Protective Role of Adipose-Derived Stem Cells in Staphylococcus aureus-Induced Lung Injury is Mediated by RegIIIγ Secretion

Effects of Staphylococcus aureus on stem cells and potential targeted treatment of inflammatory disorders

Due to the advanced studies on stem cells in developmental biology, the roles of stem cells in the body and their phenotypes in related diseases have not been covered clearly. Meanwhile, with the intensive research on the mechanisms of stem cells in regulating various diseases, stem cell therapy is increasingly being attention because of its effectiveness and safety. As one of the most widely used stem cell in stem cell therapies, hematopoietic stem cell transplantation shows huge advantage in treatment of leukemia and other blood-malignant diseases. Besides, due to the effect of anti-inflammatory and immunomodulatory, mesenchymal stem cells could be a potential therapeutic strategy for variety infectious diseases. In this review, we summarized the effects of Staphylococcus aureus (S. aureus) and its components on different types of adult stem cells and their downstream signaling pathways. Also, we reviewed the roles of different kinds of stem cells in various disease models caused by S. aureus, providing new insights for applying stem cell therapy to treat infectious diseases.

Adipose-derived stem cells decolonize skin Staphylococcus aureus by enhancing phagocytic activity of peripheral blood mononuclear cells in the atopic rats

Staphylococcus aureus (S. aureus) is known to induce apoptosis of host immune cells and impair phagocytic clearance, thereby being pivotal in the pathogenesis of atopic dermatitis (AD). Adipose-derived stem cells (ASCs) exert therapeutic effects against inflammatory and immune diseases. In the present study, we investigated whether systemic administration of ASCs restores the phagocytic activity of peripheral blood mononuclear cells (PBMCs) and decolonizes cutaneous S. aureus under AD conditions. AD was induced by injecting capsaicin into neonatal rat pups. ASCs were extracted from the subcutaneous adipose tissues of naïve rats and administered to AD rats once a week for a month. Systemic administration of ASCs ameliorated AD-like symptoms, such as dermatitis scores, serum IgE, IFN-γ⁺/IL-4⁺ cell ratio, and skin colonization by S. aureus in AD rats. Increased FasL mRNA and annexin V⁺/7-AAD⁺ cells in the PBMCs obtained from AD rats were drastically reversed when co-cultured with ASCs. In contrast, both PBMCs and CD163⁺ cells bearing fluorescent zymosan particles significantly increased in AD rats treated with ASCs. Additionally, the administration of ASCs led to an increase in the mRNA levels of antimicrobial peptides, such as cathelicidin and β-defensin, in the skin of AD rats. Our results demonstrate that systemic administration of ASCs led to decolonization of S. aureus by attenuating apoptosis of immune cells in addition to restoring phagocytic activity. This contributes to the improvement of skin conditions in AD rats. Therefore, administration of ASCs may be helpful in the treatment of patients with intractable AD.

Novel Antibacterial Properties of the Human Dental Pulp Multipotent Mesenchymal Stromal Cell Secretome

It is well recognized that clearance of bacterial infection within the dental pulp precedes pulpal regeneration. However, although the regenerative potential of the human dental pulp has been investigated extensively, its antimicrobial potential remains to be examined in detail. In the current study bactericidal assays were used to demonstrate that the secretome of dental pulp multipotent mesenchymal stromal cells (MSCs) has direct antibacterial activity against the archetypal Gram-positive and Gram-negative bacteria, Staphylococcus aureus and Escherichia coli, respectively, as well as the oral pathogens Streptococcus mutans, Lactobacillus acidophilus, and Fusobacterium nucleatum. Furthermore, a cytokine/growth factor array, enzyme-linked immunosorbent assays, and antibody blocking were used to show that cytokines and growth factors present in the dental pulp MSC secretome, including hepatocyte growth factor, angiopoietin-1, IL-6, and IL-8, contribute to this novel antibacterial activity. This study elucidated a novel and diverse antimicrobial secretome from human dental pulp MSCs, suggesting that these cells contribute to the antibacterial properties of the dental pulp. With this improved understanding of the secretome of dental pulp MSCs and its novel antibacterial activity, new evidence for the ability of the dental pulp to fight infection and restore functional competence is emerging, providing further support for the biological basis of pulpal repair and regeneration.

Single-Cell RNA Sequencing Reveals the Interaction of Injected ADSCs with Lung-Originated Cells in Mouse Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a severe chronic lung disease with little effective treatment options other than lung transplantation. Adipose-derived mesenchymal stem cells (ADSCs) have been shown to exert therapeutic effects on PF, but the underlying mechanisms remain to be further elucidated. Here, we show the interaction of ADSCs and lung-originated cells at the single-cell level, using bleomycin- (BLM-) induced mice PF model and green fluorescent protein– (GFP–) labeled mouse ADSCs. The intratracheally injected ADSCs were successfully recollected with flow cytometry and, together with lung-originated cells, were subjected to single-cell RNA sequencing (scRNA-seq). The ADSC treatment drastically changed the transcriptomic profile and composition of lung cells, especially macrophages. We explored the signal pathway interactions between ADSCs and lung-originated cells, showing potentially regulative pathways including NGR, ANNEXIN, HGF, and PERIOSTIN. Our data indicate that the injected ADSCs increased the number of Trem2⁺ antiinflammatory lung macrophages and lowered further inflammation and fibrosis in the lung. Our work realized the direct analysis of injected ADSCs to explore its in vivo interaction with the lung environment under PF and may provide critical information for future engineering of ADSCs to achieve better therapeutic effects in PF.

Babaodan controls excessive immune responses and may represent a cytokine-targeted agent suitable for COVID-19 treatment

It has become evident that the actions of pro-inflammatory cytokines and/or the development of a cytokine storm are responsible for the occurrence of severe COVID-19 during SARS-CoV-2 infection. Although immunomodulatory mechanisms vary among viruses, the activation of multiple TLRs that occurs primarily through the recruitment of adapter proteins such as MyD88 and TRIF contributes to the induction of a cytokine storm. Based on this, controlling the robust production of pro-inflammatory cytokines by macrophages may be applicable as a cellular approach to investigate potential cytokine-targeted therapies against COVID-19. In the current study, we utilized TLR2/MyD88 and TLR3/TRIF co-activated macrophages and evaluated the anti-cytokine storm effect of the traditional Chinese medicine (TCM) formula Babaodan (BBD). An RNA-seq-based transcriptomic approach was used to determine the molecular mode of action. Additionally, we evaluated the anti-inflammatory activity of BBD in vivo using a mouse model of post-viral bacterial infection-induced pneumonia and seven severely ill COVID-19 patients. Our study reveals the protective role of BBD against excessive immune responses in macrophages, where the underlying mechanisms involve the inhibition of the NF-κB and MAPK signaling pathways. In vivo, BBD significantly inhibited the release of IL-6, thus resulting in increased survival rates in mice. Based on limited data, we demonstrated that severely ill COVID-19 patients benefited from BBD treatment due to a reduction in the overproduction of IL-6. In conclusion, our study indicated that BBD controls excessive immune responses and may thus represent a cytokine-targeted agent that could be considered to treating COVID-19.

Effect of HBO therapy on adipose-derived stem cells, fibroblasts and co-cultures: In vitro study of oxidative stress, angiogenic potential and production of pro-inflammatory growth factors in co-cultures1

BACKGROUND: A key moderator of wound healing is oxygen. Wound healing is a dynamic and carefully orchestrated process involving blood cells, cytokines, parenchymal cells (i.e. fibroblasts and mesenchymal stem cells) and extracellular matrix reorganization. Human adipose derived stem cells as well as human fibroblasts produce soluble factors, exhibit diverse effects on inflammation and anti inflammation response and are involved in wound healing processes. Hyperbaric oxygen therapy is an effective adjunct treatment for ischemic disorders such as chronic infection or chronic wounds. In vitro effects of hyperbaric oxygen therapy on human cells were presented in many studies except for those on mono- and co-cultures of human adipose derived stem cells and fibroblasts. OBJECTIVE: The aim of this study was to investigate the effects of hyperbaric oxygen therapy on mono- and co-cultures of human adipose derived stem cells and fibroblasts. METHODS: Mono- and co-cultures from human adipose derived stem cells and fibroblasts were established. These cultures were exposed to hyperbaric oxygen therapy every 24 h for five consecutive days. Measuring experiments were performed on the first, third and fifth day. Therapy effects on the expression of VEGF, IL 6 and reactive oxygen species were investigated. RESULTS: After exposure to hyperbaric oxygen, cell culturess showed a significant increase in the expression of VEGF after 3 and 5 days. All cultures showed significantly reduced formation of reactive oxygen species throughout the experiments. The expression of IL-6 decreased during the experiment in mono-cultures of human adipose derived stem cells and co-cultures. In contrast, mono-cultures of human skin fibroblasts showed an overall significantly increased expression of IL-6. CONCLUSIONS: Hyperbaric oxygen therapy leads to immunmodulatory and proangiogenetic effects in a wound-like enviroment of adipose derived stem cells and fibroblasts.

Protective effect of Jie-Geng-Tang against Staphylococcus aureus induced acute lung injury in mice and discovery of its effective constituents

ETHNOPHARMACOLOGICAL RELEVANCE

Jie-Geng-Tang (JGT), a famous traditional Chinese medicine prescription, consists of Platycodonis Radix and Glycyrrhizae Radix et Rhizoma. According to traditional medicinal theory, JGT exerts various effects, including apocenosis, detoxifying, moisturizing the lung and relieving sore throat. It is often used to treat throat inflammation and lung diseases.

AIM OF THE STUDY

To determine the protective effect of JGT on Staphylococcus aureus (S. aureus)-induced acute lung injury (ALI) in mice and to identify the compounds in the prescription that may be responsible for antibacterial activity.

MATERIALS AND METHODS

The protective effect of JGT was assessed using S. aureus-induced ALI mice (i.g., 2.7 g/kg/day). Bacterial burden, pathological morphology, cytokine levels of TNF-α, IL-1β, KC, and MIP-2 were evaluated in the lung and bronchoalveolar lavage fluid at 24 h post-infection, respectively. Twenty three compounds in the prescription were evaluated for their minimum inhibitory concentration (MIC) in vitro by means of microbroth dilution method against S. aureus. The antibacterial effects in vitro of licochalcone A and isoliquiritigenin were also investigated by transmission electron microscopy. In vivo antibacterial activities of licochalcone A and isoliquiritigenin were evaluated by survival rates, bacterial burden, and pathological morphology of lung tissues on S. aureus-induced ALI in mice (i.p., 160 mg/kg/day).

RESULTS

Pretreatment with JGT significantly improved the pathological morphology of lung tissues on S. aureus-induced ALI in mice, accompanied with the reduced bacterial burden in the lungs and inhibited expression of inflammatory cytokine levels at 24 h post-infection. Five compounds, namely licochalcone A, licoisoflavone B, glyasperin A, isoliquiritigenin, and licochalcone B from Jie-Geng-Tang displayed good antibacterial activities against S. aureus (MIC < 128 μg/mL). Furthermore, applications of licochalcone A and isoliquiritigenin resulted in the increased survival rates, reduced bacterial burden in the lungs, and improved pathological morphology of lung tissues in S. aureus infected mice.

CONCLUSION

The study demonstrated that Jie-Geng-Tang presented protective role of acute lung injury, which supported its traditional use for the treatment of lung diseases. Licochalcone A, isoliquiritigenin, licoisoflavone B, glyasperin A, and licochalcone B might contribute to the antibacterial activity of JGT on S. aureus-induced acute lung injury. The anti-S. aureus activity of licoisoflavone B, glyasperin A, and licochalcone B in vitro, as well as the anti-S. aureus activity of licochalcone A in vivo, were first reported in this study.

Autophagy regulates the therapeutic potential of adipose-derived stem cells in LPS-induced pulmonary microvascular barrier damage

Adipose-derived stem cells (ADSCs) have been shown to be beneficial in some pulmonary diseases, and the paracrine effect is the major mechanism underlying ADSC-based therapy. Autophagy plays a crucial role in maintaining stem cell homeostasis and survival. However, the role of autophagy in mediating ADSC paracrine effects has not been thoroughly elucidated. We examined whether ADSCs participate in lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cell (PMVEC) barrier damage in a paracrine manner and illuminated the role of autophagy in regulating ADSC paracrine effects. PMVECs and ADSCs with or without autophagy inhibition were cocultured without intercellular contact, and the microvascular barrier function was assessed after LPS treatment. ADSC paracrine function was evaluated by detecting essential growth factors for endothelial cells. For in vivo experiments, ADSCs with or without autophagy inhibition were transplanted into LPS-induced lung-injury mice, and lung injury was assessed. ADSCs significantly alleviated LPS-induced microvascular barrier injury. In addition, ADSC paracrine levels of VEGF, FGF, and EGF were induced by LPS treatment, especially in the coculture condition. Inhibiting autophagy weakened the paracrine function and the protective effects of ADSCs on microvascular barrier injury. Moreover, ADSC transplantation alleviated LPS-induced lung injury, and inhibiting autophagy markedly weakened the therapeutic effect of ADSCs on lung injury. Together, these findings show that ADSC paracrine effects play a vital protective role in LPS-induced pulmonary microvascular barrier injury. Autophagy is a positive mediating factor in the paracrine process. These results are helpful for illuminating the role and mechanism of ADSC paracrine effects and developing effective therapies in acute lung injury.

Current understanding of the therapeutic benefits of mesenchymal stem cells in acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a multifaceted lung disorder in which no specific therapeutic intervention is able to effectively improve clinical outcomes. Despite an improved understanding of molecular mechanisms and advances in supportive care strategies, ARDS remains associated with high mortality, and survivors usually face long-term morbidity. In recent years, preclinical studies have provided mounting evidence of the potential of mesenchymal stem cell (MSC)-based therapies in lung diseases and critical illnesses. In several models of ARDS, MSCs have been demonstrated to induce anti-inflammatory and anti-apoptotic effects, improve epithelial and endothelial cell recovery, and enhance microbial and alveolar fluid clearance, thus resulting in improved lung and distal organ function and survival. Early-stage clinical trials have also demonstrated the safety of MSC administration in patients with ARDS, but further, large-scale investigations are required to assess the safety and efficacy profile of these therapies. In this review, we summarize the main mechanisms whereby MSCs have been shown to exert therapeutic effects in experimental ARDS. We also highlight questions that need to be further elucidated and barriers that must be overcome in order to efficiently translate MSC research into clinical practice.

miR‑124 regulates the osteogenic differentiation of bone marrow‑derived mesenchymal stem cells by targeting Sp7

MicroRNAs (miRNAs) are novel key regulators of cellular differentiation. miR‑124 has been reported to regulate osteogenic differentiation of bone marrow‑derived mesenchymal stem cells (BMSCs). However, the specific mechanisms involved have not yet been fully elucidated. The present study aimed to investigate the effect of miR‑124 on osteogenic differentiation of BMSCs and its underlying mechanisms. In the present study, it was found that alkaline phosphatase (ALP) activity, osteocalcin (OC) secretion, and the protein levels of osterix (Sp7) and runt‑related transcription factor 2 (Runx2) were significantly increased, whereas the expression of miR‑124 was decreased in a time‑dependent manner during osteogenic differentiation of BMSCs. Following overexpression of miR‑124 via transfection of miR‑124 mimics in BMSCs, Runx2 protein expression and ALP activity were significantly decreased. By contrast, inhibition of miR‑124 expression led to an increase in ALP activity and Runx2 expression. Sp7 expression was suppressed in BMSCs transfected with miR‑124 mimics while increased when miR‑124 expression was inhibited, indicating that miR‑124 regulates the expression of Sp7. Moreover, a luciferase reporter assay further verified that Sp7 is the direct target of miR‑124. Finally, the effect of miR‑124 inhibitor on promoting the differentiation of BMSCs was abolished following treatment with a small interfering RNA targeting Sp7. Taken together, the present study demonstrates that miR‑124 inhibits the osteogenic differentiation of BMSCs by targeting Sp7.

IL22 furthers malignant transformation of rat mesenchymal stem cells, possibly in association with IL22RA1/STAT3 signaling

Mesenchymal stem cells (MSCs) hold great promise as potential therapies for tumors through the delivery of various anticancer agents. However, exogenous tissue‑derived MSCs, such as those of bone marrow, have exhibited a tendency for malignant transformation in the tumor microenvironment. This issue remains controversial and is poorly understood. In the present study, the role of interleukin 22 (IL22)/IL22 receptor subunit α 1 (IL22RA1) and signal transducer and activator of transcription 3 (STAT3) signaling in the malignant transformation of MSCs was investigated. Following isolation of rat MSCs and their indirect co‑culture with C6 glioma cells, the transformed MSCs exhibited tumor cell characteristics. The Cancer Genome Atlas‑Glioblastoma Multiforme analysis revealed that primary and recurrent glioblastomas have increased IL22RA1 expression, compared with normal tissues, whereas the expression of IL22 was low in glioblastoma and normal tissues. mRNA and protein expression levels of IL22RA1 were significantly increased in the MSCs co‑cultured with C6 glioma cells. Furthermore, MSCs incubated with IL22 exhibited increased proliferation, migration and invasion. STAT3 demonstrated activation and nuclear translocation in the presence of IL22. Additionally, STAT3 small interfering RNA significantly inhibited the migration and invasion ability of MSCs, and the expression of the STAT3 downstream targets cyclin D1 and B‑cell lymphoma‑extra large under IL22 stimulation, indicating that IL22 also promoted MSC migration and invasion through STAT3 signaling. These data indicated that IL22 serves a critical role in the malignant transformation of rat MSCs, which is associated with an enhancement of the IL22RA1/STAT3 signaling pathway in the tumor microenvironment.

Mast cells participate in regulation of lung-gut axis during Staphylococcus aureus pneumonia

Objectives

The lung‐gut axis is known to be involved in the pathogenesis of Staphylococcus aureus pneumonia. However, the underlying mechanisms remain unclear. We examined the role of pulmonary mast cells (MCs) in the regulation of the lung‐gut axis during S. aureus pneumonia.

Materials and Methods

We created a mouse model of S. aureus pneumonia using MC‐deficient mice (Kit^{W‐sh/W‐sh}) and examined the level of inflammation, bacterial burden, expression of cathelicidin‐related antimicrobial peptide (CRAMP) and composition of the gut microbiota. We further evaluated anti‐bacterial immunity by administering bone marrow MCs (BMMCs) or CRAMP into the lungs of Kit^{W‐sh/W‐sh} mice.

Results

After S. aureus challenge, the MC‐deficient mice, compared with wild‐type (WT) mice, displayed attenuated lung inflammation, decreased expression of CRAMP, higher bacterial lung load and disturbance of the intestinal microbiota. Adoptive transfer of BMMCs into the lung effectively reconstituted the host defence against S. aureus in Kit^{W‐sh/W‐sh} mice, thus resulting in recovery of S. aureus pneumonia‐induced intestinal dysfunction. Similarly, exogenous administration of CRAMP significantly enhanced anti‐bacterial immunity in the lungs of MC‐deficient mice.

Conclusions

This study provides evidence for the involvement of MCs in the regulation of the lung‐gut axis during S. aureus pneumonia.

The antibacterial effect of mesenchymThe antibacterial effect of mesenchymal stem cells on graft infections: An experimental studyal stem cells on graft infections: An experimental study

Background

In this study, we aimed to investigate the antibacterial effects of mesenchymal stem cells, compared to tigecycline, on graft infection related with methicillin-resistant Staphylococcus epidermidis in a rat model.

Methods

A total of 42 male adult Wistar rats (age >6 months; weight 300 to 350 g) were divided into six groups including seven rats in each. Group 0 did not undergo any procedure; Group 1 was infected, but untreated; Group 2 was infected and treated with tigecycline without graft placement; Group 3 was infected and received mesenchymal stem cells without graft placement; Group 4 was infected and treated with tigecycline after graft placement; Group 5 was infected and treated with mesenchymal stem cells after graft placement. The pockets created were either left empty or implanted with Dacron grafts. Treatment was commenced at 48 h. Specimens were collected on Day 13. Perigraft tissues were evaluated histopathologically and bacterial colony numbers were counted.

Results

No bacterial colonization was observed in Group 0, whereas there was a significant colonization in Group 1. Complete eradication was achieved in Group 2 and Group 3 (graft-free groups), and near-complete eradication was achieved in Group 4 and Group 5 (graft-implanted groups). The histopathological findings significantly differed between Group 1-Group 2 and between Group 1-Group 3 (graft-free groups). The histopathological findings were similar between Group 2-Group 3 and between Group 4-Group 5.

Conclusion

Our study results suggest that mesenchymal stem cells may be a novel, contemporary alternative to antibiotherapy and may decrease the bio-burden of Staphylococcus at the infected graft areas, and mesenchymal stem cell treatment may be as effective as tigecycline.