Expression Of CD14 And TLR4 In Experimental Pulpitis Of Rats Induced By Lipopolysaccaride

Objective: In order to observe and semiquantitative analysis the expression of CD14, TLR4 at different periods and regions in rats' dental pulp, we established animal model of pulpitis with rats induced by lipopolysaccharide and used immunohistochemistry methods to investigate the role of CD14, TLR4 in pulpitis and provide the experimental evidence of animal for elucidating the pathogenesis of pulpitis which was caused by LPS.Methods: 56 female Sprague-Dawley (SD) rats, 24 weeks old, were randomly divided into 7groups of 8 rats each: one group was normal, other were pulpitis. In groups of pulpitis, First molars in upper jaw of each rat were divided into experimental and control groups. When pulpal tissues were exposured, experimental sides were dealt with LPS as control sides were dealt with NS. The rate were sacrificed at 1, 3, 7days, 2, 3, 4weeks by perfusing 4% paraformaldehyde into heart. The first molars combined with some jaw bones of each rat were fixed, decalcified, embedded in paraffin, and sectioned serially. The sections were stained with hematoxylin-eosin to observe the histopathological changes of pulps. Immunohistochemical staining was used to observe the expression of CD 14 and TLR4. Image pro plus 5 image analysis software was used to determine the average gray value of CD14 and TLR4 positive cells in rat pulpal tissues. Statistical tests were performed by one-way analysis of variance (ONE-way ANOVA), SNK-q test and t test.Results:1. The pulpal tissues survived long more than four weeks in LPS experimental groups. The whole process of the pulpal tissues hurt by LPS and their immunity defence and self-reparation was observed.2. Positive staining for CD14 was not found in any other layer cells of healthy pulp, except some cells in the odontoblast layer. Strong positive staining for CD14 was observed in inflammatory areas (mainly for monocytes/macrophages and neutrophils). Image analysis of CD14 indicated that the difference between normal group and each inflammatory group dealt with LPS had statistical meaning; there were statistical difference among the inflammatory groups, except the difference between three-week group and four-week group; compared LPS-group with NS-group, there were statistical difference in three-day group and seven-day group, no statistical difference in one-day group.3. Positive staining for TLR4 was mainly found in vascular endothelial cells, odontoblasts and inflammatory cells. Statistical results of image analysis of TLR4 was indicated as following: there were statistical difference between normal group and other inflammatory groups deal with LPS except two-week inflammatory group; compared each inflammatory group deal with LPS, except the difference between one-day group and three-day group, other groups shown the statistical difference; compared LPS-group with NS-group, there were statistical difference in every time-group and average gray value of LPS-group was lower than NS-group's in the same period.Conclusions:1. Experimental model of rats' pulpitis induced by lipopolysaccharide was the valid and credible animal model for studying the machanism of LPS hurting pulpal tissues.2. It was indicated that CD14 and TLR4 participated in the process of dental pulpitis and played an important role in the pulpitis. 3. LPS can up-regulate the expression of CD14 and TLR4.