Effect of Solute Molecular Weights on Mass Transfer within the Rat Lacunar-Canalicular System under Gravity

The lacunar-canalicular system (LCS) serves as the mechanobiological foundation for bone tissue metabolism, mechanotransduction, and functional adaptation. However, the impact of solutes with varying molecular weights on LCS mass transfer under gravity remains unclear.

Rhodamine tracers of varying molecular weights were injected into the peritoneal cavity of SD rats and LCS mass transfer experiments were performed under normal and hypergravity conditions. Femurs were extracted from rats and prepared into bone section samples, which were then observed under a laser scanning confocal microscope to analyze tracer distribution. ImageJ was used to analyze the fluorescence intensity at the lacunae, which indicated the concentration of fluorescent tracer.

Concentrations of a fluorescent tracer in the lacunae gradually decrease with increasing distance from the Haversian canal. Additionally, with the increase in solute molecular weight, concentrations of fluorescent tracers within each lacuna decrease accordingly. Hypergravity (5 g) effectively promotes the solute transfers of varying molecular weights across layers to the lacunae. Larger molecular weight solutes exhibit stronger hypergravity-driven mass transfer augmentation in the LCS.

This study uncovered the effects of solute molecular weights on mass transfer within the LCS under gravitational fields. The higher the molecular weight of the solutes within the bone, the more difficult mass transfer becomes and the more susceptible to gravity. Hypergravity significantly promotes the efficiency of solute mass transfer and ensures normal mass transfer in the LCS. These results not only provide a potential adjuvant strategy for improving bone health but also open up a novel therapeutic pathway for the management of osteoporosis.