Cross talk between LAM cells and fibroblasts may influence alveolar epithelial cell behavior in lymphangioleiomyomatosis

Abstract

Lymphangioleiomyomatosis (LAM) is a female specific cystic lung disease in which TSC2 deficient LAM cells, LAM-Associated Fibroblasts (LAFs) and other cell types infiltrate the lungs. LAM lesions can be associated with type II alveolar epithelial cells (AT2 cells). We hypothesised that the behaviour of AT2 cells in LAM is influenced locally by LAFs. We tested this hypothesis in patient samples and in vitro. In human LAM lung, nodular AT2 cells show enhanced proliferation when compared to parenchymal AT2 cells, demonstrated by increased Ki67 expression. Further, nodular AT2 cells express proteins associated with epithelial activation in other disease states including Matrix Metalloproteinase 7, and Fibroblast Growth Factor 7 (FGF7). In vitro, LAF conditioned medium is mitogenic and positively chemotactic for epithelial cells, increases the rate of epithelial repair and protects against apoptosis. In vitro, LAM patient-derived TSC2 null cells cocultured with LAFs upregulate LAF expression of the epithelial chemokine and mitogen FGF7, which is a potential mediator of fibroblast-epithelial crosstalk, in an mTOR dependent manner. In a novel in vitro model of LAM, ex vivo cultured LAM lung-derived microtissues promote both epithelial migration and adhesion. Our findings suggest that AT2 cells in LAM display a proliferative, activated phenotype and that fibroblast accumulation following LAM cell infiltration into the parenchyma contributes to this change in AT2 cell behaviour. Fibroblast-derived FGF7 may contribute to the cross-talk between LAFs and hyperplastic epithelium in vivo, but does not appear to be the main driver of the effects of LAFs on epithelial cells in vitro.

LAM Cells as Potential Drivers of Senescence in Lymphangioleiomyomatosis Microenvironment

“…The LAM/TSC cell CM also caused senescent features in IMR90 cell line sustaining the capability of LAM/TSC cells to induce senescence in fibroblasts. Very recently, the capability of LAM cells to modulate the LAM-Associated fibroblasts (LAFs) phenotype was demonstrated in an in vitro model of LAM microtissues, where non-expressing-tuberin LAM cells cause the increased expression of the Fibroblasts Growth Factor 7 protein, which acts as a chemotactic and mitogen factor for epithelial cells [18]. This evidence sustains the role of the LAM microenvironment in controlling LAM development.…”

“…On these bases, senescence, and in particular the SASP, might have a role in driving disease progression. Indeed, even if it is demonstrated that LAM cells enhance the capability of lung fibroblasts to promote lung epithelial cell migration and proliferation [18], the mechanisms underlying the pathological communication are still not completely understood.…”

Single-cell multiomic analysis identifies a HOX-PBX gene network regulating the survival of lymphangioleiomyomatosis cells

“…We also recognize that the cells used for functional studies were not LAM-lung derived because of the rarity and survival disadvantage of LAM lung cells in culture conditions despite efforts from multiple groups to establish LAM cell lines. A recent study by Johnson Lab revealed that LAM lung stromal components including LAM-associated fibroblasts (LAFs) contribute to LAM progression in vitro and in vivo ( 44 ). LAFs secrete cytokines that promote the growth of LAM lung cells in culture and in three-dimensional microtissues ( 44 ).…”

“…A recent study by Johnson Lab revealed that LAM lung stromal components including LAM-associated fibroblasts (LAFs) contribute to LAM progression in vitro and in vivo ( 44 ). LAFs secrete cytokines that promote the growth of LAM lung cells in culture and in three-dimensional microtissues ( 44 ). In our in vitro and in vivo studies, we used immortalized LAM patient–derived cells to demonstrate the prosurvival roles of HOXD11-PBX1 predicted by integrative single-cell genomic analyses of LAM lung cells.…”

Plasmacytoid dendritic cells mediate CpG-ODN induced increase in survival in a mouse model of lymphangioleiomyomatosis

“…Nanoparticle drug delivery techniques can also be employed to target even smaller doses of CpG to specific cell types, which could reduce tissue-wide inflammation while enhancing therapeutic immune responses to inhibit LAM nodule proliferation. Because LAM nodules are composed of many cell types including fibroblasts that may contribute to LAM pathology (36)(37)(38), targeting treatment to immune cells could minimize stromal cell exposure to CpG stimulation and curb fibrosis and collagen deposition (tissue remodeling) (39).…”