T. Takata et al., REACTIVE CHANGE IN PROLIFERATIVE ACTIVITY OF THE JUNCTIONAL EPITHELIUM AFTER TOPICAL APPLICATION OF LIPOPOLYSACCHARIDE, Journal of periodontology, 68(6), 1997, pp. 531-535
IT IS WELL ESTABLISHED THAT apical migration of junctional epithelium
(JE) along a root surface is an important factor in periodontal pocket
formation and deepening. However, the exact mechanism and, more speci
fically, the role of inflammatory products in influencing the activity
of cells within the JE is not known. To address this issue lipopolysa
ccharide (LPS) was applied topically into rat molar gingival sulcus an
d then tissues evaluated immunohistochemically for expression of proli
ferating cell nuclear antigen (PCNA). Tissues were prepared for histol
ogical analysis at designated times. Histologically, infiltration of n
eutrophils with associated edema was noted in JE and gingival connecti
ve tissues 6 hours after LPS application and was prominent at 12 hours
. These inflammatory changes persisted in the 2- and 3-day specimens,
and disappeared at 5 days. In normal gingiva, before the LPS applicati
on, the JE showed few PCNA positive cells, while almost all cells in t
he basal and suprabasal cell layers of the oral gingival epithelium an
d the oral sulcular epithelium were PCNA positive. No increase in the
number of PCNA positive cells in the JE beyond zero time was observed
at 6 and 12 hours after LPS application. One day after LPS application
, PCNA positive cells appeared in the basal cell layer of the JE, with
a continued increase number of PCNA positive cells in the JE continue
d at 2 and 3 days. By day 5 the number of PCNA positive cells were dec
reasing with a return to a normal range by 7 days. These results showe
d that 1) under normal physiological conditions, cells within the JE h
ave minimal mitotic activity and 2) the JE cells can enter the prolife
rating cell cycle when exposed to LPS, and suggest that the enhanced p
roliferating activity in the JE is an important factor for the deepeni
ng of the periodontal pocket, if the connective tissue attachment is b
roken down.