| Chronic obstructive pulmonary disease (COPD) is a respiratory condition characterized by progressive decline in lung function, usual-ly as a response to inhalation of noxious substances such as tobacco smoke. COPD is also a leading cause of mortality globally. Emphyse-ma is characterized by airway destruction distal to the terminal bron-chioles , gradual loss of lung recoil, decreased alveolar surface area, and impaired gas exchange. Lung Transplantation and Lung Volume Reduction Surgery provide it only remediation. Vitamin A ( or retinol) and its active derivative retinoic acid ( RA) play a multiple role in lung development and function. Retinoic acid treatment abrogates elastase - induced pulmonary emphysema in rats has been reported by Massaro in 1997. In order to make sure if there are some intervenient effects of RA and vitamin A on the development of experimental em-physema in rats and to study their effective mechanism, experimental emphysema model were made by instilling elastase into rat lungs.METHODS AND MATERIALSAnimals.Twenty-eight male Wistar rats, 12 weeks old, the body weight is (274 ?23 ) g, purchased from the animal center of China Medical University, were divided into four groups, the normal group( A), themodel group(B) , the RA group(C) and the vitamin A group(D) , seven rats in each group.Method Rats were anesthetized with ketamine ( ~75rag/kg) , op-erating to expose the trachea. We instilled elastase (2. Ou/g body mass ) , into rat lungs of Group B, C, D, or an equal volume of saline into rat lungs of Group A. From the second day of instilling elastase rats of group C and D were treated by all - trans - retinoic acid (500μg/kg body mass, once a day) or vitamin A (50000u/kg body mass, once a day) via intraperitoneal injections and esophagus, re-spectively. Twenty - five days late, all rats were killed.Fixation, Tissue sampling, and Tissue preparationThe rats were anesthetized, then were killed by cutting the ab-dominal aorta. Cold 10% neutral formalin was infused into the trachea at a transpulmonary pressure of 1.96 Kpa H20 for 3Ominates. The tra-chea was ligated, lungs were removed from the thorax, and fixation was continued for 24h. Lungs were cut into blocks; The alveolar lin-ing cellscan was stained using standard histochemical dies ( hematoxy-lin - eosin) , so therefore, alveoli can be differentiated clearly from surrounding tissue when the image is converted to a gray scale. Some of the blocks were stained by immunohistochemical ( proliferating cell nuclear antigen [PCNA] ) method to identify proliferating cells.Image analysisWe use computer - assisted image analysis system, MetaMorth/ DP10 system, Meta Morth Imager System V4. 6 software to analyze the changes in alveolar area and density. Two blocks of each rat were ana-lyzed. Eight fields of each block were taken randomly, not include bronchioles and large blood vessel. MAA ( mean alveolar area) : counting the number of alveolar in each field of vision (Na) , measur-ing the area of it(TA) , and the area of positive stain area (PA) , then getting the MAA = (TA - PA)/Na.MLJ(mean linear intercept) : scoring a cross through the center of each field of vision, counting the number of the point that across the cross of the linear intercept ( Ns ) , measuring the length of the cross ( L) , then getting the MLI = L/Ns.Index of PCNA: The number of positive nuclear of the alveolar that been stained by PCNA. Counting the number of the blue nuclear of each field ( Nl ) , the number of the positive nuclear ( N2 ) , then getting the index of PCNA = N2/(Nl + N2)of each field, calculating the means of them, then getting the index of each block.Statistical methodsValues were expressed as means ?s, Two - tailed unpaired t -test were used to analyze the data. A value of p <0.05 was considered as the level of significance.Results1. Histopathological featuresObserved in the gross, the volume of lungs in emphysema model group were bigger than those in normal group and RA group, color be-... |
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