The impairment of osteogenesis in bone sialoprotein (BSP) knockout calvaria cell cultures is cell density dependent

OPN, BSP, and Bone Quality-Structural, Biochemical, and Biomechanical Assessment in OPN-/-, BSP-/-, and DKO Mice

Osteopontin (OPN) and Bone Sialoprotein (BSP), abundantly expressed by osteoblasts and osteoclasts, appear to have important, partly overlapping functions in bone. In gene-knockout (KO, -/-) models of either protein and their double (D)KO in the same CD1/129sv genetic background, we analyzed the morphology, matrix characteristics, and biomechanical properties of femur bone in 2 and 4 month old, male and female mice. OPN-/- mice display inconsistent, perhaps localized hypermineralization, while the BSP-/- are hypomineralized throughout ages and sexes, and the low mineralization of young DKO mice recovers with age. The higher contribution of primary bone remnants in OPN-/- shafts suggests a slow turnover, while their lower percentage in BSP-/- indicates rapid remodeling, despite FTIR-based evidence in this genotype of a high maturity of the mineralized matrix. In 3-point bending assays, OPN-/- bones consistently display higher Maximal Load, Work to Max. Load and in young mice Ultimate Stress, an intrinsic characteristic of the matrix. Young male and old female BSP-/- also display high Work to Max. Load along with low Ultimate Stress. Principal Component Analysis confirms the major role of morphological traits in mechanical competence, and evidences a grouping of the WT phenotype with the OPN-/- and of BSP-/- with DKO, driven by both structural and matrix parameters, suggesting that the presence or absence of BSP has the most profound effects on skeletal properties. Single or double gene KO of OPN and BSP thus have multiple distinct effects on skeletal phenotypes, confirming their importance in bone biology and their interplay in its regulation.

Functional defects in cementoblasts with disrupted bone sialoprotein functional domains, in vitro

Bone sialoprotein (BSP) is a multifunctional extracellular matrix (ECM) protein present in bone and cementum. Global in vivo ablation of BSP leads to bone mineralization defects, lack of acellular cementum, and periodontal breakdown. BSP harbors three main functional domains: N-terminal collagen-binding domain, hydroxyapatite-nucleating domain, and C-terminal RGD integrin-binding signaling domain. How each of these domains contributes to BSP function(s) is not understood. We hypothesized that collagen-binding and RGD domains play distinct roles in cementoblast functions. Three CRISPR/Cas9 gene-edited cell lines were derived from control wild-type (WT) OCCM.30 murine immortalized cementoblasts: 1) deletion of the N-terminus of BSP after signal peptide, including entire collagen binding domain (Ibsp∆N-Term); 2) deletion of exon 4 (majority of collagen-binding domain; Ibsp∆Ex4); and 3) deletion of C-terminus of BSP including the integrin binding RGD domain (Ibsp∆C-Term). Compared to WT, Ibsp∆Ex4 and Ibsp∆C-Term cell lines showed reduced BSP secretion, in vitro. Abnormal cell morphology was observed in all mutant cell lines, with Ibsp∆C-Term showing highly disorganized cytoskeleton. All mutant cell lines showed significantly lower cell proliferation compared to WT at all timepoints. Ibsp∆N-Term cells showed reduced cell migration by 24 h. All mutants exhibited over 50 % significant reduced mineralization at days 6 and 10. While WT cells were largely unaffected by seeding density, mutant cells failed to mineralize at lower cell density. Mutant cell lines diverged from WT and from each other by dysregulated expression in 23 genes involved in mineralization, ECM, and cell signaling. In summary, disabling BSP functional domains led to profound and distinct changes in cementoblast cell functions, especially dysregulated gene expression and reduced mineralization, in a way did not align with a straightforward narrative where each functional domain caused specific, expected differences. Instead, the study uncovered a significant level of complexity in how different mutant forms of BSP affected cell functions, in vitro.

Central and peripheral tau retention modulated by an anti-tau antibody

Tau protein blood levels dependent on its distribution to peripheral organs and possible elimination from the body. Thus, the peripheral distribution of CSF-derived tau protein was explored, especially since there is a transition to blood-based biomarkers and the emerging idea that tau pathology may spread beyond brain. Near infrared fluorescence (NIRF) was mainly used to analyze tau (tau-NIRF) distribution after its intracisternal or intravenous injection. There was a striking uptake of blood- or CSF-derived tau-NIRF protein by the skeletal structures, liver, small intestine (duodenum), gall bladder, kidneys, urinary bladder, lymph nodes, heart, and spleen. In aging and in older APP/PS1 mice, tau uptake in regions, such as the brain, liver, and skeleton, was increased. In bone (femur) injected tau protein was associated with integrin-binding sialoprotein (IBSP), a major non-collagenous glycoprotein that is associated with mineralization. Tau-NIRF was cleared slowly from CSF via mainly across the cribriform plate, and cervical lymph nodes. In brain, some of the CSF injected tau protein was associated with NeuN-positive and PDGFRý-positive cells, which may explain its retention. The presence of tau in the bladders suggested excretion routes of tau. CSF anti-tau antibody increased CSF tau clearance, while blood anti-tau antibody decreased tau accumulation in the femur but not in liver, kidney, and spleen. Thus, the data show a body-wide distribution and retention of CSF-derived tau protein, which increased with aging and in older APP/PS1 mice. Further work is needed to elucidate the relevance of tau accumulation in each organ to tauopathy.

Osteogenic effects of rapamycin on bone marrow mesenchymal stem cells via inducing autophagy

BACKGROUND

While autophagy is essential for stem cells' self-renewal and differentiation, its effect on bone marrow mesenchymal stem cells (BMSCs) remains unclear. This study aimed to investigate the interaction between autophagy and osteogenic differentiation using rapamycin (RAPA), a classical autophagy agonist with osteo-regulatory effects.

METHODS

Rat BMSC's autophagy was analyzed after osteoinduction (0, 7, 14, and 21 d) by western blotting, immunofluorescence, and real-time quantitative polymerase chain reaction (RT-qPCR). In addition, we evaluated osteogenic differentiation using alizarin red staining, alkaline phosphatase assays, and RT-qPCR/Western blotting quantification of bone sialoprotein, type 1 collagen, alkaline phosphatase, osteopontin, and Runt-related transcription factor 2 mRNA and protein levels.

RESULTS

The BMSC's basal autophagy level gradually decreased during osteogenic differentiation with a decrease in BECN1 level and the lipidated (LC3-II) to unlipidated (LC3-I) microtubule-associated protein 1 light chain 3 ratio and an increase in the expression of selective autophagic target p62. In contrast, it increased with increasing RAPA concentration. Furthermore, while 2 nM RAPA promoted BMSC osteogenic differentiation on days 7 and 14, 5 nM RAPA inhibited osteogenesis on days 14 and 21. Inhibition of autophagy by the inhibitor 3-methyladenine could impair RAPA's osteogenesis-enhancing effect on BMSCs.

CONCLUSIONS

The BMSC's basal autophagy level decreased over time during osteogenic differentiation. However, an appropriate RAPA concentration promoted BMSC osteogenic differentiation via autophagy activation.

Fabrication of Interleukin-4 Encapsulated Bioactive Microdroplets for Regulating Inflammation and Promoting Osteogenesis

Background

Despite the inherent regenerative ability of bone, large bone defect regeneration remains a major clinical challenge for orthopedic surgery. Therapeutic strategies medicated by M2 phenotypic macrophages or M2 macrophage inducer have been widely used to promote tissue remodeling. In this study, ultrasound-responsive bioactive microdroplets (MDs) encapsulated with bioactive molecule interleukin-4 (IL4, hereafter designated MDs-IL4) were fabricated to regulate macrophage polarization and potentiate the osteogenic differentiation of human mesenchymal stem cells (hBMSCs).

Materials and Methods

The MTT assay, live and dead staining, and phalloidin/DAPI dual staining were used to evaluate biocompatibility in vitro. H&E staining was used to evaluate biocompatibility in vivo. Inflammatory macrophages were further induced via lipopolysaccharide (LPS) stimulation to mimic the pro-inflammatory condition. The immunoregulatory role of the MDs-IL4 was tested via macrophage phenotypic marker gene expression, pro-inflammatory cytokine level, cell morphological analysis, and immunofluorescence staining, etc. The immune-osteogenic response of hBMSCs via macrophages and hBMSCs interactions was further investigated in vitro.

Results

The bioactive MDs-IL4 scaffold showed good cytocompatibility in RAW 264.7 macrophages and hBMSCs. The results confirmed that the bioactive MDs-IL4 scaffold could reduce inflammatory phenotypic macrophages, as evidenced by changing in morphological features, reduction in pro-inflammatory marker gene expression, increase of M2 phenotypic marker genes, and inhibition of pro-inflammatory cytokine secretion. Additionally, our results indicate that the bioactive MDs-IL4 could significantly enhance the osteogenic differentiation of hBMSCs via its potential immunomodulatory properties.

Conclusion

Our results demonstrate that the bioactive MDs-IL4 scaffold could be used as novel carrier system for other pro-osteogenic molecules, thus having potential applications in bone tissue regeneration.

Surface modification of silica nonwoven fabrics for osteogenesis of bone marrow-derived mesenchymal stem cells

Silica nonwoven fabrics (SNFs) with high mechanical strength and porosity are known to exhibit high cell proliferation and osteogenic differentiation potential of mesenchymal stem cells (MSCs) by morphologically mimicking the extracellular matrix (ECM). To further improve the osteoinductive ability of SNFs, it could be effective to increase the interaction between MSCs and ECM components because exogenous ECM components seem to modulate the fate of MSCs differentiation. In this study, we developed immobilization methods for ECM components, such as collagen, fibronectin, and chondroitin sulphate C on SNFs, to improve cell-matrix interactions and examined their suitability for bone tissue regeneration. Collagen and fibronectin were immobilized via physical adsorption and chondroitin sulphate C was also immobilized by the layer-by-layer method combined with chitosan on SNF surfaces to maintain the high porosity of SNFs. The treated SNFs were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In osteogenic differentiation culture, modified SNFs showed significantly increased expression of osteogenic differentiation marker genes compared to unmodified SNFs. These results suggest that the present methods improve cell-matrix interactions and enhance the cellular functions of MSCs. We are convinced that these simple modification techniques for ECM components are effective in functionalizing various 3D fabric scaffolds possessing hydrophilic groups.

The role of Meteorin-like in skeletal development and bone fracture healing

Meteorin-like protein (Metrnl), homologous to the initially identified neurotrophic factor Meteorin, is a secreted, multifunctional protein. Here we used mouse models to investigate Metrnl's role in skeletal development and bone fracture healing. During development Metrnl was expressed in the perichondrium and primary ossification center. In neonates, single cell RNA-seq of diaphyseal bone demonstrated strongest expression of Metrnl transcript by osteoblasts. In vitro, Metrnl was osteoinductive, increasing osteoblast differentiation and mineralization in tissue culture models. In vivo, loss of Metrnl expression resulted in no change in skeletal metrics in utero, at birth, or during postnatal growth. Six-week-old Metrnl-null mice displayed similar body length, body weight, tibial length, femoral length, BV/TV, trabecular number, trabecular thickness, and cortical thickness as littermate controls. In 4-month-old mice, lack of Metrnl expression did not change structural stiffness, ultimate force, or energy to fracture of femora under 3-point-bending. Last, we investigated the role of Metrnl in bone fracture healing. Metrnl expression increased in response to tibial injury, however, loss of Metrnl expression did not affect the amount of bone deposited within the healing tissue nor did it change the structural parameters of healing tissue. This work identifies Metrnl as a dispensable molecule for skeletal development. However, the osteoinductive capabilities of Metrnl may be utilized to modulate osteoblast differentiation in cell-based orthopedic therapies.

The Bone Sialoprotein RGD Domain Modulates and Maintains Periodontal Development

Bone sialoprotein (gene: Ibsp; protein: BSP) is a multifunctional extracellular matrix protein present in bone, cementum, and dentin. Accumulating evidence supports BSP as a key regulator of mineralized tissue formation via evolutionarily conserved functional domains, including a C-terminal integrin-binding Arg-Gly-Asp (RGD) domain implicated in extracellular matrix-cell signaling. Ablation of Ibsp in mice (Ibsp-/-) results in impaired bone growth and mineralization and defective osteoclastogenesis, with effects in the craniofacial region including reduced acellular cementum formation, detachment of the periodontal ligament (PDL), alveolar bone hypomineralization, and severe periodontal breakdown. We hypothesized that BSP-RGD plays an important role in cementum and alveolar bone formation and mineralization, as well as periodontal function. This hypothesis was tested by replacing the RGD motif with a nonfunctional Lys-Ala-Glu (KAE) sequence in (IbspKAE/KAE) mice and OCCM.30 murine (IbspKAE) cementoblasts. The RGD domain was not critical for acellular or cellular cementum formation in IbspKAE/KAE mice. However, PDL volume and thickness were increased, and significantly more tartrate-resistant acid phosphatase-positive osteoclasts were found on alveolar bone surfaces of IbspKAE/KAE mice versus wild type mice. PDL organization was disrupted as indicated by picrosirius red stain, second harmonic generation imaging, dynamic mechanical analysis, and decreased asporin proteoglycan localization. In vitro studies implicated RGD functions in cell migration, adhesion, and mineralization, and this was confirmed by an ossicle implant model where cells lacking BSP-RGD showed substantial defects as compared with controls. In total, the BSP-RGD domain is implicated in periodontal development, though the scale and scope of changes indicated by in vitro studies indicate that other factors may partially compensate for and reduce the phenotypic severity of mice lacking BSP-RGD in vivo.

In Situ-Forming Collagen/poly-γ-glutamic Acid Hydrogel System with Mesenchymal Stem Cells and Bone Morphogenetic Protein-2 for Bone Tissue Regeneration in a Mouse Calvarial Bone Defect Model

BACKGROUND

Bone marrow-derived mesenchymal stem cells (BMSCs) and bone morphogenetic protein-2 (BMP-2) have been studied for bone repair because they have regenerative potential to differentiate into osteoblasts. The development of injectable and in situ three-dimensional (3D) scaffolds to proliferate and differentiate BMSCs and deliver BMP-2 is a crucial technology in BMSC-based tissue engineering.

METHODS

The proliferation of mouse BMSCs (mBMSCs) in collagen/poly-γ-glutamic acid (Col/γ-PGA) hydrogel was evaluated using LIVE/DEAD and acridine orange and propidium iodide assays. In vitro osteogenic differentiation and the gene expression level of Col/γ-PGA(mBMSC/BMP-2) were assessed by alizarin red S staining and quantitative reverse-transcription polymerase chain reaction. The bone regeneration effect of Col/γ-PGA(mBMSC/BMP-2) was evaluated in a mouse calvarial bone defect model. The cranial bones of the mice were monitored by micro-computed tomography and histological analysis.

RESULTS

The developed Col/γ-PGA hydrogel showed low viscosity below ambient temperature, while it provided a high elastic modulus and viscous modulus at body temperature. After gelation, the Col/γ-PGA hydrogel showed a 3D and interconnected porous structure, which helped the effective proliferation of BMSCs with BMP-2. The Col/γ-PGA (mBMSC/BMP-2) expressed more osteogenic genes and showed effective orthotopic bone formation in a mouse model with a critical-sized bone defect in only 3-4 weeks.

CONCLUSION

The Col/γ-PGA(mBMSC/BMP-2) hydrogel was suggested to be a promising platform by combining collagen as a major component of the extracellular matrix and γ-PGA as a viscosity reducer for easy handling at room temperature in BMSC-based bone tissue engineering scaffolds.

Cinnamaldehyde protect against ligature-induced periodontitis through inhibitions of microbial accumulation and inflammatory responses of host immune cells

Cinnamaldehyde (CA), the main active ingredient of cinnamon, is proved to be a potential candidate of controlling inflammation, but few evidences are demonstrated on its role in periodontitis. The aim...

Bio-functionalization and in-vitro evaluation of titanium surface with recombinant fibronectin and elastin fragment in human mesenchymal stem cell

Titanium is a biomaterial that meets a number of important requirements, including excellent mechanical and chemical properties, but has low bioactivity. To improve cellular response onto titanium surfaces and hence its osseointegration, the titanium surface was bio-functionalized to mimic an extracellular matrix (ECM)-like microenvironment that positively influences the behavior of stem cells. In this respect, fibronectin and elastin are important components of the ECM that regulate stem cell differentiation by supporting the biological microenvironment. However, each native ECM is unsuitable due to its high production cost and immunogenicity. To overcome these problems, a recombinant chimeric fibronectin type III_9-10 and elastin-like peptide fragments (FN9-10_ELP) was developed herein and applied to the bio-functionalized of the titanium surface. An evaluation of the biological activity and cellular responses with respect to bone regeneration indicated a 4-week sustainability on the FN9-10_ELP functionalized titanium surface without an initial burst effect. In particular, the adhesion and proliferation of human mesenchymal stem cells (hMSCs) was significantly increased on the FN9-10_ELP coated titanium compared to that observed on the non-coated titanium. The FN9-10_ELP coated titanium induced osteogenic differentiation such as the alkaline phosphatase (ALP) activity and mineralization activity. In addition, expressions of osteogenesis-related genes such as a collagen type I (Col I), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), osteocalcin (OCN), bone sialo protein (BSP), and PDZ-binding motif (TAZ) were further increased. Thus, in vitro the FN9-10_ELP functionalization titanium not only sustained bioactivity but also induced osteogenic differentiation of hMSCs to improve bone regeneration.

An In Vitro and In Vivo Comparison of Osteogenic Differentiation of Human Mesenchymal Stromal/Stem Cells

The use of stem cells in regenerative medicine, including tissue engineering and transplantation, has generated a great deal of enthusiasm. Mesenchymal stromal/stem cells (MSCs) can be isolated from various tissues, most commonly, bone marrow but more recently adipose tissue, dental pulp, and Wharton's jelly, to name a few. MSCs display varying phenotypic profiles and osteogenic differentiating capacity depending and their site of origin. MSCs have been successfully differentiated into osteoblasts both in vitro an in vivo but discrepancies exist when the two are compared: what happens in vitro does not necessarily happen in vivo, and it is therefore important to understand why these differences occur. The osteogenic process is a complex network of transcription factors, stimulators, inhibitors, proteins, etc., and in vivo experiments are helpful in evaluating the various aspects of this osteogenic process without distractions and confounding variables. With that in mind, the results of in vitro experiments need to be carefully considered and interpreted with caution as they do not perfectly replicate the conditions found within living organisms. This is where in vivo experiments help us better understand interactions that might occur in the osteogenic process that cannot be replicated in vitro. Potentially, these differences could also be exploited to develop an optimal MSC cell therapeutic product that can be used for bone disorders. There are many bone disorders, most of which cause a great deal of discomfort. Clinically acceptable protocols could be developed in which MSCs are used to aid in bone regeneration providing relief for patients with chronic pain. The aim of this review is to examine the differences between studies conducted in vitro and in vivo with regard to the osteogenic process to better define the gaps in current osteogenic research. By better understanding osteogenic differentiation, we can better define treatment strategies for various bone disorders.

FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes

FAM20C is a gene coding for a protein kinase that targets S-X-E/pS motifs on different phosphoproteins belonging to diverse tissues. Pathogenic variants of FAM20C are responsible for Raine syndrome (RS), initially described as a lethal and congenital osteosclerotic dysplasia characterized by generalized atherosclerosis with periosteal bone formation, characteristic facial dysmorphisms and intracerebral calcifications. The aim of this review is to give an overview of targets and variants of FAM20C as well as RS aspects. We performed a wide phenotypic review focusing on clinical aspects and differences between all lethal (LRS) and non-lethal (NLRS) reported cases, besides the FAM20C pathogenic variant description for each. As new targets of FAM20C kinase have been identified, we reviewed FAM20C targets and their functions in bone and other tissues, with emphasis on novel targets not previously considered. We found the classic lethal and milder non-lethal phenotypes. The milder phenotype is defined by a large spectrum ranging from osteonecrosis to osteosclerosis with additional congenital defects or intellectual disability in some cases. We discuss our current understanding of FAM20C deficiency, its mechanism in RS through classic FAM20C targets in bone tissue and its potential biological relevance through novel targets in non-bone tissues.

Effects of Cirsium setidens (Dunn) Nakai on the osteogenic differentiation of stem cells

Cirsium setidens (Dunn) Nakai, commonly known as gondre, is a perennial herb that grows predominantly in South Korea. It contains several bioactive phytochemicals with antioxidant, anti-cancer, anti-tumor and anti-inflammatory properties. The present study aimed to investigate the effects of methanolic extracts of gondre on osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs). As characterized by nuclear magnetic resonance spectroscopy and matrix-assisted laser deposition/ionization (time-of-flight) mass spectrometry, the methanol extract of gondre was found to be enriched with pectolinarin. After 48 h, enhanced viability of hPDLSCs was observed in the presence of gondre compared with under control conditions, suggesting the biocompatibility of gondre. Notably, biocompatibility was markedly affected by gondre concentration in cultured media. Relatively high cell viability was observed in medium containing 0.05% gondre. Furthermore, mineralization was significantly higher in hPDLSCs in the presence of gondre compared with that in control cells, indicating their mineralization potential. Increased expression of various transcription markers, such as collagen 1, runt-related transcription factor 2, bone sialoprotein and alkaline phosphatase, was also detected when hPDLSCs were stimulated with gondre compared with in the control groups, further confirming the superior osteogenic potential of gondre extract for tissue engineering applications, particularly in bone tissues.

Evaluation of the Effects of Cuminum cyminum on Cellular Viability, Osteogenic Differentiation and Mineralization of Human Bone Marrow-Derived Stem Cells

Background and Objectives: Cuminum cyminum L. has long been used in the treatment of various diseases in multiple geographical regions. This study was performed to determine the effects of C. cyminum methanolic extract (CCT) on the cellular viability, alkaline phosphatase activity and mineralization of human mesenchymal stem cells. Materials and Methods: Bone marrow-derived stem cells were cultured in the presence of CCT at concentrations of 0, 0.001, 0.01, 0.1 and 1 μg/mL. Evaluations of cell morphology were performed on days 1, 3, 7 and 14. Cellular viability was evaluated on days 1, 3, 5 and 7. On the 7th and 14th day, alkaline phosphatase activity measurements and Alizarin red S staining were conducted to assess the osteogenic differentiation of stem cells. A real-time polymerase chain reaction was used to determine the expression levels of RUNX2, BSP, OCN, COL2A1 and β-catenin mRNAs. Results: Stem cells in the control group showed fibroblast-like morphology and the addition of CCT at 0.001, 0.01, 0.1 and 1 μg/mL did not generate noticeable changes in morphology compared with the untreated control group. The application of CCT did not produce significant changes in cellular viability or alkaline phosphatase activity compared with controls. Alizarin Red S staining was significantly increased with the application of CCT. Treatment with CCT increased the expressions of RUNX2, BSP and OCN. Conclusions: These results indicate that CCT enhanced the osteogenic differentiation of stem cells derived from bone marrow by regulating the expressions of RUNX2, BSP and OCN. Thus, the use of CCT may be applied to achieve beneficial effects on the mineralization of stem cells.

Influence of Maitake (Grifola frondosa) Particle Sizes on Human Mesenchymal Stem Cells and In Vivo Evaluation of Their Therapeutic Potential

Maitake (Grifola frondosa) mushroom has received an enormous amount of attention as a dietary supplement due to its high nutritional values. The particle sizes of G. frondosa mushrooms were monitored by a classifying mill. β-Glucans are the bioactive component of the mushroom, and it was revealed through Fourier transform infrared spectroscopy (FTIR), proton and carbon nuclear magnetic resonance (¹H and ¹³C-NMR), matrix-assisted laser desorption/ionization, and time-of-flight (MALDI-TOF) spectrometry. The biocompatibility of G. frondosa particles, as well as induced osteogenesis of hMSCs, was evaluated through WST-1 assay and alizarin staining (ARS) technique, respectively. Notably, enhanced cell viability was noted in the presence of G. frondosa. Significantly improved calcium deposition has observed from hMSCs with G. frondosa, suggesting to their mineralization potential. The expression of osteogenic related gene markers was examined in the presence of G. frondosa through real-time polymerase chain reaction (qPCR) technique. The upregulation of osteogenic gene markers in the presence of G. frondosa particles was indicating their superior osteogenic potential. Besides, G. frondosa also activated the secretion of various kinds of proteins from the hMSCs indicating their potential for tissue engineering applications. Enhanced secretion of different immunoglobulins was observed in rat serum in the presence of G. frondosa, further demonstrating their therapeutic nature. Therefore, G. frondosa is effective for enhanced osteogenesis and can be utilized as a natural, edible, and osteogenic agent.

Osteopontin is An Important Regulative Component of the Fetal Bone Marrow Hematopoietic Stem Cell Niche

Osteopontin (OPN) is an important component in both bone and blood regulation, functioning as a bridge between the two. Previously, thrombin-cleaved osteopontin (trOPN), the dominant form of OPN in adult bone marrow (BM), was demonstrated to be a critical negative regulator of adult hematopoietic stem cells (HSC) via interactions with α₄β₁ and α₉β₁ integrins. We now demonstrate OPN is also required for fetal hematopoiesis in maintaining the HSC and progenitor pool in fetal BM. Specifically, we showed that trOPN is highly expressed in fetal BM and its receptors, α₄β₁ and α₉β₁ integrins, are both highly expressed and endogenously activated on fetal BM HSC and progenitors. Notably, the endogenous activation of integrins expressed by HSC was attributed to high concentrations of three divalent metal cations, Ca²⁺, Mg²⁺ and Mn²⁺, which were highly prevalent in developing fetal BM. In contrast, minimal levels of OPN were detected in fetal liver, and α₄β₁ and α₉β₁ integrins expressed by fetal liver HSC were not in the activated state, thereby permitting the massive expansion of HSC and progenitors required during early fetal hematopoiesis. Consistent with these results, no differences in the number or composition of hematopoietic cells in the liver of fetal OPN^-/- mice were detected, but significant increases in the hematopoietic progenitor pool in fetal BM as well as an increase in the BM HSC pool following birth and into adulthood were observed. Together, the data demonstrates OPN is a necessary negative regulator of fetal and neonatal BM progenitors and HSC, and it exhibits preserved regulatory roles during early development, adulthood and ageing.

Mechanical strain triggers differentiation of dental mesenchymal stem cells by activating osteogenesis-specific biomarkers expression

Dental stem cell biotechnology has been used as a potential method to treat the dental diseases. This study aimed to investigate effects of mechanical stimulation on osteogenic properties of rat dental mesenchymal stem cells (DMSCs). DMSCs were isolated from rat teeth root tissues and identified by detecting vimentin and keratin expression. Flexcell FX4K tension system that mediating cyclic strain was used to treat DMSCs. MTT assay was used to observe DMSCs viability. Alkaline phosphatase (ALP) staining and alizarin red staining were conducted. Osteogenesis-specific biomarkers, such as receptor activator for nuclear factor-kB ligand (RANKL), osteoprotegerin (OPG), dentin sialoprotein (DSP) and bone sialoprotein (BSP), were evaluated using RT-PCR, western blot and immunohistochemistry assay, respectively. Positive ALP staining and alizarin red staining confirmed DMSCs phenotype. There were no significant morphology differences between mechanical stimuli treated cells and normal control cells. MTT results showed no significant differences between normal control cells and mechanically stimulated DMSCs. RT-PCR, western blot and immunohistochemistry assay indicated that 10% cyclic strain could trigger an obvious change of mRNA and protein expression of RANKL, OPG, DSP and BSP, respectively. Mechanical stimulation could trigger relative higher levels of calcium deposition in DMSCs. Mechanical strain triggered bone formation mainly through activating RANKL gene expression. In conclusion, 10% cycle mechanical strain could stimulate higher amounts of ALP and calcium deposition by activating RNAKL, and could trigger dramatically changes of mRNA and protein expression of osteogenesis-specific biomarkers, such as OPG, BSP and DSP.

Transcriptome analysis of osteoblasts in an ovariectomized mouse model in response to physical exercise

Objectives

Osteoporosis is a metabolic disease resulting in progressive loss of bone mass as measured by bone mineral density (BMD). Physical exercise has a positive effect on increasing or maintaining BMD in postmenopausal women. The contribution of exercise to the regulation of osteogenesis in osteoblasts remains unclear. We therefore investigated the effect of exercise on osteoblasts in ovariectomized mice.

Methods

We compared the activity of differentially expressed genes of osteoblasts in ovariectomized mice that undertook exercise (OVX+T) with those that did not (OVX), using microarray and bioinformatics.

Results

Many inflammatory pathways were significantly downregulated in the osteoblasts after exercise. Meanwhile, IBSP and SLc13A5 gene expressions were upregulated in the OVX+T group. Furthermore, in in vitro assay, IBSP and SLc13A5 mRNAs were also upregulated during the osteogenic differentiation of MC3T3-E1 and 7F2 cells.

Conclusion

These findings suggest that exercise may not only reduce the inflammatory environment in ovariectomized mice, indirectly suppressing the overactivated osteoclasts, but may also directly activate osteogenesis-related genes in osteoblasts. Exercise may thus prevent the bone loss caused by oestrogen deficiency through mediating the imbalance between the bone resorptive activity of osteoclasts and the bone formation activity of osteoblasts.

Cite this article: W-B. Hsu, W-H. Hsu, J-S. Hung, W-J. Shen, R. W-W. Hsu. Transcriptome analysis of osteoblasts in an ovariectomized mouse model in response to physical exercise. Bone Joint Res 2018;7:601–608. DOI: 10.1302/2046-3758.711.BJR-2018-0075.R2.

Amelogenesis imperfecta: A novel FAM83H mutation and characteristics of periodontal ligament cells

OBJECTIVE

To delineate orodental features, dental mineral density, genetic aetiology and cellular characteristics associated with amelogenesis imperfecta (AI).

MATERIALS AND METHODS

Three affected patients in a family were recruited. Whole-exome sequencing was used to identify mutations confirmed by Sanger sequencing. The proband's teeth were subjected for mineral density analysis by microcomputerised tomography and characterisation of periodontal ligament cells (PDLCs).

RESULTS

The patients presented yellow-brown, pitted and irregular enamel. A novel nonsense mutation, c.1261G>T, p.E421*, in exon 5 of the FAM83H was identified. The mineral density of the enamel was significantly decreased in the proband. The patient's PDLCs (FAM83H cells) exhibited reduced ability of cell proliferation and colony-forming unit compared with controls. The formation of stress fibres was remarkably present. Upon cultured in osteogenic induction medium, FAM83H cells, at day 7 compared to day 3, had a significant reduction of BSP, COL1 and OCN mRNA expression and no significant change in RUNX2. The upregulation of ALP mRNA levels and mineral deposition were comparable between FAM83H and control cells.

CONCLUSIONS

We identified the novel mutation in FAM83H associated with autosomal dominant hypocalcified AI. The FAM83H cells showed reduced cell proliferation and expression of osteogenic markers, suggesting altered PDLCs in FAM83H-associated AI.

Expression and regulation of the ERK1/2 and p38 MAPK signaling pathways in periodontal tissue remodeling of orthodontic tooth movement

The present study aimed to investigate the expression and regulation of extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) signaling pathways in periodontal tissue remodeling of orthodontic tooth movement. Sprague Dawley rats with orthodontic tooth movement were generated. After tension stress for 1, 3, 5, 7 and 14 days, the protein and mRNA expression levels of ERK1/2 and p38 in periodontal tissue were determined by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), respectively. Primary human periodontal ligament cells (hPDLCs) were separated and characterized. Following exposure to centrifugal force for 1, 2, 6, 8 and 12 h, the protein expression levels of ERK1/2 and p38 MAPK, and the mRNA expression levels of ERK1/2, p38 and osteogenesis associated-genes [including alkaline phosphatase (ALP), osteopontin (OPN), collagen I (Col I), osteocalcin (OCN) and bone sialoprotein (BSP)] were measured. The protein expression levels of ERK1/2 and p38 MAPK in periodontal tissue and hPDLCs treated with stress were similar to those in the control groups. However, compared with the control, the phosphorylation and mRNA expression levels of the genes encoding ERK1/2 and p38 MAPK in orthodontic periodontal tissue and forced hPDLCs were elevated. These increases reached a peak at 5 days for orthodontic periodontal tissue and at 6 h for forced hPDLCs. In forced hPDLCs, the mRNA expression levels of ALP, OPN, Col I, OCN and BSP were notably and continuously upregulated in a time-dependent manner. In addition, hPDLCs were treated with the ERK1/2 inhibitor, PD098059, and the p38 MAPK inhibitor, SB203580, and the mRNA expression levels of the osteogenesis associated-genes were then measured using RT-qPCR. Following treatment with the ERK1/2 inhibitor and p38 MAPK inhibitor, the mRNA expression levels of ALP, OPN, Col I, OCN and BSP were significantly downregulated. In conclusion, ERK1/2 and p38 MAPK signaling pathways may be positively and closely associated with periodontal tissue remodeling of orthodontic tooth movement.

Macrotopographic closure promotes tissue growth and osteogenesis in vitro

While the impact of substrate topographies at nano- and microscale on bone cell behavior has been particularly well documented, very few studies have analyzed the role of substrate closure at a tissular level. Moreover, these have focused on matrix deposition rather than on osteoblastic differentiation. In the present work, mouse calvaria cells were grown for 15days on hydroxyapatite (HA) ceramics textured with three different macrogrooves shapes (^**100µm): 1 sine and 2 triangle waveforms. We found that macrotopography favors cell attachment, and that bone-like tissue growth and organization are promoted by a tight "closure angle" of the substrate geometry. Interestingly, while Flat HA controls showed little marker expression at the end of the culture, cells grown on macrogrooves, and in particular the most closed (triangle waveform with a 517µm spatial period) showed a fast time-course of osteoblast differentiation, reaching high levels of gene and protein expression of osteocalcin and sclerostin, a marker of osteocytes.

STATEMENT OF SIGNIFICANCE

Many in vitro studies have been conducted on topography at nano and microscale, fewer have focused on the influence of macrotopography on osteoblasts. Ceramics with a controlled architecture were obtained throught a 3D printing process and used to assess osteoblast behavior. Biocompatible, they allowed the long-terme survival of osteoblast cells and the laying of an important bone matrix. V-shaped grooves were found to accelerates osteoblast differentiation and promote bone-like tissue deposition and maturation (osteocyte formation), proportionately to angle closure. Such macrostructures are attractive for the design of innovative implants for bone tissue engineering and in vitro models of osteogenesis.

Bone Shaft Revascularization After Marrow Ablation Is Dramatically Accelerated in BSP-/- Mice, Along With Faster Hematopoietic Recolonization

The bone organ integrates the activity of bone tissue, bone marrow, and blood vessels and the factors ensuring this coordination remain ill defined. Bone sialoprotein (BSP) is with osteopontin (OPN) a member of the small integrin binding ligand N-linked glycoprotein (SIBLING) family, involved in bone formation, hematopoiesis and angiogenesis. In rodents, bone marrow ablation induces a rapid formation of medullary bone which peaks by ∼8 days (d8) and is blunted in BSP-/- mice. We investigated the coordinate hematopoietic and vascular recolonization of the bone shaft after marrow ablation of 2 month old BSP+/+ and BSP-/- mice. At d3, the ablated area in BSP-/- femurs showed higher vessel density (×4) and vascular volume (×7) than BSP+/+. Vessel numbers in the shaft of ablated BSP+/+ mice reached BSP-/- values only by d8, but with a vascular volume which was twice the value in BSP-/-, reflecting smaller vessel size in ablated mutants. At d6, a much higher number of Lin^- (×3) as well as LSK (Lin^- IL-7Rα^- Sca-1^hi c-Kit^hi , ×2) and hematopoietic stem cells (HSC: Flt3^- LSK, ×2) were counted in BSP-/- marrow, indicating a faster recolonization. However, the proportion of LSK and HSC within the Lin^- was lower in BSP-/- and more differentiated stages were more abundant, as also observed in unablated bone, suggesting that hematopoietic differentiation is favored in the absence of BSP. Interestingly, unablated BSP-/- femur marrow also contains more blood vessels than BSP+/+, and in both intact and ablated shafts expression of VEGF and OPN are higher, and DMP1 lower in the mutants. In conclusion, bone marrow ablation in BSP-/- mice is followed by a faster vascular and hematopoietic recolonization, along with lower medullary bone formation. Thus, lack of BSP affects the interplay between hematopoiesis, angiogenesis, and osteogenesis, maybe in part through higher expression of VEGF and the angiogenic SIBLING, OPN. J. Cell. Physiol. 232: 2528-2537, 2017. © 2016 Wiley Periodicals, Inc.

The role of the SIBLING, Bone Sialoprotein in skeletal biology - Contribution of mouse experimental genetics

Bone Sialoprotein (BSP) is a member of the "Small Integrin-Binding Ligand N-linked Glycoproteins" (SIBLING) extracellular matrix protein family of mineralized tissues. BSP has been less studied than other SIBLING proteins such as Osteopontin (OPN), which is coexpressed with it in several skeletal cell types. Here we review the contribution of genetically engineered mice (BSP gene knockout and overexpression) to the understanding of the role of BSP in the bone organ. The studies made so far highlight the role of BSP in skeletal mineralization, as well as its importance for proper osteoblast and osteoclast differentiation and activity, most prominently in primary/repair bone. The absence of BSP also affects the local environment of the bone tissue, in particular hematopoiesis and vascularization. Interestingly, lack of BSP induces an overexpression of OPN, and the cognate protein could be responsible for some aspects of the BSP gene knockout skeletal phenotype, while replacing BSP for some of its functions. Such interplay between the partly overlapping functions of SIBLING proteins, as well as the network of cross-regulations in which they are involved should now be the focus of further work.

MEMO1 drives cranial endochondral ossification and palatogenesis

The cranial base is a component of the neurocranium and has a central role in the structural integration of the face, brain and vertebral column. Consequently, alteration in the shape of the human cranial base has been intimately linked with primate evolution and defective development is associated with numerous human facial abnormalities. Here we describe a novel recessive mutant mouse strain that presented with a domed head and fully penetrant cleft secondary palate coupled with defects in the formation of the underlying cranial base. Mapping and non-complementation studies revealed a specific mutation in Memo1 - a gene originally associated with cell migration. Expression analysis of Memo1 identified robust expression in the perichondrium and periosteum of the developing cranial base, but only modest expression in the palatal shelves. Fittingly, although the palatal shelves failed to elevate in Memo1 mutants, expression changes were modest within the shelves themselves. In contrast, the cranial base, which forms via endochondral ossification had major reductions in the expression of genes responsible for bone formation, notably matrix metalloproteinases and markers of the osteoblast lineage, mirrored by an increase in markers of cartilage and extracellular matrix development. Concomitant with these changes, mutant cranial bases showed an increased zone of hypertrophic chondrocytes accompanied by a reduction in both vascular invasion and mineralization. Finally, neural crest cell-specific deletion of Memo1 caused a failure of anterior cranial base ossification indicating a cell autonomous role for MEMO1 in the development of these neural crest cell derived structures. However, palate formation was largely normal in these conditional mutants, suggesting a non-autonomous role for MEMO1 in palatal closure. Overall, these findings assign a new function to MEMO1 in driving endochondral ossification in the cranium, and also link abnormal development of the cranial base with more widespread effects on craniofacial shape relevant to human craniofacial dysmorphology.