Changes Of Ultrastructure And TGFβ₁ Expression In The Lung Of Premature Neonatal Rats Exposed To Hyperoxia

ObjectiveTo explore the changes of ultrastructure and TGF β 1 expression in the lung of neonatal premature rats exposed to hyperoxia.MethodsNinety-nine neonatal SD rats of 21-day gestational age were divided into experimental group(n=54) and control group(n=45). They were randomized into the 3rd, 7th and 14th day subgroup respectively. The rats in experimental group inhaled 95 % oxygen, and the control were fed in room air. the lung tissues were removed for pathological diagnosis by H.E and V.G stained according to the subgroup, the alteration of ultrastructure was observed by transmission electron microscope; the expression of TGF β1 was determined by immunohistochemistry and then semi-quantitative analyzation was performed. the difference of expression among groups was compared by rank sum test.Results1. Destroyed alveolars, decreased number of alveoli, local atelectasis and thickened alveoli septum were observed in the hyperoxic-damaged lungs of the 7th and 14th day. Deposited collagen fibers in alveoli septum could also be observed by V.G staining. 2.Compared with air group, hyperoxic group shows: (1) Swollen mitochondrions, empty lamellar bodys, and shed microvillus were found in type II alveolar epithelial cells;(2)The electronic density decreased in the cytoplasm of type I alveolar epithelial cells, plasmolysis and swollen mitochondrions were also observed in it;(3) Mitochondrions swelled in endothelial cells on the postnatal 3rd and 7th day, lipid droplet appeared in nucleus, and some organells were destroyed in cytoplasm at the postnatal 14th day;(4) Organells such as endoplasmic reticulunu Golgi apparatus and mitochondrions were presented in the cytoplasm of fibroblasts after the postnatal 7th day, increased collagen fibers were deposited in the extracellular matrix. 3. TGF β1 expression in the lung of both groups became stronger as days went on.The expression of TGF β1 in alveolar and bronchi epithelial cells as well as mesenchymal were stronger on the postnatal 3rd, 7th and 14th day in hyperoxic group, the difference was significant compared with air group; While the expression of TGF β1 in alveolar macrophages could only be observed on the postnatal 14th day hyperoxic group .ConclusionHyperoxic exposure can causel lung damage: decreased surfacant and increased collagen synthesis ,which can lead to the fibrosis of the immature lung. It is possible that stronger TGF β1 expression in the lung and its expression in alveolar macrophages have relations with lung injury induced by hyperoxia.