Expression of osteopontin mRNA by osteoclasts and osteoblasts in modelling adult human bone

Phylobone: a comprehensive database of bone extracellular matrix proteins in human and model organisms

The bone extracellular matrix (ECM) contains minerals deposited on highly crosslinked collagen fibrils and hundreds of non-collagenous proteins. Some of these proteins are key to the regulation of bone formation and regeneration via signaling pathways, and play important regulatory and structural roles. However, the complete list of bone extracellular matrix proteins, their roles, and the extent of individual and cross-species variations have not been fully captured in both humans and model organisms. Here, we introduce the most comprehensive resource of bone extracellular matrix (ECM) proteins that can be used in research fields such as bone regeneration, osteoporosis, and mechanobiology. The Phylobone database (available at https://phylobone.com ) includes 255 proteins potentially expressed in the bone extracellular matrix (ECM) of humans and 30 species of vertebrates. A bioinformatics pipeline was used to identify the evolutionary relationships of bone ECM proteins. The analysis facilitated the identification of potential model organisms to study the molecular mechanisms of bone regeneration. A network analysis showed high connectivity of bone ECM proteins. A total of 214 functional protein domains were identified, including collagen and the domains involved in bone formation and resorption. Information from public drug repositories was used to identify potential repurposing of existing drugs. The Phylobone database provides a platform to study bone regeneration and osteoporosis in light of (biological) evolution, and will substantially contribute to the identification of molecular mechanisms and drug targets.

Comparative Study of the Cytokine Profiles of Serum and Tissues from Patients with the Ossification of the Posterior Longitudinal Ligament

BACKGROUND

The ossification of the posterior longitudinal ligament (OPLL) is one of the contributing factors leading to severe cervical spondylotic myelopathy (CSM). The mechanism causing ossification is still unclear. The current study was designed to analyze the specimens of patients with or without OPLL.

METHODS

The study collected 51 patients with cervical spondylosis. There were six serum samples in both the non-OPLL (NOPLL) and OPLL groups. For tissue analysis, there were seven samples in the NOPLL group and five samples in the OPLL group. The specimens of serum and tissue were analyzed by using Human Cytokine Antibody Arrays to differentiate biomarkers between the OPLL and NOPLL groups, as well as between serum and OPLL tissue. Immunohistochemical staining of the ligament tissue was undertaken for both groups.

RESULTS

For OPLL vs. NOPLL, the serum leptin levels are higher in the OPLL group, corroborating others' observations that it may serve as a disease marker. In the tissue, angiogenin (ANG), osteopontin (OPN), and osteopro-tegerin (OPG) are higher than they are in the OPLL group (p < 0.05). For serum vs. OPLL tissue, many chemotactic cytokines demonstrated elevated levels of MIP1 delta, MCP-1, and RANTES in the serum, while many cytokines promoting or regulating bone genesis were up-regulated in tissue (oncostatin M, FGF-9, LIF, osteopontin, osteoprotegerin, TGF-beta2), as well as the factor that inhibits osteoclastogenesis (IL-10), with very few cytokines responsible for osteoclastogenesis. Molecules promoting angiogenesis, including angiotensin, vEGF, and osteoprotegerin, are abundant in the OPLL tissue, which paves the way for robust bone growth.

Impact of Sclerotic Lesions on the Surgical Outcome of Cholesteatoma

OBJECTIVE

Cholesteatoma is occasionally accompanied by excessive calcification and presumably has different osteogenic dynamics compared to noncholesteatomous chronic otitis media. Cholesteatoma-related sclerotic lesions through the temporal bone can pose manipulatory difficulties, possibly leading to worse surgical outcomes or complications. Therefore, we compared surgical outcomes of cholesteatomas with and without sclerotic lesions.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary academic medical center.

PATIENTS

Consecutive ears with acquired cholesteatomas requiring primary resection between January 2009 and December 2019. The ears followed up for <1 year were excluded.

INTERVENTIONS

Tympanoplasty with/without mastoidectomy.

MAIN OUTCOME MEASURES

Prevalence and location of sclerotic lesion, comorbid fistulae, postoperative air-bone gap, recidivism, and complications.

RESULTS

Overall, 19 (6.4%) of 299 ears had sclerotic lesions. More than two-thirds (68.4%) of sclerotic lesions were located adjacent to the lateral semicircular canal (LSC). Among ears with sclerotic lesions adjacent to the LSC, 46.2% had a comorbid fistula in the LSC. The prevalence of labyrinth fistula was significantly greater in ears with sclerotic lesions (42.1%) than in ears without sclerotic lesions (5.0%) (p < 0.0001, Fisher's exact test). Sensorineural hearing deterioration was significantly higher in ears with sclerotic lesions than in ears without (p = 0.0004, Fisher's exact test). Multivariate logistic regression analysis demonstrated that the presence of sclerotic lesions was a significant prognostic factor for residual disease (odds ratio [95% confidence interval]: 6.820 [2.055-22.633], p = 0.0017).

CONCLUSIONS

Surgeons should be conscious of preoperative identification of sclerotic lesions adjacent to one of the semicircular canals, possibly leading to postoperative sensorineural hearing deterioration or residual cholesteatoma.

Assessment of the effect of silica calcium phosphate nanocomposite on mesenchymal stromal cell differentiation and bone regeneration in critical size defect

Objective

The research was designed to assess silica calcium phosphate nanocomposite (SCPC) biocompatibility and bioactivity as an osteoinductive scaffold and cell carrier. Consequently, the ability of cell seeded SCPC implant to regenerate a critical size defect in rat calvarium.

Materials and Methods

The study was conducted in two parts. A series of in vitro experiments on bone marrow stromal cells (MSCs) seeded in the SCPC scaffold evaluated cell attachment, proliferation and osteogenic differentiation. In the second part, a cell seeded SCPC construct was implanted in rat calvarium and bone regeneration was assessed by histological examination to evaluate the newly formed bone quality and the residual graft volume.

Results

In vitro experimentation revealed that MSCs cultured on SCPC maintained viability and proliferation when seeded into the SCPC. Scanning electron microscopy demonstrated cell adhesion and calcium appetite formation, MSCs differentiated towards the osteogenic lineage as indicated by the upregulation of RUNX2, ALP, Col1a1 markers. Histological examination showed regeneration from the periphery and core of the defect with new bone formation at different stages of maturation.

Conclusion

Regenerative medicine delivers promising solutions and technologies for application in craniofacial reconstruction. SCPC scaffold has the potential to be used as a cell carrier to achieve stem cell-based bone regeneration, which provides a viable alternative for treatment of challenging critical size defect.

Single-cell RNA-seq reveals functionally distinct biomaterial degradation-related macrophage populations

Macrophages play crucial roles in host tissue reaction to biomaterials upon implantation in vivo. However, the complexity of biomaterial degradation-related macrophage subpopulations that accumulate around the implanted biomaterials in situ is not fully understood. Here, using single cell RNA-seq, we analyze the transcriptome profiles of the various cell types around the scaffold to map the scaffold-induced reaction, in an unbiased approach. This enables mapping of all biomaterial degradation-associated cells at high resolution, revealing distinct subpopulations of tissue-resident macrophages as the major cellular sources of biomaterial degradation in situ. We also find that scaffold architecture can affect the mechanotransduction and catabolic activity of specific material degradation-related macrophage subpopulations in an Itgav-Mapk1-Stat3 dependent manner, eventually leading to differences in scaffold degradation rate in vivo. Our work dissects unanticipated aspects of the cellular and molecular basis of biomaterial degradation at the single-cell level, and provides a conceptual framework for developing functional tissue engineering scaffolds in future.

Circular RNA Circ_0005564 promotes osteogenic differentiation of bone marrow mesenchymal cells in osteoporosis

Circular RNA (CircRNA) plays a potential role in bone formation. We aimed to study the circRNAs expression profiles and their functions in osteogenic differentiation of human bone marrow stromal cells (BMSCs). Firstly, we established osteogenic differentiation of BMSCs displaying increased mRNA expression of osteogenic differentiation marker (RUNX2, OPN, and OCN), increased ALP activity and protein expression, and increased mineralized nodules formation, as well as morphological alteration. Then, we employed high-throughput sequencing to analyze circRNA expression and found that 3440 and 3893 circRNAs in non-induced and induced groups, respectively. We further validated the 10 differentially expressed circRNAs with the most significant difference between induced and non-induced groups. Among these ten circRNAs, five of them with more than one miRNA binding site were used to construct a ceRNA network exhibiting 81 miRNAs and 182 target mRNAs. Furthermore, among these five circRNAs, we found only circ_0005564 significantly reduced the mRNA expression of RUNX2, OPN, and OCN. The circularity of circ_0005564 was verified. Our results showed that knockdown of circ_0005564 inhibited osteoblast differentiation in BMSCs. Taken together, our study demonstrates that circ_0005564 is a potential positive regulator of osteogenic differentiation of BMSCs.

Human Serum Enhances Biomimicry of Engineered Tissue Models of Bone and Cancer

For decades, fetal bovine serum (FBS) has been used routinely for culturing many cell types, based on its empirically demonstrated effects on cell growth, and the lack of suitable non-xenogeneic alternatives. The FBS-based culture media do not represent the human physiological conditions, and can compromise biomimicry of preclinical models. To recapitulate in vitro the features of human bone and bone cancer, we investigated the effects of human serum and human platelet lysate on modeling osteogenesis, osteoclastogenesis, and bone cancer in two-dimensional (2D) and three-dimensional (3D) settings. For monitoring tumor growth within tissue-engineered bone in a non-destructive fashion, we generated cancer cell lines expressing and secreting luciferase. Culture media containing human serum enhanced osteogenesis and osteoclasts differentiation, and provided a more realistic in vitro mimic of human cancer cell proliferation. When human serum was used for building 3D engineered bone, the tissue recapitulated bone homeostasis and response to bisphosphonates observed in native bone. We found disparities in cell behavior and drug responses between the metastatic and primary cancer cells cultured in the bone niche, with the effectiveness of bisphosphonates observed only in metastatic models. Overall, these data support the utility of human serum for bioengineering of bone and bone cancers.

Relationship Between Clinicopathological Features and Prognosis in Appendicular Osteosarcoma in Dogs

Osteosarcoma is the most common primary bone neoplasm in dogs and often involves the appendicular skeleton. We report the clinicopathological and prognostic features of appendicular osteosarcomas diagnosed in 153 dogs from 2008 to 2018. The survival data for 22 dogs that underwent surgery and chemotherapy were statistically compared with the clinical, histopathological and immunohistochemical data for correlation with prognosis. The affected dogs had a mean age of 9.1 years and a mean body weight of 33.4 kg. No sex predilection was detected, although the incidence was slightly higher in females (52%). Large mixed and purebred dogs were most commonly affected. Long bones were affected in 124 cases (92.5%; 124/134). The extremities affected within long bones were the metaphysis of the proximal humerus (29%), distal radius (17.7%), distal femur (15.3%) and proximal tibia (7.2%). Histologically, osteoblastic osteosarcoma was most commonly detected (56.9%), followed by chondroblastic (13.7%), telangiectatic (11.8%), fibroblastic (7.8%), giant cell-rich (5.2%) and poorly differentiated neoplasms (4.6%). Regional lymph nodes were available for analysis in 28 out of 70 excisional biopsies from amputated entire limbs. Metastases to regional lymph nodes were observed in 14.3% (4/28) of these cases. Distant metastases were found in 75% (39/52) of cases in which diagnostic imaging or necropsy was carried out. The lungs were the most common site of metastasis (87.2%; 34/39 cases). Weight, age, sex, affected limb or bone, histological classification, mitotic count or histological grade did not influence survival (P >0.05). Neoplasms located at proximal extremities (n = 7) of affected limbs had a tendency for a poorer prognosis than those at distal extremities (n = 15) (P = 0.06). For these cases, the 1-year survival rate was 14.3% compared with 40% for neoplasms at distal extremities. There was no significant difference in the survival rate when amputation (n = 16) or limb preservation (n = 6) techniques were employed with chemotherapy (P = 0.20). The survival period of dogs that had undergone limb amputation, or limb preservation surgery, and chemotherapy was 73-1,185 days, with a mean and median of 376 and 256 days, respectively. Mild to marked cytoplasmic immunolabelling of osteopontin was found in all cases but the intensity (P = 0.66) and percentage of neoplastic cells labelled (P = 0.49) did not influence survival.

In situ miRNA delivery from a hydrogel promotes osteogenesis of encapsulated mesenchymal stromal cells

Hydrogels are attractive candidates for use in tissue-engineering and the encapsulation and subsequent differentiation of mesenchymal stem/stromal cells (MSCs) is a strategy that holds great promise for the repair and regeneration of bone and cartilage. However, MSCs are well-known for their sensitivity to mechanical cues, particularly substrate stiffness, and so the inherent softness of hydrogels is poorly matched to the mechanical cues that drive efficient osteogenesis. One approach to overcome this limitation is to harness mechanotransductive signalling pathways and override the signals cells receive from their environment. Previous reports demonstrate that mechanosensitive miRNAs, miR-100-5p and miR-143-3p can enhance MSC osteogenesis, using a complex multi-step procedure to transfect, encapsulate and differentiate the cells. In this study, we develop and characterise a facile system for in situ transfection of MSCs encapsulated within a light-crosslinkable gelatin-PEG hydrogel. Comparing the influence of different transfection agents and hydrogel compositions, we show that particle size, charge, and hydrogel mechanical properties all influence the diffusion of embedded transfection agent complexes. By incorporating both MSCs and transfection agents into the hydrogels we demonstrate successful in situ transfection of encapsulated MSCs. Comparing the efficacy of pre- and in situ transfection of miR-100-5p/miR-143-3p on the osteogenic capacity of hydrogel-encapsulated MSCs, our data demonstrates superior mineralisation and osteogenic gene expression following in situ transfections. Overall, we demonstrate a simple, one-pot system for in situ transfection of miRNAs to enhance MSC osteogenic potential and thus demonstrates significant promise to improve the efficiency of MSC differentiation in hydrogels for bone tissue-engineering applications. STATEMENT OF SIGNIFICANCE: Mesenchymal stromal cells (MSCs) are sensitive to cues from their surrounding microenvironment. Osteogenesis is enhanced in MSCs grown on stiffer substrates, but this is limited when using hydrogels for bone tissue-engineering. Modulating pro-osteogenic genes with mechanosensitive microRNAs (miRNAs) represents a potential tool to overcome this challenge. Here we report a hydrogel platform to deliver miRNAs to encapsulated MSCs. We characterise effects of hydrogel composition and transfection agent type on their mobility and transfection efficiency, demonstrating successful in situ transfection of MSCs and showing that miRNAs can significantly enhance osteogenic mineral deposition and marker gene expression. This system was simpler and more effective than conventional 2D transfection prior to encapsulation and therefore holds promise to improve MSC differentiation in bone tissue-engineering.

Impact of Serum Source on Human Mesenchymal Stem Cell Osteogenic Differentiation in Culture

Human mesenchymal stem cells (MSCs) show promise for musculoskeletal repair applications. Animal-derived serum is extensively used for MSC culture as a source of nutrients, extracellular matrix proteins and growth factors. However, the routine use of fetal calf serum (FCS) is not innocuous due to its animal antigens and ill-defined composition, driving the development of alternatives protocols. The present study sought to reduce exposure to FCS via the transient use of human serum. Transient exposure to animal serum had previously proved successful for the osteogenic differentiation of MSCs but had not yet been tested with alternative serum sources. Here, human serum was used to support the proliferation of MSCs, which retained surface marker expression and presented higher alkaline phosphatase activity than those in FCS-based medium. Addition of osteogenic supplements supported strong mineralisation over a 3-week treatment. When limiting serum exposure to the first five days of treatment, MSCs achieved higher differentiation with human serum than with FCS. Finally, human serum analysis revealed significantly higher levels of osteogenic components such as alkaline phosphatase and 25-Hydroxyvitamin D, consistent with the enhanced osteogenic effect. These results indicate that human serum used at the start of the culture offers an efficient replacement for continuous FCS treatment and could enable short-term exposure to patient-derived serum in the future.

Identification and characterization of a polysaccharide from the roots of Morinda officinalis, as an inducer of bone formation by up-regulation of target gene expression

Morinda officinalis is an important traditional tonic herbal medicine. In the present study, we found that crude polysaccharides extracted from M. officinalis, named MO90, could significantly increase the bone mineral density (BMD) of the whole femur, distal femur, and proximal femur in ovariectomized (OVX) rats. In addition, MO90 decreased the level of bone turnover markers and prevented the deterioration of trabecular microarchitecture. To investigate the fractions responsible for anti-osteoporosis activity, one novel inulin-type fructan, MOW90-1, was isolated from MOP90. Structural analysis indicated that MOW90-1 consists of a backbone of (2→1)-linked-β-D-Fruf, and is terminated with (1→)-linked-α-D-Glcp and (2→)-linked-β-D-Fruf. Furthermore, an in vitro anti-osteoporosis assay indicated that MOW90-1 promoted proliferation, differentiation, and mineralization of MC3T3-E1 cells by up-regulating the expression of runt-related transcription factor 2, osterix, osteopontin, and osteocalcin. In conclusion, our studies provide supporting evidence for future use of this novel M. officinalis fructan as a key nutrient of health products.

A novel electron emission-based cell culture device promotes cell proliferation and differentiation of pre-osteoblastic MC3T3-E1 cells

In this report we demonstrate the effect of a novel electron emission-based cell culture device on the proliferation and differentiation of pre-osteoblastic MC3T3-E1 cells. Our device has an electron emission element that allows, for the first time, stable emission of electrons into an atmosphere. Atmospheric electrons react with gas molecules to generate radicals and negative ions, which induce a variety of biochemical reactions in the attached cell culture system. In this study, we demonstrated the effect of this new electron emission-based cell culture device on cell proliferation and differentiation using pre-osteoblastic MC3T3-E1 cells. Electron emission stimulation (EES) was applied directly to culture medium containing plated cells, after which the number of living cells, the mRNA levels of osteogenesis-related genes, and the alkaline phosphatase (ALP) activity were evaluated. The growth rate of EES-exposed cells increased by approximately 20% in comparison with unexposed control cells. We also found the mRNA levels of osteogenic specific genes such as collagen type I α-1, core-binding factor α-1, and osteocalcin to be up-regulated following EES. ALP activity, a marker for osteogenic activity, was significantly enhanced in EES-treated cells. Furthermore, reactive oxygen species generated by EES were measured to determine their effect on MC3T3-E1 cells. These results suggest that our new electron emission-based cell culture device, while providing a relatively weak stimulus in comparison with atmospheric plasma systems, promotes cell proliferation and differentiation. This system is expected to find application in regenerative medicine, specifically in relation to bone regeneration.

NR4A1 Regulates Motility of Osteoclast Precursors and Serves as Target for the Modulation of Systemic Bone Turnover

NR4A1 (Nur77 or NGFI-B), an orphan member of the nuclear receptor superfamily, has been identified as a key regulator of the differentiation and function of myeloid, lymphoid, and mesenchymal cells. The detailed role of NR4A1 in bone biology is incompletely understood. Here, we report a role for NR4A1 as novel factor controlling the migration and recruitment of osteoclast precursors during bone remodeling. Myeloid-specific but not osteoblast-specific deletion of NR4A1 resulted in osteopenia due to an increase in the number of bone-lining osteoclasts. Although NR4A1-deficient osteoclast precursors displayed a regular differentiation into mature osteoclasts, they showed a hyper-motile phenotype that was largely dependent on increased osteopontin expression, suggesting that expression of NR4A1 negatively controlled osteopontin-mediated recruitment of osteoclast precursors to the trabecular bone. Pharmacological activation of NR4A1, in turn, inhibited osteopontin expression and osteopontin-dependent migration of osteoclast precursors resulted in reduced abundance of bone-resorbing osteoclasts in vivo as well as in an ameliorated bone loss after ovariectomy in mice. This study identifies NR4A1 as a crucial player in the regulation of osteoclast biology and bone remodeling and highlights this nuclear receptor as a promising target for therapeutic intervention during the treatment of osteoporosis. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

miRNA-133a-5p Inhibits the Expression of Osteoblast Differentiation-Associated Markers by Targeting the 3' UTR of RUNX2

Recent studies have recognized the involvement of microRNAs (miRNAs) in the development of osteoporosis, which regulate the balance between osteogenesis and osteoclasis. In this study, we investigated the regulation by miRNA-133a-5p on the osteoblast differentiation-associated markers in the mouse osteoblast-like MC3T3-E1 cells by RUNX2. First, we manipulated the miRNA-133a level in the MC3T3-E1 cells with 20 or 40 nM miR-133a-5p mimics, miR-133a-5p inhibitor, or scramble miRNA. Then, we quantified with real-time polymerase chain reaction (qRT-PCR) the expression of Collagen I, osteocalcin (OCN), and osteopontin (OPN) in the miR-133a-5p-manipulated MC3T3-E1 cells. And the confocal microscopy was also utilized to confirm the regulation by miR-133a-5p on the expression of the three molecules. We also investigated the extracellular matrix (ECM) mineralization and the alkaline phosphatase (ALP) activity in the miR-133a-5p-manipulated MC3T3-E1 cells. In addition, we explored the possible targeting by miR-133a-5p on RUNX2, which was a well-recognized promoter to osteoblast differentiation, with luciferase reporter, qRT-PCR, and Western blotting assay. Results demonstrated that the miRNA-133a-5p mimics markedly reduced, whereas the miRNA-133a-5p inhibitor significantly promoted the expression of Collagen I, OCN, and OPN, the ECM mineralization, and the ALP activity in MC3T3-E1 cells. The alignment analysis demonstrated a high homology between miRNA-133a-5p and the 3' UTR of RUNX2. Moreover, the luciferase reporter assay demonstrated that miRNA-133a-5p targeted the 3' UTR of RUNX2, and inhibited the expression of RUNX2 in both mRNA and protein levels. In conclusion, we identified the inhibition by miRNA-133a-5p to the expression of osteoblast differentiation markers, to the ECM mineralization, and to the ALP activity in MC3T3-E1 cells, by targeting the 3' UTR of RUNX2. Our study suggests that miRNA-133a-5p might be an important target to inhibit osteoblast differentiation in osteoporosis.

Interferon-γ is a master checkpoint regulator of cytokine-induced differentiation

Cytokines are protein mediators that are known to be involved in many biological processes, including cell growth, survival, inflammation, and development. To study their regulation, we generated a library of 209 different cytokines. This was used in a combinatorial format to study the effects of cytokines on each other, with particular reference to the control of differentiation. This study showed that IFN-γ is a master checkpoint regulator for many cytokines. It operates via an autocrine mechanism to elevate STAT1 and induce internalization of gp130, a common component of many heterodimeric cytokine receptors. This targeting of a receptor subunit that is common to all members of an otherwise diverse family solves the problem of how a master regulator can control so many diverse receptors. When one adds an autocrine mechanism, fine control at the level of individual cells is achieved.

Evaluation of destruction in a collagen-induced arthritis rat model: Bony spur formation

Over the past 40 years, the collagen-induced arthritis (CIA) animal model has been widely used as a model of rheumatoid arthritis (RA). However, no model is able to completely depict the characteristics of cartilage destruction to date. In the later stage of joint cartilage destruction, bony spurs form in RA. This bony spur formation is an important symptom in the pathological development of RA. In the present study, CIA was used to elucidate the pathological process of bony spur formation. Joint damage and spur formation in the animal model was detected by radiology and histology. Radiology identified bony spurs in the knee and foot joints, which worsened as the disease progressed. Furthermore, following observations of histological sections, fusion and damage of the articular cartilage, as well as a higher number of osteoclasts, were identified. Previous results have determined that bony spurs may be involved in another pathological process that occurs during the later stages of RA. Therefore, further studies investigating this symptom are required to improve the understanding of RA and facilitate the development of an appropriate treatment for RA.

Tissue-Engineered Model of Human Osteolytic Bone Tumor

Ewing's sarcoma (ES) is a poorly differentiated pediatric tumor of aggressive behavior characterized by propensity to metastasize to bone. Interactions between the tumor and bone cells orchestrate a vicious cycle in which tumor cells induce osteoclast differentiation and activation to cause osteolytic lesions, broken bones, pain, and hypercalcemia. The lack of controllable models that can recapitulate osteolysis in ES impedes the development of new therapies and limits our understanding of how tumor cells invade bone. In response to this need, tissue-engineered models are now being developed to enable quantitative, predictive studies of human tumors. In this study, we report a novel bioengineered model of ES that incorporates the osteolytic process. Our strategy is based on engineering human bone containing both osteoclasts and osteoblasts within three-dimensional mineralized bone matrix. We show that the bone matrix is resorbed by mature osteoclasts while the new bone matrix is formed by osteoblasts, leading to calcium release and bone remodeling. Introduction of ES cell aggregates into the bone niche induced decreases in bone density, connectivity, and matrix deposition. Additionally, therapeutic reagents, such as zoledronic acid, which have demonstrated efficacy in ES treatment, inhibited bone resorption mediated by osteoclasts in the tumor model.

Adipocytes enhance expression of osteoclast adhesion-related molecules through the CXCL12/CXCR4 signalling pathway

OBJECTIVES

The purpose of this study was to investigate effects of adipocytes on osteoclast adhesion-related molecules.

MATERIALS AND METHODS

ST2 cells, a cloned stromal cell line from mouse bone marrow, able to differentiate into adipocytes, were cultured in serum-free α-MEM which was then collected to be used as adipocyte-conditioned medium (ADIPO CM). RAW264.7 cells were cultured in ADIPO CM in the presence of RANKL, and bone marrow-derived macrophages were cultured in ADIPO CM in the presence of RANKL and macrophage-colony stimulating factor to induce osteoclast differentiation. TRAP staining, resorption pit assay, qRT-PCR and western blotting assays were performed.

RESULTS

ELISAs revealed that CXCL12 was abundant in ADIPO CM and CCK-8 assay revealed no proliferation of RAW264.7 cells after exogenous CXCL12 treatment. ADIPO CM enhanced osteoclast formation and resorption, both by RAW264.7 cells and BMMs. In addition, exogenous CXCL12 efficiently potentiated formation of TRAP-positive osteoclast and resorption by RAW264.7 cells. Western blotting and qRT-PCR suggested that ADIPO CM or combined treatment with exogenous CXCL12 caused significant increase in expression of NFAT2, src and osteoclast adhesion-related molecules, including β3 integrin, CD44 and osteopontin. However, these promotional effects were largely abrogated on treatment of AMD3100, a CXCR4 antagonist.

CONCLUSIONS

Adipocytes promoted osteoclast differentiation, function and expression of adhesion-related molecules through the CXCL12/CXCR4 signalling pathway.

Cytotoxicity of Experimental Resin Composites on Mesenchymal Stem Cells Isolated from Two Oral Sources

Resin composite materials that are used to restore tooth cervical lesions associated with gingival recessions can hamper healing after root coverage surgeries. This study evaluates the in vitro cytotoxic effect of five resin composites (two commercial and three experimental) on oral mesenchymal stem cells (MSCs) and the persistence of stemness properties in high passage MSCs. Sorption and solubility tests were made for all materials. MSCs were isolated from re-entry palatal and periodontal granulation tissues and were characterized and cultured on composite discs. Cytotoxicity of the materials was evaluated by the Alamar Blue viability test, by Paul Karl Horan (PKH) labeling, and by immunocytochemical staining for actin. Water and saliva sorption and solubility data revealed that two of the experimental materials behaved comparable with the marketed resin composites. The Alamar Blue viability test shows that both cell lines grew well on composite discs that seemed to induce no apparent toxic effects. No signs of disruption of cytoskeleton organization was seen. Experimental resin composites can be recommended for further investigation for obtaining approval for use. The standard minimal criteria were fulfilled for high passage MSCs. Palatal tissue regains its regenerative properties in terms of MSC presence in the re-entry area after 6 months of healing.

Modulation of Osteogenesis in MC3T3-E1 Cells by Different Frequency Electrical Stimulation

Electrical stimulation (ES) is therapeutic to many bone diseases, from promoting fracture regeneration to orthopedic intervention. The application of ES offers substantial therapeutic potential, while optimal ES parameters and the underlying mechanisms responsible for the positive clinical impact are poorly understood. In this study, we assembled an ES cell culture and monitoring device. Mc-3T3-E1 cells were subjected to different frequency to investigate the effect of osteogenesis. Cell proliferation, DNA synthesis, the mRNA levels of osteosis-related genes, the activity of alkaline phosphatase (ALP), and intracellular concentration of Ca²⁺ were thoroughly evaluated. We found that 100 Hz could up-regulate the mRNA levels of collagen I, collagen II and Runx2. On the contrary, ES could down-regulate the mRNA levels of osteopontin (OPN). ALP activity assay and Fast Blue RR salt stain showed that 100 Hz could accelerate cells differentiation. Compared to the control group, 100 Hz could promote cell proliferation. Furthermore, 1 Hz to 10 Hz could improve calcium deposition in the intracellular matrix. Overall, these results indicate that 100Hz ES exhibits superior potentialities in osteogenesis, which should be beneficial for the clinical applications of ES for the treatment of bone diseases.

Retinoic acid-induced premature osteoblast-to-preosteocyte transitioning has multiple effects on calvarial development

We have previously shown that, in human and zebrafish, hypomorphic mutations of the gene encoding the retinoic acid (RA)-metabolizing enzyme Cyp26b1 result in coronal craniosynostosis, caused by an RA-induced premature transitioning of suture osteoblasts to preosteocytes, inducing ectopic mineralization of the suture's osteoid matrix. In addition, we showed that human CYP26B1 null patients have more severe and seemingly opposite skull defects, characterized by smaller and fragmented calvaria, but the cellular basis of these defects remained largely unclear. Here, by treating juvenile zebrafish with exogenous RA or a chemical Cyp26 inhibitor in the presence or absence of osteogenic cells or bone-resorbing osteoclasts, we demonstrate that both reduced calvarial size and calvarial fragmentation are also caused by RA-induced premature osteoblast-to-preosteocyte transitioning. During calvarial growth, the resulting osteoblast deprival leads to decreased osteoid production and thereby smaller and thinner calvaria, whereas calvarial fragmentation is caused by increased osteoclast stimulation through the gained preosteocytes. Together, our data demonstrate that RA-induced osteoblast-to-preosteocyte transitioning has multiple effects on developing bone in Cyp26b1 mutants, ranging from gain to loss of bone, depending on the allelic strength, the developmental stage and the cellular context.

Interactions between osteopontin and vascular endothelial growth factor: Implications for skeletal disorders

Osteopontin (OPN) and vascular endothelial growth factor (VEGF) are characterized by a convergence in function for maintaining the homeostasis of the skeletal and renal systems (the bone-renal-vascular axis regulates bone metabolism). The two cytokines contribute to bone remodeling, dental healing, kidney function, and the adjustment to microgravity. Often, they are co-expressed or one molecule induces the other, however, in some settings OPN-associated pathways and VEGF-associated pathways are distinct. In bone remodeling, OPN and VEGF are regulated under the influence of growth factors and hormones, hypoxia and inflammation, the micro-environment, and various physical forces. Their abundance can be affected by drug treatment. OPN and VEGF are variably associated with kidney disease. Their balanced levels are critical for restoring endothelial cell function and ameliorating the adverse effects of microgravity. Here, we review the relevant 83 papers of 257 articles published, and listed in PubMed under the key words OPN and VEGF.

Levels of matrix metalloproteinase-7 and osteopontin in human gingival crevicular fluid during initial tooth movement

Purpose

During orthodontic treatment, the early response of periodontal tissues to mechanical stress involves several metabolic changes that allow tooth movement. The purpose of this investigation was to evaluate osteopontin (OPN) and matrix metalloproteinase (MMP)-7 in the gingival crevicular fluid (GCF) of human teeth exposed to orthodontic force.

Materials and Methods

GCF samples were obtained from 15 healthy orthodontic patients (age, 12-22 years). In each patient, the left maxillary canine having the fixed orthodontic appliance was used as the test tooth, and its antagonist, with no appliance, was the control. Orthodontic force, 75 g was applied using a 16 × 22 beta titanium closing loop. The GCF sampling on the disto-buccal aspects of experimental and control tooth was performed at specific time interval with sterilized absorbent paper point. Processing was carried out with enzyme-linked immunosorbent assay to detect OPN and MMP-7 levels.

Results

The peak level of OPN was seen after 1 h application of orthodontic force which was 1280.36 pg/ml ± 185.02. The peak level of MMP-7 was seen at 0 h which was 598.3 pg/ml ± 107.5. The levels of OPN after 1 h increased to 1280.36 pg/ml ± 185.02, and they decreased at 24 h to 1012.86 pg/ml ± 168.47 (P= 0.001). The levels of MMP-7 after 1 h decreased to 478 pg/ml ± 99.7 which increased at 24 h to 526.9 pg/ml ± 99.2.

Conclusions

Orthodontic forces affect both OPN and MMP-7 protein levels on the compression side in a time-dependent fashion.

Differences in Otosclerotic and Normal Human Stapedial Osteoblast Properties Are Normalized by Alendronate in Vitro

Objective

Identify and compare phenotypic properties of osteoblasts from patients with otosclerosis (OSO), normal bones (HOB), and normal stapes (NSO) to determine a possible cause for OSO hypermineralization and assess any effects of the bisphosphonate, alendronate.

Study Design

OSO (n = 11), NSO (n = 4), and HOB (n = 13) cultures were assayed for proliferation, adhesion, mineralization, and gene expression with and without 10–10M-10–8M alendronate.

Setting

Academic hospital.

Methods

Cultures were matched for age, sex, and passage number. Cell attachment and proliferation + alendronate were determined by Coulter counting cells and assaying tritiated thymidine uptake, respectively. At 7, 14, and 21 days of culture + alendronate, calcium content and gene expression by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were determined.

Results

OSO had significantly more cells adhere but less proliferation than NSO or HOB. Calcification was significantly increased in OSO compared to HOB and NSO. NSO and HOB had similar cell adhesion and proliferation rates. A dose-dependent effect of alendronate on OSO adhesion, proliferation, and mineralization was found, resulting in levels equal to NSO and HOB. All cultures expressed osteoblast-specific genes such as RUNX2, alkaline phosphatase, type I collagen, and osteocalcin. However, osteopontin was dramatically reduced, 9.4-fold at 14 days, in OSO compared to NSO. Receptor activator of nuclear factor κB ligand/osteoprotegerin (RANKL/OPG), important in bone resorption, was elevated in OSO with decreased levels of OPG levels. Alendronate had little effect on gene expression in HOB but in OSO increased osteopontin levels and decreased RANKL/OPG.

Conclusions

OSO cultures displayed properties of hypermineralization due to decreased osteopontin (OPN) and also had increased RANKL/OPG, which were normalized by alendronate.

Cellular and molecular bases of skeletal regeneration: what can we learn from genetic mouse models?

Although bone repairs through a very efficient regenerative process in 90% of the patients, many factors can cause delayed or impaired healing. To date, there are no reliable biological parameters to predict or diagnose bone repair defects. Orthopedic surgeons mostly base their diagnoses on radiographic analyses. With the recent progress in our understanding of the bone repair process, new methods may be envisioned. Animal models have allowed us to define the key steps of bone regeneration and the biological and mechanical factors that may influence bone healing in positive or negative ways. Most importantly, small animal models such as mice have provided powerful tools to apprehend the genetic bases of normal and impaired bone healing. The current review presents a state of the art of the genetically modified mouse models that have advanced our understanding of the cellular and molecular components of bone regeneration and repair. The review illustrates the use of these models to define the role of inflammation, skeletal cell lineages, signaling pathways, the extracellular matrix, osteoclasts and angiogenesis. These genetic mouse models promise to change the field of orthopedic surgery to help establish genetic predispositions for delayed repair, develop models of non-union that mimic the human conditions and elaborate new therapeutic approaches to enhance bone regeneration.

The size of surface microstructures as an osteogenic factor in calcium phosphate ceramics

The microporosity of calcium phosphate (CaP) ceramics has been shown to have an essential role in osteoinduction by CaP ceramics after ectopic implantation. Here we show that it is not the microporosity but the size of surface microstructural features that is the most likely osteogenic factor. Two tricalcium phosphate (TCP) ceramics, namely TCP-S and TCP-B, were fabricated with equivalent chemistry and similar microporosity but different sizes of surface microstructural features. TCP-S has a grain size of 0.99 ± 0.20 μm and a micropore size of 0.65 ± 0.25 μm, while TCP-B displays a grain size of 3.08 ± 0.52 μm and a micropore size of 1.58 ± 0.65 μm. In vitro, both cell proliferation and osteogenic differentiation were significantly enhanced when human bone marrow stromal cells were cultured on TCP-S without any osteogenic growth factors, compared to TCP-B ceramic granules. The possible involvement of direct contact between cells and the TCP ceramic surface in osteogenic differentiation is also shown with a trans-well culture model. When the ceramic granules were implanted in paraspinal muscle of dogs for 12 weeks, abundant bone was formed in TCP-S (21 ± 10% bone in the available space), whereas no bone was formed in any of the TCP-B implants. The current in vitro and in vivo data reveal that the readily controllable cue, i.e. the size of the surface microstructure, could be sufficient to induce osteogenic differentiation of mesenchymal stem cells, ultimately leading to ectopic bone formation in calcium phosphate ceramics.

Zebrafish enpp1 mutants exhibit pathological mineralization, mimicking features of generalized arterial calcification of infancy (GACI) and pseudoxanthoma elasticum (PXE)

In recent years it has become clear that, mechanistically, biomineralization is a process that has to be actively inhibited as a default state. This inhibition must be released in a rigidly controlled manner in order for mineralization to occur in skeletal elements and teeth. A central aspect of this concept is the tightly controlled balance between phosphate, a constituent of the biomineral hydroxyapatite, and pyrophosphate, a physiochemical inhibitor of mineralization. Here, we provide a detailed analysis of a zebrafish mutant, dragonfish (dgf), which is mutant for ectonucleoside pyrophosphatase/phosphodiesterase 1 (Enpp1), a protein that is crucial for supplying extracellular pyrophosphate. Generalized arterial calcification of infancy (GACI) is a fatal human disease, and the majority of cases are thought to be caused by mutations in ENPP1. Furthermore, some cases of pseudoxanthoma elasticum (PXE) have recently been linked to ENPP1. Similar to humans, we show here that zebrafish enpp1 mutants can develop ectopic calcifications in a variety of soft tissues - most notably in the skin, cartilage elements, the heart, intracranial space and the notochord sheet. Using transgenic reporter lines, we demonstrate that ectopic mineralizations in these tissues occur independently of the expression of typical osteoblast or cartilage markers. Intriguingly, we detect cells expressing the osteoclast markers Trap and CathepsinK at sites of ectopic calcification at time points when osteoclasts are not yet present in wild-type siblings. Treatment with the bisphosphonate etidronate rescues aspects of the dgf phenotype, and we detected deregulated expression of genes that are involved in phosphate homeostasis and mineralization, such as fgf23, npt2a, entpd5 and spp1 (also known as osteopontin). Employing a UAS-GalFF approach, we show that forced expression of enpp1 in blood vessels or the floorplate of mutant embryos is sufficient to rescue the notochord mineralization phenotype. This indicates that enpp1 can exert its function in tissues that are remote from its site of expression.

Functionalization of biomaterials with small osteoinductive moieties

Human mesenchymal stem cells (MSCs) are currently recognized as a powerful cell source for regenerative medicine, notably for their capacity to differentiate into multiple cell types. The combination of MSCs with biomaterials functionalized with instructive cues can be used as a strategy to direct specific lineage commitment, and can thus improve the therapeutic efficacy of these cells. In terms of biomaterial design, one common approach is the functionalization of materials with ligands capable of directly binding to cell receptors and trigger specific differentiation signaling pathways. Other strategies focus on the use of moieties that have an indirect effect, acting, for example, as sequesters of bioactive ligands present in the extracellular milieu that, in turn, will interact with cells. Compared with complex biomolecules, the use of simple compounds, such as chemical moieties and peptides, and other small molecules can be advantageous by leading to less expensive and easily tunable biomaterial formulations. This review describes different strategies that have been used to promote substrate-mediated guidance of osteogenic differentiation of immature osteoblasts, osteoprogenitors and MSCs, through chemically conjugated small moieties, both in two- and three-dimensional set-ups. In each case, the selected moiety, the coupling strategy and the main findings of the study were highlighted. The latest advances and future perspectives in the field are also discussed.

Expression and clinical significance of osteopontin in calcified breast tissue

Osteopontin (OPN) is an integrin-binding protein, believed to be involved in a variety of physiological cellular functions. The physiology of OPN is best documented in the bone where this secreted adhesive glycoprotein appears to be involved in osteoblast differentiation and bone formation. In our study, we used semi-quantitative RT-PCR of osteopontin in calcification tissue of breast to detect breast cancer metastasis. The obtained data indicate that the expression of osteopontin is related to calcification tissue of breast, and possibly with the incidence of breast cancer. The expression strength of OPN by RT-PCR detection was related to the degree of malignancy of breast lesions, suggesting a close relationship between OPN and breast calcification tissue. The results revealed that expression of OPN mRNA is related to calcification of breast cancer tissue and to the development of breast cancer. Determination of OPN mRNA expression can be expected to be a guide to clinical therapy and prediction of the prognosis of breast cancer patients.

The effect of purmorphamine and sirolimus on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells

Small molecules have been introduced as less expensive biologically active compounds that can regulate different developmental phenomena. Purmorphamine and sirolimus are two small molecules that, according to some studies, possess certain osteomodulatory effects. This study was set out to highlight the appropriate dose and response time of these small molecules on enhancement of osteogenesis in human bone marrow-derived mesenchymal stem cells from early to mid and late stages of differentiation. Alkaline phosphatase activity, matrix mineralization and expression of osteoblast genes were quantitatively assessed in vitro. For the in vivo study, we transplanted stem cell-based constructs subcutaneously into rats, and treated them daily with the most promising doses of the small molecule. The constructs were analyzed by real-time PCR and histological staining. Our results showed that Sirolimus reduced osteogenic differentiation of mesenchymal stem cells by decreasing alkaline phosphatase activity at dose of 100nM after 14 days and mineralization of the matrix at 14 and 21 days post-induction. Purmorphamine induced up-regulation of alkaline phosphatase activity and expression of RUNX-2 at day 14. Up-regulation of osteocalcin was detected at the 3 and 5μM doses of purmorphamine on day 14 post-induction. Matrix mineralization remained unchanged in the presence or absence of purmorphamine. This dose of small molecule also accelerated expression of Alkaline phosphatase transcripts in vivo. In conclusion, sirolimus had an inhibitory effect on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells; while purmorphamine, particularly at a dose of 3μM, showed a promotive effect in vitro and in vivo.

Loss of MMP-2 in murine osteoblasts upregulates osteopontin and bone sialoprotein expression in a circuit regulating bone homeostasis

Multicentric osteolysis with arthropathy (MOA; MIM 605156) is an inherited osteolyses and arthritis syndrome resulting from loss of matrix metalloproteinase 2 (MMP-2). We recently demonstrated that Mmp2^–/– mice represent a unique model for the study of the human disease, sharing many features of the human syndrome including skeletal dysplasia and defects in osteoblast behavior. We therefore sought to explore the secondary molecular effects of MMP-2 loss, which coexist with the underlying skeletal and osteoblast phenotypes. We used quantitative real-time RT-PCR (qRT-PCR) to measure osteoblast-related gene expression through ex vivo osteoblast differentiation of bone marrow stromal cells (BMSC) from Mmp2^−/− and Mmp2^+/+ mice. We used western blot to measure osteopontin (OPN) serum levels and immunohistochemical staining to examine bone expression. MMP-2 expression was inhibited in SaOS2 cells using siRNA, and decreased MMP-2 expression at both RNA and protein levels was confirmed by qRT-PCR and western blot, respectively. Mmp2^−/− BMSC induced to differentiate into osteoblasts were shown to significantly upregulate OPN and bone sialoprotein (BSP) expression levels compared with controls. Transcriptional upregulation was maintained in vivo, as demonstrated by increased levels of OPN in serum and bone in Mmp2^−/− mice. These effects are generalizable because siRNA-mediated inhibition in cultured cells also upregulated OPN and BSP. OPN and BSP are known to affect MMP-2 expression and activity but have not previously been shown to be regulated by MMP-2. Identification of this newly defined circuitry provides insight into the potential molecular landscape underlying the MOA phenotype and highlights a pathway that might play a role in normal bone homeostasis.

In vitro and in vivo characteristics of stem cells derived from the periodontal ligament of human deciduous and permanent teeth

In many studies, adult stem cells have been found in human periodontal ligament (PDL), but in most cases they were found in the permanent teeth. The aim of the present study was to characterize stem cells from the PDL of deciduous teeth (dPDLSCs) and compare them with those from the PDL of permanent teeth (pPDLSCs). Stem cell markers were examined by a flow cytometric analysis. The results of in vitro differentiation into adipogenic and osteogenic lineages were analyzed by histochemical staining and quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results of in vivo transplantation were analyzed by histological staining, immunohistochemical staining, and quantitative RT-PCR. There were no significant differences in the proliferation rate, cell cycle distribution, expressions of stem cell markers such as Stro-1 and CD146, or in vitro differentiation. The pPDLSC transplants made more typical cementum/PDL-like tissues and expressed more cementum/PDL-related genes (CP23 and collagen XII) than did the dPDLSC transplants. Together, these results suggest that pPDLSCs are better candidates for use in reconstructing periodontium.

Localization of osteopontin and osterix in periodontal tissue during orthodontic tooth movement in rats

OBJECTIVE

To evaluate the localization of osteopontin (OPN) and osterix in periodontal tissue during experimental tooth movement with heavy force in rats.

MATERIALS AND METHODS

Nickel-titanium closed-coil springs were used to create a 100 g mesial force to the maxillary first molars. On days 3, 7, 10, and 14 after force application, histological changes in periodontium were examined by immunohistochemistry using proliferating cell nuclear antigen (PCNA), OPN, and osterix.

RESULTS

PCNA-positive cells were found close to the alveolar bone and cementum on both sides. OPN-positive cells were observed along the cementing line of the cementum and bone on both sides and also were visible along with newly formed fibers in the periodontal ligament on the tension side. Osterix-positive cells were strongly detected on the surface of the alveolar bone and cementum on both sides.

CONCLUSIONS

During tooth movement, periodontal remodeling occurs on both sides. These results indicate that OPN and osterix may play an important role of differentiation and osteoblasts and cementoblasts matrix formation during periodontal tissue remodeling.

Biomineralization of bone: a fresh view of the roles of non-collagenous proteins

The impact of genetics has dramatically affected our understanding of the functions of non-collagenous proteins. Specifically, mutations and knockouts have defined their cellular spectrum of actions. However, the biochemical mechanisms mediated by non-collagenous proteins in biomineralization remain elusive. It is likely that this understanding will require more focused functional testing at the protein, cell, and tissue level. Although initially viewed as rather redundant and static acidic calcium binding proteins, it is now clear that non-collagenous proteins in mineralizing tissues represent diverse entities capable of forming multiple protein-protein interactions which act in positive and negative ways to regulate the process of bone mineralization. Several new examples from the author's laboratory are provided which illustrate this theme including an apparent activating effect of hydroxyapatite crystals on metalloproteinases. This review emphasizes the view that secreted non-collagenous proteins in mineralizing bone actively participate in the mineralization process and ultimately control where and how much mineral crystal is deposited, as well as determining the quality and biomechanical properties of the mineralized matrix produced.

Periodontal tissue engineering after tooth replantation

BACKGROUND

Blood-derived products, platelet-poor plasma (PPP) and platelet-rich plasma (PRP), constitute an approach in the enhancement of tissue healing. PRP has also been used as a scaffold for bone marrow stem cells in tissue engineering. This study evaluates the effect of PPP, calcium chloride-activated PRP (PRP/Ca), calcium chloride- and thrombin-activated PRP (PRP/Thr/Ca), and bone marrow mononuclear cells and PRP/Ca (BMMCs/PRP/Ca) on the healing of replanted dog teeth.

METHODS

After 30 minutes of extraction, teeth were replanted with 1) no material (control); 2) PPP; 3) PRP/Ca; 4) PRP/Thr/Ca; or 5) BMMCs/PRP/Ca. Histologic, histomorphometric, and immunohistochemical analysis was assessed 120 days after replantation. Data from histomorphometric analysis were analyzed statistically (analysis of variance, Tukey; P <0.05). Quantitative immunohistochemical analysis was analyzed by Kruskal-Wallis and Dunn post hoc test (P <0.05).

RESULTS

Flow cytometry analysis showed 55.98% of CD34(+) and 32.67% of CD90/Thy-1 for BMMCs sample. BMMCs/PRP/Ca presented the largest areas of replacement resorption characterized by osseous ingrowth into cementum (P <0.05), with intense immunomarcation for tartrate-resistant acid phosphatase. The PRP/Ca group also showed areas of replacement resorption with significant immunomarcation for osteopontin. PRP/Thr/Ca presented no replacement resorption. PPP showed areas of inflammatory resorption, with immunomarcation for tartrate-resistant acid phosphatase.

CONCLUSIONS

The results suggest that platelets activated with thrombin play an important role in the healing of tissues after tooth replantation. Additional studies are necessary to test other materials, because PRP/Ca did not present an appropriate scaffold for undifferentiated cells in the treatment of avulsed teeth.

Low-level vibrations retain bone marrow's osteogenic potential and augment recovery of trabecular bone during reambulation

Mechanical disuse will bias bone marrow stromal cells towards adipogenesis, ultimately compromising the regenerative capacity of the stem cell pool and impeding the rapid and full recovery of bone morphology. Here, it was tested whether brief daily exposure to high-frequency, low-magnitude vibrations can preserve the marrow environment during disuse and enhance the initiation of tissue recovery upon reambulation. Male C57BL/6J mice were subjected to hindlimb unloading (HU, n = 24), HU interrupted by weight-bearing for 15 min/d (HU+SHAM, n = 24), HU interrupted by low-level whole body vibrations (0.2 g, 90 Hz) for 15 min/d (HU+VIB, n = 24), or served as age-matched controls (AC, n = 24). Following 3 w of disuse, half of the mice in each group were released for 3 w of reambulation (RA), while the others were sacrificed. RA+VIB mice continued to receive vibrations for 15 min/d while RA+SHAM continued to receive sham loading. After disuse, HU+VIB mice had a 30% greater osteogenic marrow stromal cell population, 30% smaller osteoclast surface, 76% greater osteoblast surface but similar trabecular bone volume fraction compared to HU. After 3 w of reambulation, trabecular bone of RA+VIB mice had a 30% greater bone volume fraction, 51% greater marrow osteoprogenitor population, 83% greater osteoblast surfaces, 59% greater bone formation rates, and a 235% greater ratio of bone lining osteoblasts to marrow adipocytes than RA mice. A subsequent experiment indicated that receiving the mechanical intervention only during disuse, rather than only during reambulation, was more effective in altering trabecular morphology. These data indicate that the osteogenic potential of bone marrow cells is retained by low-magnitude vibrations during disuse, an attribute which may have contributed to an enhanced recovery of bone morphology during reambulation.

An ex vivo rodent mandible culture model for bone repair

To understand fully cellular mechanisms during bone tissue repair and engineering, there is a need to develop reproducible three-dimensional organotypic culture models, whereby cells in their natural extracellular matrix can be manipulated. Limitations in current model systems do not allow for this integrated approach. This study aimed to develop and validate an ex vivo fractured rat mandible model, to investigate specific molecular and cellular processes involved in bone repair. Slices of mandible from 28-day-old male Wistar rats were cultured in Trowel-type cultures at the liquid-gas interface for up to 21 days. Maintenance of cell and tissue architecture and viability was shown within fractured mandible slices during all culture periods. Autoradiographic studies demonstrated that resident cells were actively synthesizing and secreting proteins, and cells of the osteoblast lineage were shown to survive throughout the culture periods. The model was responsive to exogenously added transforming growth factor-β1, with observed increases in cellular migration/proliferation and expression of bone matrix proteins. The ex vivo mandible model developed within this study may represent an ideal system for investigating specific processes of bone repair, as well as a promising alternative to in vivo testing of novel clinical therapeutics.

Dynamics of Bio-Oss Collagen incorporation in fresh extraction wounds: an experimental study in the dog

AIM

The objective of this experiment was to analyze processes involved in the incorporation of Bio-Oss Collagen in host tissue during healing following tooth extraction and grafting.

METHODS

Five beagle dogs were used. Four premolars in the mandible ((3)P(3), (4)P(4)) were hemi-sected, the distal roots were removed and the fresh extraction socket filled with Bio-Oss Collagen. The mucosa was mobilized and the extraction site was closed with interrupted sutures. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2 and 4 weeks of healing could be obtained. The dogs were euthanized and perfused with a fixative. Each experimental site, including the distal socket area, was dissected. The sites were decalcified in EDTA, and serial sections representing the central part of the socket were prepared in the mesio-distal plane and parallel with the long axis of the extraction socket. Sections were stained in hematoxylin and eosin and were used for the overall characteristics of the tissues in the extraction socket. In specimens representing 1, 2 and 4 weeks of healing the various tissue elements were assessed using a morphometric point counting procedure. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells positive for tartrate-resistant acid phosphatase activity (TRAP), alkaline phosphatase and osteopontin were identified.

RESULTS

The biomaterial was first trapped in the fibrin network of the coagulum. Neutrophilic leukocytes [polymorphonuclear (PMN) cells] migrated to the surface of the foreign particles. In a second phase the PMN cells were replaced by multinuclear TRAP-positive cells (osteoclasts). The osteoclasts apparently removed material from the surface of the xenogeneic graft. When after 1-2 weeks the osteoclasts disappeared from the Bio-Oss granules they were followed by osteoblasts that laid down bone mineral in the collagen bundles of the provisional matrix. In this third phase the Bio-Oss particles became osseointegrated.

CONCLUSIONS

It was demonstrated that the incorporation of Bio-Oss in the tissue that formed in an extraction wound involved a series of different processes.

Androstenediol reverses steroid-inhibited wound healing

It is well recognized that stress of any nature will cause a delay in the wound healing response. This delayed healing response appears closely associated with immune regulators. In this study, CD-1 mice were injected with a long acting form of methyl prednisolone to cause a steroid-induced immune suppression. After 24 hours, two 6-mm full thickness wounds were placed on the animals' backs and one group of animals received the immune-regulating hormone, androstenediol. Wound contraction was quantified by planimetry for the subsequent 14 days. Animals that were stressed with methyl prednisolone but receiving androstenediol contracted their open wounds at faster rates compared with methyl prednisolone-stressed animals treated with the vehicle alone. These findings suggest that restoration of immune regulation by androstenediol can reverse the delayed open wound contraction secondary to steroid stress.

Differential gene expression in the perichondrium and cartilage of the neonatal mouse temporomandibular joint

Our goal was to discover genes differentially expressed in the perichondrium (PC) of the mandibular condylar cartilage (MCC) that might enhance regenerative medicine or orthopaedic therapies directed at the tissues of the temporomandibular joint. We used targeted gene arrays (osteogenesis, stem cell) to identify genes preferentially expressed in the PC and the cartilaginous (C) portions of the MCC in 2-day-old mice. Genes with higher expression in the PC sample related to growth factor ligand-receptor interactions [FGF-13 (6.4x), FGF-18 (4x), NCAM (2x); PGDF receptors, transforming growth factor (TGF)-beta and IGF-1], the Notch isoforms (especially Notch 3 and 4) and their ligands or structural proteins/proteoglycans [collagen XIV (21x), collagen XVIII (4x), decorin (2.5x)]. Genes with higher expression in the C sample consisted mostly of known cartilage-specific genes [aggrecan (11x), procollagens X (33x), XI (14x), IX (4.5x), Sox 9 (4.4x) and Indian hedgehog (6.7x)]. However, the functional or structural roles of several genes that were expressed at higher levels in the PC sample are unclear [myogenic factor (Myf) 9 (9x), tooth-related genes such as tuftelin (2.5x) and dentin sialophosphoprotein (1.6x), VEGF-B (2x) and its receptors (3-4x) and sclerostin (1.7x)]. FGF, Notch and TGF-beta signalling may be important regulators of MCC proliferation and differentiation; the relatively high expression of genes such as Myf6 and VEGF-B and its receptors suggests a degree of unsuspected plasticity in PC cells.