Journal of Bone Research and Reports

Description

The long-term flight of astronauts in the microgravity environment of space severely decreased bone mineral density, lost bone mineral, and degenerated bone microstructure as human space exploration increased, resulting in astronauts' weightless bone loss, particularly of the weight-bearing bone. Eight astronauts on the International Space Station had their bone mass measured, and seven of them had lower lumbar vertebrae bone mineral density, while all eight astronauts had lower femoral bone density. According to a number of studies, microgravity caused a BMD decrease of approximately 2% in just one month, which was comparable to that of a postmenopausal woman after one year on Earth. For astronauts, bone loss is now one of the highest risk factors and the greatest obstacle to long-term space stay and planet exploration. This increases the risk of fractures and further contributes to serious health issues. Drug intervention, strengthening exercises, and nutrition are just a few of the countermeasures that can be implemented to slow or stop bone loss. The chemical, mechanical, and physical properties of LV and HV bone cement were compared.

Microgravity Environment

Compared to high viscosity PMMA bone cement, the mechanical properties of the commercially available low viscosity PMMA bone cement are superior. However, the effects of the glass transition temperature, residual monomer content, chemical functional group transmittance, crystallinity index, and flexural strength have not yet been determined. The purpose of this study is to determine how the higher flexural strength of LV bone cement compared to HV bone cement was caused by factors such as the glass transition temperature, residual monomer content, chemical functional group transmittance, and crystallinity index. Compared to HV bone cement, the thermal behavior analysis revealed that LV bone cement had a higher residual content and glass transition temperature. In addition, the chemical parameters of LV bone cement, such as the relatively low residual monomer content that can be calculated using Raman spectroscopy and the low transmittance of chemical functional groups that can be found in FTIR spectra, suggest that the material has a higher flexural strength than HV bone cement does.

According to the findings, the crystallinity index of LV bone cement was higher than that of HV bone cement. The glass transition temperature, crystallinity index, residual monomer content, and transmittance of chemical functional groups all play a role in the difference in flexural strength between LV and HV bone cements, which contributes to the development of PMMA bone cement and its applications. Osteoporosis and disuse bone loss are serious health issues that affect astronauts, bedridden patients, and the elderly. Grave bone loss makes the bone more porous, which weakens the bone and makes it more likely to break. Because mechanical loading enhances activities related to bone modeling and remodeling, preventative exercise is beneficial for preventing bone loss. Mechanosensory bone cells, or osteocytes, are thought to be stimulated by loading-induced fluid flow within the bone tissue. These osteocytes control the osteo-activities associated with bone remodeling. According to in vivo and in vitro research, bone loss has a negative impact on the bone's microarchitecture, such as its porosity and permeability, which makes it harder for the interstitial fluid flow that is necessary for the process of remodeling the bone.

Mechanosensory Bone Cells

Mechanical loads on the bone caused by physical exercise may increase interstitial fluid flow above the osteogenic threshold. However, it is unclear how osteoporotic or disused bone tissue's interstitial fluid flow is affected by physiological loading from exercise. Consequently, a poromechanical finite element model is used to calculate the interstitial fluid flow in healthy and osteoporotic/disused cortical bone tissue in response to exercise gait loading waveforms. According to the findings, compared to healthy tissue, osteoporotic and disused cortical bone tissue has greater porosity and less permeability, resulting in comparatively lower pore pressure and fluid velocity. Additionally, physiological loading exercises help to increase fluid flow in diseased tissue, which in turn stimulates bone cells to perform better in the process of bone remodeling. In general, the results of this study may aid in the design of potential physiological exercises to prevent osteoporosis and excessive bone loss. Individual fracture risk assessment in aromatase inhibitor-treated early breast cancer patients lacks sensitivity for bone mineral density. In postmenopausal women with HR-positive early breast cancer, aromatase inhibitors are frequently used as adjuvant therapy. It is known that these agents cause a gradual decline in bone strength, increasing the risk of fracture. In postmenopausal women, bone mineral density is regarded as a reliable indicator of bone strength.

Due to the relationship between density and failure of a loaded material, it has been demonstrated that in this setting, the risk of fracture doubles for each standard deviation reduction in BMD. Critical bone defects are the result of segmental bone loss caused by trauma, infection, or tumor and are a therapeutic issue that has not yet been addressed by existing reconstructive or regenerative techniques. The chemotactic and angiogenic potential of scaffolds functionalized with naturally occurring bioactive factor mixtures is promising in vitro, suggesting that they may stimulate bone regeneration in vivo. Histological examination of the number of vessels, activity of osteoclasts and osteoblasts, and defect healing degree was performed. Further concentration or prolonged release of bioactive factor mixtures may possibly have a synergistic effect. It is still unknown whether cortical and trabecular bone have different bone nano-mechanical properties, but it is important to know how each compartment contributes to bone strength. Additionally, the organization of trabecular bone serves to optimize load transfer and force distribution. Therefore, the bone's strength depends on both.