Expression And Significance Of Clara Cells In Fetal Lung And Injury Lung

ObjectivesTo observe the expression of Clara cells in fetal lungs, and to discuss its biologicalsignificance for developing of lung. To construct the experimental animal model of n-hexaneinhalation, which acute injury in SD rat and chronic injury in Kunming mouse for n-hexanetoxicity research. To detect the expression of Clara cells and its interrelated factors in injurylungs, and discuss the functions of Clara cell in injury lung induced by n-hexane.MethodsKunming mouse model of n-hexane long-term inhalation: 24 healthy mice wererandomly divided into 4 groups: one control group and three n-hexane groups(4w, 8w and12w). Primary concentration of n-hexane was 17.6g/m~3, 8 hours per day. SD rat model ofacute n-hexane inhalation was repeated according to the former experiment. The averagen-hexane concentration of blood was detected. The lungs, livers and kidneys were taken outsoon after the mice were killed. 12 specimens of human fetal lung (16th week～30th week)were obtained. Paraffin specimen and HE staining in the routine, and were observed undermicroscope. VG staining was applied to show collagen fibrosis.The expression of CCSP, Lysozyme, TGF-βand CGRP in fetal lungs and injury lungswere examined using immunohistochemistry of S-P methodResults1. In the poisoning groups, the average n-hexane concentrations of blood were highermarkedly than that of the control group. There were apparent pathologic damages inlungs, livers and kidneys of the poisoning mice. It was suggested that the experimentalmodel ofn-hexane long-term inhalation was successful.2. In fetal lung of the 20th week, positive reaction of CCSP cells was firstly showed inbronchiole. The quantity of CCSP cells increased during the developing of lung, andgradually reached to adult level at the 30th week. At the 16th week, positive reaction ofCGRP was primarily detected also in the bronchiole, the amount of CGRP cell reached its peak at the 25thweek, and then gradually decreased. It was suggested that there was tightrelationship between Clara cells and PNECs during development of lung.3. Both in acute and chronic poisoning groups, with prolong of the poisoning time, CCSPreaction in Clara cells was markedly decreased but the macrophage cells with Lysozymereaction gradually increased. At the same time, PNECs with CGRP reaction evidentlyincreased and some NEB were observed in acute-poisoning groups. Otherwise, positivereaction region of TGF-βmagnified gently, and collagen fibers increased gradually ininjury lungs by VG staining.Conclusions1. With the acute and chronic experimental model of n-hexane inhalation, it was showed thatn-hexane induced pathologic damages of the organs (lung, liver, kidney, etc.). It wassuggested that two models were feasible and repeatability, and were likely to providereferenced models for n-hexane toxicity research.2. The development process of Clara cells in fetal lung was gradually and complicated. Inthe early phase, Clara cells were immature. The matured Clara cell could synthesize andsecrete not only CCSP but also SP (surfactant protein). On the other hand, there was tightrelationship between Clara cells and PNECs. It was suggested that the cooperation ofClara cells and PNECs played an important role during the development of lung.3. In injury lungs after n-hexane inhalation, Clara cell was the target cell of n-hexane toxicityeffect. Clara cells played an extensive protective role in lung injury. Clara cells could bedestroyed in n-hexane inhalation, whereafter to decrease the content of CCSP. At thesame time, pulmonary fibrosis maybe befallened often.