Ji Yoon Lee, Seok-Ho Hong. IJSC 2020;13:1-12. https://doi.org/10.15283/ijsc19127

Detailed understanding of the pathogenesis and development of effective therapies for pulmonary fibrosis (PF) have been hampered by lack of in vitro human models that recapitulate disease pathophysiology. In this study, we generated alveolar organoids (AOs) derived from human pluripotent stem cells (hPSCs) for use as an PF model and for drug efficacy evaluation. Stepwise direct differentiation of hPSCs into alveolar epithelial cells by mimicking developmental cues in a temporally controlled manner was used to generate multicellular AOs. Derived AOs contained the expected spectrum of differentiated cells, including alveolar progenitors, type 1 and 2 alveolar epithelial cells and mesenchymal cells. Treatment with transforming growth factor (TGF-β1) induced fibrotic changes in AOs, offering a PF model for therapeutic evaluation of a structurally truncated form (NP-011) of milk fat globule-EGF factor 8 (MFG-E8) protein. The significant fibrogenic responses and collagen accumulation that were induced by treatment with TGF-β1 in these AOs were effectively ameliorated by treatment with NP-011 via suppression of extracellular signal-regulated kinase (ERK) signaling. Furthermore, administration of NP-011 reversed bleomycin-induced lung fibrosis in mice also via ERK signaling suppression and collagen reduction. This anti-fibrotic effect mirrored that following Pirfenidone and Nintedanib administration. Furthermore, NP-011 interacted with macrophages, which accelerated the collagen uptake for eliminating accumulated collagen in fibrotic lung tissues. This study provides a robust in vitro human organoid system for modeling PF and assessing anti-fibrotic mechanisms of potential drugs and suggests that modified MGF-E8 protein has therapeutic potential for treating PF.

Cadmium (Cd), a major component of cigarette smoke, disrupts the normal functions of airway cells and can lead to the development of various pulmonary diseases such as chronic obstructive pulmonary disease (COPD). However, the molecular mechanisms involved in Cd-induced pulmonary diseases are poorly understood. Here, we identified a cluster of genes that are altered in response to Cd exposure in human bronchial epithelial cells (BEAS-2B) and demonstrated that Cd-induced ER stress and inflammation are mediated via CCAAT-enhancer-binding proteins (C/EBP)-DNA-damaged-inducible transcript 3 (DDIT3) signaling in BEAS-2B cells. Cd treatment led to marked upregulation and downregulation of genes associated with the cell cycle, apoptosis, oxidative stress and inflammation as well as various signal transduction pathways. Gene set enrichment analysis revealed that Cd treatment stimulated the C/EBP signaling pathway and induced transcriptional activation of its downstream target genes, including DDIT3. Suppression of DDIT3 expression using specific small interfering RNA effectively alleviated Cd-induced ER stress and inflammatory responses in both BEAS-2B and normal primary normal human bronchial epithelial cells. Taken together, these data suggest that C/EBP signaling may have a pivotal role in the early induction of ER stress and inflammatory responses by Cd exposure and could be a molecular target for Cd-induced pulmonary disease.

Growing evidence links prenatal exposure to particulate matter (PM2.5) with reduced lung function and incidence of pulmonary diseases in infancy and childhood. However, the underlying biological mechanisms of how prenatal PM2.5 exposure affects the lungs are incompletely understood, which explains the lack of an ideal in vitro lung development model. Human pluripotent stem cells (hPSCs) have been successfully employed for in vitro developmental toxicity evaluations due to their unique ability to differentiate into any type of cell in the body. In this study, we investigated the developmental toxicity of diesel fine PM (dPM2.5) exposure during hPSC-derived alveolar epithelial cell (AEC) differentiation and three-dimensional (3D) multicellular alveolar organoid (AO) development. We found that dPM2.5 (50 and 100 μg/mL) treatment disturbed the AEC differentiation, accompanied by upregulation of nicotinamide adenine dinucleotide phosphate oxidases and inflammation. Exposure to dPM2.5 also promoted epithelial-to-mesenchymal transition during AEC and AO development via activation of extracellular signal-regulated kinase signaling, while dPM2.5 had no effect on surfactant protein C expression in hPSC-derived AECs. Notably, we provided evidence, for the first time, that angiotensin-converting enzyme 2, a receptor to mediate the severe acute respiratory syndrome coronavirus clade 2 (SARS-CoV-2) entry into target cells, and the cofactor transmembrane protease serine 2 were significantly upregulated in both hPSC-AECs and AOs treated with dPM2.5. In conclusion, we demonstrated the potential alveolar development toxicity and the increase of SARS-Cov-2 susceptibility of PM2.5. Our findings suggest that an hPSC-based 2D and 3D alveolar induction system could be a useful in vitro platform for evaluating the adverse effects of environmental toxins and for virus research.

Ji-Young Kim, Ji-Hye Jung, Seung-Joon Lee, Seon-Sook Han, and Seok-Ho Hong. Mol. Cells 2022;45:869-76. https://doi.org/10.14348/molcells.2022.0109

Hematopoietic stem cells (HSCs) can regenerate the entire hematopoietic system in vivo, providing the most relevant criteria to measure candidate HSCs derived from human embryonic stem cell (hESC) or induced pluripotent stem cell (hiPSC) sources. Here we show that, unlike primitive hematopoietic cells derived from hESCs, phenotypically identical cells derived from hiPSC are more permissive to graft the bone marrow of xenotransplantation recipients. Despite establishment of bone marrow graft, hiPSC-derived cells fail to demonstrate hematopoietic differentiation in vivo. However, once removed from recipient bone marrow, hiPSC-derived grafts were capable of in vitro multilineage hematopoietic differentiation, indicating that xenograft imparts a restriction to in vivo hematopoietic progression. This failure to regenerate multilineage hematopoiesis in vivo was attributed to the inability to downregulate key microRNAs involved in hematopoiesis. Based on these analyses, our study indicates that hiPSCs provide a beneficial source of pluripotent stem cell-derived hematopoietic cells for transplantation compared with hESCs. Since use of the human–mouse xenograft models prevents detection of putative hiPSC-derived HSCs, we suggest that new preclinical models should be explored to fully evaluate cells generated from hiPSC sources. Disclosure of potential conflicts of interest is found at the end of this article.