Relationship between lactic acid concentration and osteoclast differentiation of mouse monocytes / 中国组织工程研究

ABSTRACT

BACKGROUND: Preliminary study found that polylactic acid composite material could accelerate the bone construction rate, and the underlying mechanism still needs to be studied further. OBJECTIVE: To investigate the effect of lactic acid at different concentrations on osteoclast differentiation of mononuclear cells in mice. METHODS: Mouse RAW264.7 cells were cultured in DMEM with 0 (control group), 5, 10 and 20 mmol/L lactic acid, respectively, under the induction of 50 µg/L RANKL for 5 days. The effect of lactic acid concentration on the cell proliferation rate was analyzed by cell counting kit-8 assay. Tartrate resistant acid phosphatase positive polykaryotic cells were stained and counted with tartrate resistant acid phosphatase staining kit. mRNA expression levels of acid phosphatase 5, nuclear factor of activated T-cells 1 and RANK were detected by RT-PCR. Protein expression levels of cathepsin K and nuclear factor of activated T-cells 1 were detected by western blot assay. RESULTS AND CONCLUSION: (1) 5 mmol/L lactic acid produced the highest proliferation rate of raw264.7 cells, whereas the 20 mmol/L lactic acid produced lowest cell proliferation rate. Compared with the control group, the proliferation rate of raw264.7 cells by 10 mmol/L lactic acid was insignificant. (2) Tartrate resistant acid phosphatase staining showed the highest positive rate and mRNA expression levels of acid phosphatase 5, nuclear factor of activated T-cells 1 and RANK under the condition of 10 mmol/L lactic acid. (3) With the increase of lactic acid concentration, the expression level of cathepsin K increased, while the expression level of nuclear factor of activated T-cells 1 was on a decline. (4) Under the current experimental conditions, with the increase of lactic acid concentration, the ability of lactic acid to promote the osteoclast differentiation of mouse RAW264.7 cells is firstly increased and then decreased, and 10 mmol/L lactic acid was the optimal concentration to promote the osteoclast differentiation of mouse RAW264.7 cells. Lactic acid can affect the osteoclastic differentiation of mouse raw264.7 cells by nuclear factor of activated T-cells 1 in nuclear factor-KB signaling pathway.