September 1997, Volume 3, Issue 3, Pages 162 – 166

Paper

Comparison of in vitro proliferative capacity of human periodontal ligament cells in juvenile and aged donors F Nishimura1, VP Terranova2,3, M Braithwaite2,3, R Orman2, H Ohyama1, J Mineshiba1, HH Chou1, S Takashiba1 & Y Murayama1 1Department of Periodontology and Endodontology, Okayama University Dental School, 2-5-1 Shikata-cho, Okayama, 700 Japan     2Laboratory of Tumor Biology and Connective Tissue Research, Columbia University School of Dental and Oral Surgery, 630 W 168th Street, New York, NY, 10032, USA     3Current address: VA Hospital, Research Service, Hines, IL, 60141, USA

Keywords

periodontal ligament cells;   aging;   cell cycle;   cellular senescence;   AP-1

Abstract

OBJECTIVE: The aim of this study is to compare the in vitro proliferative capacity of periodontal ligament (PDL) cells from aged and juvenile donors. MATERIALS AND METHODS: Flow-cytometric analysis of the cell cycle was used to compare the length of each cell cycle, and the ratio of the cells progressing through the cycles between four PDL cells from juvenile donors and four cells from aged donors. Then, replicative capacity of the PDL cells from three juvenile and three aged donors was compared by serial cultures. Finally, expression of c-fos was compared between cells proliferating and cells which had reached senescent. RESULTS: Flow-cytometric analysis of the cell cycle had revealed that although there were no differences in the length of each phase of the cell cycle, significant differences were found in the ratio of the cells entering from Gap 1 to DNA synthesis phase of the cell cycle (P < 0.025). Replicative capacity was much longer in two cells from juvenile donors (about 20 population doublings), while all cells from aged donors showed short dividing abilities (less than eight population doublings), hence entered senescent phases shortly. Additionally, no c-fos was detected in cells which had reached senescence upon stimulation with serum. CONCLUSIONS: It is generally believed that aged humans have an impaired wound healing ability. We believe that more fibrotic PDL tissues seen in aged humans might be the reason for this, and suggest that this phenomena might be due to the progressive accumulation of senescent cell populations.

Received 9 January 1997; Revised 6 May 1997; Accepted 2 June 1997

^© Macmillan Publishers Ltd 1997