Ontogeny of pulmonary cyclooxygenase-1 (COX-1) and -2 (COX-2)

Prostaglandins synthesized by enzymatic reactions such as cyclooxygenases have been implicated in lung pathophysiology. The goal of this study was to delineate the pulmonary ontogeny of cyclooxygenase enzymes (COX-1 and COX-2) immunohistochemical expression and cellular localization in various microanatomic locations of lungs from pre-term, term, and post-natal lambs. Lung tissues were obtained at 115 and 130 days of gestation from pre-term lambs, 145 days (term; complete gestation), and 15 days post-natally. No significant differences were seen in lung COX-1 expression at various microanatomic locations during pre-term, term, or postnatally. Moderate to strong COX-1 expression was present in macrophages, alveolar septa, bronchial smooth muscle cells, bronchiolar smooth muscle cells, vascular endothelial cells, and vascular smooth muscle cells. Minimal COX-1 expression was present in bronchial and bronchiolar epithelial cells. Most microanatomic locations lacked COX-2 expression with the exception of weak expression that was present in bronchial and bronchiolar epithelial cells at 145 days of full gestation and 15 days post-natally. This work suggests that: (a) COX-1 is constitutively expressed in lungs from pre-term, term, and post-natal lambs in various microanatomic pulmonary locations, (b) there is differential expression of COX-1 and COX-2 in the developing lung, and (c) COX-2 does not appear to play a role in lung fetal development, at least in neonatal lambs.