Differential effects between the loss of MMP-2 and MMP-9 on structural and tissue-level properties of bone

A Meta-Analysis Study to Define Variations in Murine Long Bone Biomechanical Testing

A systematic literature search and meta-analysis were performed to evaluate the variability in biomechanical testing of murine long bones, specifically focused on point-bending tests of mice femora. Due to the lack of standardized protocols for these tests, the assessment quantifies the heterogeneity in reported mechanical properties across existing literature. This study followed preferred reporting items for systematic reviews and meta-analyses (PRISMA) and strengthening the reporting of observational studies in epidemiology (STROBE) guidelines to search publicly available databases for relevant studies. After title and abstract screening, full-text reviews identified 73 articles meeting the inclusion criteria. Data was extracted from these studies, including stiffness, maximum load, modulus, and ultimate stress values for both three-point and four-point bending tests. The data were analyzed through ANOVA and metaregression to assess variability caused by age, sex, and genetic strain. The reviewers also assessed the quality of the included studies. The meta-analysis revealed significant heterogeneity in reported mechanical properties, with I2 values ranging from 72% to 100% in the three point-bend tests of pooled genetic strains. This heterogeneity persisted even after accounting for age, sex, and genetic strain differences. The review concludes that nonstandardized testing setups are the likely major source of the observed variability in reported data more than the population characteristics of the mice, highlighting the need for more consistent testing methodologies in future studies.

Network pharmacology analysis uncovers the mechanism of Shudihuang-Shanzhuyu herb pair in prevention and treatment of diabetic osteoporosis via PI3K/AKT pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic osteoporosis (DOP) is a complication of diabetes characterized by reduced bone mass and increased fracture risk. Shudihuang (Rehmanniae Radix Praeparata, RR) and Shanzhuyu (Corni Fructus, CF) form a classical herb pair known as RR-CF in traditional Chinese medicine (TCM) for nourishing Yin and tonifying the kidney, and have long been used for the treatment of diabetes and OP in TCM clinical practise. However, the potential mechanism underlying the preventive and therapeutic effects of RR-CF on DOP has not been clarified.

AIM OF THE STUDY

This study aimed to explore the protective effects of RR-CF on bone loss caused by diabetes and elucidate the underlying action mechanism.

METHODS

The chemical constituents in RR-CF were detected using UPLC-Q-Exactive-MS. Type 1 diabetes mellitus (T1DM) was induced in rats by injecting streptozotocin, followed by administration of RR-CF extracts for 10 weeks. Bone mineral density, morphometric bone parameters, and serum and urine biochemical markers were analyzed using Micro-CT and ELISA kits. An in vitro osteoblastic injury model was constructed by subjecting MC3T3-E1 cells to high glucose and used to evaluate the effects of the RR-CF on osteoblastic bone formation. The anti-DOP mechanism of RR-CF was explored by network pharmacologic analysis and then verified in osteoblasts damaged by high glucose.

RESULTS

A total of 56 compounds were identified in RR-CF. Treatment with RR-CF extracts improved the bone microstructure and mineral density in the T1DM rats, and decreased the level of urine deoxypyridinoline and serum carboxyl terminal peptide of type I procollagen. The network pharmacology analysis identified cornuside, hydroxygenkwanin, acteoside, catalpol and echinacoside as the potential active components of RR-CF against DOP by interacting with the key node genes such as AKT1, EGFR, TNF, MMP9 and HSP90α. Further GO and KEGG enrichment analysis suggested that the therapeutic effects of RR, CF and RR-CF seemed to be related to the regulation of hormones, inflammation and metabolism, as well as signaling transductions of PI3K-AKT, IL-17, TNF, MAPK and estrogen signaling pathways. RR-CF promoted osteoblast differentiation and bone formation in the MC3T3-E1 cells by regulating PI3K-AKT signaling pathway.

CONCLUSION

RR-CF herb pair inhibits bone loss caused by high glucose by regulating the PI3K-AKT signaling pathways.

Resident synovial macrophages in synovial fluid: Implications for immunoregulation

Resident synovial macrophages (RSMs) are anti-inflammatory, self-renewing macrophages that provide physical immune sequestration of the joint space from the peripheral immune system. Increased permeability of this structure is associated with peripheral immune cells in the synovial fluid (SF). Direct measures of synovial barrier integrity are possible with tissue histology, but after barrier breakdown, if these cells perpetuate or initiate chronic inflammation in SF remains unknown. We sought to identify RSM in human SF as an indirect measure of synovial barrier integrity. To validate findings, we created a novel ex vivo explant model using human synovium. scRNA-seq revealed these SF RSMs upregulated pro-fibrotic and pro-osteoclastic pathways in inflammatory arthritis, but not septic arthritis. Increased frequencies of RSMs in SF was associated with increased sRANKL regardless of underlying pathology. These findings suggest the frequency of RSMs in SF may correlate with synovial barrier damage and in turn, potential damage to joint structures.

Mapping the spatial atlas of the human bone tissue integrating spatial and single-cell transcriptomics

Bone is a multifaceted tissue requiring orchestrated interplays of diverse cells within specialized microenvironments. Although significant progress has been made in understanding cellular and molecular mechanisms of component cells of bone, revealing their spatial organization and interactions in native bone tissue microenvironment is crucial for advancing precision medicine, as they govern fundamental signaling pathways and functional dependencies among various bone cells. In this study, we present the first integrative high-resolution map of human bone and bone marrow, using spatial and single-cell transcriptomics profiling from femoral tissue. This multi-modal approach discovered a novel bone formation-specialized niche enriched with osteoblastic lineage cells and fibroblasts and unveiled critical cell-cell communications and co-localization patterns between osteoblastic lineage cells and other cells. Furthermore, we discovered a novel spatial gradient of cellular composition, gene expression and signaling pathway activities radiating from the trabecular bone. This comprehensive atlas delineates the intricate bone cellular architecture and illuminates key molecular processes and dependencies among cells that coordinate bone metabolism. In sum, our study provides an essential reference for the field of bone biology and lays the foundation for advanced mechanistic studies and precision medicine approaches in bone-related disorders.

Changes in Angiogenesis and Bone Turnover Markers in Patients with Gaucher Disease Developing Osteonecrosis

Background/Objectives: Patients with Gaucher disease have a high risk of bone disease, with osteonecrosis representing the most debilitating complication. The pathogenesis of osteonecrosis has not been fully elucidated yet, and there is an unmet need for predictive biomarkers of bone complications. We aimed to assess the utility of angiogenesis and bone turnover biomarkers as predictors of osteonecrosis in Gaucher disease. Methods: Angiogenesis and bone turnover biomarkers were measured in 146 Gaucher disease patients (70M:76F, median age 49.5 [IQR 36.7 to 61]) with/without osteonecrosis enrolled in the UK-based registry GAUCHERITE [enrolment 2015-2017]. Receiver-operating characteristic curve analysis was used to compare the osteonecrosis predictive value of angiogenesis and bone turnover biomarkers and determine the optimal cut-off values for each biomarker. Results: Sixty-two patients had osteonecrosis before study enrolment, 11 had osteonecrosis during follow-up, and 73 remained osteonecrosis-free. Patients with osteonecrosis showed increased osteopontin and matrix metalloproteinase (MMP)-2 levels and decreased MMP-9 and vascular endothelial growth factor (VEGF)-C compared with those free from osteonecrosis. MMP-9 predicted future osteonecrosis with higher sensitivity and specificity (area under the receiver operating characteristic curve [AUC] 0.84 [95% CI 0.84-0.99]; sensitivity/specificity 82%/75%; cutoff value ≤ 72,420 pg/mL) than osteopontin, MMP-2 and VEGF-C when taken alone. The combination of MMP-9 and VEGF-C further increased the discriminating accuracy. Conclusions: The osteopontin-MMPs-VEGF axis is dysregulated in Gaucher disease patients with osteonecrosis. The combination of MMP-9 and VEGF-C circulating levels may serve to identify Gaucher disease patients at risk of osteonecrosis.

Potential molecular targets for the pharmacologic management of non-traumatic osteonecrosis

INTRODUCTION

Non-traumatic osteonecrosis is a debilitating condition marked by bone death, primarily due to reduced blood supply. Currently, no effective pharmacologic intervention is available to manage this condition effectively.

AREAS COVERED

Lipid metabolic disorders, chronic inflammation, vascular dysfunction, coagulopathy, and impaired bone homeostasis are suggested as the key pathogenic mechanisms involved in the development of non-traumatic osteonecrosis. Targeting any of these dysfunctions offers a potential avenue for pharmacologic intervention. However, the potential molecular targets for pharmacologic treatment of non-traumatic osteonecrosis remain underexplored. In this study, we reviewed available databases to compile a comprehensive set of pathogenic mechanisms and corresponding therapeutic targets for non-traumatic osteonecrosis.

EXPERT OPINION

Evidence suggests that a single pathogenic mechanism cannot fully explain the development of osteonecrosis, supporting the adoption of a multi-pathogenic theory. This theory implies that effective management of non-traumatic osteonecrosis requires targeting multiple pathogenic mechanisms simultaneously. Moreover, the same pathogenic mechanisms are unlikely to explain osteonecrosis development in patients with different etiologies. Consequently, a one-size-fits-all approach to medication is unlikely to be effective across all types of non-traumatic osteonecrosis. Future research should, therefore, focus on developing multi-target pharmacologic treatments tailored to the specific etiology of non-traumatic osteonecrosis.

Bioinformatics Study on Mechanism of Postnatal Development of Craniofacial Bone

OBJECTIVE

The postnatal development of craniofacial bone plays a crucial role in shaping the overall structure and functionality of the skull and face. Understanding the underlying mechanisms of this intricate process is essential for both clinical and research purposes. In this study, the authors conducted a bioinformatics analysis using the Gene Expression Omnibus database to investigate the molecular pathways and regulatory networks involved in the postnatal development of craniofacial bone.

METHODS

In this study, the online Gene Expression Omnibus microarray expression profiling data set GSE27976 was used to identify differentially expressed genes (DEGs) in different age groups. Protein-Protein Interaction network analyses, functional enrichment, and hub genes analysis were performed. The differences in immune infiltration and microenvironment among different types of cells were also analyzed.

RESULTS

In total, 523 DEGs, including 287 upregulated and 236 downregulated genes, were identified. GO and KEGG analysis showed that the DEGs were significantly enriched in multiple signaling pathways, such as skeletal system morphogenesis, osteoblast differentiation, and stem cell differentiation. Immune infiltration and microenvironment characteristics analysis showed that there were significant differences in fibroblasts, mesenchymal stem cell, osteoblast, stroma score, and microenvironment score between the two groups. Five hub genes, including IGF1, IL1B, ICAM1, MMP2 , and brain-derived neurotrophic factor, were filled out.

CONCLUSION

The findings of this study showed a significant shift in gene expression towards osteogenesis during the first 12 months after birth. These findings emphasize the critical role of the postnatal period in craniofacial bone development and provide valuable insights into the molecular mechanisms underlying this process.

Differential Gene Expression Involved in Bone Turnover of Mice Expressing Constitutively Active TGFβ Receptor Type I

Transforming growth factor beta (TGF-β) is ubiquitously found in bone and plays a key role in bone turnover. Mice expressing constitutively active TGF-β receptor type I (Mx1;TβRICA mice) are osteopenic. Here, we identified the candidate genes involved in bone turnover in Mx1;TβRICA mice using RNA sequencing analysis. A total of 285 genes, including 87 upregulated and 198 downregulated genes, were differentially expressed. According to the KEGG analysis, some genes were involved in osteoclast differentiation (Fcgr4, Lilrb4a), B cell receptor signaling (Cd72, Lilrb4a), and neutrophil extracellular trap formation (Hdac7, Padi4). Lilrb4 is related to osteoclast inhibition protein, whereas Hdac7 is a Runx2 corepressor that regulates osteoblast differentiation. Silencing Lilrb4 increased the number of osteoclasts and osteoclast marker genes. The knocking down of Hdac7 increased alkaline phosphatase activity, mineralization, and osteoblast marker genes. Therefore, our present study may provide an innovative idea for potential therapeutic targets and pathways in TβRI-associated bone loss.

Identification of gravity-responsive serum proteins in spaceflight mice using a quantitative proteomic approach with data-independent acquisition mass spectrometry

Physical inactivity associated with gravity unloading, such as microgravity during spaceflight and hindlimb unloading (HU), can cause various physiological changes. In this study, we attempted to identify serum proteins whose levels fluctuated in response to gravity unloading. First, we quantitatively assessed changes in the serum proteome profiles of spaceflight mice using mass spectrometry with data-independent acquisition. The serum levels of several proteins involved in the responses to estrogen and glucocorticoid, blood vessel maturation, osteoblast differentiation, and ossification were changed by microgravity exposure. Furthermore, a collective evaluation of serum proteomic data from spaceflight and HU mice identified 30 serum proteins, including Mmp2, Igfbp2, Tnc, Cdh5, and Pmel, whose levels varied to a similar extent in both gravity unloading models. These changes in serum levels could be involved in the physiological changes induced by gravity unloading. A collective evaluation of serum, femur, and soleus muscle proteome data of spaceflight mice also showed 24 serum proteins, including Igfbp5, Igfbp3, and Postn, whose levels could be associated with biological changes induced by microgravity. This study examined serum proteome profiles in response to gravity unloading, and may help deepen our understanding of microgravity adaptation mechanisms during prolonged spaceflight missions.

Immunohistochemical expression of SPARC in odontogenic keratocysts: a comparative study with other odontogenic cysts

BACKGROUND

Secreted protein acidic and rich in cysteine (SPARC) has been shown to modulate aggressive behavior in several benign and malignant tumors. Little is known about SPARC expression in odontogenic keratocyst (OKC), an odontogenic cyst with an aggressive nature. To the best of our knowledge, only one study has been investigated the expression of this protein in OKCs. This study aimed to characterize SPARC expression in OKCs. Additionally, to determine whether SPARC is associated with aggressive behavior in OKCs, SPARC expression in OKCs was compared with radicular cysts (RCs), dentigerous cysts (DCs) and calcifying odontogenic cysts (COCs). These odontogenic cysts showed no or less aggressive behavior.

METHODS

SPARC expression was evaluated in 38 OKCs, 39 RCs, 35 DCs and 14 COCs using immunohistochemistry. The percentages of positive cells and the intensities of immunostaining in the epithelial lining and the cystic wall were evaluated and scored.

RESULTS

Generally, OKCs showed similar staining patterns to RCs, DCs and COCs. In the epithelial lining, SPARC was not detected, except for ghost cells in all COCs. In the cystic wall, the majority of positive cells were fibroblasts. Compared between 4 groups of odontogenic cysts, SPARC expression in OKCs was significantly higher than those of RCs (P < 0.001), DCs (P < 0.001) and COCs (P = 0.001).

CONCLUSIONS

A significant increase of SPARC expression in OKCs compared with RCs, DCs and COCs suggests that SPARC may play a role in the aggressive behavior of OKCs.

Heterotypic Cell Culture from Mouse Bone Marrow under Simulated Microgravity: Lessons for Stromal Lineage Functions

Muscle and skeleton structures are considered most susceptible to negative factors of spaceflights, namely microgravity. Three-dimensional clinorotation is a ground-based simulation of microgravity. It provides an opportunity to elucidate the effects of microgravity at the cellular level. The extracellular matrix (ECM) content, transcriptional profiles of genes encoding ECM and remodelling molecules, and secretory profiles were investigated in a heterotypic primary culture of bone marrow cells after 14 days of 3D clinorotation. Simulated microgravity negatively affected stromal lineage cells, responsible for bone tissue formation. This was evidenced by the reduced ECM volume and stromal cell numbers, including multipotent mesenchymal stromal cells (MSCs). ECM genes encoding proteins responsible for matrix stiffness and cell-ECM contacts were downregulated. In a heterotypic population of bone marrow cells, the upregulation of genes encoding ECM degrading molecules and the formation of a paracrine profile that can stimulate ECM degradation, may be mechanisms of osteodegenerative events that develop in real spaceflight.

Protein Ca2+-Sites Prone to Sr2+ Substitution: Implications for Strontium Therapy

Strontium (Sr), an alkali metal with properties similar to calcium, in the form of soluble salts is used to treat osteoporosis. Despite the information accumulated on the role of Sr²⁺ as a Ca²⁺ mimetic in biology and medicine, there is no systematic study of how the outcome of the competition between the two dications depends on the physicochemical properties of (i) the metal ions, (ii) the first- and second-shell ligands, and (iii) the protein matrix. Specifically, the key features of a Ca²⁺-binding protein that enable Sr²⁺ to displace Ca²⁺ remain unclear. To address this, we studied the competition between Ca²⁺ and Sr²⁺ in protein Ca²⁺-binding sites using density functional theory combined with the polarizable continuum model. Our findings indicate that Ca²⁺-sites with multiple strong charge-donating protein ligands, including one or more bidentately bound Asp^-/Glu^- that are relatively buried and rigid are protected against Sr²⁺ attack. On the other hand, Ca²⁺-sites crowded with multiple protein ligands may be prone to Sr²⁺ displacement if they are solvent-exposed and flexible enough so that an extra backbone ligand from the outer shell can bind to Sr²⁺. In addition, solvent-exposed Ca²⁺ sites with only a few weak charge-donating ligands that can rearrange to fit the strontium's coordination requirements are susceptible to Sr²⁺ displacement. We provide the physical basis of these results and discuss potential novel protein targets of therapeutic Sr²⁺.

Unearths IFNB1 immune infiltrates in SOP-related ossification of ligamentum flavum pathogenesis

Background

Ossification of ligamentum flavum (OLF) is a hidden, indolent disease condition with variable unexplained etiology and pathology. Growing evidences show a correlation between senile osteoporosis (SOP) and OLF, but the fundamental relationship between SOP and OLF remains unclear. Therefore, the purpose of this work is to investigate unique SOP-related genes and their potential functions in OLF.

Methods

Gene Expression Omnibus (GEO) database was utilized to gather the mRNA expression data (GSE106253) and then analyzed by R software. A variety of methods, including ssGSEA, machine learning (LASSO and SVM-RFE), GO and KEGG enrichment, PPI network, transcription factor enrichment analysis (TFEA), GSEA and xCells were employed to verified the critical genes and signaling pathways. Furthermore, ligamentum flavum cells were cultured and used in vitro to identify the expression of the core genes.

Results

The preliminary identification of 236 SODEGs revealed their involvement in BP pathways associated with ossification, inflammation, and immune response, including the TNF signaling pathway, PI3K/AKT signaling pathway and osteoclast differentiation. Four down-regulated genes (SERPINE1, SOCS3, AKT1, CCL2) and one up-regulated gene (IFNB1) were among the five hub SODEGs that were validated. Additionally, they were performed by ssGSEA and xCell to show the relationship of immune cells infiltrating in OLF. The most fundamental gene, IFNB1, which was only found in the classical ossification- and inflammation-related pathways, suggested that it may affect OLF via regulating the inflammatory response. In vitro experiment, we found that IFNB1 expression was dramatically higher in cells cocultured with osteogenic induction than in controls.

Conclusion

As far as we are concerned, this is the first observation using transcriptome data mining to reveal distinct SOP-related gene profiles between OLF and normal controls. Five hub SODEGs were ultimately found using bioinformatics algorithms and experimental verification. These genes may mediate intricate inflammatory/immune responses or signaling pathways in the pathogenesis of OLF, according to the thorough functional annotations. Since IFNB1 was discovered to be a key gene and was connected to numerous immune infiltrates in OLF, it is possible that IFNB1 expression has a substantial impact on the pathogenesis of OLF. Our research will give rise to new possibilities for potential therapeutics that target SOP reverent genes and immune-associated pathways in OLF.

MMP13-Overexpressing Mesenchymal Stem Cells Enhance Bone Tissue Formation in the Presence of Collagen Hydrogel

BACKGROUND

Matrix metalloproteinases (MMPs) are proteins involved in the repair and remodeling the extracellular matrix (ECM). MMP13 is essential for bone development and healing through the remodeling of type I collagen (COL1), the main component of the ECM in bone tissue. Mesenchymal stem cells (MSCs)-based cell therapy has been considered a promising approach for bone regeneration because of their osteogenic properties. However, the approaches using MSC to completely regenerate bone tissue have been limited. To overcome the limitation, genetic engineering of MSC could be a strategy for promoting regeneration efficacy.

METHODS

We performed in vitro and in vivo experiments using MMP13-overexpressing MSCs in the presence of COL1. To examine MMP13-overexpressing MSCs in vivo, we prepared a fibrin/COL1-based hydrogel to encapsulate MSCs and subcutaneously implanted gel-encapsulated MSCs in nude mice. We found that the osteogenic marker genes, ALP and RUNX2, were upregulated in MMP13-overexpressing MSCs through p38 phosphorylation. In addition, MMP13 overexpression in MSCs stimulated the expression of integrin α3, which is up-stream receptor of p38, and substantially increased osteogenic differentiation potential of MSCs. Bone tissue formation in MMP13-overexpressing MSCs was significantly higher than that in control MSCs. Taken together, our findings demonstrate that MMP13 is not only an essential factor for bone development and bone healing but also has a pivotal role in promoting osteogenic differentiation of MSCs to induce bone formation.

CONCLUSION

MSCs Genetically engineered to overexpress MMP13, which have a powerful potential to differentiate into the osteogenic cells, might be beneficial in bone disease therapy.

Temporomandibular Joint Ankylosis in a Girl Child: Immunochemical Evaluation of Tissue Material Obtained from Repeated Arthroplasty Surgeries

Temporomandibular joint ankylosis (TMJA) is a rare, but debilitating, condition that leads to TMJ joint hypomobility. Surgery is the mainstay for treatment, which is accompanied by rehabilitative and psychological support. Despite the advances in surgical techniques, the recurrence of TMJA post-surgery has been reported as a common complication. Therefore, it becomes essential to investigate and understand the histo-morpho-pathological processes governing these ankylotic changes. Given the lack of such studies in the literature, herein we present a case of a girl child who underwent primary surgery at the age of six years, followed by a second surgery at the age of twelve years. Ankylotic tissue samples collected during both surgeries were studied using various immunohistochemical markers for tissue remodeling, inflammation, antimicrobial activity, and transcriptional regulation. The expression of MMP-2 and -9 was downregulated in repeated surgery materials, whilst MMP-13 was rarely detected in both tissues. Strong MMP-8, TIMP-2, and TIMP-4 expressions were noted in both tissues, showing their anti-inflammatory and protective roles. Moderately strong expression of bFGF, FGFR-1, IL-1α, and TNF-α could indicate sustained tissue growth in the background of inflammation (wound healing). Interestingly, the expression of β-defensin-2 was found to be constant in both tissues, thereby indicating possible ECM remodeling and collagen breakdown. Finally, a moderate expression of RUNX-2, coupled with a low expression of WNT-1 and -3a, could indicate a slow and delayed bone regeneration process. Our results showcase the complex myriad of pathways that could be involved in the progression of TMJA and post-surgery healing processes. Immunopathological studies could aid in improving the diagnosis, treatment, and prognosis for patients affected with TMJA.

Instrumented nanoindentation in musculoskeletal research

Musculoskeletal tissues, such as bone, cartilage, and muscle, are natural composite materials that are constructed with a hierarchical structure ranging from the cell to tissue level. The component differences and structural complexity, together, require comprehensive multiscale mechanical characterization. In this review, we focus on nanoindentation testing, which is used for nanometer to sub-micrometer length scale mechanical characterization. In the following context, we will summarize studies of nanoindentation in musculoskeletal research, examine the critical factors that affect nanoindentation testing results, and briefly summarize other commonly used techniques that can be conjoined with nanoindentation for synchronized imaging and colocalized characterization.

New insights into the role of matrix metalloproteinase 3 (MMP3) in bone

The Matrix Metalloproteinases are important regulators of bone metabolism and can influence bone mass and bone remodeling. We investigate the role of Matrix Metalloproteinase 3 (MMP3) on bone in mice, by using Mmp3 knockout (Mmp3 KO) in the context of estrogen deficiency, and in human, by analyzing the association of promoter polymorphism with bone mineral density in postmenopausal women and with MMP3 expression. We presented evidence in this paper that Mmp3 KO significantly increases trabecular bone mass and trabecular number and does not affect cortical bone thickness. We also found that Mmp3 KO protects from the deleterious effects of ovariectomy on bone mineral density in mice by preventing deterioration of bone microarchitecture. The effect of Mmp3 KO does not involve bone formation parameters but instead acts by inhibition of bone resorption, leading to a reduced bone loss associated to ovariectomy. By studying a human cohort, we found that a polymorphism located in the promoter of the human MMP3 gene is associated with bone mineral density in postmenopausal women and found that MMP3 rs632478 promoter variants are associated with change in promoter activity in transfection experiments. In conclusion MMP3, although weakly expressed in bone cells, could be one of the important regulators of sex hormone action in bone and whose activity could be targeted for therapeutic applications such as in Osteoporosis.

Evaluation of the multiple tissue factors in bone of primary osteoplasty and rhinoplasty in patients affected by cleft lip palate

Clefts of the lip and/or palate (CLP) are visible disruptions of standard facial structure. The aim of our study was to determine a relative number and appearance of the tissue factors in bone of patients with CLP during first time plastic alveolar osteoplasty or rhinoplasty. Immunohistochemistry was performed with matrix metalloproteinase-8 (MMP-8), matrix metalloproteinase-9 (MMP-9), osteopontin (OPN), osteocalcin (OC), Runt-related transcription factor 2 (Runx2), beta-defensin-2 (βdef-2), beta-defensin-3 (βdef-3), interleukin-1 alpha (IL-1α), and interleukin-10 (IL-10). The bone formation was observed by Masson-trichrome (Masson) staining. For the quantification of structures, the semi-quantitative census method was used. Spearman rank order correlation coefficient and Mann-Whitney U test were used for the statistical analysis. A significantly higher number of OPN positive osteocytes was observed in the CLP group when compared to the control group (p=0.002). The number of OC positive osteocytes (p=0.000) and βdef-2 positive osteocytes (p=0.003) was significantly lower in the CLP group in comparison to the control group. Strong, positive correlations between IL-10 and OC (rs=0.608; p=0.002), IL-1α and MMP-9 (rs=0.666; p=0.000), OPN and MMP-8 (rs=0.620; p=0.002) were detected in the CLP group. A tendency for the increased appearance of MMP-8, MMP-9 positive osteocytes of the patients with CLP, suggests elevated tissue remodelling properties. Increased appearance of OPN positive osteocytes in bone of the patients with CLP shows increased bone homeostasis based on seriously decreased mineralization, which may be a possible compensatory reaction to decreased quality of postsurgical bone.

Parathyroid hormone (PTH) regulation of metabolic homeostasis: An old dog teaches us new tricks

BACKGROUND

Late in the nineteenth century, it was theorized that a circulating product produced by the parathyroid glands could negatively impact skeletal homeostasis. A century later, intermittent administration of that protein, namely parathyroid hormone (PTH), was approved by the FDA and EMA as the first anabolic agent to treat osteoporosis. Yet, several unanswered but important questions remain about the skeletal actions of PTH.

SCOPE OF REVIEW

Current research efforts have focused on improving the efficacy of PTH treatment by designing structural analogs and identifying other targets (e.g., the PTH or the calcium sensing receptor). A unique but only recently described aspect of PTH action is its regulation of cellular bioenergetics and metabolism, namely in bone and adipose tissue but also in other tissues. The current review aims to provide a brief background on PTH's previously described actions on bone and highlights how PTH regulates osteoblast bioenergetics, contributing to greater bone formation. It will also shed light on how PTH could alter metabolic homeostasis through its actions in other cells and tissues, thereby impacting the skeleton in a cell non-autonomous manner.

MAJOR CONCLUSIONS

PTH administration enhances bone formation by targeting the osteoblast through transcriptional changes in several pathways; the most prominent is via adenyl cyclase and PKA. PTH and its related protein, PTHrP, also induce glycolysis and fatty acid oxidation in bone cells and drive lipolysis and thermogenic programming in adipocytes; the latter may indirectly but positively influence skeletal metabolism. While much work remains, alterations in cellular metabolism may also provide a novel mechanism related to PTH's temporal actions. Thus, the bioenergetic impact of PTH can be considered another of the myriad anabolic effects of PTH on the skeleton. Just as importantly from a translational perspective, the non-skeletal metabolic effects may lead to a better understanding of whole-body homeostasis along with new and improved therapies to treat musculoskeletal conditions.

Mineralized Peyronie's plaque has a phenotypic resemblance to bone

Mineralized Peyronie's plaque (MPP) impairs penile function. The association, colocalization, and dynamic interplay between organic and inorganic constituents can provide insights into biomineralization of Peyronie's plaque. Human MPPs (n = 11) were surgically excised, and the organic and inorganic constituents were spatially mapped using multiple high-resolution imaging techniques. Multiscale image analyses resulted in spatial colocalization of elements within a highly porous material with heterogenous composition, lamellae, and osteocytic lacuna-like features with a morphological resemblance to bone. The lower (520 ± 179 mg/cc) and higher (1024 ± 155 mg/cc) mineral density regions were associated with higher (11%) and lower (7%) porosities in MPP. Energy dispersive X-ray and micro-X-ray fluorescent spectroscopic maps in the higher mineral density regions of MPP revealed higher counts of calcium (Ca) and phosphorus (P), and a Ca/P ratio of 1.48 ± 0.06 similar to bone. More importantly, higher counts of zinc (Zn) were localized at the interface between softer (more organic to inorganic ratio) and harder (less organic to inorganic ratio) tissue regions of MPP and adjacent softer matrix, indicating the involvement of Zn-related proteins and/or pathways in the formation of MPP. In particular, dentin matrix protein-1 (DMP-1) was colocalized in a matrix rich in proteoglycans and collagen that contained osteocytic lacuna-like features. This combined materials science and biochemical with correlative microspectroscopic approach provided insights into the plausible cellular and biochemical pathways that incite mineralization of an existing fibrous Peyronie's plaque. STATEMENT OF SIGNIFICANCE: Aberrant human penile mineralization is known as mineralized Peyronie's plaque (MPP) and often results in a loss of form and function. This study focuses on investigating the spatial association of matrix proteins and elemental composition of MPP by colocalizing calcium, phosphorus, and trace metal zinc with dentin matrix protein 1 (DMP-1), acidic proteoglycans, and fibrillar collagen along with the cellular components using high resolution correlative microspectroscopy techniques. Spatial maps provided insights into cellular and biochemical pathways that incite mineralization of fibrous Peyronie's plaque in humans.

Synthesis of scaffold-free, three dimensional, osteogenic constructs following culture of skeletal osteoprogenitor cells on glass surfaces

BACKGROUND

Efficient differentiation of stem cells into three-dimensional (3D) osteogenic construct is still an unmet challenge. These constructs can be crucial for patients with bone defects due to congenital or traumatic reasons. The modulation of cell fate and function as a consequence of interaction with the physical and chemical properties of materials is well known.

METHODS

The current study has examined the osteogenic differentiation potential of human skeletal populations following culture on glass surfaces, as a monolayer, or in glass tubes as a pellet culture. The 3D prosperities were assessed morphometrically and the differentiation was evaluated through molecular characterization as well as matrix formation.

RESULTS

Early temporal expression of alkaline phosphatase expression of skeletal populations was observed following culture on glass surfaces. Skeletal populations seeded on glass tubes, adhered as a monolayer to the tube base and subsequently formed 3D pellets at the air -media interface. The pellets cultured on glass displayed 4.9 ± 1.3 times the weight and 2.9 ± 0.1 the diameter of their counterpart cultured in plastic tubes and displayed enhanced production of osteogenic matrix proteins, such a collagen I and osteonectin. The size and weight of the pellets correlated with surface area in contrast to cell numbers seeded. Global DNA methylation level was decreased in pellets cultured on glass. In contrast, gene expression analysis confirmed upregulation extracellular matrix proteins and osteogenesis-related growth factors.

CONCLUSION

This simple approach to the culture of skeletal cells on glass tubes provides a scaffold-free, 3D construct platform for generating pellets enabling analysis and evaluation of tissue development and integration of multiple constructs with implications for tissue repair and regenerative application on scale-up.

Poor bone matrix quality: What can be done about it?

PURPOSE OF THE REVIEW

Bone's ability to withstand load resisting fracture and adapting to it highly depends on the quality of its matrix and its regulators. This review focuses on the contribution of bone quality to fracture resistance and possible therapeutic targets for skeletal fragility in aging and disease.

RECENT FINDINGS

The highly organized, hierarchical composite structure of bone extracellular matrix together with its (re)modeling mechanisms and microdamage dynamics determines its stiffness, strength, and toughness. Aging and disease affect the biological processes regulating bone quality, thus resulting in defective extracellular matrix and bone fragility. Targeted therapies are being developed to restore bone's mechanical integrity. However, their current limitations include low tissue selectivity and adverse side effects. Biological and mechanical insights into the mechanisms controlling bone quality, together with advances in drug delivery and studies in animal models, will accelerate the development and translation to clinical application of effective targeted-therapeutics for bone fragility.

Osteoclast-mediated bone resorption is controlled by a compensatory network of secreted and membrane-tethered metalloproteinases

Osteoclasts actively remodel both the mineral and proteinaceous components of bone during normal growth and development as well as pathologic states ranging from osteoporosis to bone metastasis. The cysteine proteinase cathepsin K confers osteoclasts with potent type I collagenolytic activity; however, cathepsin K-null mice, as well as cathepsin K-mutant humans, continue to remodel bone and degrade collagen by as-yet-undefined effectors. Here, we identify a cathepsin K-independent collagenolytic system in osteoclasts that is composed of a functionally redundant network of the secreted matrix metalloproteinase MMP9 and the membrane-anchored matrix metalloproteinase MMP14. Unexpectedly, whereas deleting either of the proteinases individually leaves bone resorption intact, dual targeting of Mmp9 and Mmp14 inhibited the resorptive activity of mouse osteoclasts in vitro and in vivo and human osteoclasts in vitro. In vivo, Mmp9/Mmp14 conditional double-knockout mice exhibited marked increases in bone density and displayed a highly protected status against either parathyroid hormone- or ovariectomy-induced pathologic bone loss. Together, these studies characterize a collagenolytic system operative in mouse and human osteoclasts and identify the MMP9/MMP14 axis as a potential target for therapeutic interventions for bone-wasting disease states.

Salivary molecules of bone remodeling and tissue repair after head and neck radiotherapy

Head and neck radiotherapy causes quantitative and qualitative changes in saliva. The objective of this case-control study was to evaluate the salivary biomarkers associated with bone remodeling and tissue repair in patients submitted to radiotherapy for head and neck cancer treatment, compared with non-irradiated individuals. Total unstimulated saliva was collected for ELISA assay analysis of receptor activator for nuclear factor κ B (RANK) and its ligand (RANK-L), osteoprotegerin, matrix metalloproteinase-9/ tissue inhibitor of metalloproteinase-2, vascular endothelial growth factor, and epidermal growth factor. Statistics were performed, and revealed that salivary RANK (p = 0.0304), RANK-L (p = 0.0005), matrix metalloproteinase-9/ tissue inhibitor of metalloproteinase-2 (p = 0.0067), vascular endothelial growth factor (p = 0.0060), and epidermal growth factor (p < 0.0001) were reduced in patients, compared with the control group. Osteoprotegerin did not differ between the groups (p = 0.3765). Salivary biomarkers did not differ according to radiotherapy completion time (p > 0.05). In conclusion, the lower output of the salivary molecules - essential for bone remodeling and tissue repair - may disrupt tissue homeostasis and play a role in the pathogenesis of the radiotherapy-induced deleterious effects in the oral cavity.

Biologics and their delivery systems: Trends in myocardial infarction

Cardiovascular disease is the leading cause of death around the world, in which myocardial infarction (MI) is a precipitating event. However, current therapies do not adequately address the multiple dysregulated systems following MI. Consequently, recent studies have developed novel biologic delivery systems to more effectively address these maladies. This review utilizes a scientometric summary of the recent literature to identify trends among biologic delivery systems designed to treat MI. Emphasis is placed on sustained or targeted release of biologics (e.g. growth factors, nucleic acids, stem cells, chemokines) from common delivery systems (e.g. microparticles, nanocarriers, injectable hydrogels, implantable patches). We also evaluate biologic delivery system trends in the entire regenerative medicine field to identify emerging approaches that may translate to the treatment of MI. Future developments include immune system targeting through soluble factor or chemokine delivery, and the development of advanced delivery systems that facilitate the synergistic delivery of biologics.

Comparative antler proteome of sika deer from different developmental stages

Antler is a special bone tissue that has the ability to regenerate completely periodically. It is the fastest growing bone in the animal kingdom. Antler provides a valuable research model for bone growth and mineralization. Antler grows longitudinally by endochondral ossification with their growth center located in its tip. Many scholars have carried out detailed studies on morphology and gene expression of antler tip. However, few scholars have analyzed the protein expression patterns of antler tip at different development stages. This study used label-free proteomics approach to analyze the protein expression dynamics of the antler tip in six developmental periods (15, 25, 45, 65, 100 and 130 days after the previous antler cast) and costal cartilage. In result, 2052 proteins were confidently quantified, including 1937 antler proteins and 1044 costal cartilage proteins. Moreover, 913 antler core proteins and 132 antler-special proteins were obtained. Besides, the stages special proteins and differentially expressed proteins (DEPs) in different development stages were analyzed. A total of 875 DEPs were determined by one-way AVOVA. It is found that the growth period (15, 25, 45 and 65 days) showed more up-regulated protein including several chondrogenesis-associated proteins (collagen types II, collagen types XI, HAPLN1, PAPSS1 and PAPSS2). In ossification stages, the up-regulated proteins related with lysosome (CTSD, CTSB, MMP9, CAII) indicated that the antler has higher bone remodeling activity. Given the up-regulated expression of immune-related molecules (S100A7, CATHL7, LTF, AZU1, ELANE and MPO), we speculate that the local immune system may contribute to the ossification of antler tip. In conclusion, proteomics technology was used to deeply analyze the protein expression patterns of antler at different development stages. This provides a strong support for the research on the molecular regulation mechanism of rapid growth and ossification of velvet antler.

Resistance Training Modulates the Matrix Metalloproteinase-2 Activity in Different Trabecular Bones in Aged Rats

Background

Aging decreases osteogenic ability, inducing harmful effects on the bone extracellular matrix (ECM), while exercise training has been indicated as a tool to counteract bone disorders related to advancing age. The modulation of bone ECM is regulated by several types of matrix metalloproteinase (MMP); however, MMP-2 activity in different trabecular bones in response to resistance training (RT) has been neglected. Remodeling differs in different bones under the application of the same mechanical loading. Thus, we investigated the effects of 12 weeks of RT on MMP-2 activity in the lumbar vertebra (L6), tibia, and femur of young (3 months) and older rats (21 months).

Methods

Twenty Wistar rats were divided into four groups (five animals per group): young sedentary or trained and older sedentary or trained. The 12-week RT consisted of climbing a 1.1-m vertical ladder three times per week with progressive weights secured to the animals’ tails. The animals were killed 48 h after the end of the experimental period. The MMP-2 activity was assessed by the zymography method.

Results

The aging process induced lower MMP-2 activity in the lumbar vertebrae and tibia (p=0.01). RT upregulated pro, intermediate, and active MMP-2 activity in the tibia of young rats (p=0.001). RT also upregulated pro and active MMP-2 activity in the lumbar vertebrae and tibia with advancing age (p=0.01). There was no significant difference (p>0.05) between groups for MMP-2 of the femur, regardless of age and RT.

Conclusion

The aging process impairs MMP-2 activity, but RT is a potential therapeutic approach to minimize the deleterious effects of ECM degeneration in different aged bones. Distinct MMP-2 responses to exercise training may result in specific remodeling processes.

Different roles of matrix metalloproteinase 2 in osteolysis of skeletal dysplasia and bone metastasis (Review)

Matrix metalloproteinase 2 (MMP2) is a well‑characterized protein that is indispensable for extracellular matrix remodeling and other pathological processes, such as tumor progression and skeletal dysplasia. Excessive activation of MMP2 promotes osteolytic metastasis and bone destruction in late‑stage cancers, while its loss‑of‑function mutations result in the decreased bone mineralization and generalized osteolysis occurring progressively in skeletal developmental disorders, particularly in multicentric osteolysis, nodulosis and arthropathy (MONA). Either upregulation or downregulation of MMP2 activity can result in the same osteolytic effects. Thus, different functions of MMP2 have been recently identified that could explain this observation. While MMP2 can degrade bone matrix, facilitate osteoclastogenesis and amplify various signaling pathways that enhance osteolysis in bone metastasis, its role in maintaining the number of bone cells, supporting osteocytic canalicular network formation and suppressing leptin‑mediated inhibition of bone formation has been implicated in osteolytic disorders caused by MMP2 deficiency. Furthermore, the proangiogenic activity of MMP2 is one of the potential mechanisms that are associated with both pathological situations. In the present article, the latest research on MMP2 in bone homeostasis is reviewed and the mechanisms underlying the role of this protein in skeletal metastasis and developmental osteolysis are discussed.

A Potential Participant in Type 2 Diabetes Bone Fragility: TIMP-1 at Sites of Osteocyte Lacunar-Canalicular System

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of bone fracture, but the bone mineral density (BMD) is typically normal or higher in such patients. Because the fracture risk is independent of reduced BMD, bone fragility in T2DM may be partially due to poor bone quality. The mechanisms triggering bone quality abnormalities in T2DM are complex, and include the accumulation of advanced glycation end-products, the increased inflammation, and low bone turnover. Matrix metalloproteinases (MMPs) in bone can hydrolyze the bone matrix. Tissue inhibitors of MMPs (TIMPs) can inhibit the activity of MMPs. Both MMPs and TIMPs participate in mediating bone quality. Among all types of TIMPs, TIMP-1 is mostly reportedly increased in the serum of T2DM patients. Because osteocytes can express TIMP-1, and osteocyte pericellular matrix influences bone quality partially regulated by perilacunar/canalicular remodeling, we hypothesized that TIMP-1 at sites of osteocyte lacunar-canalicular system is involved in T2DM bone fragility.

Gelatinases Cleave Dentin Sialoprotein Intracellularly

Dentin sialoprotein (DSP), the NH2-terminal fragment of dentin sialophosphoprotein (DSPP), is essential for dentin formation and further processed into small fragments inside the odontoblasts. Gelatinases, including matrix metalloproteinases 9 (MMP9) and MMP2, were able to cleave DSP(P) in tooth structures. We hypothesized that gelatinases may also cleave DSP intracellularly in the odontoblasts. In this study, the co-expression and physical interaction between DSP and gelatinases were proved by double immunofluorescence and in situ proximity ligation assay (PLA). Intracellular enzymatic activity of gelatinases was verified by gelatin zymography and in situ zymography. To confirm whether DSP was cleaved by active gelatinases intracellularly, lysates of wild-type (WT) odontoblastic cells treated with a MMP2 inhibitor or a MMP9 inhibitor or a MMP general inhibitor and of Mmp9^-/- odontoblastic cells were analyzed by western blotting. Compared with the WT odontoblastic cells without inhibitor treatment, all these groups exhibited significantly higher ratios of high molecular weight to low molecular weight band density. FURIN was verified to be co-localized and physically interacted with MMP9 by double immunofluorescence and in situ PLA. The ratio of proMMP9 to activated MMP9 inside the odontoblastic cells were increased when function of endogenous FURIN was inhibited. And overexpressed proMMP9 was intracellularly cleaved by FURIN in the HEK293E cells, which was completely blocked by the mutation of proMMP9 with R⁹⁶TPR⁹⁹ substituted by A⁹⁶AAA⁹⁹. Taken together, these results indicate that DSP is intracellularly processed by gelatinases, and FURIN is involved in the intracellular activation of proMMP9 through cleavage of its R⁹⁶TPR⁹⁹ motif.

Biometals and glycosylation in humans: Congenital disorders of glycosylation shed lights into the crucial role of Golgi manganese homeostasis

About half of the eukaryotic proteins bind biometals that participate in their structure and functions in virtually all physiological processes, including glycosylation. After reviewing the biological roles and transport mechanisms of calcium, magnesium, manganese, zinc and cobalt acting as cofactors of the metalloproteins involved in sugar metabolism and/or glycosylation, the paper will outline the pathologies resulting from a dysregulation of these metals homeostasis and more particularly Congenital Disorders of Glycosylation (CDGs) caused by ion transporter defects. Highlighting of CDGs due to defects in SLC39A8 (ZIP8) and TMEM165, two proteins transporting manganese from the extracellular space to cytosol and from cytosol to the Golgi lumen, respectively, has emphasized the importance of manganese homeostasis for glycosylation. Based on our current knowledge of TMEM165 structure and functions, this review will draw a picture of known and putative mechanisms regulating manganese homeostasis in the secretory pathway.

Destroy to Rebuild: The Connection Between Bone Tissue Remodeling and Matrix Metalloproteinases

Bone is a dynamic organ that undergoes constant remodeling, an energetically costly process by which old bone is replaced and localized bone defects are repaired to renew the skeleton over time, thereby maintaining skeletal health. This review provides a general overview of bone’s main players (bone lining cells, osteocytes, osteoclasts, reversal cells, and osteoblasts) that participate in bone remodeling. Placing emphasis on the family of extracellular matrix metalloproteinases (MMPs), we describe how: (i) Convergence of multiple protease families (including MMPs and cysteine proteinases) ensures complexity and robustness of the bone remodeling process, (ii) Enzymatic activity of MMPs affects bone physiology at the molecular and cellular levels and (iii) Either overexpression or deficiency/insufficiency of individual MMPs impairs healthy bone remodeling and systemic metabolism. Today, it is generally accepted that proteolytic activity is required for the degradation of bone tissue in osteoarthritis and osteoporosis. However, it is increasingly evident that inactivating mutations in MMP genes can also lead to bone pathology including osteolysis and metabolic abnormalities such as delayed growth. We argue that there remains a need to rethink the role played by proteases in bone physiology and pathology.

Inhibition of vascular endothelial growth factor in young adult mice causes low bone blood flow and bone strength with no effect on bone mass in trabecular regions

OBJECTIVE

To determine the effect of an antibody to vascular endothelial growth factor (VEGF) on bone blood flow, bone strength, and bone mass in the young adult mouse.

METHODS

Ten-week-old male BALB/cJ mice were body weight-randomized into either a rodent anti-VEGF monoclonal antibody (anti-VEGF, B20-4.1.1; 5 mg/kg 2×/wk.; n = 12) group or a vehicle (VEH; n = 12) group. After 42 days, mice were evaluated for bone blood flow at the distal femur by 18F-NaF-PET/CT and then necropsied. Samples from trabecular and cortical bone regions were evaluated for bone strength by mechanical testing, bone mass by peripheral quantitative computed tomography (pQCT), and micoarchitecture (MicroCT). Hydration of the whole femur was studied by proton nuclear magnetic resonance relaxometry (1H NMR).

RESULTS

Distal femur blood flow was 43% lower in anti-VEGF mice than in VEH mice (p = 0.009). Ultimate load in the lumbar vertebral body was 25% lower in anti-VEGF than in VEH mice (p = 0.013). Bone mineral density (BMD) in the trabecular region of the proximal humeral metaphysis by pQCT, and bone volume fraction and volumetric BMD by MicroCT were the same in the two groups. Volume fraction of bound water (BW) of the whole femur was 14% lower in anti-VEGF than in VEH mice (p = 0.003). Finally, BW, but not cortical tissue mineral density, helped section modulus explain the variance in the ultimate moment experienced by the femur in three-point bending.

CONCLUSION

Anti-VEGF caused low bone blood flow and bone strength in trabecular bone regions without influencing BMD and microarchitecture. Low bone strength was also associated with low bone hydration. These data suggest that bone blood flow is a novel bone property that affects bone quality.

MMP2 and MMP10 Polymorphisms Are Related to Steroid-Induced Osteonecrosis of the Femoral Head among Chinese Han Population

Background

Steroid-induced osteonecrosis of the femoral head is a relatively serious condition which seriously reduces patient quality of life. However, the pathogenesis of steroid-induced ONFH is still unclear. In recent years, more scholars have found that the pathogenesis of steroid-induced ONFH is related to susceptibility factors such as MMPs/TIMPs system. The main purpose of this study is to investigate the correlation between MMP2 and MMP10 gene polymorphisms and steroid-induced ONFH in Chinese Han population.

Methods

Six SNPs in MMP2 and two SNPs in MMP10 were genotyped using Agena MassARRAY RS1000 system from 286 patients of steroid-induced ONFH and in 309 healthy controls. The association between MMP2 and MMP10 polymorphisms and steroid-induced ONFH risk were estimated by the Chi-squared test, genetic model analysis, haplotype analysis, and stratification analysis. The relative risk was estimated by odd ratios (ORs) and 95% confidence intervals (CIs).

Result

We found that the minor TG allele of rs470154 in MMP10 was associated with an increased risk of steroid-induced ONFH (OR = 1.45, 95% CI, 1.03 – 2.05, p = 0.032). In the genetic model analysis, we found that rs2241146 in MMP2 gene and rs470154 in MMP10 gene showed a statistically significant association with increased risk of steroid-induced ONFH. The six SNPs (rs470154, rs243866, rs243864, rs865094, rs11646643, and rs2241146) showed a statistically significant association with different clinical phenotypes.

Conclusion

Our results verify that genetic polymorphisms of MMP2 and MMP10 contribute to steroid-induced ONFH susceptibility in the population of Chinese Han population, and our study provides new insights into the role that MMP2 and MMP10 plays in the mechanism of ONFH.

Bone repair in craniofacial defects treated with different doses of alendronate: a histological, histomorphometric, and immunohistochemical study

OBJECTIVE

The objective of the study is to evaluate bone repair in rats treated with different alendronate doses.

MATHERIALS AND METHODS

Sixty female rats ovariectomized were randomly divided in three groups: group C (control group), group A1 (ALN/1 mg/kg), and A2 (ALN/ 3 mg/kg). Each animal received subcutaneous applications of sodium alendronate at a dose correspondent to group A1 or A2 three times a week, while the control group received 0.9% saline solution. After 4 weeks of application, a critical defect was created in the calvaria of animals of all groups. The defect was filled by particulate autogenous bone. The applications were maintained until euthanasia, which occurred 15 and 60 days after the surgical procedure. The pieces were sent for histological, histomorphometric and immunohistochemical analysis. The data were submitted to statistical analysis with significance level of 0.05.

RESULTS

The descriptive histological analysis demonstrated an increase in bone neoformation in both groups treated with alendronate when compared to the control group. The histomorphometric analysis showed an increase in the amount of neoformed bone in A1 and A2 groups when compared to group C, both at 15 days (p = 0.0002) and at 60 days (p = 0.001). In the immunohistochemical analysis, it was possible to observe a difference in immunolabeling just for Mmp2 at the time of 60 days in A1 (p = 0.001) and A2 (p = 0.023) when compared to the control group.

CONCLUSION

Systemic delivery of alendronate, regardless of the dose, increased the amount of bone neoformation.

CLINICAL RELEVANCE

Prescription of sodium alendronate at 1 mg/kg for improvement of bone neoformation in bone graft procedures.

Evaluation of the presence of MMP-2, TIMP-2, BMP2/4, and TGFβ3 in the facial tissue of children with cleft lip and palate

Cleft lip and palate (CLP) is the most common defect affecting the face. The treatment consists of surgical reconstruction of the anatomical structures of the cleft. Part of the surgical treatment is reconstruction of the alveolar bone by means of autogenic bone grafting (osteoplasty). This study aimed to evaluate the levels of expression of extracellular matrix remodeling factors in the facial tissue of children with a complete unilateral (CU) and a complete bilateral (CB) CLP to assess whether the wound healing process is adequate. Twenty-two CLP patients were enrolled in this study. Tissue samples were collected during alveolar osteoplasty for unilateral (n = 12) or bilateral (n = 10) cleft palate, (age range from 6 years 8 months to 12 years 2 months). Control material was obtained in the case of tooth extraction (age range from 6 years 9 months to 14 years 5 months). Immunohistochemistry was used to assess the levels of matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase-2 (TIMP-2), bone morphogenetic proteins 2 and 4 (BMP2/4), and transforming growth factor β3 (TGFβ3). Numbers of positively stained cells were graded semi-quantitatively. Data were analysed using the Kraskel-Wallis rank test and the Bonferroni correction. The total number of MMP2-positive cells was significantly lower in the CBCLP and in the control group than in the CUCLP (p < 0.001 after the Bonferroni correction). The total number of TIMP2-positive cells was significantly higher in the CUCLP than in the CBCLP and in the control group (p < 0.001; p < 0.003 after the Bonferroni correction). The overall number of BMP2/4, TGFβ3-positive cells was significantly higher in the CUCLP than in the CBCLP and in the control group (p < 0.001 after the Bonferroni correction). The decrease of the relative amount of statistically significant BMP2/4, TGFβ3, MMP-2, TIMP-2 containing bone cells in CBCLP patients identifies affected alveolar bone regeneration and remodeling process.

Effect of Local Application of Alendronate and Parathyroid Hormone on Craniofacial Bone Repair - a Preliminary Study

This study aimed to evaluate the effect of two methods of local application of alendronate and parathyroid hormone (PTH) on bone repair and the systemic implications. A critically sized defect (5 mm) was created in the cranial region of twenty-five male Wistar rats, and the bone removed was particulated, and grafted back to the defect with different treatments. The animals were randomly divided into five groups: A1- bone graft immersion in alendronate solution (3 mg/kg) for 5 minutes; P1- bone graft immersion in PTH solution (20 µg); A2- weekly local applications of alendronate 1 mg/kg; P2- weekly local applications of PTH (20 µg); C- no drugs were used. The animals were euthanized 60 days after surgery. Cranial bone blocks were removed for histological, histomorphometric, and immunohistochemical analyses. MMP-2 and MMP-9 were used for immunolabeling. The kidneys, liver, and brain were also removed from all the rats for histological analysis. The data were submitted for statistical analysis with a level of significance of 0.05 (One-way ANOVA). The group C and group P2 presented a higher quantity of viable bone particles than the remaining groups. Groups A1, A2, and P1 presented with fewer viable bone particles than the control group, with a predominance of non-mineralized connective tissue. The histomorphometric analysis revealed no differences in relative bone area or MMP-2 or MMP-9 immunolabeling between the groups (p>0.05). Group A2 showed presence of fat in the liver consistent with hepatic steatosis. Changes in brain tissue were observed in groups A1 and P1.

Dynamic expression of matrix metalloproteinases 2, 9 and 13 in ovariectomy-induced osteoporosis rats

The aim of the present study was to examine the dynamic expression of matrix metalloproteinase (MMP)-2, MMP-9 and MMP-13 in an ovariectomy (OVX)-induced osteoporosis rat model. A total of 80 Sprague-Dawley female rats (age, 3 months) were randomly divided into the OVX and sham groups, with 40 rats in each group. Rats in the sham group received sham surgery, while the remaining rats were ovariectomized. After 12, 16, 20 and 24 weeks, 10 rats from each group were randomly sacrificed, respectively. It was observed that the bone mineral density (BMD) and the trabecular bone area in the OVX group were significantly lower as compared with those in the sham group (P<0.01). The expression levels of MMP-2 and MMP-9 were negatively correlated with the BMD, while MMP-13 was positively correlated with the BMD. The expression levels of MMP-2 and MMP-9 increased more abruptly and were significant higher in the OVX group in comparison with those in the sham group between 12 and 24 weeks after surgery (P<0.01). More specifically, the MMP-9 mRNA expression level in the OVX group increased abruptly between 12 and 24 weeks after surgery. By contrast, in the sham group, the MMP-9 mRNA level was undetectable between 12 and 16 weeks, and increased steadily between 16 and 24 weeks. Furthermore, the mRNA and protein expression levels of MMP-13 initially increased and then decreased in the OVX group (P<0.01 vs. the sham group), whereas they continuously increased in the sham group between 12 and 24 weeks after surgery. In conclusion, MMP-2, MMP-9 and MMP-13 regulated the development of osteoporosis, and MMP-9 may be used as an important marker in the early diagnosis of osteoporosis.

18β-Glycyrrhetinic Acid Inhibits Osteoclastogenesis In Vivo and In Vitro by Blocking RANKL-Mediated RANK-TRAF6 Interactions and NF-κB and MAPK Signaling Pathways

Bone metabolism is determined by a delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts. The imbalance due to over-activated osteoclasts plays an important role in various diseases. Activation of NF-κB and MAPK signaling pathways by receptor activator of nuclear factor -κB ligand (RANKL) is vital for osteoclastogenesis. Here, we for the first time explored the effects of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid found in the Glycyrrhiza glabra L roots, on RANKL-induced osteoclastogenesis, osteoclast functions and signaling pathways in vitro and in vivo. In bone marrow monocytes (BMMs) and RAW264.7 cells, 18β-GA inhibited osteoclastogenesis, decreased expression of TRAP, cathepsin K, CTR and MMP-9, blocked actin ring formation and compromised osteoclasts functions in a dose-dependent manner at an early stage with minimal effects on osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). For underlying molecular mechanisms, 18β-GA inhibited RANKL-induced phosphorylation of p65, p50, and IκB, blocked p65 nuclear translocation and decreased the DNA-binding activity of NF-κB. Besides, 18β-GA inhibited the activation of the MAPK pathways. Co-immunoprecipitation showed that 18β-GA treatment blocked RANK-TRAF6 association at an upstream site. In vivo, 18β-GA treatment inhibited ovariectomy-induced osteoclastogenesis and reduced bone loss in mice. Overall, our results demonstrated that 18β-GA inhibited RANKL-induced osteoclastogenesis by inhibiting RANK expression in preosteoclasts and blocking the binding of RANK and TRAF6 which lead to the inhibition of NF-κB and MAPK signaling pathways. 18β-GA is a promising novel candidate in the treatment of osteoclast-related diseases such as postmenopausal osteoporosis.

Bioactive glass-ceramic bone repair associated or not with autogenous bone: a study of organic bone matrix organization in a rabbit critical-sized calvarial model

OBJECTIVE

The aim of the study was to analyze bone matrix (BMX) organization after bone grafting and repair using a new bioactive glass-ceramic (Biosilicate^®) associated or not with particulate autogenous bone graft.

MATERIAL AND METHODS

Thirty rabbits underwent surgical bilateral parietal defects and divided into groups according to the materials used: (C) control-blood clot, (BG) particulate autogenous bone, (BS) bioactive glass-ceramic, and BG + BS. After 7, 14, and 30 days post-surgery, a fragment of each specimen was fixed in - 80 °C liquid nitrogen for zymographic evaluation, while the remaining was fixed in 10% formalin for histological birefringence analysis.

RESULTS

The results of this study demonstrated that matrix organization in experimental groups was significantly improved compared to C considering collagenous organization. Zymographic analysis revealed pro-MMP-2, pro-MMP-9, and active (a)-MMP-2 in all groups, showing gradual decrease of total gelatinolytic activity during the periods. At day 7, BG presented more prominent gelatinolytic activity for pro-MMP-2 and 9 and a-MMP-2, when compared to the other groups. In addition, at day 7, a 53% activation ratio (active form/[active form + latent form]) was evident in C group, 33% in BS group, and 31% in BG group.

CONCLUSION

In general, BS allowed the production of a BMX similar to BG, with organized collagen deposition and MMP-2 and MMP-9 disponibility, permitting satisfactory bone remodeling at the late period.

CLINICAL RELEVANCE

The evaluation of new bone substitute, with favorable biological properties, opens the possibility for its use as a viable and efficient alternative to autologous bone graft.

Applying Full Spectrum Analysis to a Raman Spectroscopic Assessment of Fracture Toughness of Human Cortical Bone

A decline in the inherent quality of bone tissue is a † Equal contributors contributor to the age-related increase in fracture risk. Although this is well-known, the important biochemical factors of bone quality have yet to be identified using Raman spectroscopy (RS), a nondestructive, inelastic light-scattering technique. To identify potential RS predictors of fracture risk, we applied principal component analysis (PCA) to 558 Raman spectra (370-1720 cm^-1) of human cortical bone acquired from 62 female and male donors (nine spectra each) spanning adulthood (age range = 21-101 years). Spectra were analyzed prior to R-curve, nonlinear fracture mechanics that delineate crack initiation (K_init) from crack growth toughness (K_grow). The traditional ν₁phosphate peak per amide I peak (mineral-to-matrix ratio) weakly correlated with K_init (r = 0.341, p = 0.0067) and overall crack growth toughness (J-int: r = 0.331, p = 0.0086). Sub-peak ratios of the amide I band that are related to the secondary structure of type 1 collagen did not correlate with the fracture toughness properties. In the full spectrum analysis, one principal component (PC5) correlated with all of the mechanical properties (K_init: r = - 0.467, K_grow: r = - 0.375, and J-int: r = - 0.428; p < 0.0067). More importantly, when known predictors of fracture toughness, namely age and/or volumetric bone mineral density (vBMD), were included in general linear models as covariates, several PCs helped explain 45.0% (PC5) to 48.5% (PC7), 31.4% (PC6), and 25.8% (PC7) of the variance in K_init, K_grow, and J-int, respectively. Deriving spectral features from full spectrum analysis may improve the ability of RS, a clinically viable technology, to assess fracture risk.

Isothiocyanates suppress the invasion and metastasis of tumors by targeting FAK/MMP-9 activity

Isothiocyanates, which are present as glucosinolate precursors in cruciferous vegetables, have strong activity against various cancers. Here, we compared the anti-metastatic effects of isothiocyanates (benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), and sulforaphane (SFN)) by examining how they regulate MMP-9 expression. Isothiocyanates, particularly PEITC, suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced MMP-9 activity and invasion in various cancer cell lines. By contrast, N-methyl phenethylamine, a PEITC analog without an isothiocyanate functional group, had no effect. A reporter gene assay demonstrated that BITC, PEITC, and SFN suppressed TAP-induced MMP-9 expression by inhibiting AP-1 and NF-κB in U20S osteosarcoma cells. All three compounds reduced phosphorylation of FAK, ERK1/2, and Akt. In addition, MMP-9 expression was downregulated by inhibiting FAK, ERK1/2, and Akt. Isothiocyanates-mediated inhibition of FAK phosphorylation suppressed phosphorylation of ERK1/2 and Akt in U2OS and A549 cells, along with the translocation of p65 and c-Fos, suggesting that isothiocyanates inhibit MMP-9 expression and cell invasion by blocking phosphorylation of FAK. Furthermore, isothiocyanates, abolished MMP-9 expression and tumor metastasis in vivo with the following efficacy: PEITC>BITC>SFN. Thus, isothiocyanates act as anti-metastatic compounds that suppress MMP-9 activity/expression by inhibiting NF-κB and AP-1 via suppression of the FAK/ERK and FAK/Akt signaling pathways.

Vibrational spectroscopic techniques to assess bone quality

Although musculoskeletal diseases such as osteoporosis are diagnosed and treatment outcome is evaluated based mainly on routine clinical outcomes of bone mineral density (BMD) by DXA and biochemical markers, it is recognized that these two indicators, as valuable as they have proven to be in the everyday clinical practice, do not fully account for manifested bone strength. Thus, the term bone quality was introduced, to complement considerations based on bone turnover rates and BMD. Bone quality is an "umbrella" term that incorporates the structural and material/compositional characteristics of bone tissue. Vibrational spectroscopic techniques such as Fourier transform infrared microspectroscopy (FTIRM) and imaging (FTIRI), and Raman spectroscopy, are suitable analytical tools for the determination of bone quality as they provide simultaneous, quantitative, and qualitative information on all main bone tissue components (mineral, organic matrix, tissue water), in a spatially resolved manner. Moreover, the results of such analyses may be readily combined with the outcomes of other techniques such as histology/histomorphometry, small angle X-ray scattering, quantitative backscattered electron imaging, and nanoindentation.

Matrix Metalloproteinases in Bone Resorption, Remodeling, and Repair

Matrix metalloproteinases (MMPs) are the major protease family responsible for the cleavage of the matrisome (global composition of the extracellular matrix (ECM) proteome) and proteins unrelated to the ECM, generating bioactive molecules. These proteins drive ECM remodeling, in association with tissue-specific and cell-anchored inhibitors (TIMPs and RECK, respectively). In the bone, the ECM mediates cell adhesion, mechanotransduction, nucleation of mineralization, and the immobilization of growth factors to protect them from damage or degradation. Since the first description of an MMP in bone tissue, many other MMPs have been identified, as well as their inhibitors. Numerous functions have been assigned to these proteins, including osteoblast/osteocyte differentiation, bone formation, solubilization of the osteoid during bone resorption, osteoclast recruitment and migration, and as a coupling factor in bone remodeling under physiological conditions. In turn, a number of pathologies, associated with imbalanced bone remodeling, arise mainly from MMP overexpression and abnormalities of the ECM, leading to bone osteolysis or bone formation. In this review, we will discuss the functions of MMPs and their inhibitors in bone cells, during bone remodeling, pathological bone resorption (osteoporosis and bone metastasis), bone repair/regeneration, and emergent roles in bone bioengineering.

Matrix Metallopeptidase-2 Gene rs2287074 Polymorphism is Associated with Brick Tea Skeletal Fluorosis in Tibetans and Kazaks, China

Brick tea skeletal fluorosis is still a public health issue in the north-western area of China. However its pathogenesis remains unknown. Our previous study reveals that the severity of skeletal fluorosis in Tibetans is more serious than that in Kazaks, although they have similar fluoride exposure, suggesting the onset of brick tea type skeletal fluorosis might be genetically influenced. Here we show that MMP-2 rs2287074 SNP (G/A), but not rs243865, was associated with Brick tea type fluorosis in Tibetans and Kazaks, China. The trend test reveals a decline in probability for skeletal fluorosis with increasing number of A alleles in Tibetans. After controlling potential confounders, AA genotype had about 80 percent lower probability of developing skeletal fluorosis than GG genotype in Tibetans (odds ratio = 0.174, 95% CI: 0.053, 0.575), and approximately 53 percent lower probability in Kazaks (odds ratio = 0.462, 95% CI: 0.214, 0.996). A meta-analysis shows that the AA genotype had approximately 63 percent lower odds (odds ratio = 0.373, 95% CI: 0.202, 0.689) compared with GG genotype within the two ethnicities. A significant correlation was also found between the genotype of MMP2 rs2287074 and skeletal fluorosis severity. Therefore, the A allele of MMP2 rs2287074 could be a protective factor for brick tea skeletal fluorosis.