and renal fibrosis by delivering exosomes and targeting Hedgehog/SMO signaling, suggesting that UC-MSCs and their exosomes are novel anti-fibrotic therapeutics for treating DN.

Dynamic cultivation of human mesenchymal stem/stromal cells for the production of extracellular vesicles in a 3D bioreactor system

PURPOSE

3D cell culture and hypoxia have been demonstrated to increase the therapeutic effects of mesenchymal stem/stromal cells (MSCs)-derived extracellular vesicles (EVs). In this study, a process for the production of MSC-EVs in a novel 3D bioreactor system under normoxic and hypoxic conditions was established and the resulting EVs were characterized.

METHODS

Human adipose-derived MSCs were seeded and cultured on a 3D membrane in the VITVO® bioreactor system for 7 days. Afterwards, MSC-EVs were isolated and characterized via fluorescence nanoparticle tracking analysis, flow cytometry with staining against annexin V (Anx5) as a marker for EVs exposing phosphatidylserine, as well as CD73 and CD90 as MSC surface markers.

RESULTS

Cultivation of MSC in the VITVO® bioreactor system demonstrated a higher concentration of MSC-EVs from the 3D bioreactor (9.1 × 109 ± 1.5 × 109 and 9.7 × 109 ± 3.1 × 109 particles/mL) compared to static 2D culture (4.2 × 109 ± 7.5 × 108 and 3.9 × 109 ± 3.0 × 108 particles/mL) under normoxic and hypoxic conditions, respectively. Also, the particle-to-protein ratio as a measure for the purity of EVs increased from 3.3 × 107 ± 1.1 × 107 particles/µg protein in 2D to 1.6 × 108 ± 8.3 × 106 particles/µg protein in 3D. Total MSC-EVs as well as CD73-CD90+ MSC-EVs were elevated in 2D normoxic conditions. The EV concentration and size did not differ significantly between normoxic and hypoxic conditions.

CONCLUSION

The production of MSC-EVs in a 3D bioreactor system under hypoxic conditions resulted in increased EV concentration and purity. This system could be especially useful in screening culture conditions for the production of 3D-derived MSC-EVs.

Engineered exosomes enriched with select microRNAs amplify their therapeutic efficacy for traumatic brain injury and stroke

Traumatic brain injury (TBI) and stroke stand as prominent causes of global disability and mortality. Treatment strategies for stroke and TBI are shifting from targeting neuroprotection toward cell-based neurorestorative strategy, aiming to augment endogenous brain remodeling, which holds considerable promise for the treatment of TBI and stroke. Compelling evidence underscores that the therapeutic effects of cell-based therapy are mediated by the active generation and release of exosomes from administered cells. Exosomes, endosomal derived and nano-sized extracellular vesicles, play a pivotal role in intercellular communication. Thus, we may independently employ exosomes to treat stroke and TBI. Systemic administration of mesenchymal stem cell (MSC) derived exosomes promotes neuroplasticity and neurological functional recovery in preclinical animal models of TBI and stroke. In this mini review, we describe the properties of exosomes and recent exosome-based therapies of TBI and stroke. It is noteworthy that the microRNA cargo within exosomes contributes to their therapeutic effects. Thus, we provide a brief introduction to microRNAs and insight into their key roles in mediating therapeutic effects. With the increasing knowledge of exosomes, researchers have "engineered" exosome microRNA content to amplify their therapeutic benefits. We therefore focus our discussion on the therapeutic benefits of recently employed microRNA-enriched engineered exosomes. We also discuss the current opportunities and challenges in translating exosome-based therapy to clinical applications.

The role of apoptosis in spinal cord injury: a bibliometric analysis from 1994 to 2023

Background

Apoptosis after spinal cord injury (SCI) plays a pivotal role in the secondary injury mechanisms, which cause the ultimate neurologic insults. A better understanding of the molecular and cellular basis of apoptosis in SCI allows for improved glial and neuronal survival via the administrations of anti-apoptotic biomarkers. The knowledge structure, development trends, and research hotspots of apoptosis and SCI have not yet been systematically investigated.

Methods

Articles and reviews on apoptosis and SCI, published from 1st January 1994 to 1st Oct 2023, were retrieved from the Web of Science™. Bibliometrix in R was used to evaluate annual publications, countries, affiliations, authors, sources, documents, key words, and hot topics.

Results

A total of 3,359 publications in accordance with the criterions were obtained, which exhibited an ascending trend in annual publications. The most productive countries were the USA and China. Journal of Neurotrauma was the most impactive journal; Wenzhou Medical University was the most prolific affiliation; Cuzzocrea S was the most productive and influential author. "Apoptosis," "spinal-cord-injury," "expression," "activation," and "functional recovery" were the most frequent key words. Additionally, "transplantation," "mesenchymal stemness-cells," "therapies," "activation," "regeneration," "repair," "autophagy," "exosomes," "nlrp3 inflammasome," "neuroinflammation," and "knockdown" were the latest emerging key words, which may inform the hottest themes.

Conclusions

Apoptosis after SCI may cause the ultimate neurological damages. Development of novel treatments for secondary SCI mainly depends on a better understanding of apoptosis-related mechanisms in molecular and cellular levels. Such therapeutic interventions involve the application of anti-apoptotic agents, free radical scavengers, as well as anti-inflammatory drugs, which can be targeted to inhibit core events in cellular and molecular injury cascades pathway.

Stem cell Derived Extracellular Vesicles to Alleviate ischemia-reperfusion Injury of Transplantable Organs. A Systematic Review

BACKGROUND

The possible beneficial effects of stem cell-derived EV on ischemia-reperfusion injury (IRI) in organ transplantation have been frequently investigated; however, the source of EV, as well as the methods of isolation and administration vary widely. We conducted a systematic review to summarize current pre-clinical evidence on stem cell-derived EV therapy for IRI of transplantable organs.

METHODS

PubMed, Embase and Web of Science were searched from inception until August 19th, 2022, for studies on stem cell-derived EV therapy for IRI after heart, kidney, liver, pancreas, lung and intestine transplantation. The Systematic Review Center for Laboratory animal Experiments (SYRCLE) guidelines were followed to assess potential risk of bias.

RESULTS

The search yielded 4153 unique articles, of which 96 were retained. We identified 32 studies on cardiac IRI, 38 studies on renal IRI, 21 studies on liver IRI, four studies on lung IRI and one study on intestinal IRI. Most studies used rodent models of transient ischemic injury followed by in situ reperfusion. In all studies, EV therapy was associated with improved outcome albeit to a variable degree. EV-therapy reduced organ injury and improved function while displaying anti-inflammatory-, immunomodulatory- and pro-regenerative properties.

CONCLUSION

A multitude of animal studies support the potential of stem cell-derived EV-therapy to alleviate IRI after solid organ transplantation but suffer from low reporting quality and wide methodological variability. Future studies should focus on determining optimal stem cell source, dosage, and timing of treatment, as well as long-term efficacy in transplant models.

Role of Stem Cell-Derived Exosomes and microRNAs in Spinal Cord Injury

Neurological disorders represent a global health problem. Current pharmacological treatments often lead to short-term symptomatic relief but have dose-dependent side effects, such as inducing orthostatic arterial hypotension due to the blockade of alpha receptors, cardiotoxic effects due to impaired repolarization, and atrioventricular block and tachycardia, including ventricular fibrillation. These challenges have driven the medical community to seek effective treatments for this serious global health threat. Mesenchymal stem cells (MSCs) are pluripotent cells with anti-inflammatory, anti-apoptotic, and immunomodulatory properties, providing a promising alternative due to their ability to differentiate, favorable culture conditions, in vitro manipulation ability, and robust properties. Although MSCs themselves rarely differentiate into neurons at the site of injury after transplantation in vivo, paracrine factors secreted by MSCs can create environmental conditions for cell-to-cell communication and have shown therapeutic effects. Recent studies have shown that the pleiotropic effects of MSCs, particularly their immunomodulatory potential, can be attributed primarily to these paracrine factors. Exosomes derived from MSCs are known to play an important role in these effects. Many studies have evaluated the potential of exosome-based therapies for the treatment of various neurological diseases. In addition to exosomes, various miRNAs derived from MSCs have been identified to regulate genes and alleviate neuropathological changes in neurodegenerative diseases. This review explores the burgeoning field of exosome-based therapies, focusing on the effects of MSC-derived exosomes and exosomal miRNAs, and summarizes recent findings that shed light on the potential of exosomes in the treatment of neurological disorders. The insights gained from this review may pave the way for innovative and effective treatments for these complex conditions. Furthermore, we suggest the therapeutic effects of exosomes and exosomal miRNAs from MSCs, which have a rescue potential in spinal cord injury via diverse signaling pathways.

Optimized operation of a controlled stirred tank reactor system for the production of mesenchymal stromal cells and their extracellular vesicles

The therapeutic effects of human mesenchymal stromal cells (MSC) have been attributed mostly to their paracrine activity, exerted through small-secreted extracellular vesicles (EVs) rather than their engraftment into injured tissues. Currently, the production of MSC-derived EVs (MSC-EVs) is performed in laborious static culture systems with limited manufacturing capacity using serum-containing media. In this work, a serum-/xenogeneic-free microcarrier-based culture system was successfully established for bone marrow-derived MSC cultivation and MSC-EV production using a 2  l-scale controlled stirred tank reactor (STR) operated under fed-batch (FB) or fed-batch combined with continuous perfusion (FB/CP). Overall, maximal cell numbers of (3.0 ± 0.12) × 108 and (5.3 ± 0.32) × 108 were attained at Days 8 and 12 for FB and FB/CP cultures, respectively, and MSC(M) expanded under both conditions retained their immunophenotype. MSC-EVs were identified in the conditioned medium collected from all STR cultures by transmission electron microscopy, and EV protein markers were successfully identified by Western blot analysis. Overall, no significant differences were observed between EVs isolated from MSC expanded in STR operated under the two feeding approaches. EV mean sizes of 163 ± 5.27 nm and 162 ± 4.44 nm (p > 0.05) and concentrations of (2.4 ± 0.35) × 1011  EVs/mL and (3.0 ± 0.48) × 1011  EVs/mL (p > 0.05) were estimated by nanoparticle tracking analysis for FB and FB/CP cultures, respectively. The STR-based platform optimized herein represents a major contribution toward the development of human MSC- and MSC-EV-based products as promising therapeutic agents for Regenerative Medicine settings.

Bone marrow stromal cell-derived exosome combinate with fibrin on tantalum coating titanium implant accelerates osseointegration

This study aims to present a sustainably releasing system of exosomes-fibrin combinate loaded on tantalum-coating titanium implants. We hope to investigate potential effects of the system on osseointegration between tantalum coating titanium implants and its surrounding bone tissue. Exosomes derived from rabbit bone marrow stromal cells (rBMSCs) and fibrin were deposited onto the micro-nanostructure tantalum coating surface (Ta + exo + FI) and compared to control groups, including tantalum coating (Ta), tantalum coating loaded exosomes (Ta + exo) and tantalum coating loaded fibrin (Ta + FI). The optimal concentration of loading exosomes, exosomes uptake capacity by BMSCs, and the effect of controlled-release by fibrin were assessed by laser scanning confocal microscope (LCSM) and microplate reader. The optimal concentration of exosomes was 1 μg/μL. Adhesion, proliferation, and osteogenic differentiation ability of BMSCs on different materials were assessed in vitro. Finally, osseointegrative capacity of Ta, Ta + exo, Ta + FI, Ta + exo + FI implants in rabbit tibia were respectively evaluated with histology and bone-implant contact ratio (BIC%). It was demonstrated that exosome sustained-release system with fibrin loading on the tantalum coating was successfully established. Fibrin contribute to exosomes release extension from 2d to 6d. Furthermore, Ta + exo + FI significantly promoted adhesion, proliferation, and osteogenic differentiation of BMSCs. In vivo, the implants in Ta + exo + FI group displayed the highest osseointegrative capability than those in other groups. It is concluded that this exosome delivery system on the implants may be an effective way for tantalum coating titanium implants to promote osseointegration between implant and its surrounding bone tissue.

Microvesicle-Mediated Tissue Regeneration Mitigates the Effects of Cellular Ageing

Extracellular vesicles (EVs), comprising microvesicles (MVs) and exosomes (Exos), are membranous vesicles secreted by cells which mediate the repair of cellular and tissue damage via paracrine mechanisms. The action of EVs under normative and morbid conditions in the context of ageing remains largely unexplored. We demonstrate that MVs, but not Exos, from Pathfinder cells (PCs), a putative stem cell regulatory cell type, enhance the repair of human dermal fibroblast (HDF) and mesenchymal stem cell (MSC) co-cultures, following both mechanical and genotoxic stress. Critically, this effect was found to be both cellular age and stress specific. Notably, MV treatment was unable to repair mechanical injury in older co-cultures but remained therapeutic following genotoxic stress. These observations were further confirmed in human dermal fibroblast (HDF) and vascular smooth muscle cell (VSMC) co-cultures of increasing cellular age. In a model of comorbidity comprising co-cultures of HDFs and highly senescent abdominal aortic aneurysm (AAA) VSMCs, MV administration appeared to be senotherapeutic, following both mechanical and genotoxic stress. Our data provide insights into EVs and the specific roles they play during tissue repair and ageing. These data will potentiate the development of novel cell-free therapeutic interventions capable of attenuating age-associated morbidities and avoiding undesired effects.

Future regenerative therapies for corneal disease

PURPOSE OF REVIEW

To highlight the progress and future direction of stem-cell based regenerative therapies for the treatment of corneal disease.

RECENT FINDINGS

Corneal stem cell-based therapies, such as limbal stem cell transplantation, corneal stromal stem cell transplantation, endothelial stem cell transplantation, and stem cell-derived extracellular vesicles have demonstrated promising results in the laboratory. Although most are still in preclinical development or early phase clinical trials, these stem cell-based therapies hold potential to facilitate tissue regeneration, restore native function, and inhibit pathologic disease processes such as fibrosis, inflammation, and neovascularization.

SUMMARY

Stem cell-based therapy offers a promising therapeutic option that can circumvent several of the challenges and limitations of traditional surgical treatment. This concise review summarizes the progress in stem-cell based therapies for corneal diseases along with their history, underlying mechanisms, limitations, and future areas for development.

Challenges and strategies: Scalable and efficient production of mesenchymal stem cells-derived exosomes for cell-free therapy

Exosomes are small membrane vesicles secreted by most cell types, and widely exist in cell supernatants and various body fluids. They can transmit numerous bioactive elements, such as proteins, nucleic acids, and lipids, to affect the gene expression and function of recipient cells. Mesenchymal stem cells (MSCs) have been confirmed to be a potentially promising therapy for tissue repair and regeneration. Accumulating studies demonstrated that the predominant regenerative paradigm of MSCs transplantation was the paracrine effect but not the differentiation effect. Exosomes secreted by MSCs also showed similar therapeutic effects as their parent cells and were considered to be used for cell-free regenerative medicine. However, the inefficient and limited production has hampered their development for clinical translation. In this review, we summarize potential methods to efficiently promote the yield of exosomes. We mainly focus on engineering the process of exosome biogenesis and secretion, altering the cell culture conditions, cell expansion through 3D dynamic culture and the isolation of exosomes. In addition, we also discuss the application of MSCs-derived exosomes as therapeutics in disease treatment.

Non-Classical Intercellular Communications: Basic Mechanisms and Roles in Biology and Medicine

In multicellular organisms, interactions between cells and intercellular communications form the very basis of the organism’s survival, the functioning of its systems, the maintenance of homeostasis and adequate response to the environment. The accumulated experimental data point to the particular importance of intercellular communications in determining the fate of cells, as well as their differentiation and plasticity. For a long time, it was believed that the properties and behavior of cells were primarily governed by the interactions of secreted or membrane-bound ligands with corresponding receptors, as well as direct intercellular adhesion contacts. In this review, we describe various types of other, non-classical intercellular interactions and communications that have recently come into the limelight—in particular, the broad repertoire of extracellular vesicles and membrane protrusions. These communications are mediated by large macromolecular structural and functional ensembles, and we explore here the mechanisms underlying their formation and present current data that reveal their roles in multiple biological processes. The effects mediated by these new types of intercellular communications in normal and pathological states, as well as therapeutic applications, are also discussed. The in-depth study of novel intercellular interaction mechanisms is required for the establishment of effective approaches for the control and modification of cell properties both for basic research and the development of radically new therapeutic strategies.

Progress and expectation of stem cell therapy for diabetic wound healing

Impaired wound healing presents great health risks to diabetics. Encouragingly, the current clinical successfully found out meaningful method to repair wound tissue, and stem cell therapy could be an effective method for diabetic wound healing with its ability to accelerate wound closure and avoid amputation. This minireview aims at introducing stem cell therapy for facilitating tissue repair in diabetic wounds, discussing the possible therapeutic mechanism and clinical application status and problems.

Exosomes derived from human adipose mesenchymal stem cells ameliorate hepatic fibrosis by inhibiting PI3K/Akt/mTOR pathway and remodeling choline metabolism

Liver fibrosis is a chronic liver disease with the presence of progressive wound healing response caused by liver injury. Currently, there are no approved therapies for liver fibrosis. Exosomes derived from human adipose mesenchymal stem cells (hADMSCs-Exo) have displayed a prominent therapeutic effect on liver diseases. However, few studies have evaluated therapeutic effect of hADMSCs-Exo in liver fibrosis and cirrhosis, and its precise mechanisms of action remain unclear. Herein, we investigated anti-fibrotic efficacy of hADMSCs-Exo in vitro and in vivo, and identified important metabolic changes and the detailed mechanism through transcriptomic and metabolomic profiling. We found hADMSCs-Exo could inhibit the proliferation of activated hepatic stellate cells through aggravating apoptosis and arresting G1 phase, effectively inhibiting the expression of profibrogenic proteins and epithelial-to-mesenchymal transition (EMT) in vitro. Moreover, it could significantly block collagen deposition and EMT process, improve liver function and reduce liver inflammation in liver cirrhosis mice model. The omics analysis revealed that the key mechanism of hADMSCs-Exo anti-hepatic fibrosis was the inhibition of PI3K/AKT/mTOR signaling pathway and affecting the changes of metabolites in lipid metabolism, and mainly regulating choline metabolism. CHPT1 activated by hADMSCs-Exo facilitated formation and maintenance of vesicular membranes. Thus, our study indicates that hADMSCs-Exo can attenuate hepatic stellate cell activation and suppress the progression of liver fibrosis, which holds the significant potential of hADMSCs-Exo for use as extracellular nanovesicles-based therapeutics in the treatment of liver fibrosis and possibly other intractable chronic liver diseases.

COVID-19 plasma exosomes promote proinflammatory immune responses in peripheral blood mononuclear cells

Elevated serum cytokine production in COVID-19 patients is associated with disease progression and severity. However, the stimuli that initiate cytokine production in patients remain to be fully revealed. Virus-infected cells release virus-associated exosomes, extracellular vesicles of endocytic origin, into the blood to deliver viral cargoes able to regulate immune responses. Here, we report that plasma exosomes of COVID-19 patients contain SARS-CoV-2 double stranded RNA (dsRNA) and stimulate robust production of interleukin-6 (IL-6), IL-8, tumor necrosis factor-α (TNF-α), and other inflammatory cytokines and chemokines by human peripheral mononuclear cells. Exosome depletion abolished these stimulated responses. COVID-19 plasma exosomes induced proinflammatory responses in CD4+ T cells, CD8+ T cells, and CD14+ monocytes but not significantly in regulatory T cells, Th17 T cells, or central memory T cells. COVID-19 plasma exosomes protect the SARS-CoV-2 dsRNA cargo from RNase and deliver the dsRNA into recipient cells. These exosomes significantly increase expression of endosomal toll-like receptor 3 (TLR3), TLR7, TLR8, and TLR9 in peripheral T cells and monocytes. A pharmacological inhibitor of TLR3 considerably reduced cytokine and chemokine production by CD4+ and CD8+ T cells but not by CD14+ monocytes, highlighting divergent signaling pathways of immune cells in response to COVID-19 plasma exosomes. Our results identify a novel model of intercellular crosstalk following SARS-CoV-2 infection that evoke immune responses positioned to contribute to elevated cytokine production associated with COVID-19 progression, severity, and long-haul symptoms.

Heterogeneity of mesenchymal stem cell-derived extracellular vesicles is highly impacted by the tissue/cell source and culture conditions

Extracellular vesicles (EVs) are cell-derived membrane structures exerting major effects in physiological as well as pathological processes by functioning as vehicles for the delivery of biomolecules to their target cells. An increasing number of effects previously attributed to cell-based therapies have been recognized to be actually mediated by EVs derived from the respective cells, suggesting the administration of purified EVs instead of living cells for cell-based therapies. In this review, we focus on the heterogeneity of EVs derived from mesenchymal stem/stromal cells (MSC) and summarize upstream process parameters that crucially affect the resulting therapeutic properties and biological functions. Hereby, we discuss the effects of the cell source, medium composition, 3D culture, bioreactor culture and hypoxia. Furthermore, aspects of the isolation and storage strategies influences EVs are described. Conclusively, optimization of upstream process parameters should focus on controlling MSC-derived EV heterogeneity for specific therapeutic applications.

Graphical Abstract

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Extracellular vesicle therapy for traumatic central nervous system disorders

Traumatic central nervous system (CNS) disorders have catastrophic effects on patients, and, currently, there is no effective clinical treatment. Cell transplantation is a common treatment for traumatic CNS injury in animals. In recent years, an increasing number of studies have reported that the beneficial effect of transplanted cells for CNS repair is mediated primarily through the extracellular vesicles (EVs) secreted by the cells, in which microRNAs play a major role. Accordingly, numerous studies have evaluated the roles and applications of EVs secreted by different cell types in neurological diseases. Furthermore, due to their unique biological features, EVs are used as disease biomarkers and drug delivery systems for disease prevention and treatment. We discuss current knowledge related to EVs, focusing on the mechanism underlying their effects on traumatic CNS diseases, and summarize existing research on the potential clinical utility of EVs as disease biomarkers and drug delivery systems.

Superior therapeutic activity of TGF-β-induced extracellular vesicles against interstitial cystitis

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic disease characterized by incapacitating pelvic pain. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are considered key mediators of the paracrine action of MSCs and show better biological activities than the parent MSCs, especially in the bladder tissue, which may be unfavorable for MSC survival. Here, we produced MSC-EVs using advanced three-dimensional (a3D) culture with exogenous transforming growth factor-β3 (TGF-β3) (T-a3D-EVs). Treatment with T-a3D-EVs led to significantly enhanced wound healing and anti-inflammatory capacities. Moreover, submucosal layer injection of T-a3D-EVs in chronic IC/BPS animal model resulted in restoration of bladder function, superior anti-inflammatory activity, and recovery of damaged urothelium compared to MSCs. Interestingly, we detected increased TGF-β1 level in T-a3D-EVs, which might be involved in the anti-inflammatory activity of these EVs. Taken together, we demonstrate the excellent immune-modulatory and regenerative abilities of T-a3D-EVs as observed by recovery from urothelial denudation and dysfunction, which could be a promising therapeutic strategy for IC/BPS.

Human Cardiac Progenitor Cell-Derived Extracellular Vesicles Exhibit Promising Potential for Supporting Cardiac Repair in Vitro

Although human Cardiac Progenitor Cells (hCPCs) are not retained by host myocardium they still improve cardiac function when injected into ischemic heart. Emerging evidence supports the hypothesis that hCPC beneficial effects are induced by paracrine action on resident cells. Extracellular vesicles (EVs) are an intriguing mechanism of cell communication based on the transport and transfer of peptides, lipids, and nucleic acids that have the potential to modulate signaling pathways, cell growth, migration, and proliferation of recipient cells. We hypothesize that EVs are involved in the paracrine effects elicited by hCPCs and held accountable for the response of the infarcted myocardium to hCPC-based cell therapy. To test this theory, we collected EVs released by hCPCs isolated from healthy myocardium and evaluated the effects they elicited when administered to resident hCPC and cardiac fibroblasts (CFs) isolated from patients with post-ischemic end-stage heart failure. Evidence emerging from our study indicated that hCPC-derived EVs impacted upon proliferation and survival of hCPCs residing in the ischemic heart and regulated the synthesis and deposition of extracellular-matrix by CFs. These findings suggest that beneficial effects exerted by hCPC injection are, at least to some extent, ascribable to the delivery of signals conveyed by EVs.

The Secretome of Preconditioned Mesenchymal Stem Cells Drives Polarization and Reprogramming of M2a Macrophages toward an IL-10-Producing Phenotype

The preconditioning of mesenchymal stem cells (MSCs) has been recognized as an attractive tool to improve their regenerative and immunomodulatory capacities based on their paracrine effects. In this study, we examined the potential of an MSC-conditioned medium (MSC-CM) to alter the phenotype of murine macrophages and to drive reprogramming toward an anti-inflammatory, M2-like state in vitro. We further explored the impact of MSC cytokine preconditioning on the immunosuppressive properties of the MSC secretome. The MSC-CM suppressed the expression of proinflammatory genes in murine M1 macrophages, but only the CM from preconditioned MSCs (preMSC-CM) downregulated their expression during M1 polarization. Remarkably, only the preMSC-CM significantly increased the expression of M2a-, M2b- and M2c-specific genes and proteins during M2a polarization. Further, macrophages were found to secrete high levels of anti-inflammatory IL-10. Similarly, M2a macrophages cultured in the presence of the preMSC-CM displayed an enhanced expression of M2b/M2c-specific markers, suggesting that the secretome of preMSC promotes the repolarization of M2a-like macrophages to M2b/M2c subtypes. The preMSC-CM was found to be enriched in molecules involved in M2 polarization. Additionally, a unique downregulation of extracellular matrix components was observed. Altogether, the preMSC-CM may provide an attractive strategy to dampen inflammation by suppressing the expression of proinflammatory mediators and promoting the polarization and phenotype switch of M2a cells to IL-10-secreting M2b/M2c-like macrophages.

Algal Cells-Derived Extracellular Vesicles: A Review With Special Emphasis on Their Antimicrobial Effects

Extracellular vesicles (EVs) originated from different cells of approximately all kinds of organisms, recently got more attention because of their potential in the treatment of diseases and reconstructive medicine. To date, lots of studies have been performed on mammalian-derived vesicles, but little attention has been paid to algae and marine cells as valuable sources of EVs. Proving the promising role of EVs in medicine requires sufficient resources to produce qualified microvesicles. Algae, same as its other sister groups, such as plants, have stem cells and stem cell niches. Previous studies showed the EVs in plants and marine cells. So, this study was set out to talk about algal extracellular vesicles. EVs play a major role in cell-to-cell communication to convey molecules, such as RNA/DNA, metabolites, proteins, and lipids within. The components of EVs depends on the origin of the primitive cells or tissues and the isolation method. Sufficient resources are needed to produce high-quality, stable, and compatible EVs as a drug or drug delivery system. Plant stem cells have great potential as a new controllable resource for the production of EVs. The EVs secreted from stem cells can easily be extracted from the cell culture medium and evaluated for medicinal uses. In this review, the aim is to introduce algae stem cells as well as EVs derived from algal cells. In the following, the production of the EVs¸ the properties of EVs extracted from these sources and their antimicrobial effects will be discussed.

Research progress on the mechanism of beta-cell apoptosis in type 2 diabetes mellitus

Type 2 diabetes mellitus(T2DM) is regarded as one of the most severe chronic metabolic diseases worldwide, which poses a great threat to human safety and health. The main feature of T2DM is the deterioration of pancreatic beta-cell function. More and more studies have shown that the decline of pancreatic beta-cell function in T2DM can be attributable to beta-cell apoptosis, but the exact mechanisms of beta-cell apoptosis in T2DM are not yet fully clarified. Therefore, in this review, we will focus on the current status and progress of research on the mechanism of pancreatic beta-cell apoptosis in T2DM, to provide new ideas for T2DM treatment strategies.

The impact of obesity on adipocyte-derived extracellular vesicles

Recently, the emerging roles of adipocyte-derived extracellular vesicles (EVs) linking obesity and its comorbidities have been recognized. In obese subjects, adipocytes are having hypertrophic growth and are under stressed. The dysfunction adipocytes dysregulate the assembly of the biological components in the EVs including exosomes. This article critically reviews the current findings on the impact of obesity on the exosomal cargo contents that induce the pathophysiological changes. Besides, this review also summarizes the understanding on how obesity affects the biogenesis of adipocyte-derived exosomes and the exosome secretion. Furthermore, the differences of the exosomal contents in different adipose depots, and the impact of obesity on the exosomes that are derived from the stromal vascular fraction such as the adipose tissue macrophages and adipocyte-derived stem cells will also be discussed. The current development and potential application of exosome-based therapy will be summarized. This review provides crucial information for the design of novel exosome-based therapy for the treatment of obesity and its comorbidities.

Recent trends in therapeutic strategies for repairing endometrial tissue in intrauterine adhesion

Intrauterine adhesion (IUA) is a common gynaecological disease that develops from infection or trauma. IUA disease may seriously affect the physical and mental health of women of childbearing age, which may lead to symptoms such as hypomenorrhea or infertility. Presently, hysteroscopic transcervical resection of adhesion (TCRA) is the principal therapy for IUAs, although its function in preventing the recurrence of adhesion and preserving fertility is limited. Pharmaceuticals such as hormones and vasoactive agents and the placement of nondegradable stents are the most common postoperative adjuvant therapy methods. However, the repair of injured endometrium is relatively restricted due to the different anatomical structures of the endometrium. Recently, the treatment outcome of IUAs has improved with the advancement of hysteroscopic techniques. In particular, the application of bioactive scaffolds combined with tissue engineering technology has proven to have high therapeutic potential or endometrial repair in IUA treatment. Herein, this review has summarized past therapeutic strategies, including postoperative adjuvant therapy, cell or therapeutic molecular delivery therapy methods and bioactive scaffold-based tissue engineering methods. Therefore, this review presented the recent therapeutic strategies for repairing endometrium treatment and pointed out the issues of clinical concern to provide alternative methods for the management of IUAs.

Exosomes from adipose-derived mesenchymal stem cells alleviate liver ischaemia reperfusion injury subsequent to hepatectomy in rats by regulating mitochondrial dynamics and biogenesis

Hepatic ischaemia reperfusion injury (HIRI) is a major factor leading to liver dysfunction after liver resection and liver transplantation. Adipose-derived mesenchymal stem cells (ADSCs) have potential therapeutic effects on HIRI. Exosomes derived from ADSCs (ADSCs-exo) have been widely studied as an alternative of ADSCs therapy. Thus, the aim of this study was to evaluate the potential protective effect and related mechanism of ADSCs-exo on HIRI subsequent to hepatectomy. Rats were randomly divided into four groups: Sham, I30R+PH, ADSCs and ADSCs-exo group. After 24 h of reperfusion, liver and serum of the rats were immediately collected. ADSCs-exo improved liver function, inhibited oxidative stress and reduced apoptosis of hepatocytes in HIRI subsequent to hepatectomy in rats. ADSCs-exo significantly promoted the recovery of mitochondrial function, markedly increased the content of ATP in the liver tissue, and improved the ultrastructure of mitochondria in hepatocytes. Moreover, ADSCs-exo significantly increased the expression of OPA-1, MFN-1 and MFN-2 proteins related to mitochondrial fusion, while DRP-1 and Fis-1 mRNA and protein expression associated with mitochondrial fission were significantly decreased after the treatment with ADSCs-exo. In addition, ADSCs-exo significantly increased the expression of PGC-1α, NRF-1 and TFAM genes and proteins related to mitochondrial biogenesis. ADSCs-exo improves liver function induced by HIRI subsequent to hepatectomy in rats and maintains mitochondrial homeostasis by inhibiting mitochondrial fission, promoting mitochondrial fusion and promoting mitochondrial biogenesis. Therefore, ADSCs-exo may be considered as a potential promising alternative to ADSCs in the treatment of HIRI subsequent to hepatectomy.

Human limbal epithelial stem cell regulation, bioengineering and function

The corneal epithelium is continuously renewed by limbal stem/progenitor cells (LSCs), a cell population harbored in a highly regulated niche located at the limbus. Dysfunction and/or loss of LSCs and their niche cause limbal stem cell deficiency (LSCD), a disease that is marked by invasion of conjunctival epithelium into the cornea and results in failure of epithelial wound healing. Corneal opacity, pain, loss of vision, and blindness are the consequences of LSCD. Successful treatment of LSCD depends on accurate diagnosis and staging of the disease and requires restoration of functional LSCs and their niche. This review highlights the major advances in the identification of potential LSC biomarkers and components of the LSC niche, understanding of LSC regulation, methods and regulatory standards in bioengineering of LSCs, and diagnosis and staging of LSCD. Overall, this review presents key points for researchers and clinicians alike to consider in deepening the understanding of LSC biology and improving LSCD therapies.

Human liver stem cell-derived extracellular vesicles reduce injury in a model of normothermic machine perfusion of rat livers previously exposed to a prolonged warm ischemia

Livers from donors after circulatory death (DCD) are a promising option to increase the donor pool, but their use is associated with higher complication rate and inferior graft survival. Normothermic machine perfusion (NMP) keeps the graft at 37°C, providing nutrients and oxygen supply. Human liver stem cell‐derived extracellular vesicles (HLSC‐EVs) are able to reduce liver injury and promote regeneration. We investigated the efficacy of a reconditioning strategy with HLSC‐EVs in an experimental model of NMP. Following total hepatectomy, rat livers were divided into 4 groups: (i) healthy livers, (ii) warm ischemic livers (60 min of warm ischemia), (iii) warm ischemic livers treated with 5 × 10⁸ HLSC‐EVs/g‐liver, and (iv) warm ischemic livers treated with a 25 × 10⁸ HLSC‐EVs/g‐liver. NMP lasted 6 h and HLSC‐EVs (Unicyte AG, Germany) were administered within the first 15 min. Compared to controls, HLSC‐EV treatment significantly reduced transaminases release. Moreover, HLSC‐EVs enhanced liver metabolism by promoting phosphate utilization and pH self‐regulation. As compared to controls, the higher dose of HLSC‐EV was associated with significantly higher bile production and lower intrahepatic resistance. Histologically, this group showed reduced necrosis and enhanced proliferation. In conclusion, HLSC‐EV treatment during NMP was feasible and effective in reducing injury in a DCD model with prolonged warm ischemia.

Extracellular vesicle therapeutics from plasma and adipose tissue

Extracellular vesicles (EVs) are cell-released lipid-bilayer nanoparticles that contain biologically active cargo involved in physiological and pathological intercellular communication. In recent years, the therapeutic potential of EVs has been explored in various disease models. In particular, mesenchymal stromal cell-derived EVs have been shown to exert anti-inflammatory, anti-oxidant, anti-apoptotic, and pro-angiogenic properties in cardiovascular, metabolic and orthopedic conditions. However, a major drawback of EV-based therapeutics is scale-up issues due to extensive cell culture requirements and inefficient isolation protocols. An emerging alternative approach to time-consuming and costly cell culture expansion is to obtain therapeutic EVs directly from the body, for example, from plasma and adipose tissue. This review discusses isolation methods and therapeutic applications of plasma and adipose tissue-derived EVs, highlighting advantages and disadvantages compared to cell culture-derived ones.

The Role of MSC in Wound Healing, Scarring and Regeneration

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.

The Use of Mesenchymal Stem Cells and their Derived Extracellular Vesicles in Cardiovascular Disease Treatment

BACKGROUND

Cardiovascular disease (CVD), including disorders of cardiac muscle and vascular, is the major cause of death globally. Many unsuccessful attempts have been made to intervene in the disease's pathogenesis and treatment. Stem cell-based therapies, as a regeneration strategy, cast a new hope for CVD treatment. One of the most well-known stem cells is mesenchymal stem cells (MSCs), classified as one of the adult stem cells and can be obtained from different tissues. These cells have superior properties, such as proliferation and highly specialized differentiation. On the other hand, they have the potential to modulate the immune system and anti-inflammatory activity. One of their most important features is the secreting the extracellular vesicles (EVs) like exosomes (EXOs) as an intercellular communication system mediating the different physiological and pathophysiological affairs.

METHODS

In this review study, the importance of MSC and its secretory exosomes for the treatment of heart disease has been together and specifically addressed and the use of these promising natural and accessible agents is predicted to replace the current treatment modalities even faster than we imagine.

RESULTS

MSC derived EXOs by providing a pro-regenerative condition allowing innate stem cells to repair damaged tissues successfully. As a result, MSCs are considered as the appropriate cellular source in regenerative medicine. In the plethora of experiments, MSCs and MSC-EXOs have been used for the treatment and regeneration of heart diseases and myocardial lesions.

CONCLUSION

Administration of MSCs has been provided a replacement therapeutic option for heart regeneration, obtaining great attention among the basic researcher and the medical doctors.

Proficiency of Carboxymethylcellulose as a Cryoprotectant. Clinical and Histological Evaluation of Cryopreserved Heterogenous Mesenchymal Stem Cell-Exosomal Hydrogel on Critical Size Skin Wounds in Dogs

Background: Fresh stem cell exosomes are usually obtained and reused in the same individual. It cannot be kept viable for a long period of time regardless of the lengthy preparation time. Freezing is typically used to preserve the viability of perishable materials and increase their lifetime. Regrettably, normal freezing of biomaterials leads to cell damage. Therefore, a cryoprotectant can save the cells from the conventional cryodamage. Sodium carboxymethylcellulose (NA-CMC) is a powdery substance that is used to manufacture bio-safe hydrofilm gels because of its high viscosity, cytocompatibility, and nonallergenic nature.

Materials and Methods: Sterile CMC hydrogel was prepared, part of which was loaded with exosomal solution derived from MSCs. The gel was kept at −20°C for preservation. Two bilateral full-thickness circular skin wounds of 2-cm diameter were created on the back of experimental dogs. The wounds were at least 2.5 cm apart. Treatment started 24 hours after wound creation. Group I received CMC gel solely, whereas group II received frozen CMC exosomal gel. The gel was applied 4 times, a single application per day with 1- day interval.

Results: Clinically, the frozen exosomal gel significantly promoted wound healing with no scaring. Histologically, enhanced dermal fibroblasts and organized collagen deposition were seen in the treated group.

Conclusion: CMC proved to be an efficient cryoprotectant and a suitable vehicle for exosomes. Deep freezing was proven to conserve the viability, extended the preservation, and facilitated the usage of exosomal gel. This technique of preserved cell-free therapy is inexpensive, time-saving, and proficient and seems suitable for treating cutaneous wounds.

Protective Effect of Membrane-Free Stem Cells against Lipopolysaccharide and Interferon-Gamma-Stimulated Inflammatory Responses in RAW 264.7 Macrophages

Recently, adipose-derived stem cells (ADSCs) are considered to be ideal for application in cell therapy or tissue regeneration, mainly due to their wide availability and easy access. In this study, we examined the anti-inflammatory effects of membrane-free stem cell extract (MFSC-Ex) derived from ADSCs against lipopolysaccharide (LPS)/interferon-gamma (IFN-γ) on RAW 264.7 macrophage cells. Exposure of RAW macrophages to LPS and IFN-γ stimuli induced high levels of nitric oxide (NO), cyclooxygenase-2 (COX-2), and prostaglandin E₂ (PGE₂) production. However, pretreatment with MFSC-Ex inhibited LPS/IFN-γ-induced these pro-inflammatory mediators. To clarify the molecular mechanisms underlying the anti-inflammatory property of MFSC-Ex, we analyzed nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) protein expressions by Western blotting. Our study showed that treatment of MFSC-Ex significantly down-regulated inducible nitric oxide synthase (iNOS) and COX-2 protein expressions. Furthermore, phosphorylation of extracellular signal-regulated kinase (ERK) and p38 was also blocked by treatment with MFSC-Ex, indicating that inhibitory effect of MFSC-Ex on MAPK signaling cascade may attribute to inactivation of NF-κB. From these findings, we suggest that MFSC-Ex exert anti-inflammatory activities, which suppressed LPS/IFN-γ-induced production of NO, COX-2 and PGE₂ by regulation of NF-κB and MAPK signaling pathway in RAW 264.7 macrophages. In conclusion, MFSC-Ex might provide a new therapeutic opportunity to treatment of inflammatory-related diseases.

A Chemically Defined, Xeno- and Blood-Free Culture Medium Sustains Increased Production of Small Extracellular Vesicles From Mesenchymal Stem Cells

Cell therapy is witnessing a notable shift toward cell-free treatments based on paracrine factors, in particular, towards small extracellular vesicles (sEV), that mimic the functional effect of the parental cells. While numerous sEV-based applications are currently in advanced preclinical stages, their promised translation depends on overcoming the manufacturing hurdles posed by the large-scale production of purified sEV. Unquestionably, the culture medium used with the parental cells plays a key role in the sEV's secretion rate and content. An essential requisite is the use of a serum-, xeno-, and blood-free medium to meet the regulatory entity requirements of clinical-grade sEV's production. Here, we evaluated Oxium^TMEXO, a regulatory complying medium, with respect to production capacity and conservation of the EV's characteristics and functionality and the parental cell's phenotype and viability. A comparative study was established with standard DMEM and a commercially available culture medium developed specifically for sEV production. Under similar conditions, Oxium^TMEXO displayed a three-fold increase of sEV secretion, with an enrichment of particles ranging between 51 and 200 nm. These results were obtained through direct quantification from the conditioned medium to avoid the isolation method's interference and variability and were compared to the two culture media under evaluation. The higher yield obtained was consistent with several harvest time points (2, 4, and 6 days) and different cell sources, incluiding umbilical cord-, menstrual blood-derived mesenchymal stromal cells and fibroblasts. Additionally, the stem cell phenotype and viability of the parental cell remained unchanged. Furthermore, Oxium^TMEXO-sEV showed a similar expression pattern of the vesicular markers CD63, CD9, and CD81, with respect to sEV derived from the other conditions. The in vitro internalization assays in different target cell types and the pharmacokinetic profile of intraperitoneally administered sEV in vivo indicated that the higher EV production rate did not affect the uptake kinetics or the systemic biodistribution in healthy mice. In conclusion, the Oxium^TMEXO medium sustains an efficient and robust production of large quantities of sEV, conserving the classic functional properties of internalization into acceptor target cells and biodistribution in vivo, supplying the amount and quality of EVs for the development of cell-free therapies.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Protect Human Corneal Endothelial Cells from Endoplasmic Reticulum Stress-Mediated Apoptosis

Corneal endothelial dystrophy is a relevant cause of vision loss and corneal transplantation worldwide. In the present study, we analyzed the effect of mesenchymal stem cell (MSC)-derived extracellular vesicles (MSC-EVs) in an in vitro model of corneal dystrophy, characterized by endoplasmic reticulum stress. The effects of MSC-EVs were compared with those of serum-derived EVs, reported to display a pro-angiogenic activity. MSC-EVs were able to induce a significant down-regulation of the large majority of endoplasmic reticulum stress-related genes in human corneal endothelial cells after exposure to serum deprivation and tunicamycin. In parallel, they upregulated the Akt pathway and limited caspase-3 activation and apoptosis. At variance, the effect of the serum EVs was mainly limited to Akt phosphorylation, with minimal or absent effects on endoplasmic reticulum stress modulation and apoptosis prevention. The effects of MSC-EVs were correlated to the transfer of numerous endoplasmic reticulum (ER)-stress targeting miRNAs to corneal endothelial cells. These data suggest a potential therapeutic effect of MSC-EVs for corneal endothelial endoplasmic reticulum stress, a major player in corneal endothelial dystrophy.

MicroRNAs in the regulation of autophagy and their possible use in age-related macular degeneration therapy

Age-related macular degeneration (AMD) is a progressive sight-impairing disease of the elderly. The pathogenic mechanisms of AMD are not well understood although both genetic and many environmental factors have been associated with the development of AMD. One clinical hallmark of AMD is the detrimental aggregation of damaged proteins. Recently, it has been suggested that the weakening of autophagy clearance is an important mechanism in the pathogenesis of AMD. Autophagy is important in the removal of damaged or no longer needed cellular material and its recycling. A considerable number of autophagy-targeting microRNAs (miRNAs), small RNA molecules and epigenetic regulators have been found to be either up- or down-regulated in AMD patients and experimental models. The important role of autophagy-targeting miRNAs is supported by several studies and can open the prospect of the use of these miRNAs in the therapy for AMD.

Mesenchymal Stem Cells for the Treatment of Liver Disease: Present and Perspectives

Mesenchymal stem cell transplantation is an emerging therapy for treating chronic liver diseases. The potential of this treatment has been evaluated in preclinical and clinical studies. Although the mechanisms of mesenchymal stem cell transplantation are still not completely understood, accumulating evidence has revealed that their immunomodulation, differentiation, and antifibrotic properties play a crucial role in liver regeneration. The safety and therapeutic effects of mesenchymal stem cells in patients with chronic liver disease have been observed in many clinical studies. However, only modest improvements have been seen, partly because of the limited feasibility of transplanted cells at present. Here, we discuss several strategies targeted at improving viable cell engraftment and the potential challenges in the use of extracellular vesicle-based therapies for liver disease in the future.

The protective effects of human umbilical cord mesenchymal stem cell-derived extracellular vesicles on cisplatin-damaged granulosa cells

OBJECTIVE

Long term exposure to gonadotoxic chemotherapy is becoming a major cause of premature ovarian failure/insufficiency (POF/POI) with the increasing cancer incidence among young women. The present study was designed to investigate the protective effects of human cord mesenchymal stem cells (HUCMSCs)-derived extracellular vesicles (EVs) on cisplatin (CDDP)-damaged granulosa cells (GCs) in vitro.

MATERIALS AND METHODS

EVs were obtained from supernatant of cultured HUCMSCs by ultracentrifugation method, purified by Sucrose density gradient centrifugation, and then were co-cultured with cisplatin-damaged GCs of 3-weeks female Sprague-Dawley (SD) rats. PKH26 labeled EVs could be observed in normal and CDDP-damaged GCs after 6 h co-culture.

RESULTS

The surviving GCs were significantly higher and apoptotic GCs were significantly lower in EVs + CDDP group compared with CDDP group. Meanwhile, the levels of E2 and StAR (the key gene related to synthesis of steroid hormone) were significantly higher in EVs + CDDP group compared with CDDP group. Furthermore, the mRNA expression of Caspase 3 was down-regulated significantly and the ratio of Bcl-2/Bax was up-regulated significantly in EVs + CDDP group. Moreover, the protective effect of EVs on CDDP-damaged GCs showed a dose-dependent effect.

CONCLUSION

HUCMSCs-derived EVs could become incorporated to CDDP-damaged GCs, and increase the number of living cells, therefore playing important roles in promoting resistance to cisplatin-induced GCs apoptosis and restoring synthesis and secretion of steroid hormone in GCs. This study might provide a theoretical and experimental basis for use of mesenchymal stem cells (MSCs) derived EVs instead of MSCs as a cell-free therapeutic strategy for the patients with POI induced by chemotherapeutic agents.

Effects of Mesenchymal Stromal Cell-Derived Extracellular Vesicles in Lung Diseases: Current Status and Future Perspectives

Mesenchymal stromal cells (MSCs) as a kind of pluripotent adult stem cell have shown great therapeutic potential in relation to many diseases in anti-inflammation and regeneration. The results of preclinical experiments and clinical trials have demonstrated that MSC-derived secretome possesses immunoregulatory and reparative abilities and that this secretome is capable of modulating innate and adaptive immunity and reprograming the metabolism of recipient cells via paracrine mechanisms. It has been recognized that MSC-derived secretome, including soluble proteins (cytokines, chemokines, growth factors, proteases), extracellular vesicles (EVs) and organelles, plays a key role in tissue repair and regeneration in bronchopulmonary dysplasia, acute respiratory distress syndrome (ARDS), bronchial asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension, and silicosis. This review summarizes the known functions of MSC-EV modulation in lung diseases, coupled with the future challenges of MSC-EVs as a new pharmaceutical agent. The identification of underlying mechanisms for MSC-EV might provide a new direction for MSC-centered treatment in lung diseases.Graphical abstract.

Circulating Exosomes Are Strongly Involved in SARS-CoV-2 Infection

Knowledge of the host response to the novel coronavirus SARS-CoV-2 remains limited, hindering the understanding of COVID-19 pathogenesis and the development of therapeutic strategies. During the course of a viral infection, host cells release exosomes and other extracellular vesicles carrying viral and host components that can modulate the immune response. The present study used a shotgun proteomic approach to map the host circulating exosomes’ response to SARS-CoV-2 infection. We investigated how SARS-CoV-2 infection modulates exosome content, exosomes’ involvement in disease progression, and the potential use of plasma exosomes as biomarkers of disease severity. A proteomic analysis of patient-derived exosomes identified several molecules involved in the immune response, inflammation, and activation of the coagulation and complement pathways, which are the main mechanisms of COVID-19–associated tissue damage and multiple organ dysfunctions. In addition, several potential biomarkers—such as fibrinogen, fibronectin, complement C1r subcomponent and serum amyloid P-component—were shown to have a diagnostic feature presenting an area under the curve (AUC) of almost 1. Proteins correlating with disease severity were also detected. Moreover, for the first time, we identified the presence of SARS-CoV-2 RNA in the exosomal cargo, which suggests that the virus might use the endocytosis route to spread infection. Our findings indicate circulating exosomes’ significant contribution to several processes—such as inflammation, coagulation, and immunomodulation—during SARS-CoV-2 infection. The study’s data are available via ProteomeXchange with the identifier PXD021144.

Therapeutic Potential of Mesenchymal Stromal Cells and Extracellular Vesicles in the Treatment of Radiation Lesions-A Review

Ionising radiation-induced normal tissue damage is a major concern in clinic and public health. It is the most limiting factor in radiotherapy treatment of malignant diseases. It can also cause a serious harm to populations exposed to accidental radiation exposure or nuclear warfare. With regard to the clinical use of radiation, there has been a number of modalities used in the field of radiotherapy. These includes physical modalities such modified collimators or fractionation schedules in radiotherapy. In addition, there are a number of pharmacological agents such as essential fatty acids, vasoactive drugs, enzyme inhibitors, antioxidants, and growth factors for the prevention or treatment of radiation lesions in general. However, at present, there is no standard procedure for the treatment of radiation-induced normal tissue lesions. Stem cells and their role in tissue regeneration have been known to biologists, in particular to radiobiologists, for many years. It was only recently that the potential of stem cells was studied in the treatment of radiation lesions. Stem cells, immediately after their successful isolation from a variety of animal and human tissues, demonstrated their likely application in the treatment of various diseases. This paper describes the types and origin of stem cells, their characteristics, current research, and reviews their potential in the treatment and regeneration of radiation induced normal tissue lesions. Adult stem cells, among those mesenchymal stem cells (MSCs), are the most extensively studied of stem cells. This review focuses on the effects of MSCs in the treatment of radiation lesions.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles in Lung Diseases: Current Status and Perspectives

Extracellular vesicles (EVs) have emerged as a potential therapy for several diseases. These plasma membrane-derived fragments are released constitutively by virtually all cell types-including mesenchymal stromal cells (MSCs)-under stimulation or following cell-to-cell interaction, which leads to activation or inhibition of distinct signaling pathways. Based on their size, intracellular origin, and secretion pathway, EVs have been grouped into three main populations: exosomes, microvesicles (or microparticles), and apoptotic bodies. Several molecules can be found inside MSC-derived EVs, including proteins, lipids, mRNA, microRNAs, DNAs, as well as organelles that can be transferred to damaged recipient cells, thus contributing to the reparative process and promoting relevant anti-inflammatory/resolutive actions. Indeed, the paracrine/endocrine actions induced by MSC-derived EVs have demonstrated therapeutic potential to mitigate or even reverse tissue damage, thus raising interest in the regenerative medicine field, particularly for lung diseases. In this review, we summarize the main features of EVs and the current understanding of the mechanisms of action of MSC-derived EVs in several lung diseases, such as chronic obstructive pulmonary disease (COPD), pulmonary infections [including coronavirus disease 2019 (COVID-19)], asthma, acute respiratory distress syndrome (ARDS), idiopathic pulmonary fibrosis (IPF), and cystic fibrosis (CF), among others. Finally, we list a number of limitations associated with this therapeutic strategy that must be overcome in order to translate effective EV-based therapies into clinical practice.