Abstract
BackgroundLung fibrosis is a serious life-threatening condition whose manifestation varies according to the localization and characteristics of fibroblasts, which are considered heterogeneous. Therefore, to better understand the pathology and improve diagnosis and treatment of this disease, it is necessary to elucidate the nature of this heterogeneity and identify markers for the accurate classification of human lung fibroblast subtypes.MethodsWe characterized distinct mouse lung fibroblast subpopulations isolated by fluorescence-activated cell sorting (FACS) and performed microarray analysis to identify molecular markers that could be useful for human lung fibroblast classification. Based on the expression of these markers, we evaluated the fibroblast-like cell subtype localization in normal human lung samples and lung samples from patients with idiopathic pulmonary fibrosis (IPF).ResultsMouse lung fibroblasts were classified into Sca-1high fibroblasts and Sca-1low fibroblasts by in vitro biological analyses. Through microarray analysis, we demonstrated CD248 and integrin alpha-8 (ITGA8) as cell surface markers for Sca-1high fibroblasts and Sca-1low fibroblasts, respectively. In mouse lungs, Sca-1high fibroblasts and Sca-1low fibroblasts were localized in the collagen fiber-rich connective tissue and elastic fiber-rich connective tissue, respectively. In normal human lungs and IPF lungs, two corresponding major fibroblast-like cell subtypes were identified: CD248highITGA8low fibroblast-like cells and CD248lowITGA8high fibroblast-like cells, localized in the collagen fiber-rich connective tissue and in the elastic fiber-rich connective tissue, respectively.ConclusionCD248highITGA8low fibroblast-like cells and CD248lowITGA8high fibroblast-like cells were localized in an almost exclusive manner in human lung specimens. This human lung fibroblast classification using two cell surface markers may be helpful for further detailed investigations of the functions of lung fibroblast subtypes, which can provide new insights into lung development and the pathological processes underlying fibrotic lung diseases.
Highlights
Lung fibrosis is a serious life-threatening condition whose manifestation varies according to the localization and characteristics of fibroblasts, which are considered heterogeneous
Isolation of immunophenotypically distinct fibroblasts from the mouse lungs by fluorescence-activated cell sorting (FACS) Through FACS analysis, using antibodies against six lineage-specific cell surface markers (Additional file 1: Table S1), we isolated linneg cells from the mouse lungs; this cell population comprised a small number of lineagecommitted cells, including vascular endothelial cells, hematopoietic cells, pericytes, smooth muscle cells, epithelial cells, lymphatic endothelial cells, and erythrocytes (Fig. 1a, left and middle panels)
FACS analysis separated fibroblasts into Sca-1highThy-1low (A-type fibroblasts) and Sca-1highThy-1high (B-type fibroblasts) from linnegPDGFRAhigh cells. We identified another fibroblast subpopulation, Sca-1low (C-type fibroblasts) that has not been reported to date
Summary
Lung fibrosis is a serious life-threatening condition whose manifestation varies according to the localization and characteristics of fibroblasts, which are considered heterogeneous. To better understand the pathology and improve diagnosis and treatment of this disease, it is necessary to elucidate the nature of this heterogeneity and identify markers for the accurate classification of human lung fibroblast subtypes. In idiopathic pulmonary fibrosis (IPF), a representative lethal lung fibrotic disease, fibrosis is predominant in the perilobular To better understand the heterogeneity of fibrosis in IPF, it is first necessary to identify fibroblast subtypes, as well as their localization patterns, and to elucidate their distinct roles. Molecular markers for human lung fibroblast subtypes have not yet been well established. The discovery of a set of markers that may be used to define different human fibroblast subtypes is necessary
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