In light microscopic examination, all cyst specimens revealed the typical morphology of a radicular cyst. The cyst lumen was partially or entirely lined by nonkeratinized stratified squamous epithelium. The underlying fibrous connective tissue wall was inflamed with variable degrees of inflammatory cell infiltration. Many small blood vessels were scattered within the cystic connective wall, especially concentrated in the regions with an inflammatory infiltrate. The infiltrate consisted mainly of macrophages which were labelled with a- ACT(Fi g.1).
As shown in Fig. 2, COX-2 stain was detected in the lining epithelium and subepithelial fibroblasts, macrophages and endothelial cells in all specimens. COX-2 expression was also noted in the endothelial cells of some small capillaries in the fibrous connective tissue wall with a marked inflammatory cell infiltrate (Fig. 2).No signals were detected in the negative controls of radicular cysts. In addition, COX-2 expression in a gingiva specimen represented with higher levels of inflammation (Fig. 3).
COX-2 expression in radicular cysts with low or high levels of inflammation is listed in Table 1. Differences in COX-2 expression between tissues with low and high levels of inflammation were subsequently analyzed using Fisherâ€™s exact test. A significantly greater COX-2 expression was noted in radicular cysts with high levels of inflammation as compared to the tissues with low levels of inflammatory cell infiltrates (P = 0.0052).
Figure 1. Photograph showing macrophages labelled by a-ACT in both the lining epithelium and underlying inflamed connective tissue wall of a radicular cyst (400x).
Figure 2. Immunolocalization of COX-2 in a radicular cyst. COX-2 stain was detected in the lining epithelium and subepithelial fibroblasts, macrophages and endothelial cells in only one specimen is shown (200x).
Figure 3. Inflamed gingival tissues were used as positive control. COX-2 expression was significantly higher in a gingival specimen with higher levels of inflammatory infiltrates (200x).
Table 1. The results of COX-2 expression and the grade of inflammation in radicular cysts analyzed in this study.