The induction of cellular senescence in dental follicle cells inhibits the osteogenic differentiation

Abstract

Dental stem cells such as human dental follicle cells (DFCs) have opened new promising treatment alternatives for today's dental health issues such as periodontal tissue regeneration. However, cellular senescence represents a restricting factor to cultured stem cells, resulting in limited lifespan and reduced cell differentiation potential. Therefore, this study evaluated if and how DFCs exhibit features of cellular senescence after being expanded in cell culture. The cell proliferation of DFCs decreased, while the cell size increased during prolonged cell culture. Moreover, DFCs expressed the senescence-associated β-galactosidase after a prolonged cell culture. The onset of senescence inhibited both the induction of osteoblast markers RUNX2 and osteopontin and the biomineralization of DFCs after stimulation of the osteogenic differentiation. In conclusion, we showed that a prolonged cell culture induces cellular senescence and inhibits the osteogenic differentiation in DFCs.

Short telomeres correlate with a strong induction of cellular senescence in human dental follicle cells

“…It is already known that human DFCs are senescent in long-term cultures and that at the same time the osteogenic differentiation potential is impaired after the induction of cellular senescence [7]. We showed in a previous study that the cell cycle inhibitor protein P16 sustains the induction of cellular senescence [8], but little is known about the relationship between genomic DNA changes and the induction of cellular senescence in DFCs.…”

“…Human DFCs were obtained from ALL Cells. DFCs were cultivated in DMEM (Dulbecco’s Modified Eagle Medium, Sigma), supplemented with 10% fetal bovine serum (Sigma) and Penicillin/Streptomycin (Sigma) as described previously [7]. Medium exchange was done twice a week.…”

“…DFC cell lines are senescent at different rates and our earlier work found a cell line that became more senescent compared to other DFC cell lines (DFC_F) [7, 8, 15]. We therefore hypothesized that for the greater induction of senescence telomeres of DFC_F are shorter and that genomic DNA changes occurs more often in DFC_F.…”

“…Improved cell culture strategies are required to suppress the induction of senescence, but part of the problem is that senescence can be induced in various ways. Although little is known about these molecular processes in DFCs, previous studies have already shown that senescence of DFCs, which can be induced in long term cultures, is regulated by the expression of P16 [7, 8]. A number of studies have shown that telomere length and the response to DNA damage are responsible for the induction of cellular senescence [9–13].…”

“…A number of studies have shown that telomere length and the response to DNA damage are responsible for the induction of cellular senescence [9–13]. The telomere length shortening has probably only little influence on the induction of senescence in DFCs, since telomere length does not decrease or only slightly decreases in senescent DFCs [7, 8]. However, Alaires and colleagues showed that short telomeres of primary dental pulp stem cells (DPSCs) accelerate senscence induction of dental stem cells [14].…”