Loading-induced bone formation is mediated by Wnt1 induction in osteoblast-lineage cells.

Mechanical loading on the skeleton stimulates bone formation. Although the exact mechanism underlying this process remains unknown, a growing body of evidence indicates that the Wnt signaling pathway is necessary for the skeletal response to loading. Recently, we showed that Wnts produced by osteoblast lineage cells mediate the osteo-anabolic response to tibial loading in adult mice. Here, we report that Wnt1 specifically plays a crucial role in mediating the mechano-adaptive response to loading. Independent of loading, short-term loss of Wnt1 in the Osx-lineage resulted in a decreased cortical bone area in the tibias of 5-month-old mice. In females, strain-matched loading enhanced periosteal bone formation in Wnt1F/F controls, but not in Wnt1F/F; OsxCreERT2 knockouts. In males, strain-matched loading increased periosteal bone formation in both control and knockout mice; however, the periosteal relative bone formation rate was 65% lower in Wnt1 knockouts versus controls. Together, these findings show that Wnt1 supports adult bone homeostasis and mediates the bone anabolic response to mechanical loading.

The Association of Pelvic Bone Mineral Density and With Proximal Femoral and Spine Bone Mineral Density in Post-menopausal Women.

Pelvic fragility fractures result in significant morbidity and their incidence has increased over the past 30 years. One of the main risk factors in skeletal fragility is bone mineral density (BMD). Most of the current literature has focused on understanding spine and hip BMD. We aimed to measure the BMD of pelvis in a cohort of post-menopausal women and compare it to BMD at other skeletal sites. A questionnaire regarding risk factors for osteoporosis was completed by each participant. DXA scan of the pelvis was performed using research software. Three areas of the pelvis corresponding to common fractures were defined on pelvic DXA: R1 = symphysis public, R2 = inferior public rami, R3 = superior public rami. Pelvic BMD was calculated as the average BMD of R1-3. BMD at each location was reported as mean and standard deviation (SD). ANOVA was used to compare BMD between R1-R3 and pelvis, femoral neck, total hip, and spine. Pearson correlation was used to correlate pelvic BMD to BMD of proximal femur and spine. BMD was compared in four participant groups: 1- osteoporosis in spine and hip, 2- osteoporosis in spine only, 3-osteoporosis in hip only, and 4- no osteoporosis in spine and hip. The effect of diabetes and obesity on BMD at various skeletal sites was analyzed. Among the one hundred postmenopausal women enrolled in the study, age was: 64 ± 8, 31% were obese (BMI ≥ 30), and 8% had a diagnosis of type 2 diabetes. Pelvic area R3 had significantly higher BMD than R1 or R2 (p < 0.001). Pelvic BMD (0.50 ± 0.16) was significantly lower than total hip (0.70 ± 0.20) and spine BMD (0.97 ± 0.19) (p < 0.001). Pelvic BMD correlated with BMD at other skeletal locations, with the highest correlation with total hip (total hip: R2: 0.70, femoral neck R2: 0.50, spine R2: 0.65). Pelvic BMD was significantly lower in patients with osteoporosis of both hip and spine compared to the group without osteoporosis at both locations (p = 0.02). Obesity and type 2 diabetes were both associated with significantly higher BMD at pelvis, spine, and total hip. Pelvic BMD is lower than at other skeletal sites and is highly correlated with total hip area bone density. Obesity and type 2 diabetes are associated with higher pelvic BMD. To establish guidelines for the treatment pelvic BMD, studies defining the association of pelvic BMD with pelvic fracture risk are needed.

Gasdermin D mediates the pathogenesis of neonatal-onset multisystem inflammatory disease in mice.

Mutated NLRP3 assembles a hyperactive inflammasome, which causes excessive secretion of interleukin (IL)-1ß and IL-18 and, ultimately, a spectrum of autoinflammatory disorders known as cryopyrinopathies of which neonatal-onset multisystem inflammatory disease (NOMID) is the most severe phenotype. NOMID mice phenocopy several features of the human disease as they develop severe systemic inflammation driven by IL-1ß and IL-18 overproduction associated with damage to multiple organs, including spleen, skin, liver, and skeleton. Secretion of IL-1ß and IL-18 requires gasdermin D (GSDMD), which-upon activation by the inflammasomes-translocates to the plasma membrane where it forms pores through which these cytokines are released. However, excessive pore formation resulting from sustained activation of GSDMD compromises membrane integrity and ultimately causes a pro-inflammatory form of cell death, termed pyroptosis. In this study, we first established a strong correlation between NLRP3 inflammasome activation and GSDMD processing and pyroptosis in vitro. Next, we used NOMID mice to determine the extent to which GSDMD-driven pyroptosis influences the pathogenesis of this disorder. Remarkably, all NOMID-associated inflammatory symptoms are prevented upon ablation of GSDMD. Thus, GSDMD-dependent actions are required for the pathogenesis of NOMID in mice.

Connexins in the skeleton.

Shaping of the skeleton (modeling) and its maintenance throughout life (remodeling) require coordinated activity among bone forming (osteoblasts) and resorbing cells (osteoclasts) and osteocytes (bone embedded cells). The gap junction protein connexin43 (Cx43) has emerged as a key modulator of skeletal growth and homeostasis. The skeletal developmental abnormalities present in oculodentodigital and craniometaphyseal dysplasias, both linked to Cx43 gene (GJA1) mutations, demonstrate that the skeleton is a major site of Cx43 action. Via direct action on osteolineage cells, including altering production of pro-osteoclastogenic factors, Cx43 contributes to peak bone mass acquisition, cortical modeling of long bones, and maintenance of bone quality. Cx43 also contributes in diverse ways to bone responsiveness to hormonal and mechanical signals. Skeletal biology research has revealed the complexity of Cx43 function; in addition to forming gap junctions and "hemichannels", Cx43 provides a scaffold for signaling molecules. Hence, Cx43 actively participates in generation and modulation of cellular signals driving skeletal development and homeostasis. Pharmacological interference with Cx43 may in the future help remedy deterioration of bone quality occurring with aging, disuse and hormonal imbalances.

NLRP3 mediates osteolysis through inflammation-dependent and -independent mechanisms.

Activating-mutations in NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) cause neonatal-onset multisystem inflammatory disease. However, the ontogeny of skeletal anomalies in this disorder is poorly understood. Mice globally expressing the D301N mutation in Nlrp3 (D303N in human) model the human phenotype, including systemic inflammation and skeletal deformities. To gain insights into the skeletal manifestations, we generated mice in which the expression of D301N Nlrp3 (Nlrp3( D301N)) is restricted to myeloid cells. These mice exhibit systemic inflammation and severe osteopenia (∼ 60% lower bone mass) similar to mice globally expressing the knock-in mutation, consistent with the paradigm of innate immune-driven cryopyrinopathies. Because systemic inflammation may indirectly affect bone homeostasis, we engineered mice in which Nlrp3( D301N) is expressed specifically in osteoclasts, the cells that resorb bone. These mice also develop ∼ 50% lower bone mass due to increased osteolysis, but there is no systemic inflammation and no change in osteoclast number. Mechanistically, aside from its role in IL-1ß maturation, Nlrp3( D301N) expression enhances osteoclast bone resorbing ability through reorganization of actin cytoskeleton while promoting the degradation of poly(ADP-ribose) polymerase 1, an inhibitor of osteoclastogenesis. Thus, NLRP3 inflammasome activation is not restricted to the production of proinflammatory mediators but also leads to cytokine-autonomous responses.

Balancing benefits and risks of glucocorticoids in rheumatic diseases and other inflammatory joint disorders: new insights from emerging data. An expert consensus paper from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO).

PURPOSE: This consensus review article considers the question of whether glucocorticoid (GC) therapy is still relevant in the treatment of rheumatic diseases, with a particular focus on rheumatoid arthritis (RA), and whether its side effects can be adequately managed. Recent basic and clinical research on the molecular, cellular and clinical effects of GCs have considerably advanced our knowledge in this field. An overview of the subject seems appropriate. METHODS: This review is the result of a multidisciplinary expert working group, organised by European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis. The recent literature was surveyed and the salient evidence synthetized. RESULTS: The pathophysiological basis of RA (and other inflammatory rheumatic diseases) now strongly implicates the adaptive immune system in addition to innate mechanisms. The molecular effect of GCs and differential GC sensitivity is better understood, although exploiting this knowledge is still in its infancy. The newer treatment strategies of early and aggressive control of RA have gr eatly improved clinical outcomes, but improvements are still possible. Newer targeted anti-inflammatory drugs have made an important impact, yet they too are associated with numerous side effects. DISCUSSION: Short durations of moderate doses of GCs are generally well tolerated and have a positive benefit/risk ratio. Patients should be assessed for fracture risk and bone preserving agents and be prescribed calcium and vitamin D supplementation. CONCLUSIONS: Within a strategy of a disease modifying approach to inflammatory disease, combination therapy including a GC is effective approach.

Embryonic ablation of osteoblast Smad4 interrupts matrix synthesis in response to canonical Wnt signaling and causes an osteogenesis-imperfecta-like phenotype.

To examine interactions between bone morphogenic protein (BMP) and canonical Wnt signaling during skeletal growth, we ablated Smad4, a key component of the TGF-ß-BMP pathway, in Osx1(+) cells in mice. We show that loss of Smad4 causes stunted growth, spontaneous fractures and a combination of features seen in osteogenesis imperfecta, cleidocranial dysplasia and Wnt-deficiency syndromes. Bones of Smad4 mutant mice exhibited markers of fully differentiated osteoblasts but lacked multiple collagen-processing enzymes, including lysyl oxidase (Lox), a BMP2-responsive gene regulated by Smad4 and Runx2. Accordingly, the collagen matrix in Smad4 mutants was disorganized, but also hypomineralized. Primary osteoblasts from these mutants did not mineralize in vitro in the presence of BMP2 or Wnt3a, and Smad4 mutant mice failed to accrue new bone following systemic inhibition of the Dickkopf homolog Dkk1. Consistent with impaired biological responses to canonical Wnt, ablation of Smad4 causes cleavage of ß-catenin and depletion of the low density lipoprotein receptor Lrp5, subsequent to increased caspase-3 activity and apoptosis. In summary, Smad4 regulates maturation of skeletal collagen and osteoblast survival, and is required for matrix-forming responses to both BMP2 and canonical Wnt.

Postnatal ablation of osteoblast Smad4 enhances proliferative responses to canonical Wnt signaling through interactions with ß-catenin.

Canonical Wnt (cWnt) signaling through ß-catenin regulates osteoblast proliferation and differentiation to enhance bone formation. We previously reported that osteogenic action of ß-catenin is dependent on BMP signaling. Here, we further examined interactions between cWnt and BMP in bone. In osteoprogenitors stimulated with BMP2, ß-catenin localizes to the nucleus, physically interacts with Smad4, and is recruited to DNA-binding transcription complexes containing Smad4, R-Smad1/5 and TCF4. Furthermore, Tcf/Lef-dependent transcription, Ccnd1 expression and proliferation all increase when Smad4, 1 or 5 levels are low, whereas TCF/Lef activities decrease when Smad4 expression is high. The ability of Smad4 to antagonize transcription of Ccnd1 is dependent on DNA-binding activity but Smad4-dependent transcription is not required. In mice, conditional deletion of Smad4 in osterix(+) cells increases mitosis of cells on trabecular bone surfaces as well as in primary osteoblast cultures from adult bone marrow and neonatal calvaria. By contrast, ablation of Smad4 delays differentiation and matrix mineralization by primary osteoblasts in response to Wnt3a, indicating that loss of Smad4 perturbs the balance between proliferation and differentiation in osteoprogenitors. We propose that Smad4 and Tcf/Lef transcription complexes compete for ß-catenin, thus restraining cWnt-dependent proliferative signals while favoring the matrix synthesizing activity of osteoblasts.

N-cadherin in osteolineage cells is not required for maintenance of hematopoietic stem cells.

There is evidence suggesting that N-cadherin expression on osteoblast lineage cells regulates hematopoietic stem cell (HSC) function and quiescence. To test this hypothesis, we conditionally deleted N-cadherin (Cdh2) in osteoblasts using Cdh2(flox/flox) Osx-Cre mice. N-cadherin expression was efficiently ablated in osteoblast lineage cells as assessed by mRNA expression and immunostaining of bone sections. Basal hematopoiesis is normal in these mice. In particular, HSC number, cell cycle status, long-term repopulating activity, and self-renewal capacity were normal. Moreover, engraftment of wild-type cells into N-cadherin-deleted recipients was normal. Finally, these mice responded normally to G-CSF, a stimulus that mobilizes HSCs by inducing alterations to the stromal micro-environment. In conclusion, N-cadherin expression in osteoblast lineage cells is dispensable for HSC maintenance in mice.

Osteoblastic N-cadherin is not required for microenvironmental support and regulation of hematopoietic stem and progenitor cells.

Hematopoietic stem cell (HSC) regulation is highly dependent on interactions with the marrow microenvironment. Controversy exists on N-cadherin's role in support of HSCs. Specifically, it is unknown whether microenvironmental N-cadherin is required for normal marrow microarchitecture and for hematopoiesis. To determine whether osteoblastic N-cadherin is required for HSC regulation, we used a genetic murine model in which deletion of Cdh2, the gene encoding N-cadherin, has been targeted to cells of the osteoblastic lineage. Targeted deletion of N-cadherin resulted in an age-dependent bone phenotype, ultimately characterized by decreased mineralized bone, but no difference in steady-state HSC numbers or function at any time tested, and normal recovery from myeloablative injury. Intermittent parathyroid hormone (PTH) treatment is well established as anabolic to bone and to increase marrow HSCs through microenvironmental interactions. Lack of osteoblastic N-cadherin did not block the bone anabolic or the HSC effects of PTH treatment. This report demonstrates that osteoblastic N-cadherin is not required for regulation of steady-state hematopoiesis, HSC response to myeloablation, or for rapid expansion of HSCs through intermittent treatment with PTH.

Connexin-43 in the osteogenic BM niche regulates its cellular composition and the bidirectional traffic of hematopoietic stem cells and progenitors.

Connexin-43 (Cx43), a gap junction protein involved in control of cell proliferation, differentiation and migration, has been suggested to have a role in hematopoiesis. Cx43 is highly expressed in osteoblasts and osteogenic progenitors (OB/P). To elucidate the biologic function of Cx43 in the hematopoietic microenvironment (HM) and its influence in hematopoietic stem cell (HSC) activity, we studied the hematopoietic function in an in vivo model of constitutive deficiency of Cx43 in OB/P. The deficiency of Cx43 in OB/P cells does not impair the steady state hematopoiesis, but disrupts the directional trafficking of HSC/progenitors (Ps) between the bone marrow (BM) and peripheral blood (PB). OB/P Cx43 is a crucial positive regulator of transstromal migration and homing of both HSCs and progenitors in an irradiated microenvironment. However, OB/P Cx43 deficiency in nonmyeloablated animals does not result in a homing defect but induces increased endosteal lodging and decreased mobilization of HSC/Ps associated with proliferation and expansion of Cxcl12-secreting mesenchymal/osteolineage cells in the BM HM in vivo. Cx43 controls the cellular content of the BM osteogenic microenvironment and is required for homing of HSC/Ps in myeloablated animals.

Cadherin-mediated cell-cell adhesion and signaling in the skeleton.

Direct cell-to-cell interactions via cell adhesion molecules, in particular cadherins, are critical for morphogenesis, tissue architecture, and cell sorting and differentiation. Partially overlapping, yet distinct roles of N-cadherin (cadherin-2) and cadherin-11 in the skeletal system have emerged from mouse genetics and in vitro studies. Both cadherins are important for precursor commitment to the osteogenic lineage, and genetic ablation of Cdh2 and Cdh11 results in skeletal growth defects and impaired bone formation. While Cdh11 defines the osteogenic lineage, persistence of Cdh2 in osteoblasts in vivo actually inhibits their terminal differentiation and impairs bone formation. The action of cadherins involves both cell-cell adhesion and interference with intracellular signaling, and in particular the Wnt/ß-catenin pathway. Both cadherin-2 and cadherin-11 bind to ß-catenin, thus modulating its cytoplasmic pools and transcriptional activity. Recent data demonstrate that cadherin-2 also interferes with Lrp5/6 signaling by sequestering these receptors in inactive pools via axin binding. These data extend the biologic action of cadherins in bone forming cells, and provide novel mechanisms for development of therapeutic strategies aimed at enhancing bone formation.

Molecular mechanisms of osteoblast/osteocyte regulation by connexin43.

Osteoblasts, osteocytes, and osteoprogenitor cells are interconnected into a functional network by gap junctions formed primarily by connexin43 (Cx43). Over the past two decades, it has become clear that Cx43 is important for the function of osteoblasts and osteocytes. This connexin contributes to the acquisition of peak bone mass and is a major modulator of cortical modeling. We review key data from human and mouse genetics on the skeletal consequences of ablation or mutation of the Cx43 gene (Gja1) and the molecular mechanisms by which Cx43 regulates the differentiation, function, and survival of osteogenic lineage cells. We also discuss putative second messengers that are communicated by Cx43 gap junctions, the role of hemichannels, and the function of Cx43 as a scaffold for signaling molecules. Current knowledge demonstrates that Cx43 is more than a passive channel; rather, it actively participates in the generation and modulation of cellular signals that drive skeletal development and homeostasis.

Connexin43 in mesenchymal lineage cells regulates body adiposity and energy metabolism in mice.

Connexin43 (Cx43) is the most abundant gap junction protein present in the mesenchymal lineage. In mature adipocytes, Cx43 mediates white adipose tissue (WAT) "beiging" in response to cold exposure and maintains the mitochondrial integrity of brown adipose tissue (BAT). We found that genetic deletion of Gja1 (Cx43 gene) in cells that give rise to chondro-osteogenic and adipogenic precursors driven by the Dermo1/Twist2 promoter leads to lower body adiposity and partial protection against the weight gain and metabolic syndrome induced by a high fat diet (HFD) in both sexes. These protective effects from obesogenic diet are related to increased locomotion, fuel utilization, energy expenditure, non-shivering thermogenesis, and better glucose tolerance in conditionally Gja1 ablated mice. Accordingly, Gja1 mutant mice exhibit reduced adipocyte hypertrophy, partially preserved insulin sensitivity, increased BAT lipolysis and decreased whitening under HFD. This metabolic phenotype is not reproduced with more restricted Gja1 ablation in differentiated adipocytes, suggesting that Cx43 has a hitherto unknown function in adipocyte progenitors or other targeted cells, resulting in restrained energy expenditures and fat accumulation. These results disclose an hitherto unknown action of Cx43 in adiposity, and offer a promising new pharmacologic target for improving metabolic balance in diabetes and obesity.

Connexin43 in mesenchymal lineage cells regulates body adiposity and energy metabolism in mice.

Connexin43 (Cx43) is the most abundant gap junction protein present in the mesenchymal lineage. In mature adipocytes, Cx43 mediates white adipose tissue (WAT) beiging in response to cold exposure and maintains the mitochondrial integrity of brown adipose tissue (BAT). We found that genetic deletion of Gja1 (Cx43 gene) in cells that give rise to chondro-osteogenic and adipogenic precursors driven by the Dermo1/Twist2 promoter led to lower body adiposity and partial protection against the weight gain and metabolic syndrome induced by a high-fat diet (HFD) in both sexes. These protective effects were related to increased locomotion, fuel utilization, energy expenditure, nonshivering thermogenesis, and better glucose tolerance in conditionally Gja1-ablated mice. Accordingly, Gja1-mutant mice exhibited reduced adipocyte hypertrophy, partially preserved insulin sensitivity, increased BAT lipolysis, and decreased whitening under HFD. This metabolic phenotype was not reproduced with more restricted Gja1 ablation in differentiated adipocytes, suggesting that Cx43 in adipocyte progenitors or other targeted cells restrains energy expenditures and promotes fat accumulation. These results reveal what we believe is a hitherto unknown action of Cx43 in adiposity, and offer a promising new pharmacologic target for improving metabolic balance in diabetes and obesity.

Bone canonical Wnt signaling is downregulated in type 2 diabetes and associates with higher advanced glycation end-products (AGEs) content and reduced bone strength.

Type 2 diabetes (T2D) is associated with higher fracture risk, despite normal or high bone mineral density. We reported that bone formation genes (SOST and RUNX2) and advanced glycation end-products (AGEs) were impaired in T2D. We investigated Wnt signaling regulation and its association with AGEs accumulation and bone strength in T2D from bone tissue of 15 T2D and 21 non-diabetic postmenopausal women undergoing hip arthroplasty. Bone histomorphometry revealed a trend of low mineralized volume in T2D (T2D 0.249% [0.156-0.366]) vs non-diabetic subjects 0.352% [0.269-0.454]; p=0.053, as well as reduced bone strength (T2D 21.60 MPa [13.46-30.10] vs non-diabetic subjects 76.24 MPa [26.81-132.9]; p=0.002). We also showed that gene expression of Wnt agonists LEF-1 (p=0.0136) and WNT10B (p=0.0302) were lower in T2D. Conversely, gene expression of WNT5A (p=0.0232), SOST (p<0.0001), and GSK3B (p=0.0456) were higher, while collagen (COL1A1) was lower in T2D (p=0.0482). AGEs content was associated with SOST and WNT5A (r=0.9231, p<0.0001; r=0.6751, p=0.0322), but inversely correlated with LEF-1 and COL1A1 (r=-0.7500, p=0.0255; r=-0.9762, p=0.0004). SOST was associated with glycemic control and disease duration (r=0.4846, p=0.0043; r=0.7107, p=0.00174), whereas WNT5A and GSK3B were only correlated with glycemic control (r=0.5589, p=0.0037; r=0.4901, p=0.0051). Finally, Young's modulus was negatively correlated with SOST (r=-0.5675, p=0.0011), AXIN2 (r=-0.5523, p=0.0042), and SFRP5 (r=-0.4442, p=0.0437), while positively correlated with LEF-1 (r=0.4116, p=0.0295) and WNT10B (r=0.6697, p=0.0001). These findings suggest that Wnt signaling and AGEs could be the main determinants of bone fragility in T2D.

Type 2 diabetes is a long-term metabolic disease characterised by chronic high blood sugar levels. This in turn has a negative impact on the health of other tissues and organs, including bones. Type 2 diabetes patients have an increased risk of fracturing bones compared to non-diabetics. This is particularly true for fragility fractures, which are fractures caused by falls from a short height (i.e., standing height or less), often affecting hips or wrists. Usually, a lower bone density is associated with higher risk of fractures. However, patients with type 2 diabetes have increased bone fragility despite normal or higher bone density. One reason for this could be the chronically high levels of blood sugar in type 2 diabetes, which alter the properties of proteins in the body. It has been shown that the excess sugar molecules effectively 'react' with many different proteins, producing harmful compounds in the process, called Advanced Glycation End-products, or AGEs. AGEs are ­ in turn ­thought to affect the structure of collagen proteins, which help hold our tissues together and decrease bone strength. However, the signalling pathways underlying this process are still unclear. To find out more, Leanza et al. studied a signalling molecule, called sclerostin, which inhibits a signalling pathway that regulates bone formation, known as Wnt signaling. The researchers compared bone samples from both diabetic and non-diabetic patients, who had undergone hip replacement surgery. Analyses of the samples, using a technique called real-time-PCR, revealed that gene expression of sclerostin was increased in samples of type 2 diabetes patients, which led to a downregulation of Wnt signaling related genes. Moreover, the downregulation of Wnt genes was correlated with lower bone strength (which was measured by compressing the bone tissue). Further biochemical analysis of the samples revealed that higher sclerostin activity was also associated with higher levels of AGEs. These results provide a clearer understanding of the biological mechanisms behind compromised bone strength in diabetes. In the future, Leanza et al. hope that this knowledge will help us develop treatments to reduce the risk of bone complications for type 2 diabetes patients.

Risedronate increases osteoblastic differentiation and function through connexin43.

Bisphosphonates are potent antiresorptive drugs which have antifracture efficacy by reducing bone turnover rate and increasing bone mineral density. In addition to inhibiting osteoclast function, bisphosphonates have been reported to also promote survival of osteocyte and osteoblast via an anti-apoptotic effect, mediated by opening of hemi-gap junction channels formed by connexin43 (Cx43). In this study, we investigated the effect of risedronate, one amino-bisphosphonate, on osteoblast differentiation and Cx43 expression using the mesenchymal cell line C2C12. Risedronate dose-dependently increased the activity of osterix (OSE)-luciferase containing Runx2 response element with highest activity at 50µM. The activity of osteocalcin (OC)- and bone sialoprotein (BSP)-luciferase reporters, markers of osteoblast differentiation, were also increased by risedronate. When risedronate and BMP2 were used in combination, alkaline phosphatase (ALP) activity increased to a larger extent than when BMP2 was used alone. Risedronate as well as the pro-osteogenic transcription factors, Runx2, Osterix or Dlx5, increased transcriptional activity of the Cx43 promoter in a dose-dependent manner. In the presence of Runx2 or Dlx5, risedronate had an additive effect on Cx43 promoter activity. Accordingly, risedronate increased protein expression of Cx43, Runx2, Osterix, and Dlx5. These results suggest that risedronate promotes osteoblastic differentiation and positively regulates Cx43 gene transcription.

Sex- and race-specific associations of bone mineral density with incident heart failure and its subtypes in older adults.

BACKGROUND: Previous studies have suggested an association between bone mineral density (BMD) and heart failure (HF) risk that may be race-dependent. METHODS: We evaluated the relationship between BMD and incident HF in a cohort of older adults, the Health, Aging, and Body Composition (Health ABC) study (n = 2835), and next performed a pooled analysis involving a second older cohort, the Cardiovascular Health Study (n = 1268). Hip BMD was measured by dual-energy X-ray absorptiometry in both cohorts and spine BMD by computed tomography in a subset from Health ABC. RESULTS: In Health ABC, lower BMD at the total hip was associated with higher incident HF in Black women after multivariable adjustment. Similar associations were found for BMD at the femoral neck and spine. In both cohorts, pooled analysis again revealed an association between lower total hip BMD and increased risk of HF in Black women (HR = 1.41 per 0.1-g/cm2 decrement [95% CI = 1.23-1.62]), and showed the same to be true for White men (HR = 1.12 [1.03-1.21]). There was a decreased risk of HF in Black men (HR 0.80 [0.70-0.91]), but no relationship in White women. The associations were numerically stronger with HFpEF for Black women and White men, and with HFrEF for Black men. Findings were similar for femoral neck BMD. Sensitivity analyses delaying HF follow-up by 2 years eliminated the association in Black men. CONCLUSIONS: Lower BMD was associated with higher risk of HF and especially HFpEF in older Black women and White men, highlighting the need for additional investigation into underlying mechanisms.

N-cadherin and cadherin 11 modulate postnatal bone growth and osteoblast differentiation by distinct mechanisms.

We have previously shown that targeted expression of a dominant-negative truncated form of N-cadherin (Cdh2) delays acquisition of peak bone mass in mice and retards osteoblast differentiation; whereas deletion of cadherin 11 (Cdh11), another osteoblast cadherin, leads to only modest osteopenia. To determine the specific roles of these two cadherins in the adult skeleton, we generated mice with an osteoblast/osteocyte specific Cdh2 ablation (cKO) and double Cdh2(+/-);Cdh11(-/-) germline mutant mice. Age-dependent osteopenia and smaller diaphyses with decreased bone strength characterize cKO bones. By contrast, Cdh2(+/-);Cdh11(-/-) exhibit severely reduced trabecular bone mass, decreased in vivo bone formation rate, smaller diaphyses and impaired bone strength relative to single Cdh11 null mice. The number of bone marrow immature precursors and osteoprogenitor cells is reduced in both cKO and Cdh2(+/-);Cdh11(-/-) mice, suggesting that N-cadherin is involved in maintenance of the stromal cell precursor pool via the osteoblast. Although Cdh11 is dispensable for postnatal skeletal growth, it favors osteogenesis over adipogenesis. Deletion of either cadherin reduces ß-catenin abundance and ß-catenin-dependent gene expression, whereas N-cadherin loss disrupts cell-cell adhesion more severely than loss of cadherin 11. Thus, Cdh2 and Cdh11 are crucial regulators of postnatal skeletal growth and bone mass maintenance, serving overlapping, yet distinct, functions in the osteogenic lineage.

Gender and Geographic Origin as Determinants of Manuscript Publication Outcomes: JBMR® Bibliometric Analysis from 2017 to 2019.

The Journal of Bone and Mineral Research (JBMR®), the flagship journal of the American Society for Bone and Mineral Research (ASBMR), enjoys a premiere position in its field and has a global reach. The journal uses a single-blind peer-review process whereby three editors are typically involved in assessing each submission for publication, in addition to external reviewers. Although emphasizing fairness, rigor, and transparency, this process is not immune to the influence of unconscious biases. The gender and geographic diversity of JBMR® authors, editors, and reviewers has increased over the last three decades, but whether such diversity has affected peer-review outcomes is unknown. We analyzed manuscript acceptance rates based on the gender and geographic origin of authors, reviewers, and Associate Editors. The analysis included 1662 original research articles submitted to JBMR® from September 2017 through December 2019. Gender was assigned using probabilities from an online tool and manually validated through internet searches. Predictor variables of manuscript outcome were determined with multivariate logistic regression analysis. The acceptance rate was highest when the first and last authors were of different genders, and lowest when both authors were men. Reviewer gender did not influence the outcome regardless of the genders of the first and last authors. Associate Editors from all geographical regions tended to select reviewers from their same region. The acceptance rate was highest when the Associate Editor was from Europe. Manuscripts with authors from North America and Australia/New Zealand had greater overall odds of acceptance than those from Europe and Asia. Manuscripts reviewed only by Editorial Board (EB) members had a lower acceptance rate than those refereed by non-EB reviewers or a mix of EB and non-EB reviewers. Overall, the geographical origin of authors, reviewers, and editors, as well as reviewers' EB membership may influence manuscript decisions. Yet, the JBMR® peer-review process remains largely free from gender bias. © 2022 American Society for Bone and Mineral Research (ASBMR).