The effect of different gravity fields on mass transfer in the rat bone lacunar-canalicular system

The bone lacunar-canalicular system (LCS) is an important microscopic infrastructure for signaling and solute transport in bone tissue, which guarantees normal physiological processes of the tissue, but the mass transfer laws in the LCS under different gravity fields have not yet been clarified. SD rats were injected intraperitoneally with different concentrations of sodium fluorescein tracer and subjected to mass transfer experiments in the LCS under normal gravity and hypergravity. The fluorescence distribution in the osteon was observed using laser scanning confocal microscopy. The hypergravity environment was provided by a self-designed high-G loading centrifuge. The fluorescence intensity of the Haversian canal in the osteon was the highest. The fluorescence intensity of lacunae farther away from the Haversian canal was lower, and the fitted curve was parabolic. With the increasing distance from the Haversian canal, the curve first rapidly decreased, and then the decreasing trend gradually became slower. Hypergravity promoted mass transfer in the LCS, and the 10 ​G hypergravity showed varying degrees of fluorescence intensity in each layer of the osteon relative to normal gravity, with intensity enhancements in the range of 132.7–249.0%. The fluorescence intensity was also significantly increased when the tracer concentration was halved and the gravity field magnitude was increased to 10G. In conclusion, hypergravity promoted the transport of solute molecules, nutrients, and signaling molecules within the LCS. The effect of hypergravity on mass transfer in the LCS was greater than that of tracer concentration. This may help to understand bone diseases from a mass transfer perspective.