Immunohistochemical study of osteopontin expression during distraction osteogenesis in the rat

Effect of platelet rich plasma injection on bone formation in the expanded mid-palatal suture in rabbits: a randomized controlled animal study

BACKGROUND

Mid-Palatal suture expansion needs long retention period due to delayed bone formation in the expanded suture. Platelet-rich plasma (PRP) is a concentrated source of growth factors which increase bone formation. The aim of this study was to evaluate the effect of PRP injection on bone formation in expanded mid palatal suture in rabbits.

METHODS

In this prospective randomized controlled animal study, Twenty male rabbits (8-weeks-old) were subjected to mid-palatal expansion for 5 days. Animals were afterwards randomly divided into control group A & study group B. PRP was prepared and injected in the mid-palatal suture in animals belonging to group B only. After 6 weeks of retention, all animals were euthanized, and premaxillae were prepared for histological, histomorphometric and immunohistochemical analysis. Student t-test and paired t-test were used to compare the means of the two groups and within the same group respectively. Significance level set at p ≤ 0.05.

RESULTS

Histomorphometric analysis revealed a significant increase (p < 0.001) in the mean percentage of new bone in the study group (14.4%) compared to the control (1.4%). Suture width in study group was significantly wider than the control group (278.8 ± 9μms and 120.4 ± 3.4μms, p < 0.001). There was a significant increase in vascular density in study group than control group (309 ± 65.34 and 243.86 ± 48.1, p = 0.021). Osteopontin immuno-expression revealed a significant increase in optical density in study group than control group (0.21 ± 0.02 & 0.12 ± 0.01, p < 0.001).

CONCLUSIONS

In rabbit model, PRP injection can accelerate new bone formation in the expanded mid-palatal suture when compared to the control. This could hopefully result in a more stable midpalatal expansion and a reduced retention period.

Bulked Segregant Analysis and Association Analysis Identified the Polymorphisms Related to the Intermuscular Bones in Common Carp (Cyprinus carpio)

Simple Summary

Many widely cultured freshwater fish species, such as common carp, belong to the Cyprinidae family. However, most cyprinids have numerous and complex intermuscular bones (IBs), resulting in an adverse effect on cyprinid fish meat processing and consumption. Numerous studies have been trying to understand the development mechanism of IBs and to identify the SNPs associated with the total IB number. However, the SNPs associated with different forms of IBs have been studied less thoroughly. The joint effects of the SNPs on IB development also remain poorly understood. The common carp has numerous geographical populations and domesticated strains, diversifying its phenotypes. The question of whether consensus IB-related SNPs or genes exist among multiple strains of common carp has also not yet been answered. Selective breeding of IB-reduced common carp has been hindered due to a lack of effective molecular markers. To answer these questions, we performed bulked segregant analysis (BSA) to detect the consensus SNPs in three strains. The consensus BSA-SNPs and the other SNPs in their flanking regions were validated in additional individuals. The SNPs associated with the frequency of different IB types were identified. We examined the joint effects of significant SNPs on the numbers of different types of IBs. The identified genetic markers may benefit future selective breeding and reduce the IB number in common carp.

Abstract

The allotetraploid common carp is one of the most important freshwater food fish. However, the IBs found in allotetraploid common carp increase the difficulty in fish meat processing and consumption. Although candidate genes associated with the total IB number have been identified, the SNPs associated with the numbers of the total IBs and different forms of IBs have not yet been identified, hindering the breeding of IB-reduced common carp. Herein, the numbers of different types of IBs in three common carp strains were measured. Using whole-genome resequencing and bulked segregant analysis in three pairs of IB-more and IB-less groups, we identified the consensus nonsynonymous SNPs in three strains of common carp. Screening the flanking regions of these SNPs led to the detection of other SNPs. Association study detected 21 SNPs significantly associated with the number of total IBs, epineural-IBs, and ten detailed types of IBs. We observed the joint effects of multiple SNPs on each associated IB number with an improved explained percentage of phenotypic variation. The resulting dataset provides a resource to understand the molecular mechanisms of IB development in different common carp strains. These SNPs are potential markers for future selection to generate IB-reduced common carp.

Molecular mechanisms of intermuscular bone development in fish: a review

Intermuscular bones (IBs) are slender linear bones embedded in muscle, which ossify from tendons through a process of intramembranous ossification, and only exist in basal teleosts. IBs are essential for fish swimming, but they present a choking risk during human consumption, especially in children, which can lead to commercial risks that have a negative impact on the aquaculture of these fish. In this review, we discuss the morphogenesis and functions of IBs, including their underlying molecular mechanisms, as well as the advantages and disadvantages of different methods for IB studies and techniques for breeding and generating IB-free fish lines. This review reveals that the many key genes involved in tendon development, osteoblast differentiation, and bone formation, e.g., scxa, msxC, sost, twist, bmps, and osterix, also play roles in IB development. Thus, this paper provides useful information for the breeding of new fish strains without IBs via genome editing and artificial selection.

Boosting osteogenic potential and bone regeneration by co-cultured cell derived extracellular matrix incorporated porous electrospun scaffold

Implants for bone regeneration to remedy segmental bone defects, osteomyelitis, necrotic bone tissue and non-union fractures have worldwide appeal. Although biomaterials offer most of the advantages by improving tissue growth but developments are more commonly achieved via biologically derived molecules. To aid site specific bone tissue regeneration by synthetic scaffold, cell derived extracellular matrix (ECM) can be a crucial component. In this study, co-cultured bone marrow mesenchymal stem cell and osteoblastic cells derived ECM incorporated electrospun polycaprolactone (PCL) membranes were assessed for bone tissue engineering application. The preliminary experimental details indicated that, co-culture of cells supported enhanced in vitro ECM synthesis followed by successful deposition of osteoblastic ECM into electrospun membranes. The acellular samples revealed retention of ECM related biomacromolecules (collagen, glycosaminoglycan) and partial recovery of pores after decellularization. In vitro biocompatibility tests ensured improvement of proliferation and osteoblastic differentiation of MC3T3-E1 cells in decellularized ECM containing membrane (PCL-ECM) compared to bare membrane (PCL-B) which was further confirmed by osteogenic marker proteins expression analysis. The decellularized PCL-ECM membrane allowed great improvement of bone regeneration over the bare membrane (PCL-B) in 8 mm size critical sized rat skull defects at 2 months of post implantation. In short, the outcome of this study could be impactful in development and application of cell derived ECM based synthetic electrospun templates for bone tissue engineering application.[Formula: see text].

Comparative proteomic analysis of human mesenchymal stromal cell behavior on calcium phosphate ceramics with different osteoinductive potential

In recent years, synthetic calcium phosphate (CaP) ceramics have emerged as an alternative to bone grafts in the treatment of large critical-sized bone defects. To successfully substitute for bone grafts, materials must be osteoinductive, that is, they must induce osteogenic differentiation and subsequent bone formation in vivo. Although a set of osteoinductive CaP ceramics has been developed, the precise biological mechanism by which a material directs cells toward osteogenesis and the role of individual chemical and physical properties in this mechanism remain incompletely understood. Here, we used proteomics to compare serum protein adsorption to two CaP ceramics with different osteoinductive potential, namely an osteoinductive β-tricalcium phosphate (TCP) and a non-osteoinductive hydroxyapatite (HA). Moreover, we analyzed the protein profiles of human mesenchymal stromal cells (hMSCs) cultured on these two ceramics. The serum protein adsorption experiments in the absence of cells highlighted the proteins that are highly abundant in the serum and/or have a high affinity to CaP. The extent of adsorption was suggested to be affected by the available surface area for binding and by the ion exchange dynamics on the surface. Several proteins were uniquely expressed by hMSCs on TCP and HA surfaces. Proteins identified as enriched on TCP were involved in processes related to wound healing, cell proliferation, and the production of extracellular matrix. On the other hand, proteins that were enriched on HA were involved in processes related to protein production, translation, localization, and secretion. In addition, we performed a separate proteomics analysis on TCP, HA, and two biphasic calcium phosphates with known osteoinductive potential and performed a clustering analysis on a combination of a set of proteins found to be enriched on osteoinductive materials with a set of proteins already known to be involved in osteogenesis. This yielded two protein networks potentially involved in the process of osteoinduction – one consisting of collagen fragments and collagen-related enzymes and a second consisting of endopeptidase inhibitors and regulatory proteins. The results of this study show that protein profiling can be a useful tool to help understand the effect of biomaterial properties on the interactions between a biomaterial and a biological system. Such understanding will contribute to the design and development of improved biomaterials for (bone) regenerative therapies.

Relevant advances in bone lengthening research: a bibliometric analysis of the 100 most-cited articles published from 2001 to 2017

This study aimed to assess the scientific production of bone lengthening research by identifying the most-cited papers. All articles including the term 'bone lengthening' published between 2001 and 2017 were retrieved through the Web of Science database. The 100 most-cited articles on bone lengthening included a total of 4244 citations, with 414 (9.7%) citations in 2017. There was an average of 249.6 citations per year. The articles predominantly addressed biomechanics and bone formation (38). Different surgical techniques, including intramedullary nail (14), Ilizarov (nine), intramedullary skeletal kinetic distractor (ISKD) (six), Taylor spatial frame (6), the PRECICE device (three), and lengthening and submuscular locking plate (three), were the second most-studied topic. Most studies were therapeutic (58), whereas 30 studies were experimental investigations using animal models. Among the clinical studies, case series were predominant (level of evidence IV) (57). This study presents the first bibliometric analysis of the most relevant articles on bone lengthening. The list is relatively comprehensive in terms of identifying the top issues in this field. However, the most influential clinical studies have a poor level of evidence, although a slight tendency toward a better level of evidence has been observed in more recent years.

Is there an optimal initial amount of activation for midpalatal suture expansion? : A histomorphometric and immunohistochemical study in a rabbit model

OBJECTIVE

Accelerated bone-borne expansion protocols on sutural separation and sutural bone formation were evaluated via histomorphometry and immunohistochemistry to determine the optimal initial activation without disruption of bone formation.

MATERIALS AND METHODS

Sixteen New Zealand white rabbits were randomly divided into four groups. Modified Hyrax expanders were placed across the midsagittal sutures and secured with miniscrew implants with the following activations: group 1 (control), 0.5 mm expansion/day for 12 days; group 2, 1 mm instant expansion followed by 0.5 mm expansion/day for 10 days; group 3, 2.5 mm instant expansion followed by 0.5 mm expansion/day for 7 days; and group 4, 4 mm instant expansion followed by 0.5 mm expansion/day for 4 days. After 6 weeks, sutural expansion and new bone formation were evaluated histomorphometrically. Statistical analysis was performed using Kruskal-Wallis/Mann-Whitney U tests and Spearman's rho correlation (p < 0.05).

RESULTS

The smallest median sutural separation was observed in group 1 (3.05 mm) and the greatest in group 4 (4.57 mm). The lowest and highest amount of bone formation were observed in group 4 (55.82%) and in group 3 (66.93%), respectively. Immunohistochemical analysis revealed significant differences in median levels of alkaline phosphatase and osteopontin expression between all experimental groups. The highest level of these proteins was attained in group 3, followed by groups 2, 1, and 4, respectively.

CONCLUSIONS

Sutural appositional bone formation corresponded with the amount of initial expansion to a point. When initial expansion was increased to 4 mm, sutural bone remodeling was disturbed and new bone formation was decreased. The most effective sutural expansion was achieved with 2.5 mm initial activation followed by 0.5 mm expansion/day for 7 days.

Colorectal carcinoma with osseous metaplasia

Osseous metaplasia (OM) is rarely observed in colorectal cancer (incidence < 0.4% in rectal cancer), where it has a non-specific clinical presentation and unknown pathogenesis. Here, we report three cases of colorectal carcinoma with OM and propose a new hypothesis. All three patients (two males and one female) were Chinese and had different sites of colorectal carcinoma with OM: rectum, sigmoid colon, and appendix. The pathologic diagnoses were serrated adenocarcinoma; moderately to poorly differentiated adenocarcinoma with micropapillary carcinoma and cribriform comedo-type adenocarcinoma; and mucinous adenocarcinoma, respectively. Clinical follow-up showed that one patient died 5 months after surgery, but the others are alive after 68 months and 53 months. Immunohistochemistry revealed that CD44, MAPK, MDM2, OPN and PEDF were expressed by both tumor cells and stromal cells, while P53 was expressed only by tumor cells. KRAS/NRAS/BRAF genotyping revealed different KRAS mutations in each of the three cases, but the NRAS and BRAF exons were all wild-type. These findings suggest OM has no relation with NRAS and BRAF mutation, and it is uncertain whether there is a relationship between ossification and KRAS mutation. OPN, MAPK, MDM2, P53, PEDF and CD44 may act as osteogenic factors in colorectal cancer with OM.

Enhanced bone regeneration with carbon nanotube reinforced hydroxyapatite in animal model

In order to improve the inherently poor mechanical properties of hydroxyapatite (HAp) and to increase its feasibility as load bearing implant material, in the present investigation, functionalised (HFC1 and HFC2) and non-functionalized (HC1 and HC2) multi-walled carbon nanotubes were used as reinforcing material with HAp. Significant improvement with respect to fracture toughness, flexural strength and impact strength of the composites was noticed. In vitro biological properties of HAp-carbon nanotube (CNT) biocomposites have also favored uniform and systematic apatite growth on their surface. Subsequently, in vivo osseous ingrowth at bone defect of rabbit femur was evaluated and compared using radiology, push out test, fluorochrome labeling, histology and scanning electron microscopy after 2 and 4 months respectively. The results demonstrated growth of web like soft callus from the host bone towards the implant, ensuring strong host bone interaction. Toxicological studies of the liver and kidney cells exhibited no abnormality, thereby confirming non-toxicity of the CNT in the animal body. Host-implant biomechanical strength showed high interfacial strength of the composites, indicating their high potentials to be used for bone remodeling applications.

A combinatorial cell-laden gel microarray for inducing osteogenic differentiation of human mesenchymal stem cells

Development of three dimensional (3D) microenvironments that direct stem cell differentiation into functional cell types remains a major challenge in the field of regenerative medicine. Here, we describe a new platform to address this challenge by utilizing a robotic microarray spotter for testing stem cell fates inside various miniaturized cell-laden gels in a systematic manner. To demonstrate the feasibility of our platform, we evaluated the osteogenic differentiation of human mesenchymal stem cells (hMSCs) within combinatorial 3D niches. We were able to identify specific combinations, that enhanced the expression of osteogenic markers. Notably, these 'hit' combinations directed hMSCs to form mineralized tissue when conditions were translated to 3D macroscale hydrogels, indicating that the miniaturization of the experimental system did not alter stem cell fate. Overall, our findings confirmed that the 3D cell-laden gel microarray can be used for screening of different conditions in a rapid, cost-effective, and multiplexed manner for a broad range of tissue engineering applications.

Autologous rabbit adipose tissue-derived mesenchymal stromal cells for the treatment of bone injuries with distraction osteogenesis

BACKGROUND AIMS

Adipose tissue-derived mesenchymal stromal cells (MSCs) have a higher capacity for proliferation and differentiation compared with other cell lineages. Although distraction osteogenesis is the most important therapy for treating bone defects, this treatment is restricted in many situations. The aim of this study was to examine the therapeutic potential of adipose tissue-derived MSCs and osteoblasts differentiated from adipose tissue-derived MSCs in the treatment of bone defects.

METHODS

Bone defects were produced in the tibias of New Zealand rabbits that had previously undergone adipose tissue extraction. Tibial osteotomy was performed, and a distractor was placed on the right leg of the rabbits. The rabbits were placed in control (group I), stem cell (group II) and osteoblast-differentiated stem cell (group III) treatment groups. The rabbits were sacrificed, and the defect area was evaluated by radiologic, biomechanical and histopathologic tests to examine the therapeutic effects of adipose tissue-derived MSCs.

RESULTS

Radiologic analyses revealed that callus density and the ossification rate increased in group III compared with group I and group II. In biomechanical tests, the highest ossification rate was observed in group III. Histopathologic studies showed that the quality of newly formed bone and the number of cells active in bone formation were significantly higher in group III rabbits compared with group I and group II rabbits.

CONCLUSIONS

These data reveal that osteoblasts differentiated from adipose tissue-derived MSCs shorten the consolidation period of distraction osteogenesis. Stem cells could be used as an effective treatment for bone defects.

Rosiglitazone disrupts endosteal bone formation during distraction osteogenesis by local adipocytic infiltration

Rosiglitazone (Rosi) is a drug in the thiazolidinedione class for treatment of type 2 diabetes mellitus (T2DM), which binds and activates PPARγ nuclear receptor in fat cells, sensitizing them to insulin. Despite proven antidiabetic efficacy, Rosi therapy may be associated with trabecular bone loss and an increased risk of fractures. To examine the potential side effects of Rosi treatment on bone formation, we delivered Rosi to mice using a combined model of distraction osteogenesis (DO) and type 2 diabetes mellitus (T2DM). DO provides a unique method to isolate the sequence of intramembranous bone formation, an important component of both fracture healing and bone homeostasis. Four groups of n=6 mice were used to compare the effects of Rosi on bone formation and cellular composition in both diabetic (Avy/a strain) and non-diabetic mice (a/a strain). New bone formation was examined by high resolution radiographs, micro-computed tomography, and histology. Precursor cells in the distraction gap were quantitated using immunohistochemical stains for proliferating cell nuclear antigen. Committed osteoblasts and adipocytes in the gap were identified and quantitated by immunostaining for osteocalcin and FABP4/aP2, respectively. The diabetic model developed obesity, hyperglycemia, hyperinsulinemia and insulin resistance, while the control littermates remained lean, normoglycemic and insulin sensitive. Rosi treatment decreased levels of non-fasted glucose and insulin and improved insulin sensitivity in the A(vy)/a mice, but had no effect in a/a mice, indicating antidiabetic efficacy of Rosi at the tested dose. Despite the diabetic, obese mice having twice the number of fat cells in their marrow than the non-diabetic mice, bone formation using DO was not adversely affected by the diabetes itself. However, Rosi treatment significantly diminished intramembranous endosteal bone formation, while increasing adipogenesis in and adjacent to the distraction gap up to 3.5- to 3.8-fold in both diabetic and non-diabetic models. This effect was independent of the anti-diabetic therapeutic response. These results raise the question of whether osteoblast precursors are inhibited in their development or actually converted to adipocytic phenotypes, possibly via marrow fat PPARγ nuclear receptor.

Rosiglitazone inhibits bone regeneration and causes significant accumulation of fat at sites of new bone formation

Thiazolidinediones (TZDs), peroxisome proliferator-activated receptor gamma activators, and insulin sensitizers represent drugs used to treat hyperglycemia in diabetic patients. Type 2 diabetes mellitus (T2DM) is associated with a twofold increase in fracture risk, and TZDs use increases this risk by an additional twofold. In this study, we analyzed the effect of systemic administration of the TZD rosiglitazone on new bone formation in two in vivo models of bone repair, a model of drilled bone defect regeneration (BDR) and distraction osteogenesis (DO) and a model of extended bone formation. Rosiglitazone significantly inhibited new endosteal bone formation in both models. This effect was correlated with a significant accumulation of fat cells, specifically at sites of bone regeneration. The diminished bone regeneration in the DO model in rosiglitazone-treated animals was associated with a significant decrease in cell proliferation measured by the number of cells expressing proliferating cell nuclear antigen and neovascularization measured by both the number of vascular sinusoids and the number of cells producing proangiogenic vascular endothelial growth factor at the DO site. In summary, rosiglitazone decreased new bone formation in both BDR and DO models of bone repair by mechanisms which include both intrinsic changes in mesenchymal stem cell proliferation and differentiation and changes in the local environment supporting angiogenesis and new bone formation. These studies suggest that bone regeneration may be significantly compromised in T2DM patients on TZD therapy.

A new piezoelectric actuator induces bone formation in vivo: a preliminary study

This in vivo study presents the preliminary results of the use of a novel piezoelectric actuator for orthopedic application. The innovative use of the converse piezoelectric effect to mechanically stimulate bone was achieved with polyvinylidene fluoride actuators implanted in osteotomy cuts in sheep femur and tibia. The biological response around the osteotomies was assessed through histology and histomorphometry in nondecalcified sections and histochemistry and immunohistochemistry in decalcified sections, namely, through Masson's trichrome, and labeling of osteopontin, proliferating cell nuclear antigen, and tartrate-resistant acid phosphatase. After one-month implantation, total bone area and new bone area were significantly higher around actuators when compared to static controls. Bone deposition rate was also significantly higher in the mechanically stimulated areas. In these areas, osteopontin increased expression was observed. The present in vivo study suggests that piezoelectric materials and the converse piezoelectric effect may be used to effectively stimulate bone growth.

Understanding in vivo response and mechanical property variation in MgO, SrO and SiO₂ doped β-TCP

The aim of this work is to evaluate the influence of MgO, SrO and SiO₂ doping on mechanical and biological properties of β-tricalcium phosphate (β-TCP) to achieve controlled resorption kinetics of β-TCP system for maxillofacial and spinal fusion application. We prepared dense TCP compacts of four different compositions, i) pure β-TCP, ii) β-TCP with 1.0wt.% MgO+1.0wt.% SrO, iii) β-TCP with 1.0wt.% SrO+0.5wt.% SiO₂, and iv) β-TCP with 1.0wt.% MgO+1.0wt.% SrO+0.5wt.% SiO₂, by uniaxial pressing and sintering at 1250°C. β phase stability is observed at 1250°C sintering temperature due to MgO doping in β-TCP. In vitro mineralization in simulated body fluid (SBF) for 16 weeks shows excellent apatite growth on undoped and doped samples. Strength degradation of TCP samples in SBF is significantly influenced by both dopant chemistry and amount of dopant. Compressive strengths for all samples show degradation in SBF over the 16 week time period with varying degradation kinetics. MgO/SrO/SiO₂ doped sample shows no strength loss, while undoped TCP shows the maximum strength loss from 419 ± 28 MPa to 158 ± 28 MPa over the 16 week study. In case of MgO/SrO doped TCP, strength loss is slow and gradual. TCP doped with 1.0wt.% MgO and 1.0wt.% SrO shows excellent in vivo biocompatibility when tested in male Sprague-Dawley rats for 16 weeks. Histomorphology analysis reveals that MgO/SrO doped TCP promoted osteogenesis by excellent early stage bone remodeling as compared to undoped TCP.

Long-term outcome of cryopreserved bone-derived osteoblasts for bone regeneration in vivo

Cryopreserved bone-derived osteoblasts (CBOs) have been considered as a promising cell source for bone regeneration. Previous studies have demonstrated that CBOs had good proliferation and osteogenicity. However, the long-term outcome of CBOs in vivo still remains unknown. In this experiment, we applied CBOs combined with calcium phosphate cement (CPC) to augment maxillary sinus in canine, computer tomography, polychrome labeling, biomechanical tests, fluorescent immunohistochemistry staining and histological analysis were used to analyze the property and mineralization process of the tissue-engineered bone preclinical application. Our results showed that CBOs combined with CPC could promote bone regeneration, dramatically maintain the height, volume and biomechanical property of augmented maxillary sinus. Furthermore, the tissue-engineered bone was more mature than scaffold alone or autogenous bone, and bone formation and remodeling were still apparent 20 months postoperatively. Additionally, 4 months after surgery might be the suitable time point for implants placement in the regenerated bone. These results also indicate that cryopreserved bone may be a potential source of osteoblasts for maxillary sinus augmentation.

Unfocused extracorporeal shock waves induce anabolic effects in rat bone

BACKGROUND

Extracorporeal shock waves are known to stimulate the differentiation of mesenchymal stem cells toward osteoprogenitors and induce the expression of osteogenic-related growth hormones. The aim of this study was to investigate if and how extracorporeal shock waves affected new bone formation, bone microarchitecture, and the mechanical properties of bone in a healthy rat model, in order to evaluate whether extracorporeal shock wave therapy might be a potential treatment for osteoporosis.

METHODS

Thirteen rats received 1000 electrohydraulically generated unfocused extracorporeal shock waves to the right tibia. The contralateral, left tibia was not treated and served as a control. At two, seven, twenty-one, and forty-nine days after administration of the shock waves, in vivo single-photon-emission computed tomography (SPECT) scanning was performed to measure new bone formation on the basis of uptake of technetium-labeled methylene diphosphonate ((99m)Tc-MDP) (n = 6). Prior to and forty-nine days after the extracorporeal shock wave therapy, micro-computed tomography (micro-CT) scans were made to examine the architectural bone changes. In addition, mechanical testing, microcrack, and histological analyses were performed.

RESULTS

Extracorporeal shock waves induced a strong increase in (99m)Tc-MDP uptake in the treated tibia compared with the uptake in the untreated, control tibia. Micro-CT analysis showed that extracorporeal shock waves stimulated increases in both trabecular and cortical volume, which resulted in higher bone stiffness compared with that of the control tibiae. Histological analysis showed intramedullary soft-tissue damage and de novo bone with active osteoblasts and osteoid in the bone marrow of the legs treated with extracorporeal shock waves. Microcrack analysis showed no differences between the treated and control legs.

CONCLUSIONS

This study shows that a single treatment with extracorporeal shock waves induces anabolic effects in both cancellous and cortical bone, leading to improved biomechanical properties. Furthermore, treatment with extracorporeal shock waves results in transient damage to the bone marrow, which might be related to the anabolic effects. After further examination and optimization, unfocused extracorporeal shock waves might enable local treatment of skeletal sites susceptible to fracture.

Direct bone formation during distraction osteogenesis does not require TNFalpha receptors and elevated serum TNFalpha fails to inhibit bone formation in TNFR1 deficient mice

Distraction osteogenesis (DO) is a process which induces direct new bone formation as a result of mechanical distraction. Tumor necrosis factor-alpha (TNF) is a cytokine that can modulate osteoblastogenesis. The direct effects of TNF on direct bone formation in rodents are hypothetically mediated through TNF receptor 1 and/or 2 (TNFR1/2) signaling. We utilized a unique model of mouse DO to assess the effects of 1) TNFR homozygous null gene alterations on direct bone formation and 2) rmTNF on wild type (WT), TNFR1(-/-) (R1KO), and TNR2(-/-) (R2KO) mice. Radiological and histological analyses of direct bone formation in the distraction gaps demonstrated no significant differences between the WT, R1KO, R2KO, or TNFR1(-/-) and R2(-/-) (R1 and 2KO) mice. R1 and 2KO mice had elevated levels of serum TNF but demonstrated no inhibition of new bone formation. Systemic administration by osmotic pump of rmTNF during DO (10 microg/kg/day) resulted in significant inhibition of gap bone formation measures in WT and R2KO mice, but not in R1KO mice. We conclude that exogenous rmTNF and/or endogenous TNF act to inhibit new bone formation during DO by signaling primarily through TNFR1.

Restoration of regenerative osteoblastogenesis in aged mice: modulation of TNF

Skeletal changes accompanying aging are associated with both increased risk of fractures and impaired fracture healing, which, in turn, is due to compromised bone regeneration potential. These changes are associated with increased serum levels of selected proinflammatory cytokines, e.g., tumor necrosis factor alpha (TNF-alpha). We have used a unique model of bone regeneration to demonstrate (1) that aged-related deficits in direct bone formation can be restored to young mice by treatment with TNF blockers and (2) that the cyclin-dependent kinase inhibitor p21 is a candidate for mediation of the osteoinhibitory effects of TNF. It has been hypothesized recently that TNF antagonists may represent novel anabolic agents, and we believe that the data presented here represent a successful test of this hypothesis.

Pulmonary adenocarcinoma with heterotopic ossification

Pulmonary adenocarcinoma is a common malignancy that often involves calcification; however, bone formation in primary lung adenocarcinoma is extremely rare. In ten cases of primary pulmonary adenocarcinoma with heterotopic ossification, we detected immunoreactivity against TGF-beta1, osteopontin, osteocalcin and Runx2 in the fibroblastic stroma and tumor cells within the area of ossification. Our results suggest that in primary pulmonary adenocarcinoma, heterotopic ossification occurs via intramembranous bone formation. To our knowledge, only 11 other cases of pulmonary adenocarcinoma with heterotopic ossification have been reported. Here, we present ten cases of pulmonary adenocarcinoma showing heterotopic ossification with a description of previously published results and the histogenesis of heterotopic bone formation.

Sodium hyaluronate accelerates the healing process in tooth sockets of rats

OBJECTIVE

In this study we evaluated the effects of sodium hyaluronate (HY) in the healing process of tooth sockets of rats.

DESIGN

Immediately after the extraction of the upper first molars of male Holtzman rats, right sockets were treated with 1% HY gel (approximately 0.1 ml), while left sockets were used as control (blood clot). The animals were sacrificed at 2, 7, and 21 days after tooth extraction and upper maxillaries processed for histological and morphometric analysis of the apical and medium thirds of the sockets. Carbopol, an inert gel, was used to evaluate the mechanical effect of gel injection into sockets. Expression of bone morphogenetic protein-2 (BMP-2) and osteopontin (OPN) was determined by immunohistochemistry at 1, 2, 3, 4, 5, and 7 days after tooth extraction.

RESULTS

Histological analysis showed that HY treatment induced earlier trabecular bone deposition resulting in a bone matrix more organized at 7 and 21 days after tooth extraction. Also, HY elicited significant increase in the amount of bone trabeculaes at 7 and 21 days after tooth extraction (percentage of trabecular bone area at 7 days: 13.21+/-4.66% vs. 2.58+/-1.36% in the apical third of control sockets) and in the vessels counting at 7 days. Conversely, the number of cell nuclei was decreased in HY-treated sockets. Additionally, expression of BMP-2 and OPN was enhanced in HY-treated sockets compared with control sockets.

CONCLUSIONS

These findings suggest that HY accelerates the healing process in tooth sockets of rats stimulating the expression of osteogenic proteins.

Runt-related transcription factor 2 (RUNX2) and RUNX2-related osteogenic genes are down-regulated throughout osteogenesis in type 1 diabetes mellitus

Type 1 diabetes mellitus is associated with a number of disorders of skeletal health, conditions that rely, in part, on dynamic bone formation. A mouse model of distraction osteogenesis was used to study the consequences of streptozotocin-induced diabetes and insulin treatment on bone formation and osteoblastogenesis. In diabetic mice compared with control mice, new bone formation was decreased, and adipogenesis was increased in and around, respectively, the distraction gaps. Although insulin treatment restored bone formation to levels observed in nondiabetic control mice, it failed to significantly decrease adipogenesis. Molecular events altered during de novo bone formation in untreated type 1 diabetes mellitus, yet restored with insulin treatment were examined so as to clarify specific osteogenic genes that may contribute to diabetic bone disease. RNA from distraction gaps was analyzed by gene microarray and quantitative RT-PCR for osteogenic genes of interest. Runt-related transcription factor 2 (RUNX2), and several RUNX2 target genes, including matrix metalloproteinase-9, Akp2, integrin binding sialoprotein, Dmp1, Col1a2, Phex, Vdr, osteocalcin, and osterix, were all significantly down-regulated in the insulin-deficient, hyperglycemic diabetic animals; however, insulin treatment of diabetic animals significantly restored their expression. Expression of bone morphogenic protein-2, transcriptional coactivator with PDZ-binding motif, and TWIST2, all important regulators of RUNX2, were not impacted by the diabetic condition, suggesting that the defect in osteogenesis resides at the level of RUNX2 expression and its activity. Together, these data demonstrate that insulin and/or glycemic status can regulate osteogenesis in vivo, and systemic insulin therapy can, in large part, rescue the diabetic bone phenotype at the tissue and molecular level.

Chronic ethanol exposure inhibits distraction osteogenesis in a mouse model: role of the TNF signaling axis

Tumor necrosis factor-alpha (TNF-alpha) is an inflammatory cytokine that modulates osteoblastogenesis. In addition, the demonstrated inhibitory effects of chronic ethanol exposure on direct bone formation in rats are hypothetically mediated by TNF-alpha signaling. The effects in mice are unreported. Therefore, we hypothesized that in mice (1) administration of a soluble TNF receptor 1 derivative (sTNF-R1) would protect direct bone formation during chronic ethanol exposure, and (2) administration of recombinant mouse TNF-alpha (rmTNF-alpha) to ethanol naïve mice would inhibit direct bone formation. We utilized a unique model of limb lengthening (distraction osteogenesis, DO) combined with liquid diets to measure chronic ethanol's effects on direct bone formation. Chronic ethanol exposure resulted in increased marrow TNF, IL-1, and CYP 2E1 RNA levels in ethanol-treated vs. control mice, while no significant weight differences were noted. Systemic administration of sTNF-R1 during DO (8.0 mg/kg/2 days) to chronic ethanol-exposed mice resulted in enhanced direct bone formation as measured radiologically and histologically. Systemic rmTNF-alpha (10 microg/kg/day) administration decreased direct bone formation measures, while no significant weight differences were noted. We conclude that chronic ethanol-associated inhibition of direct bone formation is mediated to a significant extent by the TNF signaling axis in a mouse model.

In VitroMicrodistraction of Preosteoblasts: Distraction Promotes Proliferation and Oscillation Promotes Differentiation

Osteoblast biology is influenced in vivo by a 3-dimensional (3D) extracellular matrix that mediates their adhesion and interaction and by a constant state of compressive and tensile forces. To study the role of mechanical stress on osteoblasts in vitro, these parameters must be addressed. Therefore, this study describes the use of a novel, in vitro system that subjects cells to distractive and compressive forces in a 3D environment. This system, termed a microdistractor system, was used to apply linear forces to 3D collagen type I gels containing preosteoblasts. Gels were induced for up to 16 days in osteogenic medium and subjected to either constant linear distraction (distraction gels) or to repeating cycles of distraction and compression (oscillation gels). The effect of these stresses was evaluated over time by measuring proliferation rates, protein synthesis (i.e., cellular activity), and osteogenic differentiation levels. While linear forces in general appeared to increase protein synthesis, force-specific effects on proliferation and differentiation were observed. Specifically, distraction forces appeared to enhance MC3T3 proliferation while distraction/compressive forces appeared to accelerate their osteogenic differentiation program. Therefore, these results suggest that the microdistraction system may be an appropriate in vitro system for the study of mechanobiology in osteoblast phenotype.

Effects of systemic and local administration of recombinant human IGF-I (rhIGF-I) on de novo bone formation in an aged mouse model

DO was used in an aged mouse model to determine if systemically and/or locally administered rhIGF-I improved osteoblastogenesis and new bone formation. Local and systemic rhIGF-I treatment increased new bone formation. However, only systemic delivery produced measurable concentrations of rhIGF-I in the circulation.

INTRODUCTION

Human and rodent research supports a primary role for IGF-I in bone formation. Significant roles for both endocrine and paracrine/autocrine IGF-I have been suggested for normal osteoblastogenesis and bone formation. We have assessed, using a mouse model of distraction osteogenesis (DO), the impact of continuous administration of recombinant human (rh)IGF-I, delivered either locally to the distraction site or absorbed systemically, on bone formation in an aged mouse model.

MATERIALS AND METHODS

DO was performed in aged mice (18-month-old C57BL/6 male mice), which were distracted at 0.15 mm daily. At the time of osteotomy, miniosmotic pumps were inserted subcutaneously to (1) deliver vehicle or rhIGF-I subcutaneously for systemic delivery or (2) deliver vehicle or rhIGF-I directly to the newly forming bone through infusion tubing routed subcutaneously from the pump to the distraction site. Serum concentrations of mouse IGF-I, human IGF-I, and osteocalcin were determined at the end of the study.

RESULTS

New bone formation observed in DO gaps showed a significant increase in new bone formation in rhIGF-I-treated mice, irrespective of delivery route. However, detectable levels of human IGF-I were found only in the serum of animals receiving rhIGF-I systemically. Osteocalcin levels did not differ between controls and rhIGF-I-treated groups.

CONCLUSIONS

Locally and systemically delivered rhIGF-I both produce significant increases in new bone formed in an aged mouse model in which new bone formation is normally markedly impaired, suggesting that rhIGF-I may improve senile osteoporosis. Because systemic administration of IGF-I can result in untoward side effects, including an increased risk for cancer, the findings that locally delivered IGF-I improves bone regeneration without increasing circulating IGF-I levels suggests that this delivery route may be preferable in an at-risk, aged population.

A novel mouse model for the study of the inhibitory effects of chronic ethanol exposure on direct bone formation

Excessive alcohol consumption has been reported to interfere with human bone homeostasis and repair in multiple ways. Previous studies have demonstrated that chronic ethanol exposure in the rat via an intragastric dietary delivery system inhibits direct bone formation during distraction osteogenesis (DO, limb lengthening). The opportunity to extend the rat ethanol studies to mice is now possible due to the development of mouse models of DO. This study employed a novel combination of liquid ethanol diet delivery and a murine DO model to test the hypothesis that chronic ethanol exposure would result in deficits in direct bone formation during DO in contrast to the pair-fed controls. Twenty-eight 12-month-old C57BL/6 male mice were acclimated to the Lieber-DeCarli liquid control diet #710027 (Dyets Inc.) over a 1-week period. The mice were separated into two diet groups (n=14/group): pair-fed control and ethanol (diet #710260). After being on diet for 82 days, all mice underwent placement of an external fixator and osteotomy on the left tibia. Following a 6-day latency period, distraction began at a rate of 0.075 mm twice a day (b.i.d.) for 14 days. The weight changes were equivalent for both groups. The hypothesis that chronic ethanol exposure would inhibit direct bone formation and produce skeletal toxicity was supported by radiographic (P=.011) and histologic (P=.002) analyses of the % new bone formation in the DO gaps, by peripheral quantitative computed tomography analysis of the total volumetric bone mineral density of the contralateral proximal tibias (P<.001) and contralateral femoral necks (P=.012), by three-point bending on the contralateral tibias (P<.001 energy to break), by pin site bone formation measures (P<.001), and by ethanol-associated increased adipocyte area (adjacent to the gap) percentages (P<.002). We conclude that this model can be used to study the mechanisms underlying inhibition of bone formation by chronic ethanol exposure and to test preclinical interventions.

Matricellular proteins: Extracellular modulators of bone development, remodeling, and regeneration

Matricellular proteins are components of the extracellular matrix which are highly expressed in the developing and mature skeleton. Members of this protein class serve as biological mediators of cell function by interacting directly with cells or by modulating the activity of growth factors, proteases, and other extracellular matrix proteins. Although skeletons of matricellular protein-null mice are grossly normal, they each display unique deficiencies that are often magnified under pathological conditions. In addition, bone cells from wild-type and matricellular protein-null mice behave differently in various in vitro models of bone matrix synthesis and turnover. In this review, osteopontin, bone sialoprotein, tenascin C, SPARC, and thrombospondins 1 and 2 will each be discussed in the context of bone cell biology. Because the biological effects of matricellular proteins are largely context dependent, in vivo and in vitro results must be considered together in order to fully appreciate the specific contributions that matricellular proteins make to bone physiology and pathophysiology. In particular, it is clear that although matricellular proteins are not required for bone development and function, the proteins act to modulate post-natal bone structure in response to aging, ovariectomy, mechanical loading, and bone regeneration.

Bone formation is impaired in a model of type 1 diabetes

The effects of type 1 diabetes on de novo bone formation during tibial distraction osteogenesis (DO) and on intact trabecular and cortical bone were studied using nonobese diabetic (NOD) mice and comparably aged nondiabetic NOD mice. Diabetic mice received treatment with insulin, vehicle, or no treatment during a 14-day DO procedure. Distracted tibiae were analyzed radiographically, histologically, and by microcomputed tomography (microCT). Contralateral tibiae were analyzed using microCT. Serum levels of insulin, osteocalcin, and cross-linked C-telopeptide of type I collagen were measured. Total new bone in the DO gap was reduced histologically (P < or = 0.001) and radiographically (P < or = 0.05) in diabetic mice compared with nondiabetic mice but preserved by insulin treatment. Serum osteocalcin concentrations were also reduced in diabetic mice (P < or = 0.001) and normalized with insulin treatment. Evaluation of the contralateral tibiae by microCT and mechanical testing demonstrated reductions in trabecular bone volume and thickness, cortical thickness, cortical strength, and an increase in endosteal perimeter in diabetic animals, which were prevented by insulin treatment. These studies demonstrate that bone formation during DO is impaired in a model of type 1 diabetes and preserved by systemic insulin administration.

Osteopontin expression in osteoblasts and osteocytes during bone formation under mechanical stress in the calvarial suture in vivo

To clarify the role of OPN in bone formation under mechanical stress, we examined the expression and the function of OPN in bone using an expansion force-induced osteogenesis model. Our results indicated that OPN expression was enhanced during the bone formation and that OPN would be one of the positive factors for the bone formation under mechanical stress.

INTRODUCTION

Bone formation is known to be stimulated by mechanical stress; however, molecules involved in stress-dependent regulation of bone formation have not yet been fully characterized. Extracellular matrix proteins such as osteopontin (OPN) could play a role in mediation of the mechanical stress signal to osteoblasts. However, the function of OPN in bone formation under mechanical force is not known. Therefore, we examined the expression and the role of OPN in bone formation in vivo under tensile mechanical stress.

MATERIALS AND METHODS

Sagittal sutures of mice were subjected to expansion mechanical stress by setting orthodontic spring wires, and OPN expression during bone formation within the suture gap was examined.

RESULTS

Expansion of the sutures resulted in bone formation at the edges of the parietal bones within the sagittal suture. Immunohistochemical analysis revealed abundant accumulation of OPN protein in the matrix of newly formed bone on the inner edge of the parietal bone within the mechanically expanded sutures. Osteoblasts forming bone within the suture subjected to tensile stress also exhibited high levels of OPN protein expression. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicated that OPN mRNA expression was enhanced in wild-type calvariae subjected to expansion force compared with the control calvariae where dead spring wires were set without expansion stress. In addition, type I collagen mRNA was also expressed in the calvariae under the mechanical stimuli. To understand the function of OPN, sagittal sutures in OPN-deficient mice were subjected the expansion stress, and bone formation within the suture to fill the expanded gap was compared with that observed in wild-type mice. OPN deficiency reduced bone formation at the edge of the parietal bone in contact with the expanded suture gap.

CONCLUSIONS

These observations revealed that OPN plays a pivotal role in bone formation under tensile mechanical stress.