An ultrastructural study on the regeneration of blood vessels of the curetted tracheal mucosa in rat

After the respiratory tract is damaged by trauma or infection, it is repaired rapidly. The purpose of this study is to observe morphologically the regenerative process of tracheal mucosae, especially the regeneration of blood vessels in the mechanically injured tracheal mucosa of rats. The total mucosal layer of trachea was removed by curetting in 95 adult rats. Then, at several interval from one hour to ten weeks after treatment, 5 rats were killed, and their curreted area of the trachea were removed as specimen for transmission electron microscopical and scanning electron microscopical observation. For scanning electron microscopy, vascular network casts were made by the infusion of Mercox resin through the aortic arch. One hour after curetting, the injured blood vessels formed terminal blind branches. From three hours to one week after curetting, many vascular bud-like-processes appeared in venules at the floor and margin of the curetted wound. Twelve hours after curetting, new vascular network were observed in the curetted area. One week after curetting, the vascular network was consisted of capillaries, veins, and arteries. The vascular networks were almost completely rearranged at six weeks after curetting. However the irregular arrangement were still observed partially after ten weeks of curetting. The formation of terminal blind branches in vessels were noted as the initial healing process of injured vascular networks. Then many "bud-like-processes" appeared. Six weeks after curetting, the vascular networks were almost completely rearranged.