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BackgroundPathways directing endogenous stem/progenitor cells to restore normal architecture and function of damaged/diseased lungs remain underexplored. Published data have revealed that alveolar progenitor type II cell (ATIIC)-derived signaling promotes re-epithelialization of injured alveoli, yet the underlying mechanism is unknown. Here we aim to define the role of ATIIC-derived exosome miRNA signaling in controlling ATIIC-specific proliferation or differentiation in response to injury.MethodsPluripotent stem cell-derived cultures, which contain early lung stem/progenitor populations that can subsequently differentiate into ATIICs, were used as a model for unbiased screening and identification of ATIIC phenotype-specific exosome miRNA signaling, and human induced pluripotent stem cell-derived ATIICs (hiPSC-ATIICs) were employed to examine the molecular basis of key exosome miRNA signaling in promoting ATIIC-specific proliferation. QRT-PCR was performed to examine expression pattern of ATIIC-derived key exosome miRNA in an alveolar injury model and in injured human lungs.ResultsWe show that human ATIIC line (A549)-derived exosome miR-371b-5p promotes ATIIC-specific proliferation, but not differentiation, in differentiating cultures of pluripotent stem cells. Using 3′UTR-driven luciferase reporters, we identified PTEN as a direct target of miR-371b-5p. Transfection of miR-371b-5p mimic into hiPSC-ATIICs leads to significantly decreased expression of endogenous PTEN, which stimulates phosphorylation of Akt and its downstream substrates, GSK3β and FOXOs, promoting cell proliferation. While not expressed in normal ATIIC phenotypes, the exosome miR-371b-5p expression is significantly induced after hiPSC-ATIICs or hATIICs (human primary ATIICs) are subjected to bleomycin-induced injury. To rule out that the ATIIC-derived exosome-miRNAs are merely a cell culture phenomenon, we transplanted hiPSC-ATIICs into bleomycin-challenged lungs of mice, and found that the transplanted hiPSC-ATIICs engraft and express exosome miR-371b-5p, along with additional survival of numerous mouse ATIICs in bleomycin-injured lungs. Consistent with these findings, significant levels of exosome miR-371b-5p were also detected in lavage samples of patients with acute pneumonia, but not in those from patients without pulmonary disorders.ConclusionsCollectively, our data strongly suggest that ATIIC-derived exosome miR-371b-5p may serve as a niche signaling to augment ATIIC survival/proliferation, promoting re-epithelialization of injured alveoli, and thus provide a promising novel target to develop treatment for currently incurable lung diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-017-0586-2) contains supplementary material, which is available to authorized users.

Human induced pluripotent stem cells (hiPSCs) have great therapeutic potential in repairing defective lung alveoli. However, genetic abnormalities caused by vector-integrations and low efficiency in generating hiPSCs, as well as difficulty in obtaining transplantable hiPSC-derived cell types, are still major obstacles. Here we report a novel strategy using a single non-viral site-specific-targeting vector with a combination of Tet-On inducible gene expression system, Cre/lox P switching gene expression system, and alveolar epithelial type II cell (ATIIC)-specific NeomycinR trangene expression system. With this strategy, a single copy of all of the required transgenes can be specifically knocked into a site immediately downstream of beta-2-microglobulin (B2M) gene locus at a high frequency, without causing B2M dysfunction. Thus, the expression of reprogramming factors, Oct4, Sox2, cMyc and Klf4, can be precisely regulated for efficient reprogramming of somatic cells into random-integration-free or genetic mutation-free hiPSCs. The exogenous reprogramming factor transgenes can be subsequently removed after reprogramming by transient expression of Cre recombinase, and the resulting random-integration-free and exogenous reprogramming-factor-free hiPSCs can be selectively differentiated into a homogenous population of ATIICs. In addition, we show that these hiPSC-derived ATIICs exhibit ultra-structural characteristics and biological functions of normal ATIICs. When transplanted into bleomycin-challenged mice lungs, hiPSC-derived ATIICs efficiently remain and re-epithelialize injured alveoli to restore pulmonary function, preventing lung fibrosis and increasing survival without tumorigenic side effect. This strategy allows for the first time efficient generation of patient-specific ATIICs for possible future clinical applications.

Objective:A Mediterranean diet supplemented with olive oil and nuts prevents cardiovascular disease in clinical studies, but the underlying mechanisms are incompletely understood. We investigated whether the preventive effect of the diet could be due to inhibition of atherosclerosis and foamy monocyte formation inLdlr–/–mice fed with a diet in which milkfat in a Western diet (WD) was replaced with extra-virgin olive oil and nuts (EVOND).Approach and Results:Ldlr–/–mice were fed EVOND or a Western diet for 3 (or 6) months. Compared with the Western diet, EVOND decreased triglyceride and cholesterol levels but increased unsaturated fatty acid concentrations in plasma. EVOND also lowered intracellular lipid accumulation in circulating monocytes, indicating less formation of foamy monocytes, compared with the Western diet. In addition, compared with the Western diet, EVOND reduced monocyte expression of inflammatory cytokines, CD36, and CD11c, with decreased monocyte uptake of oxLDL (oxidized LDL [low-density lipoprotein]) ex vivo and reduced CD11c+foamy monocyte firm arrest on vascular cell adhesion molecule-1 and E-selectin–coated slides in an ex vivo shear flow assay. Along with these changes, EVOND compared with the Western diet reduced the number of CD11c+macrophages in atherosclerotic lesions and lowered atherosclerotic lesion area of the whole aorta and aortic sinus.Conclusions:A diet enriched in extra-virgin olive oil and nuts, compared with a Western diet high in saturated fat, lowered plasma cholesterol and triglyceride levels, inhibited foamy monocyte formation, inflammation, and adhesion, and reduced atherosclerosis inLdlr–/–mice.