Comprehensive Analysis of Genes Expressed by Rare Microchimeric Fetal Cells in the Maternal Mouse Lung1

Abstract

During pregnancy, cells from each fetus travel into the maternal circulation and organs, resulting in the development of microchimerism. Identification of the cell types in this microchimeric population would permit better understanding of possible mechanisms by which they affect maternal health. However, comprehensive analysis of fetal cells has been hampered by their rarity. In this study, we sought to overcome this obstacle by combining flow cytometry with multidimensional gene expression microarray analysis of fetal cells isolated from the murine maternal lung during late pregnancy. Fetal cells were collected from the lungs of pregnant female mice. cDNA was amplified and hybridized to gene expression microarrays. The resulting fetal cell core transcriptome was interrogated using multiple methods including Ingenuity Pathway Analysis, the BioGPS gene expression database, principal component analysis, the Eurexpress gene expression atlas, and primary literature. Here we report that small numbers of fetal cells can be flow sorted from the maternal lung, facilitating discovery-driven gene expression analysis. We additionally show that gene expression data can provide functional information about fetal cells. Our results suggest that fetal cells in the murine maternal lung are a mixed population, consisting of trophoblasts, mesenchymal stem cells, and cells of the immune system. Detection of trophoblasts and immune cells in the maternal lung may facilitate future mechanistic studies related to the development of immune tolerance and pregnancy-related complications, such as pre-eclampsia. Furthermore, the presence and persistence of mesenchymal stem cells in maternal organs may have implications for long-term postpartum maternal health.

Tissue Optical Clearing, Three-Dimensional Imaging, and Computer Morphometry in Whole Mouse Lungs and Human Airways

“…Our method overcomes significant analysis hurdles and can automatically quantify a labeled structure (nerves in this case) in the context of its 3D tissue compartment. The approach can be readily used to study other sparse and heterogeneous structures, such as rare sites of microchimerism where fetal cells travel into the lung during pregnancy or the earliest micron-sized sites of tumor metastases (43,44). Whole lung microscopic imaging has the potential to fill the gap between large-scale (e.g., CT, MRI) and small-scale (e.g., fluorescence microscopy) imaging data to provide a comprehensive analysis of cellular/ subcellular structures throughout the lung.…”

Chimerism in health and potential implications on behavior: A systematic review

“…Studies of myocardial injury in pregnant mice have provided evidence of fetal cell migration to sites of cardiac injury and capacity for cardiac differentiation (Kara et al, 2012; Kara, Bolli, Matsunaga, et al, 2012). Fetal microchimerism in the lungs and brain of mice feature various cell types and have greater detection at the site of tissue injury from smoking or excitotoxic lesions, respectively, suggesting a potential protective effect (Pritchard, Wick, Slonim, Johnson, & Bianchi, 2012; Tan et al, 2005; Vogelgesang et al, 2014). It has been proposed that improving our understanding of chimeric cell trafficking across the placenta, blood–brain barrier and migration to sites of tissue injury in mice may provide insights into the properties that also support this behavior in humans (Tan et al, 2005).…”

Raising antibodies against circulating foetal cells from maternal peripheral blood

“…Lack of understanding concerning the origin of cells crossing the placenta into the maternal bloodstream is however a major problem, as an optimal cell type for non‐invasive prenatal diagnostics have not yet been identified. Increased knowledge of cellular trafficking across the placenta could furthermore provide novel insight in microchimeric foetal cells affecting maternal health …”

“…Increased knowledge of cellular trafficking across the placenta could furthermore provide novel insight in microchimeric foetal cells affecting maternal health. 11 Different approaches based on antibodies recognising biomarkers of specific cell populationshave been used for the enrichment, such as MACS 12 and FACS, 13 and identification of circulating foetal cells. Enrichment often is followed by characterisation of the origin of foetal cells by either fluorescence in situ hybridization (FISH) 12 or PCR.…”