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Bone augmentation using artificial bone is an important option in dental defect prostheses. A bone substitute using carbonate apatite (CO3Ap), an inorganic component of bone, was reported to have promising bone formation and bone replacement ability. However, the osteoinductivity of artificial bone is less than autogenous bone (AB). In this study, CO3Ap with AB is demonstrated as a clinically effective bone substitute. For in vitro experiments, an osteoclast-like cell (RAW-D) was cultured in the presence of AB, CO3Ap, or both (Mix), and the number of osteoclasts was evaluated. Osteoblasts were also cultured under the same conditions, and the number of adherent cells was evaluated. For in vivo experiments, a few holes were created in the rat tibia and AB, CO3Ap, or Mix were added. At 0, 14, and 21 days, the tissue morphology of the wound area was observed, and the thickness of the cortical bone was measured. In vitro, Mix did not increase the number of osteoclasts or osteoblasts. However, in vivo, the rate of bone replacement remarkably increased with Mix on dome-shape. A bone-grafting material combining osteoinductive AB with abundant artificial bone is expected to be clinically easy to use and able to form bone. [ABSTRACT FROM AUTHOR]

Background/Aim: The aim of this study was to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on bone metabolism during the healing period in rat tibiae bone defects using micro--computed tomography (micro CT) imaging for three-dimensional morphological evaluation. Materials and Methods: The right tibia received ultrasound exposure (US group) every day, whereas the opposite side served as a control (Control group). At 1, 2, and 3 weeks after the operation, micro CT was performed, and the volume and surface area of new bone formation in the bone defects was evaluated three-dimensionally. Results: Bone volume (BV) and bone surface (BS) in the tibiae of both the US and Control groups demonstrated the highest values 1 week after the operation, with no significant differences between the groups. At 2 weeks after the operation, the BV and BS values in both groups had decreased, but the decrease was smaller in the US group than the Control group. At 3 weeks after the operation, the BV and BS values in the Control group were significantly lower than those in the US group. Conclusion: LIPUS stimulation can prevent bone loss during the healing of bone defects. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate the effect of topical simvastatin on the osseointegration of machined-surface titanium implants. Material & methods: Sixteen female Sprague–Dawley rats were used in this study in a 4-wk experimental trial. The rats were divided into two groups: a test group (n = 8), in which local simvastatin was applied, and a control group (n = 8). In each of the 16 animals, a machined-surface titanium implant was surgically integrated into the tibial metaphysis. Prior to integration of the implants, 100 μl of ethanol solution containing 5 mg of simvastatin was applied to the bone sockets. The implants were then immediately integrated into the bone sockets. No simvastatin treatment was applied in the control group. At the end of the 4-wk period, the rats were sacrificed, and the implants and surrounding bone tissue were removed. The bone–implant contact (BIC) and bone filling (BF) ratios of nondecalcified histological sections were then determined. The BIC ratio was defined as the ratio of the implant surface directly in contact with the bone to the total implant surface length. The BF ratio was determined by measuring the bone-filled area at a distance of 0.5 mm from implant. Results: There were no statistically significant differences in the BIC and BF ratios of the test group and control group in terms of implant osseointegration (p > 0.05). Conclusion: Within the limitations of this study, we conclude that topically applied simvastatin to implant surfaces does not affect osseointegration.

Objective: We aimed to investigate effects of different concentrations (0.5-5%) of Sodium Hypochlorite (NaOCl) solution on healthy tissues, and determine the optimal concentration that does not harm to tissue. Materials and Methods: 30 tibias of 15 male Wistar albino rats were used. The tibias were randomly divided into 5 groups (Salin, 0.5%, 1%, 2.5%, and 5% NaOCl). Tibias were reamed intramedullary, and irrigated with 20 ml of saline or increasing concentrations of (0.5-5%) NaOCl. The tibias were embedded in paraffin and the sections were stained with hematoxylin-eosin. All sections were assessed for edema, acute inflammation, or necrosis according to their density, in bone marrow and soft tissues. Results: Pairwise comparisons revealed that irrigation of tibia with saline or 0.5% NaOCl solutions was not statistically significant in terms of necrosis in the bone marrows (p=0.320). However, irrigation of rat tibia with saline caused less necrosis in the bone marrows compared to high concentrations (1%, 2.5%, and 5%) of NaOCl (saline and 1% NaOCl, p=0.017; saline and 2.5% NaOCl, p=0.0007; saline and 5% NaOCl, p=0.001). Conclusion: As an irrigation solution, the effects of 0.5% NaOCl are similar to those of saline in terms of edema, inflammation, and necrosis. There is a need for evaluation of necrosis for extended periods such as one week or one month by immunohistochemical methods and flow cytometry. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of topical simvastatin on the osseointegration of machined-surface titanium implants. Sixteen female Sprague–Dawley rats were used in this study in a 4-wk experimental trial. The rats were divided into two groups: a test group (n = 8), in which local simvastatin was applied, and a control group (n = 8). In each of the 16 animals, a machined-surface titanium implant was surgically integrated into the tibial metaphysis. Prior to integration of the implants, 100 μl of ethanol solution containing 5 mg of simvastatin was applied to the bone sockets. The implants were then immediately integrated into the bone sockets. No simvastatin treatment was applied in the control group. At the end of the 4-wk period, the rats were sacrificed, and the implants and surrounding bone tissue were removed. The bone–implant contact (BIC) and bone filling (BF) ratios of nondecalcified histological sections were then determined. The BIC ratio was defined as the ratio of the implant surface directly in contact with the bone to the total implant surface length. The BF ratio was determined by measuring the bone-filled area at a distance of 0.5 mm from implant. There were no statistically significant differences in the BIC and BF ratios of the test group and control group in terms of implant osseointegration (p > 0.05). Within the limitations of this study, we conclude that topically applied simvastatin to implant surfaces does not affect osseointegration. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the systemic effect of thymoquinone (TQ) on bone healing by starting TQ administration, either 40 days before, or on the day of the surgical procedure and continuing during the healing period of 28 days. Eighteen experimental rats were divided into three groups and defects were created in their tibias. The following procedures were performed for each group: Control group (C): No systemic drug administration (n = 6); Test group 1 (T1): Systemic TQ was administered daily starting 40 days before creation of the defect and additionally during the post-operative healing period of 28 days (n = 6); Test group 2 (T2): Systemic TQ was administered daily after creation of the defect and during the healing period of 28 days (n = 6). Quantitative measurement for new bone formation, osteoblast lining and semi-quantitative measurement of capillary intensities were examined and statistically analysed. There was a significant increase in the ratio of new bone per total defect area and new bone trabeculae lined by active osteoblasts in both test groups (T1 and T2) compared to control group (p < 0.05). However the difference between T1 and T2 was not statistically significant. TQ-administered groups also showed an increase in capillary intensity in the defect area compared to the control group (p < 0.05). Systemic administration of TQ either starting 40 days before or on the day of surgery accelerated new bone formation in a rat model and can be advocated as an adjunct to expedite bone healing.

The aim of the present study was to assess the systemic effect of thymoquinone (TQ) on bone healing by starting TQ administration, either 40 days before, or on the day of the surgical procedure and continuing during the healing period of 28 days. Eighteen experimental rats were divided into three groups and defects were created in their tibias. The following procedures were performed for each group: Control group (C): No systemic drug administration (n= 6); Test group 1 (T1): Systemic TQ was administered daily starting 40 days before creation of the defect and additionally during the post-operative healing period of 28 days (n= 6); Test group 2 (T2): Systemic TQ was administered daily after creation of the defect and during the healing period of 28 days (n= 6). Quantitative measurement for new bone formation, osteoblast lining and semi-quantitative measurement of capillary intensities were examined and statistically analysed. There was a significant increase in the ratio of new bone per total defect area and new bone trabeculae lined by active osteoblasts in both test groups (T1 and T2) compared to control group (p< 0.05). However the difference between T1 and T2 was not statistically significant. TQ-administered groups also showed an increase in capillary intensity in the defect area compared to the control group (p< 0.05). Systemic administration of TQ either starting 40 days before or on the day of surgery accelerated new bone formation in a rat model and can be advocated as an adjunct to expedite bone healing. [ABSTRACT FROM PUBLISHER]

Low-magnitude high-frequency loading, applied by means of whole body vibration (WBV), affects the bone. Deconstructing a WBV loading stimulus into its constituent elements and investigating the effects of frequency and acceleration individually on bone tissue kinetics around titanium implants were aimed for in this study. A titanium implant was inserted in the tibia of 120 rats. The rats were divided into 1 control group (no loading) and 5 test groups with low (L), medium (M) or high (H) frequency ranges and accelerations [12-30 Hz at 0.3× g ( F A); 70-90 Hz at 0.075× g ( F A); 70-90 Hz at 0.3× g ( F A); 130-150 Hz at 0.043× g ( F A); 130-150 Hz at 0.3× g ( F A)]. WBV was applied for 1 or 4 weeks. Implant osseointegration was evaluated by quantitative histology (bone-to-implant contact (BIC) and peri-implant bone formation (BV/TV)). A 2-way ANOVA (duration of experimental period; loading mode) with α = 0.05 was performed. BIC significantly increased over time and under load ( p < 0.0001). The highest BICs were found for loading regimes at high acceleration with medium or high frequency ( F A and F A), and significantly differing from F A and F A ( p < 0.02 and p < 0.005 respectively). BV/TV significantly decreased over time ( p < 0.0001). Loading led to a site-specific BV/TV increase ( p < 0.001). The highest BV/TV responses were found for F A and F A, significantly differing from F A ( p < 0.005). The findings reveal the potential of high-frequency vibration loading to accelerate and enhance implant osseointegration, in particular when applied at high acceleration. Such mechanical signals hold great, though untapped, potential to be used as non-pharmacologic treatment for improving implant osseointegration in compromised bone. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to examine the influence of immediate and early loading on dynamic changes in bone metabolism around dental implants using bone scintigraphy. Material and methods: Two titanium implants were inserted in the right tibiae of 21 rats. Closed coil springs with 4.0-N loads were applied parallel to the upper portion of the implants for 35 days. According to the load application timing, rats were divided into three groups: immediate loading (IL) group, early loading 1 day after implant insertion (1-D early loading [EL]) group, and loading 3 days after implant insertion (3-D EL) group. Rats were intravenously injected with technetium-99 m-methylene diphosphonate (Tc99 m-MDP) (74 MBq/rat) and scanned by bone scintigraphy at 1, 4, 7, 11, 14, 21, 28, and 35 days after load application. The ratio of accumulation of Tc99 m-MDP around the implants to that of a reference site (uptake ratio) was calculated to evaluate bone metabolism. Results: In every group, the uptake ratio increased until 7 days after load application and then gradually decreased. It was significantly higher than baseline at 4, 7, 11, and 14 days (P < 0.001). The uptake ratio in the 1-D EL and 3-D EL groups were significantly higher than that in the control group and also that in the IL group (P < 0.001). Conclusions: Bone metabolism initially increased and then gradually decreased to baseline despite differences in load timing. Increases in bone metabolic activity differed according to load application timing; the later the load application, the more enhanced the bone metabolism. [ABSTRACT FROM AUTHOR]

Bioactive glass scaffolds (70S30C; 70% SiO2 and 30% CaO) produced by a sol–gel foaming process are thought to be suitable matrices for bone tissue regeneration. Previous in vitro data showed bone matrix production and active remodelling in the presence of osteogenic cells. Here we report their ability to act as scaffolds for in vivo bone regeneration in a rat tibial defect model, but only when preconditioned. Pretreatment methods (dry, pre-wetted or preconditioned without blood) for the 70S30C scaffolds were compared against commercial synthetic bone grafts (NovaBone® and Actifuse®). Poor bone ingrowth was found for both dry and wetted sol–gel foams, associated with rapid increase in pH within the scaffolds. Bone ingrowth was quantified through histology and novel micro-CT image analysis. The percentage bone ingrowth into dry, wetted and preconditioned 70S30C scaffolds at 11weeks were 10±1%, 21±2% and 39±4%, respectively. Only the preconditioned sample showed above 60% material–bone contact, which was similar to that in NovaBone and Actifuse. Unlike the commercial products, preconditioned 70S30C scaffolds degraded and were replaced with new bone. The results suggest that bioactive glass compositions should be redesigned if sol–gel scaffolds are to be used without preconditioning to avoid excess calcium release. [ABSTRACT FROM AUTHOR]

Abstract: Amongst cancers with poor prognosis those originating from breast commonly metastasise to the skeleton for the high affinity of breast cancer cells to bone. A3 adenosine receptor (A3AR) agonists were found to be potent anti-tumour agents even if their effect on bone-residing breast cancer has not yet been investigated. An animal model of surgery-induced metastasis was used to mimic the human condition in an attempt to develop a novel effective treatment strategy. Sprague–Dawley rats receiving intra-tibial injections of syngeneic MRMT-1 rat mammary gland carcinoma cells developed cancer-associated osteolytic lesions and structural damage that were monitored by microcomputed tomography imaging and histological analysis. To address the involvement of A3ARs in tumour-related signalling pathway, A3AR expression and functional role were analysed in MRMT-1 cells. The effect of chronic treatment with an A3AR agonist, 2-chloro-N 6-(3-iodobenzyl)-adenosine-5′-N-methyl-uronamide (Cl-IB-MECA) in comparison with cisplatin, was evaluated on rat tumour growth and bone cancer pain. A3ARs were expressed in MRMT-1 cells and their activation reduced NF-kB, increased p53 expression and apoptosis, inhibited tumour cell proliferation and migration. In vivo Cl-IB-MECA administration, started on day 1 after tumour cell injection, produced a significant reduction in tumour growth and cancer pain. Cl-IB-MECA treatment, performed on days 5 and 10 after the tumour cell inoculation, revealed the capability of A3AR stimulation to partially reduce tumour progression. Our findings highlighted the effectiveness of A3AR stimulation in the inhibition of breast tumour-derived bone metastasis growth strongly suggesting that targeting A3ARs may have promising therapeutic value in the treatment of bone-residing breast cancer. [Copyright &y& Elsevier]

The aim of this study was to evaluate the effect of low-magnitude, high-frequency (LMHF) loading, applied by means of whole-body vibration (WBV), on peri-implant bone healing and implant osseointegration in rat tibiae. A custom-made titanium implant was inserted into the proximal metaphysis of the tibiae of 42 rats and left to heal for 3, 7, 14 or 25 days. Half of the animals received LMHF mechanical vibration for 5 days per week (test), whereas the others served as unloaded controls. The WBV consisted of 15 consecutive frequency steps (12, 20, 30, ... to 150 Hz). Each of the 15 frequencies was applied for 2000 cycles, at an acceleration of 0.3 g. In the group with a 25-day healing period, PET images were taken at −1 (day before surgery), 3, 5, 7, 10, 14 and 21 days of loading, after an injection of [F]sodium fluoride, a positron-emitting tracer. The ratio of the metabolic activity around the implants to that of a reference site (uptake ratio) was calculated as a measure of bone metabolism. Bone-to-implant contact (BIC) and peri-implant bone fraction (BF) were analysed for histomorphometrical measurement. The mean BIC and BF were significantly influenced by both the loading and the healing time (ANOVA, P<0.01). The PET images did not reveal any significant difference in uptake ratio between the test and the control implants. LMHF loading increased BIC and BF significantly. The results confirm the bone-stimulating potential of LMHF loading, through WBV, on peri-implant bone healing and osseointegration. Ogawa T, Zhang X, Naert I, Vermaelen P. Deroose CM, Sasaki K, Duyck J. The effect of whole-body vibration on peri-implant bone healing in rats. Clin. Oral Impl. Res. , 2011; 302-307. doi: 10.1111/j.1600-0501.2010.02020.x [ABSTRACT FROM AUTHOR]

The article focuses on low-magnitude, high-frequency (LMHF) loading, whole-body vibration's effect on peri-implant bone healing. In the study conducted by the authors, they used ninety-five male Wistar rats, which has an average weight of 353.7 grams, that was subjected to an implant in the medio-proximal site of its one tibia with the use of a custom-made titanium. The authors conclude based on their study that LMHF loading can stimulate peri-implant bone healing and formation if it is done in a particular time sequence.

Abstract: We evaluated the local response of cortical bone in the rat tibia due to combined treatment with synthetic parathyroid hormone, hPTH-(1-34), and mechanical stimulation by four-point bending. Forty-eight female retired breeder Sprague-Dawley rats were divided into six groups. Mechanically stimulated animals included the following groups: (1) Bend+PTH, (2) Sham+PTH, (3) Bend+Vehicle, (4) Sham+Vehicle. Non-mechanically stimulated animals included a (5) Control group that received neither loading nor injections, and a (6) PTH group that received only hPTH-(1-34) injections. The right limbs of mechanically loaded animals were exposed to a peak force of 50N for 36 cycles at 2Hz, three days per week for four weeks, and PTH-treated animals received injections equivalent to 50μg/kg BW. Fluorochrome labeling was used to measure local formation at 12 sectors about the endocortical periphery. The distributions of endocortical bone formation were compared to the local formation differences between treatment groups and to a variety of potential mechanical stimuli signals. Results indicated that hPTH-(1-34) exerted a potent anabolic effect with near-uniform formation about the endocortical surface, and that localized formation peaks due to bending were further augmented in the presence of hPTH-(1-34) treatment. Correlation of formation patterns to mechanical signal distributions highlighted several candidate signals including the mid-principal stress, the dilatational strain, and the radial gradient of the local radial strain. [Copyright &y& Elsevier]

Different types of calcium phosphate compounds are commercially available for medical and dental applications as bone substitute materials. Biological apatites contain several kinds of minor elements such as carbonate (CO3), magnesium (Mg), and fluoride (F) in enamel, dentin, and bone. It has been shown that F ion and F-substituted apatite promoted osteoblast proliferation and inhibited osteoclast cell activity. The purpose of this study was to investigate the in vivo rat tibia activity on F-substituted apatite (FAp). Apatites of unsintered calcium deficient apatite (CDA), and FAps, with low, medium, and high F concentrations, were implanted in rat tibia for 1 and 2 weeks. Implanted tissues were embedded in paraffin blocks. stained with hematoxylin-eosin and histomorphometrically observed. Results showed that low F concentration induced better and faster new bone formation in vivo compared to CDA. Therefore the results suggested that F as a minor element in bone rendered a suitable effect on bone formation in vivo. [ABSTRACT FROM AUTHOR]

Renal failure (RF) is a serious disease of relatively high incidence, known to cause bone alterations. RF patients frequently suffer anemia, which is usually treated with iron. Given that iron overload inhibits bone formation, the aim of the present study was to evaluate the effect of iron on the subchondral bone of rat tibiae, using a model of renal failure. Male Wistar rats were subjected to experimental nephrectomy in order to induce renal failure and to iron overload by daily intraperitoneal injections of 88 mg/kg body weight of iron-dextran for 16 days. Tetracyclines were injected intraperitoneally to evaluate dynamic parameters of bone. Undecalcified histological sections of the tibiae were obtained. Serum urea, creatinine, and paratohormone (PTH) levels were evaluated 30 days after the onset of the experiment. Static and dynamic histomorphometric measurements were performed. Iron overload modified the response of the animals with renal failure: a reduction in bone forming activity compatible with adynamic bone disease and a decrease in peritrabecular fibrosis were observed. Our results suggest that iron is yet one more factor involved in the imbalance in bone metabolism typically found in renal failure patients treated with iron, rendering diagnosis and treatment of bone disease in these patients more complex. [ABSTRACT FROM AUTHOR]

Micro-computed tomography (micro-CT) allows for classical anatomical imaging well suited to the study of skeletal structures. Recent improvements in spatial resolution and the ability to assess cancellous bone microstructure more efficiently has led to an increase in the number of micro-CT users in both academic and commercial environments. Accurate and reproducible positioning of bone samples and image acquisition time are two limiting factors that every bio-imaging laboratory must deal with. Therefore, method improvements that may save time or improve quality and reproducibility of data are always welcome. Here, we present an “alternative” approach for performing two- (2D) and three-dimensional (3D) analysis of bone tissue using in vitro micro-CT technology. The proposed method for acquiring longitudinal images of long bones has several advantages over the “conventional” scanning method of generating axial images. The proposed method allows for more accurate and reproducible positioning of specimen for single and multi-sample scans while providing higher-resolution image sets in substantially less time, compared to the “conventional” method. In addition, longitudinal images generated with the proposed method are comparable to views obtained by classic bone histology and, thus, are more informative to bone scientists, providing an opportunity to assess cancellous bone of the metaphysis and/or epiphysis, evaluate longitudinal bone growth, and finally to more accurately and reproducibly define regions of interest on image. [Copyright &y& Elsevier]

Matrix metalloproteinase (MMP)-13 (an interstitial collagenase also called collagenase 3) is involved in degradation of extracellular matrix in various tissues. Using immunohistochemistry and Western blotting, we investigated localization of MMP-13 in rat tibia, to clarify the role of MMP-13 in bone resorption.MMP-13 reactivity was mainly seen on bone surfaces under osteoclasts, and in some osteocytes and their lacunae near osteoclasts. However, immunoreactivity was not seen in chondrocytes or osteoclasts. MMP-13 was also localized on cement lines in the epiphysis. In the growth plate erosion zone, perivascular cells showed MMP-13 reactivity. Immunoelectron microscopy revealed that MMP-13 was localized on the bone surfaces, under the ruffled borders and some clear zones of osteoclasts. Gold-labeled MMP-13 was closely associated with collagen fibrils. Gold labeling was also detected in Golgi apparatus of osteocytes adjacent to osteoclasts and bone lining cells. Western blotting showed that MMP-13 was mainly associated with mineralized bone matrix. These findings suggest that MMP-13 synthesized and secreted by osteoblast-lineage cells is localized under the ruffled borders of osteoclasts. MMP-13 may play an important role in degradation of type I collagen in bone matrix, acting in concert with cathepsin K and MMP-9 produced by osteoclasts. MMP-13 in perivascular cells may be involved in removal of cartilage matrix proteins such as type II collagen and aggrecan. [Copyright &y& Elsevier]

Although the rat is the most common animal model used in studying osteoporosis, it is often used inappropriately. Osteoporosis is a disease that most commonly occurs in humans long after growth plate fusion with the associated cessation of longitudinal bone growth, but there has been a question as to when or to what extent the rat growth plate fuses. To investigate this question, we used microcomputed X-ray tomography, at voxel resolutions ranging from (5.7 μm)3 to (11 μm)3, to image the proximal epiphyseal growth plates of both male (n = 19) and female (n = 15) rat tibiae, ranging in age from 2 to 25 months. The three-dimensional images were used to evaluate fusion of the epiphyseal growth plate by quantitating the amount of cancellous bone that has bridged across the growth plate. The results suggest that the time course of fusion of the epiphyseal growth plate follows a sigmoidal pattern, with 10% of the maximum number of bridges having formed by 3.9 months in the male tibiae and 5.8 months in the female tibiae, 50% of the maximum number of bridges having formed by 5.6 months in the male tibiae and 5.9 months in the female tibiae, and 90% of the total maximum of bridges have formed by 7.4 months for the males and 6.5 months for the females. The total volume of bridges per tibia at the age at which the maximum number of bridges per tibia has first formed is 0.99 mm3/tibia for the males and 0.40 mm3/tibia for the females. After the maximum number of bridges (−290 for females, −360 for males) have formed the total volume of bridges per tibia continues to increase for an additional 7.0 months in the males and 17.0 months for the females until they reach maximum values (−1.5 mm3/tibia for the males and −2.2 mm3/tibia for the females). [Copyright &y& Elsevier]

Prostaglandins mediate adaptive bone formation induced by mechanical loading. Inhibition of cyclooxygenase-2 (COX-2) with NS-398 effectively blocks loading-induced osteogenesis on the endocortical bone surface of the tibia. In this study, we compared the effects of selective inhibition of COX-2 with NS-398 on mechanically induced osteogenesis at the endocortical surface (tibia) with that on the periosteal surface (ulna). We further tested the effect of NS-398 administered at different times before (3 hrs or 30 min) or after (30 min) mechanical loading. Mechanical loading induced lamellar bone formation on the endocortical surface of the tibia and the periosteal surface of the ulna. Oral administration of either indomethacin or NS-398 3 hrs before loading significantly decreased loading-induced bone formation rate (BFR) and mineralizing surface (MS/BS), but not mineral apposition rate (MAR), at the endocortical surface of the tibia and the periosteal surface of the ulna. NS-398 reduced loading-induced MS/BS by 96% on the endocortical surface of the tibia, but only by 37% on the periosteal surface of the ulna (significantly different from endocortical, P <0.05). Indomethacin reduced MS/BS and BFR to a lesser extent than NS-398 and did not have different effects on the periosteal and endocortical surfaces. These data suggest that the endocortical bone adaptive response to mechanical loading is more dependent upon COX-2 activity than is the periosteal bone response. Intraperitoneal injection of NS-398 3 hrs before loading suppressed load-induced bone formation rate at the endocortical surface of the tibia significantly more (27%) than when administered 30 min before loading. When NS-398 was given 30 min after loading, bone formation was not significantly suppressed. These data suggest that a primary cellular mechanism of bone formation following brief bouts of mechanical loading involves release of prostaglandins from cells at the time mechanical loading is applied, rather than new prostaglandin synthesis associated with a mechanically induced COX-2 expression. [ABSTRACT FROM AUTHOR]

Bone mass and microarchitecture are the main determinants of bone strength. Three-dimensional micro-computed tomography has the potential to examine complete bones of small laboratory animals with very high resolution in a non-invasive way. In the presented work, the proximal part of the tibiae of hindlimb unloaded and control rats were measured with 3D MicroCT, and the secondary spongiosa of the scanned region was evaluated using direct evaluation techniques that do not require model assumptions. For determination of the complete bone status, the cortex of the tibiae was evaluated and characterised by its thickness. It is shown that with the proposed anatomically conforming volume of interest (VOI), up to an eight-fold volume increase can be evaluated compared to cubic or spherical VOIs. A pronounced trabecular bone loss of -50% is seen after 23 days of tail suspension. With the new evaluation techniques, it is shown that most of this bone loss is caused by the thinning of trabeculae, and to a lesser extent by a decrease in their number. What changes most radically is the structure type: the remaining bone is more rod-like than the control group's bone. Cortical bone decreases less than trabecular bone, with only -18% after 23 days. [ABSTRACT FROM AUTHOR]

Background/aim: The aim of this study was to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on bone metabolism during the healing period in rat tibiae bone defects using micro-computed tomography (micro CT) imaging for three-dimensional morphological evaluation., Materials and Methods: The right tibia received ultrasound exposure (US group) every day, whereas the opposite side served as a control (Control group). At 1, 2, and 3 weeks after the operation, micro CT was performed, and the volume and surface area of new bone formation in the bone defects was evaluated three-dimensionally., Results: Bone volume (BV) and bone surface (BS) in the tibiae of both the US and Control groups demonstrated the highest values 1 week after the operation, with no significant differences between the groups. At 2 weeks after the operation, the BV and BS values in both groups had decreased, but the decrease was smaller in the US group than the Control group. At 3 weeks after the operation, the BV and BS values in the Control group were significantly lower than those in the US group., Conclusion: LIPUS stimulation can prevent bone loss during the healing of bone defects., (Copyright © 2022, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

The purpose of this study was to determine how corticosteroid-induced osteopenia in rats develops by using conventional bone histomorphometry and node-strut analysis. Seven-month-old female Wistar rats were divided into three groups: an untreated control group, a low corticosteroid dose group (prednisolone, 2.5 mg kg−1 day−1), and a high corticosteroid dose group (prednisolone, 12,5 mg kg−1 day−1). Prednisolone was administered six times each week for 4 and 8 weeks. At necropsy, the left tibiae were collected, and sections were prepared using Villanueva's bone stain. Histomorphometrically, corticosteroid at both doses reduced the trabecular thickness at the 4th week, and significant bone loss was established at the 8th week with strong suppression of bone formation. In node-strut analysis, neither node-related nor terminus-related parameters changed significantly in any group at either treatment duration. These results indirectly suggest that trabecular thickness is reduced but the trabecular network is preserved in corticosteroid-induced osteopenia in rats. [ABSTRACT FROM AUTHOR]

Although mechanical forces regulate bone mass and morphology, little is known about the signals involved in that regulation. External force application increases periosteal bone formation by increasing surface activation and formation rate. In this study, the early tibial periosteal response to external loads was compared between loaded and nonloaded contralateral tibia by examining the results of blot hybridization analyses of total RNA. To study the impact of external load on gene expression, RNA blots were sequentially hybridized to cDNAs encoding the protooncogene c-fos, cytoskeletal protein beta-actin, bone matrix proteins alkaline phosphatase (ALP), osteopontin (Op), and osteocalcin (Oc), and growth factors insulin-like growth factor I (IGF-I) and transforming growth factor-beta (TGF-beta). The rapid yet transient increase in levels of c-fos mRNA seen within 2 hours after load application indirectly suggests that the initial periosteal response to mechanical loading is cell proliferation. This is also supported by the concomitant decline in levels of mRNAs encoding bone matrix proteins ALP, Op, and Oc, which are typically produced by mature osteoblasts. Another early periosteal response to mechanical load appeared to be the rapid induction of growth factor synthesis as TGF-beta and IGF-I mRNA levels were increased in the loaded limb with peak levels being observed 4 hours after loading. These data indicate that the acute periosteal response to external mechanical loading was a change in the pattern of gene expression which may signal cell proliferation. The altered pattern of gene expression observed in the present study supports previous evidence of increased periosteal cell proliferation seen both in vivo and in vitro following mechanical loading. [ABSTRACT FROM AUTHOR]