Idiopathic pulmonary fibrosis (IPF) is characterized by chronic inflammation, severe scarring, and stem cell senescence. Stem cell‐based therapies modulate inflammatory and fibrogenic pathways by release of soluble factors. Stem cell‐derived extracellular vesicles should be explored as a potential therapy for IPF. Human amnion epithelial cell‐derived exosomes (hAEC Exo) were isolated and compared against human lung fibroblasts exosomes. hAEC Exo were assessed as a potential therapy for lung fibrosis. Exosomes were isolated and evaluated for their protein and miRNA cargo. Direct effects of hAEC Exo on immune cell function, including macrophage polarization, phagocytosis, neutrophil myeloperoxidase activity and T cell proliferation and uptake, were measured. Their impact on immune response, histological outcomes, and bronchioalveolar stem cell (BASC) response was assessed in vivo following bleomycin challenge in young and aged mice. hAEC Exo carry protein cargo enriched for MAPK signaling pathways, apoptotic and developmental biology pathways and miRNA enriched for PI3K‐Akt, Ras, Hippo, TGFβ, and focal adhesion pathways. hAEC Exo polarized and increased macrophage phagocytosis, reduced neutrophil myeloperoxidases, and suppressed T cell proliferation directly. Intranasal instillation of 10 μg hAEC Exo 1 day following bleomycin challenge reduced lung inflammation, while treatment at day 7 improved tissue‐to‐airspace ratio and reduced fibrosis. Administration of hAEC Exo coincided with the proliferation of BASC. These effects were reproducible in bleomycin‐challenged aged mice. The paracrine effects of hAECs can be largely attributed to their exosomes and exploitation of hAEC Exo as a therapy for IPF should be explored further. Stem Cells Translational Medicine 2018;7:180–196

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that mainly affects premature babies who require ventilator support. The pathogenesis of BPD is complex but includes vascular maldevelopment, alveolarization arrest, and lung inflammation. There is no cure for BPD. Clinical care is limited to supportive respiratory measures. A population of stem‐like cells derived from placental membranes, human amnion epithelial cells (hAECs), has shown therapeutic promise in preclinical models of BPD. With a view to future efficacy trials, we undertook a first‐in‐human clinical trial of hAECs in babies with BPD to assess the safety of these cells. In a single‐center, open‐label phase I trial, we administered allogeneic hAECs (1 × 106 per kilogram bodyweight) by intravenous infusion to six premature babies with BPD. The primary outcomes of the study were focused on safety, including local site reaction, anaphylaxis, infection, features of rejection, or tumor formation. Outcomes to discharge from neonatal unit were studied. The hAECs were well tolerated. In the first baby, there was transient cardiorespiratory compromise during cell administration consistent with a pulmonary embolic event. Following changes to cell administration methods, including introduction of an inline filter, and reducing the cell concentration and the rate of cell infusion, no such events were observed in the subsequent five babies. We did not see evidence of any other adverse events related to cell administration. Allogeneic hAECs can be safely infused into babies with established BPD. Future randomized clinical trials to assess efficacy in this patient population are justified. Stem Cells Translational Medicine 2018;7:628–635

Human amnion epithelial cells (hAECs) have been shown to modulate inflammation and restore normal lung structure and respiratory function following bleomycin challenge in immune-competent mice. These effects are exerted despite a lack of significant engraftment of hAECs, suggesting that immunomodulatory effect mechanisms are at play. In this study, using the bleomycin model of injury, we explored the interactions between hAECs and macrophages. We administered 4 million hAECs intraperitoneally to C57Bl6 mice 24 h following a bleomycin challenge. Using FACS analysis and qPCR, we showed that hAEC administration significantly reduced macrophage infiltration into the lungs and that the majority of the pulmonary macrophages were of the M2 phenotype. Using bone marrow-derived macrophages, we then showed that hAEC-conditioned media could alter macrophage polarization, migration, and phagocytosis, without affecting macrophage survival or proliferation in vitro. This study provides the first evidence that hAECs directly influence macrophage behavior in a proreparative manner and suggests that hAECs are able to mediate these effects independently of other immune cell types.

IntroductionThe immunomodulatory properties of human amnion epithelial cells (hAECs) have been previously described in several disease models. We previously reported on the ability of hAECs to influence macrophage phenotype and chemotaxis. In this study, we aim to elucidate the contribution of regulatory T cells (Tregs) to macrophage polarisation and downstream effects on inflammation and fibrosis in a bleomycin model of lung injury.MethodsEither CD45+/FoxP3+Tregs or CD45+/FoxP3-non-Tregs were adoptively transferred into Rag1-/- mice immediately prior to bleomycin challenge. Four million hAECs were administered 24 hours later. Outcomes were measured 7 or 14 days later.ResultsMitigation of lung inflammation and fibrosis was observed only in animals that received both hAECs and Tregs. hAEC treatment also induced the maturation of non-Tregs into FoxP3-expressing Tregs. This event was found to be transforming growth factor-beta (TGFβ)-dependent. Furthermore, polarisation of macrophages from M1 to M2 occurred only in animals that received hAECs and Tregs.ConclusionsThis study provides the first evidence that Tregs are required for hAEC-mediated macrophage polarisation and consequential mitigation of bleomycin-induced lung injury. Uncovering the interactions between hAECs, macrophages, and T-cell subsets is central to understanding the mechanisms by which hAECs elicit lung repair.Electronic supplementary materialThe online version of this article (doi:10.1186/scrt542) contains supplementary material, which is available to authorized users.