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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 TH2 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., Human mesenchymal stem cells (MSCs) either directly promote group 2 innate lymphoid cell (ILC2) activation through upregulated ICOS‐ICOSL interaction. MSCs exert inhibitory effects on ILC2s via activating regulatory T (Treg) cells through ICOS‐ICOSL interaction. Treg cells prevent the promotion of MSCs on ILC2s via decreased ICOS‐ICOSL interaction between MSCs and ILC2s. IL‐10 is required for the MSC‐induced Treg cells in suppressing ILC2s alongside ICOS‐ICOSL interaction.

BackgroundAllergic rhinitis (AR) is characterized by IgE-mediated mucosa response after exposure to allergens. Extracellular vesicles (EVs) are nano-size vesicles containing biological cargos for intercellular communications. However, the role of plasma EVs in pathogenesis of AR remains largely unknown.MethodsPlasma EVs from patients with AR were isolated, quantified, and characterized. The expression of Der p 1 and antigen-presenting molecules on EVs was determined by Western blot, flow cytometry, or ELISA. PKH26- and CFSE (carboxyfluorescein succinimidyl ester)-stained AR-EVs were used to determine the uptake of EVs by CD4+T cells and their effects on CD4+T cell proliferation, respectively.ResultsPlasma EVs in healthy control (HC) and AR patients were similar in the concentration of particles, expression for specific EV markers, and both had structural lipid bilayer. However, the levels of Der p 1 on plasma EVs from both mild and moderate-severe AR patients were significantly higher than that on HC. The levels of antigen-presenting molecules on plasma EVs were similar from three subjects. Moreover, levels of Der p 1 on EVs in plasma, but not nasal secretion, were significantly associated with the symptom score of AR patients and level of plasma IL-13. Additionally, plasma EVs from patients with AR promoted the development of Th2 cells, while no effect was found on CD4+ T-cell proliferation.ConclusionsPlasma EVs derived from patients with AR exhibited antigen-presenting characteristics and promoted differentiation of Th2 cells, thus providing novel understanding of the pathogenesis of AR.

The diversity of immune responses in allergic diseases is critically mediated by dendritic cells (DCs), including myeloid and plasmacytoid DCs. Allergen inhalation increased the release of IL-33 from patients with allergic rhinitis (AR), which affecting the downstream cells by binding to its receptor (ST2). However, the effects of inhaled allergens on the expression of ST2 by DCs and IL-33 on the function of mDCs are unknown. The levels of ST2+mDCs and ST2+pDCs in the blood from patients with AR and healthy subjects were examined using flow cytometry. Moreover, the patients were challenged using the allergens and the levels of ST2+mDCs and ST2+pDCs were investigated at different time points. We found that there were higher levels of ST2+ mDCs and ST2+ pDCs in patients with AR, and these levels were further increased 0.5 h after allergen inhalation. Additionally, the type 2 immune response was upregulated after challenge. IL-33 treatment increased the expression of ST2 on mDCs. Our study demonstrated that ST2 was upregulated on DCs after allergen inhalation and that mDCs responded directly to IL-33 through ST2, suggesting that the IL-33/ST2 axis might play an important role in the pathogenesis of allergic rhinitis by DCs.

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.

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.

Subarachnoid hemorrhage (SAH) is a devastating disease with high mortality. The mechanisms underlying its pathological complications have not been fully identified. Here, we investigate the potential involvement of the glymphatic system in the neuropathology of SAH. We demonstrate that blood components rapidly enter the paravascular space following SAH and penetrate into the perivascular parenchyma throughout the brain, causing disastrous events such as cerebral vasospasm, delayed cerebral ischemia, microcirculation dysfunction and widespread perivascular neuroinflammation. Clearance of the paravascular pathway with tissue-type plasminogen activator ameliorates the behavioral deficits and alleviates histological injury of SAH. Interestingly, AQP4−/− mice showed no improvements in neurological deficits and neuroinflammation at day 7 after SAH compared with WT control mice. In conclusion, our study proves that the paravascular pathway dynamically mediates the pathological complications following acute SAH independently of glymphatic control.