Characteristics of the state of bone tissue in genetically modified mice with impaired enzymatic regulation of steroid hormone metabolism

Research Results in Pharmacology 8(4): 157–166 UDC: 615.275.4 DOI 10.3897/rrpharmacology.8.98779 Review Article Characteristics of the state of bone tissue in genetically modified mice with impaired enzymatic regulation of steroid hormone metabolism Mikhail V. Korokin1, Oleg S. Gudyrev1, Petr R. Lebedev1, Elena V. Kuzubova1, Alexandra I. Radchenko1, Ivan S. Koklin1, Eduard I. Taran1, Alim A. Kochkarov1 1 Belgorod State National Research University, 85 Pobedy St., Belgorod 308015, Russia Corresponding author: Mikhail V. Korokin () Academic editor: Tatyana Avtina ♦ Received 10 Ocotber 2022  ♦  Accepted 13 December 2022  ♦  Published 22 December 2022 Citation: Korokin MV, Gudyrev OS, Lebedev PR, Kuzubova EV, Radchenko AI, Koklin IS, Taran EI, Kochkarov AA (2022) Characteristics of the state of bone tissue in genetically modified mice with impaired enzymatic regulation of steroid hormone metabolism. Research Results in Pharmacology 8(4): 157–166. https://doi.org/10.3897/rrpharmacology.8.98779 Abstract Introduction: The aim was to evaluate the structural and functional changes of bone tissue in mice with null expression of 11β-HSD2 or both 11β-HSD2 and Apolipoprotein E. Materials and methods: The experimental study was performed in 60 male mice, weighting 24–30 g. The animals were kept in accordance with the rules of laboratory practice for preclinical studies on the territory of the Russian Federation. Mice lacking 11β-HSD2 (Hsd2-/-) and male mice lacking 11β-HSD2 and Apolipoprotein E (Hsd2-/-/Apoe-/-) were used in the study. We studied and characterized the state of bone tissue, indicators of bone density, microcirculation in bone tissue, endothelial dysfunction coefficient, width of bone trabeculae, as well as serum concentrations of bone alkaline phosphatase, hydroxyproline, deoxyprinoline and expression levels of p53, Bcl2, Bax, eNOS genes. Results and discussion: We showed that mice with the Hsd2-/- genotype with no expression of 11ß-HSD2 by the 6th month of life showed a statistically significant decrease in bone density, which progresses to the 7th and 8th months of life. At the 8th month of animal life, a decrease in bone density is accompanied by a statistically significant decrease in the level of microcirculation in the bone and an increase in the coefficient of endothelial dysfunction. Taking into account the relationship of endothelial dysfunction, atherogenesis and disorders in the processes of bone remodeling, in the framework of this study, we also assessed the state of bone tissue in double transgenes with the genotype Hsd2-/-/ Apoe-/-, which lack the expression of both 11ß-HSD2 and Apolipoprotein E. In this study, we also saw increased activation of processes leading to disruption of bone remodeling processes. In the group of the animals with the genotype Hsd2-/-/Apoe-/-, we found statistically significant differences from the mice with no expression of 11ß-HSD2 in bone density and microcirculation, and the width of bone trabeculae. Also, a statistically significant increase in hydroxyproline and deoxyprinoline was found in the group of double transgenes, in the absence of significant changes in the concentration of bone alkaline phosphatase. This fact indicates a pronounced activation of bone resorption processes in the absence of activation of osteosynthesis processes, which leads to the detected violation of bone remodeling processes. Conclusion: Thus, we have shown that a violation of the metabolic regulation of steroid hormone metabolism in animals with null expression of the 11ß-HSD2 (Hsd2-/- genotype) leads to the development of signs of osteoporosis – bone density decreases, which is accompanied by a decrease in the width of bone trabeculae, the level of microcirculation in bone tissue decreases simultaneously with an increase in the coefficient of endothelial dysfunction. The additional null expression of ApoE gene in double transgenes with the genotype Hsd2-/-/Apoe-/- leads to an increase in the severity of changes associated with a violation of bone remodeling processes and, in addition to a more pronounced change in Copyright Korokin MV et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 158 Korokin MV et al.: Characteristics of the state of bone tissue in genetically modified mice bone tissue density, bone trabecular width, microcirculation and the coefficient of endothelial dysfunction leads to an increase in the concentration of biochemical markers of bone resorption. These changes indicate the important role of the enzyme 11ß-hydroxysteroid dehydrogenase type 2 in the processes of bone remodeling disorders. Graphical abstract Keywords osteoporosis, bone density, steroid hormone metabolism, transgenic animals, 11ß-HSD2, Apoe, Hsd2-/-, Hsd2-/-/Apoe-/-. Introduction The World Health Organization has officially identified osteoporosis (OP) as one of the ten most important chronic diseases of mankind, because it is very widespread, has a clear definition, diagnostic methods, and opportunities for prevention and treatment. OP – a systemic skeletal disease from the group of metabolic osteopathies – is characterized by a decrease in bone mass and a violation of the microarchitectonics of bone tissue, which leads to a decrease in bone strength and, as a consequence, to an increased risk of fractures. Being one of the most frequent causes of pathological disabling fractures, osteoporosis significantly limits the quality and duration of life and aggravates the course of concomitant diseases (World Health Organization 2003; Sözen et al. 2017; Korokin et al. 2022). It is known that a decrease in osteoreparative processes and an increase in osteoresorption are often associated with a violation of steroid hormone metabolism. In this regard, the main risk factors for the development of osteoporosis are the postmenopausal period and long-term therapy with glucocorticoids (Laurent et al. 2022). Therefore, one of the most obvious directions for the search for molecular predictors and new targets for pharmacotherapy of osteoporosis is the system of tissue metabolism of steroid Research Results in Pharmacology 8(4): 157–166 hormones. The skeleton is one of the classic targets of glucocorticoid hormones. Corticosteroid activation in hypercorticism, prolonged treatment with corticosteroid hormones or aldosteronism is associated with a decrease in bone density (Frenkel et al. 2015; Kuipers et al. 2016). The enzyme 11b-hydroxysteroid dehydrogenase (11b-HSD), represented by two isoforms, performs the mutual conversion of cortisone and cortisol in tissues. Using the methods of reverse genetics, the systemic consequences of knockout of both isoforms were established. Convincing evidence demonstrates that both enzymes are involved in the pathogenesis o (...truncated)