Study On Lacunar-canalicular System Mass Transfer In Overweight Environment

Bone is the main part to support the body and ensure movement,which has always played a crucial role in our body.The ground experiment of bone health shows that proper force stimulation could maintain normal bone mass.But in space,whether it is physical exercise,drug therapy,or the combination of the two,can not completely eliminate the occurrence of osteoporosis.We believe that the reason for this is the lack of bone mass transfer under microgravity,which leads to osteoporosis.Because bone cells are embedded in mineralized matrix,they can not receive blood supply,so they can only rely on the material transport in the tissue to obtain nutrients,excrete waste,and transmit chemical signals with adjacent cells.In microgravity,the mass transfer can not reach the deep bone cells,leading to apoptosis.Because it is difficult to simulate microgravity in space on the ground,this paper studies the mass transfer of bone lacuna and bone tubule from the overweight environment,so as to explore the important reason of osteoporosis caused by the lack of mass transfer of bone under microgravity,and provide the basis for the follow-up of China’s aerospace industry to fight against osteoporosis.This paper is divided into three parts.The first part is to apply the speed of solute mass transfer and transport in constant gravity and overweight environment.The femur of sheep was cut into 3 mm × 3 mm × 10 mm small rectangular bone blocks.After the bone blocks were divided into groups,under the conditions of overweight and constant weight at different times,the situation of dye entering into the rectangular bone blocks was observed,and then the bone mass transfer situation under different gravity environment was judged.The results showed that the rate of the dye invading the bone mass in vitro was in accordance with the logarithmic function,that is,at the beginning,the infection speed was faster,and with the increase of the infection time,the infection speed gradually slowed down.In the high-G(10 G)environment,the average infection speed of staining agent was 1.4 times of that in the constant gravity(1G)environment,and the experimental data showed that the infection speed and bone mass had no direct relationship with the direction of centrifugal force.The second part is the quantitative study of mass transfer in the lacunar canalicular system(LCS)under different gravity conditions.The fluorescence tracer(sodium fluorescein,376Da)was injected into SD rats.The rats were placed in different gravity conditions and entered the bone through blood circulation.The fluorescence images of bone lacuna in the bone were taken by confocal fluorescence microscope and analyzed by Image-J,so as to explore the mass transfer of LCS in different gravity environment.The results showed that the fluorescence intensity of LCS in bone decreased about 45% at 25 μ m of Haversian tube under constant gravity and 75% after 40 μ m,while the fluorescence intensity of LCS in bone decreased about 10% at 25 μ m of Haversian tube under overweight(10g)environment,while the fluorescence intensity remained at a high level after 40 μ m,and the decrease rate was only 25%.It is suggested that gravity is an important factor affecting solute transport in bone.The third part is to use COMSOL multiphysics software to establish the model of lacuna canaliculus system(LCS)in bone tissue,and simulate the transport of nutrients required by bone cell metabolism in LCS with blood flow in microgravity(0 G),constant gravity(1 G)and high G(10 G)environment.The simulation results show that in LCS,the velocity of bone cells in the distal part of Haversian tube is very small,which is 12 orders of magnitude lower than that of Haversian tube.In the case of high G(10 G),the velocity of the distal bone lacuna is 5.3% higher than that of no gravity and 3.2% higher than that of normal gravity,which indicates that gravity can accelerate the velocity of the fluid in the distal bone lacuna.The simulation results show that in microgravity environment,the velocity of bone cells in the distal part of Haversian tube is very small.The pressure of lacunar was uniform,but in normal and overweight condition,the lacunar in LCS was low and high gradient.As a mechanical sensor,bone cells lack the stimulation of pressure,which leads to the loss of nutrients.Therefore,gravity is indeed an important factor affecting the mass transfer in bone.In a word,through the above three experiments to explore the influence of gravity on solute transport in bone,in order to explore the important factors of osteoporosis under microgravity,and provide important basis for the occurrence of aviation industry and the prevention of osteoporosis in the future.