Empty Osteocyte Lacunae Research Articles

RANK/RANKL/OPG signaling pathways in necrotic jaw bone from bisphosphonate-treated subjects.

Osteonecrosis of the jaw (ONJ) is a chronic complication affecting long-term bisphosphonate-treated subjects, recognized by non-healing exposed bone in the maxillofacial region. The pathophysiological mechanism underlying ONJ has not been fully elucidated. The aim of the present study was to investigate the role of RANK/RANKL/OPG signaling pathway and, in parallel, to evaluate angiogenic and matrix mineralization processes in jaw bone necrotic samples obtained from bisphosphonate-treated subjects with established ONJ. Necrotic bone samples and native bone samples were processed for Light and Field Emission in Lens Scanning Electron Microscope (FEISEM) analyses, for Real-Time RT-PCR to evaluate the gene expression of TNFRSF11A (RANK), TNFSF11 (RANKL), and TNFSF11B (OPG) and for immunohistochemical analyses of VEGF and BSP expression. Morphological analyses performed by Light microscope and FEISEM show empty osteocytic lacunae and alteration of lamellar organization with degradation of the mineralized bone matrix in necrotic bone samples. A significant increase in TNFRSF11A, TNFSF11, TRAF6 and NFAT2 gene expression, and a reduction of TNFSF11B gene transcription level compared is also showed in necrotic bone compared to control samples. No significant difference of VEGF expression is evidenced, while lower BSP expression in necrotic bone compared to healthy samples is found. Even if the pathogenesis of bisphosphonate-associated ONJ remains unknown, a link between oral pathogens and its development seems to exist. We suppose lipopolysaccharide produced by bacteria colonizing and infecting necrotic bone and the surrounding viable area could trigger RANK/RANKL/OPG signaling pathway and, in this context, osteoclasts activation could be considered as a protective strategy carried out by the host bone tissue to delimitate the necrotic area and to counteract infection.

Comparison of Surface Morphology and Healing in Rat Calvaria Bone Defects between Ultrasonic Surgical Method and Rotary Cutting Method

The aim of this study was to investigate the influence of ultrasonic surgical method (piezoelectric surgery) on invasions of bone structure in early stages and the subsequent healing process of bone defects of rat calvaria as compared with that of rotary cutting using an appropriate rotation speed. Thirteen-week-old male Sprague-Dawley rats were used in this study. Bone defects were prepared in rat calvaria using either an ultrasonic surgical instrument with an ultrasonic insert tip (Ui) or a handpiece with a round bur (Rb) as a rotary cutting instrument (control). Morphological evaluations of the cutting surfaces in the bone defects were assessed by scanning electron microscope (SEM) and confocal laser microscope (CLM) observation. The degree of invasions of the bone structure in the early stages after bone defects were made was assessed by the ratio of empty osteocyte lacunae relative to the total number of osteocytes. The process of bone healing was analyzed by histological observation, immunohistochemical staining with proliferating cell nuclear antigen (PCNA) and osteocalcin (OC), and ratio of PCNA-positive cells. Many fine, parallel streaky cutting traces were observed in the Ui groove surfaces, whereas the Rb groove surfaces were flat and no parallel cutting traces were observed. The arithmetic average roughness of the Ui group (10.06 ± 1.96 µm) was significantly higher than that of the Rb group (2.52 ± 0.16 µm) (p < 0.05). During the entire observation period, no differences in histological observation and immunohistochemical staining were observed between the Ui and Rb groups. No significant differences were recognized in the ratio of empty lacunae and PCNA-positive cells between the Ui and Rb groups. In the present study, there were no appreciable differences in the invasions of bone structure in the early stages and the subsequent healing process of the bone defects of rat calvaria between ultrasonic surgical method and rotary cutting method.

Ultrastructural and immunohistochemical study of the effect of sodium alendronate in the progression of experimental periodontitis in rats.

The aim of the present research was to investigate the ultrastructural aspects and the immunoexpression of receptor activator of NFκB ligand (RANKL) and osteoprotegerin (OPG) on experimental periodontal disease of alendronate (ALN)-treated rats. Male Wistar rats received daily injections of 2.5 mg/kg body weight of ALN during 7 days previously and 7, 14, and 21 days after the insertion of a 4.0 silk suture into the gingival sulcus around the right upper second molar. Specimens were fixed in 0.1% glutaraldehyde + 4% formaldehyde under microwave irradiation, decalcified in 4.13% EDTA and paraffin embedded for TRAP histochemistry and immunohistochemistry for RANKL and OPG, or embedded in Spurr epoxy resin for TEM analysis. ALN reduced the activity of osteoclasts and significantly decreased the resorption of the alveolar crest. In the control group the alveolar crest appeared resorbed by TRAP-positive osteoclasts, which presented ultrastructural features of activated cells. The immunoexpression of RANKL was not inhibited by the drug; however, the expression of OPG was increased in the treated animals. The alveolar crest of ALN-treated specimens at 21 days showed signs of osteonecrosis, like empty osteocyte lacunae, the exposed bone regions and bacterial infection. The results showed that ALN treatment in individuals with periodontal disease represents a risk of osteonecrosis because of the reduced activity of osteoclasts resultant of the increased immunoexpression of OPG.

Preventive effects of siRNA targeting PPARγ gene on steroid-induced osteonecrosis in rabbits

Purposes/Aim: Glucocorticoid steroids can induce expression of PPARγ gene and enhance adipogenesis by bone marrow mesenchymal stem cells (BMSCs), which may result in osteonecrosis of the femoral head. Currently, there are no medications available to prevent steroid-induced osteonecrosis. We hypothesized that siRNA targeting PPARγ gene may prevent steroid-induced adipogenesis and osteonecrosis in rabbit. The purpose of this study was to evaluate the preventive effects of siRNA targeting PPARγ gene on steroid-induced adipogenesis and osteonecrosis.Methods: Forty-eight healthy New Zealand rabbits were randomized into four groups with Group M treated with dexamethasone only, Group S with dexamethasone and a recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene, Group Con with dexamethasone and a vector carrying irrelative sequence, and Group N with no treatment serving as control. Expressions of the PPARγ, osteocalcin and Runx2 genes, as well as histopathologic changes were evaluated.Results: The levels of PPARγ gene expression were decreased while the levels of osteocalcin and Runx2 gene expression were increased in rabbits treated with dexamethasone and recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene (Group S), compared to rabbits treated either with dexamethasone alone (Group M) or with both dexamethasone and a vector carrying irrelative sequence (Group Con). The marrow necrosis, adipocyte hypertrophy and proliferation, diminished hematopoiesis, thinner and sparse trabeculae, and increased empty osteocyte lacunae in the femoral head were observed in Group M and Group Con rabbits. However, no such changes were seen in Group S rabbits that were treated with dexamethasone and a recombinant adenovirus shuttle vector carrying siRNA targeting PPARγ gene.Conclusion: siRNA targeting PPARγ gene can inhibit adipogenic differentiation of BMSCs and prevent steroid-induced osteonecrosis in rabbit. The inhibition of bone-marrow adipogenesis and concomitant enhancement of osteogenesis with RNAi may provide a novel approach to the prevention of steroid-induced osteonecrosis.

The Validity of CMFDA and Ethd-1 in the Determination of Osteocyte Viability in the Diaphysis of Long Bones in a Sheep Model

The determination of osteocyte viability is essential in bone research and clinical practice; however its determination at the time of sampling, without disruption of the bone matrix is difficult. The current clinical histological diagnosis of osteonecrosis requires the identification of empty osteocyte lacunae, which may take up to 4 weeks to completely develop. The aim of this study was to assess the efficacy of 5-chloromethylfluorescein diacetate (CMFDA) and ethidium homodimer-1 (EthD-1) to stain osteocyte viability at the time of sampling without disrupting the bony architecture in a sheep model. The methods involved harvesting adult sheep femoral and tibial mid-diaphyseal bone and staining 1 cm thick samples with different concentrations of CMFDA and EthD-1 for varying durations at different temperatures. Osteocyte viability and the effect on background staining were assessed. The results show that CMFDA and EthD-1 can successfully stain for osteocyte viability in situ at the time of sampling without destruction of the bone matrix. Optimal staining is achieved with a concentration of 2.5 μl CMFDA (25 μmol) and 5 μl EthD-1 (10 μmol) to 1ml DMEM (Dulbecco's modified Eagle's medium) for a duration of 4 hours at 4oC. These intermediate stain concentrations, low temperatures and short incubation periods limit background staining. We conclude that in contrast to analysing for empty osteocyte lacunae, CMFDA and EthD-1 can stain osteocytes for their viability from the time of injury and thus may aid in an earlier and more precise diagnosis of the percentage of osteocyte necrosis.

RANKL Inhibitors Induce Osteonecrosis of the Jaw in Mice With Periapical Disease

Antiresorptive medications are essential in treating diseases of pathologic osteoclastic bone resorption, including bone cancer and osteoporosis. Bisphosphonates (BPs) are the most commonly used antiresorptives in clinical practice. Although inhibition of bone resorption is important in regulating unwanted malignant and metabolic osteolysis, BP treatment is associated with potential side effects, including osteonecrosis of the jaws (ONJ). Recently, non-BP antiresorptive medications targeting osteoclastic function and differentiation, such as denosumab, have entered the clinical arena. Denosumab treatment results in a similar rate of ONJ as BPs. Animal models of ONJ, using high-dose BP treatment in combination with tooth extraction or dental disease, provide valuable tools and insight in exploring ONJ pathophysiology. However, the ability of other antiresorptives to induce ONJ-like lesions in animal models has not been explored. Such studies would be beneficial in providing support for the role of osteoclast inhibition in ONJ pathogenesis versus a direct BP effect on oral tissues. Here, we tested the ability of the receptor activator of NF-κB ligand (RANKL) inhibitors RANK-Fc (composed of the extracellular domain of RANK fused to the fragment crystallizable [Fc] portion of immunoglobulin G [IgG]) and OPG-Fc (composed of the RANKL-binding domains of osteoprotegerin [OPG] linked to the Fc portion of IgG) to induce ONJ in mice in the presence of periapical disease, but in the absence of dental extractions. We demonstrate radiographic evidence of ONJ in RANK-Fc-treated and OPG-Fc-treated mice, including inhibition of bone loss, increased bone density, lamina dura thickening, and periosteal bone deposition. These findings closely resembled the radiographic appearance of an ONJ patient on denosumab treatment. Histologic examination revealed that RANK-Fc treatment and OPG-Fc treatment resulted in absence of osteoclasts, periosteal bone formation, empty osteocytic lacunae, osteonecrosis, and bone exposure. In conclusion, we have successfully induced ONJ in mice with periapical disease, using potent osteoclast inhibitors other than BPs. Our findings, coupled with ONJ animal models using high-dose BPs, suggest that osteoclast inhibition is pivotal to the pathogenesis of ONJ.

Effect of the alcohol consumption on osteocyte cell processes: a molecular imaging study

We have previously shown microarchitectural tissue changes with cellular modifications in osteocytes following high chronic alcohol dose. The aim of this study was to assess the dose effect of alcohol consumption on the cytoskeleton activity, the cellular lipid content and modulation of differentiation and apoptosis in osteocyte. Male Wistar rats were divided into three groups: Control (C), Alcohol 25% v/v (A25) or Alcohol 35% v/v (A35) for 17 weeks. Bone mineral density (BMD) was assessed by DXA, osteocyte empty lacunae, lacunae surface, bone marrow fat with bright field microscopy. Osteocyte lipid content was analysed with transmission electron microscopy (TEM) and epifluorescence microscopy. Osteocyte apoptosis was analysed with immunolabelling and TEM. Osteocyte differentiation and cytoskeleton activity were analysed with immunolabelling and real time quantitative PCR. At the end of the protocol, BMD was lower in A25 and A35 compared with C, while the bone marrow lipid content was increased in these groups. More empty osteocyte lacunae and osteocyte containing lipid droplets in A35 were found compared with C and A25. Cleaved caspase-3 staining and chromatin condensation were increased in A25 and A35 versus C. Cleaved caspase-3 was increased in A35 versus A25. CD44 and phosphopaxillin stainings were higher in A35 compared with C and A25. Paxillin mRNA expression was higher in A35 versus A25 and C and sclerostin mRNA expression was higher in A35 versus C. We only observed a dose effect of alcohol consumption on cleaved caspase-3 osteocyte immunostaining levels and on the number of lipid droplets in the bone marrow.

Osteogenic Efficacy Enhancement of Kaempferol Through An Engineered Layer-By-Layer Matrix: A Study in Ovariectomized Rats

A layer-by-layer matrix (LBL) comprising kaempferol (LBL-KEM) was prepared for improved osteogenic action. The LBL-KEM consisted of alternate layers of sodium alginate and protamine sulfate, which were sequentially deposited on the preformed kaempferol (KEM)-loaded CaCO3 core (CaCO3-KEM) by LBL self-assembly. The LBL matrix developed was evaluated for layer growth by ζ-potential and size alterations after self-assembly of each layer. Its physicochemical properties and intestinal absorption pattern were characterized and its pharmacokinetic behavior, mineralization of bone marrow cells, bone mineral density, bone strength, microcrack formation and estrogenicity were evaluated after oral administration. The entrapment efficiency of KEM was 94 ± 2% and the cumulative %KEM released from LBL-KEM was 19.2 and 63.5% at pH 1.4 and 7.4, respectively, after 24 h. Stepwise polyelectrolyte assembly onto initially positively charged particles (+21.2 mV) resulted in alterations between -28.5 and +10.9 mV. A final ζ-potential of -8.9 mV was obtained after terminal surface modification with sodium deoxycholate. Fluorescein isothiocyanate-labeled LBL matrix was diffused into the basolateral lacteal region upon oral administration to rats. The area under the KEM serum concentration curve following oral administration of LBL-KEM to rats was 2479 ± 682 ng·h/ml, nearly twofold higher than free KEM. The concentration-time profile in bone marrow indicated improved penetration and retention of KEM on administration of LBL-KEM. Treatment with LBL-KEM restored bone mineralization, bone mineral density, microcrack formation and empty osteocyte lacunae density in ovariectomized (OVx) rats, which was significantly (p < 0.05) improved in femoral diaphysea, tibial head and vertebrae compared with free KEM treatment. Administration of LBL-KEM to growing female rats for 4 weeks resulted in no estrogenicity when compared with OVx rats. The data suggests that LBL matrix enhanced drug delivery, improved pharmacokinetics and maintained better bone quality under OVx conditions.

Ultrastructural and immunohistochemical study of early repair of alveolar sockets after the extraction of molars from alendronate‐treated rats

The aim of the present research was to analyze ultrastructural and immunohistochemical aspects of the alveolar repair after the extraction of molars of alendronate (ALN)-treated rats. Wistar rats received 2.5mg/kg body wt/day of ALN during 14 days previously and 7, 14 and 21 days after the extraction of the second mandibular molar. Specimens were fixed in 2% glutaraldehyde + 2.5% formaldehyde under microwave irradiation, decalcified in 4.13% EDTA and paraffin embedded for TRAP histochemistry and immunohistochemistry for OPN, BSP and endoglin, or embedded in Spurr epoxy resin for TEM analysis. Additional specimens had their soft tissues removed and were processed for scanning electron microscopy. The ALN group presented latent TRAP-positive osteoclasts and nonresorbed alveolar crests with bacterial infection. Mild bone necrosis signs were observed at all time points studied. Ultrastructurally, empty osteocyte lacunae were observed and bone trabeculae surface presented hyalinized aspect. A significant delay in alveolar repair occurred, as well as decreased angiogenesis. ALN treatment provoked mild signs of bone necrosis, despite the high dose employed. The present findings add new information about the ultrastructural aspect of the early repair of rats under ALN treatment and highlight for giving attention when oral surgeries are performed in patients using this drug.

Effects of Chronic Stress and Alendronate Therapy on the Osseointegration of Titanium Implants

The purposes of this study were to evaluate the influence of chronic stress (CS) on implant osseointegration and also to analyze whether alendronate (ALN) therapy could prevent these eventual stress-negative effects. Adult male Holtzmann rats were assigned to one of the four experimental groups: AL (ALN; 1 mg/kg/week; n = 12), ALS (ALN + CS; 1 mg/kg/week; n = 12), CTL (sterile physiological saline; n = 12), or CTLS (sterile physiological saline + CS; n = 12). After 58 days of drug therapy, the ALS and CTLS groups were exposed to CS, and 2 days later all animals underwent tibial implant installation. The animals were euthanized 28 days following the operative surgical procedure. It was observed that the CTLS group presented an impairment of bone metabolism represented by lowest levels of bone-specific alkaline phosphatase and bone area fraction occupancy values. Furthermore, these animals presented a higher proportion of empty osteocytic lacunae. In contrast, the ALN therapy showed increased osseointegration and torque value parameters, regardless of stress exposition. Analysis of the data presented suggests that CS partially impairs the osseointegration of tibial implants and that ALN therapy is able to prevent these negative effects.

Histological findings on jaw osteonecrosis associated with bisphosphonates (BONJ) or with radiotherapy (ORN) in humans

Objective. To describe the histological features of bone tissue harvested from patients affected by jaw osteonecrosis associated with bisphoshponates (BONJ) or with radiotherapy (ORN), in undecalcified ground sections. Materials and methods. Sixteen bone tissue samples from 14 patients with BONJ and two patients with ORN were processed in order to obtain both ground, undecalcified sections and decalcified sections. The sections underwent histometric and morphometric analysis. Results. Bone tissue samples obtained from patients with BONJ or ORN of the jaws shared some histological characteristics. Common histological features included the loss of bone architecture, the absence of a proper Haversian system and proper marrow spaces, the presence of necrotic spots of non-mineralized tissue, areas of empty osteocytic lacunae next to areas of hypercellularity, the presence of resorption pits with rare osteoclast-like cells and the presence of bacteria and of an inflammatory infiltrate. A violet rib of tissue characterized by large resorption pits facing was frequently observed between the mineralized bone and the inflammatory infiltrate. Conclusions. The histological features of BONJ and ORN are similar and resemble those of osteomyelitis. Even though it is not clear whether infection is the cause or consequence of bone exposure, inflammatory cells, bacteria or their products may have a massive, direct lytic effect on bone tissue challenged by bisphosphonates.

Histological, histomorphometric and microtomographic analyses of retrieval hip resurfacing arthroplasty failed at different times

BackgroundMetal-on-metal hip resurfacing arthroplasty (HR) has been gaining popularity especially for young and active patients. Although different series report good mid-term results, the long-term outcome and failure mechanisms are still concerning. In this consecutive revision case series, 9 retrieved specimens of a failed Birmingham Hip Resurfacing (BHR) were divided according to the time to fracture: 3 specimens failed at less than 6 months (Group 1), 3 failed between 6 months and 3 years (Group 2) and 3 failed later than 3 years (Group 3). The objective of the study was to examine by a specific quantitative histomorphometry and microtomography (micro-CT) method the characteristics of bone quality and its microarchitecture in retrieved metal-on-metal HR.MethodsA series of 948 BHR were performed between 2001 and 2009. Among these implants 10 failures occurred and nine of these underwent revision surgery and were examined by histomorphometry and micro-CT.ResultsHistomorphometry showed a significant increase in trabecular separation (Tb.Sp) in Group 3 in comparison with Group 1 (113%, p < 0.05). In the top region, micro-CT showed that Groups 2 and 3 presented significant lower bone volume (Group 2: 61%, p < 0.005; Group 3: 1%, p < 0.05), trabecular number (Group 2: 53%, p < 0.005; Group 3: 40%, p < 0.05), and higher Tb.Sp (Group: 71%,p < 0.05) when compared to Group 1. Additionally, histomorphometry showed that the top regions in Group 1 had a significantly lower mean percentage of empty osteocyte lacunae than the top regions in both Group 2 and 3 (p < 0.05).ConclusionsThis study showed that the morphometric parameters considered are crucial for a good understanding of mechanical properties of HR and may be of significant importance in the pathogenesis of HR failure particularly in the development of late fractures.

Healing of Extraction Sockets and Augmented Alveolar Defects Following 1-Year Treatment With Bisphosphonate

To assess the effect of bisphosphonates on healing of extraction sockets and augmented alveolar defects, 12 adult female mongrel dogs were assigned to 2 experimental groups and a control group. The experimental groups received oral alendronate (ALN, 3.5 mg/kg/wk) or IV pamidronate (PAM, 1 mg/kg/wk) for 12 months. Animals were randomly tested for serum C-terminal telopeptide of collagen I (CTx). The right first and second premolars were extracted. After 8 weeks, extraction sites were evaluated for healing. Subsequently, 3-wall defects were created in ridges and filled with human mineralized cortical particulate bone. Two months post-augmentation, animals were sacrificed and mandibles were collected for cone-beam computed tomography (CBCT) and histomorphometric appraisal. The obtained data were compared using 1-way ANOVA test. CTx test results in both experimental groups were comparable (<10 pg/mL) but lower than that of the control group (minimum 159.2 pg/mL). Two months post-extraction, bone sequestra were noticed in extraction sites in BP-treated groups, involving the entire alveolar bone in the PAM group and the upper rim of the alveoli in the ALN group. Histologically, bone sequestra from the PAM group demonstrated empty osteocyte lacunae, while in the ALN group areas of necrotic bone along with evidence of active bone remodeling was distinguished. Eight weeks post-augmentation, the experimental groups showed no evidence of bone formation in the augmented area, while bone formation ratio was measured to be 18.32% in the control group. The mean amount of pixel intensity calculated from the CBCT images of the ALN, PAM, and control group was 113.69 ± 11.04, 124.94 ± 4.72, and 113.69 ± 6.63, respectively. Pixel intensity in PAM-treated group was significantly higher than both other groups. This study demonstrated that 1-year treatment with ALN/PAM was associated with impairment of post-extraction and post-augmentation bone healing in dogs.

Femtosecond plasma mediated laser ablation has advantages over mechanical osteotomy of cranial bone

Although mechanical osteotomies are frequently made on the craniofacial skeleton, collateral thermal, and mechanical trauma to adjacent bone tissue causes cell death and may delay healing. The present study evaluated the use of plasma-mediated laser ablation using a femtosecond laser to circumvent thermal damage and improve bone regeneration. Critical-size circular calvarial defects were created with a trephine drill bit or with a Ti:Sapphire femtosecond pulsed laser. Healing was followed using micro-CT scans for 8 weeks. Calvaria were also harvested at various time points for histological analysis. Finally, scanning electron microscopy was used to analyze the microstructure of bone tissue treated with the Ti:Sapphire laser, and compared to that treated with the trephine bur. Laser-created defects healed significantly faster than those created mechanically at 2, 4, and 6 weeks post-surgery. However, at 8 weeks post-surgery, there was no significant difference. In the drill osteotomy treatment group, empty osteocyte lacunae were seen to extend 699 ± 27 µm away from the edge of the defect. In marked contrast, empty osteocyte lacunae were seen to extend only 182 ± 22 µm away from the edge of the laser-created craters. Significantly less ossification and formation of irregular woven bone was noted on histological analysis for drill defects. We demonstrate accelerated bone healing after femtosecond laser ablation in a calvarial defect model compared to traditional mechanical drilling techniques. Improved rates of early regeneration make plasma-mediated ablation of the craniofacial skeleton advantageous for applications to osteotomy.

Alcohol‐induced Osteonecrosis – dose and duration effects

We read with great interest the paper by Ikemura et al. published in the August issue of the International Journal of Experimental Pathology (Ikemura et al. 2011). In their study, the authors used a model of alcohol-induced osteonecrosis in rabbits to evaluate the morphological changes in bone marrow fat cells and the changes in the serum lipid levels. Animals received either 15 ml/kg/day (LDA: low-dose alcohol) or 30 ml/kg/day (HDA: high-dose alcohol) of a solution containing 15% ethanol for intragastrically for 4 weeks, whereas a control group received a physiological saline solution. Results were observed at 6 weeks after the beginning of the treatment (i.e. 2 weeks after withdrawal). As these results are difficult to reconcile with aspects of current understanding of alcohol effects on bone metabolism, we would like to comment on their protocol and their results in perspective. Regarding the quantity of alcohol used to induce osteonecrosis, the animals thus ingested either 2.25 g/kg/day (LDA) or 4.5 g/kg/day (HDA) of alcohol. In comparison, Wang et al. (2008) used a dose of 9.2 g/kg/day (i.e. more than twice the amount used in the HDA group) to induce objectively recognizable alcohol-induced osteonecrosis in rabbits, with concomitant marked marrow fat cell hypertrophy and proliferation, thinner and sparse trabeculae, diminished hematopoiesis and increased empty osteocyte lacunae (Wang et al. 2008). In the same manner, Broulik et al.(2010) used a dose of 7.22 g/kg/day of ethanol (corresponding to a consumption of 1 l wine or 2.5 l of 12 ° beer in male adults) to induce bone metabolism disturbances in rats (Broulik et al. 2010). In animal models there may be a cause and effect relationship between alcohol consumption and osteonecrosis of the femoral head (Hirota et al. 1993), but for osteonecrosis to develop in humans, the alcohol exposure threshold is approximately 150 l of 100% ethanol, at a consumption rate of 400 ml or more of absolute ethanol weekly (Cruess 1986; Jones 1994). Therefore, we believe that it is difficult to compare rabbit, rat and human studies with regard to the quantity of alcohol used to induce bone disturbances. Bearing this in mind, we suggest that the lack of osteonecrotic lesions in both LDA and HDA groups might be linked to the fact that the doses of alcohol ingested over 4 weeks was too low a dose of alcohol. We believe that the authors need to justify and discuss their choice of dosage. In addition, the short duration of alcohol treatment (4 weeks) is surprising. The authors do not give an explanation for this duration of alcohol treatment. In comparison, alcohol was administered intragastrically to rabbits for one to 6 months, and changes in lipid metabolism were observed only after 2–3 months of treatment (Wang et al. 2003). In another study, mice were treated with alcohol daily for up to 10 months and significant modifications of lipid metabolism appeared at 6 months, with significant increase in largest fat cell size detectable at 10 months (Wang et al. 2008). Finally, animals were treated with alcohol for 4 weeks, and the results were observed at 6 weeks after the beginning of the treatment, therefore after 2 weeks of withdrawal. The authors do not discuss this aspect of the protocol and its relevance in the aetiology of induced osteonecrosis. A possible explanation is to mimic the clinically relevant symptoms of alcohol withdrawal (Schuckit 2009). However, enlightenment about the impact of this withdrawal on osteonecrosis development would be welcome. Thus, without affecting the reported results, we suggest that the findings are difficult to interpret based upon current understanding of alcohol effects on bone metabolism and that there are protocol-related issues, including dose, duration and eventual withdrawal, which might account for the observations reported.

Suppurative osteomyelitis, bisphosphonate induced osteonecrosis, osteoradionecrosis: a blinded histopathologic comparison and its implications for the mechanism of each disease

Statistically, significant numbers of central bone specimens of suppurative osteomyelitis of the jaws (SOJ), bisphosphonate induced osteonecrosis of the jaws (BIONJ), and osteoradionecrosis of the jaws (ORNJ) were compared. All three evidenced the common finding of necrotic bone with empty osteocytic lacunae, Haversian and Volkmann canals, but each showed a distinctive histopathologic pattern indicating a different disease mechanism and treatment options. Suppurative osteomyelitis was characterized by intense marrow inflammation and marrow vessel thrombosis with retention of viable osteoclasts and periosteum. Bisphosphonate induced osteonecrosis was characterized by an empty marrow space with empty Howship's lacunae and an absence of osteoclasts but viable periosteum. Osteoradionecrosis was characterized by a collagenous hypocellular, hypovascular marrow space and nonviable periosteum. Histologic evidence in SOJ indicates a microorganism provoked intense inflammation and marrow vascular thrombosis creating an environment conducive to continual bacterial proliferation. BIONJ is seen as a non-inflammatory drug toxicity to bone by osteoclastic death leading to over suppression of bone renewal, and ORN as another non-inflammatory condition caused by a high linear energy transfer that impairs or kills numerous cell types in the field of radiation including periosteum, bone, and all soft tissue.

Increased human defensine levels hint at an inflammatory etiology of bisphosphonate-associated osteonecrosis of the jaw: An immunohistological study

BackgroundHuman β-defensins (hBD) are antimicrobial peptides that are an integral part of bone innate immunity. Recently, it could be shown that expression of hBD-1, -2 and -3 were upregulated in cases of osteomyelitis of the jaws. In order to gain insight into the possible impairment of hBD metabolism in bisphosphonate-associated osteonecrosis of the jaws (BONJ), the present exploratory study was designed so as to determine the qualitative and quantitative expression of afore mentioned hBDs in BONJ and infected osteoradionecrosis (ORN), both of which represent inflammatory bone diseases.MethodsBone samples were collected from patients with BONJ (n = 20) and ORN (n = 20). Non-infected healthy bone samples (n = 20) were included as controls. Immunohistological staining in an autostainer was carried out by the (Strept-ABC)-method against hBD-1,-2,-3. Specific positive vs. negative cell reaction of osteocytes (labeling index) near the border of bony resection was determined and counted for quantitative analysis. Number of vital osteocytes vs. empty osteocytes lacunae was compared between groups.ResultshBD-1,-2 and -3 could be detected in BONJ as well as ORN and healthy bone samples. Immunoreactivity against hBD-2 and -3 was significantly higher in BONJ than in ORN and healthy jaw bone samples. Number of empty osteocyte lacunae was significantly higher in ORN compared with BONJ (P = 0.001).ConclusionUnder the condition of BONJ an increased expression of hBD-1,-2,-3 is detectable, similarly to the recently described upregulation of defensins in chronically infected jaw bones. It remains still unclear how these findings may relate to the pathoetiology of these diseases and whether this is contributing to the development of BONJ and ORN or simply an after effect of the disease.

Changes in osteocyte density correspond with changes in osteoblast and osteoclast activity in an osteoporotic sheep model

Histomorphometric assessment of trabecular bone in osteoporotic sheep showed that bone volume, osteoid surface area, bone formation rate, and osteocyte density were reduced. In contrast, eroded surface area and empty lacunae density were increased. Changes in osteocyte density correlated with changes in osteoblast and osteoclast activity. Osteocytes contribute to the regulation of the activity of osteoclasts and osteoblasts that together control bone mass. Osteocytes therefore likely play a role in the loss of bone mass associated with osteoporosis. The purpose of this study was to investigate the relationships between osteocyte lacunar density and other bone histomorphometric parameters in the iliac crest (IC) and lumbar spine (LS) of osteoporotic sheep. Osteoporosis was induced in ten mature ewes by an established protocol involving a combination of ovariectomy, dexamethasone injection, and low calcium diet for 6 months. Five ewes were used as controls. Post-mortem IC and LS biopsies were collected and processed for further histomorphometric assessment. Bone volume, osteoid surface, and bone formation rate in the IC and LS of osteoporotic sheep were reduced compared to those of the controls. In contrast, eroded surface area was increased in osteoporotic sheep. In the osteoporotic group, osteocyte density was reduced in the LS region and to a greater extent in the IC region. The empty osteocyte lacunae were increased 1.7-fold in LS and 2.1-fold in IC in the osteoporotic group. The osteocyte density correlated positively with markers of osteoblast activity and negatively with those of osteoclast activity. Depletion of osteocytes and an increase in the empty lacunae could be important factors contributing to bone loss in this model since they may adversely affect intercellular communication between osteoblasts and osteoclasts. The regional differences in histology suggest that there may be different pathological mechanisms operating at different anatomical sites.

Prevention of alcohol-induced osteonecrosis of femoral head in rabbits by small interfering RNA targeting specific gene by gavage

Objective To observe the effect of small interfering RNA (siRNA) adenovirus vectors targeting PPARγto prevent the alcohol-induced osteonecrosis of the femoral head (ONFH) in rabbits.Methods Ninety-six rabbits were randomly divided into four groups. In group N, normal saline ( 10 ml/kg every day) was poured into stomach. In group M, the strong wine (the volume fraction was 46% alcohol,10 ml/kg every day) was poured into stomach. In group S, under the randomly selected side and anesthesia, the animals were injected with 25 μl siRNA adenovirus drip into the femoral head and then the puncture hole was closed on the 1st day at the 1st, 3rd and 5th month of the experiment, and at the same time the strong wine (the volume fraction was 46% alcohol, 10 ml/kg every day) was poured into stomach. In group CO, animals were treated with the same method as the group S, but not injected with siRNA adenovirus drip. The animals were sacrificed in batches at 2nd, 4th and 6th month after the experiment. The serology and pathological changes of the femoral head were studied. Results At the 6th month, the triglyceride (TG, mmol/L) contents in groups N, M, CO and S were (1.21 ±0. 12), (4.59 ± 1.58), (4.63 ±1.17) and (4. 32 ± 1.20), the cholesterol levels ( CHO, mmol/L) were (2. 35 ± 0. 33), ( 19. 59 ±1.58), (20. 13 ± 1. 17) and ( 18.32 ± 1.20), the average diameter of the max adipocyte (μm) was (40. 89 ± 2. 41 ), (48.65 ± 2.93 ), (49. 45 ± 2. 63 ) and ( 42. 52 ± 2. 57 ), the trabeculace area fraction was (41.80 ±2. 47)%, (30. 70 ±2. 86)%, (29. 80 ±2. 69)% and (41.60 ±2. 87)%, the percentage of empty osteocyte lacunae was (12.30 ± 1.73)%, (22.40 ± 1.52)%, (23. 10 ± 1.62)% and (11.70 ±1.46)%, the expreasion levels of PPARγ mRNA were (0.29 ±0.05), (0.66±0. 12), (0.61±0.15) and (0. 33 ± 0. 05 ), the expression levels of osteocalcin mRNA were (0. 92 ± 0. 07 ), (0. 19 ± 0. 11 ), (0. 23 ±0. 08) and (0. 88 ± 0. 11 ), the expression levels of PPARγprotein were ( 0. 75 ± 0. 08 ), ( 1.60 ± 0. 11 ),(1.55 ±0. 12) and (0.65 ±0.05), respectively. In groups M and CO, the pathological changes were obvious; there was decreased hematopoietic tissue, proliferation and hypertrophy of the adipocytes, increased fatty tissue, and thinned, sparse or breoken bone trabeculae in the femoral head; the area fraction of the trabeculae was reduced. In group S, the average diameter of the max adipocyte, percentage of empty osteocyte lacunae, incidence of ONFH, the expressions of PPARγmRNA and protein were obviously reduced as compared with groups M and CO (P ＜0. 01,P ＜0. 05). There was no statistically significant difference between group S and group N (P ＞ 0. 05). Conclusion siRNA adenovirus vectors targeting PPARγcan efficaciously suppress the expression of PPARγ gene and adipogenic differentiation of the MSCs in the femoral head induced by alcohol, which may prevent the development of the alcohol-induced ONFH in rabbits. Key words: siRNA; PPARγ; Alcohol; Osteonecrosis of femoral head; Rabbit; Prevent

Nitrate patch prevents steroid‐related bone necrosis

Avascular necrosis of the femoral head is a common complication with disabling effect for young patients after high-dose corticosteroid treatment. We could show that steroids have a vasoconstrictive effect on lateral epiphyseal arteries of the femoral head which could lead to ischemia and subsequent necrosis. In this study we investigated the preventive effect of a nitrate patch on steroid-related bone necrosis in a rabbit model. New Zealand White rabbits (male; 3-4.5 kg bodyweight) were injected with 20 mg/kg bodyweight methylprednisolone (GC group; n = 6). Control animals (n = 6) were treated with phosphate-buffered saline. A third group (GC + N; n = 6) additionally received a nitrate patch (0.675 mg/day). Four weeks after i.m. methylprednisolone injection the animals were sacrificed. For histology and immunohistochemistry, tissue samples were fixed in 3% paraformaldehyde, embedded in paraffin, sectioned, dewaxed, and stained with Ladewig. For quantification of empty lacunae, a histologic sign of FHN, histomorphometry was performed. Histomorphometry revealed a significant increase of empty lacunae in glucocorticoid-treated animals compared to controls and GC + N-treated animals. No significant difference in empty lacunae count was detected between the GC + N group and controls. HE staining revealed the different osteocyte amount in the GC versus GC and nitrate patch-treated groups. This study demonstrates an increased number of empty osteocyte lacunae representing a pathologic feature of osteonecrosis, in the GC group. Less empty lacunae were counted in the GC animals after additional treatment with a nitrate patch. This finding suggests that nitrate co-treatment has the potential to prevent steroid-associated FHN.