The cell proliferative activity of parodontal tissues in aging mice

Abstract

One hundred and thirty-eight short-lived mice of the Brookhaven National Laboratory inbred strain of Swiss albino 5, 26, 52, 78 weeks of age were used to determine the normal proliferative activity of the parodontal tissues comprising the mesial aspects of the maxillary 1st molars and the associated changes concomitant with aging. Labelling indices were obtained following grain-counting of autoradiographs. Each animal received 1 μCi of tritiated thymidine per gram body weight 1 hr prior to death. Five micron sections were cut from paraffin blocks prepared routinely following EDTA decalcification. Results showed that the order of proliferative activity was similar at all ages. The proliferative activity was highest in gingival epithelium while all other tissue compartments were significantly lower. In lessening order, these were 4 connective tissue compartments, 2 osteogenic layers and lastly the cementoblastic layer. A progressive decrease in labelling indices to 52 weeks of age was generally observed with increasing age. This was subsequently followed by a rise in the number of labelled cells, especially in the gingival epithelium and connective tissue below the crevicular region. A survey of the tissues for inflammatory reactions revealed increased incidence with advancing age, especially at 78 weeks of age. The crevicular region of the epithelium, the connective tissue below and the periapical periodontium were the usual inflammatory sites. It was concluded that increased labelling observed in animals older than 52 weeks of age was associated with increased incidence of inflammation at susceptible sites coincidental with histological age changes in parodontal tissues.