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This study focused on the pathological characteristics of glucocorticoid-induced osteoporosis and screened active monomers from a quinone compound library to determine de-cyclopentylquinone as the core research substance. This substance can improve the oxidative stress abnormalities and osteogenic inhibition of bone marrow mesenchymal stem cells under hormone intervention, and protect the bone tissue in animal models and regulate the survival state of osteoblasts. The study confirmed that its core mechanism relies on the CD39/CD73/adenosine signaling axis, by increasing extracellular adenosine content to activate downstream osteogenic-related signaling pathways, and by optimizing the drug action form through bone-targeting liposomes, it also clarified the intrinsic association between purinergic signaling and the oxidative-reductive homeostasis of bone tissue.
This review addresses the regeneration and repair challenges caused by the heterogeneity of bone-cartilage tissue, with the tissue engineering system combining mesenchymal stem cells and biomaterial scaffolds as the core, clarifying the regulatory mechanism of biological physical signals on the fate of stem cells, systematically summarizing the progress in the design of biomimetic microenvironment scaffolds under mechanical biology guidance, achieving precise regulation of the lineage-specific differentiation of mesenchymal stem cells, and providing theoretical support and design references for layered bone-cartilage regeneration, especially the regeneration of subchondral bone.
01 Research Background
Long-term use of glucocorticoids can induce osteoporosis-related bone lesions, which are accompanied by increased oxidative stress in the body and significant inhibition of the physiological process of bone formation. The existing research intervention methods cannot simultaneously achieve the regulation of oxidative stress damage and the positive repair of osteogenic function. There is still a lack of suitable active substances and clear target regulatory mechanisms. It is necessary to explore new bone-protecting active components from natural compound libraries to improve the mechanism research system for this type of bone disease.
The tendon-bone transitional tissue has a highly specialized extracellular matrix structure, with the core feature being the hierarchical arrangement of collagen and the gradient composition of minerals. This structural system can achieve stable force transmission and guide the cell phenotype of the spatial organization. Currently, it is impossible to precisely reproduce the complex multi-scale structure and composition gradient at the tendon-bone interface, which has become a key bottleneck hindering the integration and regeneration of soft and hard tissues. It is urgently needed to develop a biomimetic matrix construction scheme that conforms to the characteristics of natural structures.
02 Main Content
Based on the quinone compound resource library, a high-throughput screening was carried out, and the functional active substance de-cyclopentylquinone was locked through osteogenic-related reporter cells. The regulatory effect of this substance on the oxidative stress, apoptosis, and osteogenic differentiation ability of stem cells induced by dexamethasone was explored. The molecular mechanism of de-cyclopentylquinone exerting bone protection through the CD39/CD73/adenosine signaling axis was deeply analyzed. A bone-targeting drug-loaded liposome carrier was constructed to optimize the expression of the active substance in the body. The mechanism of the association between purinergic signaling and the oxidative-reductive homeostasis of bone tissue was supplemented and clarified.
03 Research Design
The first stage established a high-throughput screening platform, using Runx2 promoter luciferase reporter cells to complete the initial screening and candidate substance locking of quinone compounds; the second stage conducted in vitro cell experiments, using bone marrow mesenchymal stem cells as the research object, to verify the improvement effect of the active substance on the oxidative stress, cell apoptosis, and osteogenic differentiation inhibition caused by glucocorticoid; the third stage constructed a mouse model of glucocorticoid-induced osteoporosis to conduct in vivo validation experiments on bone phenotype and cell state; the fourth stage intervened in key targets within the signaling axis through gene knockdown technology to confirm the core mediating role of the pathway; finally, a bone-targeting liposome drug delivery system was prepared to explore the optimization effect of carrier modification on the biological action of the active substance.
04 Results
In vitro experiments showed that de-cyclopentylquinone could effectively reverse the oxidative stress disorder caused by glucocorticoids in stem cells, improve the state of osteogenic differentiation inhibition of cells, and reduce the level of cell apoptosis; In in vivo animal experiments, this active substance can slow down the process of bone mineral loss, alleviate the oxidative stress response within the bone tissue, and inhibit the apoptosis damage of osteoblasts. At the mechanism level, de-cyclo-pyronine can restore the function of the CD39/CD73/adenosine signaling axis that has been disrupted by glucocorticoids, and increase the content of adenosine outside the cells. Adenosine can produce a dual protective effect, alleviating oxidative stress and cell apoptosis, and activating specific adenosine receptors to initiate a downstream multi-level signal cascade reaction, promoting the expression of osteogenic-related genes. After gene knockdown of the core proteins within the signaling axis, the bone protection-related effects of de-cyclo-pyronine and exogenous adenosine will disappear. After being modified by bone-targeting liposomes, the biological regulatory effect of this active substance in the body is further strengthened.
05 Extension of the thinking
It is possible to expand the screening of homologous derivatives of quinone compounds to explore more similar substances with bone protection activity; it is possible to further investigate the differential regulatory rules of the CD39/CD73/adenosine signaling axis in different bone functional cells such as osteoblasts and osteoclasts; it is possible to extend the exploration of the role logic of this signaling axis in other pathological models of bone damage mediated by oxidative stress; it is possible to further optimize the carrier compatibility structure based on the existing design ideas of bone-targeting drug delivery carriers, and at the same time explore the synergistic regulatory relationship between other endogenous active substances and this adenosine signaling axis.
