INTERNATIONAL JOURNAL OF REGENERATIVE MEDICINE | ISSN 2613-5914 Available online at www.sciencerepository.org Science Repository * Correspondence to: Nazanin Mojtabavi, Institute of immunology and infectious disease, immunology research center, Iran University of medical sciences, Department of Immunology, Iran University of medical sciences, Tehran, Iran; Tel: 00982186703281; ORCID: 0000-0002-3539-9483; E-mail: Mojtabavi.n@iums.ac.ir © 2020 Nazanin Mojtabavi. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Hosting by Science Repository. All rights reserved. http://dx.doi.org/10.31487/j.RGM.2020.01.06 Research Article Progesterone Decreased Cell Infiltration in Airways of Systemic Sclerosis Mice Model Fatemeh Vafashoar 1,2 , Kazem Mousavizadeh 3 , Hadi Poormoghim 4 , Pendar Safari 1,2 , Amir Haghighi 5 and Nazanin Mojtabavi 1,2* 1 Institute of immunology and infectious disease, immunology research center, Iran University of medical sciences, Tehran, Iran 2 Department of Immunology, Iran University of medical sciences, Tehran, Iran 3 Faculty of Advanced Technologies in Medicine, Iran University of Medica sciences, Tehran , Iran 4 Scleroderma study group, Firuzgar hospital, Iran University of medical sciences, Tehran, Iran 5 Nicolaus Copernicus University, Collegium Medicum in Bydgoszcz, Bydgoszcz, Poland A R T I C L E I N F O Article history: Received: 2 May, 2020 Accepted: 22 May, 2020 Published: 27 August, 2020 Keywords: Systemic sclerosis progesterone bronchoalveolar lavage fibrosis bleomycin A B S T R A C T Systemic sclerosis (SSc) is the fibrotic autoimmune disease with a higher incidence in women. Lung fibrosis is the most common cause of death in SSc patients. Sex steroids have crucial role in the induction of autoimmune diseases. Progesterone impacts autoimmunity by direct action on parenchymal cells or through its immunomodulatory effect. This study aimed to investigate the effect of progesterone on the cellularity of airways in an animal model of systemic sclerosis. 6 groups of mice were considered in this study. Systemic sclerosis (SSc) was induced in female BALB/c mice by subcutaneous injection of bleomycin for 28 days. For evaluating the effect of Progesterone in SSc model, Progesterone was administered subcutaneously parallel with bleomycin for 28 days or one week after the first administration of bleomycin for 21 days. Further, three control groups were included in this study. On day 29, under lethal anesthesia bronchoalveolar lavage (BAL) was collected and evaluated for cellularity. Our results indicate the increment of cells in BAL of SSc (P<0.0001) mice. Administration of Progesterone for 28 days significantly reduced the infiltrating cells in BALs (P<0.01) of SSc mice. The differential count of BALs indicates that Progesterone reduced the number of lymphocytes (P˂0.05) in SSc mice but did not affect the number of macrophages. Therefore, we conclude that progesterone reduced the inflammatory cells in airways by decreasing the number of lymphocytes. © 2020 Nazanin Mojtabavi. Hosting by Science Repository. All rights reserved. Introduction Systemic sclerosis (SSc) is a chronic connective tissue disease with immune system dysregulation, microvascular injury and fibrosis of skin and internal organs. Progressive fibrosis compromises the function of organs by continuous accumulation of extracellular matrix (ECM) components and the replacement of normal tissue with permanent scar tissue [1]. Lung dysfunction because of fibrosis is the leading cause of morbidity and mortality in SSc patients [2]. Fibrosis is initiated by a tissue injury and activation of innate and adaptive immune responses. Activation of the immune system results in activation of M2-type macrophages (alternatively-activated), Th2 cells, and differentiation of fibroblasts to myofibroblasts [3]. An investigation has indicated the increment of collagen synthesis has occurred in fibroblasts adjacent to inflammatory cells. This hypothesis confirms that the necessary signal for activation of fibroblasts and the production of collagen is provided by adjacent inflammatory cells, primarily by lymphocytes [4]. Systemic sclerosis (SSc) is a female predominant autoimmune disease (AD). The prevalence of SSc is three-fold more common in women than men, and its incidence during the reproductive period (ages 15-50) is 15- times higher [5]. The predominancy of autoimmune diseases in females