Abstract
The in vitro life-span of human periodontal ligament fibroblasts (PDLF) was studied on clones from periodontium of teeth extracted due to periodontitis and dental caries (69 clones/192 individuals, aged 20-80 years) and from periodontium of teeth extracted for orthodontic reasons (23 clones/26 individuals, aged 15-19 years). In the primary cultures the ratio of the number of cells expressing senescence-associated beta-galactosidase (SA-beta-Gal) to the total number of cells is significantly larger in PDLF (92 clones; 11.1+/-4.9%) than in human gingival fibroblasts (GF) (10 clones; 0.5+/-0.1 %). The finite population doubling numbers (PD) of PDLF are not age-matched and the mean PD of PDLF (7.1+/-2.9) is significantly smaller than GF (28.5+/-3.2), IMR-90 (human lung fibroblasts, 5 clones; 44.3 +/- 2.2), and human osteoblasts (5 clones; 19.7+/-1.4). Comparing the ratio of the number of SA-beta-Gal positive cells to the total number of cells in primary culture, and the finite PD in PDLF cultures: 1) the ratio of 15-19 years old donor group is significantly smaller than in the other donor groups (20-29, 30-39, 40-49, 50-59 and 60-80 years old), and 2) there were no statistically significant differences among the 20-29, 30-39, 40-49 and 50-59 year old donor groups, and the 30-39, 40-49, 50-59 and 60-80 year old donor groups. These findings suggest that the in vitro life-span of PDLF is shorter than other fibroblasts in the connective tissues and that PDLF may undergo senescence in adult clones without relation to donor's age. There may be more aged fibroblasts in periodontium than in other tissues, such as gingiva and lung.