Exosome-based Therapy for Bronchopulmonary Dysplasia

The calcineurin-NFATc pathway modulates the lipid mediators in BAL fluid extracellular vesicles, thereby regulating microvascular endothelial cell barrier function

Extracellular vesicles mediate intercellular communication by transporting biologically active macromolecules. Our prior studies have demonstrated that the nuclear factor of activated T cell cytoplasmic member 3 (NFATc3) is activated in mouse pulmonary macrophages in response to lipopolysaccharide (LPS). Inhibition of NFATc3 activation by a novel cell-permeable calcineurin peptide inhibitor CNI103 mitigated the development of acute lung injury (ALI) in LPS-treated mice. Although pro-inflammatory lipid mediators are known contributors to lung inflammation and injury, it remains unclear whether the calcineurin-NFATc pathway regulates extracellular vesicle (EV) lipid content and if this content contributes to ALI pathogenesis. In this study, EVs from mouse bronchoalveolar lavage fluid (BALF) were analyzed for their lipid mediators by liquid chromatography in conjunction with mass spectrometry (LC-MS/MS). Our data demonstrate that EVs from LPS-treated mice contained significantly higher levels of arachidonic acid (AA) metabolites, which were found in low levels by prior treatment with CNI103. The catalytic activity of lung tissue cytoplasmic phospholipase A2 (cPLA2) increased during ALI, correlating with an increased amount of arachidonic acid (AA) in the EVs. Furthermore, ALI is associated with increased expression of cPLA2, cyclooxygenase 2 (COX2), and lipoxygenases (5-LOX, 12-LOX, and 15-LOX) in lung tissue, and pretreatment with CNI103 inhibited the catalytic activity of cPLA2 and the expression of cPLA2, COX, and LOX transcripts. Furthermore, co-culture of mouse pulmonary microvascular endothelial cell (PMVEC) monolayer and NFAT-luciferase reporter macrophages with BALF EVs from LPS-treated mice increased the pulmonary microvascular endothelial cell (PMVEC) monolayer barrier permeability and luciferase activity in macrophages. However, EVs from CNI103-treated mice had no negative impact on PMVEC monolayer barrier integrity. In summary, BALF EVs from LPS-treated mice carry biologically active NFATc-dependent, AA-derived lipids that play a role in regulating PMVEC monolayer barrier function.

Umbilical cord blood exosomes from very preterm infants with bronchopulmonary dysplasia aggravate lung injury in mice

Bronchopulmonary dysplasia (BPD) is characterized by abnormal development of the blood vessels and alveoli in lungs, which largely occurs in premature infants. Exosomes (EXO) from very preterm infants (VPI) with BPD (BPD-EXO) impair angiogenic activities of human umbilical vein endothelial cells (HUVECs) via EXO-miRNAs cargo. This study aimed to determine whether and how BPD-EXO affect the development of BPD in a mouse model. We showed that treating BPD mice with BPD-EXO chronically and irreversibly aggravated lung injury. BPD-EXO up-regulated 139 and down-regulated 735 genes in the mouse lung tissue. These differentially expressed genes were enriched to the MAPK pathway (e.g., Fgf9 and Cacna2d3), which is critical to angiogenesis and vascular remodeling. BPD-EXO suppressed expression of Fgf9 and Cacna2d3 in HUVECs and inhibited migration, tube formation, and increased cell apoptosis in HUVECs. These data demonstrate that BPD-EXO aggravate lung injury in BPD mice and impair lung angiogenesis, plausibly leading to adverse outcomes of VPI with BPD. These data also suggest that BPD-EXO could serve as promising targets for predicting and treating BPD.

MSC-EXO and tempol ameliorate bronchopulmonary dysplasia in newborn rats by activating HIF-1α

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a major complication of premature infants and an important cause of morbidity and mortality. This study investigates the effect of the combination of mesenchymal stem cells-derived exosomes (MSC-EXO) and tempol on BPD and analyzes its mechanism.

METHODS

MSC-EXO was extracted by centrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis, and western blot analysis (WB). Tidal volume (TV), minute ventilation (MV), peak inspiratory flow (PIF), and dynamic pulmonary compliance (Cdyn) of rats were measured by BuxCo pulmonary function experimental platform. Hematoxylin-eosin staining was performed to observe the lung morphology and radical alveolar count (RAC) and mean linear intercept (MLI) were assessed. Immunofluorescence (IF) was conducted to detect the expression of CD31 and α-SMA in pulmonary blood vessels. The kits were used to calculate malondialdehyde (MDA), superoxide dismutase (SOD), and total antioxidant capacity (TAOC) concentration in lung tissue. Enzyme linked immunosorbent assay was applied to detect the levels of IL-1β, IL-17, IL-6, and IFN-γ in bronchoalveolar lavage fluid. In addition, the expressions of HIF-1α, vascular endothelial growth factor (VEGF), p-PI3K, and p-AKT were analyzed by WB and IF.

RESULTS

We successfully extracted and identified MSC-EXO. In BPD rats, TV, MV, PIF, and Cdyn decreased, alveoli were simplified, and the number of interalveoli small vessels, blood vessel density decreased. Moreover, RAC, CD31, TAOC, and SOD decreased, and MLI, α-SMA, MDA, IL-1β, IL-17, IL-6, and IFN-γ increased, which was reversed by the combination of MSC-EXO and tempol treatment after combined treatment. In addition, the expression levels of HIF-1α, VEGF, p-PI3K, and p-AKT were increased after combined treatment.

CONCLUSIONS

Combined treatment could improve lung tissue injury, promote pulmonary vascular remodeling, restore lung function, and inhibit oxidative stress in BPD rats. These effects were achieved through activation of HIF-1α.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for the Treatment of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic respiratory disease in premature infants. However, there is a lack of effective treatment. Mesenchymal stromal cells derived extracellular vesicles (MSC-EVs), as nano- and micron-sized heterogeneous vesicles secreted by MSCs, are the main medium for information exchange between MSCs and injured tissue and organ, playing an important role in repairing tissue and organ injury. EVs include exosomes, microvesicles and so on. They are rich with various proteins, nucleic acids, and lipids. Now, EVs are considered as a new way of cell-to-cell communication. EVs mainly induce regeneration and therapeutic effects in different tissues and organs through the biomolecules they carry. The surface membrane protein or loaded protein and nucleic acid molecules carried by EVs, can activate the signal transduction of target cells and regulate the biological behavior of target cells after binding and cell internalization. MSC-EVs can promote the development of pulmonary vessels and alveoli and reduce pulmonary hypertension (PH) and inflammation and play an important role in the repair of lung injury in BPD. The regeneration potential of MSC-EVs is mainly due to the regulation of cell proliferation, survival, migration, differentiation, angiogenesis, immunoregulation, anti-inflammatory, mitochondrial activity and oxidative stress. As a new type of cell-free therapy, MSC-EVs have non-immunogenic, and are small in size and go deep into most tissues. What's more, it has good biological stability and can be modified and loaded with drugs of interest. Obviously, MSC-EVs have a good application prospect in the treatment of lung injury and BPD. However, there are still many challenges to make MSC-EVs really enter clinical application.

Umbilical Cord Blood-Derived Exosomes From Very Preterm Infants With Bronchopulmonary Dysplasia Impaired Endothelial Angiogenesis: Roles of Exosomal MicroRNAs

Premature infants have a high risk of bronchopulmonary dysplasia (BPD), which is characterized by abnormal development of alveoli and pulmonary vessels. Exosomes and exosomal miRNAs (EXO-miRNAs) from bronchoalveolar lavage fluid are involved in the development of BPD and might serve as predictive biomarkers for BPD. However, the roles of exosomes and EXO-miRNAs from umbilical cord blood of BPD infants in regulating angiogenesis are yet to be elucidated. In this study, we showed that umbilical cord blood-derived exosomes from BPD infants impaired angiogenesis in vitro. Next-generation sequencing of EXO-miRNAs from preterm infants without (NBPD group) or with BPD (BPD group) uncovered a total of 418 differentially expressed (DE) EXO-miRNAs. These DE EXO-miRNAs were primarily enriched in cellular function-associated pathways including the PI3K/Akt and angiogenesis-related signaling pathways. Among those EXO-miRNAs which are associated with PI3K/Akt and angiogenesis-related signaling pathways, BPD reduced the expression of hsa-miR-103a-3p and hsa-miR-185-5p exhibiting the most significant reduction (14.3% and 23.1% of NBPD group, respectively); BPD increased hsa-miR-200a-3p expression by 2.64 folds of the NBPD group. Furthermore, overexpression of hsa-miR-103a-3p and hsa-miR-185-5p in normal human umbilical vein endothelial cells (HUVECs) significantly enhanced endothelial cell proliferation, tube formation, and cell migration, whereas overexpressing hsa-miR-200a-3p inhibited these cellular responses. This study demonstrates that exosomes derived from umbilical cord blood of BPD infants impair angiogenesis, possibly via DE EXO-miRNAs, which might contribute to the development of BPD.

Immunosuppressive Effects of Mesenchymal Stem Cells-derived Exosomes

Mesenchymal stem cells (MSCs) have become important seed cells in therapy because of their immunosuppressive function and anti-inflammatory effects. MSCs exert immunosuppressive effects through direct contact or paracrine action. The paracrine functions of MSCs are at least partially mediated by exosomes, which are membrane vesicles, carrying abundant proteins, nucleic acids and other active molecules. MSC-exos have heterogeneity. The exosomes from different donors, tissues generations of MSCs carry different bioactive molecules. These cargos are transferred to recipient cells by endocytosis or binding to proteins on the receptor surface to mediate intercellular communication between different cell types and affect the functions of the recipient cells. Exosomes play an important role in the regulation of the immune system. Exosomes derived from MSCs (MSC-exos) carry immunomodulatory effectors or transmit active signal molecules to regulate the biological activities of immune cells and thus mediating immune suppression, especially on macrophages and T cells. Mitochondria and autophagy-related pathways are also associated with MSC-exos immunosuppressive effects. Graphical Abstract.

M2 macrophage-derived exosomes promote the c-KIT phenotype of vascular smooth muscle cells during vascular tissue repair after intravascular stent implantation

Rationale: For intravascular stent implantation to be successful, the processes of vascular tissue repair and therapy are considered to be critical. However, the mechanisms underlying the eventual fate of vascular smooth muscle cells (VSMCs) during vascular tissue repair remains elusive. In this study, we hypothesized that M2 macrophage-derived exosomes to mediate cell-to-cell crosstalk and induce dedifferentiation phenotypes in VSMCs. Methods: In vivo, 316L bare metal stents (BMS) were implanted from the left iliac artery into the abdominal aorta of 12-week-old male Sprague-Dawley (SD) rats for 7 and 28 days. Hematoxylin and eosin (HE) were used to stain the neointimal lesions. En-face immunofluorescence staining of smooth muscle 22 alpha (SM22α) and CD68 showed the rat aorta smooth muscle cells (RASMCs) and macrophages. Immunohistochemical staining of total galactose-specific lectin 3 (MAC-2) and total chitinase 3-like 3 (YM-1) showed the total macrophages and M2 macrophages. In vitro, exosomes derived from IL-4+IL-13-treated macrophages (M2Es) were isolated by ultracentrifugation and characterized based on their specific morphology. Ki-67 staining was conducted to assess the effects of the M2Es on the proliferation of RASMCs. An atomic force microscope (AFM) was used to detect the stiffness of the VSMCs. GW4869 was used to inhibit exosome release. RNA-seq was performed to determine the mRNA profiles of the RASMCs and M2Es-treated RASMCs. Quantitative real-time PCR (qRT-PCR) analysis was conducted to detect the expression levels of the mRNAs. Western blotting was used to detect the candidate protein expression levels. T-5224 was used to inhibit the DNA binding activity of AP-1 in RASMCs. Results: M2Es promote c-KIT expression and softening of nearby VSMCs, hence accelerating the vascular tissue repair process. VSMCs co-cultured in vitro with M2 macrophages presented an increased capacity for de-differentiation and softening, which was exosome dependent. In addition, the isolated M2Es helped to promote VSMC dedifferentiation and softening. Furthermore, the M2Es enhanced vascular tissue repair potency by upregulation of VSMCs c-KIT expression via activation of the c-Jun/activator protein 1 (AP-1) signaling pathway. Conclusions: The findings of this study emphasize the prominent role of M2Es during VSMC dedifferentiation and vascular tissue repair via activation of the c-Jun/AP-1 signaling pathway, which has a profound impact on the therapeutic strategies of coronary stenting techniques.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Bronchopulmonary Dysplasia: An Update on Experimental Therapeutics

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease that affects thousands of newborns and infants every year. Although it is accepted that BPD results from lung damage and inflammation triggered by mechanical ventilation and hyperoxia, the causes and molecular events leading to lung damage and arrested development remain unknown. While recent advances in neonatal care have improved the survival of very low-weight infants, the rates of BPD have not improved accordingly. This is mainly due to our limited understanding of the disease’s pathogenesis and the effective therapeutic options available. Current therapeutics for BPD involve ventilation management, steroid treatment, and administration of various agents, such as pulmonary surfactant, caffeine, vitamin A, nitric oxide, and stem cells. However, the efficacy of these agents in preventing and ameliorating BPD symptoms varies depending on the populations studied and the disease stage. As the field moves towards personalised therapeutic approaches, this review summarises clinical and experimental studies conducted in various models, aiming to increase understanding of the cellular and molecular mechanisms by which these agents can prevent or treat BPD. Due to the increasing number of extremely premature infants, it is imperative that we continue to work towards understanding the mechanisms of BPD pathogenesis and generating more effective therapeutic options.

Intraperitoneal injection of MSC-derived exosomes prevent experimental bronchopulmonary dysplasia

Mesenchymal stromal cell (MSC) derived exosomes mediate tissue protection and regeneration in many injuries and diseases by modulating cell protein production, protecting from apoptosis, inhibiting inflammation, and increasing angiogenesis. In the present study, daily intraperitoneal injection of MSC-derived exosomes protected alveolarization and angiogenesis in a newborn rat model of bronchopulmonary dysplasia (BPD) induced by 14 days of neonatal hyperoxia exposure (85% O₂). Exosome treatment during hyperoxia prevented disruption of alveolar growth, increased small blood vessel number, and inhibited right heart hypertrophy at P14, P21, and P56. In vitro, exosomes significantly increased tube-like network formation by HUVEC, in part through a VEGF mediated mechanism. In summary, daily intraperitoneal injection of exosomes increased blood vessel number and size in the lung through pro-angiogenic mechanisms. MSC-derived exosomes therefore have both anti-inflammatory and pro-angiogenic mechanism to protect the lung from hyperoxia induced lung and heart disease associated with BPD.

Early gestational mesenchymal stem cell secretome attenuates experimental bronchopulmonary dysplasia in part via exosome-associated factor TSG-6

BACKGROUND

Mesenchymal stem cells (MSCs) are promising tools for the treatment of human lung disease and other pathologies relevant to newborn medicine. Recent studies have established MSC exosomes (EXO), as one of the main therapeutic vectors of MSCs in mouse models of multifactorial chronic lung disease of preterm infants, bronchopulmonary dysplasia (BPD). However, the mechanisms underlying MSC-EXO therapeutic action are not completely understood. Using a neonatal mouse model of human BPD, we evaluated the therapeutic efficiency of early gestational age (GA) human umbilical cord (hUC)-derived MSC EXO fraction and its exosomal factor, tumor necrosis factor alpha-stimulated gene-6 (TSG-6).

METHODS

Conditioned media (CM) and EXO fractions were isolated from 25 and 30 weeks GA hUC-MSC cultures grown in serum-free media (SFM) for 24 h. Newborn mice were exposed to hyperoxia (> 95% oxygen) and were given intraperitoneal injections of MSC-CM or MSC-CM EXO fractions at postnatal (PN) day 2 and PN4. They were then returned to room air until PN14 (in a mouse model of severe BPD). The treatment regime was followed with (rh)TSG-6, TSG-6-neutralizing antibody (NAb), TSG-6 (si)RNA-transfected MSC-CM EXO and their appropriate controls. Echocardiography was done at PN14 followed by harvesting of lung, heart and brain for assessment of pathology parameters.

RESULTS

Systemic administration of CM or EXO in the neonatal BPD mouse model resulted in robust improvement in lung, cardiac and brain pathology. Hyperoxia-exposed BPD mice exhibited pulmonary inflammation accompanied by alveolar-capillary leakage, increased chord length, and alveolar simplification, which was ameliorated by MSC CM/EXO treatment. Pulmonary hypertension and right ventricular hypertrophy was also corrected. Cell death in brain was decreased and the hypomyelination reversed. Importantly, we detected TSG-6, an immunomodulatory glycoprotein, in EXO. Administration of TSG-6 attenuated BPD and its associated pathologies, in lung, heart and brain. Knockdown of TSG-6 by NAb or by siRNA in EXO abrogated the therapeutic effects of EXO, suggesting TSG-6 as an important therapeutic molecule.

CONCLUSIONS

Preterm hUC-derived MSC-CM EXO alleviates hyperoxia-induced BPD and its associated pathologies, in part, via exosomal factor TSG-6. The work indicates early systemic intervention with TSG-6 as a robust option for cell-free therapy, particularly for treating BPD.

Stem Cell-Derived Exosome in Cardiovascular Diseases: Macro Roles of Micro Particles

The stem cell-based therapy has emerged as the promising therapeutic strategies for cardiovascular diseases (CVDs). Recently, increasing evidence suggest stem cell-derived active exosomes are important communicators among cells in the heart via delivering specific substances to the adjacent/distant target cells. These exosomes and their contents such as certain proteins, miRNAs and lncRNAs exhibit huge beneficial effects on preventing heart damage and promoting cardiac repair. More importantly, stem cell-derived exosomes are more effective and safer than stem cell transplantation. Therefore, administration of stem cell-derived exosomes will expectantly be an alternative stem cell-based therapy for the treatment of CVDs. Furthermore, modification of stem cell-derived exosomes or artificial synthesis of exosomes will be the new therapeutic tools for CVDs in the future. In addition, stem cell-derived exosomes also have been implicated in the diagnosis and prognosis of CVDs. In this review, we summarize the current advances of stem cell-derived exosome-based treatment and prognosis for CVDs, including their potential benefits, underlying mechanisms and limitations, which will provide novel insights of exosomes as a new tool in clinical therapeutic translation in the future.