Intravenous immunoglobulins prevents experimental fibrosis in a murine model of systemic sclerosis

Abstract

Introduction Systemic sclerosis (SSc) is an autoimmune disease characterized by an extensive multi-organs fibrosis. Immunosuppressants are effective in some extent but their incomplete efficacy is hampered by a higher infection risk. Intravenous immunoglobulins (IVIG) have a good safety profile, exhibit immunomodulatory and antifibrotic properties and hence could be a relevant treatment for SSc. The purpose of this study was to investigate the effects of IVIG in an experimental model of SSc. Materiels et methodes SSc was induced in 6 weeks old Balb/c mice by subcutaneous injections of HOCl five days a week during six weeks (n = 20), whereas control mice received subcutaneous injections of PBS (n = 20). Human IVIG was administrated intravenously by single retro-orbital injection at a dose of 2 g/kg the first day of HOCl administration (n = 20). A control group received an injection of 2% maltose (n = 20). Skin thickness was assessed during the protocol until the sacrifice (day 42). Skin tissues were collected in 4% PFA and processed for histological analysis. Dermal thickness was measured by performing a May-Grunwald–Giemsa staining of 4 μm skin sections; collagen deposition was assessed by performing a Picrosirius red-staining and quantified by using a color deconvolution method. In addition, immunostaining of skin sections was performed in order to evaluate the α-smooth muscle actin (α-SMA) expression. Frozen skin tissues were analyzed to also assess the mRNA expression of main inflammatory and pro-fibrotic genes (by quantitative reverse transcription polymerase chain reaction). Collagen deposition was also evaluated by measuring the content of hydroxyproline in 10 mg of frozen tissue. Resultats Mice exposed to HOCl developed a diffuse cutaneous SSc with higher dermal thickness compared to the PBS group. IVIG significantly reduced dermal thickness and collagen deposition in HOCl-receiving mice. The amount of α-SMA positive cells evaluated by immunofluorescence was reduced in the HOCl treated mice receiving IVIG. The mRNA expression profile of various markers of fibrosis (fibronectin, TGFβ) or inflammation (TNFα, IL-1β, IL-6) were also significantly decreased in the skin of HOCl mice treated with IVIG compared to HOCl-treated mice receiving 2% maltose. Conclusion These results demonstrate the efficacy of IVIG in preventing experimental fibrosis in a HOCl murine model of SSc.