A35-32 Monocyte-derived CST3 In Early Interstitial Lung Disease

Rationale

Interstitial lung disease (ILD) is a heterogeneous group of disorders characterized by pulmonary interstitial remodeling and abnormal collagen deposition, in which dysregulation of the protease-antiprotease system plays a critical role. Pulmonary fibrosis is irreversible at advanced stages. Interstitial lung abnormalities (ILA) are incidental radiologic findings detected on chest computed tomography (CT) that are associated with fibrosis and are considered an early stage of ILD. Cystatin C (CST3) is a secreted cysteine protease inhibitor. Previous studies have reported elevated levels of CST3 in the serum of patients with idiopathic pulmonary fibrosis. However, the cellular source of CST3 in the peripheral blood of individuals at the early stage of ILD remains unclear. The aim of this study was to investigate the cellular origin of CST3 in individuals with ILA.

Methods

Peripheral blood samples were prospectively collected from ILA individuals who underwent routine health examinations with chest CT between November 2023 and August 2024. Peripheral blood mononuclear cells (PBMC) were isolated from these samples. After matching for age and sex, PBMCs from two individuals with subpleural non-fibrotic ILA and three individuals with subpleural fibrotic ILA were subjected to single-cell RNA sequencing. Cell clustering, annotation, and differential expression analysis were performed to characterize the cellular expression profile of CST3 in PBMCs from individuals with ILA.

Results

PBMC were composed of monocytes and lymphocytes. CST3 mRNA expression was significantly higher in monocytes than in other PBMC populations. Further analysis of monocyte subsets revealed that CST3 exhibited the highest average expression in classical monocytes, which was significantly greater than that observed in non-classical (2.472±0.701 v.s. 2.386±0.805, P < 0.0001) and intermediate monocytes (2.472±0.701 v.s. 1.555±1.148, P < 0.0001). Subtype-specific analysis demonstrated that the average CST3 expression levels in both classical (2.490±0.685 v.s. 2.445±0.724, P = 0.0103) and non-classical monocytes (2.440±0.791 v.s. 2.330±0.816, P = 0.0155) were significantly higher in individuals with subpleural fibrotic ILA compared with those with subpleural non-fibrotic ILA. In contrast, no significant difference in CST3 expression was observed in intermediate monocytes between the two groups.

Conclusion

CST3 in peripheral blood is predominantly derived from monocytes.

This abstract is funded by: National Natural Science Foundation of China (No. 32501152)