Increased Bone Mass Research Articles

A Mild Case of Autosomal Recessive Osteopetrosis Masquerading as the Dominant Form Involving Homozygous Deep Intronic Variations in the CLCN7 Gene

Osteopetrosis is a heterogeneous group of rare hereditary diseases characterized by increased bone mass of poor quality. Autosomal-dominant osteopetrosis type II (ADOII) is most often caused by mutation of the CLCN7 gene leading to impaired bone resorption. Autosomal recessive osteopetrosis (ARO) is a more severe form and is frequently accompanied by additional morbidities. We report an adult male presenting with classical clinical and radiological features of ADOII. Genetic analyses showed no amino-acid-converting mutation in CLCN7 but an apparent haploinsufficiency and suppression of CLCN7 mRNA levels in peripheral blood mononuclear cells. Next generation sequencing revealed low-frequency intronic homozygous variations in CLCN7, suggesting recessive inheritance. In silico analysis of an intronic duplication c.595-120_595-86dup revealed additional binding sites for Serine- and Arginine-rich Splicing Factors (SRSF), which is predicted to impair CLCN7 expression. Quantitative backscattered electron imaging and histomorphometric analyses revealed bone tissue and material abnormalities. Giant osteoclasts were present and additionally to lamellar bone, and abundant woven bone and mineralized cartilage were observed, together with increased frequency and thickness of cement lines. Bone mineralization density distribution (BMDD) analysis revealed markedly increased average mineral content of the dense bone (CaMean T-score + 10.1) and frequency of bone with highest mineral content (CaHigh T-score + 19.6), suggesting continued mineral accumulation and lack of bone remodelling. Osteocyte lacunae sections (OLS) characteristics were unremarkable except for an unusually circular shape. Together, our findings suggest that the reduced expression of CLCN7 mRNA in osteoclasts, and possibly also osteocytes, causes poorly remodelled bone with abnormal bone matrix with high mineral content. This together with the lack of adequate bone repair mechanisms makes the material brittle and prone to fracture. While the skeletal phenotype and medical history were suggestive of ADOII, genetic analysis revealed that this is a possible mild case of ARO due to deep intronic mutation.

MAF1, a repressor of RNA polymerase III-dependent transcription, regulates bone mass.

MAF1, a key repressor of RNA polymerase (pol) III-mediated transcription, has been shown to promote mesoderm formation in vitro. Here, we show that MAF1 plays a critical role in regulating osteoblast differentiation and bone mass. Global deletion of MAF1 (Maf1-/- mice) produced a high bone mass phenotype. However, osteoblasts isolated from Maf1-/- mice showed reduced osteoblastogenesis ex vivo. Therefore, we determined the phenotype of mice overexpressing MAF1 in cells from the mesenchymal lineage (Prx1-Cre;LSL-MAF1 mice). These mice showed increased bone mass. Ex vivo, cells from these mice showed enhanced osteoblastogenesis concordant with their high bone mass phenotype. Thus, the high bone mass phenotype in Maf1-/- mice is likely due to confounding effects from the global absence of MAF1. MAF1 overexpression promoted osteoblast differentiation of ST2 cells while MAF1 downregulation inhibited differentiation, indicating MAF1 enhances osteoblast formation. However, other perturbations used to repress RNA pol III transcription, inhibited osteoblast differentiation. However, decreasing RNA pol III transcription through these perturbations enhanced adipogenesis in ST2 cells. RNA-seq analyzed the basis for these opposing actions on osteoblast differentiation. The different modalities used to perturb RNA pol III transcription resulted in distinct gene expression changes, indicating that this transcription process is highly sensitive and triggers diverse gene expression programs and phenotypic outcomes. Specifically, MAF1 induced genes known to promote osteoblast differentiation. Furthermore, genes that are induced during osteoblast differentiation displayed codon bias. Together, these results reveal a novel role for MAF1 and RNA pol III-mediated transcription in osteoblast fate determination, differentiation, and bone mass regulation.

Anoctamin 1 controls bone resorption by coupling Cl− channel activation with RANKL-RANK signaling transduction

Osteoclast over-activation leads to bone loss and chloride homeostasis is fundamental importance for osteoclast function. The calcium-activated chloride channel Anoctamin 1 (also known as TMEM16A) is an important chloride channel involved in many physiological processes. However, its role in osteoclast remains unresolved. Here, we identified the existence of Anoctamin 1 in osteoclast and show that its expression positively correlates with osteoclast activity. Osteoclast-specific Anoctamin 1 knockout mice exhibit increased bone mass and decreased bone resorption. Mechanistically, Anoctamin 1 deletion increases intracellular Cl− concentration, decreases H+ secretion and reduces bone resorption. Notably, Anoctamin 1 physically interacts with RANK and this interaction is dependent upon Anoctamin 1 channel activity, jointly promoting RANKL-induced downstream signaling pathways. Anoctamin 1 protein levels are substantially increased in osteoporosis patients and this closely correlates with osteoclast activity. Finally, Anoctamin 1 deletion significantly alleviates ovariectomy induced osteoporosis. These results collectively establish Anoctamin 1 as an essential regulator in osteoclast function and suggest a potential therapeutic target for osteoporosis.

BMP9 reduces age-related bone loss in mice by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis

Age-related osteoporosis is characterized by the accumulation of senescent osteoblastic cells in bone microenvironment and significantly reduced osteogenic differentiation. Clearing of the senescent cells is helpful to improve bone formation in aged mice. Bone morphogenetic protein 9 (BMP9), a multifunctional protein produced and secreted by liver, was reported to improve osteoporosis caused by estrogen withdrawal. However, the mechanism of BMP9 has not been fully elucidated, and its effect on senile osteoporosis has not been reported. This study reveals that BMP9 significantly increases bone mass and improves bone biomechanical properties in aged mice. Furthermore, BMP9 reduces expression of senescent genes in bone microenvironment, accompanied by decreased senescence-associated secretory phenotypes (SASPs) such as Ccl5, Mmp9, Hmgb1, Nfkb1, and Vcam1. In vitro, Bmp9 treatment inhibits osteoblast senescence through activating Smad1, which suppresses the transcriptional activity of Stat1, thereby inhibits P21 expression and SASPs production. Furthermore, inhibiting the Smad1 signal in vivo can reverse the inhibitory effect of BMP9 on Stat1 and downstream senescent genes, which eliminates the protection of BMP9 on age-related osteoporosis. These findings highlight the critical role of BMP9 on reducing age-related bone loss by inhibiting osteoblast senescence through Smad1-Stat1-P21 axis.

Osteopetrosis: A rare case

Osteopetrosis is a rare inherited metabolic bone disease characterized by failure of osteoclasts to resorb bone leading to impairment of bone modeling and remodeling. The defect in bone turnover results in skeletal fragility despite increased bone mass, hematopoietic insufficiency, disturbed tooth eruption, nerve entrapment syndromes, and growth failure. It has two major clinical forms: an autosomal dominant benign type or an autosomal recessive malignant type. The recessive form is usually fatal whereas the dominant type is more compatible with life. A rare autosomal recessive (intermediate form) is more prevalent and has less severe presentation. A 12-year-old boy presented with short stature, bilateral progressive vision loss, and backache. X-ray of nondominant hand for bone age estimation showed bone in bone formation. Followed which skeletal survey was done which showed characteristic radiological findings suggestive of osteopetrosis. Osteopetrosis is a rare disease transmitted by autosomal dominant or recessive inheritance having variable penetrance. We report here intermediate form of osteopetrosis. Although the genetic test is used to differentiate between the subtypes, diagnosis is mainly radiological.

Transiently increased serotonin has modest or no effects on bone mass accrual in growing female C57BL6/J or growing male and female Lrp5A214V mice.

Serotonin (5HT) is a chemical messenger with biologic activities affecting multiple organs. Within the skeletal system, studies in mice and humans suggest blood 5HT levels affect bone, with elevations impairing and reductions enhancing bone accrual. Other studies, however, have not supported this hypothesis. Recently, administering 5HT to a Piezo1 mutant mouse strain with hyposerotonemia, intestinal dysmotility, and a doubling of femoral trabecular bone mass at 2months of age, was reported to return the animals' intestinal motility and bone mass to normal. However, whether the 5HT directly affected bone metabolism or indirectly affected metabolism by improving intestinal function was not determined. Therefore, we administered 5HT to mice with normal intestinal function. We randomized female C57BL6/J mice and male and female mice that have increased bone mass due to a missense mutation in the WNT co-receptor LRP5 (Lrp5A214V) to receive 5HT or vehicle via daily IP injection from 4weeks to 8weeks of age. We did not observe consistent significant changes for distal femur trabecular, midshaft femur cortical, or vertebral body trabecular bone mass between 5HT treated and vehicle treated mice of either genotype. These data are compatible with other studies that have not observed a correlation between blood 5HT level and bone mass.

Quercetin Attenuates Osteoporosis in Orchiectomy Mice by Regulating Glucose and Lipid Metabolism via the GPRC6A/AMPK/mTOR Signaling Pathway.

Quercetin, a flavonoid found in natural medicines, has shown a role in disease prevention and health promotion. Moreover, because of its recently identified contribution in regulating bone homeostasis, quercetin may be considered a promising agent for improving bone health. This study aimed to elucidate the role of quercetin in androgen deprivation therapy-induced osteoporosis in mice. C57BL/6 mice were subjected to orchiectomy, followed by quercetin treatment (75 and 150 mg/kg/d) for 8 weeks. Bone microstructure was then assessed by micro-computed tomography, and a three-point bending test was used to evaluate the biomechanical parameters. Hematoxylin and eosin (H&E) staining was used to examine the shape of the distal femur, gastrocnemius muscle, and liver. The balance motion ability in mice was evaluated by gait analysis, and changes in the gastrocnemius muscle were observed via Oil red O and Masson’s staining. ELISA and biochemical analyses were used to assess markers of the bone, glucose, and lipid metabolism. Western blotting analyses of glucose and lipid metabolism-related protein expression was performed, and expression of the GPCR6A/AMPK/mTOR signaling pathway-related proteins was also assessed. After 8 weeks of quercetin intervention, quercetin-treated mice showed increased bone mass, bone strength, and improved bone microstructure. Additionally, gait analysis, including stride length and frequency, were significantly increased, whereas a reduction of the stride length and gait symmetry was observed. H&E staining of the gastrocnemius muscle showed that the cross-sectional area of the myofibers had increased significantly, suggesting that quercetin improves balance, motion ability, and muscle mass. Bone metabolism improvement was defined by a reduction of serum levels of insulin, triglycerides, total cholesterol, and low-density lipoprotein, whereas levels of insulin-like growth factor-1 and high-density lipoprotein were increased after quercetin treatment. Expression of proteins involved in glucose uptake was increased, whereas that of proteins involved in lipid production was decreased. Moreover, the GPRC6A and the phospho-AMPK/AMPK expression ratio was elevated in the liver and tibia tissues. In contrast, the phospho-mTOR/mTOR ratio was reduced in the quercetin group. Our findings indicate that quercetin can reduce the osteoporosis induced by testosterone deficiency, and its beneficial effects might be associated with the regulation of glucose metabolism and inhibition of lipid metabolism via the GPCR6A/AMPK/mTOR signaling pathway.

Physical Activity in Late Prepuberty and Early Puberty Is Associated With High Bone Formation and Low Bone Resorption.

BackgroundPhysical activity (PA) increases bone mass, especially in late prepuberty and early puberty, but it remains unclear if and how PA affects both bone formation and bone resorption.Materials and MethodsWe included 191 boys and 158 girls aged 7.7 ± 0.6 (mean ± SD) in a population-based PA intervention study. The intervention group (123 boys and 94 girls) received daily physical education (PE) in school (40 min/day; 200 min/week) from study start and during the nine compulsory school years in Sweden. The controls (68 boys and 64 girls) received the national standard of 1–2 classes PE/week (60 min/week). During the intervention, blood samples were collected at ages 9.9 ± 0.6 (n = 172; all in Tanner stages 1–2) and 14.8 ± 0.8 (n = 146; all in Tanner stages 3–5) and after termination of the intervention at age 18.8 ± 0.3 (n = 93; all in Tanner stage 5) and 23.5 ± 0.7 (n = 152). In serum, we analyzed bone formation markers [bone-specific alkaline phosphatase (bALP), osteocalcin (OC), and N-terminal propeptide of collagen type 1 (PINP)] and bone resorption markers [C-terminal telopeptide cross links (CTX) and tartrate-resistant acid phosphatase (TRAcP 5b)]. Linear regression was used to compare age and sex-adjusted mean differences between intervention children and controls in these markers.ResultsTwo years after the intervention was initiated (at Tanner stages 1–2), we found higher serum levels of bALP and OC, and lower serum levels of TRAcP 5b in the intervention compared with the control group. The mean difference (95% CI) was for bALP: 13.7 (2.1, 25.3) μg/L, OC: 9.1 (0.1, 18.1) μg/L, and TRAcP 5b: −2.3 (−3.9, −0.7) U/L. At Tanner stages 3–5 and after the intervention was terminated, bone turnover markers were similar in the intervention and the control children.ConclusionDaily school PA in the late prepubertal and early pubertal periods is associated with higher bone formation and lower bone resorption than school PA 1–2 times/week. In late pubertal and postpubertal periods, bone formation and resorption were similar. Termination of the intervention is not associated with adverse bone turnover, indicating that PA-induced bone mass benefits gained during growth may remain in adulthood.

Volleyball practice increases bone mass in prepubescent boys during growth: A 1-yr longitudinal study.

The aim of this longitudinal study was to examine the effects of 1-yr of volleyball practice on the bone mass development in the growing skeleton among prepubescent children. Twenty volleyball players and nine teen matched control boys (Tanner stage 1, at the start of the study) were followed over a 1-yr period. Bone mineral density (BMD, g/cm2), bone mineral content (BMC, g) were measured by dual-energy X-ray absorptiometry on the whole body, lumbar spine (L2–L4), legs, arms, femoral necks, hips and radii. At follow-up, in comparison with controls, volleyball players gained more BMD in whole body (4.5% vs 1.7%; p = 0.014), both nondominant and dominant arms (5.8% vs 1.1% p = 0.005, and 6% vs 2.1%; p = 0.003, respectively), both nondmoninat and dominant legs (9% vs 4.8%; p = 0.005 and 10.7% vs 6% p = 0.0025; respectively), dominant ultradistal radius (10.4% vs 0.9%; p = 0.005), dominant third distal radius (9.6% vs 3.71%; p = 0.023), dominant whole radius (7.4% vs 3.1%; p = 0.017), lumbar spine L2-L4 (9.9% vs 2.8%; p = 0.004), femoral neck (4.7% vs 1.6%; p = 0.034), trochanter (6% vs 1.5%; p<0.001) and total hip (6.1% vs 2.6%; p = 0.006). Volleyball players gained more BMC in both nondominant and dominant arms (25.1% vs 13.4%; p = 0.003, and 26.1% vs 15.6%; p<0.001 respectively), both nondominant and dominant legs (20.2% vs 14.5%; p = 0.004 and 23% vs 16%; p = 0.004, respectively), dominant ultradistal radius (22.4% vs 8.7%; p = 0.002), dominant third distal radius (20.9% vs 5.9%; p = 0.001), dominant whole radius (20% vs 13%), nondominant third distal radius (14.5% vs 5.9%; p = 0.001), nondominant whole radius (21.1% vs 12%; p = 0.002), lumbar spine L2-L4 (21.1% vs 13.7%; p = 0.007), femoral neck (25.9% vs 8.7%; p = 0.007), trochanter (23.5% vs 17.1%; p = 0.006), and total hip (16.3% vs 11.3%; p = 0.009) than controls. A close correlation was observed between the increment (Δ) of whole body lean mass and increased (Δ) BMD and BMC in whole body (r = 0.43, p<0.01, r = 0.73, p<0.001; respectively), lumbar spine (r = 0.54, r = 0.61, p<0.001; respectively), trochanter (r = 0.46, p<0.01, r = 0.35, p<0.05; respectively), and total hip (r = 0.53, p<0.01, r = 0.6, p<0.0001; respectively). In summary, 1-yr of volleyball practice has an osteogenic effect on bone mass in loaded sites in prepubescent boys.

Deletion of IL-17ra in osteoclast precursors increases bone mass by decreasing osteoclast precursor abundance.

Metabolic bone diseases, such as osteoporosis, typically reflect an increase in the number and activity of bone-resorbing osteoclasts that result in a loss of bone mass. Inflammatory mediators have been identified as drivers of both osteoclast formation and activity. The IL-17 family of inflammatory cytokines has gained attention as important contributors to both bone formation and resorption. The majority of IL-17 cytokines signal through receptor complexes containing IL-17a receptor (IL-17ra); however, the role of IL-17ra signaling in osteoclasts remains elusive. In this study, we conditionally deleted Il17ra in osteoclast precursors using LysM-Cre and evaluated the phenotypes of skeletally mature male and female conditional knockout and control mice. The conditional knockout mice displayed an increase in trabecular bone microarchitecture in both the appendicular and axial skeleton. Assessment of osteoclast formation in vitro revealed that deletion of Il17ra decreased osteoclast number, which was confirmed in vivo using histomorphometry. This phenotype was likely driven by a lower abundance of osteoclast precursors in IL-17ra conditional knockout mice. This study suggests that IL-17ra signaling in preosteoclasts can contribute to osteoclast formation and subsequent bone loss.

Skeletal muscle mitoribosomal defects are linked to low bone mass caused by bone marrow inflammation in male mice.

BackgroundMitochondrial oxidative phosphorylation (OxPhos) is a critical regulator of skeletal muscle mass and function. Although muscle atrophy due to mitochondrial dysfunction is closely associated with bone loss, the biological characteristics of the relationship between muscle and bone remain obscure. We showed that muscle atrophy caused by skeletal muscle‐specific CR6‐interacting factor 1 knockout (MKO) modulates the bone marrow (BM) inflammatory response, leading to low bone mass.MethodsMKO mice with lower muscle OxPhos were fed a normal chow or high‐fat diet and then evaluated for muscle mass and function, and bone mineral density. Immunophenotyping of BM immune cells was also performed. BM transcriptomic analysis was used to identify key factors regulating bone mass in MKO mice. To determine the effects of BM‐derived CXCL12 (C–X–C motif chemokine ligand 12) on regulation of bone homeostasis, a variety of BM niche‐resident cells were treated with recombinant CXCL12. Vastus lateralis muscle and BM immune cell samples from 14 patients with hip fracture were investigated to examine the association between muscle function and BM inflammation.ResultsMKO mice exhibited significant reductions in both muscle mass and expression of OxPhos subunits but increased transcription of mitochondrial stress response‐related genes in the extensor digitorum longus (P < 0.01). MKO mice showed a decline in grip strength and a higher drop rate in the wire hanging test (P < 0.01). Micro‐computed tomography and von Kossa staining revealed that MKO mice developed a low mass phenotype in cortical and trabecular bone (P < 0.01). Transcriptomic analysis of the BM revealed that mitochondrial stress responses in skeletal muscles induce an inflammatory response and adipogenesis in the BM and that the CXCL12–CXCR4 (C–X–C chemokine receptor 4) axis is important for T‐cell homing to the BM. Antagonism of CXCR4 attenuated BM inflammation and increased bone mass in MKO mice. In humans, patients with low body mass index (BMI = 17.2 ± 0.42 kg/m2) harboured a larger population of proinflammatory and cytotoxic senescent T‐cells in the BMI (P < 0.05) and showed reduced expression of OxPhos subunits in the vastus lateralis, compared with controls with a normal BMI (23.7 ± 0.88 kg/m2) (P < 0.01).ConclusionsDefects in muscle mitochondrial OxPhos promote BM inflammation in mice, leading to decreased bone mass. Muscle mitochondrial dysfunction is linked to BM inflammatory cytokine secretion via the CXCL12–CXCR4 signalling axis, which is critical for inducing low bone mass.

Melatonin increases bone mass in normal, perimenopausal, and postmenopausal osteoporotic rats via the promotion of osteogenesis

BackgroundOsteoporosis is a disease threatening the health of millions of individuals. Melatonin is found to be a potential anti-osteoporosis drug. However, whether melatonin plays a role against osteoporosis at different stages of the menopause and the underlying mechanisms are unknown.MethodsOvariectomy was utilized as a model of perimenopausal and postmenopausal osteoporosis. A total of 100 mg/kg melatonin, or solvent alone, was added to the drinking water of the rats over 8 weeks. Perimenopausal rats immediately received intervention following ovariectomy while postmenopausal rats received intervention 8 weeks after ovariectomy. All rats underwent overdose anesthesia following intervention after which blood samples and femurs were collected for further analysis. Rat femurs were scanned using micro-CT and examined histologically. The serum levels of melatonin and osteogenic biochemical markers were measured and the expression of osteogenesis-associated genes (Runx2, Sp7) were quantified by real-time quantitative PCR. Alkaline phosphatase (ALP) activity and the gene expression (Col1a1, Runx2, Alpl, and Bglap) were measured after bone marrow mesenchymal stem cells (BMSCs) were osteogenically induced, both with and without melatonin in vitro. ALP staining and Alizarin Red S staining were used to identify osteogenesis.ResultsAnalysis by micro-CT and histological staining demonstrated that bone mass decreased and bone microarchitecture deteriorated over time after ovariectomy. Intervention with melatonin increased bone mass in normal, perimenopausal, and postmenopausal osteoporotic rats. Serum levels of ALP continuously increased after ovariectomy while osteocalcin levels initially rose, then decreased. Melatonin increased the serum levels of ALP and osteocalcin and mRNA expression levels of Runx2 and Sp7 in normal and postmenopausal rats, the opposite of the markers in perimenopausal rats. In vitro study demonstrated that 100 μmol/L melatonin increased the mRNA expression of Col1a1, Runx2, and Alpl three and/or seven days after intervention, and Alpl and Bglap 14 d after intervention. Melatonin increased ALP activity and the extent of ALP and matrix mineralization in the late stage of osteogenesis.ConclusionsBone mass continuously decreased after ovariectomy, while melatonin increased bone mass and ameliorated bone metabolism in normal, perimenopausal, and postmenopausal osteoporotic rats due to the induction of osteogenic differentiation in BMSCs.

FSH blockade improves cognition in mice with Alzheimer's disease.

Alzheimer's disease has a higher incidence in older women, with a spike in cognitive decline that tracks with visceral adiposity, dysregulated energy homeostasis and bone loss during the menopausal transition1,2. Inhibiting the action of follicle-stimulating hormone (FSH) reduces body fat, enhances thermogenesis, increases bone mass and lowers serum cholesterol in mice3-7. Here we show that FSH acts directly on hippocampal and cortical neurons to accelerate amyloid-β and Tau deposition and impair cognition in mice displaying features of Alzheimer's disease. Blocking FSH action in these mice abrogates the Alzheimer's disease-like phenotype by inhibiting the neuronal C/EBPβ-δ-secretase pathway. These data not only suggest a causal role for rising serum FSH levels in the exaggerated Alzheimer's disease pathophysiology during menopause, but also reveal an opportunity for treating Alzheimer's disease, obesity, osteoporosis and dyslipidaemia with a single FSH-blocking agent.

The Role of NRF2 in Bone Metabolism – Friend or Foe?

Bone metabolism is closely related to oxidative stress. As one of the core regulatory factors of oxidative stress, NRF2 itself and its regulation of oxidative stress are both involved in bone metabolism. NRF2 plays an important and controversial role in the regulation of bone homeostasis in osteoblasts, osteoclasts and other bone cells. The role of NRF2 in bone is complex and affected by several factors, such as its expression levels, age, sex, the presence of various physiological and pathological conditions, as well as its interaction with certains transcription factors that maintain the normal physiological function of the bone tissue. The properties of NRF2 agonists have protective effects on the survival of osteogenic cells, including osteoblasts, osteocytes and stem cells. Activation of NRF2 directly inhibits osteoclast differentiation by resisting oxidative stress. The effects of NRF2 inhibition and hyperactivation on animal skeleton are still controversial, the majority of the studies suggest that the presence of NRF2 is indispensable for the acquisition and maintenance of bone mass, as well as the protection of bone mass under various stress conditions. More studies show that hyperactivation of NRF2 may cause damage to bone formation, while moderate activation of NRF2 promotes increased bone mass. In addition, the effects of NRF2 on the bone phenotype are characterized by sexual dimorphism. The efficacy of NRF2-activated drugs for bone protection and maintenance has been verified in a large number of in vivo and in vitro studies. Additional research on the role of NRF2 in bone metabolism will provide novel targets for the etiology and treatment of osteoporosis.

RNA interference-based osteoanabolic therapy for osteoporosis by a bone-formation surface targeting delivery system

RNA interference (RNAi)-based gene therapy that promotes anabolic bone formation is an effective approach for addressing osteoporosis. However, the selection of target gene and tissue-specific delivery systems has hindered the progression of this strategy. In this study, we identified casein kinase-2 interacting protein-1 encoding gene (Ckip-1), a negative regulator of bone formation, as an effective target of small interfering RNAs (siRNAs) for improving bone mass. Moreover, an impressive (DSS)6-Liposome (Lipos) nanoparticle system that could target the bone formation surface was synthesized to enhance the delivery of Ckip-1 siRNA to osteogenic lineage cells. The in vitro results confirmed that the (DSS)6-Lipos system could efficaciously improve the intracellular delivery of Ckip-1 siRNA without obvious cell toxicity. The in vivo application of the delivery system showed specific accumulation of siRNA in osteogenic cells located around the bone formation surface. Bone-related analysis indicated increased bone mass and improved bone microarchitecture in mice with ovariectomy-induced osteoporosis. Moreover, the biomechanical characteristics of the tibia were enhanced significantly, indicating increased resistance to fragile fracture induced by osteoporosis. Thus, (DSS)6-Lipos-Ckip-1 siRNA-based osteoanabolic therapy may be a promising option for the treatment of osteoporosis.

Serum irisin concentrations and osteoporotic vertebral fractures in women with rheumatoid arthritis: A cross-sectional study.

Irisin stimulates osteoblast differentiation increasing bone mass a decreasing in irisin levels might contribute to osteoporotic fractures in inflammatory diseases. To date, there is controverted whether irisin levels are associated with osteoporotic fractures in rheumatoid arthritis (RA). Therefore, we evaluate the association of serum irisin with osteoporotic Vertebral Fractures (VFs) in women with RA.A total of 148 women with RA was included in the study.Clinical characteristics and risk factors of VFs was evaluated. For measurement of bone mineral density we included the assessment of lumbar spine (AP L1-L4) and Femoral Neck by dual-energy X-ray absorptiometry (DXA). VFs were evaluated by lateral vertebral assessment (LVA) of the dorsal and lumbar regions using X-ray and digital vertebral morphometry by DXA, using the Genant scale. Serum irisin levels were measured by ELISA. A reference group of 97 women with non-rheumatic diseases were included to compare irisin levels.RA patients had a median age of 59 years and 41% had osteoporosis. Seventy three (49%) had VFs. Lower irisin levels were observed in RA patients compared to controls (94 ± 74 vs 135 ± 103, P < .001). Irisin concentrations were lower in RA + VFs than RA non-VFs (74 ± 42 vs 113 ± 92 ng/mL, P = .001). In the multivariable logistic regression analysis the low 50 percentile irisin levels < 73 ng/mL (OR:3.1, 95% CI:1.55–6.2, P = .001), and disease duration of RA (OR:1.04, 95% CI:1.001–1.08, P = .04) were associated with an increase in the risk of VFs.A decrease of irisin levels is associated to VFs in RA. These results are valuable to consider that RA patients with low levels of irisin are in a potential risk of VFs.

Bone structural, biomechanical, and histomorphometric characteristics of the hindlimb skeleton in the marsh rice rat (Oryzomys palustris).

The rice rat (Oryzomys palustris) is a nonconventional laboratory rodent species used to model some human bone disorders. However, no studies have been conducted to characterize the postcranial skeleton. Therefore, we aimed to investigate age- and gender-related features of the hindlimb skeleton of this species. We used femurs and tibiae from 94 rats of both genders aged 4-28 weeks. Bone mineral content (BMC), volumetric bone mineral density (vBMD), and biomechanical properties were determined in femurs. In addition, bone histomorphometry of tibiae was conducted to assess bone cell activities and bone turnover over time. Bone length, total metaphysis BMC and vBMD, mid-diaphyseal BMC and vBMD, cortical thickness, and cortical area progressively augmented with age. Whereas the increase in these parameters plateaued at age 16-22 weeks in female rats, they continued to rise to age 28 weeks in male rats. Furthermore, bone strength parameters increased with age, with few differences between genders. We also observed a rapid decrease in longitudinal growth between age 4 and 16 weeks. Whereas young rats had a greater bone formation rate and bone turnover, older rice rats had greater bone volume and trabecular thickness, with no differences between genders. (a) Sexual dimorphism in the rice rat becomes grossly evident at age 16 weeks; (b) the age-related increases in bone mass, structural cortical parameters, and in some biomechanical property parameters plateau at an older age in male than in female rats; and (c) bone growth and remodeling significantly decreased with age irrespective of the gender.

A recommended amount of hydrolyzed protein improves physiological function by regulating gut microbiota in aged mice

Dietary proteins play a critical role in maintaining the health of elderly people. Although experts recommend that elderly people consume more protein, a high-protein diet may add to the burden of elderly people with degraded digestion and absorption functions. The effects of a normal or high-protein diet and those of a whole or hydrolyzed protein diet on bone and muscle health and gastrointestinal function were evaluated in aged female C57BL/6J mice. The hydrolyzed protein diet with 14.7% protein energy ratio (HNP) contributed to the maintenance of weight and an increase in bone and muscle mass. Further, the overall aging situation was improved by the consumption of this diet. However, the hydrolyzed protein diet with 21.3% protein energy ratio (HHP) increased the levels of LPS, IL-6, IL-10, and TNF-α in serum. Additionally, the small intestine structure was damaged, and the goblet cell number was decreased in the HHP and whole protein with 21.3% protein energy ratio (HP) groups. The relative abundances of Streptococcus and Peptococcus were decreased while that of Bifidobacterium was increased in HNP group compared with the whole protein with 14.7% protein energy ratio (NP) and HP groups. Undigested proteins entering the intestine may cause undesirable changes in gut microbiota, which adversely affect the aging body in NP and HP groups. In summary, hydrolyzed proteins are more advisable than untreated dietary protein in aged mice. This study aimed to provide guidance for daily diet for elderly people, and provide additional information to industry in order to guide their future food development.

The Effects of Signaling-Selective Parathyroid Hormone Analogs on Osteoporotic Osteocyte Apoptosis

Objectives: To compare the effects of signaling-selective parathyroid hormone analogs [G1, R19]hPTH(1–28) [GR(1–28)] and [G1, R19]hPTH(1–34) [GR(1–34)] on osteoporotic osteocyte apoptosis, and to explore the mechanism of the anti-osteoporotic difference. Methods: The osteoporosis model was established in eighty adult female C57BL/6 mice aged 12 weeks. The mice were subcutaneously administered with GR(1–28) and GR(1–34) 5 days per week for 8 weeks. Bilateral femur samples were collected at 4 and 8 weeks, and micro-computed tomography (CT), H&amp;E staining and immunohistochemical staining analyses were performed. Results: From micro-CT analysis, GR(1–34) increased proximal femoral bone mineral density (BMD) and relative bone volume (BV/TV), which was higher than GR(1–28) did. In addition, more trabecular number (Tb.N), thinner trabecular thickness (Tb.Th) and wider trabecular separation (Tb.Sp) were measured at week 8 using GR(1–34). From H&amp;E and immunohistochemical staining, a stronger apoptosis inhibition was induced by GR(1–34) with more Bcl-2 secretion but less Bax expression, as opposed to GR(1–28). Conclusions: GR(1–34) shows better anti-osteoporotic effects than GR(1–28), which appears to be attributed to the activation of the PLC-independent PKC signaling pathway triggered by the former, inhibiting osteocyte apoptosis through up-regulation of Bcl-2 and down-regulation of Bax to increase bone mass and improving trabecular bone microstructure to enhance bone quality by reducing trabecular number, increasing trabecular thickness and trabecular space.

Testosterone supplementation and bone parameters: a systematic review and meta-analysis study.

The role of testosterone (T) replacement therapy (TRT) in subjects with late onset hypogonadism is still the object of an intense debate. All observational studies and placebo-controlled or -uncontrolled randomized trials (RCTs) comparing the effect of TRT on different bone parameters were considered. Out of 349 articles, 36 were considered, including 3103 individuals with a mean trial duration of 66.6weeks. TRT improves areal bone mineral density (aBMD) at the spine and femoral neck levels in observational studies, whereas placebo-controlled RTCs showed a positive effect of TRT only at lumber spine and when trials included only hypogonadal patients at baseline (total testosterone < 12nM). The effects on aBMD were more evident in subjects with lower T levels at baseline and increased as a function of trial duration and a higher prevalence of diabetic subjects. Either T or estradiol increase at endpoint contributed to aBMD improvement. TRT was associated with a significant reduction of bone resorption markers in observational but not in controlled studies. TRT is able to inhibit bone resorption and increase bone mass, particularly at the lumbar spine level and when the duration is long enough to allow the anabolic effect of T and estrogens on bone metabolism to take place.