LAM cell mTOR dysregulation induces IL6 and paracrine AT2 cell senescence impeding lung repair in lymphangioleiomyomatosis.

LAM is a rare disease which causes lung cysts and respiratory failure. TSC2 deficient 'LAM cells' with dysregulated mTOR signalling form nodules with fibroblasts causing lung injury. We examined if mTOR dysregulation could induce senescence and impair responses to lung injury. Senescence markers p21 and p16 were increased in LAM lungs and co-localised with alveolar type 2 cells. The SenMayo senescence gene panel was upregulated in LAM alveolar type 2 cells with senescence supressed by mTOR inhibition in patients. LAM cell / fibroblast spheroid cultures induced senescence markers in alveolar type 2 cell organoids, altered their growth and delayed epithelial scratch wound repair. Upstream regulator analysis predicted alveolar type 2 cell IL6 receptor activation. IL6 was produced by LAM cells, was overexpressed in LAM serum and related to lung function, induced p16 and p21 in alveolar type 2 cells and inhibited epithelial wound resolution. Wound repair in the presence of TSC2 null but not TSC2 addback LAM cell / fibroblast spheroids was enhanced by the IL6 receptor antagonist Tocilizumab. Our findings show TSC2 loss induces senescence and IL6 production which are associated with impaired lung repair. Targeting IL6 signalling in parallel with mTOR inhibition, may reduce lung damage in LAM. Overall design: To understand the processes driving senescence we used laser capture micro-dissection to isolate LAM nodules from lung tissue from 19 women with LAM and 3 controls. Lung tissue used for laser capture microdissection was obtained from patients at the UK LAM. RNA was extracted from laser capture and rest of lungs and analysed gene expression by RNA sequencing.