Diminished Induction of Skin Fibrosis in Mice with MCP-1 Deficiency

Abstract

Scar and fibrosis are often the end result of mechanical injury and inflammatory diseases. One chemokine that is repeatedly linked to fibrotic responses is monocyte chemoattractant protein-1 (MCP-1). We utilized a murine fibrosis model that produces dermal lesions similar to scleroderma to evaluate collagen fibrillogenesis in the absence of MCP-1. Dermal fibrosis was induced by subcutaneous injection of bleomycin into the dorsal skin of MCP-1-/- and wild-type C57BL/6 mice. After 4 weeks of daily injections, bleomycin treatment led to thickened collagen bundles with robust inflammation in the lesional dermis of wild-type mice. In contrast, the lesional skin of MCP-1-/- mice exhibited a dermal architecture similar to phosphate-buffered saline (PBS)-injected control and normal skin, with few inflammatory cells. Ultrastructural analysis of the lesional dermis from bleomycin-injected wild-type mice revealed markedly abnormal arrangement of collagen fibrils, with normal large diameter collagen fibrils replaced by small collagen fibrils of 41.5 nm. In comparison, the dermis of bleomycin-injected MCP-1-/- mice displayed a uniform pattern of fibril diameters that was similar to normal skin (average diameter 76.7 nm). The findings implicate MCP-1 as a key determinant in the development of skin fibrosis induced by bleomycin, and suggest that MCP-1 may influence collagen fiber formation in vivo.

Regulation of scar formation by vascular endothelial growth factor

“…In contrast, scar tissue from control mice injected with IgG antibodies contained a high frequency of very small-diameter fibrils (less than 40 nm), similar to what is found in models of cutaneous fibrosis. [20][21][22] Scars from mice injected with anti-VEGF antibodies contained a lower frequency of the small-diameter fibrils (0-40 nm) and a higher frequency of fibrils within the normal range (41-80 nm) compared with control scars. The results suggest that neutralization of VEGF not only reduced the amount of scar tissue formed (Figure 6), but also improved the quality of the scar tissue that did form by shifting the collagen fibril distribution to a state more closely resembling normal skin (Figure 7).…”

“…Collagen fibril diameter measurements have been used previously to evaluate the degree of cutaneous fibrosis. [20][21][22] Three normal skin samples and six scar samples from each treatment group, all from different mice, were used for analysis. Each micrograph was divided into four parts for analysis and fibrils from four micrographs per sample were measured.…”

Systemic sclerosis: a prototypic multisystem fibrotic disorder

“…The mice also manifest evidence of pulmonary and renal fibrosis. In light of its reproducibility, relative strain independence, and ease of induction, the subcutaneous bleomycin model is used with increasing frequency to investigate the roles of specific gene products in SSclike disease (19,20). Transplantation of MHC-mismatched BM or spleen cells into sublethally irradiated recipient mice results in an SSc-like condition resembling chronic graft-versus-host disease, with skin and lung fibrosis accompanied by evidence of autoimmunity (21,22).…”

Essential Roles for Early Growth Response Transcription Factor Egr-1 in Tissue Fibrosis and Wound Healing

“…26 Electron microscopy and analysis of collagen fibril diameter were performed as previously described. 27 Briefly, lesional skin tissue from wild-type and Egr-1 Ϫ/Ϫ mice was fixed in 4% glutaraldehyde and after processing, embedded in Spurr's epoxy resin (Electron Microscopy Sciences, Fort Washington, PA). Ultrathin sections (80 nm) were stained with uracyl acetate and lead citrate, and examined with a transmission electron microscope (JEOL 1220, JEOL, Peabody, MA).…”