title: Paquinimod reduces skin fibrosis in tight skin 1 mice, an experimental model of systemic sclerosis.
abstract: BACKGROUND
  Systemic Sclerosis (SSc) is an autoimmune disease characterized by vascular and immune dysfunction. A hallmark of SSc is the excessive accumulation of extracellular matrix in the skin and in internal organs. There is a high and unmet medical need for novel therapies in this disease. The pathogenesis of SSc is complex and still poorly understood, but the innate immune system has emerged as an important factor in the disease. SSc patients show increased numbers of macrophages/monocytes in the blood and in the skin compared to healthy individuals and these cells are important sources of profibrotic cytokines and chemokines. Paquinimod belongs to a class of orally active quinoline-3-carboxamide (quinoline) derivatives with immunomodulatory properties and has shown effects in several models of autoimmune/inflammatory disorders. Paquinimod is currently in clinical development for treatment of SSc. The immunomodulatory effects of paquinimod is by targeting the myeloid cell compartment via the S100A9 protein.
  
  
  OBJECTIVE
  In this study we investigate whether targeting of myeloid cells by paquinimod can effect disease development in an experimental model of SSc, the tight skin 1 (Tsk-1) mouse model.
  
  
  METHODS
  Seven weeks old female B6.Cg-Fbn1(Tsk)/J (Tsk-1) mice were treated with vehicle or paquinimod at the dose of 5 or 25mg/kg/day in the drinking water for 8 weeks. The effect of paquinimod on the level of skin fibrosis and on different subpopulations within the myeloid cell compartment in skin biopsies were evaluated by using histology, immunohistochemisty, a hydroxyproline assay and real-time PCR. Furthermore, the level of IgG in serum from treated animals was also analysed. The statistical analyses were performed using Mann-Whitney nonparametric two tailed rank test.
  
  
  RESULTS
  The results show that treatment with paquinimod reduces skin fibrosis measured as reduction of skin thickness and decreased number of myofibroblasts and total hydroxyproline content. The effect on fibrosis was associated with a polarization of macrophages in the skin from a pro-fibrotic M2 to a M1 phenotype. Paquinimod treatment also resulted in a reduced TGFβ-response in the skin and an abrogation of the increased auto-antibody production in this SSc model.
  
  
  CONCLUSIONS
  Paquinimod reduces skin fibrosis in an experimental model of SSc, and this effect correlates with local and systemic effects on the immune system.
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Martin.Stenstrom@activebiotech.com.
authors.forename: Martin
authors.initials: M
authors.lastname: Stenström
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Helen.Nyhlen@activebiotech.com.
authors.forename: Helén Carlsson
authors.initials: HC
authors.lastname: Nyhlén
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Marie.Torngren@activebiotech.com.
authors.forename: Marie
authors.initials: M
authors.lastname: Törngren
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: David.Liberg@activebiotech.com.
authors.forename: David
authors.initials: D
authors.lastname: Liberg
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Birgitta.Sparre@activebiotech.com.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Sparre
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Helen.Tuvesson@activebiotech.com.
authors.forename: Helén
authors.initials: H
authors.lastname: Tuvesson
authors.affiliation: Active Biotech AB, Lund, Sweden. Electronic address: Helena.Eriksson@activebiotech.com.
authors.forename: Helena
authors.initials: H
authors.lastname: Eriksson
authors.affiliation: Active Biotech AB, Lund, Sweden; Immunology Group, Lund University, Sweden. Electronic address: Tomas.Leanderson@activebiotech.com.
authors.forename: Tomas
authors.initials: T
authors.lastname: Leanderson
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000188:drug therapy* / Q000276:immunology; D040502:Calgranulin B / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005355:Fibrosis; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D011804:Quinolines / Q000627:therapeutic use*; D012595:Scleroderma, Systemic / Q000188:drug therapy* / Q000473:pathology; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D040502:Calgranulin B; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D011804:Quinolines; C576329:S100A9 protein, mouse; D016212:Transforming Growth Factor beta; C573440:paquinimod
keywords: M2 macrophages; Myofibroblasts; Paquinimod; Skin fibrosis; Systemic sclerosis; Tight skin 1 mice