The discovery of lymphatic stomata and its ultrastructure in mouse tunica vaginalis.

The communicating hydrocele is caused by the failure of the processus vaginalis closure. After the patent processus vaginalis is closed, the hydrocele can subside spontaneously, but the mechanism responsible for the drainage of hydrocele has not been expounded. Former studies showed that lymphatic stomata between the mesothelial cells lining the peritoneum and pleura were responsible for the drainage of ascites and pleural effusion. Although the tunica vaginalis is also lined by mesothelial cells, the existence of lymphatic stomata in it has never been reported. Therefore, we investigated the presence and ultrastructure of lymphatic stomata in mouse tunica vaginalis.We studied the ultrastructure of mouse tunica vaginalis by scanning and transmission electron microscopy. The submesothelial connective tissue with foramina were investigated after the mesothelial cells were digested by NaOH solution. Typan blue was used as a tracer to show the absorptive function of lymphatic stomata.The lymphatic stomata were found between the mesothelial cells. The trypan blue was directly absorbed by the lymphatic stomata. Milky spots which possessed immune function were observed, and the lymphatic stomata were found within the milky spots.Our study is the first to report the presence and ultrastructure of lymphatic stomata in mouse tunica vaginalis. They might be related to the lymphatic drainage in the tunica vaginalis cavity.