Immunohistochemical examination of plexiform-like complex vascular lesions in the lungs of broiler chickens selected for susceptibility to idiopathic pulmonary arterial hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) is a disease of unknown cause that is characterized by elevated pulmonary arterial pressure and pulmonary vascular resistance, and by extensive vascular remodelling. In human IPAH patients, remodelling of the pulmonary vasculature results in the formation of plexiform lesions in the terminal pulmonary arterioles. Various molecules are expressed in the human plexiform lesions, including alpha smooth muscle actin, von Willebrand factor, vascular endothelial growth factor, vascular endothelial growth factor receptor type 2, hypoxia inducible factor-1α, survivin, tenascin, collagen, fibronectin, and various immune/inflammatory cells such as, cytotoxic lymphocytes, B lymphocytes, MHC class II cells, and monocytes/macrophages are also present. Plexiform lesions rarely develop in the lungs of laboratory animals, but plexiform-like complex vascular lesions (CVL) do develop spontaneously in the lungs of broiler chickens from an IPAH-susceptible line. To examine angioproliferative and immune-system-related activities associated with CVL in broiler lungs, paraformaldehyde-fixed, paraffin-embedded lung sections from 8-week-old to 24-week-old broiler chickens were stained immunohistochemically using monoclonal or polyclonal antibodies specific for angioproliferative molecules and immune/inflammatory cells. The CVL in the lungs of broiler chickens exhibited positive staining for both angioproliferative molecules and immune/inflammatory cells. These observations combined with the close histological resemblance of broiler CVL to the plexiform lesions of human IPAH patients further validates chickens from our IPAH-susceptible line as an excellent animal model of spontaneous plexogenic arteriopathy.