Mesenchymal stem cells derived from human induced pluripotent stem cells modulate T-cell phenotypes in allergic rhinitis

Small extracellular vesicles derived from human mesenchymal stem cells prevent Th17-dominant neutrophilic airway inflammation via immunoregulation on Th17 cells

Type 17 helper T cells (Th17)-dominant neutrophilic airway inflammation is critical in the pathogenesis of steroid-resistant airway inflammation such as severe asthma. Small extracellular vesicles (sEV) derived from human mesenchymal stem cells (MSCs) display extensive therapeutic effects and advantages in many diseases. However, the role of MSC-sEV in Th17-dominant neutrophilic airway inflammation and the related mechanisms are still poorly studied. Here we found that MSC-sEV significantly alleviated the infiltration of inflammatory cells in peribronchial interstitial tissues and reduced levels of inflammatory cells, especially neutrophils, in bronchoalveolar lavage fluids (BALF) of mice with neutrophilic airway inflammation. Consistently, MSC-sEV significantly decreased levels of IL-17A in BALF and Th17 in lung tissues. Furthermore, we found that labelled MSC-sEV were taken up by human CD4+ T cells most obviously at 12 h after incubation, and distributed mostly in mouse lungs. More importantly, potential signaling pathways involved in the MSC-sEV mediated inhibition of Th17 polarization were found using RNA sequencing. Using Western blot, JAK2-STAT3 pathway was identified as an important role in the inhibition of Th17 polarization by MSC-sEV. We found that proteins in MSC-sEV were mostly involved in the therapeutic effects of MSC-sEV. In total, our study suggested that MSC-sEV could be a potential therapeutic strategy for the treatment of neutrophilic airway inflammation.

Imbalance of Th1 and Th2 Cytokines and Stem Cell Therapy in Pathological Pain

The pathophysiological importance of T helper 1 (Th1) and Th2 cell cytokines in pathological pain has been highly debated in recent decades. However, the analgesic strategy targeting individual cytokines still has a long way to go for clinical application. In this review, we focus on the contributions of Th1 cytokines (TNF-α, IFN-γ, and IL-2) and Th2 cytokines (IL-4, IL-5, IL-10, and IL-13) in rodent pain models and human pain-related diseases. A large number of studies have shown that Th1 and Th2 cytokines have opposing effects on pain modulation. The imbalance of Th1 and Th2 cytokines might determine the final effect of pain generation or inhibition. However, increasing evidence indicates that targeting the individual cytokine is not sufficient for the treatment of pathological pain. It is practical to suggest a promising therapeutic strategy against the combined effects of Th1 and Th2 cytokines. We summarize the current advances in stem cell therapy for pain-related diseases. Preclinical and clinical studies show that stem cells inhibit proinflammatory cytokines and release enormous Th2 cytokines that exhibit a strong analgesic effect. Therefore, a shift of the imbalance of Th1 and Th2 cytokines induced by stem cells will provide a novel therapeutic strategy against intractable pain. It is extremely important to reveal the cellular and molecular mechanisms of stem cell-mediated analgesia. The efficiency and safety of stem cell therapy should be carefully evaluated in animal models and patients with pathological pain.

The expression mechanism of programmed cell death 1 ligand 1 and its role in immunomodulatory ability of mesenchymal stem cells

Programmed cell death 1 ligand 1 (PD-L1) is an important immunosuppressive molecule, which inhibits the function of T cells and other immune cells by binding to the receptor programmed cell death-1. The PD-L1 expression disorder plays an important role in the occurrence, development, and treatment of sepsis or other inflammatory diseases, and has become an important target for the treatment of these diseases. Mesenchymal stem cells (MSCs) are a kind of pluripotent stem cells with multiple differentiation potential. In recent years, MSCs have been found to have a strong immunosuppressive ability and are used to treat various inflammatory insults caused by hyperimmune diseases. Moreover, PD-L1 is deeply involved in the immunosuppressive events of MSCs and plays an important role in the treatment of various diseases. In this review, we will summarize the main regulatory mechanism of PD-L1 expression, and discuss various biological functions of PD-L1 in the immune regulation of MSCs.

Mesenchymal stem cells overexpressing interleukin-10 prevent allergic airway inflammation

BACKGROUNDS

Allergic airway inflammation is prevalent worldwide and imposes a considerable burden on both society and affected individuals. This study aimed to investigate the therapeutic advantages of mesenchymal stem cells (MSCs) overexpressed interleukin-10 (IL-10) for the treatment of allergic airway inflammation, as both IL-10 and MSCs possess immunosuppressive properties.

METHODS

Induced pluripotent stem cell (iPSC)-derived MSCs were engineered to overexpress IL-10 via lentiviral transfection (designated as IL-10-MSCs). MSCs and IL-10-MSCs were administered intravenously to mice with allergic inflammation induced by ovalbumin (OVA), and the features of allergic inflammation including inflammatory cell infiltration, Th cells in the lungs, and T helper 2 cell (Th2) cytokine levels in bronchoalveolar lavage fluid (BALF) were examined. MSCs and IL-10-MSCs were co-cultured with CD4+ T cells from patients with allergic rhinitis (AR), and the levels of Th2 cells and corresponding type 2 cytokines were studied. RNA-sequence was performed to further investigate the potential effects of MSCs and IL-10-MSCs on CD4+ T cells.

RESULTS

Stable IL-10-MSCs were established and characterised by high IL-10 expression. IL-10-MSCs significantly reduced inflammatory cell infiltration and epithelial goblet cell numbers in the lung tissues of mice with allergic airway inflammation. Inflammatory cell and cytokine levels in BALF also decreased after the administration of IL-10-MSCs. Moreover, IL-10-MSCs showed a stronger capacity to inhibit the levels of Th2 after co-cultured with CD4+ T cells from patients with AR. Furthermore, we elucidated lower levels of IL-5 and IL-13 in IL-10-MSCs treated CD4+ T cells, and blockade of IL-10 significantly reversed the inhibitory effects of IL-10-MSCs. We also reported the mRNA profiles of CD4+ T cells treated with IL-10-MSCs and MSCs, in which IL-10 played an important role.

CONCLUSION

IL-10-MSCs showed positive effects in the treatment of allergic airway inflammation, providing solid support for the use of genetically engineered MSCs as a potential novel therapy for allergic airway inflammation.

Mesenchymal stromal cells and their small extracellular vesicles in allergic diseases: From immunomodulation to therapy

Mesenchymal stromal cells (MSCs) have long been considered a potential tool for treatment of allergic inflammatory diseases, owing to their immunomodulatory characteristics. In recent decades, the medical utility of MSCs has been evaluated both in vitro and in vivo, providing a foundation for therapeutic applications. However, the existing limitations of MSC therapy indicate the necessity for novel therapies. Notably, small extracellular vesicles (sEV) derived from MSCs have emerged rapidly as candidates instead of their parental cells. The acquisition of abundant and scalable MSC-sEV is an obstacle for clinical applications. The potential application of MSC-sEV in allergic diseases has attracted increasing attention from researchers. By carrying biological microRNAs or active proteins, MSC-sEV can modulate the function of various innate and adaptive immune cells. In this review, we summarise the recent advances in the immunomodulatory properties of MSCs in allergic diseases, the cellular sources of MSC-sEV, and the methods for obtaining high-quality human MSC-sEV. In addition, we discuss the immunoregulatory capacity of MSCs and MSC-sEV for the treatment of asthma, atopic dermatitis, and allergic rhinitis, with a special emphasis on their immunoregulatory effects and the underlying mechanisms of immune cell modulation.

Recent advances in understanding the effects of T lymphocytes on mucosal barrier function in allergic rhinitis

Allergic rhinitis is a non-infectious chronic inflammatory disease of the nasal mucosa that affects T cells and their cytokines. T cells play significant roles in the development of allergic inflammatory diseases by orchestrating mechanisms underlying innate and adaptive immunity. Although many studies on allergic rhinitis have focused on helper T cells, molecular makeup, and pathogenesis-related transduction pathways, pathological mechanisms have not yet been completely explored. Recent studies have suggested that T cell status may play an important role in the interaction between T cells and the nasal mucosal barrier in allergic rhinitis. This study aimed to explore the interactions between T cells and nasal mucosal barriers in allergic rhinitis and to review the therapeutic modalities of pertinent biological agents involving T cells.

Mesodermal Derivatives of Pluripotent Stem Cells Route to Scarless Healing

Scar formation during normal tissue regeneration in adults may result in noticeable cosmetic and functional defects and have a significant impact on the quality of life. In contrast, fetal tissues in the mid-gestation period are known to be capable of complete regeneration with the restitution of the initial architecture, organization, and functional activity. Successful treatments that are targeted to minimize scarring can be realized by understanding the cellular and molecular mechanisms of fetal wound regeneration. However, such experiments are limited by the inaccessibility of fetal material for comparable studies. For this reason, the molecular mechanisms of fetal regeneration remain unknown. Mesenchymal stromal cells (MSCs) are central to tissue repair because the molecules they secrete are involved in the regulation of inflammation, angiogenesis, and remodeling of the extracellular matrix. The mesodermal differentiation of human pluripotent stem cells (hPSCs) recapitulates the sequential steps of embryogenesis in vitro and provides the opportunity to generate the isogenic cell models of MSCs corresponding to different stages of human development. Further investigation of the functional activity of cells from stromal differon in a pro-inflammatory microenvironment will procure the molecular tools to better understand the fundamental mechanisms of fetal tissue regeneration. Herein, we review recent advances in the generation of clonal precursors of primitive mesoderm cells and MSCs from hPSCs and discuss critical factors that determine the functional activity of MSCs-like cells in a pro-inflammatory microenvironment in order to identify therapeutic targets for minimizing scarring.

Dendritic cells mediated by small extracellular vesicles derived from MSCs attenuated the ILC2 activity via PGE2 in patients with allergic rhinitis

BACKGROUND

Mesenchymal stromal cells-derived small extracellular vesicles (MSC-sEVs) have recently attracted considerable attention because of their therapeutic potential in various immune diseases. We previously reported that MSC-sEVs could exert immunomodulatory roles in allergic airway inflammation by regulating group 2 innate lymphoid cell (ILC2) and dendritic cell (DC) functions. Therefore, this study aimed to investigate the indirect effects of MSC-sEVs on ILC2s from patients with allergic rhinitis (AR) via DCs.

METHODS

Here, we isolated sEVs from induced pluripotent stem cells-MSCs using anion-exchange chromatography and mature DCs (mDCs) were treated with MSC-sEVs. sEV-mDCs were co-cultured with peripheral blood mononuclear cells from patients with AR or purified ILC2s. The levels of IL-13 and GATA3 in ILC2s were examined by flow cytometry. Bulk RNA sequence for mDCs and sEV-mDCs was employed to further probe the potential mechanisms, which were then validated in the co-culture systems.

RESULTS

sEV-mDCs showed impaired capacity in priming the levels of IL-13 and GATA3 in ILC2s when compared with mDCs. Furthermore, there was higher PGE2 and IL-10 production from sEV-mDCs, and the blockade of them especially the former one reversed the inhibitory effects of sEV-mDCs.

CONCLUSIONS

We demonstrated that MSC-sEVs were able to dampen the activating effects of mDCs on ILC2s in patients with AR. Mechanismly, the PGE2-EP2/4 axis played an essential role in the immunomodulatory effects of sEV-mDCs on ILC2s. Herein, we provided new insights into the mechanism underlying the therapeutic effects of MSC-sEVs in allergic airway inflammation.

Mesenchymal stem cells and allergic airway inflammation; a therapeutic approach to induce immunoregulatory responses

Allergic airway inflammations are among the essential disorders worldwide that are already considered a significant concern. Mesenchymal stem cells (MSCs) are stromal cells with regenerative potential and immunomodulatory characteristics and are widely administered for tissue repair as an immunoregulatory agent in different inflammatory diseases. The current review summarized primary studies conducted to evaluate the therapeutic potential of MSCs for allergic airway disorders. In this case, modulation of airway pathologic inflammation and infiltration of inflammatory cells were examined, and modulation of the Th1/Th2 cellular balance and humoral responses. Also, the effects of MSCs on the Th17/Treg ratio and inducing Treg immunoregulatory responses along with macrophage and dendritic cell function were evaluated.

Regenerative Medicine and Rehabilitation Therapy in the Canine

Regenerative medicine is used in the canine to optimize tissue healing and treat osteoarthritis and soft tissue injuries. Rehabilitation therapy is also often implemented in the treatment and management of musculoskeletal conditions in the canine. Initial experimental studies have shown that regenerative medicine and rehabilitation therapy may work safely and synergistically to enhance tissue healing. Although additional study is required to define optional rehabilitation therapy protocols after regenerative medicine therapy in the canine, certain fundamental principles of rehabilitation therapy still apply to patients treated with regenerative medicine.

The potential therapeutic role of extracellular vesicles in critical-size bone defects: Spring of cell-free regenerative medicine is coming

In recent years, the incidence of critical-size bone defects has significantly increased. Critical-size bone defects seriously affect patients' motor functions and quality of life and increase the need for additional clinical treatments. Bone tissue engineering (BTE) has made great progress in repairing critical-size bone defects. As one of the main components of bone tissue engineering, stem cell-based therapy is considered a potential effective strategy to regenerate bone tissues. However, there are some disadvantages including phenotypic changes, immune rejection, potential tumorigenicity, low homing efficiency and cell survival rate that restrict its wider clinical applications. Evidence has shown that the positive biological effects of stem cells on tissue repair are largely mediated through paracrine action by nanostructured extracellular vesicles (EVs), which may overcome the limitations of traditional stem cell-based treatments. In addition to stem cell-derived extracellular vesicles, the potential therapeutic roles of nonstem cell-derived extracellular vesicles in critical-size bone defect repair have also attracted attention from scholars in recent years. Currently, the development of extracellular vesicles-mediated cell-free regenerative medicine is still in the preliminary stage, and the specific mechanisms remain elusive. Herein, the authors first review the research progress and possible mechanisms of extracellular vesicles combined with bone tissue engineering scaffolds to promote bone regeneration via bioactive molecules. Engineering modified extracellular vesicles is an emerging component of bone tissue engineering and its main progression and clinical applications will be discussed. Finally, future perspectives and challenges of developing extracellular vesicle-based regenerative medicine will be given. This review may provide a theoretical basis for the future development of extracellular vesicle-based biomedicine and provide clinical references for promoting the repair of critical-size bone defects.

Mesenchymal Stem/Stromal Cells in Asthma Therapy: Mechanisms and Strategies for Enhancement

Asthma is a complex and heterogeneous disease characterized by chronic airway inflammation, airway hyperresponsiveness, and airway remodeling. Most asthmatic patients are well-established using standard treatment strategies and advanced biologicals. However, a small group of patients who do not respond to biological treatments or are not effectively controlled by available treatment strategies remain a clinical challenge. Therefore, new therapies are urgently needed for poorly controlled asthma. Mesenchymal stem/stromal cells (MSCs) have shown therapeutic potential in relieving airway inflammation and repairing impaired immune balance in preclinical trials owing to their immunomodulatory abilities. Noteworthy, MSCs exerted a therapeutic effect on steroid-resistant asthma with rare side effects in asthmatic models. Nevertheless, adverse factors such as limited obtained number, nutrient and oxygen deprivation in vitro, and cell senescence or apoptosis affected the survival rate and homing efficiency of MSCs, thus limiting the efficacy of MSCs in asthma. In this review, we elaborate on the roles and underlying mechanisms of MSCs in the treatment of asthma from the perspective of their source, immunogenicity, homing, differentiation, and immunomodulatory capacity and summarize strategies to improve their therapeutic effect.

Immunomodulatory Effects of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Allergic Airway Disease

Mesenchymal stem cells (MSCs) have been reported as promising candidates for the treatment of various diseases, especially allergic diseases, as they have the capacity to differentiate into various cells. However, MSCs itself have several limitations such as creating a risk of aneuploidy, difficulty in handling them, immune rejection, and tumorigenicity, so interest in the extracellular vesicles (EVs) released from MSCs are increasing, and many studies have been reported. Previous studies have shown that extracellular vesicles (EVs) produced by MSCs are as effective as the MSCs themselves in suppression of allergic airway inflammation through the suppression of Th2 cytokine production and the induction of regulatory T cells (Treg) expansion. EVs are one of the substances secreted by paracrine induction from MSCs, and because it exerts its effect by delivering contents such as mRNA, microRNA, and proteins to the receptor cell, it can reduce the problems or risks related to stem cell therapy. This article reviews the immunomodulatory properties of MSCs-derived EVs and their therapeutic implications for allergic airway disease.

Mesenchymal stem/stromal cells in the pathogenesis and regenerative therapy of inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) represent a group of chronic inflammatory disorders of the gastrointestinal (GI) tract including ulcerative colitis (UC), Crohn’s disease (CD), and unclassified IBDs. The pathogenesis of IBDs is related to genetic susceptibility, environmental factors, and dysbiosis that can lead to the dysfunction of immune responses and dysregulated homeostasis of local mucosal tissues characterized by severe inflammatory responses and tissue damage in GI tract. To date, extensive studies have indicated that IBDs cannot be completely cured and easy to relapse, thus prompting researchers to find novel and more effective therapeutics for this disease. Due to their potent multipotent differentiation and immunomodulatory capabilities, mesenchymal stem/stromal cells (MSCs) not only play an important role in regulating immune and tissue homeostasis but also display potent therapeutic effects on various inflammatory diseases, including IBDs, in both preclinical and clinical studies. In this review, we present a comprehensive overview on the pathological mechanisms, the currently available therapeutics, particularly, the potential application of MSCs-based regenerative therapy for IBDs.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for Bone Defect Repair

The repair of critical bone defects is a hotspot of orthopedic research. With the development of bone tissue engineering (BTE), there is increasing evidence showing that the combined application of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) (MSC-EVs), especially exosomes, with hydrogels, scaffolds, and other bioactive materials has made great progress, exhibiting a good potential for bone regeneration. Recent studies have found that miRNAs, proteins, and other cargo loaded in EVs are key factors in promoting osteogenesis and angiogenesis. In BTE, the expression profile of the intrinsic cargo of EVs can be changed by modifying the gene expression of MSCs to obtain EVs with enhanced osteogenic activity and ultimately enhance the osteoinductive ability of bone graft materials. However, the current research on MSC-EVs for repairing bone defects is still in its infancy, and the underlying mechanism remains unclear. Therefore, in this review, the effect of bioactive materials such as hydrogels and scaffolds combined with MSC-EVs in repairing bone defects is summarized, and the mechanism of MSC-EVs promoting bone defect repair by delivering active molecules such as internal miRNAs is further elucidated, which provides a theoretical basis and reference for the clinical application of MSC-EVs in repairing bone defects.

Mesenchymal stromal cells-derived small extracellular vesicles modulate DC function to suppress Th2 responses via IL-10 in patients with allergic rhinitis

Mesenchymal stromal cells (MSCs) are well known for their immunoregulatory roles on allergic inflammation particularly by acting on T cells, B cells, and dendritic cells (DCs). MSC‐derived small extracellular vesicles (MSC‐sEV) are increasingly considered as one of the main factors for the effects of MSCs on immune responses. However, the effects of MSC‐sEV on DCs in allergic diseases remain unclear.

Engineering of human mesenchymal stem cells resistant to multiple natural killer subtypes

Mesenchymal stem cells (MSCs) as a therapeutic promise are often quickly cleared by innate immune cells of the host including natural killer (NK) cells. Efforts have been made to generate immune-escaping human embryonic stem cells (hESCs) where T cell immunity is evaded by defecting β-2-microglobulin (B2M), a common unit for human leukocyte antigen (HLA) class I, and NK cells are inhibited via ectopic expression of HLA-E or -G. However, NK subtypes vary among recipients and even at different pathologic statuses. It is necessary to dissect and optimize the efficacy of the immune-escaping cells against NK subtypes. Here, we first generated B2M knockout hESCs and differentiated them to MSCs (EMSCs) and found that NK resistance occurred with B2M^-/- EMSCs expressing HLA-E and -G only when they were transduced via an inducible lentiviral system in a dose-dependent manner but not when they were inserted into a safe harbor. HLA-E and -G expressed at high levels together in transduced EMSCs inhibited three major NK subtypes, including NKG2A⁺/LILRB1⁺, NKG2A⁺/LILRB1^-, and NKG2A^-/LILRB1⁺, which was further potentiated by IFN-γ priming. Thus, this study engineers MSCs with resistance to multiple NK subtypes and underscores that dosage matters when a transgene is used to confer a novel effect to host cells, especially for therapeutic cells to evade immune rejection.

Application of mesenchymal stem cells derived from human pluripotent stem cells in regenerative medicine

Mesenchymal stem cells (MSCs) represent the most clinically used stem cells in regenerative medicine. However, due to the disadvantages with primary MSCs, such as limited cell proliferative capacity and rarity in the tissues leading to limited MSCs, gradual loss of differentiation during in vitro expansion reducing the efficacy of MSC application, and variation among donors increasing the uncertainty of MSC efficacy, the clinical application of MSCs has been greatly hampered. MSCs derived from human pluripotent stem cells (hPSC-MSCs) can circumvent these problems associated with primary MSCs. Due to the infinite self-renewal of hPSCs and their differentiation potential towards MSCs, hPSC-MSCs are emerging as an attractive alternative for regenerative medicine. This review summarizes the progress on derivation of MSCs from human pluripotent stem cells, disease modelling and drug screening using hPSC-MSCs, and various applications of hPSC-MSCs in regenerative medicine. In the end, the challenges and concerns with hPSC-MSC applications are also discussed.

Intranasally Administered Extracellular Vesicles from Adipose Stem Cells Have Immunomodulatory Effects in a Mouse Model of Asthma

Asthma is a chronic eosinophilic airway disease characterized by type 2 helper T cell-driven inflammation. Adipose stem cells (ASCs) and the ASC culture supernatant are known to improve allergic airway inflammation; however, the immunomodulatory effects of ASC-derived extracellular vesicles (EVs) on allergic airway diseases remain unclear. Thus, we assessed the effects of ASC-derived EVs on allergic airway inflammation in a mouse model of asthma. EVs were isolated from the culture supernatant of murine ASCs and characterized. Six-week-old female C57BL/6 mice were sensitized to ovalbumin (OVA) by intraperitoneal injection and challenged intranasally with OVA. Before the OVA challenge, 10 μg/50 μl of ASC-derived EVs was administered intranasally to the experimental group. ASC-derived EVs significantly attenuated airway hyperresponsiveness (AHR) in asthmatic mice (p = 0.023). ASC-derived EVs resulted in a remarkable reduction of the total number of inflammatory cells (p = 0.005) and eosinophils (p = 0.023) in the bronchoalveolar lavage fluid (BALF), the degree of eosinophilic lung inflammation (p < 0.001), and the serum total and OVA-specific immunoglobulin (Ig)E (p = 0.048 and p = 0.001) and total IgG1 (p < 0.001). Interleukin- (IL-) 4 was significantly inhibited with ASC-derived EV pretreatment in the BALF and lung draining lymph nodes (LLNs) (p = 0.040 and p = 0.011). Furthermore, ASC-derived EV administration resulted in a significant increase of the regulatory T cell (Treg) populations in LLNs. ASC-derived EVs alleviated AHR and allergic airway inflammation caused by the induction of Treg expansion in a mouse model of asthma. There seems to be a role for ASC-derived EVs as a modifier in allergic airway disease.

Mesenchymal stem/stromal cell therapy in atopic dermatitis and chronic urticaria: immunological and clinical viewpoints

Allergic diseases are immune-mediated diseases. Allergies share a common immunopathogenesis, with specific differences according to the specific disease. Mesenchymal stem/stromal cells (MSCs) have been applied to people suffering from allergic and many other diseases. In this review, the immunologic roles of MSCs are systemically reviewed according to disease immunopathogenesis from a clinical viewpoint. MSCs seem to be a promising therapeutic modality not only as symptomatic treatments but also as causative and even preventive treatments for allergic diseases, including atopic dermatitis and chronic urticaria.

Pluripotent-derived Mesenchymal Stem/stromal Cells: an Overview of the Derivation Protocol Efficacies and the Differences Among the Derived Cells

Mesenchymal stem/stromal cells (MSCs) are remarkable tools for regenerative medicine. Therapeutic approaches using these cells can promote increased activity and viability in several cell types through diverse mechanisms such as paracrine and immunomodulatory activities, contributing substantially to tissue regeneration and functional recovery. However, biological samples of human MSCs, usually obtained from adult tissues, often exhibit variable behavior during in vitro culture, especially with respect to cell population heterogeneity, replicative senescence, and consequent loss of functionality. Accordingly, it is necessary to establish standard protocols to generate high-quality, stable cell cultures, for example, by using pluripotent stem cells (PSCs) in derivation protocols of MSC-like cells since PSCs maintain their characteristics consistently during culture. However, the available protocols seem to generate distinct populations of PSC-derivedMSCs (PSC-MSCs) with peculiar attributes, which do not always resemble bona fide primary MSCs. The present review addresses the developmental basis behind some of these derivation protocols, exposing the differences among them and discussing the functional properties of PSC-MSCs, shedding light on elements that may help determine standard characterizations and criteria to evaluate and define these cells.

Mesenchymal stem cells enhance Treg immunosuppressive function at the fetal-maternal interface

Well-regulated maternal-fetal immune tolerance is a prerequisite for normal pregnancy. Hyperactivated immune cells and overwhelming inflammatory responses trigger adverse gestation outcome, such as recurrent spontaneous abortion (RSA). Local exacerbation of immunomodulatory cells in maternal decidua is a critical event, tightly linked with fetus acceptance. Owning to the notable immunoregulatory potentials, mesenchymal stromal cells (MSCs) and regulatory T cells (Tregs) have been separately reported as promising therapeutic approaches for refractory RSA attributable to certain immune disorders. However, the cross-talk between MSCs and Tregs at the fetal-maternal interface remains poorly understood. Here we revealed, for the first time, that umbilical MSCs could induce expansion of decidual Foxp3⁺CD4⁺ T cells with upregulated production of IL-10 and TGF-β. Meanwhile, MSCs reinforced the immune suppressive functions of decidual Tregs (dTregs). More important, MSCs-instructed dTregs gained enhanced capacity to suppress Th1 and Th17 related inflammatory responses. In vivo data demonstrated that adoptive transfer of MSCs obviously promoted accumulation of Foxp3⁺ dTregs in lipopolysaccharide (LPS)-induced mice abortion model and spontaneous abortion model (DBA/2-mated female CBA/J mice). Furthermore, MSCs treatment effectively ameliorated absorption rate in both models. This study may offer a new insight for the application of MSCs and Tregs in clinical recurrent miscarriage.

Comparative analysis of human induced pluripotent stem cell-derived mesenchymal stem cells and umbilical cord mesenchymal stem cells

Generation of induced pluripotent stem cells (iPSCs) and their differentiation into mesenchymal stem/stromal cells (iMSCs) have created exciting source of cells for autologous therapy. In this study, we have compared the therapeutic potential of iMSCs generated from urinary epithelial (UE) cells with the available umbilical cord MSCs (UC‐MSCs). For this, adult UE cells were treated with the mRNA of pluripotent genes (OCT4, NANOG, SOX2, KLF4, MYC and LIN28) and a cocktail of miRNAs under specific culture conditions for generating iPSCs. Our non‐viral and mRNA‐based treatment regimen demonstrated a high reprogramming efficiency to about 30% at passage 0. These UE‐iPSCs were successfully differentiated further into ectoderm, endoderm and mesoderm lineage of cells. Moreover, these UE‐iPSCs were subsequently differentiated into iMSCs and were compared with the UC‐MSCs. These iMSCs were capable of differentiating into osteocytes, chondrocytes and adipocytes. Our qRT‐PCR and Western blot data showed that the CD73, CD90 and CD105 gene transcripts and proteins were highly expressed in iMSCs and UC‐MSCs but not in other cells. The comparative qRT‐PCR data showed that the iMSCs maintained their MSC characteristics without any chromosomal abnormalities even at later passages (P15), during which the UC‐MSCs started losing their MSC characteristics. Importantly, the wound‐healing property demonstrated through migration assay was superior in iMSCs when compared to the UC‐MSCs. In this study, we have demonstrated an excellent non‐invasive and pain‐free method of obtaining iMSCs for regenerative therapy. These homogeneous autologous highly proliferative iMSCs may provide an alternative source of cells to UC‐MSCs for treating various diseases.

HMSC-Derived Exosome Inhibited Th2 Cell Differentiation via Regulating miR-146a-5p/SERPINB2 Pathway

Background

Allergic rhinitis (AR) is a global disease without specific treatment. Human mesenchymal stem cell- (HMSC-) derived exosomes (HMSC-exos) have been implicated for the amelioration of allergic inflammation by delivering miR-146a-5p in a mouse asthma model. However, the antiallergic activity and the underlying mechanism of HMSC-exos in AR remain unclear. The present study aimed to investigate the role of HMSC-exos in the pathogenesis of AR.

Materials and Methods

Blood specimens were collected from AR patients and healthy donators for investigation. HMSC and CD4⁺ T cells were used in the present study. Flow cytometry was used to characterize the population of Type 1 helper T (Th1) and Th2 cells. Specific siRNA and overexpressed plasmids were designed to silence or overexpress the expressions of miR-146a-5p and SERPINB2. Luciferase reporter assay was adopted to explore the binding site of miR-146a-5p and SERPINB2. Quantitative real-time PCR and immunoblots were performed to estimate the expression of target genes.

Results

The population of Th2 cells was significantly elevated in AR patients as compared with that in healthy donators. HMSC-exos could decrease the expression of SERPINB2 and the differentiation of Th2 cells. miR-146a-5p in HMSC-exos exhibited consistent effects and lowered the expression of SERPINB2 by binding on its 3′UTR region. Moreover, the differentiation of Th2 cells was promoted by SERPINB2 that could be reversed by HMSC-exos. Additionally, the miR-146a-5p expression was negatively associated with the SERPINB2 expression in the serum of AR patients.

Conclusion

HMSC-exos could inhibit the differentiation of Th2 cells via the regulation of the miR-146a-5p/SERPINB2 pathway. miR-146a-5p and SERPINB2 could be applied as potential targets for AR treatment.

Protective effect of miR-138-5p inhibition modified human mesenchymal stem cell on ovalbumin-induced allergic rhinitis and asthma syndrome

The objective of the study is to evaluate the protective effects of human mesenchymal stem cells (hMSCs) modified with miR‐138‐5p inhibitor against the allergic rhinitis and asthma syndrome (ARAS). MiR‐138‐5p or negative control was transfected into hMSCs, and fluorescence‐activated cell sorting was used to evaluate hMSC surface markers. Quantitative real‐time PCR (qRT‐PCR) was used to evaluate miR‐138‐5p, SIRT1, caspase‐3, IL‐6, IL‐1β and TNF‐α levels after TNF‐α and IL‐6 stimulations. hMSCs with or without miR‐138‐5p inhibition was intranasally administered into ARAS mice (n = 10 each group), followed by monitoring sneezing and nasal rubbing events to evaluate the allergic symptoms. Histamine, ovalbumin‐specific IgE, IgG2a, IgG1 and LTC4 release were monitored in the serum and nasal lavage fluid using enzyme‐linked immunosorbent assay. Expression of SIRT1 and HMGB1/TLR4 pathway in nasal mucosa was assessed. After miR‐138‐5p inhibitor transfection, the hMSC lineage was preserved. Binding between SIRT1 and miR‐138‐4p was observed, and miR‐138‐5p inhibition led to upregulation of SIRT1. Inhibition of miR‐138‐5p led to attenuated inflammatory responses of hMSCs upon TNF‐α and IL‐6 stimulation, and allergic symptoms in mice, as well as histamine and ovalbumin‐specific IgG release. hMSCs with miR‐138‐5p inhibition showed characteristics of activated SIRT1 and inhibited HMGB1/TLR4 pathway. Inhibition of miR‐138‐5p in hMSCs enhanced its effects in attenuating inflammatory responses and allergic reaction in the ARAS model, which is presumably regulated by SIRT1 and the HMGB1/TLR4 pathway.

Mesenchymal stem cells derived from human dental follicle modulate the aberrant immune response in atopic dermatitis

Background: Atopic dermatitis (AD) is an inflammatory cutaneous disorder. The advancements in the understanding of AD immunological pathogenesis have caused the development of therapies that suppress the dysregulated immune response. We aimed to evaluate the immunomodulatory effect of dental stem cells (dental follicle-mesenchymal stem cells [DF-MSCs]) on AD patients. Materials & methods: We investigated the immunoregulatory potential of DF-MSCs on T cell response in AD and compared them with psoriasis and healthy individuals and the underlying mechanisms. Results: DF-MSCs significantly reduced Fas, FasL and TNFR II frequency in T cells, increased naive T cell population while reducing memory T cell, decreased inflammatory cytokine levels and promoted Tregs frequency in the AD population. Conclusion: These results imply that DF-MSCs are modulating inflammation through decreasing T cell apoptosis, inducing Treg expansion and stabilizing cytokine levels.

Application Prospects of Mesenchymal Stem Cell Therapy for Bronchopulmonary Dysplasia and the Challenges Encountered

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in premature babies, especially affecting those with very low or extremely low birth weights. Survivors experience adverse lung and neurological defects including cognitive dysfunction. This impacts the prognosis of children with BPD and may result in developmental delays. The currently available options for the treatment of BPD are limited owing to low efficacy or several side effects; therefore, there is a lack of effective treatments for BPD. The treatment for BPD must help in the repair of damaged lung tissue and promote further growth of the lung tissue. In recent years, the emergence of stem cell therapy, especially mesenchymal stem cell (MSC) therapy, has improved the treatment of BPD to a great extent. This article briefly reviews the advantages, research progress, and challenges faced with the use of MSCs in the treatment of BPD. Stem cell therapy is beneficial as it repairs damaged tissues by reducing inflammation, fibrosis, and by acting against oxidative stress damage. Experimental trials have also proven that MSCs provide a promising avenue for BPD treatment. However, there are challenges such as the possibility of MSCs contributing to tumorous growths, the presence of heterogeneous cell populations resulting in variable efficacy, and the ethical considerations regarding the use of this treatment in humans. Therefore, more research must be conducted to determine whether MSC therapy can be approved as a treatment option for BPD.

Mesenchymal stem cells regulate type 2 innate lymphoid cells via regulatory T cells through ICOS-ICOSL interaction

Group 2 innate lymphoid cells (ILC2s) are recognized as key controllers and effectors of type 2 inflammation. Mesenchymal stem cells (MSCs) have been shown to alleviate type 2 inflammation by modulating T lymphocyte subsets and decreasing T_H 2 cytokine levels. However, the effects of MSCs on ILC2s have not been investigated. In this study, we investigated the potential immunomodulatory effects of MSCs on ILC2s in peripheral blood mononuclear cells (PBMCs) from allergic rhinitis patients and healthy subjects. We further investigated the mechanisms involved in the MSC modulation using isolated lineage negative (Lin^- ) cells. PBMCs and Lin^- cells were cocultured with induced pluripotent stem cell-derived MSCs (iPSC-MSCs) under the stimulation of epithelial cytokines IL-25 and IL-33. And the ILC2 levels and functions were examined and the possible mechanisms were investigated based on regulatory T (Treg) cells and ICOS-ICOSL pathway. iPSC-MSCs successfully decreased the high levels of IL-13, IL-9, and IL-5 in PBMCs in response to IL-25, IL-33, and the high percentages of IL-13⁺ ILC2s and IL-9⁺ ILC2s in response to epithelial cytokines were significantly reversed after the treatment of iPSC-MSCs. However, iPSC-MSCs were found directly to enhance ILC2 levels and functions via ICOS-ICOSL interaction in Lin^- cells and pure ILC2s. iPSC-MSCs exerted their inhibitory effects on ILC2s via activating Treg cells through ICOS-ICOSL interaction. The MSC-induced Treg cells then suppressed ILC2s by secreting IL-10 in the coculture system. This study revealed that human MSCs suppressed ILC2s via Treg cells through ICOS-ICOSL interaction, which provides further insight to regulate ILC2s in inflammatory disorders.

Long-Term Trypsin Treatment Promotes Stem Cell Potency of Canine Adipose-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) isolated from adipose tissue (adipose-derived stem cells [ADSCs]) are considered one of the most promising cell types for applications in regenerative medicine. However, the regenerative potency of ADSCs may vary because of heterogeneity. Long-term trypsin treatment (LTT) is known to significantly concentrate multilineage-differentiating stress-enduring (Muse) cells from human MSCs. In this study, we aimed to generate cells with high stem cell potency from canine ADSCs using LTT. After 16 h of treatment with trypsin, surviving ADSCs (LTT-tolerant cells) had significantly enhanced expression of stage-specific embryonic antigen (SSEA)-1, a mouse embryonic stem cell marker, and fucosyltransferase 9, one of several fucosyltransferases for SSEA-1 biosynthesis. However, LTT-tolerant cells did not enhance the expression of SSEA-3, a known human Muse cell marker. LTT-tolerant cells, however, showed significantly higher self-renewal capacity in the colony-forming unit fibroblast assay than ADSCs. In addition, the LTT-tolerant cells formed cell clusters similar to embryoid bodies and expressed undifferentiated markers. Moreover, these cells differentiated into cells of all three germ layers and showed significantly higher levels of α 2-6 sialic acid (Sia)-specific lectins, known as differentiation potential markers of human MSCs, than ADSCs. LTT-tolerant cells had a normal karyotype and had low telomerase activity, showing little carcinogenetic potency. LTT-tolerant cells also showed significantly increased activity of transmigration in the presence of chemoattractants and had increased expression of migration-related genes compared with ADSCs. In addition, LTT-tolerant cells had stronger suppressive activity against mitogen-stimulated lymphocyte proliferation than ADSCs. Overall, these results indicated that the LTT-tolerant cells in canine ADSCs have similar properties as human Muse cells (although one of the undifferentiated markers is different) and are expected to be a promising tool for regenerative therapy in dogs.

Applications of Mesenchymal Stem Cells in Skin Regeneration and Rejuvenation

Mesenchymal stem cells (MSCs) are multipotent stem cells derived from adult stem cells. Primary MSCs can be obtained from diverse sources, including bone marrow, adipose tissue, and umbilical cord blood. Recently, MSCs have been recognized as therapeutic agents for skin regeneration and rejuvenation. The skin can be damaged by wounds, caused by cutting or breaking of the tissue, and burns. Moreover, skin aging is a process that occurs naturally but can be worsened by environmental pollution, exposure to ultraviolet radiation, alcohol consumption, tobacco use, and undernourishment. MSCs have healing capacities that can be applied in damaged and aged skin. In skin regeneration, MSCs increase cell proliferation and neovascularization, and decrease inflammation in skin injury lesions. In skin rejuvenation, MSCs lead to production of collagen and elastic fibers, inhibition of metalloproteinase activation, and promote protection from ultraviolet radiation-induced senescence. In this review, we focus on how MSCs and MSC-derived molecules improve diseased and aged skin. Additionally, we emphasize that induced pluripotent stem cell (iPSC)-derived MSCs are potentially advanced MSCs, which are suitable for cell therapy.

Immunomodulation by systemic administration of human-induced pluripotent stem cell-derived mesenchymal stromal cells to enhance the therapeutic efficacy of cell-based therapy for treatment of myocardial infarction

Rationale: Poor survival and engraftment are major hurdles of stem cell therapy in the treatment of myocardial infarction (MI). We sought to determine whether pre-transplantation systemic intravenous administration of human induced pluripotent stem cell (hiPSC)-derived mesenchymal stromal cells (hiPSC-MSCs) could improve the survival of hiPSC-MSCs or hiPSC-derived cardiomyocytes (hiPSC-CMs) following direct intramyocardial transplantation in a mouse model of MI.

Methods: Mice were randomized to undergo intravenous administration of saline or 5×10⁵ hiPSC-MSCs one week prior to MI, induced by ligation of the left anterior descending coronary artery. Mice were further assigned to undergo direct intramyocardial transplantation of hiPSC-MSCs (1×10⁶) or hiPSC-CMs (1×10⁶) 10 minutes following MI. Echocardiographic and invasive hemodynamic assessment were performed to determine cardiac function. In-vivo fluorescent imaging analysis, immunofluorescence staining and polymerase chain reaction were performed to detect cell engraftment. Flow cytometry of splenic regulatory T cells (Tregs) and natural killer (NK) cells was performed to assess the immunomodulatory effects.

Results: Pre-transplantation systemic administration of hiPSC-MSCs increased systemic Tregs activation, decreased the number of splenic NK cells and inflammation, and enhanced survival of transplanted hiPSC-MSCs and hiPSC-CMs. These improvements were associated with increased neovascularization and decreased myocardial inflammation and apoptosis at the peri-infract zone with consequent improved left ventricular function four weeks later. Co-culture of splenic CD4 cells with hiPSC-MSCs also modulated their cytokine expression profile with a decreased level of interferon-γ, tumor necrosis factor-α, and interleukin (IL)-17A, but not IL-2, IL-6 and IL-10.

Conclusion: Pre-transplantation systemic intravenous administration of hiPSC-MSCs induced immunomodulation and facilitated the survival of intramyocardially transplanted cells to improve cardiac function in MI.

Mesenchymal stem cells: amazing remedies for bone and cartilage defects

Skeletal disorders are among the leading debilitating factors affecting millions of people worldwide. The use of stem cells for tissue repair has raised many promises in various medical fields, including skeletal disorders. Mesenchymal stem cells (MSCs) are multipotent stromal cells with mesodermal and neural crest origin. These cells are one of the most attractive candidates in regenerative medicine, and their use could be helpful in repairing and regeneration of skeletal disorders through several mechanisms including homing, angiogenesis, differentiation, and response to inflammatory condition. The most widely studied sources of MSCs are bone marrow (BM), adipose tissue, muscle, umbilical cord (UC), umbilical cord blood (UCB), placenta (PL), Wharton's jelly (WJ), and amniotic fluid. These cells are capable of differentiating into osteoblasts, chondrocytes, adipocytes, and myocytes in vitro. MSCs obtained from various sources have diverse capabilities of secreting many different cytokines, growth factors, and chemokines. It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues. Accordingly, differential identification of MSCs' secretome enables us to make optimal choices in skeletal disorders considering various sources. This review discusses and compares the therapeutic abilities of MSCs from different sources for bone and cartilage diseases.

Induced Pluripotent Stem Cell-Differentiated Chondrocytes Repair Cartilage Defect in a Rabbit Osteoarthritis Model

The aim of this study was to explore the therapeutic effect of iPSC-mesenchymal stem cell (MSC)-derived chondrocytes in a rabbit osteoarthritis (OA) model. The iPSCs were characterized by gene expressions, immunostaining of pluripotent markers, and in vivo teratoma formation. iPSC-differentiated MSCs were characterized by flow cytometry and trilineage differentiation. A rabbit OA model was established by the transection of the anterior cruciate ligament. The therapeutic effect of transplanted iPSC-MSC-chondrocytes on the OA was evaluated by the histology, immunostaining, and qPCR of defective cartilage. The results showed iPSC could express pluripotency markers such as OCT4, SOX2, and NANOG and form an embryoid body and a teratoma. After differentiation of iPSCs for 30 days, MSCs were established. The iPSC-MSC could express typical MSC markers such as CD29, CD44, CD90, CD105, and HLA-ABC. They could differentiate into adipocytes, osteocytes, and chondrocytes. In this model, iPSC-MSC-chondrocytes significantly improved the histology and ICRS (International Cartilage Repair Society) scores. The transplanted cartilage expressed less IL-1β, TNF-α, and MMP13 than control cartilage. In conclusion, the iPSCs we derived might represent an emerging source for differentiated MSC-chondrocyte and might rescue cartilage defects through its anti-inflammatory and anti-catabolic effects.

3D Bioprinting a human iPSC-derived MSC-loaded scaffold for repair of the uterine endometrium

Common events in the clinic, such as uterine curettage or inflammation, may lead to irreversible endometrial damage, often resulting in infertility in women of childbearing age. Currently, tissue engineering has the potential to achieve tissue manipulation, regeneration, and growth, but personalization and precision remain challenges. The application of "3D cell printing" is more in line with the clinical requirements of tissue repair. In this study, a porous grid-type human induced pluripotent stem cell-derived mesenchymal stem cell (hiMSC)-loaded hydrogel scaffold was constructed using a 3D bioprinting device. The 3D-printed hydrogel scaffold provided a permissive in vitro living environment for hiMSCs and significantly increased the survival duration of transplanted hiMSCs when compared with hiMSCs administered locally in vivo. Using an endometrial injury model, we found that hiMSC transplantation can cause early host immune responses (the serological immune response continued for more than 1 month, and the local immune response continued for approximately 1 week). Compared with the sham group, although the regenerative endometrium failed to show full restoration of the normal structure and function of the lining, implantation of the 3D-printed hiMSC-loaded scaffold not only promoted the recovery of the endometrial histomorphology (endometrial tissue and gland regeneration) and the regeneration of endometrial cells (stromal cells and epithelial cells) and endothelial cells but also improved endometrial receptivity functional indicators, namely, pinopode formation and leukemia inhibitory factor and αvβ3 expression, which partly restored the embryo implantation and pregnancy maintenance functions of the injured endometrium. These indicators were significantly better in the 3D-printed hiMSC-loaded scaffold group than in the unrepaired (empty) group, the hiMSCs alone group and the 3D scaffold group, and the empty group showed the worst repair results. Our study confirm that the 3D-printed hiMSC-loaded hydrogel scaffold may be a promising material for endometrial repair.

Screening and Functional Pathway Analysis of Pulmonary Genes Associated with Suppression of Allergic Airway Inflammation by Adipose Stem Cell-Derived Extracellular Vesicles

Background

Although mesenchymal stem cell- (MSC-) derived extracellular vesicles (EVs) are as effective as MSCs in the suppression of allergic airway inflammation, few studies have explored the molecular mechanisms of MSC-derived EVs in allergic airway diseases. The objective of this study was to evaluate differentially expressed genes (DEGs) in the lung associated with the suppression of allergic airway inflammation using adipose stem cell- (ASC-) derived EVs.

Methods

C57BL/6 mice were sensitized to ovalbumin (OVA) by intraperitoneal injection and challenged intranasally with OVA. To evaluate the effect of ASC-derived EVs on allergic airway inflammation, 10 μg/50 μL of EVs were administered intranasally prior to OVA challenge. Lung tissues were removed and DEGs were compared pairwise among the three groups. DEG profiles and hierarchical clustering of the identified genes were analyzed to evaluate changes in gene expression. Real-time PCR was performed to determine the expression levels of genes upregulated after treatment with ASC-derived EVs. Enrichment analysis based on the Gene Ontology (GO) database and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were also performed to further identify the function of DEGs.

Results

Expression of paraoxonase 1 (PON1), brain-expressed X-linked 2 (Bex2), insulin-like growth factor binding protein 6 (Igfbp6), formyl peptide receptor 1 (Fpr1), and secretoglobin family 1C member 1 (Scgb1c1) was significantly increased in asthmatic mice following treatment with ASC-derived EVs. GO enrichment and KEGG pathway analysis showed that these genes were strongly associated with immune system processes and their regulation, cellular processes, single-organism processes, and biological regulation.

Conclusion

These results suggest that the DEGs identified in this study (PON1, Bex2, Igfbp6, Fpr1, and Scgb1c1) may be involved in the amelioration of allergic airway inflammation by ASC-derived EVs.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

Mesenchymal Stem Cell-Based Therapy for Allergic Rhinitis

Allergic rhinitis (AR) is a prevalent disorder that causes a significant and often underestimated health burden for individuals and society. The current drug treatment cannot essentially deal with the regulation of the allergic reaction, while the allergic symptoms could be alleviated. Mesenchymal stem cells (MSCs) bear a variety of properties, such as the ability to differentiate into various cell lineages, to secrete soluble factors crucial for cell survival and proliferation, to migrate to the exact site of injury, and to modulate the immune response. Clinical studies have been extensively conducted in MSCs as the models for varieties of diseases such as neurological diseases. Due to their immunomodulatory properties, the MSCs have gradually been believed to become one of the promising strategies for AR treatments although so far the MSCs-mediated treatment for AR is still at animal experiments stage. Fully understanding the roles and mechanisms of MSCs immunomodulatory effects serves as the prerequisite that will be beneficial to the application of MSCs-based AR clinical treatment methods. In this review article, we highlighted the recent research advances and give a brief perspective in the future study of the MSCs-mediated therapeutic application in AR treatments.

Small extracellular vesicles derived from human MSCs prevent allergic airway inflammation via immunomodulation on pulmonary macrophages

Allergic airway inflammation is a major public health disease that affects up to 300 million people in the world. However, its management remains largely unsatisfactory. The dysfunction of pulmonary macrophages contributes greatly to the development of allergic airway inflammation. It has been reported that small extracellular vesicles derived from mesenchymal stromal cells (MSC-sEV) were able to display extensive therapeutic effects in some immune diseases. This study aimed to investigate the effects of MSC-sEV on allergic airway inflammation, and the role of macrophages involved in it. We successfully isolated MSC-sEV by using anion exchange chromatography, which were morphologically intact and positive for the specific EV markers. MSC-sEV significantly reduced infiltration of inflammatory cells and number of epithelial goblet cells in lung tissues of mice with allergic airway inflammation. Levels of inflammatory cells and cytokines in bronchoalveolar lavage fluid were also significantly decreased. Importantly, levels of monocytes-derived alveolar macrophages and M2 macrophages were significantly reduced by MSC-sEV. MSC-sEV were excreted through spleen and liver at 24 h post-administration in mice, and were able to be taken in by macrophages both in vivo and in vitro. In addition, proteomics analysis of MSC-sEV revealed that the indicated three types of MSC-sEV contained different quantities of proteins and shared 312 common proteins, which may be involved in the therapeutic effects of MSC-sEV. In total, our study demonstrated that MSC-sEV isolated by anion exchange chromatography were able to ameliorate Th2-dominant allergic airway inflammation through immunoregulation on pulmonary macrophages, suggesting that MSC-sEV were promising alternative therapy for allergic airway inflammation in the future.

Application of Stem Cell-Derived Extracellular Vesicles in Allergic Airway Diseases

Mesenchymal stem cells (MSCs) have been reported to be promising candidates for the treatment of allergic airway diseases. However, MSCs themselves have several problems including immune rejection, risk of aneuploidy, difficulty of handling, and tumorigenicity. An increasing number of studies demonstrated that administration of conditioned media or extracellular vesicles (EVs) released by MSCs is as effective as the MSCs themselves in suppression of allergic airway inflammation. EVs can exert their effects by delivering their contents such as proteins, mRNAs, and microRNAs to recipient cells. Furthermore, the administration of MSCs-derived EVs may reduce potential safety risks associated with stem cell therapy, suggesting that MSCs-derived EVs may be a promising alternative to cell therapy for allergic airway diseases. This review examines the current understanding of the immunomodulatory properties of MSCs-derived EVs and its therapeutic implication for allergic airway diseases.

Stem Cells in Veterinary Medicine-Current State and Treatment Options

Regenerative medicine is a branch of medicine that develops methods to grow, repair, or replace damaged or diseased cells, organs or tissues. It has gained significant momentum in recent years. Stem cells are undifferentiated cells with the capability to self—renew and differentiate into tissue cells with specialized functions. Stem cell therapies are therefore used to overcome the body's inability to regenerate damaged tissues and metabolic processes after acute or chronic insult. The concept of stem cell therapy was first introduced in 1991 by Caplan, who proposed that massive differentiation of cells into the desired tissue could be achieved by isolation, cultivation, and expansion of stem cells in in vitro conditions. Among different stem cell types, mesenchymal stem cells (MSC) currently seem to be the most suitable for therapeutic purposes, based on their simple isolation and culturing techniques, and lack of ethical issues regarding their usage. Because of their remarkable immunomodulatory abilities, MSCs are increasingly gaining recognition in veterinary medicine. Developments are primarily driven by the limitations of current treatment options for various medical problems in different animal species. MSCs represent a possible therapeutic option for many animal diseases, such as orthopedic, orodental and digestive tract diseases, liver, renal, cardiac, respiratory, neuromuscular, dermal, olfactory, and reproductive system diseases. Although we are progressively gaining an understanding of MSC behavior and their mechanisms of action, some of the issues considering their use for therapy are yet to be resolved. The aim of this review is first to summarize the current knowledge and stress out major issues in stem cell based therapies in veterinary medicine and, secondly, to present results of clinical usage of stem cells in veterinary patients.

Small extracellular vesicles derived from human mesenchymal stromal cells prevent group 2 innate lymphoid cell-dominant allergic airway inflammation through delivery of miR-146a-5p

Group 2 innate lymphoid cells (ILC2s) are recently reported to play a more critical role in allergic diseases. We previously identified that mesenchymal stromal cells (MSCs) elicited therapeutic effects on allergic airway inflammation. Small extracellular vesicles (sEV) derived from MSCs possess striking advantages including low immunogenicity and high biosafety, and is extremely promising cell-free therapeutic agents. However, the effects of MSC-sEV on ILC2s are still unclear. Additionally, scalable isolation protocols are required for the mass production of homogenous MSC-sEV especially in clinical application. We previously reported that induced pluripotent stem cells-derived MSCs were the ideal cellular source for the large preparation of MSC-sEV. Here we developed a standardized scalable protocol of anion-exchange chromatography for isolation of MSC-sEV, and investigated the effects of MSC-sEV on ILC2 function from patients with allergic rhinitis and in a mouse ILC2-dominant asthma model. The characterization of MSC-sEV was successfully demonstrated in terms of size, morphology and specific markers. Using flow cytometry and human Cytokine Antibody Array, MSC-sEV but not fibroblasts-sEV (Fb-sEV) were found to significantly inhibit the function of human ILC2s. Similarly, systemic administration of MSC-sEV but not Fb-sEV exhibited an inhibition of ILC2 levels, inflammatory cell infiltration and mucus production in the lung, a reduction in levels of T helper 2 cytokines, and alleviation of airway hyperresponsiveness in a mouse model of asthma. Using RNA sequencing, miR-146a-5p was selected as the candidate to mediate the above effects of MSC-sEV. We next revealed the uptake of ILC2s to MSC-sEV, and that transfer of miR-146a-5p in MSC-sEV to ILC2s in part contributed to the effects of MSC-sEV on ILC2s in vitro and in a mouse model. In conclusion, we demonstrated that MSC-sEV were able to prevent ILC2-dominant allergic airway inflammation at least partially through miR-146a-5p, suggesting that MSC-sEV could be a novel cell-free strategy for the treatment of allergic diseases.

Mesenchymal stem cells in allergic diseases: Current status

Allergic diseases, which include asthma, allergic skin diseases, allergic rhinitis and allergic conjunctivitis, have already garnered worldwide public health attention over recent decades. Mesenchymal stem cells (MSCs) have gradually emerged as a potential method for treating allergic diseases due to their immunosuppressive characteristics, tissue repair ability and secretion of various biological factors. This potential of MSC-based therapy has been confirmed in clinical and preclinical studies, which report the therapeutic benefits of MSCs for various allergic diseases and explore the antiallergic mechanisms. In this review, we focus on the discoveries and biological mechanisms of MSCs as a therapeutic tool in allergic diseases. We discuss the challenges of conducting MSC studies as well as future directions.

The Importance of HLA Assessment in "Off-the-Shelf" Allogeneic Mesenchymal Stem Cells Based-Therapies

The need for more effective therapies of chronic and acute diseases has led to the attempts of developing more adequate and less invasive treatment methods. Regenerative medicine relies mainly on the therapeutic potential of stem cells. Mesenchymal stem cells (MSCs), due to their immunosuppressive properties and tissue repair abilities, seem to be an ideal tool for cell-based therapies. Taking into account all available sources of MSCs, perinatal tissues become an attractive source of allogeneic MSCs. The allogeneic MSCs provide "off-the-shelf" cellular therapy, however, their allogenicity may be viewed as a limitation for their use. Moreover, some evidence suggests that MSCs are not as immune-privileged as it was previously reported. Therefore, understanding their interactions with the recipient's immune system is crucial for their successful clinical application. In this review, we discuss both autologous and allogeneic application of MSCs, focusing on current approaches to allogeneic MSCs therapies, with a particular interest in the role of human leukocyte antigens (HLA) and HLA-matching in allogeneic MSCs transplantation. Importantly, the evidence from the currently completed and ongoing clinical trials demonstrates that allogeneic MSCs transplantation is safe and seems to cause no major side-effects to the patient. These findings strongly support the case for MSCs efficacy in treatment of a variety of diseases and their use as an "off-the-shelf" medical product.

Human induced pluripotent stem cell-derived mesenchymal stem cells promote healing via TNF-α-stimulated gene-6 in inflammatory bowel disease models

Therapeutic applications of tissue-derived mesenchymal stem cells (MSCs) are hindered by their limited expansion ability and variation across donors. Human induced pluripotent stem cell (iPSC)-derived MSCs show greater expandability and therefore offer potential for use in tissue repair therapies. Here we explored the regenerative effects of iPSC-MSCs and the mechanisms by which iPSC-MSCs promote mucosal healing via tumor necrosis factor-α-stimulated gene 6 (TSG-6) in mouse models of inflammatory bowel disease (IBD). Human iPSCs were induced to differentiate into MSCs following a clinically compliant protocol. The iPSC-MSC treatment promoted mucosal healing in colitic mice, accompanied by increased epithelial cell proliferation, CD44-positive cells, and Lgr5-positive cells. TSG-6 knockdown in iPSC-MSCs or blocking of hyaluronan–CD44 interactions by PEP-1 abrogated the therapeutic effects of iPSC-MSCs, whereas use of recombinant TSG-6 showed therapeutic effects similar to those of iPSC-MSCs. A mouse or patient-derived organoid culture system was developed. Organoids co-cultured with iPSC-MSCs showed increased epithelial cell proliferation, CD44-positive cells, and Lgr5-positive cells, which was abolished by TSG-6 knockdown. TSG-6-induced promoting effects in organoids were dependent on Akt activation and abrogated by the anti-CD44 antibody or MK2206. In conclusion, iPSC-MSCs promoted epithelial cell proliferation to accelerate mucosal healing in a murine colitis model via TSG-6 through hyaluronan–CD44 interactions in an Akt-dependent manner, demonstrating a patient-specific “off-the-shelf” format for IBD treatment.

Mesenchymal stem cells combined with traditional Chinese medicine (qi-fang-bi-min-tang) alleviates rodent allergic rhinitis

Mesenchymal stem cells (MSCs) have been proved to exert anti-inflammatory effects and regulate immune reactions. Traditional Chinese medicine (TCM), qi-fang-bi-min-tang, is effective for some patients with allergic diseases. However, it remains unclear whether MSCs combined with TCM could benefit the treatment of allergic rhinitis (AR). In this study, we reported an additional effect of TCM (qi-fang-bi-min-tang) on the therapy of AR under MSCs treatment. Intriguingly, we observed that TCM-treated MSCs significantly inhibited the symptoms of AR and reduced the pathological changes of nasal mucosa in ovalbumin (OVA)-induced rats. The expression levels of interferon γ (IFN-γ), interleukin-17 (IL-17), and IL-4 were significantly decreased in the plasma of AR rats after injection of TCM-treated MSCs. TCM-treated MSCs reduced the levels of histamine secreted by mast cells and immunoglobulin E (IgE) secreted by plasma cells. In addition, we found that MSCs combined with TCM had a better therapeutic effect than TCM alone on AR in an OVA-induced mouse model. After OVA induction, MSCs combined with TCM significantly reduced the ratio of T helper type 1 (Th1), Th2, and Th17, but increased the proportion of Treg in the spleen of mice. Consistently, the expression levels of IFN-γ, IL-4, and IL-17 were significantly decreased, but transforming growth factor-β1 was significantly increased in the plasma of AR mice after treated with TCM and MSCs. Our results from both rats and mice indicated that the effects of TCM combined with MSCs on the AR might be through regulating the secretion of Th1, Th2, and Th17 cytokines. This study suggested that TCM (qi-fang-bi-min-tang)-treated MSCs could be used in the clinical therapy of AR.

Dendritic cells and M2 macrophage play an important role in suppression of Th2-mediated inflammation by adipose stem cells-derived extracellular vesicles

Although stem cell-derived extracellular vesicles (EVs) have been shown to facilitate regeneration of injured tissue, there is no report that evaluates the immune-modulating effect of stem cell-derived EVs on Th2-mediated inflammation. In this study, we evaluated the immunomodulatory effects of adipose stem cells (ASCs)-derived EVs on Th2-mediated inflammation induced by Aspergillus protease antigen in lung epithelial cells. The EVs were isolated from supernatant of ASCs and the diameters of EVs were measured by using dynamic light scattering. The mice primary lung epithelial cells and mouse lung epithelial cell line (MLE12) were pre-treated with 200 ng/ml of Aspergillus protease and then treated with 1 μg/ml of ASC-derived EVs. Real time PCR was performed to determine the expression levels of eotaxin, IL-25, TGF-β, and IL-10 mRNAs after EV treatment. To evaluate the role of EVs in macrophage polarization and dendritic cells (DCs) differentiation, in vitro bone marrow-derived macrophage and DCs stimulation assay was performed. EV treatment significantly decreased the expression of eotaxin and IL-25 and increased TGF-β and IL-10 in both lung epithelial cells. EV treatment significantly increased the expression of co-stimulatory molecules such as CD40, CD80, and CD 86 in immature DCs. Furthermore, EV treatment significantly enhanced the gene expression of M2 macrophage marker such as Arg1, CCL22, IL-10, and TGF-β. In conclusion, EVs of ASCs ameliorated Th2-mediated inflammation induced by Aspergillus protease antigen through the activation of dendritic cells and M2 macrophage, accompanied by down-regulation of eotaxin and IL-25, and up-regulation of TGF-β and IL-10 in mouse lung epithelial cells.

Production of Mesenchymal Stem Cells Through Stem Cell Reprogramming

Mesenchymal stem cells (MSCs) possess a broad spectrum of therapeutic applications and have been used in clinical trials. MSCs are mainly retrieved from adult or fetal tissues. However, there are many obstacles with the use of tissue-derived MSCs, such as shortages of tissue sources, difficult and invasive retrieval methods, cell population heterogeneity, low purity, cell senescence, and loss of pluripotency and proliferative capacities over continuous passages. Therefore, other methods to obtain high-quality MSCs need to be developed to overcome the limitations of tissue-derived MSCs. Pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are considered potent sources for the derivation of MSCs. PSC-derived MSCs (PSC-MSCs) may surpass tissue-derived MSCs in proliferation capacity, immunomodulatory activity, and in vivo therapeutic applications. In this review, we will discuss basic as well as recent protocols for the production of PSC-MSCs and their in vitro and in vivo therapeutic efficacies. A better understanding of the current advances in the production of PSC-MSCs will inspire scientists to devise more efficient differentiation methods that will be a breakthrough in the clinical application of PSC-MSCs.

Gallic acid alleviates nasal inflammation via activation of Th1 and inhibition of Th2 and Th17 in a mouse model of allergic rhinitis

Allergic rhinitis (AR) is an allergic nasal disease characterized by nasal obstruction, rhinorrhea, sneezing, and itching. Type 1 helper T cells (Th1)/type 2 helper T cells (Th2) imbalance has been identified as an important immunological mechanism of AR. In addition, up-regulation of type 17 helper T cells (Th17) also increase the risk of developing AR. Gallic acid (3, 4, 5-trihydroxybenzoic acid, GA), a polyphenol natural product, is obtained from various herbs, red wine, and green tea. It is known to have diverse biological effects such as anti-oxidation, anti-inflammation, anti-microbial and anti-cancer. In the present study, the effect of GA on airway inflammation and expression of Th1, Th2 and Th17 cytokines in an ovalbumin (OVA)-induced AR mouse model were investigated. GA alleviated the nasal allergic symptoms, reduced the thickness of nasal mucosa, attenuated goblet cell hyperplasia and eosinophil cell infiltration in the nasal mucosa, decreased the levels of interleukin (IL)-4, IL-5, IL-13 and IL-17 in nasal lavage fluid (NALF), and diminished the levels of OVA-specific IgE, OVA-specific IgG1 and OVA-specific IgG2a in serum. However, GA increased the expression of interferon-gamma and IL-12 in NALF. Taken together, it suggests that GA may be used as a therapeutic agent for AR.