OBJECTIVETo investigate the autophagy in human bone marrow mesenchymal stem cells (hBMMSC) exposed to irradiation.

METHODSThe apoptosis and necrosis rate were assessed by Annexin V and propidium (PI) staining in hBMMSC at 4h after irradiated with X-ray at 0, 2, 4, 8 and 10 Gy. The autophagy was observed by transmission electron microscopy. The mRNA expression of Beclin1 and microtubule-associated protein 1 light chain 3 (MAPLC3 or LC3) was analyzed by RT-PCR in hBMMSC at 4h after X-ray irradiation at 0, 8 and 10 Gy.

RESULTSThe apoptosis rate of hBMMSC was markedly decreased while the necrosis and death rate were slowly increased with the increase of irradiation dose when under 8 Gy. The apoptosis rate was significantly increased and reached a peak while the necrosis and whole death rate were obviously increased when irradiated with 10 Gy X-rays. In addition, the change of apoptosis rate was more significant than that of necrosis rate. By electron microscopy, a mass of autophagic vacuoles (autophagosome and autolysosome) were observed in irradiation and positive control groups, but were only occasionally seen in normal control group. The proportion of hBMMSC with autophagic vacuoles in 8 Gy irradiation group was higher than that in 10 Gy one. The mRNA expression of Beclin1 and LC3 in irradiation groups and positive control group was significantly higher than in normal control group, and so did in 8 Gy irradiation group than that in 10 Gy group.

CONCLUSIONIrradiation may induce the autophagy in hBMMSC, and autophagy could protect hBMMSC from irradiation injury in a certain dose range.