Lats2-Underexpressing Bone Marrow-Derived Mesenchymal Stem Cells Ameliorate LPS-Induced Acute Lung Injury in Mice

Hypoxic bone marrow mesenchymal stem cell-derived exosomal lncRNA XIST attenuates lipopolysaccharide-induced acute lung injury via the miR-455-3p/Claudin-4 axis

Mesenchymal stem cell-derived exosomes and long non-coding RNAs (lncRNAs) have been identified to play a role in acute lung injury (ALI). In this study, we investigated whether exosomal lncRNAs could regulate ALI and the underlying mechanisms. Bone marrow mesenchymal stem cells (BM-MSCs) were pretreated with hypoxia or normoxia, and exosomes were subsequently extracted from normoxic BM-MSCs (Nor-exos) and hypoxic BM-MSCs (Hypo-exos). A rat model of ALI was established via an airway perfusion of lipopolysaccharide (LPS). Exosomes were administered via the tail vein to evaluate the in vivo effect of exosomes in ALI. LPS-exposed RLE-6TN cells were incubated with exosomes to explore their in vitro effect in ALI. A luciferase reporter assay was used to evaluate the interaction between lncRNA XIST and miR-455-3p, as well as miR-455-3p and Claudin-4. We found that the exosomes attenuated LPS-induced ALI and Hypo-Exos exerted a greater therapeutic effect compared with Nor-exos both in vitro and in vivo. Moreover, an abundance of lncRNA XIST was observed in Hypo-exos compared with Nor-exos. Mechanistically, LncRNA XIST functioned as a miR-455-3p sponge and targeted Claudin-4 in ALI. Our results provide novel insight into the role of exosomal lncRNA XIST for the treatment of ALI. Thus, hypoxic pretreatment may represent an effective method for improving the therapeutic effects of exosomes.

Proximal Tubular Lats2 Ablation Exacerbates Ischemia/Reperfusion Injury (IRI)-Induced Renal Maladaptive Repair through the Upregulation of P53

The Hippo pathway mediates renal maladaptive repair after acute kidney injury (AKI), which has been considered a driving force in the progression to chronic kidney disease (CKD). LATS2, a core kinase of the Hippo pathway, exerts non-Hippo-dependent functions in the regulation of the cell cycle and cell fate, providing new insights into AKI and further repair. However, its role remains unknown. Here, we utilized a proximal tubular Lats2 conditional knockout mouse strain (Lats2-CKO) to evaluate the effect of LATS2 deficiency on ischemia/reperfusion-induced AKI-to-CKD transition. Lats2-CKO mice presented with more severe tubular maladaptive repair, inflammatory infiltration, interstitial fibrosis, and apoptosis following AKI. Importantly, we discovered that Lats2 ablation caused the activation of p53, with increased levels of cellular apoptotic molecules (p21, Bax, and cleaved caspase-3), and decreased levels of anti-apoptotic molecules (Bcl-2 and Bcl-xL). Pifithirin-α (p53 inhibitor) effectively attenuated renal fibrosis, inflammation, and apoptosis in Lats2-CKO mice after AKI. Consistently, in vitro Lats2 overexpression decreased p53, p21, Bax and cleaved caspase 3 expression after hypoxia/reoxygenation (H/R) treatment. Of note, the phosphorylation of MDM2, which promotes the ubiquitination degradation of p53, at site Ser186 was decreased in Lats2-CKO kidneys, but increased by Lats2 overexpression in vitro. Therefore, LATS2 deficiency aggravated ischemia/reperfusion injury (IRI)-induced maladaptive repair via regulating the tubular MDM2-p53 axis in AKI-to-CKD transition.

Hippo signaling pathway and respiratory diseases

The hippo signaling pathway is a highly conserved evolutionary signaling pathway that plays an important role in regulating cell proliferation, organ size, tissue development, and regeneration. Increasing evidences consider that the hippo signaling pathway is involved in the process of respiratory diseases. Hippo signaling pathway is mainly composed of mammalian STE20-like kinase 1/2 (MST1/2), large tumor suppressor 1/2 (LATS1/2), WW domain of the Sav family containing protein 1 (SAV1), MOB kinase activator 1 (MOB1), Yes-associated protein (YAP) or transcriptional coactivator with PDZ-binding motif (TAZ), and members of the TEA domain (TEAD) family. YAP is the cascade effector of the hippo signaling pathway. The activation of YAP promotes pulmonary arterial vascular smooth muscle cells (PAVSMCs) proliferation, which leads to pulmonary vascular remodeling; thereby the pulmonary arterial hypertension (PAH) is aggravated. While the loss of YAP leads to high expression of inflammatory genes and the accumulation of inflammatory cells, the pneumonia is consequently exacerbated. In addition, overexpressed YAP promotes the proliferation of lung fibroblasts and collagen deposition; thereby the idiopathic pulmonary fibrosis (IPF) is promoted. Moreover, YAP knockout reduces collagen deposition and the senescence of adult alveolar epithelial cells (AECs); hence the IPF is slowed. In addition, hippo signaling pathway may be involved in the repair of acute lung injury (ALI) by promoting the proliferation and differentiation of lung epithelial progenitor cells and intervening in the repair of pulmonary capillary endothelium. Moreover, the hippo signaling pathway is involved in asthma. In conclusion, the hippo signaling pathway is involved in respiratory diseases. More researches are needed to focus on the molecular mechanisms by which the hippo signaling pathway participates in respiratory diseases.

Electroacupuncture attenuates pulmonary vascular remodeling in a rat model of chronic obstructive pulmonary disease via the VEGF/PI3K/Akt pathway

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. Pulmonary vascular remodeling is the main pathological feature of COPD. Vascular endothelial growth factor (VEGF), the key regulator of angiogenesis, mediates activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, which regulates the proliferation and migration of vascular endothelial cells and plays important roles in pulmonary angiogenesis and remodeling in COPD. Here, the efficacy of electroacupuncture (EA) with respect to regulation of microvascular remodeling induced by VEGF/PI3K/Akt was evaluated in a rat model of COPD.

METHODS

Rats were randomly assigned to blank, COPD model, EA and sham acupuncture (SA) groups. Rats in the EA group received EA at GV14, BL13 and BL23 three times per week, while those in the SA group, as a control, received shallow and minimal electrostimulation at sites 5-10 mm away from the traditional acupuncture point locations. After 2, 4 and 8 weeks of treatment, the optimal treatment duration was determined according to the results of lung function, lung pathology and inflammatory factor levels. Then, microvessel density, protein levels and mRNA expression of selected VEGF/PI3K/Akt pathway intermediates were determined by immunofluorescence, immunohistochemistry and Western blot analysis, and mRNA qRT-PCR, respectively.

RESULTS

EA improved lung function and lung tissue histopathology, with the best effect after 8 weeks of treatment, as noted by reduced density of lung microvessels and expression of angiogenesis-related factors (VEGF and endothelin (ET)-1). EA-treated COPD rats exhibited reduced VEGF, VEGF receptor 2 (VEGFR2), ET-1 mRNA and VEGF, VEGFR2, phosphorylated (p)-VEGFR2, PI3K, Akt, p-Akt, mammalian target of rapamycin (mTOR), and p-mTOR at the protein level in comparison with untreated and SA-treated COPD model rats.

CONCLUSION

EA had beneficial effects on COPD in this animal model including reduced pulmonary vascular remodeling via mechanisms possibly related to the VEGF/PI3K/Akt pathway.

Trelagliptin Alleviates Lipopolysaccharide (LPS)-Induced Inflammation and Oxidative Stress in Acute Lung Injury Mice

Acute lung injury (ALI) is an urgent disease lacking effective therapies, resulting in relatively high morbidity and mortality. The pathological mechanism of ALI is reported to be related to excessive inflammation and activated oxidative stress. The present study aims to investigate the protective effects of the DPP-4 inhibitor Trelagliptin against lipopolysaccharide (LPS)-induced ALI and the underlying mechanism. LPS was used to induce ALI mice models. The pathological condition of ALI mice was evaluated using MPO activity assay, lung wet to dry weight ratio detection, and HE staining on the lung tissues. Lung function was assessed using a spirometer. The oxidative stress level in the lung tissues was checked by MDA measurement and GPx detection using commercial kits. The leukocyte and neutrophil numbers were determined using a hemocytometer and the total concentration of protein in the BALF was detected using a bicinchoninic acid method. The expression levels of TNF-α, IL-6, and CXCL2 in the lung tissues were evaluated using qRT-PCR and ELISA. Western blot analysis was used to determine the expression levels of TLR4 and p-NF-κB p65. LPS-induced elevated MPO activity, pulmonary wet to dry weight ratio, airway resistance (RAW), the total number of leukocytes and neutrophils, production of inflammatory factors, decreased pulmonary dynamic compliance (Cdyn), and peak expiratory flow (PEF), and an aggravated histopathological state (such as disordered alveolar structure, significant pulmonary interstitial edema, and large numbers of red blood cells and inflammatory cells in the alveolar cavity) were significantly reversed by the administration of Trelagliptin. The TLR4/NF-κB signaling pathway was activated and oxidative stress was induced by stimulation with LPS; however, both effects were suppressed by the administration of Trelagliptin. Trelagliptin might alleviate LPS-induced inflammation and oxidative stress in acute lung injury mice.

BMSC-Derived Exosomes Ameliorate LPS-Induced Acute Lung Injury by miR-384-5p-Controlled Alveolar Macrophage Autophagy

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common critical diseases. Bone marrow mesenchymal stem cell (BMSC) transplantation is previously shown to effectively rescue injured lung tissues. The therapeutic mechanism of BMSC-derived exosomes is not fully understood. Here, we investigated the BMSC-derived exosomal microRNAs (miRNAs) on effecting lipopolysaccharide- (LPS-) induced ALI and its mechanism. In vitro, rat alveolar macrophages were treated with or without exosomes in the presence of 10 μg/ml LPS for 24 h. Cell viability was determined with Cell Counting Kit-8 assay. Apoptotic ratio was determined with TUNEL and Annexin V-FITC/PI double staining. The levels of miR-384-5p and autophagy-associated genes were measured by RT-qPCR and western blot. Autophagy was observed by TEM and assessed by means of the mRFP-GFP-LC3 adenovirus transfection assay. In vivo, we constructed LPS-induced ALI rat models. Exosomes were injected into rats via the caudal vein or trachea 4 h later after LPS treatment. The lung histological pathology was determined by H&E staining. Pulmonary vascular permeability was assessed by wet-to-dry weight ratio and Evans blue dye leakage assay, and inflammatory cytokines in serum and BALF were measured by ELISA. Furthermore, the therapeutic mechanism involved in miR-384-5p and Beclin-1 was determined. The results showed that BMSC-derived exosomes were taken up by the alveolar macrophages and attenuated LPS-induced alveolar macrophage viability loss and apoptosis. Exosomes effectively improved the survival rate of ALI rats within 7 days, which was associated with alleviating lung pathological changes and pulmonary vascular permeability and attenuating inflammatory response. Furthermore, this study for the first time found that miR-384-5p was enriched in BMSC-derived exosomes, and exosomal miR-384-5p resulted in relieving LPS-injured autophagy disorder in alveolar macrophages by targeting Beclin-1. Therefore, exosomal miR-384-5p could be demonstrated as a promising therapeutic strategy for ALI/ARDS.

Therapeutic mechanisms of mesenchymal stem cells in acute respiratory distress syndrome reveal potentials for Covid-19 treatment

The mortality rate of critically ill patients with acute respiratory distress syndrome (ARDS) is 30.9% to 46.1%. The emergence of the coronavirus disease 2019 (Covid-19) has become a global issue with raising dire concerns. Patients with severe Covid-19 may progress toward ARDS. Mesenchymal stem cells (MSCs) can be derived from bone marrow, umbilical cord, adipose tissue and so on. The easy accessibility and low immunogenicity enable MSCs for allogeneic administration, and thus they were widely used in animal and clinical studies. Accumulating evidence suggests that mesenchymal stem cell infusion can ameliorate ARDS. However, the underlying mechanisms of MSCs need to be discussed. Recent studies showed MSCs can modulate immune/inflammatory cells, attenuate endoplasmic reticulum stress, and inhibit pulmonary fibrosis. The paracrine cytokines and exosomes may account for these beneficial effects. In this review, we summarize the therapeutic mechanisms of MSCs in ARDS, analyzed the most recent animal experiments and Covid-19 clinical trial results, discussed the adverse effects and prospects in the recent studies, and highlight the potential roles of MSC therapy for Covid-19 patients with ARDS.

Improved Differentiation Ability and Therapeutic Effect of miR-23a-3p Expressing Bone Marrow-Derived Mesenchymal Stem Cells in Mice Model with Acute Lung Injury

Background and Objectives

Implantation of bone marrow-derived mesenchymal stem cells (BMSCs) has been recognized as an effective therapy for attenuating acute lung injury (ALI). This study aims to discover microRNA (miRNA)-mediated improvement of BMSCs-based therapeutic effects.

Methods and Results

Mice were treated with lipopolysaccharide (LPS) for induction of ALI. BMSCs with lentivirus-mediated expression of miR-23b-3p or fibroblast growth factor 2 (FGF2) were intratracheally injected into the mice with ALI. The expressions of miR-23b-3p, FGF2, Occludin, and surfactant protein C (SPC) in lung tissues were analyzed by immunoblot or quantitative reverse transcription polymerase chain reaction. Histopathological changes in lung tissues were observed via hematoxylin-eosin staining. Lung edema was assessed by the ratio of lung wet weight/body weight (LWW/BW). The levels of interleukin (IL)-1β, IL-6, IL-4, and IL-8 in bronchoalveolar lavage fluid (BALF) were assessed by ELISA. LPS injection downregulated the expressions of miR-23b-3p, SPC and Occludin in the lung tissues, increased the LWW/BW ratio and aggravated histopathological abnormalities, while upregulating IL-1β, IL-6, IL-4, and IL-8 in the BALF. Upregulated miR-23b-3p counteracted LPS-induced effects, whereas downregulated miR-23b-3p intensified LPS-induced effects. FGF2, which was downregulated by miR-23b-3p upregulation, was a target gene of miR-23b-3p. Overexpressing FGF2 downregulated the expressions of miR-23b-3p, SPC and Occludin, increased the LWW/BW ratio and aggravated histopathological abnormalities, while upregulating IL-1β, IL-6, IL-4, and IL-8, and it offset miR-23b-3p upregulation-caused effects on the ALI mice.

Conclusions

Overexpression of miR-23b-3p in BMSCs strengthened BMSC-mediated protection against LPS-induced mouse acute lung injury via targeting FGF2.

Bone marrow mesenchymal stem cell-derived exosomes alleviate hyperoxia-induced lung injury via the manipulation of microRNA-425

BACKGROUND

Hyperoxia-induced lung injury (HILI) is an acute lung injury (LI) induced by extended periods of exposure to hyperoxia. Alleviating LI by bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exos) and microRNAs (miRs) has been previously reported. This study is devised to probe the interaction between BMSCs-Exos and miR-425 in HILI.

METHODS

Firstly, BMSCs-Exos were isolated and identified. Then, HILI rat models and RLE-6TN cell models were successfully established and treated by BMSCs-Exos. Afterwards, functional assays were conducted to explore cell biological behaviors in models, with miR-425 expression detected. Then, the target relation between miR-425 and PTEN was clarified by luciferase reporter assay. Eventually, expression of PTEN and the PI3K/Akt axis was assessed by Western blotting and qRT-PCR.

RESULTS

BMSCs-Exos promoted miR-425 expression and attenuated HILI and H₂O₂ induced RLE-6TN cell injury as evidence by alleviated lung cell injury, decreased TUNEL-positive cells, induced cell viability and declined apoptosis (all p < 0.05). Besides, when miR-425 was knocked-down, the protective role of BMSCs-Exos in HILI was also reduced (all p < 0.05). miR-425 targeted PTEN mRNA, whose upregulation reversed the protective role of BMSCs-Exos in HILI (all p < 0.05). BMSCs-Exos improved the quenched levels of the PI3K/AKT axis in HILI (all p < 0.05).

CONCLUSION

Our data supported that miR-425 in BMSCs-Exos inhibits HILI by targeting PTEN and upregulating the PI3K/AKT axis. This study may provide personalized interventions for HILI remedy.