Prevalence of glucocorticoid induced osteonecrosis in the mouse is not affected by treatments that maintain bone vascularity.

OBJECTIVE: Determine if LLP2A-Ale or PTH (1-34) affects the prevalence of glucocorticoid-induced osteonecrosis (ON) in a mouse model. METHODS: Eight-week-old young adult male BALB/cJ mice were weight-randomized into Control (Con), glucocorticoid (GC)-only, or concurrent treatments with GC and LLP2A-Ale (250 µg/kg or 500 µg/kg, IV, Days 1, 14, 28) or parathyroid hormone hPTH (1-34) (40 µg/kg, 5×/week). Mice were necropsied after 45 days for qualitative evaluation of prevalent ON and quantitative evaluation of vascularity in the distal femoral epiphysis (DFE); and quantitative evaluation of bone mass, microarchitecture, and strength in the distal femoral metaphysis and lumbar vertebral body. RESULTS: The prevalence of ON was 14% in the Con group and 36% in the GC-only group (P = 0.07). The prevalence of ON did not differ among GC-only, GC + LLP2A-Ale, and GC + PTH groups. GC-only mice had significantly lower trabecular and cortical bone strength than Con, while GC + LLP2A-Ale (500 µg/kg) and GC + PTH (1-34) groups had significantly greater trabecular bone strength than the GC-only group. GC + LLP2A-Ale (250 µg/kg and 500 µg/kg) and GC + PTH had significantly higher trabecular bone volume than GC-only mice at the vertebrae, distal femoral epiphyses and distal femoral metaphyses. DFE vascularity was lower in GC-only mice than in all other groups. CONCLUSION: Neither LLP2A-Ale nor hPTH (1-34) reduced the prevalence of GC-induced ON, compared to GC-only mice. However, GC-treated mice given LLP2A-Ale or hPTH (1-34) had better bone mass, microarchitecture, and strength in trabecular-rich regions, and higher levels of vascularity than GC-only mice.

Sex dimorphic regulation of osteoprogenitor progesterone in bone stromal cells.

Increasing peak bone mass is a promising strategy to prevent osteoporosis. A mouse model of global progesterone receptor (PR) ablation showed increased bone mass through a sex-dependent mechanism. Cre-Lox recombination was used to generate a mouse model of osteoprogenitor-specific PR inactivation, which recapitulated the high bone mass phenotype seen in the PR global knockout mouse mode. In this work, we employed RNA sequencing analysis to evaluate sex-independent and sex-dependent differences in gene transcription of osteoprogenitors of wild-type and PR conditional knockout mice. PR deletion caused marked sex hormone-dependent changes in gene transcription in male mice as compared to wild-type controls. These transcriptional differences revealed dysregulation in pathways involving immunomodulation, osteoclasts, bone anabolism, extracellular matrix interaction and matrix interaction. These results identified many potential mechanisms that may explain our observed high bone mass phenotype with sex differences when PR was selectively deleted in the MSCs.

Beta-Ecdysone Protects Mouse Osteoblasts from Glucocorticoid-Induced Apoptosis In Vitro.

Glucocorticoid-induced osteoporosis is a common form of secondary osteoporosis. Glucocorticoids affect both bone formation and resorption, and prolonged glucocorticoid exposure can suppress osteoblast activities. beta-Ecdysone, found in many plants, is involved in protein synthesis, carbohydrate and lipid metabolism, and immunologic modulation. Here, we evaluated the effects of beta-ecdysone on osteoblast viability by assessing apoptosis following treatment with excess glucocorticoids. Mouse bone marrow stromal cells were induced to differentiate and grow into osteoblasts, and then treated with 10 µM glucocorticoid and 10, 1, or 0.1 µM beta-ecdysone. The expression levels of osteoblast growth and differentiation factors (runt-related transcription factor 2, osteogenic protein-1, and alkaline phosphatase), apoptosis-related genes (transformation-related protein 53, ataxia telangiectasia mutated protein, caspase-3, and caspase-8), and Akt1 and phospho-Akt (Thr308) were then assessed via alkaline phosphatase staining, acridine orange-propidium iodide staining, annexin V/PI apoptosis assay, real-time RT-PCR, and Western blot analyses. Notably, treatment with 10 µM glucocorticoid resulted in reduced osteoblast viability and the specific activity of alkaline phosphatase as well as reduced runt-related transcription factor 2, osteogenic protein-1, and alkaline phosphatase mRNA expression in vitro, indicating that glucocorticoid inhibited osteogenic differentiation. Moreover, glucocorticoid treatment yielded increased transformation-related protein 53, ataxia telangiectasia mutated protein, caspase-3, and caspase-8 expression and decreased Akt1 and phospho-Akt levels, indicating glucocorticoid-induced apoptosis. Meanwhile, beta-ecdysone inhibited glucocorticoid function, preserving the expression of Akt1 and phospho-Akt and reducing the expression of transformation-related protein 53, ataxia telangiectasia mutated protein, caspase-3, and caspase-8. Thus, beta-ecdysone prevented glucocorticoid-induced osteoblast apoptosis in vitro. These data highlight the potential for beta-ecdysone as a treatment for preventing the effects of glucocorticoid on bone growth.

Improved Mobilization of Exogenous Mesenchymal Stem Cells to Bone for Fracture Healing and Sex Difference.

Mesenchymal stem cell (MSC) transplantation has been tested in animal and clinical fracture studies. We have developed a bone-seeking compound, LLP2A-Alendronate (LLP2A-Ale) that augments MSC homing to bone. The purpose of this study was to determine whether treatment with LLP2A-Ale or a combination of LLP2A-Ale and MSCs would accelerate bone healing in a mouse closed fracture model and if the effects are sex dependent. A right mid-femur fracture was induced in two-month-old osterix-mCherry (Osx-mCherry) male and female reporter mice. The mice were subsequently treated with placebo, LLP2A-Ale (500 µg/kg, IV), MSCs derived from wild-type female Osx-mCherry adipose tissue (ADSC, 3 x 105 , IV) or ADSC + LLP2A-Ale. In phosphate buffered saline-treated mice, females had higher systemic and surface-based bone formation than males. However, male mice formed a larger callus and had higher volumetric bone mineral density and bone strength than females. LLP2A-Ale treatment increased exogenous MSC homing to the fracture gaps, enhanced incorporation of these cells into callus formation, and stimulated endochondral bone formation. Additionally, higher engraftment of exogenous MSCs in fracture gaps seemed to contribute to overall fracture healing and improved bone strength. These effects were sex-independent. There was a sex-difference in the rate of fracture healing. ADSC and LLP2A-Ale combination treatment was superior to on callus formation, which was independent of sex. Increased mobilization of exogenous MSCs to fracture sites accelerated endochondral bone formation and enhanced bone tissue regeneration. Stem Cells 2016;34:2587-2600.

ß-Ecdysone Augments Peak Bone Mass in Mice of Both Sexes.

BACKGROUND: One of the strongest predictors for osteoporosis is peak bone mass. Interventions to augment peak bone mass have yet to be developed. ß-Ecdysone (ßEcd), a natural steroid-like compound produced by arthropods to initiate metamorphosis, is believed to have androgenic effects and so may be used to augment bone mass. QUESTIONS/PURPOSES: The purpose of this study was to use both male and female (1) gonadal-sufficient; and (2) -insufficient mice to investigate sex differences in terms of bone development and structure after ßEcd administration. METHODS: Two-month-old male and female Swiss-Webster mice were randomized to receive either vehicle or ßEcd (0.5 mg/kg) for 3 weeks. In a separate experiment to evaluate the effects of ßEcd on sex hormone-deficient mice, gonadectomy was performed in male (orchiectomy [ORX]) and female mice (ovariectomy [OVX]). Sham-operated and the ORX/OVX mice were then treated for 3 weeks with ßEcd. Primary endpoints for the study were trabecular bone structure and bone strength. RESULTS: In male mice, the trabecular bone volume was 0.18±0.02 in the placebo-treated (PL) and 0.23±0.02 in the ßEcd-treated group (p<0.05 versus PL); and 0.09±0.01 in the ORX group (p<0.05 versus PL) and 0.12±0.01 in the ORX+ßEcd group. Vertebral bone strength (maximum load) was 43±2 in PL and 51±1 in the ßEcd-treated group (p<0.05 versus PL); and 30±4 in the ORX group (p<0.05 versus PL) and 37±3 in the ORX+ßEcd group. In female mice, trabecular bone volume was 0.23±0.02 in PL and 0.26±0.02 in the ßEcd-treated group (p<0.05 versus PL); and 0.15±0.01 in the OVX group (p<0.05 versus PL) and 0.14±0.01 in the OVX+ßEcd group. Maximum load of the vertebrae was 45±2 in PL and 48±4 in the ßEcd-treated group; and 39±4 in the OVX group (p<0.05 versus PL) and 44±4 in the OVX+ßEcd group. CONCLUSIONS: These findings suggest the potential use of ßEcd in the augmentation of bone mass in growing male and female mice. It may also partially prevent the detrimental effects of gonadectomy on trabecular bone. CLINICAL RELEVANCE: Our results support the potential use of ßEcd or nature products that are rich in ßEcd to augment peak bone mass. ßEcd may differ from the other anabolic hormone treatments that may have severe side effects such as serious cardiac complications. However, its effects on humans remain to be determined.

Prevention of glucocorticoid induced bone changes with beta-ecdysone.

Beta-ecdysone (ßEcd) is a phytoecdysteroid found in the dry roots and seeds of the asteraceae and achyranthes plants, and is reported to increase osteogenesis in vitro. Since glucocorticoid (GC) excess is associated with a decrease in bone formation, the purpose of this study was to determine if treatment with ßEcd could prevent GC-induced osteoporosis. Two-month-old male Swiss-Webster mice (n=8-10/group) were randomized to either placebo or slow release prednisolone pellets (3.3mg/kg/day) and treated with vehicle control or ßEcd (0.5mg/kg/day) for 21days. GC treatment inhibited age-dependent trabecular gain and cortical bone expansion and this was accompanied by a 30-50% lower bone formation rate (BFR) at both the endosteal and periosteal surfaces. Mice treated with only ßEcd significantly increased bone formation on the endosteal and periosteal bone surfaces, and increased cortical bone mass were their controls to compare to GC alone. Concurrent treatment of ßEcd and GC completely prevented the GC-induced reduction in BFR, trabecular bone volume and partially prevented cortical bone loss. In vitro studies determined that ßEcd prevented the GC increase in autophagy of the bone marrow stromal cells as well as in whole bone. In summary, ßEcd prevented GC induced changes in bone formation, bone cell viability and bone mass. Additional studies are warranted of ßEcd for the treatment of GC induced bone loss.

Association of serum uric acid and incident nonspine fractures in elderly men: the Osteoporotic Fractures in Men (MrOS) study.

Uric acid (UA) is produced from purines by the enzyme xanthine oxidase, and elevated levels may cause arthritis and kidney stones. Conversely, UA also appears to function as an antioxidant and may protect against the oxidative stress associated with aging and disease. We performed a prospective fracture case-cohort study to understand the relation of UA and fracture risk in older men enrolled in the Osteoporotic Fractures in Men (MrOS) study. In the cohort of 5994 men aged 65 years and older attending the baseline MrOS examination, we evaluated a subgroup 1680 men in a case-cohort study design. The analytic group included 387 men with incident nonspine fractures (73 hip) and a random sample of 1383. Serum UA was measured in baseline serum samples. Modified proportional hazards models that account for case-cohort study design were used to estimate the relative hazards (RH) of hip and nonspine fracture in men for serum UA. Models were adjusted for age, race, clinic site, body mass index, vitamin D, parathyroid hormone, walking speed, Physical Activity Scale for the Elderly (PASE) score, frailty, and total. Subjects with incident nonspine fractures were older, had lower total hip bone mineral density (BMD), and higher serum phosphorus. There was an 18% decreased risk of nonspine fractures (95% confidence interval [CI] 0.71-0.93; p = 0.003) per 1 SD increase of baseline serum and 34% decreased risk of nonspine fractures in quartile 4 of UA versus quartiles 1, 2, and 3 (95% CI 0.49-0.89; p = 0.028) compared with nonfracture cases after multivariate adjustment. Hip fractures were not significantly associated with UA. Total hip BMD was significantly higher in the group of men with high UA levels compared with lower UA levels and increased linearly across quartiles of UA after multivariate adjustment (p for trend = 0.002). In summary, higher serum UA levels were associated with a reduction in risk of incident nonspine fractures but not hip fractures and higher hip BMD.