{
  "abstract": "Introduction Plasmacytoid dendritic cells (pDC) are innate immune cells specialized in rapidly producing large amounts of type I interferon (IFN-I) that have been associated with systemic sclerosis (SSc). They infiltrate affected tissues, drive overproduction of IFN-I, and their depletion alleviates fibrosis in murine models. Due to their high secretory capacity, pDC have a large endoplasmic reticulum (ER) and basal levels of ER stress, resulting from the accumulation of misfolded proteins. pDC activation is impacted by ER stress, and it has been found that there is dysregulation of ER stress-related genes in pDC of SSc patients. Therefore, we are exploring the contribution of pDC and ER stress for fibrosis development.Material and Methods We established an in vitro platform to study interactions between human pDC, and IMR-90 lung fibroblasts. Mono and co-cultures were exposed to the ER stress inducers tunicamycin, subtilase cytotoxin (SubAB) and HA-15. Cells were also treated with the TLR7 agonist CL307. Extracellular matrix (ECM) protein production and cellular activation were evaluated by immunoblotting and RT-qPCR.Results It was found that the pDC cell line CAL-1 physically interacts with IMR90 cells. Exposure of pDC-IMR90 co-cultures to SubAB or HA15 resulted in increased expression of fibronectin and alpha-smooth muscle actin (alpha-SMA). This effect required the presence of the ER stress sensor protein kinase R-like ER kinase (PERK), but not stimulator of IFN genes (STING) on CAL-1 cells. Treatment with a TLR7 agonist in conjunction with ER stress induction had a synergistic effect on production of IFN-I, but it did not interfere with fibroblast activation in the co-cultures. Moreover, cell-to-cell contact between IMR-90 and CAL-1 was required, since soluble factors produced by SubAB-exposed cells were insufficient to induce fibroblast activation.Conclusions Altogether, our results suggest that both pDC and ER stress induction contribute to fibroblast activation and that IFN-I is not the driver of ER stress induced-ECM production in the co-cultures. Currently, we are further elucidating the mechanism behind this effect, aiming to identify molecular targets for therapeutic strategies against tissue fibrosis.This work is supported by the World Scleroderma Foundation and Edith Busch Stiftung (Research Grant Programme 2022-2023). Work was also developed within the scope of iBiMED – Institute of Biomedicine (UI 4501) and the project DOI 10.54499/2022.03217.PTDC, all supported by national funds (OE) through FCT - Fundação para a Ciência e Tecnologia, I.P.. FCT is acknowledged for the individual grant to M.D.M. (SFRH/2024.05442.BDANA).",
  "authors": [
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Beatriz H Ferreira"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Mariana D Machado"
    },
    {
      "affiliations": [
        "Unidade Local de Saúde da Região de Aveiro, Rheumatology Department, Aveiro, Portugal"
      ],
      "name": "Carolina Mazeda"
    },
    {
      "affiliations": [
        "Unidade Local de Saúde da Região de Aveiro, Rheumatology Department, Aveiro, Portugal"
      ],
      "name": "Catarina R Silva"
    },
    {
      "affiliations": [
        "Unidade Local de Saúde da Região de Aveiro, Rheumatology Department, Aveiro, Portugal"
      ],
      "name": "Eduardo Dourado"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Camila Castro"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Fátima Leite-Pinheiro"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Andreia Mendes"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Luís Mendes"
    },
    {
      "affiliations": [
        "Department of Molecular and Biomedical Science, Research Centre for Infectious Diseases, University of Adelaide, Adelaide, Australia"
      ],
      "name": "Adrienne W Paton"
    },
    {
      "affiliations": [
        "Department of Molecular and Biomedical Science, Research Centre for Infectious Diseases, University of Adelaide, Adelaide, Australia"
      ],
      "name": "James C Paton"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal",
        "Aix Marseille Univ, CNRS, INSERM, CIML, Centre d’Immunologie de Marseille-Luminy, Marseille, Marseille, France"
      ],
      "name": "Philippe Pierre"
    },
    {
      "affiliations": [
        "iBiMED - Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, Portugal"
      ],
      "name": "Catarina R Almeida"
    }
  ],
  "title": "P.036 The involvement of PDC and ER stress in systemic sclerosis-associated fibrosis",
  "uid": "6fac3403-3cba-5469-a157-4f37bc75b8df"
}