Abstract
Introduction Fibrocytes are emerging myeloid-derived circulating cells that can migrate into damaged tissues and usually contribute to their repair. Key features of fibrocytes include the expression myeloid markers, production of extracellular matrix proteins, and secretion of various humoral factors that activate resident fibroblasts; they also have the potential to differentiate into fibroblasts. However, no specific surface markers have been identified to identify fibrocytes in vivo. One reason could be that the method used to detect fibrocytes requires intracellular collagen staining. Methods In the present study, to establish an improved method for the detection of lung fibrocytes and to analyze viable fibrocytes, we used collagen I(α)2-green fluorescent protein (Col-GFP) reporter mice, which had undergone the intratracheal instillation of bleomycin (BLM). Results Using flow cytometry to gate out cells with autofluorescence, we clearly found that CD45+ GFP+ cells resided in the lungs of Col-GFP mice at a steady state and these cells increased after BLM injury, peaking at Day 14. These cells expressed not only known cell surface markers of fibrocytes, but also some novel markers, in addition to a low level of collagen I in comparison to CD45- GFP+ cells. Conclusion Our findings suggest that the improved method can be a useful for the detection of pure lung fibrocytes and allows us to further analyze the characteristics of viable fibrocytes.
Highlights
Fibrocytes are emerging myeloid‐derived circulating cells that can migrate into damaged tissues and usually contribute to their repair
The key features of fibrocytes include the expression of myeloid markers such as CD34, CD45, CD14 and CD11a, CD11b, the production of extracellular matrix proteins such as collagen‐I, vimentin, and α‐smooth muscle actin, and the secretion of various humoral factors that activate resident fibroblasts; they have the potential to differentiate into fibroblasts.[5,9]
Using flow cytometry to gate out cells with autofluorescence, we clearly found CD45+ green fluorescent protein (GFP)+ cells residing in the lungs of collagen I(α)2‐green fluorescent protein (Col‐GFP) mice at a steady state and demonstrated that these cells increased after BLM injury
Summary
Fibrocytes are emerging myeloid‐derived circulating cells that can migrate into damaged tissues and usually contribute to their repair. Fibrocytes are myeloid‐derived circulating cells with characteristics of both fibroblasts and monocytes, which are described in 1994 by Bucala et al.[4] Since this discovery, there have been an increasing number of reports on the characterization of fibrocytes and their role in the pathogenesis of various human diseases.[5] Fibrocytes can migrate into damaged tissues and usually contribute to their repair.[6,7,8] The key features of fibrocytes include the expression of myeloid markers such as CD34, CD45, CD14 and CD11a, CD11b, the production of extracellular matrix proteins such as collagen‐I, vimentin, and α‐smooth muscle actin, and the secretion of various humoral factors that activate resident fibroblasts; they have the potential to differentiate into fibroblasts.[5,9]
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