Induced pluripotent and CD34+ stem cell derived myeloid cells display differential responses to particle and dust mite exposure

Abstract

Myeloid cells form an essential component of initial responses to environmental hazards and toxic exposures. The ability to model these responses in vitro is central to efforts tasked with identifying hazardous materials and understanding mechanisms of injury and disease. Induced pluripotent stem cell (iPSC) derived cells have been suggested as alternatives to more established primary cell testing systems for these purposes. iPSC derived macrophage and dendritic like cells were compared to CD34+ haematopoietic stem cell derived populations using transcriptomic analysis. Using single cell sequencing-based characterisation of iPSC derived myeloid cells, we identified transitional, mature and M2 like macrophages as well as dendritic like antigen presenting cells and fibrocytes. Direct transcriptomic comparisons between iPSC and CD34+ cell derived populations revealed higher expression of myeloid differentiation genes such as MNDA, CSF1R and CSF2RB in CD34+ cells, while iPSC populations had higher fibroblastic and proliferative markers. Exposure of differentiated macrophage populations to nanoparticle alone or in combination with dust mite, resulted in differential gene expression on combination only, with responses markedly absent in iPSC compared to CD34+ derived cells. The lack of responsiveness in iPSC derived cells may be attributable to lower levels of dust mite component receptors CD14, TLR4, CLEC7A and CD36. In summary, iPSC derived myeloid cells display typical characteristics of immune cells but may lack a fully mature phenotype to adequately respond to environmental exposures.

Mononuclear phagocyte sub-types in vitro display diverse transcriptional responses to dust mite exposure

“…Building from this work in our current study, we have used Scseq to further characterise the different cell types within these in vitro systems and tested how some of them respond to HDM exposure. Again, building on previous work, where we demonstrated that CD34+ derived macrophages respond to particle and house dust mite exposures through an increase in inflammatory mediators including CXCL5, CCL15 and metallothionein MT1M expression 24 , our aim in this study was to identify the cell types responsible for these changes in gene expression. Ultimately, through the identification of MNP cell types, which are highly responsive to environmental stimuli, and present within diseased airways, one can help refine mechanistic understanding of how inhaled exposures contribute to exacerbation of disease conditions such as allergic asthma.…”

“…In this study, we used human primary bone marrow derived CD34+ stem cells to generate different populations of MNPs, found within inflammatory airway disease, with the aim to test responses to pollutant particulate and allergen exposure 23 , 24 . These stem cells give rise to many if not all of the infiltrating MNP cells in allergic and asthmatic lung disease and have also been observed to replace alveolar macrophages 25 as they are depleted from the lung in disease.…”