Increased autophagic activity in senescent human dental pulp cells

To establish whether autophagy is involved in dental pulp cell (DPC) senescence, so as to better understand the mechanism of the ageing process within the dental pulp.

Human DPCs obtained from intact molars and premolars were cultured and serially passaged. Senescence-β-galactosidase (SA-β-gal) staining was performed to assess DPC senescence, which is considered to be the senescence of cells in culture after a series of passages. Autophagic activity was analysed by Western blot for major autophagic proteins and transmission electron microscopy (TEM) for autophagic vacuoles in both young and senescent cells. Statistical analyses were performed using the Student's t-test.

Senescence-β-galactosidase staining was higher in senescent DPC than in young cells (P = 0.011). Western blot revealed senescent DPCs had greater expression of autophagic proteins (microtubule-associated protein light chain 3 and Beclin 1) than young cells (P = 0.04, P = 0.001). Transmission electron microscopy revealed more autophagic vacuoles in senescent DPCs compared to young cells (P = 0.029).

Expression of autophagic proteins (microtubule-associated protein light chain 3 and Beclin 1) increased in senescent DPCs compare to young cells. More autophagic vacuoles were observed in senescent DPCs by TEM. Collectively, these data imply that autophagic activity increased in senescent DPCs.