Mfge8 diminishes the severity of tissue fibrosis in mice by binding and targeting collagen for uptake by macrophages
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
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
View: Text | PDF
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

×

Figure 6

Mfge8–/– fibroblasts do not have impaired collagen uptake.

Options: View larger image (or click on image) Download as PowerPoint
Mfge8–/– fibroblasts do not have impaired collagen uptake. (A and B...
(A and B) Primary lung fibroblasts from Mfge8–/– and Mfge8+/+ mice at passage 4 were incubated for 90 minutes with FITC-conjugated type l collagen, and unbound/uningested collagen was removed with multiple washes. Cells were then incubated with 50 μg/ml trypsin and 50 μg/ml proteinase K to remove membrane-bound collagen. Collagen in the membrane-bound portion (supernatant after enzymatic treatment) and intracellular portion (pellet remaining after enzymatic treatment) was quantified by a spectrofluorometer. There was no difference in membrane-bound (A) or intracellular (B) collagen with or without the addition of rMfge8 (13 μg/ml). Data are presented as mean ± SEM.