SFTPB in serum extracellular vesicles as a biomarker of progressive pulmonary fibrosis
Takatoshi Enomoto, et al.
Takatoshi Enomoto, et al.
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Research Article Pulmonology

SFTPB in serum extracellular vesicles as a biomarker of progressive pulmonary fibrosis

Abstract

Progressive pulmonary fibrosis (PPF), defined as the worsening of various interstitial lung diseases (ILDs), currently lacks useful biomarkers. To identify novel biomarkers for early detection of patients at risk of PPF, we performed a proteomic analysis of serum extracellular vesicles (EVs). Notably, the identified candidate biomarkers were enriched for lung-derived proteins participating in fibrosis-related pathways. Among them, pulmonary surfactant-associated protein B (SFTPB) in serum EVs could predict ILD progression better than the known biomarkers, serum KL-6 and SP-D, and it was identified as an independent prognostic factor from ILD-gender-age-physiology index. Subsequently, the utility of SFTPB for predicting ILD progression was evaluated further in 2 cohorts using serum EVs and serum, respectively, suggesting that SFTPB in serum EVs but not in serum was helpful. Among SFTPB forms, pro-SFTPB levels were increased in both serum EVs and lungs of patients with PPF compared with those of the control. Consistently, in a mouse model, the levels of pro-SFTPB, primarily originating from alveolar epithelial type 2 cells, were increased similarly in serum EVs and lungs, reflecting pro-fibrotic changes in the lungs, as supported by single-cell RNA sequencing. SFTPB, especially its pro-form, in serum EVs could serve as a biomarker for predicting ILD progression.

Authors

Takatoshi Enomoto, Yuya Shirai, Yoshito Takeda, Ryuya Edahiro, Shigeyuki Shichino, Mana Nakayama, Miho Takahashi-Itoh, Yoshimi Noda, Yuichi Adachi, Takahiro Kawasaki, Taro Koba, Yu Futami, Moto Yaga, Yuki Hosono, Hanako Yoshimura, Saori Amiya, Reina Hara, Makoto Yamamoto, Daisuke Nakatsubo, Yasuhiko Suga, Maiko Naito, Kentaro Masuhiro, Haruhiko Hirata, Kota Iwahori, Izumi Nagatomo, Kotaro Miyake, Shohei Koyama, Kiyoharu Fukushima, Takayuki Shiroyama, Yujiro Naito, Shinji Futami, Yayoi Natsume-Kitatani, Satoshi Nojima, Masahiro Yanagawa, Yasushi Shintani, Mari Nogami-Itoh, Kenji Mizuguchi, Jun Adachi, Takeshi Tomonaga, Yoshikazu Inoue, Atsushi Kumanogoh

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Figure 3

Clinical features of SFTPB in serum EVs in the discovery cohort, particularly associations with ILD progression.

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Clinical features of SFTPB in serum EVs in the discovery cohort, particu...
(A) Serum EV levels of SFTPB for each disease, measured by DIA in the discovery cohort. Pairwise intergroup comparisons between HCs and each ILD subgroup, as well as between non-progressive pulmonary fibrosis (non-PPF) and PPF in all ILDs, INSIP, CVD-ILD, and other ILD groups were performed using 2-tailed Student’s t test (Bonferroni correction), with **P < 0.01, and ***P < 0.001. (B) SFTPB levels in serum EVs correlated with the extent of interstitial shadows on CT scans. The differences were analyzed by ANOVA, and Holm’s method was applied to adjust for P values: **P < 0.01. (A and B) The boxes indicate interquartile ranges (75% and 25%) and medians; the upper and lower whiskers represent the 10% and 90% points, respectively. (C and D) Pearson correlations of SFTPB with percentage predicted forced vital capacity (%FVC) and the diffusing capacity for carbon monoxide (%DLco). ***P < 0.001. (E) Receiver operating characteristic (ROC) curves for evaluating SFTPB in serum EVs, serum KL-6, and SP-D as predicting composite outcome (relative decline in %FVC ≥ 10%, acute exacerbation, or death) within a year in 60 evaluable ILD cases in the discovery cohort. (F) Kaplan-Meier curve estimating the probability of overall survival (OS) stratified by the SFTPB levels in serum EVs. In 180 cases with INSIP, CVD-ILD, FHP, or unclassifiable ILD, high levels of SFTPB in serum EVs were significantly associated with high mortality. OS was defined as the period from the date of blood collection to the date of death from any cause.