Nothobranchius furzeri, the Turquoise Killifish: A Model of Age-Related Osteoporosis?

INTRODUCTION: Osteoporosis is a frequent age-related disease, which affects millions of people worldwide. Despite significant progress in the treatment of the disease, a high number of patients still are underdiagnosed and undertreated. Therefore, novel animal models for the investigation of the disease are necessary. Nothobranchius furzeri is the shortest-lived vertebrate (with a lifespan of 3-7 months) that can be kept in captivity. Although it is an established model for aging research, studies on bone are lacking. The aim of this study was therefore to characterize N. furzeri as a potential model for age-related osteoporosis. MATERIALS AND METHODS: Bone properties of aging N. furzeri were investigated in male and female fish of the Gona Re Zhou strain, which were between 8 and 20 weeks old. Micro-computed tomography (Scanco Medical µCT35) was performed to determine the bone properties of the vertebral bodies. Bone structure and remodeling were investigated by different histological staining techniques and histomorphometry. The chemical composition of fish vertebrae and intervertebral discs was analyzed by Raman microspectroscopy. RESULTS: Osteoblasts, mono- and multinucleated osteoclasts but no osteocytes could be observed in the vertebral area of N. furzeri. Histomorphometric evaluations revealed a significant decrease of the number of osteoblasts/bone perimeter and for osteoid volume/bone volume (BV) a trend toward a decrease in old male N. furzeri. Comparing male and female fish, males showed higher BV densities and cortical thickness. The relative values of the bone volume density of 20-week-old male N. furzeri were significantly lower than 10-week-old ones. The mineral to matrix ratio increased with age in male and female fish. In the intervertebral discs, proteoglycans in relation to the organic matrix were significantly lower in older female fish. CONCLUSION: Our finding of a lack of osteocytes is in agreement with the fact that N. furzeri belongs to the evolutionarily advanced teleost fish. Furthermore, not only age-specific but also sex-specific differences were visible in the bone properties of N. furzeri, which can be taken into consideration for the study of gender aspects of age-related musculoskeletal diseases.

Age Related Osteoporosis: Targeting Cellular Senescence.

Age-related chronic diseases are an enormous burden to modern societies worldwide. Among these, osteoporosis, a condition that predisposes individuals to an increased risk of fractures, substantially contributes to increased mortality and health-care costs in elderly. It is now well accepted that advanced chronical age is one of the main risk factors for chronical diseases. Hence, targeting fundamental aging mechanisms such as senescence has become a promising option in the treatment of these diseases. Moreover, for osteoporosis, the main pathophysiological concepts arise from menopause causing estrogen deficiency, and from aging. Here, we focus on recent advances in the understanding of senescence-related mechanisms contributing to age-related bone loss. Furthermore, treatment options for senile osteoporosis targeting senescent cells are reviewed.

Assessment of Bone Microstructure by Micro CT in C57BL/6J Mice for Sex-Specific Differentiation.

It remains uncertain which skeletal sites and parameters should be analyzed in rodent studies evaluating bone health and disease. In this cross-sectional mouse study using micro-computed tomography (µCT), we explored: (1) which microstructural parameters can be used to discriminate female from male bones and (2) whether it is meaningful to evaluate more than one bone site. Microstructural parameters of the trabecular and/or cortical compartments of the femur, tibia, thoracic and lumbar vertebral bodies, and skull were evaluated by µCT in 10 female and 10 male six-month-old C57BL/6J mice. The trabecular number (TbN) was significantly higher, while the trabecular separation (TbSp) was significantly lower in male compared to female mice at all skeletal sites assessed. Overall, bone volume/tissue volume (BV/TV) was also significantly higher in male vs. female mice (except for the thoracic spine, which did not differ by sex). Most parameters of the cortical bone microstructure did not differ between male and female mice. BV/TV, TbN, and TbSp at the femur, and TbN and TbSp at the tibia and lumbar spine could fully (100%) discriminate female from male bones. Cortical thickness (CtTh) at the femur was the best parameter to detect sex differences in the cortical compartment (AUC = 0.914). In 6-month-old C57BL/6J mice, BV/TV, TbN, and TbSp can be used to distinguish male from female bones. Whenever it is not possible to assess multiple bone sites, we propose to evaluate the bone microstructure of the femur for detecting potential sex differences.

Myostatin and markers of bone metabolism in dermatomyositis.

BACKGROUND: In dermatomyostis (DM) patients, inflammation, reduced activity, and medication have a negative impact on the musculoskeletal system. Several endocrine factors are involved in muscle growth and bone turnover. OBJECTIVE: We aimed to investigate factors regulating myogenesis and bone metabolism and to evaluate possible associations between these endocrine factors, muscle strength, and functional tests in DM patients. METHODS: We conducted a cross-sectional study in 20 dermatomyositis patients. Serum levels of myostatin (MSTN), follistatin (FSTN), dickkopf 1 (Dkk1), sclerostin (SOST), periostin (PSTN), the receptor activator nuclear factor kB ligand (RANKL):osteoprotegerin (OPG) ratio and fibroblast growth factor 23 (FGF23) were determined. Physical function was evaluated by hand-held strength measurement, chair rising test, timed up and go test and the 3-min walking test. RESULTS: Serum MSTN and FGF23 levels (2.5 [1.9; 3.2] vs. 1.9 [1.6; 2.3] and 2.17 [1.45; 3.26] vs. 1.28 [0.79; 1.96], respectively; p <  0.05) were significantly higher in DM patients than in controls. Dkk1 was significantly lower (11.4 [6.9; 20.0] vs. 31.8 [14.3; 50.6], p <  0.01). Muscle strength and physical function tests correlated with each other (e.g. hip flexion - timed up and go test: r = - 0.748, p < 0.01). CONCLUSION: In DM patients, biochemical musculo-skeletal markers are altered and physical function shows deficits. All these tests reflect independent of each other different deficits in long-term DM patients which is important for the assessment of DM patients as well as planning of therapeutic interventions in clinical routine.

Age- and Strain-Related Differences in Bone Microstructure and Body Composition During Development in Inbred Male Mouse Strains.

We explored age- and strain-related differences in bone microstructure and body composition in male C57BL/6J, DBA/2JRj and C3H/J mice. Bone microstructure of the femur, tibia and L4 was assessed by µCT at the age of 8, 16 and 24 weeks. The weight of several muscles and fat depots were measured at the same time points. At all timepoints, C3H/J mice had the thickest cortices followed by DBA/2JRj and C57BL/6J mice. Nevertheless, C57BL/6J mice had higher Tb.BV/TV and Tb.N, and lower Tb.Sp than DBA/2JRj and C3H/J mice at least at 24 weeks of age. Skeletal development patterns differed among strains. C57BL/6J and DBA/2JRj mice, but not C3H/J mice, experienced significant increases in the sum of the masses of 6 individual muscles by 24 weeks of age. In C57BL/6J and DBA/2JRj mice, the mass of selected fat depots reached highest values at 24 weeks, whist, in C3H/J mice, the highest values of fat depots masses were achieved at 16 weeks. Early strain differences in muscle and fat masses were largely diminished by 24 weeks of age. C3H/J and C57BL/6J mice displayed the most favorable cortical and trabecular bone parameters, respectively. Strain differences in body composition were less overt than strain specificity in bone microstructure, however, they possibly influenced aspects of skeletal development.

Circulating Myostatin Levels Decrease Transiently after Implantation of a Hip Hemi-Arthroplasty.

INTRODUCTION: Muscle and bone metabolism are both important for the healing of fractures and the regeneration of injured muscle tissue. The aim of this investigation was to evaluate myostatin and other regulating factors in patients with hip fractures who underwent hemi-arthroplasty. METHODS: Serum levels of myostatin (MSTN), follistatin (FSTN), dickkopf-1 (Dkk1), and periostin (PSTN) as well as markers of bone turnover were evaluated in patients with hip fractures before surgery and twice in the 2 weeks after surgery. These parameters were also evaluated in age- and gender-matched subjects without major musculoskeletal injury. RESULTS: MSTN was transiently reduced; its opponent FSTN was transiently increased. Dkk1, the negative regulator of bone mass, and PSTN, a marker of subperiosteal bone formation, increased after surgery. With regard to markers of bone turnover, resorption was elevated during the entire period of observation whereas the early bone formation marker N-terminal propeptide of type I collagen was elevated 12 days after surgery. CONCLUSIONS: Unexpectedly, MSTN, a negative regulator of muscle growth, was reduced after surgery compared with before surgery. As musculoskeletal markers are altered during bone healing, they do not reflect general bone metabolism after fracture or joint arthroplasty. This is important because many elderly patients receive treatment for osteoporosis.

Bone Effects of Binge Alcohol Drinking Using Prepubescent Pigs as a Model.

BACKGROUND: Although chronic alcohol consumption in adults is an established risk factor for osteoporotic fractures, there is a huge gap in our knowledge about bone effects of binge drinking in adolescents. The aim of this pilot study was therefore to assess skeletal effects of binge alcohol drinking using prepubescent pigs as a large animal model. METHODS: Piglets aged 2 months were offered alcohol orally as a mixture of hard liquor and apple juice. Those with the highest propensity to drink alcohol were included in the experiment and received 1.4 g alcohol/kg bodyweight 2 times per week for 2 months (alcohol group); control piglets received apple juice in an identical manner. At the age of 4 months, the animals were euthanized; trabecular and cortical bone samples from the femur, the tibia, the humerus, and the fourth vertebral body harvested during necropsy were assessed by microcomputed tomography and dynamic histomorphometry. In addition, blood chemistry and blood alcohol determinations were performed. RESULTS: Blood alcohol levels assessed 1 hour after alcohol administration were 0.99‰ ± 0.15, 1.12‰ ± 0.2, and 1.14‰ ± 0.18 at the ages of 2, 3, and 4 months, respectively. In the alcohol group, serum calcium and phosphate levels were decreased. In the femur, trabecular number and connectivity density were lower in the alcohol than in the control group, and in the humerus and the fourth vertebral bodies, an opposite pattern was seen for trabecular number and connectivity density, respectively. Cortical density was higher in the humerus and trabecular density higher in the tibia of the alcohol group compared to the control group. Cortical porosity was lower in the humerus of the alcohol group. No significant differences were seen for trabecular thickness, trabecular separation, bone volume fraction, and static and dynamic histomorphometric parameters. CONCLUSIONS: In this pilot study, we have assessed skeletal effects of binge alcohol drinking by using prepubescent pigs as a promising large animal model. Binge drinking has bone effects that are site-specific. However, these data have to be verified in a larger study population.

Immunology of Osteoporosis: A Mini-Review.

Osteoporosis is a major cause of fractures and associated morbidity in the aged population. The pathogenesis of osteoporosis is multifactorial; whereas traditional pathophysiological concepts emphasize endocrine mechanisms, it has been recognized that also components of the immune system have a significant impact on bone. Since 2000, when the term 'osteoimmunology' was coined, novel insights into the role of inflammatory cytokines by influencing the fine-tuned balance between bone resorption and bone formation have helped to explain the occurrence of osteoporosis in conjunction with chronic inflammatory reactions. Moreover, the phenomenon of a low-grade, chronic, systemic inflammatory state associated with aging has been defined as 'inflamm-aging' by Claudio Franceschi and has been linked to age-related diseases such as osteoporosis. Given the tight anatomical and physiological coexistence of B cells and the bone-forming units in the bone marrow, a role of B cells in osteoimmunological interactions has long been suspected. Recent findings of B cells as active regulators of the RANK/RANKL/OPG axis, of altered RANKL/OPG production by B cells in HIV-associated bone loss or of a modulated expression of genes linked to B-cell biology in response to estrogen deficiency support this assumption. Furthermore, oxidative stress and the generation of advanced glycation end products have emerged as links between inflammation and bone destruction.

Secondary confounders of osteoporotic hip fractures in patients admitted to a geriatric acute care department.

BACKGROUND: With respect to the pathogenesis of osteoporosis, primary and secondary forms of the disease can be distinguished. It has been recognized that the incidence of primary and secondary osteoporosis differs in women and men. OBJECTIVE: The aim of the present study was to assess the incidence and gender distribution of factors contributing to osteoporosis in older hip fracture patients. METHODS: In this cross-sectional study 404 patients with hip fractures and controls referred to an acute geriatric care department over a period of 15 months were included. The medical history was recorded and blood samples were analyzed for routine laboratory parameters. RESULTS: A total of 249 patients with hip fractures and 155 matched controls were studied. The Tinetti test and the Barthel index were found to show highly significant differences in both groups mainly because of the postoperative state of patients with fractures. Vitamin D deficiency was found in 94.1% of male fracture patients and 94.6% of female fracture patients. On average 2.4 secondary contributors of osteoporosis were present in male fracture patients versus 2.9 in male controls and 2.3 in female fracture patients versus 2.3 in female controls. For most parameters no significant gender differences of possible secondary contributors to osteoporosis were found. Secondary osteoporosis was diagnosed in all male fracture patients and in 56.2% of all female fracture patients. CONCLUSION: Based on the findings of this study it is recommended that hip fracture patients should be assessed for secondary contributors of osteoporosis. Although the overall distribution of secondary contributors was similar in women and men, the prevalence of secondary osteoporosis was higher in men.

Serum levels of sclerostin and dickkopf-1: effects of age, gender and fracture status.

BACKGROUND: Fragility fractures, especially hip fractures, are a very common complication of osteoporosis in elderly subjects. Sclerostin (SOST) and dickkopf-1 (DKK-1) are inhibitors of the canonical wnt signalling pathway and thus could be involved in the pathogenesis of age-related bone fragility. OBJECTIVE: To investigate SOST and DKK-1 in a large group of geriatric patients with hip fractures and to relate the wnt inhibitors to age and gender. METHODS: This was a cross-sectional study carried out in a department of acute geriatric care in a district hospital in Upper Austria and a hospital in Vienna, Austria. A total of 256 geriatric patients (172 women and 84 men) and 67 young control subjects were selected after exclusion. Medical history was obtained, a comprehensive geriatric assessment was performed and serum levels of SOST, DKK-1 and bone formation markers were analysed. RESULTS: DKK-1 levels increased with age and in the presence of hip fractures. In contrast, SOST levels were lower in patients with hip fractures. When compared to women, men had higher SOST levels but lower DKK-1 levels. CONCLUSION: Serum levels of the inhibitors of the canonical wnt signalling pathway reflect different biological events and are useful for the study of bone fragility in geriatric patients.

The role of cathepsins in osteoimmunology.

Cathepsins are proteases comprising two small groups of serine and aspartic cathepsins and a large group of lysosomal cysteine cathepsins. Most of them are ubiquitously expressed throughout human tissues but some of them display a more restricted expression pattern and are involved in explicit tasks such as collagen degradation in the process of bone and cartilage destruction or degradation of invariant chain peptides in the process of antigen processing and presentation. In addition to the aforementioned functions, cathepsins have been shown to play a critical role in the pathogenesis of osteoimmunological diseases involving mutual interactions between skeletal and immunological functions. The most convincing evidence that cathepsins participate in the pathogenesis of osteoimmunological disorders exists for cathepsins K and S. Therefore, this review focuses on recent advances in understanding the role of cathepsins K and S in osteoimmunology and highlights the progress that has been made in targeting cathepsins to treat diseases related to the skeletal or immune system.

Challenges in establishing animal models for studying osteoimmunology of hypoparathyroidism.

Hypoparathyroidism is a relatively rare human and veterinary disease characterized by deficient or absent production of parathyroid hormone (PTH). PTH is known as a classical regulator of calcium and phosphorus homeostasis. Nevertheless, the hormone also appears to modulate immune functions. For example, increased CD4:CD8 T-cell ratios and elevated interleukin (IL)-6 and IL-17A levels were observed in patients with hyperparathyroidism, whereas gene expression of tumor necrosis factor-α (TNF-α) and granulocyte macrophage-colony stimulating factor (GM-CSF) was decreased in patients with chronic postsurgical hypoparathyroidism. Various immune cell populations are affected differently. So, there is a need for validated animal models for the further characterization of this disease for identifying targeted immune-modulatory therapies. In addition to genetically modified mouse models of hypoparathyroidism, there are surgical rodent models. Parathyroidectomy (PTX) can be well performed in rats-for pharmacological and associated osteoimmunological research and bone mechanical studies, a large animal model could be preferable, however. A major drawback for successfully performing total PTX in large animal species (pigs and sheep) is the presence of accessory glands, thus demanding to develop new approaches for real-time detection of all parathyroid tissues.

Circulating bioactive sclerostin levels in an Austrian population-based cohort.

BACKGROUND: Circulating serum sclerostin levels are supposed to give a good estimation of the levels of this negative regulator of bone mass within bone. Most studies evaluating total serum sclerostin found different levels in males compared to females and in older compared to younger subjects. Besides an ELISA detecting total sclerostin an ELISA determining bioactive sclerostin has been developed. The aim of this study was to investigate serum levels of bioactive sclerostin in an Austrian population-based cohort. METHODS: We conducted a cross-sectional observational study in 235 healthy subjects. Using the bioactive ELISA assay (Biomedica) bioactive sclerostin levels were evaluated. RESULTS: Serum levels of bioactive sclerostin were higher in men than in women (24%). The levels correlated positively with age (r = 0.47). A positive correlation could also be detected with body mass index and bone mineral density. CONCLUSION: Using the ELISA detecting bioactive sclerostin our results are consistent with data in the literature obtained by different sclerostin assays. The determination of sclerostin concentrations in peripheral blood thus appears to be a robust parameter of bone metabolism.

Differential Expression of Dickkopf 1 and Periostin in Mouse Strains with High and Low Bone Mass.

By expressing different genes and proteins that regulate osteoclast as well as osteoblast formation, osteocytes orchestrate bone metabolism. The aim of this project was the evaluation of the differences in the osteocytes' secretory activity in the low bone mass mouse strain C57BL/6J and the high bone mass strain C3H/J. The femura of eight- and sixteen-week-old male C57BL/6J and C3H/J mice­six animals per group­were analyzed. Using immunohistochemistry, osteocytes expressing dickkopf 1, sclerostin, periostin, fibroblast growth factor 23 (FGF23), and osteoprotegerin were detected. By means of the OsteoMeasure-System, 92.173 osteocytes were counted. At the age of eight weeks, approximately twice as many cortical and trabecular osteocytes from the C57BL/6J mice compared to the C3H/J mice expressed dickkopf 1 (p < 0.005). The number of cortical osteocytes expressing sclerostin was also higher in the C57BL/6J mice (p < 0.05). In contrast, the cortical and trabecular osteocytes expressing periostin were twice as high in the C3H/J mice (p < 0.005). The dickkopf 1 expressing osteocytes of the C57BL/6J mice decreased with age and showed a strain-specific difference only in cortical bone by 16 weeks of age (p < 0.05). In the C3H/J mice, the amount of osteocytes expressing periostin tended to increase with age. Thus, strain-related differences were maintained in 16-week-old rodents (p < 0.005). No strain-specific differences in the expression of FGF23 or osteoprotegerin in the cortical compartment could be detected. This experimental study showed that the osteocytes' protein expression reflects differences in bone characteristics and strain-related differences during skeletal maturation. Besides the osteocytes' expression of sclerostin, their expression of dickkopf 1 and periostin seems to be important for bone properties as well.

Osteoporosis: Pathophysiology and therapeutic options.

Osteoporosis is a metabolic bone disease that, on a cellular level, results from osteoclastic bone resorption not compensated by osteoblastic bone formation. This causes bones to become weak and fragile, thus increasing the risk of fractures. Traditional pathophysiological concepts of osteoporosis focused on endocrine mechanisms such as estrogen or vitamin D deficiency as well as secondary hyperparathyroidism. However, research over the last decades provided exiting new insights into mechanisms contributing to the onset of osteoporosis, which go far beyond this. Selected mechanisms such as interactions between bone and the immune system, the gut microbiome, and cellular senescence are reviewed in this article. Furthermore, an overview on currently available osteoporosis medications including antiresorptive and bone forming drugs is provided and an outlook on potential future treatment options is given.

Myostatin and other musculoskeletal markers in lung transplant recipients.

Recipients of lung transplantation (LuTx) may experience impaired muscle function and bone metabolism even after rehabilitation. We investigated the potential use of musculoskeletal markers in identifying the impairment of muscle function and bone function in these patients. Biochemical parameters, bodily functions, and lung function of 37 LuTx recipients were evaluated at the time of their discharge from the hospital stay and about 6 months later. The biomarkers were also assessed in 30 healthy age and gender distribution-matched controls. Compared to controls, the negative muscle regulator myostatin was elevated in LuTx recipients at baseline and follow-up, whereas its opponent follistatin only showed a group-specific difference at follow-up. LuTx recipients had reduced serum levels of sclerostin and increased levels of dickkopf 1 and periostin. Lung function and physical function were improved during follow-up. The change in lung function was correlated with the change in chair-rising time and the 6-min walking test. At follow-up, all musculoskeletal markers of LuTx recipients differed from those of controls, thus reflecting their still reduced lung function and bodily functions. Among the tested biomarkers, myostatin, sclerostin, dickkopf 1, and periostin were useful to detect impaired musculoskeletal function in LuTx recipients. Myostatin may serve as a target of treatment in the future.

Molecular mechanisms of osteoporotic hip fractures in elderly women.

A common manifestation of age-related bone loss and resultant osteoporosis are fractures of the hip. Age-related osteoporosis is thought to be determined by a number of intrinsic factors including genetics, hormonal changes, changes in levels of oxidative stress, or an inflammatory status associated with the aging process. The aim of this study was to investigate gene expression and bone architecture in bone samples derived from elderly osteoporotic women with hip fractures (OP) in comparison to bone samples from age matched women with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 10 women with low-trauma hip fractures (mean age 83±6) and consecutive surgical hip replacement. Ten bone samples from patients undergoing hip replacement due to osteoarthritis (mean age 80±5) served as controls. One half of each bone sample was subjected to gene expression analysis. The second half of each bone sample was analyzed by microcomputed tomography. From each half, samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. We could show a significantly decreased expression of the osteoblast related genes RUNX2, Osterix, Sclerostin, WNT10B, and Osteocalcin, a significantly increased ratio of RANKL to Osteoprotegerin, and a significantly increased expression of the enzymes superoxide dismutase 2 (SOD2) and glutathione peroxidase GPX3, and of the inflammatory cytokine IL6 in bone samples from hip fracture patients compared to controls. Major microstructural changes in OP bone were seen in the neck and were characterized by a significant decrease of bone volume, trabecular number, and connectivity density and a significant increase of trabecular separation. In conclusion, our data give evidence for a decreased expression of osteoblast related genes and increased expression of osteoclast related genes. Furthermore, increased expression of SOD2 and GPX3 suggest increased antioxidative activity in bone samples from elderly osteoporotic women with hip fractures.

Changes in Serum Levels of Myokines and Wnt-Antagonists after an Ultramarathon Race.

BACKGROUND: Regular physical activities have a positive effect on the muscular skeletal system but overstrenuous exercise may be different. Transiently suppressed bone formation and increased bone resorption after participation in a 246-km ultradistance race has been demonstrated. PURPOSE: The aim of this study was to analyze effects of the Spartathlon race on novel musculoskeletal markers. METHODS: Venous blood samples were obtained before and immediately after the race from 19 participants of the Spartathlon. From 9 runners who were available 3 days after the start blood was drawn for a third time. Serum levels of myostatin, an inhibitor of myogenic differentiation, and its opponent follistatin as well as sclerostin and dickkopf-1, both of them inhibitors of the wnt signaling pathway, and markers of bone turnover were determined. RESULTS: Serum levels of myostatin were significantly higher after the race. Serum follistatin only showed a transient increase. Sclerostin levels did not significantly differ before and after the race, whereas dickkopf-1 levels were significantly decreased. At follow-up a decrement of sclerostin and dickkopf-1 levels was seen. Serum cathepsin K levels did not change. CONCLUSION: The increase of serum levels of myostatin appears to reflect muscle catabolic processes induced by overstrenuous exercise. After the short-term uncoupling of bone turnover participation in an ultradistance race seems to initiate a long-term positive effect on bone indicated by the low-level inhibition of the Wnt/ß-catenin signaling pathway.

Molecular evidence of osteoblast dysfunction in elderly men with osteoporotic hip fractures.

Osteoporosis is extremely frequent in post-menopausal women; nevertheless, osteoporosis in men is also a severe and frequently occurring but often underestimated disease. Increasing evidence links bone loss in male idiopathic osteoporosis and age related osteoporosis to osteoblast dysfunction rather than increased osteoclast activity as seen in postmenopausal osteoporosis. The aim of this study was to investigate gene expression of osteoblast related genes and of bone architecture in bone samples derived from elderly osteoporotic men with hip fractures (OP) in comparison to bone samples from age matched men with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 12 men with low-trauma hip fractures and consecutive surgical hip replacement. Bone samples of age matched patients undergoing hip replacement due to osteoarthritis served as controls. One half of the bone samples was subjected to RNA extraction, reverse transcription, and real-time polymerase chain reactions. The second half of the bone samples was analyzed by static histomorphometry. From each half samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. OP patients displayed a significantly decreased RUNX2, Osterix and SOST expression compared to OA patients. Major microstructural changes in OP bone were seen in the subcortical region of the neck and were characterized by a significant decrease of bone volume, and a significant increase of trabecular separation. In conclusion, decreased local gene expression of RUNX2 and Osterix in men with hip fractures strongly supports the concept of osteoblast dysfunction in male osteoporosis. Major microstructural changes in the trabecular structure associated with osteoporotic hip fractures in men are localized in the subcortical region of the femoral neck.