Development of a new ELISA for serum periostin: evaluation of growth-related changes and bisphosphonate treatment in mice

Association of Serum Periostin Level with Classical Bone Turnover Markers and Bone Mineral Density in Shanghai Chinese Postmenopausal Women with Osteoporosis

Background

It has been reported that serum periostin levels are significantly higher in postmenopausal patients with osteoporotic fractures. Nonetheless, the levels of serum periostin in postmenopausal women with different bone mass remain unclear.

Purpose

The objective of the study was to identify the levels of serum periostin in Chinese postmenopausal women with different bone mass, and the correlations between the periostin levels and the classical bone turnover markers (BTMs), and bone mineral densities (BMDs) at different sites.

Patients and Methods

This study enrolled 331 Chinese postmenopausal women in Shanghai; their clinical features were collected; their levels of serum periostin and traditional BTMs were measured by ELISA or the fully automated immunoassay analyzer; their BMDs at different sites were measured by dual-energy X-ray absorptiometry (DXA).

Results

According to the T-value of bone mineral density (BMD), these postmenopausal women were divided into normal group (n=84), osteopenia group (n=126) and osteoporosis group (n=121). There was no significant difference in the serum periostin levels among the above three groups of subjects. In addition, Spearman correlation analysis also revealed that no correlation was observed between the value of serum periostin and those of traditional BTMs, and BMDs at different sites, respectively. The values of traditional BTMs were negatively correlated with those of BMDs at all measured sites. Furthermore, the receiver-operating characteristic (ROC) curves analysis indicated that among the periostin and traditional BTMs mentioned above, the best predictors for postmenopausal osteoporosis in Shanghai Chinese postmenopausal women were osteocalcin (OC) and procollagen type 1 N-terminal propeptide (P1NP) [the areas under the ROC curve (AUC)=0.746 and 0.761, respectively].

Conclusion

Serum periostin may not be used as a marker of systemic bone metabolism in Shanghai Chinese postmenopausal women without prior fracture. In addition, serum P1NP and OC levels may be the predictors of osteoporosis occurrence in Chinese postmenopausal women.

RANKL-Induced Increase in Cathepsin K Levels Restricts Cortical Expansion in a Periostin-Dependent Fashion: A Potential New Mechanism of Bone Fragility

Receptor activator of nuclear factor-κΒ ligand (RANKL) is necessary and sufficient to promote osteoclastogenesis and a key pathogenic factor in osteoporosis. Failure of periosteal apposition to compensate for bone loss due to endosteal resorption further contributes to bone fragility. Whether these two processes are biologically related, however, remains unknown. Using high-resolution peripheral quantitative computed tomography (HR-pQCT), we first examined cortical bone parameters at distal radius and tibia in postmenopausal women (PMW) as well as in cadaveric human adult humeri. Increases in medullary area were negatively correlated with cortical bone volume but positively with total bone volume, and this relationship was stronger in the dominant arm, suggesting a mechanically driven process. To investigate the role of RANKL in this dual process, we used mice overexpressing huRANKL (huRANKLTg⁺ ). Trabecular and cortical bone volume (Ct.BV) are reduced in these mice, whereas cortical total volume (Ct.TV) is increased. In these bones, Sost mRNA levels are downregulated and periostin (Postn) mRNA levels upregulated, hence providing a positive message for periosteal bone formation. In turn, genetic deletion of Postn in huRANKLTg⁺  mice prevented the increase in Ct.TV and aggravated bone fragility. In contrast, cathepsin K (Ctsk) ablation improved Ct.TV in both huRANKLTg⁺  and wild-type (WT) mice and stimulated periosteal bone formation, while augmenting Postn protein levels. Therefore, bone strength in huRANKLTg⁺ /Ctsk^-/- mice was restored to WT levels. These findings suggest that high levels of RANKL not only induce endosteal bone loss but may somewhat restrict periosteal bone formation by triggering periostin degradation through cathepsin K, hence providing a biological mechanism for the observed limited increase in cortical area in postmenopausal women. © 2021 American Society for Bone and Mineral Research (ASBMR).

Zoledronic acid modulates osteoclast apoptosis through activation of the NF-κB signaling pathway in ovariectomized rats

Bone mass loss (osteoporosis) seen in postmenopausal women is an adverse factor for implant denture. Using an ovariectomized rat model, we studied the mechanism of estrogen-deficiency-caused bone loss and the therapeutic effect of Zoledronic acid. We observed that ovariectomized-caused resorption of bone tissue in the mandible was evident at four weeks and had not fully recovered by 12 weeks post-ovariectomized compared with the sham-operated controls. Further evaluation with a TUNEL assay showed ovariectomized enhanced apoptosis of osteoblasts but inhibited apoptosis of osteoclasts in the mandible. Zoledronic acid given subcutaneously as a single low dose was shown to counteract both of these ovariectomized effects. Immunohistochemical staining showed that ovariectomized induced the protein levels of RANKL and the 65-kD subunit of the NF-κB complex mainly in osteoclasts, as confirmed by staining for TRAP, a marker for osteoclasts, whereas zoledronic acid inhibited these inductions. Western blotting showed that the levels of RANKL, p65, as well as the phosphorylated form of p65, and IκB-α were all higher in the ovariectomized group than in the sham and ovariectomized + zoledronic acid groups at both the 4th- and 12th-week time points in the mandible. These data collectively suggest that ovariectomized causes bone mass loss by enhancing apoptosis of osteoblasts and inhibiting apoptosis of osteoclasts. In osteoclasts, these cellular effects may be achieved by activating RANKL-NF-κB signalling. Moreover, zoledronic acid elicits its therapeutic effects in the mandible by counteracting these cellular and molecular consequences of ovariectomized.

Plasma periostin as a biomarker of osteoporosis in postmenopausal women with type 2 diabetes

INTRODUCTION

Periostin, as an emerging biomarker, is involved in multiple steps in bone metabolism. This study aimed to investigate the correlation between periostin levels and bone mineral density as well as bone turnover markers in postmenopausal women with type 2 diabetes (T2DM).

MATERIALS AND METHODS

This study was a cross-sectional study that included 164 postmenopausal women with T2DM as study subjects and 32 age-matched nondiabetic postmenopausal women with normal bone mineral density (BMD) as healthy control subjects. A total of 164 subjects with T2DM were then divided into three groups according to BMD: the normal BMD group (n = 29), the osteopenia group (n = 70), and the osteoporosis group (n = 65). The clinical data of all subjects along with the relevant biochemical parameter data were collected. Plasma periostin was detected using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Plasma periostin levels were significantly increased in T2DM patients with normal BMD compared with healthy controls (p < 0.05). In the diabetic group, plasma periostin levels were significantly elevated with decreased BMD, were positively correlated with osteocalcin levels (r = 0.162, p = 0.039) and were inversely associated with femoral neck BMD (r = - 0.308, p < 0.001) and total femur BMD (r = - 0.295, p < 0.001). In the case of chronic complications, periostin levels were slightly increased in individuals with complications of diabetic retinopathy, diabetic nephropathy and fracture (p > 0.05).

CONCLUSIONS

The current study demonstrated that plasma periostin levels were significantly associated with BMD in patients with T2DM, and periostin might act as a novel biochemical marker of osteoporosis in postmenopausal women with type 2 diabetes.

Serum periostin levels and severity of fibrous dysplasia of bone

Fibrous dysplasia of bone (FD) is a rare congenital bone disease, characterized by a fibrous component in the bone marrow. Periostin has been extensively researched because of its implication in various fibrotic or inflammatory diseases. Periostin may be associated with the burden or the severity of FD. The case control PERIOSDYS study aimed at assessing serum periostin levels in FD patients. Sixty four patients with monostotic or polyostotic disease were included, in order to evaluate whether the concentrations were greater in patients than in 128 healthy age, BMI and sex-matched controls and if they were more elevated in patients with the more severe phenotypes. We found that periostin levels were greater in patients with FD compared to controls (mean = 1085 vs 958 pmol/l, p = 0.026), especially in those with a history of fracture (mean = 1475 vs 966 pmol/l, p = 0.0005), polyostotic forms (mean = 1214 vs 955 pmol/l, p = 0.004) or McCune-Albright syndrome (mean = 1585 vs 1023 pmol/l, p = 0.0048). In contrast, high pain levels were not associated with periostin levels (mean = 1137 vs 1036 pmol/l, p = 0.445). Furthermore, patients undergoing bisphosphonate therapy had significantly lower levels than treatment naïve patients (mean = 953 vs 1370 pmol/l, p = 0.002). In conclusion, periostin may be a biochemical marker indicative of the most severe forms of FD and could be used to monitor patients treated with bisphosphonates.

Practical Application of Periostin as a Biomarker for Pathological Conditions

In physiological condition, periostin is expressed in limited tissues such as periodontal ligament, periosteum, and heart valves. Periostin protein is mainly localized on extracellular collagen bundles and in matricellular space. On the other hand, in pathological condition, expression of periostin is induced in disordered tissues of human patients. In tumor development and progression, periostin is elevated mainly in its microenvironment and stromal tissue rich in extracellular matrix. Tumor stromal fibroblasts highly express periostin and organize the tumor-surrounding extracellular matrix architecture. In fibrosis in lung, liver, and kidney, proliferating activated fibroblasts express periostin and replace normal functional tissues with dense connective tissues. In inflammation and allergy, inflammatory cytokines such as IL-4 and IL-13 induce expression of periostin that plays important roles in pathogenesis of these diseases. The elevated levels of periostin in human patients could be detected not only in tissue biopsy samples but also in peripheral bloods using specific antibodies against periostin, because periostin secreted from the disordered tissues is transported into blood vessels and circulates in the cardiovascular system. In this chapter, I introduce the elevated expression of periostin in pathological conditions, and discuss how periostin could be utilized as a biomarker in disease diagnosis.

The C-Terminal Intact Forms of Periostin (iPTN) Are Surrogate Markers for Osteolytic Lesions in Experimental Breast Cancer Bone Metastasis

Periostin is an extracellular matrix protein that actively contributes to tumor progression and metastasis. Here, we hypothesized that it could be a marker of bone metastasis formation. To address this question, we used two polyclonal antibodies directed against the whole molecule or its C-terminal domain to explore the expression of intact and truncated forms of periostin in the serum and tissues (lung, heart, bone) of wild-type and periostin-deficient mice. In normal bones, periostin was expressed in the periosteum and specific periostin proteolytic fragments were found in bones, but not in soft tissues. In animals bearing osteolytic lesions caused by 4T1 cells, C-terminal intact periostin (iPTN) expression disappeared at the invasive front of skeletal tumors where bone-resorbing osteoclasts were present. In vitro, we found that periostin was a substrate for osteoclast-derived cathepsin K, generating proteolytic fragments that were not recognized by anti-periostin antibodies directed against iPTN. In vivo, using an in-house sandwich immunoassay aimed at detecting iPTN only, we observed a noticeable reduction of serum periostin levels (- 26%; P < 0.002) in animals bearing osteolytic lesions caused by 4T1 cells. On the contrary, this decrease was not observed in women with breast cancer and bone metastases when periostin was measured with a human assay detecting total periostin. Collectively, these data showed that mouse periostin was degraded at the bone metastatic sites, potentially by cathepsin K, and that the specific measurement of iPTN in serum should assist in detecting bone metastasis formation in breast cancer.

Tumor suppression effect of targeting periostin with siRNA in a nude mouse model of human laryngeal squamous cell carcinoma

BACKGROUND

The incidence of laryngeal carcinoma is increasing, however, the mechanism is not fully understood. We aimed to investigate the efficacy of periostin gene silencing by siRNA on tumor inhibition, in a novel nude mouse model of human laryngeal squamous cell carcinoma, and to explore possible inhibitory mechanisms.

METHODS

Tumors were established in nude mice by transplantation of LSCC AMC-HN-8 cell line. Forty-eight nude mice were randomly divided into groups of eight each, and treated with high (1.0 OD) or low (0.5 OD) doses of periostin-siRNA or appropriate control solutions. Tumor growth was observed and used to calculate an inhibition rate (%). Routine pathological and electron microscopic examination were used to determine tumor apoptosis and proliferation. Changes in periostin mRNA and protein levels were analyzed.

RESULTS

Tumor growth was significantly inhibited in mice treated by high dose periostin-siRNA compared to untreated and those treated with low dose periostin-siRNA (P < 0.05). Pathological examination showed increased tumor necrosis and apoptotic changes in treated mice, which was confirmed by electron microscopy. Periostin mRNA and protein expression were significantly reduced in tumors from mice treated with high dose periostin-siRNA, compared to controls and low-dose periostin-siRNA treatment groups (P < 0.05).

CONCLUSION

Periostin silencing was associated with growth inhibition of tumor cells in a nude mouse model of LSCC. The underlying mechanism may be due to receptor-mediated induction of relevant signal transduction pathways that modulate the microenvironment needed for cancer cell survival. Periostin is expected to become a new target for cancer therapy.

Development of a New Immunoassay for Human Cathepsin K-Generated Periostin Fragments as a Serum Biomarker for Cortical Bone

Periostin is a matricellular protein mainly expressed by periosteal cells and osteocytes in bone, but is also present in several other tissues. Available immunoassays use antibodies of unclear specificity. The aim of the study was to develop a bone-specific periostin ELISA based on the detection of fragments generated by the osteoclastic and osteocytic protease cathepsin K. In vitro digestion of human recombinant intact periostin by cathepsin K leads to the generation of multiple fragments. Using LS-MS/MS, it was found that the GSLQPIIK peptide was the most efficiently and abundantly generated periostin fragment. A rabbit polyclonal antibody directed against the synthetic GSLQPIIK sequence was produced. Immunohistochemistry experiments of the tibia showed that the GSLQPIIK fragments localized at the periosteal surface and within the osteocytes. Using the same antibody, we developed an ELISA for the measurement of GSLQPIIK in the serum. This ELISA demonstrated intra- and interassay variability below 14% with a sensitivity allowing accurate determinations in the serum of healthy individuals. Serum GSLQPIIK was measured in 160 healthy postmenopausal women (mean age 65 year) participating in the Geneva Retiree Cohort. Serum GSLQPIIK levels did not correlate with total periostin, hip BMD, and the bone markers PINP and CTX. However, GSLQPIIK was negatively correlated (p values ranging from 0.007 to 0.03) with Hr-pQCT measures of tibia and radius cortical bone, but not with trabecular parameters. We have developed the first assay for the detection of periostin fragments generated by cathepsin K. Because serum levels of this new marker significantly correlated with cortical bone measurements in postmenopausal women, it may prove to be useful for the clinical investigation of patients with osteoporosis.

Role and underlying mechanisms of the interstitial protein periostin in the diagnosis and treatment of malignant tumors

Invasion and metastasis are the major characteristics of malignant tumors and are complex processes involving multiple genes. Gene regulation is a precise, large and complex biological control system, and its underlying mechanisms remain to be elucidated. Mesenchymal-specific genes are expressed primarily by mesenchymal cells, and the expression products of these genes are molecules with various structures and functions, including secreted proteins and extracellular matrix proteins. The periostin gene has been newly identified as a mesenchymal-specific gene and an extracellular-matrix secreted protein. Periostin is able to bind to various subtypes of integrin receptors on the surface of the cell membrane. This triggers relevant signal transduction pathways to alter the microenvironment of cancer cells in order to facilitate their survival, invasion, metastasis and angiogenesis as well as enhance the tolerance to hypoxia and chemicals. Therefore, periostin is associated with the grade of malignancy, level of invasion and prognosis of malignant tumors. The in-depth study of periostin may provide an effective marker for tumor diagnosis and prognosis, as well as a novel treatment target.

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.

Hyperbaric Oxygen Therapy is Ineffective as an Adjuvant to Daptomycin with Rifampicin Treatment in a Murine Model of Staphylococcus aureus in Implant-Associated Osteomyelitis

Implant-associated infections caused by bacterial biofilms are difficult to treat. Surgical intervention is often necessary to cure the patient, as the antibiotic recalcitrance of biofilms renders them untreatable with conventional antibiotics. Intermittent hyperbaric oxygen treatment (HBOT) has been proposed as an adjuvant to conventional antibiotic treatment and it has been speculated that combining HBOT with antibiotics could improve treatment outcomes for biofilm infections. In this study we addressed whether HBOT could improve treatment outcomes of daptomycin and rifampicin combination therapy. The effect of HBOT on the treatment outcomes of daptomycin and rifampicin against implant-associated osteomyelitis was quantified in a murine model. In total, 80 mice were randomized into two groups receiving antibiotics, either alone or in combination with daily intermittent HBOT (304 kPa for 60 min) following injection of antibiotics. Treatment was initiated 11 days after animals were infected with Staphylococcus aureus and treatment duration was 14 days. We found that HBOT did not improve the cure rate and did not reduce the bacterial load on the implant surface or in the surrounding tissue. Cure rates of daptomycin + rifampicin were 40% in infected tibias and 75% for implants while cure rates for HBOT-daptomycin + rifampicin were 50% and 85%, respectively, which were not significantly higher (Fisher’s exact test). While it is encouraging that the combination of daptomycin and rifampicin is very effective, our study demonstrates that this efficacy cannot be improved by adjuvant HBOT.

Intravenous bisphosphonate therapy does not thicken cementum or change periodontal ligaments of cancer patients

OBJECTIVE

To test the hypothesis that intravenous (IV) bisphosphonate (BP) therapy thickens or alters the micromorphology of cementum and periodontal ligament (PDL) in cancer patients.

STUDY DESIGN

Thirty-two teeth extracted from 24 cancer patients and separated into test (patients who have undergone IV BP therapy, n = 16) and control (patients naive to BP therapy, n = 16) groups were studied. Cementum thickness was measured in 3 different areas of the dental root with polarized light microscopy. PDL was assessed by optical light microscopy and the immunohistochemical expression of periostin.

RESULTS

No significant difference was detected in cementum thickness (apical, P = .06; medium, P = .16; cervical, P = .18) between groups. The numbers of fibroblasts in PDL (P = .56), incremental lines of cementum (P = .51) and the immunohistochemical patterns of periostin expression in PDL (P = .68) did not differ between groups.

CONCLUSION

IV BP therapy does not thicken cementum or change the micromorphology of PDL.

Preliminary insight into the periostin leverage during periodontal tissue healing

BACKGROUND

Tissue repair and regeneration is assisted by the efficient coordination of cell and extracellular matrix interactions mediated by matricellular molecules such as periostin. Given its high expression around the teeth, the periodontal organ represents an ideal system to capture the protein dynamics during wound healing.

METHODS

An observational prospective case-control study was designed to characterize periostin changes over time after periodontal surgery in tissue, oral fluids and serum by histological, protein and mRNA analyses.

RESULTS

Histological analysis showed lower periostin with a diffuse local distribution pattern in disease patients. Levels of periostin in gingival crevicular fluid (GCF) increased over time for both groups, more noticeably in the periodontitis subjects. A transient and subtle change in circulating periostin levels was also noticed. The mRNA periostin levels contrasted with the protein levels and may indicate the underlying post-transcriptional regulatory process during chronic inflammation. Levels of known periodontal disease biomarkers such as IL-β, IL1-α, TNF-α, MIP-1α and CRP served as tissue stability markers and complemented the clinical parameters recorded.

CONCLUSION

The transient local increase in GCF periostin after eliminating the local etiology in periodontally affected sites suggests its importance in the maturation and stability of the connective tissue. The decreasing levels observed as the tissue healed highlight its spatial/temporal significance.

High-throughput screening of mouse gene knockouts identifies established and novel skeletal phenotypes

Screening gene function in vivo is a powerful approach to discover novel drug targets. We present high-throughput screening (HTS) data for 3 762 distinct global gene knockout (KO) mouse lines with viable adult homozygous mice generated using either gene-trap or homologous recombination technologies. Bone mass was determined from DEXA scans of male and female mice at 14 weeks of age and by microCT analyses of bones from male mice at 16 weeks of age. Wild-type (WT) cagemates/littermates were examined for each gene KO. Lethality was observed in an additional 850 KO lines. Since primary HTS are susceptible to false positive findings, additional cohorts of mice from KO lines with intriguing HTS bone data were examined. Aging, ovariectomy, histomorphometry and bone strength studies were performed and possible non-skeletal phenotypes were explored. Together, these screens identified multiple genes affecting bone mass: 23 previously reported genes (Calcr, Cebpb, Crtap, Dcstamp, Dkk1, Duoxa2, Enpp1, Fgf23, Kiss1/Kiss1r, Kl (Klotho), Lrp5, Mstn, Neo1, Npr2, Ostm1, Postn, Sfrp4, Slc30a5, Slc39a13, Sost, Sumf1, Src, Wnt10b), five novel genes extensively characterized (Cldn18, Fam20c, Lrrk1, Sgpl1, Wnt16), five novel genes with preliminary characterization (Agpat2, Rassf5, Slc10a7, Slc26a7, Slc30a10) and three novel undisclosed genes coding for potential osteoporosis drug targets.

Zoledronate effects on systemic and jaw osteopenias in ovariectomized periostin-deficient mice

Osteoporosis and periodontal disease (PD) are frequently associated in the elderly, both concurring to the loss of jaw alveolar bone and finally of teeth. Bisphosphonates improve alveolar bone loss but have also been associated with osteonecrosis of the jaw (ONJ), particularly using oncological doses of zoledronate. The effects and therapeutic margin of zoledronate on jaw bone therefore remain uncertain. We reappraised the efficacy and safety of Zoledronate (Zol) in ovariectomized (OVX) periostin (Postn)-deficient mice, a unique genetic model of systemic and jaw osteopenia. Compared to vehicle, Zol 1M (100 µg/kg/month) and Zol 1W (100 µg/kg/week) for 3 months both significantly improved femur BMD, trabecular bone volume on tissue volume (BV/TV) and cortical bone volume in both OVX Postn^+/+ and Postn^−/− (all p<0.01). Zol 1M and Zol 1W also improved jaw alveolar and basal BV/TV, although the highest dose (Zol 1W) was less efficient, particularly in Postn^−/−. Zol decreased osteoclast number and bone formation indices, i.e. MAR, MPm/BPm and BFR, independently in Postn^−/− and Postn^+/+, both in the long bones and in deep jaw alveolar bone, without differences between Zol doses. Zol 1M and Zol 1W did not reactivate inflammation nor increase fibrous tissue in the bone marrow of the jaw, whereas the distance between the root and the enamel of the incisor (DRI) remained high in Postn^−/− vs Postn^+/+ confirming latent inflammation and lack of crestal alveolar bone. Zol 1W and Zol 1M decreased osteocyte numbers in Postn^−/− and Postn^+/+ mandible, and Zol 1W increased the number of empty lacunae in Postn^−/−, however no areas of necrotic bone were observed. These results demonstrate that zoledronate improves jaw osteopenia and suggest that in Postn^−/− mice, zoledronate is not sufficient to induce bone necrosis.

Technetium-99 conjugated with methylene diphosphonate ameliorates ovariectomy-induced osteoporotic phenotype without causing osteonecrosis in the jaw

Technetium-99 conjugated with methylene diphosphonate ((99)Tc-MDP) is a novel bisphosphonate derivative without radioactivity and has been successfully used to treat arthritis in China for years. Since bisphosphonate therapy has the potential to induce bisphosphonate-related osteonecrosis of the jaw (BRONJ), we examined whether (99)Tc-MDP represents a new class of bisphosphonate for antiresorptive therapy to ameliorate estrogen deficiency-induced bone resorption with less risk of causing BRONJ. We showed that (99)Tc-MDP-treated, ovariectomized (OVX) mice had significantly improved bone mineral density and trabecular bone volume in comparison to the untreated OVX group by inhibiting osteoclasts and enhancing osteogenic differentiation of bone marrow mesenchymal stem cells. To determine the potential of inducing BRONJ, (99)Tc-MDP/dexamethasone (Dex) or zoledronate/Dex was administered into C57BL/6J mice via the tail vein, followed by extraction of maxillary first molars. Interestingly, (99)Tc-MDP treatment showed less risk to induce osteonecrosis in the maxillary bones compared to zoledronate treatment group, partially because (99)Tc-MDP neither suppressed adaptive regulatory T cells nor activated the inflammatory T-helper-producing interleukin-17 cells. Taken together, our findings demonstrate that (99)Tc-MDP therapy may be a promising approach in the treatment of osteoporosis with less risk of causing BRONJ.

The multiple facets of periostin in bone metabolism

Periostin is a matricellular glutamate-containing protein expressed during ontogenesis and in adult connective tissues submitted to mechanical strains including bone and, more specifically, the periosteum, periodontal ligaments, tendons, heart valves, or skin. It is also expressed in neoplastic tissues, cardiovascular and fibrotic diseases, and during wound repair. Its biological functions are extensively investigated in fields such as cardiovascular physiology or oncology. Despite its initial identification in bone, investigations of periostin functions in bone-related physiopathology are less abundant. Recently, several studies have analyzed the potential role of periostin in bone biology and suggest that periostin may be an important regulator of bone formation. The aim of this article is to provide an extensive review on the implications of periostin in bone biology and its potential use in benign and metabolic bone diseases.