Periostin expression contributes to cortical bone loss during unloading

Cathepsin K Controls Cortical Bone Formation by Degrading Periostin

Although inhibitors of bone resorption concomitantly reduce bone formation because of the coupling between osteoclasts and osteoblasts, inhibition or deletion of cathepsin k (CatK) stimulates bone formation despite decreasing resorption. The molecular mechanisms responsible for this increase in bone formation, particularly at periosteal surfaces where osteoclasts are relatively poor, remain unclear. Here we show that CatK pharmacological inhibition or deletion (Ctsk^-/- mice) potentiates mechanotransduction signals mediating cortical bone formation. We identify periostin (Postn) as a direct molecular target for degradation by CatK and show that CatK deletion increases Postn and β-catenin expression in vivo, particularly at the periosteum. In turn, Postn deletion selectively abolishes cortical, but not trabecular, bone formation in CatK-deficient mice. Taken together, these data indicate that CatK not only plays a major role in bone remodeling but also modulates modeling-based cortical bone formation by degrading periostin and thereby moderating Wnt-β-catenin signaling. These findings provide novel insights into the role of CatK on bone homeostasis and the mechanisms of increased cortical bone volume with CatK mutations and pharmacological inhibitors. © 2017 American Society for Bone and Mineral Research.

Irisin prevents and restores bone loss and muscle atrophy in hind-limb suspended mice

We previously showed that Irisin, a myokine released from skeletal muscle after physical exercise, plays a central role in the control of bone mass. Here we report that treatment with recombinant Irisin prevented bone loss in hind-limb suspended mice when administered during suspension (preventive protocol) and induced recovery of bone mass when mice were injected after bone loss due to a suspension period of 4 weeks (curative protocol). MicroCT analysis of femurs showed that r-Irisin preserved both cortical and trabecular bone mineral density, and prevented a dramatic decrease of the trabecular bone volume fraction. Moreover, r-Irisin protected against muscle mass decline in the hind-limb suspended mice, and maintained the fiber cross-sectional area. Notably, the decrease of myosin type II expression in unloaded mice was completely prevented by r-Irisin administration. Our data reveal for the first time that Irisin retrieves disuse‐induced bone loss and muscle atrophy. These findings may lead to development of an Irisin-based therapy for elderly immobile osteoporotic and physically disable patients, and might represent a countermeasure for astronauts subjected to microgravity-induced bone and muscle losses.

Influence of Mechanical Force on Bone Matrix Proteins in Ovariectomised Mice and Osteoblast-like MC3T3-E1 Cells

AIM

To investigate the effect of mechanical stress on periostin and semaphorin-3A expression in a murine model of postmenopausal osteoporosis and in osteoblast-like MC3T3-E1 cells.

MATERIALS AND METHODS

Female mice were divided into three groups and treated with a sham operation, ovariectomy (OVX) or OVX plus treadmill training (OVX+Run). After 10 weeks, tibias were used for histological analysis. MC3T3-E1 cells were burdened by mechanical stress using a centrifuge or were treated with periostin, and the production of biologically-active semaphorin-3A was examined in vitro.

RESULTS

In OVX+Run group tibias, the number of tartrate-resistant acid phosphatase-positive osteoclasts was lower than in the OVX group, and the expression of periostin and semaphorin-3A was higher. In MC3T3-E1 cells, centrifugal stress significantly increased periostin and semaphorin-3A mRNA expression. Treatment with periostin increased the semaphorin-3A level.

CONCLUSION

We speculate that mechanical load may increase periostin production in osteoblasts, and periostin may inhibit osteoclast differentiation by its effects on semaphorin-3A. Our results support the concept of a positive correlation between exercise and inhibition of osteoclasts in post-menopausal osteoporosis.

Intra- and Interskeletal Proteome Variations in Fresh and Buried Bones

Proteomic methods are acquiring greater importance in archaeology and palaeontology due to the longevity of proteins in skeletal remains. There are also developing interests in forensic applications, offering the potential to shed light on post-mortem intervals and age at death estimation. However, our understanding of intra- and interskeletal proteome variations is currently severely limited. Here, we evaluated the proteomes obtained from five distinct subsamples of different skeletal elements from buried pig carcasses to ascertain the extent of variation within and between individuals. We found that reproducibility of data depends on the skeletal element used for sampling and that intrabone differences exceed those observed between the same skeletal element sampled from different individuals. Interestingly, the abundance of several serum proteins appeared to correlate with biological age with relative concentrations of alpha-1 antitrypsin and chromogranin-A increasing and those of fetuin-A decreasing. We also observed a surprising level of divergence in data from different LC-MS/MS runs on aliquots of similar samples analyzed months apart, adding constraints to the comparison of results of such methods across different studies.

Periostin: The bone and beyond

In recent years the relationship between bone, metabolism and many pathophysiologic mechanisms involving other organs and the immune system, was increasingly apparent. This observation concerns vitamin D, osteopontin and periostin (PO). PO is expressed in the periosteum of long bones but also in many other tissues and organs, including heart, kidney, skin and lungs, being enhanced by mechanical stress or injury. PO has a relevant physiological function in promoting injury repair in a large number of tissues. However, its overexpression was observed in different diseases characterized by inflammation, fibrosis and tumorigenesis. Here we review the current knowledge on the role of PO in physiologic and pathologic pathways of different diseases. A specific focus regards the correlation between the level of PO and lung diseases and the identification of PO also as an inflammatory key effector in asthma, strongly associated with airways eosinophilia. In fact PO seems to be a useful biomarker of "Th2-high" asthma compared to "Th2-low" asthma phenotype and a predictor of response to therapeutic agents. Currently, a growing number of studies suggests a possible role of PO as a new diagnostic marker and/or therapeutic target for different diseases and its usefulness in clinical practice should be supported and confirmed by further and larger studies.

Repeated irradiation from micro-computed tomography scanning at 2, 4 and 6 months of age does not induce damage to tibial bone microstructure in male and female CD-1 mice

Long-term effects of repeated in vivo micro-computed tomography (μCT) scanning at key stages of growth and bone development (ages 2, 4 and 6 months) on trabecular and cortical bone structure, as well as developmental patterns, have not been studied. We determined the effect of repetitive μCT scanning at age 2, 4 and 6 months on tibia bone structure of male and female CD-1 mice and characterized developmental changes. At 2, 4 and 6 months of age, right tibias were scanned using in vivo μCT (Skyscan 1176) at one of three doses of radiation per scan: 222, 261 or 460 mGy. Left tibias of the same mice were scanned only at 6 months to serve as non-irradiated controls to determine whether recurrent radiation exposure alters trabecular and cortical bone structure at the proximal tibia. In males, eccentricity was lower (P<0.05) in irradiated compared with non-irradiated tibias (222 mGy group). Within each sex, all other structural outcomes were similar between irradiated and non-irradiated tibias regardless of dose. Trabecular bone loss occurred in all mice due to age while cortical development continued to age 6 months. In conclusion, repetitive μCT scans at various radiation doses did not damage trabecular or cortical bone structure of proximal tibia in male and female CD-1 mice. Moreover, scanning at 2, 4 and 6 months of age highlight the different developmental time course between trabecular and cortical bone. These scanning protocols can be used to investigate longitudinal responses of bone structures to an intervention.

Periostin action in bone

Periostin is a highly conserved matricellular protein that shares close homology with the insect cell adhesion molecule fasciclin 1. Periostin is expressed in a broad range of tissues including the skeleton, where it serves both as a structural molecule of the bone matrix and a signaling molecule through integrin receptors and Wnt-beta-catenin pathways whereby it stimulates osteoblast functions and bone formation. The development of periostin null mice has allowed to elucidate the crucial role of periostin on dentinogenesis and osteogenesis, as well as on the skeletal response to mechanical loading and parathyroid hormone. The use of circulating periostin as a potential clinical biomarker has been explored in different non skeletal conditions. These include cancers and more specifically in the metastasis process, respiratory diseases such as asthma, kidney failure, renal injury and cardiac infarction. In postmenopausal osteoporosis, serum levels have been shown to predict the risk of fracture-more specifically non-vertebral- independently of bone mineral density. Because of its preferential localization in cortical bone and periosteal tissue, it can be speculated that serum periostin may be a marker of cortical bone metabolism, although additional studies are clearly needed.

The impact of microgravity on bone in humans

Experiencing real weightlessness in space is a dream for many of us who are interested in space research. Although space traveling fascinates us, it can cause both short-term and long-term health problems. Microgravity is the most important influence on the human organism in space. The human body undergoes dramatic changes during a long-term spaceflight. In this review, we will mainly focus on changes in calcium, sodium and bone metabolism of space travelers. Moreover, we report on the current knowledge on the mechanisms of bone loss in space, available models to simulate the effects of microgravity on bone on Earth as well as the combined effects of microgravity and cosmic radiation on bone. The available countermeasures applied in space will also be evaluated.

Osteogenic Potential of Human Oral-Periosteal Cells (PCs) Isolated From Different Oral Origin: An In Vitro Study

The periosteum is a specialized connective tissue containing multipotent stem cells capable of bone formation. In this study, we aimed at demonstrating that human oral periosteal cells derived from three different oral sites (upper vestibule, lower vestibule, and hard palate) represent an innovative cell source for maxillo-facial tissue engineering applications in terms of accessibility and self-commitment towards osteogenic lineage. Periosteal cells (PCs) were isolated from patients with different ages (20-30 yy, 40-50 yy, 50-60 yy); we then analyzed the in vitro proliferation capacity and the bone self-commitment of cell clones culturing them without any osteogenic supplement to support their differentiation. We found that oral PCs, independently of their origin and age of patients, are mesenchymal stem cells with stem cell characteristics (clonogenical and proliferative activity) and that, even in absence of any osteogenic induction, they undertake the osteoblast lineage after 45 days of culture. These results suggest that oral periosteal cells could replace mesenchymal cells from bone marrow in oral tissue-engineering applications.

Periostin: A Downstream Mediator of EphB4-Induced Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Erythropoietin-producing hepatocyte B4 (EphB4) has been reported to be a key molecular switch in the regulation of bone homeostasis, but the underlying mechanism remains poorly understood. In this study, we investigated the role of EphB4 in regulating the expression of periostin (POSTN) within bone marrow-derived mesenchymal stem cells (MSCs) and assessed its effect and molecular mechanism of osteogenic induction in vitro. Treatment with ephrinB2-FC significantly increased the expression of POSTN in MSCs, and the inhibition of EphB4 could abrogate this effect. In addition, osteogenic markers were upregulated especially in MSCs overexpressing EphB4. To elucidate the underlying mechanism of cross talk between EphB4 and the Wnt pathway, we detected the change in protein expression of phosphorylated-glycogen synthase kinase 3β-serine 9 (p-GSK-3β-Ser9) and β-catenin, as well as the osteogenic markers Runx2 and COL1. The results showed that GSK-3β activation and osteogenic marker expression levels were downregulated by ephrinB2-FC treatment, but these effects were inhibited by blocking integrin αvβ3 in MSCs. Our findings demonstrate that EphB4 can promote osteogenic differentiation of MSCs via upregulation of POSTN expression. It not only helps to reveal the interaction mechanism between EphB4 and Wnt pathway but also brings a better understanding of EphB4/ephrinB2 signaling in bone homeostasis.

Plasma periostin associates significantly with non-vertebral but not vertebral fractures in postmenopausal women: Clinical evidence for the different effects of periostin depending on the skeletal site

BACKGROUND

Periostin is preferentially expressed by the periosteum, which mainly covers the long bones. Therefore, the role of periostin in osteoporotic fracture (OF) may differ depending on bone type. We performed a case-control study to investigate whether periostin can serve as a predictor of OF risk, particularly after dividing OFs into non-vertebral and vertebral fractures.

METHODS

Among 532 consecutive postmenopausal women not taking any drug or without any disease that could affect bone metabolism, 133 cases with OF (i.e., non-vertebral and/or vertebral fractures) and 133 age- and body mass index-matched controls were enrolled. Non-vertebral (i.e., forearm, humerus, hip, and pelvis; n=81) and morphological vertebral (n=62) fractures were identified by an interviewer-assisted questionnaire and lateral thoracolumbar radiographs, respectively. Bone mineral density (BMD) and plasma periostin levels were also measured.

RESULTS

Plasma periostin was markedly higher in subjects with non-vertebral fracture than their controls even after adjustment for BMD and potential confounders (P=0.006). Each standard deviation increment of plasma periostin was associated with a multivariable-adjusted odds ratio of 1.59 for non-vertebral fracture. The odds for non-vertebral fracture were 2.48-fold higher in subjects in the highest periostin tertile compared with those in the lowest periostin tertile (95% confidence interval=1.10-5.61). However, associations between plasma periostin and vertebral fracture were not observed, regardless of the adjustment model used. Consistently, plasma periostin levels were inversely associated with proximal femur BMD (P=0.007 to 0.030) but not lumbar spine BMD. In subgroup analyses, plasma periostin had no correlation with the levels of classical bone turnover markers.

CONCLUSIONS

Plasma periostin may be a potential biomarker of the risk of OF, especially in non-spinal skeletal sites, such as the limbs, rather than spine.

Involvement of periostin-sclerostin-Wnt/β-catenin signaling pathway in the prevention of neurectomy-induced bone loss by naringin

Periostin has an essential role in mechanotransduction in bone. Naringin, a natural flavonoid, has been evidenced for its osteoprotective role in osteoporosis, while its mechanism is far from clear. Here we show that down-regulation of periostin, and up-regulation of its downstream sclerostin and inactivation of Wnt/β-catenin signaling were implicated in neurectomy-induced bone loss. Naringin could up-regulate periostin and prevent neurectomy-induced deterioration of BMD, trabecular microstructure and bone mechanical characteristics. In conclusion, naringin could prevent progress of disuse osteoporosis in rats, which may be mediated by increased periostin expression and subsequently inhibition of sclerostin and activation of Wnt/β-catenin signaling pathways.

Maternal High Fat Diet Affects Offspring's Vitamin K-Dependent Proteins Expression Levels

Studies suggest bone growth & development and susceptibility to vascular disease in later life are influenced by maternal nutrition, during intrauterine and early postnatal life. There is evidence for a role of vitamin K-dependent proteins (VKDPs) including Osteocalcin, Matrix-gla protein, Periostin, and Gas6, in bone and vascular development. This study extends the analysis of VKDPs previously conducted in 6 week old offspring, into offspring of 30 weeks of age, to assess the longer term effects of a maternal and postnatal high fat (HF) diet on VKDP expression. Overall a HF maternal diet and offspring diet exacerbated the bone changes observed. Sex specific and tissue specific differences were observed in VKDP expression for both aorta and femoral tissues. In addition, significant correlations were observed between femoral OCN, Periostin Gas6, and Vkor expression levels and measures of femoral bone structure. Furthermore, MGP, OCN, Ggcx and Vkor expression levels correlated to mass and fat volume, in both sexes. In summary the current study has highlighted the importance of the long-term effects of maternal nutrition on offspring bone development and the correlation of VKDPs to bone structure.