Chitosan monomer accelerates alkaline phosphatase activity on human osteoblastic cells under hypofunctional conditions

Chitosan is a natural polyaminosaccharide that is extensively applied as an antitumor and antirheumatic drug. However, there are few reports about its effects on hypofunctional osteoblasts in vitro. We investigated the biological characteristics of a human osteoblastic cell line (NOS-1 cells) that was cultured with a chitosan monomer-containing medium under simulated microgravity conditions. After 7 days of cell incubation under the conventional conditions, the flasks were transferred to a microgravity simulator for 3 days. In the 0.005% chitosan monomer supplemented group, the marker enzyme of biological mineralization, the alkaline phosphatase (ALP) activity, was significantly higher compared with the control group (p < 0.05). A cDNA microarray was performed to investigate the effects on the mRNA level by chitosan monomer, and the fluorescent signal was analyzed. The interferon gamma (IFN-γ) receptor gene was detected with a signal ration of 2.2. The slight increase of IFN-γ receptor expression was confirmed after 3 days of incubation according to RT-PCR analysis. Western blot analysis also showed the increased expression of IFN-γ receptor. These results suggest that a supra-low concentration of chitosan monomer may increase the ALP activity of osteoblastic cells through the IFN-γ receptor at the early phase of cell culture and recover the activity for biological mineralization under the hypofunctional condition.