Levels Of Fibulin-1 In The Lung And Serum Are Increased In Fibrotic Interstitial Lung Disease

RATIONALE: Excessive pulmonary extracellular matrix (ECM) deposition leads to a progressive, permanent change in lung architecture that, in extreme cases, results in respiratory failure. Fibulin-1 (FBLN1), fibronectin (FN) periostin (PO) and tenascin-C (TNC) are ECM associated proteins that are increased in several diseases. The aim of this study was to measure levels of these proteins in the airway, parenchyma and serum of patients with a range of fibrotic lung diseases and determine the relationship between these levels and the degree of fibrosis. METHODS: Immunohistochemistry (IHC) was performed on paraffin-embedded formalin fixed tissue sections from patients with no lung disease and Idiopathic pulmonary fibrosis (IPF) (n=5-8 each) from 3 cohorts (Sydney, Perth, and Modena). Staining intensity was analysed by ImageJ to assess FBLN1 protein levels in tissue. Serum and pulmonary function tests from patients with interstitial lung disease (ILD) were collected from 3 cohorts (Sydney, Modena and San Francisco). Serum levels of FBLN1, PO, TNC and FN were analysed by western blot and sandwich ELISA. RESULTS: The level of FBLN1 immunostaining in the airways and parenchyma of patients with IPF was significantly increased compared to that of non-diseased individuals (n=4-5; p=0.02, n=5-8; p=0.001 respectively). The level of immunostaining for PO in the parenchyma of patients with IPF was significantly increased compared to those of non-diseased individuals (n=4-9; p=0.01). Serum levels of FBLN1 and PO but not TNC or FN were significantly increased in patients with IPF (n=44) from all three cohorts compared to non-diseased controls (n=17) (p<0.001) (Figure 1). Serum levels of FBLN1, in patients with ILDs were associated with fibrotic disease severity (Figure 2), as represented by composite physiologic index (R=0.404; p<0.001), DLco% predicted (R=-0.358; p=0.003), and FVC% predicted (R=-0.326; p=0.005).CONCLUSIONS: FBLN1 deposition is increased in both the airway and parenchyma of patients with IPF. Serum FBLN1 levels are elevated in patients with fibrotic ILD and are associated with the degree of fibrosis. Although serum PO levels and serum FBLN1 levels were associated with DLco and composite physiologic index, only FBLN1 was associated with FVC. Findings from this study indicate that FBLN1 is a novel IPF biomarker and raise the possibility that it can be used as a target for the development of new treatments for these diseases for which there are few treatment options.