Progesterone Decreased Cell Infiltration in Airways of Systemic Sclerosis Mice Model

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.