Structure and Concentration of Elastic System Fibers in the Trachea of the Rat

Abstract

SUMMARY:The extracellular matrix is a key element in the tracheal morphology and physiology, both in normal and pathological states, yet little is known regarding its composition and organization. Herein we carried out a detailed study of the morphological organization and volumetric density of elastic system fibers in the trachea of Wistar rats. Six Wistar rats at the age of 45 days were used. The trachea was excised following anesthesia with Thiopental and perfusion through the left ventricle with buffered saline followed by formalin solution. Samples were fixed in formaline, embedded in paraffin, and histologically processed. The elastic system fibers were evaluated at light microscopy by using Weigert's resorcin-fuchsin technique after oxidation with oxone. Morphometric studies were performed by the point-counting method. Quantities were expressed (%, mean) as volumetric densities and were determined on 25 random fields for each animal. Elastic system fibers were identified beneath the tracheal mucosa showing mainly a longitudinal profile. There were also some bundles of oblique fibers in this region, forming an irregular network of elastic tissue. Close to the inner surface of the cartilaginous ring, a well defined circular layer is present. The volumetric density of the elastic system fibers in the trachea of Wistar rats is 2.46 ± 0.99%. The data in the present study provides original information regarding the elastic system fibers of the rat trachea, which might be used as a model for studying human major airway morphology. The results reported herein provide the basis for continuous investigations on tracheal extracellular matrix by stereology.

Desnutrição materna durante a lactação em ratos Wistar: efeitos sobre as fibras elásticas da matriz extracelular na traqueia dos filhotes

“…Twenty-four hours after birth, excess pups were removed in order to reduce the size of each litter (group) to six, since this procedure maximizes lactation. (5,7) At delivery, the PR diet started to be offered to the PR dam, this having been defined as lactation day 0 (D0). At 21 days of age (weaning), all pups were killed with an overdose of sodium pentobarbital (0.15 mL/100 g of body weight) in the morning and perfused through the left ventricle with PBS, followed by a formalin solution.…”

“…(7) These programs use the color properties of the elements (pixels) of an image in order to determine a threshold level for inclusion. However, in very thin linear structures, such as elastic fibers, the contrast between the structural elements (e.g., fibers) and the background is low; therefore, there is a high error rate when such programs are used.…”

“…(5) Few studies have focused on the morphology of the trachea, especially regarding its extracellular matrix and elastic fibers. (7,8) Although considerable attention has been given to the elastic properties of the lung and chest wall, there have been no studies investigating the elastic network of the major airways. (9) We consider that the lack of studies on this topic is relevant, since procedures involving the trachea and the airways are emerging and becoming more complex.…”

“…The composition of the elastic fibers in the tracheas of rats is similar to that of those in the tracheas of humans. (7) In addition, the rat is considered a good model for nutritional research. (5) Few studies have focused on the morphology of the trachea, especially regarding its extracellular matrix and elastic fibers.…”

“…(7,13) The data are expressed as mean ± SD, with the respective 95% CIs. The Mann-Whitney test was used in order to compare the results between the groups.…”