Abstract:

Mesenchymal stem cells (MSCs) in bone marrow form a niche that has inevitable interactions with neutrophils. Moreover, previous documents have shown that calcitriol has an important role in regulating the cell growth of MSCs. This study set out to investigate the effects of calcitriol on the interaction between bone-marrow-derived MSCs and neutrophils. MSCs were isolated from the bone marrow of rats and pulsed with different concentrations of calcitriol (50, 100, and 200 nM) for different periods of time (24, 48, and 72 h). As the next step, the supernatants of MSCs cocultured with neutrophils for 4 h and neutrophil functions were evaluated. The results showed that the supernatants of MSCs treated with calcitriol could significantly increase the phagocytosis of Staphylococcus aureus by neutrophils and, conversely, decrease the respiratory burst intensity of neutrophils. Moreover, treatment of MSCs with calcitriol can cause a significant decrease in the percentage of neutrophil apoptosis. These findings were concurrent with a significant increase in IL-6 levels in the supernatant of calcitriol-treated MSCs. Consequently, the supernatant of bone-marrow-derived MSCs was pulsed with calcitriol, and the exertion of a protective role against potentially harmful reactive oxygen species production preserved phagocytosis and the survival rate of neutrophils.

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