Role of fibrocytes (CD34+) derived from peripheral blood in the pathology of dermal fibrosis in a model of scleroderma

Peripheral blood fibrocytes are a newly identified circulating leukocyte subpopulation that migrates into injured tissue where it may display fibroblast-like properties and participate in wound healing and fibrosis of skin and other organs. In this study, fibrocyte recruitment to skin in a bleomycin-induced dermal fibrosis model of human scleroderma in vivo was studied. Sections of skin from normal mice) control group) and bleomycin-treated C57BL/6 mice (Experimental group) were stained for Procollagen α2 Type I and CD34 and the double stained cells, and also fibrocytes were counted in the tissue sections. There were more fibrocytes in the dermis of experimental group than control group. There was no significant difference in fibrocyte number between skin samples with 1 week bleomycin treated and 3 weeks treated samples. We also found that fibrocytes (CD34+ and procollagen+) were mainly localized in clusters around blood vessels in the dermis and also individually close to epithelium. Our data suggest an important role of fibrocytes in the pathology of dermal fibrosis.