Abstract Rationale Silicosis is an occupational lung disease caused by the inhalation of respirable crystalline silica, characterized by chronic inflammation and massive fibrosis. Current in vivo and in vitro models present limitations in replicating the pathophysiological features of silicosis, hindering the development of effective therapies. Therefore, we aimed to establish a novel ex vivo model to investigate acute inflammatory responses in both mouse (mPCLS) and human (hPCLS) precision-cut lung slices exposed to different types of commercial silica. Methods PCLS from male C57BL/6 mice (n = 5) and human lung tissue (n = 5) were untreated (control) or treated with silica (Min-U-Sil 5, NIST 1878b or quarry-derived DQ12) at 200 or 400µg/mL, in the absence or presence of lipopolysaccharide (LPS; 10ng/mL) for 5 days. PCLS viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide; MTT) and silica-induced cytotoxicity (lactate dehydrogenase; LDH) were assessed. Silica uptake was determined via polarized light microscopy, and secretion of cytokines (TNFα, IL-6, IL-1β, IL-10, TGF-β) and procollagen were quantified by ELISA of PCLS conditioned media. Collagen deposition (Masson’s trichrome), macrophage number (F4/80), and α-SMA expression were assessed in fixed mPCLS. Results Viability of mPCLS and hPCLS was preserved with all silica treatments, but high cytotoxicity was observed with DQ12 and NIST 1878b silica (mPCLS). Macrophage uptake of Min-U-Sil 5, NIST 1878b, and DQ12 was confirmed in both mPCLS and hPCLS, with cell aggregation around silica particles and evidence of activated, foamy, and dying macrophage phenotypes visualised by histology in mPCLS. Silica-induced cytokine secretion of IL-1β, TNF-α, and IL-10 was highest in DQ12-treated hPCLS co-stimulated with LPS. Despite modest increases in procollagen secretion, there was no collagen deposition or increased α-SMA expression in silica-treated mPCLS regardless of LPS, at the 5-day endpoint. Conclusion Silica treatment of PCLS effectively induced acute inflammation but did not establish fibrosis. This model could be utilised to study mechanisms driving macrophage uptake in early silicosis and screen novel anti-inflammatory therapeutics. This abstract is funded by: Dust Diseases Board, iCare, Australia
Papagianis et al. (Fri,) studied this question.