MMP9 and pulmonary fibrosis: The aim of the present study was to contribute to this field through the assessment of specific biomarkers, such as cyclooxygenase (COX-2), inducible nitric oxide synthase (i-NOS), metalloproteinase-9 (MMP-9), erythropoietin receptor (EPO-R), and cytochrome C (Cyt-C), in a bleomycin-induced model of pulmonary fibrosis.