Strong paracrine effects of SASP from senescence-induced severe early-onset COPD-derived fibroblasts

Background Lung fibroblasts from Severe Early-Onset (SEO-)COPD patients exhibit increased cellular senescence with higher levels of senescence-associated secretory phenotype (SASP) protein secretion. Yet, the impact of senescent fibroblasts, and their SASP, on surrounding fibroblasts in SEO-COPD lungs remains unclear. Aim To identify the effect of the SASP secreted by senescent SEO-COPD-derived fibroblasts on surrounding lung fibroblasts. Methods Cellular senescence was induced in lung fibroblasts derived from seven SEO-COPD patients (age≤53 years, FEV1<40% predicted), and conditioned medium (CM) containing the SASP, was collected (senescent CM). CM from untreated fibroblasts was used as control. Fibroblasts were stimulated with senescent and control CM, and with tissue plasminogen activator (t-PA), a previously identified COPD-associated SASP protein. Effects on paracrine senescence, inflammation, and extracellular matrix (ECM) regulation were assessed. Results Stimulation with senescent CM increased the percentage of Senescence-associated beta-galactosidase positive fibroblasts and decreased p16, p21 & LMNB1 expression (p<0.05). T-PA did not affect these markers. Senescent CM increased IL-8 gene expression, increased IL-6 secretion, and strongly increased IL-8 secretion compared to control CM. T-PA slightly decreased IL-6 and IL-8 secretion. Additionally, senescent CM and t-PA stimulation both reduced decorin secretion. Senescent CM reduced FN1 gene expression, while DCN and MMP2 expression remained unaffected. T-PA did not affect ECM gene expression. Conclusion The SASP from senescence-induced SEO-COPD-derived fibroblasts has a strong paracrine effect on untreated fibroblasts, suggesting that senescent lung fibroblasts contribute to chronic inflammation and ECM dysregulation. These findings imply involvement of senescent fibroblasts in abnormal lung ageing and possibly disease pathology in COPD.