Characterization of Fibroblast-specific Protein 1 in Pulmonary Fibrosis

Abstract

Because fibroblasts produce collagen and other extracellular matrix components that are deposited during tissue fibrosis, defining the behavior of these cells is critical to understanding the pathogenesis of fibrotic diseases. We investigated the utility of fibroblast-specific protein 1 (FSP1), a member of the calmodulin S100 troponin C superfamily, for identifying lung fibroblasts in a murine model of pulmonary fibrosis induced by intratracheal administration of bleomycin. Protein and mRNA expression of FSP1 was minimal in untreated lungs, but increased by 1 week after bleomycin administration and remained increased at 2 and 3 weeks after treatment. By immunohistochemistry, the number of FSP1(+) cells increased in a dose-dependent manner in the lungs after bleomycin treatment. Colocalization of alpha1 procollagen and FSP1 in interstitial cells demonstrated that FSP1(+) fibroblasts contribute to the deposition of collagen after bleomycin administration. In primary lung cell cultures, lung fibroblasts, but not macrophages or type II alveolar epithelial cells, expressed FSP1. FSP1 also identified fibroblasts in lung biopsy specimens from patients with documented usual interstitial pneumonitis. Therefore, FSP1 is an improved marker for lung fibroblasts that could be useful for investigating the pathogenesis of pulmonary fibrosis.

SPARC Oppositely Regulates Inflammation and Fibrosis in Bleomycin-Induced Lung Damage

“…17 This approach, however, is complicated by the different origin of collagen-producing cells, which, besides resident fibroblasts, include fibrocytes 21 and mesenchymal stem cells of bone marrow origin (BMMSCs). 22 To evaluate the contribution of bone marrowderived collagen-producing cells in bleomycin-induced fibrosis, we designed ad hoc bone marrow chimeras, which allowed us to distinguish host-and bone marrowderived fibroblasts and fibrocytes on the basis of CXCR4, FSP1, 23 and CD45 markers (see Supplemental Figure S2 at http://ajp.amjpathol.org). CD45.2 mice were lethally irradiated and transplanted with a CD45.1 bone marrow to distinguish donor and host cells.…”

Endoplasmic reticulum stress enhances fibrotic remodeling in the lungs

“…3D). In previous studies, we have used S100A4 as a fibroblast marker in the lungs (14)(15)(16)(17). Therefore, we evaluated lung sections by IHC for S100A4 expression and noted greater numbers of S100A4-positive fibroblasts in L188Q SFTPC mice compared with WT controls after bleomycin treatment ( Additionally, we wanted to determine whether lung mechanics were different at 3 wk after bleomycin treatment in L188Q SFTPC mice.…”

“…in mice by intubation as previously described (17). Lungs were harvested for histology, frozen tissue, bronchoalveolar lavage, or cell isolation as previously described (14)(15)(16)(17). L188Q SFTPC mice and controls were maintained on normal water ad libitum until transgene activation was desired.…”

“…Formalin-fixed lung sections were prepared as previously described (14)(15)(16). IHC (14,15), immunofluorescence (16,17), TUNEL (15,17), and bronchoalveolar lavage with cell counts (15,17) were performed as previously described. RNA isolation, real-time RT-PCR, and Western blot analysis were performed by using standard techniques (detailed in SI Materials and Methods).…”

“…After 24 h, cells were harvested for Western blot analysis. Type II AECs were isolated as previously described (14,16).…”