THE VASCULAR-RESPONSE IN CHRONIC PERIODONTITIS

The role of vascular endothelial cells (EC) in periodontitis was inves tigated in a series of histological studies. Expansion of the vasculat ure was found to occur with development of gingivitis and periodontiti s. This was thought to contribute to the characteristic tissue degrada tion in the developing disease. Vascular expansion could also play a r ole in the formation of a previously unreported perivascular hyaline m aterial (PHyM). Polymorphonuclear leukocytes (PMN) are known to be pro tective in periodontitis, and the location, incidence and extent of PH yM suggested a role for PHyM in periodontitis by inhibiting PMN emigra tion. PMN emigration was found to occur from specialized high EC (HEC) lined post capillary venules. This was unexpected, as such vessels ha ve previously been found to exchange lymphocytes almost exclusively. D etailed histochemical, ultrastructural and biosynthetic studies of the se specialized blood vessels led to the suggestion that HEC may be spe cially adapted for the synthesis of cytokines in periodontitis. A nega tive association between expression of the membrane bound ectoenzyme, alkaline phosphatase, and HEC suggested a role for this enzyme in leuk ocyte emigration. These observations compel re-evaluation of the role of EC in chronic inflammation, and in periodontitis in particular. The direction of current and future work is discussed.