120 Chapter 5 presence of bronchiolization of the alveolar epithelium was observed in all IPF patients from whom cells were obtained (Supplementary Figure 3). This is relevant as this is indicative of an active bronchiolization process occurring in the alveolar region in the IPF tissues, which is a form of metaplasia, and the larger organoid formation, potentially due to aberrant proliferation or cell transitioning in the IPF organoids, may be a reflection of such metaplasia [14, 15]. Further studies on whether the IPF organoids contain more or larger cells, or more swelling due to reduced barrier function or more mucus production would be required to investigate the influence of bronchiolization in parenchymal lung tissue on the organoid forming process. Our study reporting initial observations on alveolar regeneration in IPF has some limitations that should be recognized. The lack of differences in the numbers of different cell types in the unfractionated cell populations between the groups may be a consequence of the isolation method, which has been optimized for alveolar epithelial cells and not for other cell types. In addition, the generated cell counts may be an underestimation of the total numbers of cells present in the lung tissue as several of the surface markers are known to be sensitive to cleavage by the enzymatic treatment used to isolate cells. Nevertheless, sufficient cell numbers have been isolated in order to support organoid formation effectively, as indicated by our current findings. Further investigation of the involvement of cellular interactions during the initiation of organoid formation will be of interest in future studies, but was outside of the scope of this discovery study. As mentioned above, the origin of larger organoids from IPF donors requires further investigation. The finding that the organoid forming efficiency differs between IPF and non-IPF lung-derived organoid cultures from unfractionated suspensions, but not isolated epithelial progenitors, suggests that altered interactions between different cell types derived from IPF lungs are responsible for the aberrations in the initiation phase of the organoid formation. Previous research has shown that WNT-signalling influences the ability of epithelial progenitor cells to self-renew and form organoids [16]. In mice it has been shown that epithelial progenitors reside in a stromal niche that provides WNT signals to maintain their stemness [17]. Thus, we speculate that the WNT signalling pathway might be dysregulated in IPF-derived organoids due to the disturbed crosstalk between epithelial progenitors and stromal cell types. Further studies are needed to investigate whether alterations in the release of WNT ligands from stromal cells, endothelial cells and/or macrophages or in their interaction with epithelial cells occur in IPF.
RkJQdWJsaXNoZXIy MTk4NDMw