Effects of Mesenchymal Stem Cell Coculture on Human Lung Small Airway Epithelial Cells

Abstract

Mesenchymal stem cells (MSCs) and their secreted extracellular vesicles have been used effectively in different lung disease animal models and clinical trials. Their specific beneficial effects, the potential differences between MSCs derived from different organs, and interactions between MSC products and target cells still need to be studied further. Therefore, we investigated the effects of secreted products of human MSCs derived from the bone marrow and adipose tissue on human lung small airway epithelial (AE) cells in vitro. AE cells were cocultured with MSCs in inserts that allowed the free exchange of medium but did not allow direct cell-to-cell contact. We examined the effects on AE cell viability, proliferation, cell numbers, expression of AE cell-specific genes, and CD54 (intercellular adhesion molecule 1 (ICAM1)) surface positivity, as well as the secretion/uptake of growth factors relevant for AE cell. We found that coculture increased the viability of AE cells. The majority of AE cells expressed CD54 on their surface, but the percentage of cells being positive for CD54 did not increase in coculture. However, ICAM1 gene expression was increased in coculture. Also, we observed increased gene expression of mucin (MUC1), a lung-enriched cell surface glycoprotein. These observed effects were the same between bone marrow and adipose tissue MSCs. However, MSCs derived from adipose tissue reduced angiopoietin concentrations in coculture, whereas those from the bone marrow did not. Conclusively, MSCs influenced AE cells positively by increasing their viability and affecting gene expression, with some effects being specific for the tissue origin of MSCs.

Figure 1

Small airway epithelial cells in culture. Small airway epithelial cells are well-attached one day after plating (a) and had formed a near confluent monolayer after four days of culture (b). Phase microscopy, scale bars 200 μm.

Figure 2

Flow cytometry of small airway epithelial cells. Representative analyses of small airway epithelial (AE) cells investigated in flow cytometry. AE cells were either cultured alone without any addition of mesenchymal cells (MSC), which are the control cultures, left, or cocultured with MSCs derived from either adipose tissue (AD), middle, or bone marrow (BM), right. (a) Determination of cell viability using the eFluor 780 viability dye, which stains exclusively dead cell positive (yellow) compared to unstained controls (blue). (b) Detection of CD54-positive cells (blue), with isotype controls (red). (c) Detection of proliferating Ki67-positive cells (blue), with isotype controls (red).