Influence of Inflammation to Lymphangiogenesis in Human Dental Pulp

Abstract

Summary During inflammation, lymphangiogenesis takes place to enhance the transport of filtered fluid, proteins, and immune cells. Dental pulp tissue is frequently exposed to inflammatory insults, but the lymphatic system of the pulp and its responses to injury have not been investigated in detail using specific lymphatic markers. The aim of this study was to evaluate and to compare the lymphatic system in health dental pulp and pulp with inflammation, and to establish whether lymphangiogenesis takes place during dental pulp inflammation. Ten pulps with irreversibile pulpitis and eleven samples of healthy dental pulps were included in this study. All pulp samples were analyzed microscopically using the standard hematoxylin-eosin (HE) staining to detect the presence of inflammation. Immunohistochemical staining was performed using monoclonal anti-CD31 antibody (DAKO) at dilution 1:20. Microvessels identified by CD31, in which lumen the red blood cells were not detected, were considered as lymph vessels. Active areas of lymphangiogenesis (“hot spots”) were selected using low magnification. Images from five high power fields in the hot spot areas were recorded for each sample. Lymph vessels were counted using ImageJ program. The total number of lymph vessels so obtained was then divided by the number of the counted hot spots, and the result was used to denote the lymph vessel density. The mean number of lymphatic vessels, detected by CD31, in the group without inflammation was significantly lower than in the group with inflammation (3.75 versus 13.58, t=7.093, p<0.001). The present study established an increased number of lymphatic vessels in the inflamed human dental pulp suggesting that inflammation contributes to lymphangiogenesis.

Review on the Lymphatic Vessels in the Dental Pulp

“…Lymphatic endothelial cell differentiation is also influenced by, i.a., VEGF-C, VEGF-D, angiopoietin-2, transmembrane ligand—ephrin-B2, neuropilin-2 receptor protein and transmembrane glycoprotein—podoplanin. At the inflammatory site, lymphangiogenesis is regulated by the same factors that affect lymphatic vessel development in terms of individual development [ 57 , 93 ].…”