The inter-connection between fibrosis and microvascular remodeling in idiopathic pulmonary fibrosis: Reality or just a phenomenon

BACKGROUND: Idiopathic pulmonary fibrosis is the most frequent interstitial disease with the worst prognosis. It is characterized by an uncontrolled fibrosis which is difficult to manage. The pathogenesis of this disease remains unclear with many theories resulting in multiple target therapies. The relation between fibrosis and vascular remodeling has been debated in the literature with different results that may seem contradictory. AIM: We target to evaluate the connection between fibrosis and vascular remodeling in usual interstitial pneumonia. MATERIAL AND METHODS: 26 cases of idiopathic pulmonary fibrosis were reviewed by 2 pathologists and the diagnosis of UIP was retained according to the American Thoracic Society's criteria. Fibrotic changes and vascular remodeling were evaluated blindly. The fibrotic changes were classified as severe, intermediate and mild. Vascular occlusion was graded in 4 grades extending from medial hypertrophy (grade 1) to plexiform lesions of the vascular wall (grade 4). RESULTS: We noticed that severe degrees of fibrosis were correlated with severe grades of vascular obstruction. In fact, our 26 cases were classified as severe fibrosis in 11 cases with grade IV vascular lesions in 6 cases, intermediate fibrosis in 12 cases with grade II vascular lesions in 8 cases and mild fibrosis in 3 cases with grade I vascular lesions in all cases. CONCLUSION: Many theories have been reported concerning the UIP's pathogenesis. Recently, many authors reported that the primum movens of these lesions was an epithelial/endothelial injury which induces uncontrolled fibrosis and microvascular remodeling using different pathways. This puts emphasis on the necessity of multi-target therapies in order to improve the management of this fatal disease.