Role of prostaglandins in interleukin-1-induced bone resorption in mice in vitro

The mechanism of bone resorption induced by interleukin 1 (IL-1) was examined in mice using three different in vitro assay systems: a fetal long bone organ culture system, a bone marrow culture system, and a coculture system of primary osteoblastic cell populations and spleen cells. In the organ culture system, recombinant human IL-1 alpha (rhIL-1 alpha) increased both bone resorption and osteoclast number. Both were partially suppressed in the presence of indomethacin. In the marrow culture, both rhIL-1 alpha and rhIL-1 beta stimulated osteoclastlike cell formation, which was completely inhibited by adding indomethacin concurrently. Furthermore, there was a good correlation between the number of osteoclastlike cells formed and the amount of prostaglandin E2 (PGE2) released into the culture media. This indicates that PGE2 is involved in the mechanism of IL-1-mediated osteoclastlike cell formation. In the coculture of primary osteoblastic cell populations and spleen cells, rhIL-1 again stimulated osteoclastlike cell formation, which was inhibited by adding indomethacin. In the cocultures in which direct interaction between osteoblastic cells and spleen cells was inhibited, PGE2 synthesis was similarly increased but no osteoclastlike cells were formed. These results indicate that IL-1 induces osteoclast formation by a mechanism involving PG (most likely PGE2). Furthermore, direct interaction between osteoclast progenitors and osteoblastic cells is required in the osteoclast recruitment induced by IL-1.     

Changes in mast cell number during the activation phase of an induced synchronized remodeling sequence in the rat

Increase in mast cell (MC) number has been reported in some pathological conditions with increased remodeling. However, it is not known whether MCs are involved in the physiological remodeling of bone. In the present study the possible variations in MCs were investigated during the activation phase in a rat model of synchronized remodeling. Seven groups of 10 rats were used. As early as the first day of induction, MCs increased by 50% and then decreased on day 2. The same pattern of changes recurred on days 3 and 4. Intact non-degranulating MCs increased mainly at some distance from the bone surface. Degranulating MCs conversely decreased near the cambium layer of the periosteum. Prostaglandins were not involved in these changes. These results suggest an association between the events leading to the onset of bone resorption and MCs. Degranulation might induce the release of agents active on these events.     

Systemic zoledronate precoating of a bone graft reduces bone resorption during remodeling

Background Cartilage degeneration often occurs after osteosynthesis of a devascularized intermediary fragment in a joint fracture, in mosaicplasty or in whole-joint toe-to-finger transplantation. Hypothetically, the degeneration is secondary to a collapse of the transferred subchondral bone as it remodels during high mechanical load. Bisphosphonates are used to reduce resorption of necrotic bone. We tested a systemic pretreatment before harvesting the graft in order to protect the bone and cartilage against collapse and secondary arthrosis.

Methods Rats were given one zoledronate injection and bone grafts were harvested. The grafts were frozen, thawed and placed into bone chambers, and implanted into another batch of rats. Graft resorption and new bone formation was measured by histomorphometric analysis and compared with untreated grafts.

Results In the remodeled area of the controls, the graft was almost totally resorbed and replaced by bone marrow. In the zoledronate-treated specimens, the graft remained and the graft trabeculas were lined with new bone. By histomorphometry, the total amount of bone (graft plus new bone) within the remodeled area was 16% in the zoledronate-treated grafts and 5% in the controls (p = 0.003).

Interpretation A bone graft can be pretreated with bisphosphonate and remain protected against resorption once implanted again. ▪     

Systemic zoledronate precoating of a bone graft reduces bone resorption during remodeling

Background?Cartilage degeneration often occurs after osteosynthesis of a devascularized intermediary fragment in a joint fracture, in mosaicplasty or in whole-joint toe-to-finger transplantation. Hypothetically, the degeneration is secondary to a collapse of the transferred subchondral bone as it remodels during high mechanical load. Bisphosphonates are used to reduce resorption of necrotic bone. We tested a systemic pretreatment before harvesting the graft in order to protect the bone and cartilage against collapse and secondary arthrosis.

Methods?Rats were given one zoledronate injection and bone grafts were harvested. The grafts were frozen, thawed and placed into bone chambers, and implanted into another batch of rats. Graft resorption and new bone formation was measured by histomorphometric analysis and compared with untreated grafts.

Results?In the remodeled area of the controls, the graft was almost totally resorbed and replaced by bone marrow. In the zoledronate-treated specimens, the graft remained and the graft trabeculas were lined with new bone. By histomorphometry, the total amount of bone (graft plus new bone) within the remodeled area was 16% in the zoledronate-treated grafts and 5% in the controls (p = 0.003).

Interpretation?A bone graft can be pretreated with bisphosphonate and remain protected against resorption once implanted again.??     

Osteoclast-derived apoptotic bodies couple bone resorption and formation in bone remodeling

Bone remodeling is precisely coordinated by bone resorption and formation.Apoptotic osteoclasts generate large amounts of apoptotic bodies(ABs)marking the end of the bone resorption phase,whereas the functions of osteoclast-derived ABs remain largely unknown.Here,we identified the molecular profile of ABs derived from osteoclasts at distinct differentiation stages and investigated their corresponding functions.ABs were isolated from apoptotic bone marrow macrophages,preosteoclasts,and mature osteoclasts induced by staurosporine.Proteomic signature analysis with liquid chromatography-tandem mass spectrometry suggested marked protein cargo differences among the different ABs.Further bioinformatic analysis showed that the proteomic signatures of the ABs were highly similar to those of their parental cells.Functionally,pOC-ABs induced endothelial progenitor cell differentiation and increased CD31hiEmcnhi endothelial cell formation in a murine bone defect model via their PDGF-BB cargo.mOC-ABs induced osteogenic differentiation of mesenchymal stem cells and facilitated osteogenesis via RANKL reverse signaling.In summary,we mapped the detailed proteomic landscapes of ABs derived from osteoclasts and showed that their potential biological roles are important in coupling bone formation with resorption during bone remodeling.     

Coupling of resorption and formation on bone remodeling sequence in orthodontic tooth movement: A histochemical study

Rat's molars were submitted to orthodontic tooth movement. Bone formation areas were detected using lead-labeling technique. Osteoclasts and osteoblasts were detected by enzyme histochemistry using Tartrate resistant Acid phosphatase (TRACPase) and Alkaline phosphatase (ALPase) to determine simultaneously and mark the 2 types of cells on a same section. The sites selected for study were pressure/distal, tension/mesial and transitional areas of second molars. The results showed that: orthodontic force activated bone remodeling sequence throughout the alveolar bone; slight new bone formation was observed on the cement line on the pressure side. ALPase-positive cells were detected on the pressure side neighboring osteoclasts. On the tension side, bone formation was enhanced in the protrusions whereas both resorption and formation were observed in the depressions. In the transitional area, cellular sequence from osteoclastic bone resorption to bone formation was revealed over the cement line. These findings demonstrated that: coupling phenomena occur on the pressure side but with inhibited osteoblast activity. Bone formation on the tension side involves both promotion of bone formation by the traction force; bone remodeling sequence is established on the tension side by the interaction between osteoclastic bone resorption and bone formation that takes place in the depressions; Coupling phenomena occur in the transitional area as well. Our findings on the pressure side led to the consideration that osteoblastic cells in periodontal ligament would be involved in the regulation of osteoclastic bone resorption. Thus, there appears to be an interaction between osteoclastic and osteoblastic cells and an activated bone remodeling sequence involving the coupling phenomena as a mechanical adaptation to orthodontic force.     

miRNA在骨重建中的作用

微小RNA(micro RNA,miRNA)是一类具有组织特异性或发育阶段特异性表达特征的非编码调控小RNA,近年来,miRNA与骨形成和代谢的关系已成为研究热点之一,许多研究发现miRNA在骨代谢中的调控作用巨大。部分miRNA能够调节骨重建过程中的血管生成以及成骨细胞、破骨细胞的分化,通过改变相关miRNA表达水平进而深入研究miRNA在骨重建中的调控作用,同时miRNA可作为早期检测骨代谢疾病的生物标志物。本文通过对已知的miRNA在骨重建中血管生成及成骨细胞、破骨细胞中生物学和骨病理学作用机制的总结,说明其在骨重建过程中的重要作用。基于miRNA在骨重建中的调控作用,并在骨代谢相关疾病的临床实践中开辟新的领域,进而对骨代谢疾病有治疗作用。     

Increased bone resorption precedes increased bone formation in the ovariectomized rat

This study describes an increase in biochemical and histomorphometric markers of bone resorption prior to increased bone formation and trabecular bone loss in the ovariectomized rat. Six-month-old, female Sprague Dawley rats were either sham operated or ovariectomized (Ovx) and killed at 0, 6, 9, 15, 18, 21, and 42 days postOperation when femora were collected and trabecular bone volume (BV/TV) was determined from von Kossa silver-stained sections using the Quantimet 520 image analysis system in the distal region. A number of these sections were also examined unstained for fluorochrome labels, and stained for acid phosphatase to detect osteoclast-like cells (ACP surface). At 18 days postoperation, lumbar vertebrae were examined. Blood and urine specimens were analyzed for bone-related biochemical variables. ACP surface was significantly greater in Ovx rats compared with sham at 6 days postoperation (mean ACP surface (%TS) ± SEM: sham 36.4 ± 1.9; Ovx 40.3 ± 1.2,P < 0.05) as was urinary hydroxyproline excretion. Serum osteocalcin and alkaline phosphatase activity were not elevated in Ovx rats compared with Sham until 9 days postoperation. Mineral apposition rate (MAR) was increased at 12 days after ovariectomy (mean MAR (Μm/day) ± SEM: sham 0.85 ± 0.06; Ovx 1.23 ± 0.06,P < 0.05). Trabecular bone volume (BV/TV) at a specific site in the metaphyseal-diaphyseal core area was significantly lower at 15 days postoperation (mean (%) ± SEM: Sham 7.40 ± 1.23, Ovx 4.25 0 0.65,P < 0.05). There was no difference in lumbar vertebral BV/TV between the two groups at 18 days postoperation, however, ACP surface was elevated in the Ovx rats (P < 0.05). A systemic increase in bone resorption at 6 days postovariectomy precedes increased formation whereas the length of time required for the dissolution of trabeculae postoperation is determined locally.     

外泌体中miRNA对骨重建过程影响研究进展

骨重建是骨密度和矿物质稳态的重要保证。成骨细胞与破骨细胞间的动态平衡对骨重建至关重要。细胞外囊泡是一组来源于细胞的囊泡,包括外泌体和微囊泡。它们广泛存在于真核生物的体液中并参与了一系列生理和病理过程。外泌体能够通过其内含的蛋白质、脂质和核酸发挥细胞通讯的功能。近年来的研究表明,骨细胞、间充质干细胞、成骨细胞以及破骨细胞所分泌的外泌体能够调节成骨细胞与破骨细胞间的动态平衡,这一过程部分是由外泌体所携带的miRNA实现的。本文将就近年来有关骨源性外泌体中的miRNA对骨重建的影响作一整理探讨。     

Cortical bone remodeling in normal rat

Summary Cortical bone remodeling along the femur diaphysis was determined in normal female rats (Sprague-Dawley) with the tetracycline technique.Three segments on the cortical bone circumference (the anterolateral, the medial, and the posterior) were found to be most suitable for the study of the remodeling process. Oxytetracycline was administered at age 60 and 75 days, and groups of animals were killed at age 75, 85, 95, and 105 days.The accumulated endosteal growth during age 60 to 75 days in the anterolateral segment was found to increase uniformly in the distal direction along the femur diaphysis. A method is described where this accumulated endosteal growth is used. This method eliminates the use of calipers to determine the section level and makes it possible to study comparable sections even after varying periods of time.The proximal part of the diaphysis showed periosteal apposition in all three segments. The periosteal apposition turned into resorption in the distal part of the diaphysis in the anterolateral and medial segments, whereas the periosteal appsition increased in the posterior segment.The endosteal growth increased in the distal direction in the anterolateral and medial segments. Irregular OTC bands made measurements of endosteal remodeling in the posterior segment impossible.The cortical width decreased in the distal direction along the femoral shaft. Comparison between the different age groups is described and also the relation between the accumulated endosteal growth and the diameter of the medullary cavity.     

Role of transforming growth factor-beta in bone remodeling

Transforming growth factor-beta (TGF-beta) plays a critical role in bone remodeling. TGF-beta stimulates matrix protein synthesis, has dramatic effects on the bone cells responsible for bone formation and resorption, and is abundant in bone and bone-conditioned media. Multiple sources of TGF-beta have been described. It was initially purified from platelets. Two distinct forms of TGF-beta have been purified from bone. The second form, TGF-beta II, was initially purified from bone but was then identified in platelets and also as the major TGF-beta in the monkey kidney BSC-1 cell line. The two bone-derived factors were called cartilage-inducing Factor A (CIF-A) and cartilage-inducing Factor B (CIF-B), based on their capacity to induce the formation of extracellular matrix proteins, which are characteristic of cartilage. CIF-A is identical to the TGF-beta purified from platelets, which is called TGF-beta I. CIG-B is the same as TGF-beta II, which was sequenced soon after CIF-B was discovered and characterized. There is 70% sequence homology between the two forms. The largest source of TGF-beta in the body is present in bone (200 micrograms/kg tissue), although the most concentrated source is in platelets. TGF-beta has multiple effects on bone cells depending on their phenotype and/or stage of differentiation. Osteoblasts, the cells responsible for formation of new bone and perhaps cellular control of bone remodeling, are directly affected by TGF-beta, which can induce differentiation or proliferation, depending on the osteoblastic cell type examined. TGF-beta inhibits the formation of osteoclast precursors and bone resorption and, in greater concentrations, has inhibitory effects on isolated osteoclasts, the cells responsible for bone resorption. TGF-beta may act as a bone-coupling factor linking bone resorption to bone formation.     

Cancellous bone resorption in the proximal ilium of the ovariectomized rat

Summary Bone histomorphometry was performed on the proximal ilium of mature Sprague-Dawley rats following ovariectomy, and these rats were compared with sham-operated controls. Bone volume per unit tissue volume (BV/TV), osteoid surface, and the depth and extent of eroded cavities were measured in animals killed at intervals after operation. The rate of bone loss and the mean osteoid surface in the proximal ilium of the ovariectomized rats was significantly greater than that of the control rats over a 210-day postoperative period. The eroded surface and mean trabecular thickness in the proximal ilium of the ovariectomized rats were not significantly different from that of the control rats, and therefore failed to explain the difference in the rate of bone loss. The distribution of the depths of trabecular eroded cavities in the ilium of ovariectomized rats was different from that in the control rats. The loss of trabecular bone mass in the proximal ilium of ovariectomized, mature rats appeared due to increased activity of individual osteoclasts, rather than to increased osteoclast numbers and thinning of trabeculae.     

Implant placement increases bone remodeling transiently in a rat model

To examine bone remodeling following implant placement, 88 female Sprague–Dawley rats underwent either sham ovariectomy (sham‐ovx) or ovariectomy (ovx) at 4.5 months. At 11 months, 17 baseline control animals were euthanized, while 71 rats received bilateral intramedullary femoral implants. Implanted rats were randomized to 4‐, 8‐, or 12‐week follow‐up times. Microcomputed tomography was used to assess cortical area and trabecular architecture in all rats. Dynamic and static histomorphometry were performed in a subset to examine the trabecular and endocortical bone in the distal femoral metaphysis adjacent to the implant and the periosteal surface at the midshaft superior to the implant (n = 59). Implantation did not affect bone volume in either sham‐ovx or ovx rats compared to baseline controls. Implant placement significantly increased mineralizing surface, mineral apposition rate, and bone formation rate in both sham‐ovx and ovx rats at the trabecular and endocortical surfaces at four and sometimes 8 weeks, with a return to baseline values by 12 weeks. At the periosteal surface, implant placement increased bone formation at 4 weeks with a return to baseline levels by 8 weeks. Thus, implant placement increases bone remodeling transiently without affecting bone volume in sham‐ovx and ovx rats. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 800–806, 2013     

Osteoporosis and mandibular bone resorption in the sprague dawley rat

Summary Mandibular bone resorption in normal and osteoporotic rats was measured using standard scintillation techniques for tritiated tetracycline (H3-TC). Thirty-four Sprague-Dawley rats were labeled with H3-TC at 4–9 weeks of age. Ten animals were then sacrificed for baseline radioactivity levels, while 12 experimental animals were given a high protein, low calcium diet, and 12 control animals were given a normal calcium diet. Osteoporotic and normal diets were instituted for 90 days. The results show a significant reduction in the quantity of bone in the experimental group (P<.05) as compared to the control group. In addition, serum samples collected were found to contain significantly elevated (P<.01) alkaline phosphatase level in the experimental group when compared to the control group.     

Role of tumor necrosis factor alpha in particulate-induced bone resorption

The purpose of this study was to determine the role of tumor necrosis factor alpha in bone resorption secondary to mediator release from macrophages exposed to cement particles. The J774 mouse macrophage cell line was exposed to polymethylmethacrylate particles for 24 hours and the resulting conditioned medium was analyzed for prostaglandin E₂, tumor necrosis factor alpha, interleukin-1 alpha and beta, and the ability to stimulate release of prostaglandin E₂ and ⁴⁵Ca from radiolabeled mouse calvaria. Macrophage exposure to polymethylmethacrylate particles led to a 9-fold increase in release of tumor necrosis factor alpha (p < 0.01), but did not lead to a significant increase in release of prostaglandin E₂, interleukin-1 alpha, or interleukin-1 beta when compared to unexposed cells. Exposure of the macrophages to polymethylmethacrylate particles over a time course from 30 minutes to 96 hours led to an increase in the release of tumor necrosis factor alpha that was initially detected at 30 minutes and was maximum at 48 hours. Incubation of the macrophage-polymethylmethacrylate conditioned medium with rat calvaria significantly increased the release of ⁴⁵Ca and prostaglandin E₂ from the bone. To study the role of release of tumor necrosis factor alpha in bone resorption, the macrophage-polymethylmethacrylate conditioned medium was then preincubated with anti-tumor necrosis factor alpha antibody prior to exposure of the conditioned medium to the calvaria. This preincubation was successful in significantly inhibiting ⁴⁵Ca release by calvaria (p < 0.01) to levels that were not significantly different from the levels of release by unexposed calvaria. Tumor necrosis factor alpha appears to play a critical role in initiating particulate-induced bone resorption. Exposure of macrophages to polymethylmethacrylate particles leads to a significant release of tumor necrosis factor alpha in a time-dependent fashion. This macrophage-polymethylmethacrylate conditioned medium stimulated release of prostaglandin E₂ and bone resorption in bone organ culture. The addition of anti-tumor necrosis factor alpha antibody to this in vitro system inhibited the bone resorption stimulated by the macrophage-polymethylmethacrylate conditioned medium and partially suppressed the production of prostaglandin E₂. The sequence of events in this model for particulate-induced bone resorption appears to be initiated by the production of tumor necrosis factor alpha by the macrophage, followed by production of prostaglandin E₂ by cells in bone, and then by bone resorption.     

The effects of metabolic acidosis on bone formation and bone resorption in the rat

Metabolic acidosis (MA) has been implicated in the pathogenesis of both osteomalacia and osteopenia. Alterations in the secretion of parathyroid hormone and in the metabolism of vitamin D may contribute to such skeletal changes. To minimize the influence of these factors, quantitative bone histology and measurements of bone formation using double tetracycline labeling were done in thyroparathyroidectomized (TPTX) rats with MA induced by ammonium chloride (TPTX-A), and in both non-acidotic TPTX (TPTX-C) and intact (C) controls. To evaluate the response of both cortical and trabecular bone to MA, histologic studies were done at three separate sites in the tibia, cortical bone from the mid-shaft, and trabecular bone from the epiphysis and from the metaphysis. Plasma pH was lower in TPTX-A, 7.24 +/- 0.10, than in either TPTX-C, 7.39 +/- 0.03, or C, 7.43 +/- 0.04, P less than 0.01, and urinary hydroxyproline excretion increased from 89.8 +/- 8.7 in TPTX-C to 150.2 +/- 25.9 micrograms/mg/creatinine in TPTX-A, P less than 0.01. Resorption surface at the epiphysis increased from 1.8 +/- 0.6% in TPTX-C to 4.0 +/- 1.6% in TPTX-A, P less than 0.05, values not different from those in C, 3.1 +/- 1.1%. Resorption surface was unchanged at other skeletal sites, but total bone volume at the metaphysis fell from 15.5 +/- 5.6% in TPTX-C to 9.0 +/- 4.3% in TPTX-A, P less than 0.05. Bone formation was reduced at each skeletal site in TPTX-A vs. TPTX-C, P less than 0.05 for all values, but histologic evidence of osteomalacia was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of photodynamic therapy on the periodontitis-induced bone resorption in rat

Lasers in Medical Science - This study aimed to evaluate the effects of toluidine blue–mediated photodynamic therapy (TB-PDT) on the periodontitis-induced bone resorption in periodontitis in...     

Role of gastrointestinal hormones in postprandial reduction of bone resorption.

Collagen type I fragments, reflecting bone resorption, and release of gut hormones were investigated after a meal. Investigations led to a dose escalation study with glucagon like peptide-2 (GLP-2) in postmenopausal women. We found a dose-dependent effect of GLP-2 on the reduction of bone resorption. INTRODUCTION: The C-terminal telopeptide region of type I collagen as measured in serum (s-CTX) can be used to assess bone resorption. This marker of bone resorption has a significant circadian variation that is influenced by food intake. However, the mediator of this variation has not been identified. MATERIALS AND METHODS: We studied the release of the gut hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2; a representative of the intestinal proglucagon-derived peptides) after ingestion of glucose, fat, protein, and fructose, as well as their effects after parenteral administration in relation to bone turnover processes in healthy volunteers. Furthermore, we studied the effect on bone turnover of a single subcutaneous injection of GLP-2 in four different dosages (100, 200, 400, or 800 microg GLP-2) or placebo in 60 postmenopausal women (mean age, 61 +/- 5 years). RESULTS: All macronutrients significantly (p < 0.05) reduced bone resorption as assessed by s-CTX (39-52% from baseline), and only the glucagon-like peptides were secreted in parallel. Parenteral administration of GIP and GLP-1 did not result in a reduction of the s-CTX level, whereas GLP-2 caused a statistically significant and dose-dependent reduction in the s-CTX level from baseline compared with placebo (p < 0.05). Urine DPD/creatinine, a marker of bone resorption, was significantly reduced by 25% from baseline in the 800-microg GLP-2 group (p < 0.01). An area under the curve (AUC(0-8h)) analysis for s-CTX after GLP-2 injection confirmed the dose-dependent decrease (ANOVA, p = 0.05). The s-osteocalcin level was unaffected by the GLP-2 treatment. CONCLUSION: These studies exclude both GIP and GLP-1 as key mediators for the immediate reduction in bone resorption seen after a meal. The dose-dependent reduction of bone resorption markers found after subcutaneous injection of GLP-2 warrants further investigation into the mechanism and importance of GLP-2 for the bone turnover processes.     

Cyclosporin A in the oophorectomized rat: unexpected severe bone resorption

Local factors, such as interleukin-1, may mediate the accelerated bone remodeling in the acute estrogen-deficient rat. Cyclosporin A (CsA), which in vitro inhibits some of these local factors, was administered to oophorectomized (OX) rats in an attempt to modify this high turnover state. Three groups of 15 rats were studied. Group A was sham operated, group B was OX, and group C was OX and received CsA (15 mg/kg per day) by gavage commencing 4 days postoophorectomy for 28 days. Estradiol levels were determined to confirm oophorectomy. Blood was sampled on days -7, 0, 7, 14, 21, and 28 for ionized calcium (Ca2+), 1,25-(OH)2-vitamin D, PTH, and bone gla protein (BGP). Rats received tetracycline hydrochloride for bone histomorphometric labeling. All results were compared to group A. Body weight was increased in group B (p less than 0.003) but not in group C. There was no difference in Ca2+ or PTH between the groups. BGP levels were higher in group B by day 28 (p less than 0.005); BGP levels were increased in group C from days 7-28 (p less than 0.002). 1,25-(OH)2-vitamin D was significantly increased in group C (p less than 0.0001) but not in group B. Tibial bone histomorphometry revealed increased measurements of bone formation and osteoclast number without a loss of bone volume (BV/TV) in group B. Group C showed a dramatic increase in bone turnover with significant loss of BV/TV (p less than 0.001). In conclusion, CsA in the OX rat resulted in unexpected enhanced bone remodeling with high BGP levels and severe bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)