Human osteoclasts, not osteoblasts, deposit osteopontin onto resorption surfaces: an in vitro and ex vivo study of remodeling bone

Exploring the impact of naltrexone on the THBS1/eNOS/NO pathway in osteoporotic bile duct-ligated rats

Hepatic osteodystrophy, a prevalent manifestation of metabolic bone disease, can arise in the context of chronic liver disease. The THBS1-eNOS-NO signaling pathway plays a pivotal role in the maturation of osteoclast precursors. This study aimed to investigate the impact of Naltrexone (NTX) on bone loss by examining the THBS1-eNOS-NO signaling pathways in bile duct ligated (BDL) rats. Male Wistar rats were randomly divided into five groups (n = 10 per group): control, sham-operated + normal saline, BDL + normal saline, sham-operated + NTX (10 mg/kg), and BDL + NTX. Parameters related to liver injury were measured at the study's conclusion, and Masson-trichrome staining was employed to evaluate collagen deposition in liver tissue. Bone THBS-1 and endothelial nitric oxide synthase (eNOS) expression levels were measured using real-time PCR, while the level of bone nitric oxide (NO) was assessed through a colorimetric assay. NTX treatment significantly attenuated the BDL-induced increase in circulating levels of liver enzymes and bilirubin. THBS-1 expression levels, elevated after BDL, were significantly suppressed following NTX administration in the BDL + NTX group. Despite no alterations in eNOS expression between groups, the bone NO level, significantly decreased in the BDL group, was significantly reduced by NTX in the BDL + NTX group. This study partly provides insights into the possible molecular mechanisms in BDL-induced osteoporosis and highlights the modulating effect of NTX on these pathways. Further research is needed to establish the impact of NTX on histomorphometric indexes.

Berberine-Encapsulated Poly(lactic-co-glycolic acid)-Hydroxyapatite (PLGA/HA) Microspheres Synergistically Promote Bone Regeneration with DOPA-IGF-1 via the IGF-1R/PI3K/AKT/mTOR Pathway

Polymer microspheres have recently shown outstanding potential for bone tissue engineering due to their large specific surface area, good porosity, injectable property, good biocompatibility, and biodegradability. Their good load-release function and surface modifiability make them useful as a carrier of drugs or growth factors for the repair of bone defects in irregularly injured or complex microenvironments, such as skull defects. In this study, berberine (BBR)-encapsulated poly(lactic-co-glycolic acid) (PLGA)/hydroxyapatite (HA) microspheres were fabricated using electrified liquid jets and a phase-separation technique, followed by modification with the 3,4-hydroxyphenalyalanine-containing recombinant insulin-like growth-factor-1 (DOPA-IGF-1). Both the BBR and the IGF-1 exhibited sustained release from the IGF-1@PLGA/HA-BBR microspheres, and the composite microspheres exhibited good biocompatibility. The results of the alkaline phosphatase (ALP) activity assays showed that the BBR and IGF-1 in the composite microspheres synergistically promoted the osteogenic differentiation of MC3T3-E1 cells. Furthermore, it was confirmed that immobilized IGF-1 enhances the mRNA expression of an osteogenic-related extracellular matrix and that BBR accelerates the mRNA expression of IGF-1-mediated osteogenic differentiation and cell mineralization. Further cellular studies demonstrate that IGF-1 could further synergistically activate the IGF-1R/PI3K/AKT/mTOR pathway using BBR, thereby enhancing IGF-1-mediated osteogenesis. Rat calvarial defect repair experiments show that IGF-1@PLGA/HA-BBR microspheres can effectively promote the complete bony connection required to cover the defect site and enhance bone defect repair. These findings suggest that IGF-1@PLGA/HA-BBR composite microspheres show a great potential for bone regeneration.

2D size of trabecular bone structure units (BSU) correlate more strongly with 3D architectural parameters than age in human vertebrae

Bone tissue is continuously remodeled. In trabecular bone, each remodeling transaction forms a microscopic bone structural unit (BSU), also known as a hemiosteon or a trabecular packet, which is bonded to existing tissue by osteopontin-rich cement lines. The size and shape of the BSUs are determined by the size and shape of the resorption cavity, and whether the cavity is potentially over- or under-filled by the subsequent bone formation. The present study focuses on the recently formed trabecular BSUs, and how their 2D size and shape changes with age and trabecular microstructure. The study was performed using osteopontin-immunostained frontal sections of L2 vertebrae from 8 young (aged 18.5-37.6 years) and 8 old (aged 69.1-96.4 years) control females, which underwent microcomputed tomography (μCT) imaging prior to sectioning. The contour of 4230 BSU profiles (181-385 per vertebra) within 1024 trabecular profiles were outlined, and their 2D width, length, area, and shape were assessed. Of these BSUs, 22 (0.5%) were generated by modeling-based bone formation (i.e. without prior resorption), while 99.5% were generated by remodeling-based bone formation (i.e. with prior resorption). The distributions of BSU profile width, length, and area were significantly smaller in the old versus young females (p < 0.005), and the median profile width, length, and area were negative correlated with age (p < 0.018). Importantly, these BSU profile size parameters were more strongly correlated with trabecular bone volume (BV/TV, p < 0.002) and structure model index (SMI, p < 0.008) assessed by μCT, than age. Moreover, the 2D BSU size parameters were positively correlated to the area of the individual trabecular profiles (p < 0.0001), which were significantly smaller in the old versus young females (p < 0.024). The BSU shape parameters (aspect ratio, circularity, and solidity) were not correlated with age, BV/TV, or SMI. Collectively, the study supports the notion that not only the BSU profile width, but also its length and area, are more influenced by the age-related bone loss and shift from plates to rods (SMI), than age itself. This implies that BSU profile size is mainly driven by changes in the trabecular microstructure, which affect the size of the resorption cavity that the BSU refills.

Osteopontin on the Dental Implant Surface Promotes Direct Osteogenesis in Osseointegration

After dental implantation, osteopontin (OPN) is deposited on the hydroxyapatite (HA) blasted implant surface followed by direct osteogenesis, which is significantly disturbed in Opn-knockout (KO) mice. However, whether applying OPN on the implant surface promotes direct osteogenesis remains unclarified. This study analyzed the effects of various OPN modified protein/peptides coatings on the healing patterns of the bone-implant interface after immediately placed implantation in the maxilla of four-week-old Opn-KO and wild-type (WT) mice (n = 96). The decalcified samples were processed for immunohistochemistry for OPN and Ki67 and tartrate-resistant acid phosphatase histochemistry. In the WT mice, the proliferative activity in the HA binding peptide-OPN mimic peptide fusion coated group was significantly higher than that in the control group from day 3 to week 1, and the rates of OPN deposition and direct osteogenesis around the implant surface significantly increased in the recombinant-mouse-OPN (rOPN) group compared to the Gly-Arg-Gly-Asp-Ser peptide group in week 2. The rOPN group achieved the same rates of direct osteogenesis and osseointegration as those in the control group in a half period (week 2). None of the implant surfaces could rescue the direct osteogenesis in the healing process in the Opn-KO mice. These results suggest that the rOPN coated implant enhances direct osteogenesis during osseointegration following implantation.

Increased expression of osteopontin in subchondral bone promotes bone turnover and remodeling, and accelerates the progression of OA in a mouse model

Osteopontin (OPN) has been proved to be closely related to the pathogenesis of osteoarthritis (OA), but the role of OPN in the pathogenesis of OA has not been fully clarified. Current studies on OPN in OA mostly focus on articular cartilage, synovial membrane and articular fluid, while ignoring its role in OA subchondral bone turnover and remodeling. In this study, we used a destabilization OA mouse model to investigate the role of OPN in OA subchondral bone changes. Our results indicate that increased expression of OPN accelerates the turnover and remodeling of OA subchondral bone, promotes the formation of h-type vessels in subchondral bone, and mediates articular cartilage degeneration induced by subchondral bone metabolism. In addition, our results confirmed that inhibition of PI3K/AKT signaling pathway inhibits OPN-mediated OA subchondral bone remodeling and cartilage degeneration. This study revealed the role and mechanism of OPN in OA subchondral bone, which is of great significance for exploring specific biological indicators for early diagnosis of OA and monitoring disease progression, as well as for developing drugs to regulate the metabolism and turnover of subchondral bone and alleviate the subchondral bone sclerosis of OA.

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The soft tissues of the oral cavity are constantly subjected to microtrauma due to various factors. The gingiva in particular reacts to these beyond a point resulting in reactive hyperplastic lesions. Amongst these, the pyogenic granuloma and the peripheral ossifying fibroma are the most common clinical entities. Since they have a similar clinical presentation but diverse histomorphologic illustrations, it was advocated that there exists an interrelation between these two reactive fibrous overgrowths. Hence, this paper is intended to abolish the quandary in diagnosing peripheral ossifying fibroma and pyogenic granuloma.

Heterogeneity of the osteocyte lacuno-canalicular network architecture and material characteristics across different tissue types in healing bone

Various tissue types, including fibrous connective tissue, bone marrow, cartilage, woven and lamellar bone, coexist in healing bone. Similar to most bone tissue type, healing bone contains a lacuno-canalicular network (LCN) housing osteocytes. These cells are known to orchestrate bone remodeling in healthy bone by sensing mechanical strains and translating them into biochemical signals. The structure of the LCN is hypothesized to influence mineralization processes. Hence, the aim of the present study was to visualize and match spatial variations in the LCN topology with mineral characteristics, within and at the interfaces of the different tissue types that comprise healing bone. We applied a correlative multi-method approach to visualize the LCN architecture and quantify mineral particle size and orientation within healing femoral bone in a mouse osteotomy model (26 weeks old C57BL/6 mice). This approach revealed structural differences across several length scales during endochondral ossification within the following regions: calcified cartilage, bony callus, cortical bone and a transition zone between the cortical and callus region analyzed 21 days after the osteotomy. In this transition zone, we observed a continuous convergence of mineral characteristics and osteocyte lacunae shape as well as discontinuities in the lacunae volume and LCN connectivity. The bony callus exhibits a 34% higher lacunae number density and 40% larger lacunar volume compared to cortical bone. The presented correlations between LCN architecture and mineral characteristics improves our understanding of how bone develops during healing and may indicate a contribution of osteocytes to bone (re)modeling.

Relationship Between Clinicopathological Features and Prognosis in Appendicular Osteosarcoma in Dogs

Osteosarcoma is the most common primary bone neoplasm in dogs and often involves the appendicular skeleton. We report the clinicopathological and prognostic features of appendicular osteosarcomas diagnosed in 153 dogs from 2008 to 2018. The survival data for 22 dogs that underwent surgery and chemotherapy were statistically compared with the clinical, histopathological and immunohistochemical data for correlation with prognosis. The affected dogs had a mean age of 9.1 years and a mean body weight of 33.4 kg. No sex predilection was detected, although the incidence was slightly higher in females (52%). Large mixed and purebred dogs were most commonly affected. Long bones were affected in 124 cases (92.5%; 124/134). The extremities affected within long bones were the metaphysis of the proximal humerus (29%), distal radius (17.7%), distal femur (15.3%) and proximal tibia (7.2%). Histologically, osteoblastic osteosarcoma was most commonly detected (56.9%), followed by chondroblastic (13.7%), telangiectatic (11.8%), fibroblastic (7.8%), giant cell-rich (5.2%) and poorly differentiated neoplasms (4.6%). Regional lymph nodes were available for analysis in 28 out of 70 excisional biopsies from amputated entire limbs. Metastases to regional lymph nodes were observed in 14.3% (4/28) of these cases. Distant metastases were found in 75% (39/52) of cases in which diagnostic imaging or necropsy was carried out. The lungs were the most common site of metastasis (87.2%; 34/39 cases). Weight, age, sex, affected limb or bone, histological classification, mitotic count or histological grade did not influence survival (P >0.05). Neoplasms located at proximal extremities (n = 7) of affected limbs had a tendency for a poorer prognosis than those at distal extremities (n = 15) (P = 0.06). For these cases, the 1-year survival rate was 14.3% compared with 40% for neoplasms at distal extremities. There was no significant difference in the survival rate when amputation (n = 16) or limb preservation (n = 6) techniques were employed with chemotherapy (P = 0.20). The survival period of dogs that had undergone limb amputation, or limb preservation surgery, and chemotherapy was 73-1,185 days, with a mean and median of 376 and 256 days, respectively. Mild to marked cytoplasmic immunolabelling of osteopontin was found in all cases but the intensity (P = 0.66) and percentage of neoplastic cells labelled (P = 0.49) did not influence survival.

Short-term use of resveratrol in alloplastic graft material applied with calvarial bone defects in rats

PURPOSE

The effects of resveratrol administration on calvarial bone defects with alloplastic graft material was investigated for osteoinductive reaction and bone development in rats.

METHODS

Healthy male rats were randomly divided into 3 groups consisting of 10 rats. Groups were as follows: control (defect) group, defect + graft group, and defect + graft + resveratrol group. A calvarial bone defect was created in all groups, alloplastic bone grafts were applied to the defect in the 2nd and 3rd group, resveratrol (5 mg/kg/day) was added to the drinking water of the animals following graft application for 28 days in the 3rd group.

RESULTS

Increase in osteoclasts and necrotic changes were observed histopathologically in the control group. In the 2nd group, reduction of inflammation, congestion of blood vessels, increased osteblastic activity, osteoinductive effect, progression of osteocyte development and increased collagen fibers in connective tissue were observed. In the 3rd group, osteoblasts seemed to secrete bone matrix and accelerate osteoinductive effect with increased osteopregenitor activity and positive osteopontin and osteonectin expressions.

CONCLUSION

Resveratrol treatment was thought to be an alternative and supportive drug for implant application by inducing new bone formation in the calvaral defect region as a result of short-term treatment.

Osteopontin is An Important Regulative Component of the Fetal Bone Marrow Hematopoietic Stem Cell Niche

Osteopontin (OPN) is an important component in both bone and blood regulation, functioning as a bridge between the two. Previously, thrombin-cleaved osteopontin (trOPN), the dominant form of OPN in adult bone marrow (BM), was demonstrated to be a critical negative regulator of adult hematopoietic stem cells (HSC) via interactions with α₄β₁ and α₉β₁ integrins. We now demonstrate OPN is also required for fetal hematopoiesis in maintaining the HSC and progenitor pool in fetal BM. Specifically, we showed that trOPN is highly expressed in fetal BM and its receptors, α₄β₁ and α₉β₁ integrins, are both highly expressed and endogenously activated on fetal BM HSC and progenitors. Notably, the endogenous activation of integrins expressed by HSC was attributed to high concentrations of three divalent metal cations, Ca²⁺, Mg²⁺ and Mn²⁺, which were highly prevalent in developing fetal BM. In contrast, minimal levels of OPN were detected in fetal liver, and α₄β₁ and α₉β₁ integrins expressed by fetal liver HSC were not in the activated state, thereby permitting the massive expansion of HSC and progenitors required during early fetal hematopoiesis. Consistent with these results, no differences in the number or composition of hematopoietic cells in the liver of fetal OPN^-/- mice were detected, but significant increases in the hematopoietic progenitor pool in fetal BM as well as an increase in the BM HSC pool following birth and into adulthood were observed. Together, the data demonstrates OPN is a necessary negative regulator of fetal and neonatal BM progenitors and HSC, and it exhibits preserved regulatory roles during early development, adulthood and ageing.

Osteoclasts secrete osteopontin into resorption lacunae during bone resorption

Osteopontin (OPN) is a non-collagenous extracellular sialylated glycoprotein located in bone. It is believed to be one of the key components in osteoclast attachment to bone during resorption. In this study, we characterized OPN and other glycoproteins found in the resorption lacunae to confirm the role of osteoclasts in OPN secretion using electron microscopy and mass spectrometry. Additionally, we examined the glycan epitopes of resorption pits and the effects of different glycan epitopes on the differentiation and function of osteoclasts. Osteoarthritic femoral heads were examined by immunohistochemistry to reveal the presence of OPN in areas of increased bone metabolism in vivo. Our results demonstrate that human osteoclasts secrete OPN into resorption lacunae on native human bone and on carbonated hydroxyapatite devoid of natural OPN. OPN is associated with an elevated bone turnover in osteoarthritic bone under experimental conditions. Our data further confirm that osteoclasts secrete OPN into the resorption pit where it may function as a chemokine for subsequent bone formation. We show that α2,3- and α2,6-linked sialic acids have a role in the process of osteoclast differentiation. OPN is one of the proteins that has both of the above sialic residues, hence we propose that de-sialylation can effect osteoclast differentiation in bone.

NR4A1 Regulates Motility of Osteoclast Precursors and Serves as Target for the Modulation of Systemic Bone Turnover

NR4A1 (Nur77 or NGFI-B), an orphan member of the nuclear receptor superfamily, has been identified as a key regulator of the differentiation and function of myeloid, lymphoid, and mesenchymal cells. The detailed role of NR4A1 in bone biology is incompletely understood. Here, we report a role for NR4A1 as novel factor controlling the migration and recruitment of osteoclast precursors during bone remodeling. Myeloid-specific but not osteoblast-specific deletion of NR4A1 resulted in osteopenia due to an increase in the number of bone-lining osteoclasts. Although NR4A1-deficient osteoclast precursors displayed a regular differentiation into mature osteoclasts, they showed a hyper-motile phenotype that was largely dependent on increased osteopontin expression, suggesting that expression of NR4A1 negatively controlled osteopontin-mediated recruitment of osteoclast precursors to the trabecular bone. Pharmacological activation of NR4A1, in turn, inhibited osteopontin expression and osteopontin-dependent migration of osteoclast precursors resulted in reduced abundance of bone-resorbing osteoclasts in vivo as well as in an ameliorated bone loss after ovariectomy in mice. This study identifies NR4A1 as a crucial player in the regulation of osteoclast biology and bone remodeling and highlights this nuclear receptor as a promising target for therapeutic intervention during the treatment of osteoporosis. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Multiplex analysis of serum hormone and cytokine in patients with cervical cOPLL: towards understanding the potential pathogenic mechanisms

Cervical ossification of the posterior longitudinal ligament (cOPLL) is one of the major causes of myelopathy. However, the mechanism underlying remains elusive. In the present study, using MILLIPLEX magnetic bead panel, we investigated four serum hormones and six serum cytokines in cOPLL patients and healthy subjects. The results showed that tumor necrosis factore-α (TNF-α) were significantly increased, and DDK-1 was significantly decreased in the serum from male and female cOPLL patients compared with those from healthy controls, respectively. Osteopontin (OPN) and fibroblast growth factor-23 (FGF-23) were significantly increased in male cOPLL patients compared with that in healthy male controls. Further analysis showed that FGF-23 and OPN significantly increased, dickkopf-1 (DKK-1) decreased in the extensive cOPLL group. In addition, a significant positive correlation between the OPN and FGF-23 was observed in male cOPLL patients. The results are useful for understanding the mechanism underlying cOPLL.

Bone demineralization with citric acid enhances adhesion and spreading of preosteoblasts

BACKGROUND

Previous studies have demonstrated that bone demineralization can improve consolidation in bone grafts. The biologic mechanisms underlying this phenomenon remain unclear.

METHODS

Twelve adult male guinea pigs were used in this experiment. Forty-five bone samples removed from the calvaria of nine animals were divided in groups (n = 9) according to the time of demineralization with citric acid (50%, pH 1): 15, 30, 90, and 180 seconds and non-demineralized samples (control). Preosteoblasts (MC3T3-E1) were cultured on the bone samples for 24, 48, and 72 hours (n = 3). Fifteen samples removed from the remaining three animals were analyzed by scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) after demineralization (n = 3).

RESULTS

The number of preosteoblasts increased significantly with time in all groups. The bone surface area covered by these cells increased with time, except in the control group. Intragroup differences occurred between 24 and 72 hours (P < 0.05). Samples demineralized for 30 seconds showed greater area covered by preosteoblast cells than for the other times of demineralization in all periods of cell culture (P < 0.05) without a statistically significant difference compared with 15 seconds. SEM/EDS showed diminished content of calcium (Ca) after 15 seconds of demineralization, but the Ca content increased after 180 seconds of demineralization (P < 0.05). The phosphorus (P) amount increased significantly only after 30 seconds of demineralization (P < 0.5). The sulfur (S) content was increased in demineralized samples in relation to non-demineralized ones, reaching the highest level after 90 seconds, when the difference became significant in relation to all the other times of demineralization (P < 0.05). Magnesium (Mg) content did not differ significantly between demineralized and non-demineralized samples.

CONCLUSIONS

Bone surfaces demineralized for 30 seconds increased the spreading of preosteoblasts as well as the surface area covered by these cells. Bone demineralization deserves to be studied in periodontal and maxillofacial regenerative procedures.

The role of the SIBLING, Bone Sialoprotein in skeletal biology - Contribution of mouse experimental genetics

Bone Sialoprotein (BSP) is a member of the "Small Integrin-Binding Ligand N-linked Glycoproteins" (SIBLING) extracellular matrix protein family of mineralized tissues. BSP has been less studied than other SIBLING proteins such as Osteopontin (OPN), which is coexpressed with it in several skeletal cell types. Here we review the contribution of genetically engineered mice (BSP gene knockout and overexpression) to the understanding of the role of BSP in the bone organ. The studies made so far highlight the role of BSP in skeletal mineralization, as well as its importance for proper osteoblast and osteoclast differentiation and activity, most prominently in primary/repair bone. The absence of BSP also affects the local environment of the bone tissue, in particular hematopoiesis and vascularization. Interestingly, lack of BSP induces an overexpression of OPN, and the cognate protein could be responsible for some aspects of the BSP gene knockout skeletal phenotype, while replacing BSP for some of its functions. Such interplay between the partly overlapping functions of SIBLING proteins, as well as the network of cross-regulations in which they are involved should now be the focus of further work.

Osteopontin expression in reactive lesions of gingiva

Reactive proliferations of the gingiva comprise lesions such as pyogenic granuloma (PG), inflammatory fibroepithelial hyperplasia (IFH), peripheral ossifying fibroma (POF), and peripheral giant cell lesion. Osteopontin (OPN) has a dual role, it promotes mineralization when it is bound to solid substrate, and on the other hand, it inhibits mineralization when it is seen in association with solution. Objectives The study aimed to evaluate the expression of osteopontin in normal gingival tissue and different types of focal reactive proliferations of gingival tissue, and its role in the development of calcification within it. Material and Methods The presence and distribution of osteopontin was assessed using immunohistochemistry in five cases of normal gingival tissue and 30 cases of focal reactive proliferations of gingiva. Results There was no expression of osteopontin in normal subjects. Few cases of pyogenic granuloma, inflammatory fibroepithelial hyperplasia, and all the cases of peripheral ossifying fibroma showed positivity for osteopontin in the inflammatory cells, stromal cells, extracellular matrix, and in the calcifications. Conclusion The expression of osteopontin in all the cases of peripheral ossifying fibroma speculates that the majority of the cases of peripheral ossifying fibroma originate from the periodontal ligament cells. The treatment modalities for peripheral ossifying fibroma should differ from other focal reactive proliferations of gingiva.

BRONJ-related jaw bone is associated with increased Dlx-5 and suppressed osteopontin-implication in the site-specific alteration of angiogenesis and bone turnover by bisphosphonates

OBJECTIVES

Site-specific suppression of bone remodelling has been implicated in bisphosphonate-(BP)-related osteonecrosis of the jaws (BRONJ). Due to the origin of jaw bone from cranial neural crest, osseous differentiation is regulated specifically by the antagonizing BMP-2-downstream-transcription factors Msx-1 and Dlx-5. Osteopontin has been implicated in bone remodelling and angiogenesis. The osteoblast and osteoclast progenitor proliferation mediating Msx-1 has been demonstrated to be suppressed in BRONJ. In vitro BPs were shown to increase Dlx-5 and to suppress osteopontin expression. This study targeted Dlx-5 and osteopontin in BRONJ-related and BP-exposed jaw bone compared with healthy jaw bone samples at protein- and messenger RNA (mRNA) level, since increased Dlx-5 and suppressed osteopontin might account for impaired bone turnover in BRONJ.

MATERIALS AND METHODS

Fifteen BRONJ-exposed, 15 BP-exposed and 20 healthy jaw bone samples were processed for real-time reverse transcription polymerase chain reaction (RT-PCR) and for immunohistochemistry. Targeting Dlx-5, osteopontin and glyceraldehyde 3-phosphate dehydrogenase mRNA was extracted, quantified by the LabChip-method, followed by quantitative RT-PCR. For immunohistochemistry, an autostaining-based alkaline phosphatase antialkaline phosphatase (APAPP) staining kit was used. Semiquantitative assessment was performed measuring the ratio of stained cells/total number of cells (labelling index, Bonferroni adjustment).

RESULTS

The labelling index was significant decreased for osteopontin (p < 0.017) and significantly increased for Dlx-5 (p < 0.021) in BRONJ samples. In BRONJ specimens, a significant fivefold decrease in gene expression for osteopontin (p < 0.015) and a significant eightfold increase in Dlx-5 expression (p < 0.012) were found.

CONCLUSIONS

BRONJ-related suppression of bone turnover is consistent with increased Dlx-5 expression and with suppression of osteopontin. The BP-related impaired BMP-2-Msx-1-Dlx-5 axis might explain the jaw bone specific alteration by BP.

CLINICAL RELEVANCE

The findings of this study help to explain the restriction of RONJ to craniofacial bones. BRONJ might serve as a model of disease elucidating the specific signal transduction of neural crest cell-derived bone structures in health and disease.

Does collagen trigger the recruitment of osteoblasts into vacated bone resorption lacunae during bone remodeling?

Osteoblast recruitment during bone remodeling is obligatory to re-construct the bone resorbed by the osteoclast. This recruitment is believed to be triggered by osteoclast products and is therefore likely to start early during the remodeling cycle. Several osteoclast products with osteoblast recruitment potential are already known. Here we draw the attention on the osteoblast recruitment potential of the collagen that is freshly demineralized by the osteoclast. Our evidence is based on observations on adult human cancellous bone, combined with in vitro assays. First, freshly eroded surfaces where osteoblasts have to be recruited show the presence of non-degraded demineralized collagen and close cell-collagen interactions, as revealed by electron microscopy, while surface-bound collagen strongly attracts osteoblast lineage cells in a transmembrane migration assay. Compared with other extracellular matrix molecules, collagen's potency was superior and only equaled by fibronectin. Next, the majority of the newly recruited osteoblast lineage cells positioned immediately next to the osteoclasts exhibit uPARAP/Endo180, an endocytic collagen receptor reported to be involved in collagen internalization and cell migration in various cell types, and whose inactivation is reported to lead to lack of bone formation and skeletal deformities. In the present study, an antibody directed against this receptor inhibits collagen internalization in osteoblast lineage cells and decreases to some extent their migration to surface-bound collagen in the transmembrane migration assay. These complementary observations lead to a model where collagen demineralized by osteoclasts attracts surrounding osteoprogenitors onto eroded surfaces, and where the endocytic collagen receptor uPARAP/Endo180 contributes to this migration, probably together with other collagen receptors. This model fits recent knowledge on the position of osteoprogenitor cells immediately next to remodeling sites in adult human cancellous bone.

Increased osteopontin contributes to inhibition of bone mineralization in FGF23-deficient mice

Excessive FGF23 has been identified as a pivotal phosphaturic factor leading to renal phosphate-wasting and the subsequent development of rickets and osteomalacia. In contrast, loss of FGF23 in mice (Fgf23(-/-) ) leads to high serum phosphate, calcium, and 1,25-vitamin D levels, resulting in early lethality attributable to severe ectopic soft-tissue calcifications and organ failure. Paradoxically, Fgf23(-/-) mice exhibit a severe defect in skeletal mineralization despite high levels of systemic mineral ions and abundant ectopic mineralization, an abnormality that remains largely unexplained. Through use of in situ hybridization, immunohistochemistry, and immunogold labeling coupled with electron microscopy of bone samples, we discovered that expression and accumulation of osteopontin (Opn/OPN) was markedly increased in Fgf23(-/-) mice. These results were confirmed by qPCR analyses of Fgf23(-/-) bones and ELISA measurements of serum OPN. To investigate whether elevated OPN levels were contributing to the bone mineralization defect in Fgf23(-/-) mice, we generated Fgf23(-/-) /Opn(-/-) double-knockout mice (DKO). Biochemical analyses showed that the hypercalcemia and hyperphosphatemia observed in Fgf23(-/-) mice remained unchanged in DKO mice; however, micro-computed tomography (µCT) and histomorphometric analyses showed a significant improvement in total mineralized bone volume. The severe osteoidosis was markedly reduced and a normal mineral apposition rate was present in DKO mice, indicating that increased OPN levels in Fgf23(-/-) mice are at least in part responsible for the osteomalacia. Moreover, the increased OPN levels were significantly decreased upon lowering serum phosphate by feeding a low-phosphate diet or after deletion of NaPi2a, indicating that phosphate levels contribute in part to the high OPN levels in Fgf23(-/-) mice. In summary, our results suggest that increased OPN is an important pathogenic factor mediating the mineralization defect and the alterations in bone metabolism observed in Fgf23(-/-) bones.

Titanium nanotubes activate genes related to bone formation in vitro

Background:

Titanium is used worldwide to make osseointegrable devices, thanks to its favorable characteristics as mechanical proprieties and biocompatibility, demonstrated by in vivo studies with animal models and clinical trials over a forty-year period. However, the exact genetic effect of the titanium layer on cells is still not well characterized.

Materials and Methods:

To investigate how titanium nanotubes stimulate osteoblasts differentiation and proliferation, some osteoblast genes (SP7, RUNX2, COL3A1, COL1A1, ALPL, SPP1 and FOSL1) were analyzed by quantitative Real Time RT- PCR.

Results:

After 15 days, osteoblasts cultivated on titanium naotube showed the up-regulation of bone related genes SP7, ENG, FOSL1 and SPP1 and the down-regulation of RUNX2, COL3A1, COL1A1, and ALPL. After 30 days of treatment, the bone related genes SP7, ENG, FOSL1 and RUNX2 were up-regulated while COL3A1, COL1A1, ALPL and SPP1 were down-regulated.

Conclusions:

Our results, demonstrates that titanium nanotubes can lead to osteoblast differentiation and extracellular matrix deposition and mineralization in dental pulp stem cells by the activation of osteoblast related genes SPP1, FOSL1 and RUNX2.

Morphological evidences of Bio-Oss® colonization by CD44-positive cells

OBJECTIVES

Our objectives were to examine vascular and cellular colonization in anorganic bovine bone (ABB) after 6 months of healing in human maxillary sinus augmentation grafts.

MATERIAL AND METHODS

Fifty unilateral maxillary sinus augmentation procedures were performed on 50 consecutive patients. Bone cores were obtained through the implant receptor sites 6 months later and evaluated with morphological image analysis and immunohistochemical techniques.

RESULTS

Image analysis revealed a mean of 35.44 ± 16% vital bone, 31.66 ± 15% non-mineralized tissue, and 32.72 ± 25% remnant ABB particles. In our patients, neovascularization in 46.3% of cases was demonstrated within ABB particles 6 months after sinus floor augmentation surgery. Neovascularization of ABB particles was inversely related to age, directly to osteoclast number per mm², and not influenced by habits or disease. CD44-positive cells colonization was found in 74% of cases. An important correlation was found regarding CD44 expression and number of vessel in ABB particles (r = 0.624 P < 0.001, Pearson). Osteopontin expression was detected on the interstitial boundary of bone with ABB particles and within the osteocyte lacunae and bone canaliculi and was relationship with presence of CD44-positive cells inside ABB particles (r = 0.388, P = 0.046, Pearson).

CONCLUSION

In conclusion, images compatible with osteone colonized by osteocytes CD44 positive and neovascularization in ABB particles were observed after 6 months of graft maturation. These biologic events have not previously been morphologically and immunohistochemically documented.

Sequential expression of osteoblast phenotypic genes during medullary bone formation and resorption in estrogen-treated male Japanese quails

Medullary bone is formed reticularly in the bone marrow cavity of the long bones of female birds. Although this bone matrix contains fewer collagen fibers and more acid mucopolysaccharides than cortical bone, it is not clear that the expression pattern of osteoblast phenotypic genes during bone remodeling. Therefore, 17β-estradiol (E2)-treated male Japanese quails were used to examine the temporal expression patterns of osteoblast phenotypic genes, and to simultaneously confirm the morphological changes occurring in the bone marrow cavity during medullary bone formation and resorption. After E2 treatment, bone lining cells proliferated and developed into mature osteoblasts that had intense alkaline phosphatase (ALP) activity. These cells began to form medullary bone that contained acid mucopolysaccharides and tartrate-resistantacid phosphatase. Runt-related gene 2 (Runx2) mRNA was stably expressed throughout the process. The expression of both ALP and type I collagen mRNAs increased initially, and then rapidly decreased after day 7, while osteoclasts began to resorb medullary bone at day 5. The expression of bone matrix-related genes peaked at day 5, and suddenly decreased at day 7, except for osteopontin. Taken together with these results, the expression patterns of bone matrix-related genes during the later stages might be related to osteoclast activity. Additionally, the constant expression of Runx2 during bone formation and resorption suggested that osteoprogenitor cells always exist in the bone marrow cavity. Therefore, the expression patterns of these genes and the characteristics of bone matrix might extremely be related to the quick remodeling of medullary bone.

Bio-Oss®acts on Stem cells derived from Peripheral Blood

OBJECTIVES

This study aims to study how Bio-Oss® can induce osteoblast differentiation in mesenchymal stem cells, the expression levels of bone related genes and mesenchymal stem cells markers using real time Reverse Transcription-Polymerase Chain Reaction.

METHODS

PB-hMSCs stem preparations were obtained for gradient centrifugation from peripheral blood of healthy anonymous volunteers, using the Acuspin System-Histopaque 1077. The samples were then cultured for 7 days for RNA processing, and the expression was quantified using real time PCR.

RESULTS

Bio-Oss® caused an induction of osteoblast transcriptional factor like RUNX2 and of bone related genes; SPP1 and FOSL1. In contrast, the expression of ENG was significantly decreased in stem cells treated with Bio-Oss® with respect to untreated cells, indicating the differentiation effect of this biomaterial on stem cells.

CONCLUSION

The results obtained can be relevant to enhance the understanding of the molecular mechanism of bone regeneration and can act as a model for comparing other materials with similar clinical effects.

The importance of the SIBLING family of proteins on skeletal mineralisation and bone remodelling

The small integrin-binding ligand N-linked glycoprotein (SIBLING) family consists of osteopontin, bone sialoprotein, dentin matrix protein 1, dentin sialophosphoprotein and matrix extracellular phosphoglycoprotein. These proteins share many structural characteristics and are primarily located in bone and dentin. Accumulating evidence has implicated the SIBLING proteins in matrix mineralisation. Therefore, in this review, we discuss the individual role that each of the SIBLING proteins has in this highly orchestrated process. In particular, we emphasise how the nature and extent of their proteolytic processing and post-translational modification affect their functional role. Finally, we describe the likely roles of the SIBLING proteins in clinical disorders of hypophosphataemia and their potential therapeutic use.

Bone structure and B-cell populations, crippled by obesity, are partially rescued by brief daily exposure to low-magnitude mechanical signals

Deterioration of the immune and skeletal systems, each of which parallel obesity, reflects a fragile interrelationship between adiposity and osteoimmunology. Using a murine model of diet-induced obesity, this study investigated the ability of mechanical signals to protect the skeletal-immune systems at the tissue, cellular, and molecular level. A long-term (7 mo) high-fat diet increased total adiposity (+62%), accelerated age-related loss of trabecular bone (-61%), and markedly reduced B-cell number in the marrow (-52%) and blood (-36%) compared to mice fed a regular diet. In the final 4 mo of the protocol, the application of low-magnitude mechanical signals (0.2 g at 90 Hz, 15 min/d, 5 d/wk) restored both bone structure and B cells to those levels measured in control mice fed a regular diet. These phenotypic outcomes were achieved, in part, by reductions in osteoclastic activity and a biasing of hematopoietic stem cell differentiation toward the lymphoid B-cell lineage and away from a myeloid fate. These results emphasize that obesity undermines both the skeletal and immune systems, yet brief exposure to mechanical signals, perhaps as a surrogate to the salutary influence of exercise, diminishes the consequences of diabetes and obesity, restoring bone structure and normalizing B-cell populations by biasing of the fate of stem cells through mechanosensitive pathways.

Effect of titanium surface topographies on human bone marrow stem cells differentiation in vitro

Coating characteristics of dental implants such as composition and topography regulate cell response during implant healing. The aim of this study was to assess how surface topography can affect osteogenic differentiation of mesenchymal stem cells (MSCs) by analyzing the expression levels of bone-related genes and MSCs marker. Thirty disk-shaped, commercially pure Grade 2 titanium samples (10 × 2 mm) with 3 different surface topographies (DENTSPLY-Friadent GmbH, Mannheim, Germany) were used in the present study: 10 Ti machined disks (control), 10 Ti sandblasted and acid-etched disks (DPS(®)) and 10 sandblasted and acid-etched disks at high temperature (Plus(®)). Samples were processed for real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. By comparing machined and Plus(®) disks, quantitative real-time RT-PCR showed a significant reduction of the bone-related genes osteocalcin (BGLAP) and osteoblast transcriptional factor (RUNX2). The comparison between DPS(®) and Plus(®) disks showed a slight induction of all the genes examined (RUNX2, ALPL, COL1A1, COL3A1, ENG, FOSL1, SPP1, and SP7); only the expression of BGLAP remained stable. The present study, demonstrated that implant surface topography affects osteoblast gene expression. Indeed, Plus(®) surface produces an effect on MSCs in the late differentiation stages.

Anatase-based implants nanocoating on stem cells derived from adipose tissue

PURPOSE

The aim of this study was to investigate the effect of a new anatase coating with antibacterial properties (Bactercline anatase coating [BAC]) on dental implants in the commitment of stem cells derived from adipose tissue to osteoblasts.

MATERIALS AND METHODS

Using real-time reverse transcription polymerase chain reaction, the quantitative expression of specific genes, such as transcriptional factors (runx2 and sp7), bone-related genes (spp1, col1a1, col3a1, alpl, and fosl1), and mesenchymal stem cells marker (eng), was examined.

RESULTS

BAC caused induction of bone-related genes such as sp7, fosl1, alpl, and spp1. In contrast, the expression of runx2, col3a1, and col1a1 was decreased in stem cells treated with BAC with respect to untreated cells.

CONCLUSION

The obtained results are relevant to better understand the molecular mechanism of bone regeneration and as a model for comparing other materials with similar clinical effects.

How are osteoclasts induced to resorb bone?

Although much is known about how osteoclasts are formed, we know little about how they are activated, or how they recognize bone as the substrate appropriate for resorption. Bone mineral is considered to be essential to this recognition process, but a "mineral receptor" has never been identified. Recently, we found that resorptive behavior, as judged by the formation of ruffled borders and actin rings, occurs on ordinary tissue culture substrates if they are first coated with vitronectin. Similarly, vitronectin-coated substrates induce osteoclasts to secrete tartrate-resistant acid phosphatase and to form podosome belts, and to make resorption trails in the protein that coat the substrate. The same applies to bone mineral, which only induces resorptive behavior if coated with vitronectin. In contrast, fibronectin has none of these effects, despite inducing adhesion and spreading. It appears that osteoclasts recognize bone as the substrate appropriate for resorption through the high affinity of vitronectin-receptor ligands for bone mineral.

Histologic evaluation of human alveolar sockets treated with an artificial bone substitute material

This study involved a histologic, enzyme histologic, immunohistologic, and three-dimensional microstructure evaluating the extent of osteogenesis and repair in the human alveolar extraction socket achievable with an artificial bone substitute. After tooth extraction in 7 patients, extraction sockets were filled with Mastergraft (15% hydroxyapatite, 85% β-tricalcium phosphate complex). Radiomicrographs and histologic examinations were performed on samples obtained during dental implant placement procedure. On micro-computed tomography, new bone was observed in all collected samples, and osteogenesis was observed to have taken place around the artificial bone substitute. Histologically, active osteogenesis was found throughout the region observed. Addition of new bone around the Mastergraft was observed, and osteoblast-like cells were present. Cells that had partially invaded the artificial bone included tartrate-resistant acid phosphate-positive and CD34-positive cells. These findings indicate that the Mastergraft artificial bone induced osteogenesis in the jawbone and seemed effective for repairing bone defects.

Osteoplant acts on stem cells derived from peripheral blood

Objectives:

The osteoplant is an equine, flexible, heterologous, deantigenic, cortical, and spongy bone tissue, totally reabsorbable, used for implantation of bone tissue, to restore skeletal, even weight-bearing structures. However, how the osteoplant alters osteoblast activity to promote bone formation is poorly understood.

Materials and Methods:

To study how the osteoplant induces osteoblast differentiation in mesenchymal stem cells, the expression levels of bone-related genes, and mesenchymal stem cell markers are analyzed, using real time Reverse Transcription-Polymerase Chain Reaction (RT-PCR).

Results:

The osteoplant causes induction of osteoblast transcriptional factors such as osterix (RUNX2), and of bone-related genes such as osteopontin (SPP1) and osteocalcin (BGLAP). In contrast the expression of ENG (CD105) is significantly decreased in stem cells treated with osteoplant, with respect to untreated cells, indicating the differentiation effect of this biomaterial on stem cells.

Conclusion:

The obtained results can be relevant to better understand the molecular mechanism of bone regeneration and as a model for comparing other materials with similar clinical effects.

Polylactide-Polyglycolide Resorbable Plates Stimulates Adipose Tissue-Derived Stem Cells towards Osteoblasts Differentiation

Polylactide, polyglycolide materials or devices have been utilized routinely during maxillofacial, craniofacial, and orthopaedic reconstructive surgical procedures.(1) These materials combine the benefits of rigid fixation with the advantages of biodegradation, avoiding the need for implant removal and minimizing the risk of other complications.(2) To study how polylactide, polyglycolide acids plates (PLPG plates) can induce osteoblast differentiation and proliferation in mesenchymal stem cells, the expression levels of bone related genes (RUNX2, SP7, ALPL, SPP1, COL1A1, COL3A1 and FOSL1) and mesenchymal stem cells marker (ENG) were measured in adipose derived stem cells (ADSCs) and normal osteoblast (NO) cultivated on PLPG plates after 15 and 30 days of treatment using real time Reverse Transcription-Polymerase Chain Reaction. Significantly differentially expressed genes among ADSCs and NO were SP7, ENG, FOSL1, RUNX, ALPL and SPP1 in the first 15 days of treatment and SP7, ENG FOSL1, COL3A1 COL1A1, SPP1 and ALPL after 30 days. The present study demonstrated that PLPG plates strongly influences the behavior of ADSCs in vitro by enhancing proliferation, differentiation and deposition of matrix.

Bone is not essential for osteoclast activation

BACKGROUND

The mechanism whereby bone activates resorptive behavior in osteoclasts, the cells that resorb bone, is unknown. It is known that α(v)β(3) ligands are important, because blockade of α(v)β(3) receptor signaling inhibits bone resorption, but this might be through inhibition of adhesion or migration rather than resorption itself. Nor is it known whether α(v)β(3) ligands are sufficient for resorption the consensus is that bone mineral is essential for the recognition of bone as the substrate appropriate for resorption.

METHODOLOGY/PRINCIPAL FINDINGS

Vitronectin- but not fibronectin-coated coverslips induced murine osteoclasts to secrete tartrate-resistant acid phosphatase, as they do on bone. Osteoclasts incubated on vitronectin, unlike fibronectin, formed podosome belts on glass coverslips, and these were modulated by resorption-regulating cytokines. Podosome belts formed on vitronectin-coated surfaces whether the substrates were rough or smooth, rigid or flexible. We developed a novel approach whereby the substrate-apposed surface of cells can be visualized in the scanning electron microscope. With this approach, supported by transmission electron microscopy, we found that osteoclasts on vitronectin-coated surfaces show ruffled borders and clear zones characteristic of resorbing osteoclasts. Ruffles were obscured by a film if cells were incubated in the cathepsin inhibitor E64, suggesting that removal of the film represents substrate-degrading behavior. Analogously, osteoclasts formed resorption-like trails on vitronectin-coated substrates. Like bone resorption, these trails were dependent upon resorbogenic cytokines and were inhibited by E64. Bone mineral induced actin rings and surface excavation only if first coated with vitronectin. Fibronectin could not substitute in any of these activities, despite enabling adhesion and cell spreading.

CONCLUSIONS/SIGNIFICANCE

Our results show that ligands α(v)β(3) are not only necessary but sufficient for the induction of resorptive behavior in osteoclasts; and suggest that bone is recognized through its affinity for these ligands, rather than by its mechanical or topographical attributes, or through a putative 'mineral receptor'.

Engipore acts on human bone marrow stem cells

OBJECTIVES

Porous HA scaffolds are promising materials for tissue engineering because they offer a tridimensional support and serve as template for cell proliferation and at last tissue formation. Engipore provide a natural 3D scaffold with organic fibrous material in bone. However, how this material alters osteoblast activity to promote bone formation is poorly understood.

MATERIALS AND METHODS

To study how Engipore can induce osteoblast differentiation in mesenchymal stem cells, the expression levels of bone related genes and mesenchymal stem cells marker were analyzed.

RESULTS

Engipore causes a significant induction of osteoblast transcriptional factors like SP7 and RUNX2 and of the bone-related gene osteocalcin (BGLAP). The expression of CD105 was not significantly changed in stem cells treated with Engipore with respect to untreated cells, while SSP1 (osteopontin) was significantly down expressed thus reducing osteoclast activity.

CONCLUSIONS

The obtained results can be relevant to better understand the molecular mechanism of bone regeneration.

Mechanical properties and osteocompatibility of novel biodegradable alanine based polyphosphazenes: Side group effects

The versatility of polymers for tissue regeneration lies in the feasibility to modulate the physical and biological properties by varying the side groups grafted to the polymers. Biodegradable polyphosphazenes are high-molecular-weight polymers with alternating nitrogen and phosphorus atoms in the backbone. This study is the first of its kind to systematically investigate the effect of side group structure on the compressive strength of novel biodegradable polyphosphazene based polymers as potential materials for tissue regeneration. The alanine polyphosphazene based polymers, poly(bis(ethyl alanato) phosphazene) (PNEA), poly((50% ethyl alanato) (50% methyl phenoxy) phosphazene) (PNEA(50)mPh(50)), poly((50% ethyl alanato) (50% phenyl phenoxy) phosphazene) (PNEA(50)PhPh(50)) were investigated to demonstrate their mechanical properties and osteocompatibility. Results of mechanical testing studies demonstrated that the nature and the ratio of the pendent groups attached to the polymer backbone play a significant role in determining the mechanical properties of the resulting polymer. The compressive strength of PNEA(50)PhPh(50) was significantly higher than poly(lactide-co-glycolide) (85:15 PLAGA) (p<0.05). Additional studies evaluated the cellular response and gene expression of primary rat osteoblast cells on PNEA, PNEA(50)mPh(50) and PNEA(50)PhPh(50) films as candidates for bone tissue engineering applications. Results of the in vitro osteocompatibility evaluation demonstrated that cells adhere, proliferate, and maintain their phenotype when seeded directly on the surface of PNEA, PNEA(50)mPh(50), and PNEA(50)PhPh(50). Moreover, cells on the surface of the polymers expressed type I collagen, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein, which are characteristic genes for osteoblast maturation, differentiation, and mineralization.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.

Role of osteopontin in breast cancer patients

AIM AND BACKGROUND

In breast cancer, as in almost all neoplastic diseases, the prognosis is strictly related to the invasive capacity, local and distant, that characterizes the growth of all tumors. Since the mechanisms that regulate replication of the neoplastic cells, with consequent capacity to metastasize, are not completely known, identification of new markers represents the gold standard of research in the stratification of patients with such a pathology. Osteopontin, a specific phosphoglycoprotein isolated from extracellular bone matrix and actively involved in mechanisms of bone reabsorption, appears to play a key role in osteoclastogenesis at the level of the skeleton in some pathologic situations. It has been found that patients with metastatic bone lesions from breast or prostate cancer present, with respect to subjects without repetitive bone lesions, elevated serum levels of the protein, indicating that osteopontin could play an important role in the development and progression of the neoplastic disease at the bone level.

METHODS AND STUDY DESIGN

The authors studied 26 patients with breast cancer, evaluating as a marker also serum osteopontin levels.

RESULTS AND CONCLUSIONS

The results, although obtained on a small number of patients, showed that osteopontin evaluation in breast cancer patients can be a particularly interesting method of research in staging of the disease as well as in the prognosis, thereby attributing a role of a biotumoral marker also in the follow-up of the therapy.

Gene therapy via inducible nitric oxide synthase: a tool for the treatment of a diverse range of pathological conditions

Nitric oxide (NO(.)) is a reactive nitrogen radical produced by the NO synthase (NOS) enzymes; it affects a plethora of downstream physiological and pathological processes. The past two decades have seen an explosion in the understanding of the role of NO(.) biology, highlighting various protective and damaging modes of action. Much of the controversy surrounding the role of NO(.) relates to the differing concentrations generated by the three isoforms of NOS. Both calcium-dependent isoforms of the enzyme (endothelial and neuronal NOS) generate low-nanomolar/picomolar concentrations of NO(.). By contrast, the calcium-independent isoform (inducible NOS (iNOS)) generates high concentrations of NO(.), 2-3 orders of magnitude greater. This review summarizes the current literature in relation to iNOS gene therapy for the therapeutic benefit of various pathological conditions, including various states of vascular disease, wound healing, erectile dysfunction, renal dysfunction and oncology. The available data provide convincing evidence that manipulation of endogenous NO(.) using iNOS gene therapy can provide the basis for future clinical trials.

Sol–gel bioactive glasses support both osteoblast and osteoclast formation from human bone marrow cells

We have examined the ability of bioactive sol-gel glass ceramics to support both osteoblast and osteoclast differentiation from human bone marrow cells (HBMC). Nucleated cells from human bone marrow were cultured on tissue culture plastic and on two sol-gel coatings: A2 glass-ceramic containing 54 mol % CaO/40 mol % SiO(2) and S2 glass-ceramic containing 16 mol % CaO/80 mol % SiO(2). Osteoblast differentiation was followed by measuring alkaline phosphatase (ALP) activity, mRNA levels for ALP, osteopontin, RANK ligand (RANKL), and immunofluorescent co-localization of ALP and RANKL. Osteoclasts were identified by morphology and positive staining for tartrate-resistant acid phosphatase (TRAP). ALP activity and mRNA levels were similar for cells on A2 coatings and on tissue culture plastic, but mRNA levels of osteopontin and RANKL were tenfold higher on A2 than on plastic. Cultures on A2 coatings also contained multinucleated osteoclasts staining positively for TRAP. In contrast, cells cultured on S2 coatings had the characteristics of more differentiated osteoblasts as measured by higher ALP expression. However, the levels of osteopontin and RANKL mRNA on S2 glass were lower than on A2 glass and there were fewer, weakly staining TRAP-positive multinucleate cells. Thus, sol-gel glass-ceramic materials differing in CaO/SiO(2) ratios can produce markedly different effects on the osteoblast and osteoclast differentiation from HBMC.

Histochemical examinations on cortical bone regeneration induced by thermoplastic bioresorbable plates applied to bone defects of rat calvariae

We aimed to histologically elucidate whether bioresorbable plates (DeltaSystem) can induce cortical bone formation, which is essential for long-lasting bone augmentation. Standardized bone defects in rat calvariae were covered with a convexly-shaped DeltaSystem plate, and then processed for histological observations. At 1 week, alkaline phosphatase-positive osteoblasts were seen in the newly-formed bone extending from the cavity's bottom, indicating accelerated osteogenesis. A thick layer of soft connective tissue positive for periostin, a hallmark of periosteum, covered this new bone. At 2 weeks, a spongy bone had filled the cavity up to half its height. The inner layer of the soft tissue facing the spongy bone revealed abundant periostin and osteopontin, and had many tartrate-resistant acid phosphatase-positive osteoclasts. At 4 weeks, this layer had given rise to thin new bony matrices without relation to the spongy bone arising from the cavity. These bone matrices had been thickened by 8 weeks, and turned into a thick cortical bone outlining the regenerated bone at 12 weeks. Thus, our study has provided histological evidences of cortical osteogenesis when DeltaSystem plates are used for bone augmentation procedures.