Abstract: OBJECTIVE To observe the protective effect of human umbilical cord mesenchymal stem cells (hUCMSCs) on apoptosis of A549 cells of patients with infections.METHODS The hUCMSCs specimens were collected from fetal umbilical cord and decidua tissues under aseptic condition, the A549 cells were inoculated with Pseudomonas aeruginosa so as to establish A549 cell damage model, and the impact of P.aeruginosa on the apoptosis of the A549 cells and the protective effect of hUCMSCs on the apoptosis were observed.RESULTS The P.aeruginosa infection resulted in the slow growth, aging and vacuolation of the A549 cells, the expression of SP-A in the A549 cells was reduced under the infection state, as compared with the A549 cells that were not infected, there was significant difference ( t=7.745,P=0.001). The expression of SP-A in the A549 cells was up-regulated after the inoculation of hUCMSCs, as compared with infection group, there was significant difference ( t=3.872,P=0.017).The rate of apoptosis of the A549 cells accelerated after the P.aeruginosa infection, and the survival rate was reduced; the rate of apoptosis of the A549 cells was reduced after the inoculation of hUCMSCs, and the survival rate was up-regulated.CONCLUSION The inoculation of hUCMSCs may repair the damage of the A549 cells infected with P.aeruginosa infection and inhibit the apoptosis.