The Mass Transfer Within the Lacunar-canalicular System of Rats Under Simulated Microgravity

Abstract

Microgravity causes disuse osteoporosis in astronauts, lacking effective treatments. The mass transfer within the lacunar-canalicular system (LCS), essential for maintaining bone balance, makes studying molecular Weight solute transfer in LCS under microgravity vital for clinical solutions. In this study, a tail-suspended rat model was used to simulate microgravity on Earth. Rats were injected with fluorescent tracers of three molecular weights as the transport Mass, and the gray values of osteocytes at lacunae were detected in LCS by laser scanning confocal microscopy to represent the concentration of fluorescent tracers. Under microgravity, the gray values in lacunae farther from the Haversian canal were lower, with this trend observed in all molecular Weight fluorescent tracers. As gravity decreased, gray values in the lacunae also declined, with the most significant reductions seen in lacunae farther from the Haversian canal. For fluorescent tracers of 479 Da, 20 kDa and 150 kDa, gray values in deep lacunae decreased by 16.532%, 18.181% and 34.688%, respectively. The larger the molecular weight of the fluorescent tracers, the greater the decrease in gray values of osteocytes in all layers surrounding the Haversian canal, especially in deeper lacunae. Larger molecules face more difficulty penetrating the LCS and reaching deeper lacunae, with microgravity having a more significant effect on these molecules. Microgravity impairs mass transfer within the LCS, particularly reducing the delivery of essential components to deeper lacunae, which may lead to bone loss and induce osteoporosis. This study offers new insights for the clinical treatment of microgravity-induced osteoporosis.