Osteoclast depletion with clodronate liposomes delays fracture healing in mice

Osteoclasts are abundant within the fracture callus and also localize at the chondro‐osseous junction. However, osteoclast functions during fracture healing are not well defined. Inhibition of osteoclast formation or resorptive activity impairs callus remodeling but does not prevent callus formation. Interestingly, though anti‐osteoclast therapies differentially affect resolution of callus cartilage into bone. Treatments that inhibit osteoclast formation or viability tend to impair callus cartilage resolution, while treatments that target inhibition of bone resorption generally do not affect callus cartilage resolution. Here, we tested whether depletion of osteoclasts by systemic treatment with clodronate liposomes would similarly impair callus cartilage resolution. ICR mice were treated by intraperitoneal injections of clodronate‐laden liposomes or control liposomes and subjected to closed femur fracture. Femurs were resected at multiple times after fracture and analyzed by radiography, histology, and mechanical testing to determine effects on healing. Clodronate liposome treatment did not prevent callus formation. However, radiographic scoring indicated that clodronate liposome treatment impaired healing. Clodronate liposome treatment significantly reduced callus osteoclast populations and delayed resolution of callus cartilage. Consistent with continued presence of callus cartilage, torsional mechanical testing found significant decreases in callus material properties after 28 days of healing. The results support a role for osteoclasts in the resolution of callus cartilage into bone. Whether the cartilage resolution role for osteoclasts is limited to simply resorbing cartilage at the chondro‐osseous junction or in promoting bone formation at the chondro‐osseous junction through another mechanism, perhaps similar to the reversal process in bone remodeling, will require further experimentation. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1699–1706, 2017.

     

Traumatic late dissociation of the polyethylene articulating surface in a total knee arthroplasty--a case report

Clodronate was administered daily 28 days before and after an experimental tibial fracture in 35 male rats, and the effect on fracture healing and posttraumatic bone loss was studied. 5 groups were tested. The clodronate/clodronate group received clodronate in daily doses of 10 mg/ kg body weight for 28 days before being subjected to a standardized fracture of the right tibia, and during the fracture healing period of 28 days. The clodronate/ saline group received clodronate before fracture and saline during the healing period. The saline/ clodronate group received saline before and clodronate after fracture. The saline/saline group received saline only, while the control group served as unfractured, untreated controls. After 28 days of fracture healing, the tibias were evaluated with dual energy x-ray absorptiometry, and tested mechanically in a 3-point ventral bending test. Bone mineral content and bone mineral density were approximately 30% higher in the groups receiving clodronate during the experiment, compared to the untreated groups. The weight and cross-sectional area of the fracture callus were equal in all groups. Whether clodronate was administered before the fracture, after the fracture or both, did not affect the bone mineral. Ultimate bending moment, energy absorption, stiffness and deflection were not significantly different between the groups. Our findings suggest that clodronate increases bone mineral both when given before and after a tibial shaft fracture, without affecting fracture healing at 28 days.     

Effect of clodronate on fracture healing in denervated rats

The effect of clodronate on healing of the fracture of osteopenic bone was studied in rats. A total of 165 female rats (14 ± 1 weeks, 216 ± 2 g) were divided into five fracture groups (n = 30), and a neurectomized group (n = 15). Osteopenia (op) was induced by right sciatic neurectomy 4 weeks before the fracture. Nonosteopenic (nop) rats were not operated. A closed prepinned diaphyseal fracture of the right femur was done by three-point bending method both to op and nop rats, and the left femur served as an unoperated control. All the fracture groups were divided into treatment (clodronate 10 mg/kg/day sc) and control (saline sc) groups, and the administration was continued throughout the study. The op rats were killed 2, 4, 8, and 12 weeks and nop rats 8 weeks after the fracture. Fracture healing was examined by x-ray and bone-bending strength. Neurectomy reduced bone strength (p < 0.01) at 4 weeks. Clodronate did not affect the bending strength of healing callus of op rats at 2, 4, 8, or 12 weeks after fracture, but reduced the strength of healing callus in nop rats (p < 0.05) at 8 weeks. Radiologic callus width increased in clodronate-treated groups both in op (8 and 12 weeks, p < 0.001) and nop rats (8 weeks, p < 0.05) when compared with saline-treated groups. Clodronate did not affect normal bone strength.

In conclusion, clodronate did not affect the bending strength of op fracture nor the strength of the control bones. The remodeling of the fracture was delayed with clodronate.     

Expression of dentin matrix protein 1 (DMP1) during fracture healing

Dentin matrix protein 1 (DMP1) is one of the acidic phosphorylated extracellular matrix proteins called the SIBLING (small integrin-binding ligand, N-linked glycoproteins) family. Recent studies showed that DMP1 is expressed in the mineralized tissues and suggested that DMP1 is involved in the mineralization. We investigated the precise localization of DMP1 messenger RNA (mRNA) and protein during fracture healing. In situ hybridization demonstrated that DMP1 mRNA was strongly expressed in preosteocytes and osteocytes in the bony callus during intramembranous and endochondral ossification while DMP1 mRNA was not detected in osteoblasts and chondrocytes. During endochondral ossification, however, a low number of DMP1-expressing cells were identified in the cluster of hypertrophic chondrocytes. However, these DMP1-expressing cells were not hypertrophic and were likely to be osteoblast-lineage cells, which were embedded in the matrix of bone or cartilage, because type I collagen-expressing cells and invasion of capillary vessels were observed in the same area. Northern blot, in situ hybridization, and immunohistochemical analyses showed that DMP1 mRNA and protein expressions were increased until day 14 postfracture, when bony callus was formed, and then declined to a lower level during remodeling of the bony callus. Therefore, DMP1 is likely to play an important role in the mineralization of the bony callus.     

不同骨愈合方式的细胞与分子机理研究-BMP与骨祖细胞的分布及其作用

目的 :研究骨形态发生蛋白 (BMP)及骨祖细胞的分布与作用 ,探讨不同骨愈合方式的细胞与分子机理。方法 :制造兔桡骨中下段骨折 ,缺损 3mm ,不同时期取骨痂作HE及BMP免疫组化染色 ,显微镜下观察结果并作计算机图像分析。结果 :膜内成骨区及软骨内成骨区骨祖细胞、成骨细胞、成软骨细胞及未成熟的骨细胞BMP染色呈强阳性 ;但肥大的软骨细胞和成纤维细胞为阴性染色。计算机图像分析显示 :膜内成骨区较软骨内成骨区有较高BMP浓度及较多阳性着色细胞。结论 :骨愈合方式与局部BMP浓度及骨祖细胞的来源与分布有关。     

Clodronate increases the calcium content in fracture callus

Summary Eighty-eight rats underwent intramedullary pin fixation and fracture of both tibiae. Half of the animals were given clodronate 50 mg/kg s. c. weekly. Clodronate treatment did not affect the growth of fibrocartilage or the endochondral and membranous new bone formation. The regaining of tensile load capacity of fractured bone remained unaffected by the drug. Calluses were remodeled to lamellar bone in both groups. However, although the total area invaded by mineralized tissue in callus remained unaffected by the drug, the areas of hematopoietic bone marrow tissue within mineralized callus were observed to be markedly smaller in clodronate-treated animals than in controls. The calluses in the clodronate group were significantly heavier and contained more calcium at 2 months after fracture than those in the controls.     

Spatial and temporal distribution of CD44 and osteopontin in fracture callus

The multifunctional adhesion molecule CD44 is a major cell-surface receptor for hyaluronic acid (HUA). Recent data suggest that it may also bind the ubiquitous bone-matrix protein, osteopontin (OPN). Because OPN has been shown to be a potentially important protein in bone remodelling, we investigated the hypothesis that OPN interactions with the CD44 receptor on bone cells participate in the regulation of the healing of fractures. We examined the spatial and temporal patterns of expression of OPN and CD44 in healing fractures of rat femora by in situ hybridisation and immunohistochemistry. We also localised HUA in the fracture callus using biotinylated HUA-binding protein. OPN was expressed in remodelling areas of the hard callus and was found in osteocytes, osteoclasts and osteoprogenitor cells, but not in cuboidal osteoblasts which were otherwise shown to express osteocalcin. The OPN signal in osteocytes was not uniformly distributed, but was restricted to specific regions near sites where OPN mRNA-positive osteoclasts were attached to bone surfaces. In the remodelling callus, intense immunostaining for CD44 was detected in osteocyte lacunae, along canaliculi, and on the basolateral plasma membrane of osteoclasts, but not in the cuboidal osteoblasts. HUA staining was detected in fibrous tissues but little was observed in areas of hard callus where bone remodelling was progressing. Our findings suggest that OPN, rather than HUA, is the major ligand for CD44 on bone cells in the remodelling phase of healing of fractures. They also raise the possibility that such interactions may be involved in the communication of osteocytes with each other and with osteoclasts on bone surfaces. The interactions between CD44 and OPN may have important clinical implications in the repair of skeletal tissues.     

Bisphosphonates in the Treatment of Thalassemia-Induced Osteoporosis

The aim of our randomized, placebo-controlled study was to investigate the effects of 2 years’ daily oral administration of alendronate or intramuscular administration of clodronate every 10 days, on bone remodeling parameters and bone mineral density (BMD), safety and tolerability in a group of osteoporotic thalassemic patients. Twenty-five young patients (mean age 26.6 ± 7.1 years) with beta-thalassemia major were randomly divided to receive placebo or 100 mg of clodronate intramuscularly every 10 days or 10 mg of alendronate per os daily. All patients took 500 mg of elemental calcium and 400 IU cholecalciferol in the evening at meal time. After 2 years, pyridinium crosslinks, which are bone resorption markers, did not differ significantly from baseline values in the placebo group, whereas they had decreased significantly in the clodronate and alendronate groups. Osteocalcin, a bone formation marker, did not change significantly in the placebo group, whereas it decreased slightly, but not significantly, in the clodronate and alendronate groups after 12 and 24 months. At the end of the study, the lumbar spine BMD had decreased significantly in the placebo group; it did not change significantly in the clodronate group; in the alendronate group it had increased but not significantly, whereas the increase was significant with respect to the placebo group. Femoral neck BMD decreased significantly in the placebo group; it did not change significantly in the clodronate group, but increased significantly in the alendronate group. No relevant side effects were recorded during our study. In conclusion, in patients with thalassemia-induced osteoporosis, the daily administration of alendronate significantly increases BMD, the most important predictor of the risk of fracture at several sites. Clodronate treatment at our dosage is ineffective in this pathology in spite of the good compliance of patients. Received: 13 August 2001 / Accepted: 19 February 2002     

Dentin matrix protein 1 is predominantly expressed in chicken and rat osteocytes but not in osteoblasts.

Although osteocytes are the most abundant cells in bone, little is known about their function, and no specific marker protein for osteocytes has been described. Dentin matrix protein 1 (DMP1) is an acidic phosphoprotein expressed in tooth organ and bone. Our previous work showed that in the chicken, which is not capable of forming tooth, DMPI messenger RNA (mRNA) is highly expressed in bone by Northern blot analysis. To clarify the significance of DMP1 expression in bone, the expression of DMP1 mRNA and its protein was examined in the chicken and rat. In the chicken, DMPI mRNA was detected only in bone tissues and was localized in osteocytes and preosteocytes but not in osteoblasts. Similarly, in the rat, DMPI mRNA was predominantly expressed in osteocytes and preosteocytes in bone matrix but not in osteoblasts located at the bone surface. Antiserum was raised against the peptide from rat DMP1, and the localization of DMP1 was examined by immunohistochemistry. In the development of bone, DMP1 was first detected in newly formed bone matrix after osteoblastic cells had been embedded within it. After the appearance of typical osteocytes, DMP1 was localized in the pericellular bone matrix of osteocytes, including their processes. These data show that DMP1 is a bone matrix protein specifically expressed in osteocytes and preosteocytes and suggest that DMP1 plays a role in bone homeostasis because of its high calcium ion-binding capacity.     

Demonstration of osteocytic perilacunar/canalicular remodeling in mice during lactation

Osteoclasts are thought to be solely responsible for the removal of bone matrix. However, we show here that osteocytes can also remove bone matrix by reversibly remodeling their perilacunar/canalicular matrix during the reproductive cycle. In contrast, no osteocytic remodeling was observed with experimental unloading despite similar degrees of bone loss. Gene array analysis of osteocytes from lactating animals revealed an elevation of genes known to be utilized by osteoclasts to remove bone, including tartrate‐resistant acid phosphatase (TRAP) and cathepsin K, that returned to virgin levels upon weaning. Infusion of parathyroid hormone–related peptide (PTHrP), known to be elevated during lactation, induced TRAP activity and cathepsin K expression in osteocytes concurrent with osteocytic remodeling. Conversely, animals lacking the parathyroid hormone type 1 receptor (PTHR1) in osteocytes failed to express TRAP or cathepsin K or to remodel their osteocyte perilacunar matrix during lactation. These studies show that osteocytes remove mineralized matrix through molecular mechanisms similar to those utilized by osteoclasts. © 2012 American Society for Bone and Mineral Research.     

Matrix extracellular phosphoglycoprotein (MEPE) is highly expressed in osteocytes in human bone

The matrix extracellular phosphoglycoprotein (MEPE) gene is highly expressed in tumors that cause oncogenic hypophosphatemic osteomalacia (OHO). MEPE is also known as one of the bone-tooth matrix proteins and is associated with bone mineralization. We developed a rabbit polyclonal antibody directed against recombinant human MEPE (rhMEPE) after cloning its cDNA from the cDNA library of a nasal tumor tissue causing OHO. Using this antibody, we analyzed the distribution of MEPE in human bones by immunohistochemistry. In bone specimens from normal subjects, MEPE was predominantly expressed by osteocytes and not by osteoblasts. In bone specimens from patients with osteomalacia, however, MEPE was focally expressed by deeply located osteocytes. We also compared the MEPE positivity of osteocytes in mineralized bone and non-mineralized osteoid obtained from patients with osteomalacia and osteoporosis. Among osteomalacia patients, MEPE positivity was seen in 87.5 ± 8.6% of the osteocytes from mineralized bone compared with 7.8 ± 6.4% of those from osteoid. Among osteoporosis patients, MEPE positivity was found in 95.3 ± 0.5% of the osteocytes from mineralized bone compared with 4.9 ± 5.7% of those from osteoid. MEPE was mainly expressed by osteocytes embedded in the matrix of mineralized bone from patients with osteomalacia or osteoporosis. Our data provide the first histological evidence that MEPE is predominantly expressed by osteocytes in human bone, with significant expression by osteocytes within mineralized bone.     

Long-term administration of clodronate does not prevent fracture healing in rats

Clinicians have been concerned that fractures do not heal properly in individuals exposed to bisphosphonate treatment, a treatment that strongly affects bone metabolism. The current study attempted to clarify the long-term effects of clodronate (dichloromethylene bisphosphonate) treatment on fracture healing in growing rats. Clodronate was administered subcutaneously twice a week in a dose of 2 mg/kg or 10 mg/kg. Physiologic saline served as a control. After 24 weeks of treatment, the tibiae were fractured, and the treatment was continued for another 4 weeks and 8 weeks. At both end points the cross-sectional areas of the callus, measured by peripheral quantitative computed tomography, were greater in the clodronate-treated rats than in controls, but there were no significant differences in bone mineral density. There were no significant differences between treatments in radiologic healing, histomorphometry, or in mechanical failure load of the callus with the exception of increased tensile stiffness at a dose of 2 mg/kg at 4 weeks. Clodronate treatment does not seem to prolong the fracture healing process, even when administered on a long-term basis before the fracture. Clodronate increases the size of the callus, but has only a minor effect on its biomechanical properties. The current results suggest that long-term clodronate treatment does not inhibit fracture healing.     

Studies on the biology of fish bone. III. Ultrastructure of osteogenesis and resorption in osteocytic (cellular) and anosteocytic (acellular) bones

Summary The comparative ultrastructure of fish bone osteogenesis and resorption induced by scale removal was described in the osteocytic (cellular-boned)Carassius auratus and the anosteocytic (acellular-boned)Tilapia macrocephala. Osteocytes, present in osteocytic bone, were lacking in anosteocytic bone. In osteocytic bone the osteoblast secreted a collagenous preosseous matrix in which it became enmeshed and then was termed a preosteocyte. When the preosseous matrix mineralized, the preosteocyte was termed an osteocyte and was completely surrounded by bone. In anosteocytic bone the osteoblasts receded from the mineralizing front and never became trapped as osteocytes. During resorption, types A and B resorptive cells, present in both bone types, invaded the matrix and demineralized the osseous zone. These cells were characterized by large amounts of granular endoplasmic reticulum and intracellular inclusions containing crystal-like material. Although functionally similar to mammalian osteoclasts, these cells lacked a characteristic ruffled border and were not multinucleated. The osteocytes of cellular bone did not appear to be involved during demineralization.     

Matrix Metalloproteinase–Driven Endochondral Fracture Union Proceeds Independently of Osteoclast Activity

As new insights into the complexities of endochondral fracture repair emerge, the temporal role of osteoclast activity remains ambiguous. With numerous antiresorptive agents available to treat bone disease, understanding their impact on bone repair is vital. Further, in light of recent work suggesting osteoclast activity may not be necessary during early endochondral fracture union, we hypothesize instead a pivotal role of matrix metalloproteinase (MMP) secreting cells in driving this process. Although the role of MMPs in fracture healing has been examined, no directly comparative experiments exist. We examined a number of antiresorptive treatments to either block osteoclast activity, including the potent bisphosphonates zoledronic acid (ZA) and clodronate (CLOD), which work via differing mechanisms, or antagonize osteoclastogenesis with recombinant OPG (HuOPG‐Fc), comparing these directly to an inhibitor of MMP activity (MMI270). Endochondral ossification to union occurred normally in all antiresorptive groups. In contrast, MMP inhibition greatly impaired endochondral union, significantly delaying cartilage callus removal. MMP inhibition also produced smaller, denser hard calluses. Hard callus remodeling was, as expected, delayed with ZA, CLOD, and OPG treatment at 4 and 6 weeks, resulting in larger, more mineralized calluses at 6 weeks. As a result of reduced hard callus turnover, bone formation was reduced with antiresorptive agents at these time points. These results confirm that the achievement of endochondral fracture union occurs independently of osteoclast activity. Alternatively, MMP secretion by invading cells is obligatory to endochondral union. This study provides new insight into cellular contributions to bone repair and may abate concerns regarding antiresorptive therapies impeding initial fracture union.     

The fate of soft callus chondrocytes during long bone fracture repair.

Following fracture, the cartilaginous tissue of the soft callus is eventually replaced by bone. Removal of the cartilage is a critical part of the bone healing process but information concerning the changes in chondrocytes during this process is sparse. The aim of the study was to investigate the fate of chondrocytes in the soft callus during the bone repair process using a rabbit tibial fracture model. Fracture tissue was processed for collagen I-III and keratan sulphate immunohistochemistry to study changes in matrix composition and the TUNEL technique (terminal deoxynucleotidyl transferase medicated dUTP nick-end labelling) to identify death of soft callus chondrocytes. Transmission electron microscopy (TEM) was also carried out to investigate the ultrastructure of chondrocytes within the soft callus. Results showed that the size of the cartilage area decreased over time and that cartilage matrix was replaced with new matrix rich in collagen I and III. Chondrocytes became engulfed in the new matrix and appeared to stop producing cartilage matrix. Chondrocyte cell death was seen at the border of the soft callus, just within the newly produced matrix. TEM revealed that these dying/dead cells were not typically apoptotic in appearance. In conclusion, results indicate that chondrocytes of the soft callus die as a result of the progressive production of bone matrix which eventually engulfs them and leads to the remodelling of the area and eventual bone repair.     

Osteocyte density in woven bone

Woven bone forms rapidly during tissue growth, following injury and in response to certain anabolic stimuli. Functional differences between woven and lamellar bone may be due, in part, to differences in osteocyte density (cells per unit tissue). Woven bone has been estimated to contain four to eight times more osteocytes than lamellar bone, although primary data to support this assertion are limited. Given recent findings implicating osteocytes as regulators of bone remodeling, bone formation and bone volume, such large differences in osteocyte density between woven and lamellar bone may have important consequences. In this study, we compared the density of osteocyte lacunae (lacunae/mm(2) tissue) in rat lamellar bone with that in woven bone formed under several different circumstances. We found that the lacunar density of lamellar cortical bone in the rat (834+/-83 cells/mm2, mean+/-SD) did not differ significantly from that of periosteal woven bone formed via intramembranous osteogenesis, either in response to mechanical loading (921+/-204 cells/mm2) or in the periosteal buttressing region of the fracture callus (1138+/-168 cells/mm2). In contrast, lacunar density of endochondrally derived woven bone in the center (gap) region of fracture callus was nearly 100% greater (1875+/-270 cells/mm2) than in lamellar cortical bone while lacunar density of primary spongiosa of the growth plate was 40% greater (1674+/-228 cells/mm2) than that in lamellar cancellous bone (1189+/-164). These findings demonstrate that lacunar density in woven bone varies depending on skeletal site and developmental history and appears to be elevated in endochondrally derived woven bone adjacent to marrow space. Given the considerable evidence supporting osteocytes as local initiators of bone remodeling, we suggest that woven bone with increased lacunar density may undergo remodeling at an accelerated rate.     

Effects of Long-Term Administration of Clodronate on Growing Rat Bone

Bisphosphonates inhibit bone resorption. Short-term bisphosphonate treatment at therapeutical dosage has been shown to be safe, but there are only a few studies concerning the long-term effects of bisphosphonates on the non-osteoporotic skeleton. Here, we studied the bone effects of 32 weeks' treatment with clodronate on growing rats, using a therapeutical dose of 2 mg/kg and a high dose of 10 mg/kg. We used biomechanical, densitometrical, and, histomorphometrical analyses to examine the rat tibia, femur, and vertebra and also tested some hematological and biochemical parameters. Tibial length was significantly lower in the high clodronate group compared with the controls. No differences were found in tibial or vertebral ash weights. The L4 vertebra compression failure load was higher in the high clodronate group compared with the therapeutical clodronate group, but not compared with the controls. The mechanical strength of the femoral shaft or femoral neck was not affected by clodronate. Cortical BMD in the L4 vertebra was significantly higher in both clodronate groups compared with controls. Histomorphometrical analysis indicated that the trabecular number of vertebra was increased in the therapeutical clodronate group. The mineral apposition rate was not significantly affected by the treatment. Hematological analyses showed a decreased number of platelets at the high dosage. A slight increase in liver enzyme activity was seen in both groups. We conclude that long-term administration of clodronate has no harmful but rather some beneficial effects on bone at the therapeutical dosage. However, a fivefold dose of clodronate causes a slight decrease in the growth of tibial length.     

Cell Death of Osteocytes Occurs in Rat Alveolar Bone during Experimental Tooth Movement

The purpose of this study was to examine the morphological changes in alveolar bone osteocytes on the pressure side during experimental tooth movement, using quantitative evaluation on hematoxylin and eosin-stained sections, the TUNEL method, confocal laser scanning microscopy (CLSM), and transmission electron microscopy. In 8-week-old Wistar rats, the left first molar was forced to move mesially with an average load of 10 g by a nickel-titanium superelastic wire. After 6 hours, nuclear condensation and fragmentation appeared in osteocytes adjacent to the hyalinized periodontal ligament (PDL). These cells showed TUNEL-positive reaction. The number of osteocytes with apoptosis progressively increased up to 1 day. At 1 and 2 days, cytoplasmic and nuclear destruction and distribution within the lacunae occurred and increased up to 4 days. The proportion of necrotic osteocytes and near empty lacunae peaked at 2 and 4 days, respectively. At 7 days, necrotic osteocyte and empty lacunae numbers returned to the level of control bone, probably due to resorption of the alveolar bone containing apoptotic and necrotic osteocytes. Ultrastructually, the osteocytes showed apoptotic morphology at 6 and 12 hours and 1 day; at 2 and 4 days, several osteocytes exhibited characteristics of necrosis and destructive images of the surrounding bone matrix, which resulted in enlargement of the lacunae. The present results demonstrate that osteocytes in alveolar bone adjacent to the hyalinized PDL underwent cell death via apoptosis and "secondary necrosis" during orthodontic tooth movement, which may be associated with the subsequent bone resorption.     

Suppression of autophagy in osteocytes does not modify the adverse effects of glucocorticoids on cortical bone

Glucocorticoid excess decreases bone mass and strength in part by acting directly on osteoblasts and osteocytes, but the mechanisms remain unclear. Macroautophagy (herein referred to as autophagy) is a lysosome-based recycling pathway that promotes the turnover of intracellular components and can promote cell function and survival under stressful conditions. Recent studies have shown that glucocorticoids stimulate autophagy in osteocytes, suggesting that autophagy may oppose the negative actions of glucocorticoids on this cell type. To address this possibility, we compared the impact of prednisolone administration on the skeletons of adult mice in which autophagy was suppressed in osteocytes, via deletion of Atg7 with a Dmp1-Cre transgene, to their control littermates. In control mice, prednisolone increased autophagic flux in osteocyte-enriched bone as measured by LC3 conversion, but this change did not occur in the mice lacking Atg7 in osteocytes. Nonetheless, prednisolone reduced femoral cortical thickness, increased cortical porosity, and reduced bone strength to similar extents in mice with and without autophagy in osteocytes. Prednisolone also suppressed osteoblast number and bone formation in the cancellous bone of control mice. As shown previously, Atg7 deletion in osteocytes reduced osteoblast number and bone formation in cancellous bone, but these parameters were not further reduced by prednisolone administration. In cortical bone, prednisolone elevated osteoclast number to a similar extent in both genotypes. Taken together, these results demonstrate that although glucocorticoids stimulate autophagy in osteocytes, suppression of autophagy in this cell type does not worsen the negative impact of glucocorticoids on the skeleton.