Mfge8 diminishes the severity of tissue fibrosis in mice by binding and targeting collagen for uptake by macrophages
Kamran Atabai, … , Zena Werb, Dean Sheppard
Kamran Atabai, … , Zena Werb, Dean Sheppard
Published November 2, 2009
Citation Information: J Clin Invest. 2009;119(12):3713-3722. https://doi.org/10.1172/JCI40053.
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Research Article Pulmonology

Mfge8 diminishes the severity of tissue fibrosis in mice by binding and targeting collagen for uptake by macrophages

Abstract

Milk fat globule epidermal growth factor 8 (Mfge8) is a soluble glycoprotein known to regulate inflammation and immunity by mediating apoptotic cell clearance. Since fibrosis can occur as a result of exaggerated apoptosis and inflammation, we set out to investigate the hypothesis that Mfge8 might negatively regulate tissue fibrosis. We report here that Mfge8 does decrease the severity of tissue fibrosis in a mouse model of pulmonary fibrosis; however, it does so not through effects on inflammation and apoptotic cell clearance, but by binding and targeting collagen for cellular uptake through its discoidin domains. Initial analysis revealed that Mfge8–/– mice exhibited enhanced pulmonary fibrosis after bleomycin-induced lung injury. However, they did not have increased inflammation or impaired apoptotic cell clearance after lung injury compared with Mfge8+/+ mice; rather, they had a defect in collagen turnover. Further experiments indicated that Mfge8 directly bound collagen and that Mfge8–/– macrophages exhibited defective collagen uptake that could be rescued by recombinant Mfge8 containing at least one discoidin domain. These data demonstrate a critical role for Mfge8 in decreasing the severity of murine tissue fibrosis by facilitating the removal of accumulated collagen.

Authors

Kamran Atabai, Sina Jame, Nabil Azhar, Alex Kuo, Michael Lam, William McKleroy, Greg DeHart, Salman Rahman, Dee Dee Xia, Andrew C. Melton, Paul Wolters, Claire L. Emson, Scott M. Turner, Zena Werb, Dean Sheppard

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Figure 1

Mfge8 expression is induced by lung injury.

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Mfge8 expression is induced by lung injury. (A and B) Lung sections take...
(A and B) Lung sections taken from adult wild-type mice were stained with anti-Mfge8 antibody. Mfge8 was expressed in the alveolar interstitium (arrow in A) and pulmonary endothelium (arrow in B). Scale bars: 10 μm. (C and D) Alveolar macrophages were obtained by BAL after saline administration (C) or 5 days after bleomycin administration (5 U/kg) (D). Mfge8 staining was present in macrophages from saline-treated animals (C), and the intensity of expression increased after bleomycin treatment (D). Scale bars: 10 μm. (E) Ten micrograms of protein from total lung homogenates taken at the indicated days after bleomycin treatment (1.1 U/kg) or 7 days after saline treatment was loaded for a Western blot using an anti-Mfge8 antibody. An antibody against Crk was used to demonstrate equal loading of protein. (F) One microgram of protein from lung homogenates obtained from human patients with IPF was loaded for a Western blot using an anti-lactadherin antibody (Lact.). Control samples were from lungs rejected for transplantation. An antibody against Crk was used to demonstrate loading of protein.