Fibrinogen Induces RUNX2 Activity and Osteogenic Development from Human Pluripotent Stem Cells

Platelet-rich fibrin as an autologous biomaterial for bone regeneration: mechanisms, applications, optimization

Platelet-rich fibrin, a classical autologous-derived bioactive material, consists of a fibrin scaffold and its internal loading of growth factors, platelets, and leukocytes, with the gradual degradation of the fibrin scaffold and the slow release of physiological doses of growth factors. PRF promotes vascular regeneration, promotes the proliferation and migration of osteoblast-related cells such as mesenchymal cells, osteoblasts, and osteoclasts while having certain immunomodulatory and anti-bacterial effects. PRF has excellent osteogenic potential and has been widely used in the field of bone tissue engineering and dentistry. However, there are still some limitations of PRF, and the improvement of its biological properties is one of the most important issues to be solved. Therefore, it is often combined with bone tissue engineering scaffolds to enhance its mechanical properties and delay its degradation. In this paper, we present a systematic review of the development of platelet-rich derivatives, the structure and biological properties of PRF, osteogenic mechanisms, applications, and optimization to broaden their clinical applications and provide guidance for their clinical translation.

Bone Formation and Maintenance in Oral Surgery: The Decisive Role of the Immune System-A Narrative Review of Mechanisms and Solutions

Based on the evidence of a significant communication and connection pathway between the bone and immune systems, a new science has emerged: osteoimmunology. Indeed, the immune system has a considerable impact on bone health and diseases, as well as on bone formation during grafts and its stability over time. Chronic inflammation induces the excessive production of oxidants. An imbalance between the levels of oxidants and antioxidants is called oxidative stress. This physio-pathological state causes both molecular and cellular damage, which leads to DNA alterations, genetic mutations and cell apoptosis, and thus, impaired immunity followed by delayed or compromised wound healing. Oxidative stress levels experienced by the body affect bone regeneration and maintenance around teeth and dental implants. As the immune system and bone remodeling are interconnected, bone loss is a consequence of immune dysregulation. Therefore, oral tissue deficiencies such as periodontitis and peri-implantitis should be regarded as immune diseases. Bone management strategies should include both biological and surgical solutions. These protocols tend to improve immunity through antioxidant production to enhance bone formation and prevent bone loss. This narrative review aims to highlight the relationship between inflammation, oxidation, immunity and bone health in the oral cavity. It intends to help clinicians to detect high-risk situations in oral surgery and to propose biological and clinical solutions that will enhance patients' immune responses and surgical treatment outcomes.

Induced pluripotent stem cell technology in bone biology

Technologies on the development and differentiation of human induced pluripotent stem cells (hiPSCs) are rapidly improving, and have been applied to create cell types relevant to the bone field. Differentiation protocols to form bona fide bone-forming cells from iPSCs are available, and can be used to probe details of differentiation and function in depth. When applied to iPSCs bearing disease-causing mutations, the pathogenetic mechanisms of diseases of the skeleton can be elucidated, along with the development of novel therapeutics. These cells can also be used for development of cell therapies for cell and tissue replacement.

Circ_0018168 inhibits the proliferation and osteogenic differentiation of fibroblasts in ankylosing spondylitis via regulating miR-330-3p/DKK1 axis

Background

Circular RNAs (circRNAs) play a crucial regulatory role in human diseases. However, the roles of circRNAs in ankylosing spondylitis (AS) are barely known. In this study, the functions of circ_0018168 in AS were investigated.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot assay were used for circ_0018168, microRNA-330-3p (miR-330-3p), dickkopf-1 (DKK1), alkaline phosphatase (ALP), osteocalcin (OCN), Runt-related transcription factor 2 (Runx2) levels. Cell Counting Kit-8 (CCK-8) assay and 5′-ethynyl-2′-deoxyuridine (EdU) assay were conducted to analyze cell proliferation ability. Flow cytometry analysis was manipulated for cell cycle process. ALP activity was examined with a commercial kit. RNA immunoprecipitation (RIP) assay, RNA pull-down assay and dual-luciferase reporter assay were used to analyze the relationships of circ_0018168, miR-330-3p and DKK1.

Results

Circ_0018168 and DKK1 levels were lowly expressed in AS hip capsule specimens. Circ_0018168 overexpression repressed cell proliferation, cell cycle process as well as reduced ALP activity and ALP, OCN and Runx2 protein levels in AS fibroblasts. DKK1 silencing ameliorated the impact of circ_0018168 on AS progression. In addition, circ_0018168 served as the sponge for miR-330-3p, which could target DKK1. MiR-330-3p inhibition suppressed the proliferation, cell cycle and osteogenic differentiation in AS fibroblasts, but DKK1 silencing reversed the impacts. Besides, the effect of circ_0018168 on AS development was abolished by miR-330-3p upregulation.

Conclusion

Circ_0018168 overexpression restrained fibroblast proliferation and osteogenic differentiation in AS by elevating DKK1 through adsorbing miR-330-3p.

Platelets and osteoblasts: secretome connections

Megakaryocyte hyperplasia associated with myeloproliferative neoplasms commonly leads to abnormal bone tissue deposition in the bone marrow, known as osteosclerosis. In this study, we aimed to synthesize the known proteomics literature describing factors released by megakaryocytes and platelets and to examine if any of the secreted factors have a known ability to stimulate the bone-forming cells, osteoblasts. Using a systematic search of Medline, we identified 77 articles reporting on factors secreted by platelets and megakaryocytes. After a full-text screening and analysis of the studies, we selected seven papers that reported proteomics data for factors secreted by platelets from healthy individuals. From 60 proteins reported in at least two studies, we focused on 23 that contained a putative signal peptide, which we searched for a potential osteoblast-stimulatory function. From nine proteins with a positive effect on osteoblast formation and function, two extracellular matrix (ECM) proteins, secreted protein acidic and rich in cysteine (SPARC) and tissue inhibitor of metalloproteinase-1 (TIMP1), and three cellular proteins with known extracellular function, the 70-kDa heat shock protein (HSP70), thymosin-β4 (TB4), and super dismutase (SOD), were identified as hypothetical candidate molecules to be examined as potential mediators in mouse models of osteomyelofibrosis. Thus, careful analysis of prior literature can be beneficial in assisting the planning of future experimental studies.

Developmental principles informing human pluripotent stem cell differentiation to cartilage and bone

Human pluripotent stem cells can differentiate into any cell type given appropriate signals and hence have been used to research early human development of many tissues and diseases. Here, we review the major biological factors that regulate cartilage and bone development through the three main routes of neural crest, lateral plate mesoderm and paraxial mesoderm. We examine how these routes have been used in differentiation protocols that replicate skeletal development using human pluripotent stem cells and how these methods have been refined and improved over time. Finally, we discuss how pluripotent stem cells can be employed to understand human skeletal genetic diseases with a developmental origin and phenotype, and how developmental protocols have been applied to gain a better understanding of these conditions.

Apheresis Platelet Rich-Plasma for Regenerative Medicine: An In Vitro Study on Osteogenic Potential

Background: Platelet-Rich Plasma (PRP) induces bone regeneration; however, there is low evidence supporting its efficacy in bone healing. The lack of a standardized protocol of administration represents the main obstacle to its use in the clinical routine for bone defects’ treatment. The purpose of this study was to characterize PRP and elucidate its osteogenic potential. Methods: Platelet count, fibrinogen levels, and growth factors concentration were measured in PRP obtained by four apheresis procedures. HOB-01-C1, a pre-osteocytic cell line, was used to examine the effects of different PRP dilutions (from 1% to 50%) on cell viability, growth, and differentiation. Gene expression of RUNX2, PHEX, COL1A1, and OCN was also assayed. Results: PRP showed a mean 4.6-fold increase of platelets amount compared to whole blood. Among the 36 proteins evaluated, we found the highest concentrations for PDGF isoforms, EGF, TGF-β and VEGF-D. PDGF-AA positively correlated with platelet counts. In three of the four tested units, 25% PRP induced a growth rate comparable to the positive control (10% FBS); whereas, for all the tested units, 10% PRP treatment sustained differentiation. Conclusions: This study showed that PRP from apheresis stimulates proliferation and differentiation of pre-osteocyte cells through the release of growth factors from platelets.

Comparative proteomic analysis of osteogenic differentiated human adipose tissue and bone marrow-derived stromal cells

Mesenchymal stromal cells are promising candidates for regenerative applications upon treatment of bone defects. Bone marrow‐derived stromal cells (BMSCs) are limited by yield and donor morbidity but show superior osteogenic capacity compared to adipose‐derived stromal cells (ASCs), which are highly abundant and easy to harvest. The underlying reasons for this difference on a proteomic level have not been studied yet. Human ASCs and BMSCs were characterized by FACS analysis and tri‐lineage differentiation, followed by an intraindividual comparative proteomic analysis upon osteogenic differentiation. Results of the proteomic analysis were followed by functional pathway analysis. 29 patients were included with a total of 58 specimen analysed. In these, out of 5148 identified proteins 2095 could be quantified in >80% of samples of both cell types, 427 in >80% of ASCs only and 102 in >80% of BMSCs only. 281 proteins were differentially regulated with a fold change of >1.5 of which 204 were higher abundant in BMSCs and 77 in ASCs. Integrin cell surface interactions were the most overrepresented pathway with 5 integrins being among the proteins with highest fold change. Integrin 11a, a known key protein for osteogenesis, could be identified as strongly up‐regulated in BMSC confirmed by Western blotting. The integrin expression profile is one of the key distinctive features of osteogenic differentiated BMSCs and ASCs. Thus, they represent a promising target for modifications of ASCs aiming to improve their osteogenic capacity and approximate them to that of BMSCs.

Lineage-specific differentiation of osteogenic progenitors from pluripotent stem cells reveals the FGF1-RUNX2 association in neural crest-derived osteoprogenitors

Human pluripotent stem cells (hPSCs) can provide a platform to model bone organogenesis and disease. To reflect the developmental process of the human skeleton, hPSC differentiation methods should include osteogenic progenitors (OPs) arising from three distinct embryonic lineages: the paraxial mesoderm, lateral plate mesoderm, and neural crest. Although OP differentiation protocols have been developed, the lineage from which they are derived, as well as characterization of their genetic and molecular differences, has not been well reported. Therefore, to generate lineage-specific OPs from human embryonic stem cells and human induced pluripotent stem cells, we employed stepwise differentiation of paraxial mesoderm-like cells, lateral plate mesoderm-like cells, and neural crest-like cells toward their respective OP subpopulation. Successful differentiation, confirmed through gene expression and in vivo assays, permitted the identification of transcriptomic signatures of all three cell populations. We also report, for the first time, high FGF1 levels in neural crest-derived OPs-a notable finding given the critical role of fibroblast growth factors (FGFs) in osteogenesis and mineral homeostasis. Our results indicate that FGF1 influences RUNX2 levels, with concomitant changes in ERK1/2 signaling. Overall, our study further validates hPSCs' power to model bone development and disease and reveals new, potentially important pathways influencing these processes.

microRNA-214-3p Suppresses Ankylosing Spondylitis Fibroblast Osteogenesis via BMP-TGFβ Axis and BMP2

Recent investigations suggest microRNAs (miRs) exert functions in fibroblast osteogenesis in ankylosing spondylitis (AS), an inflammatory rheumatic disease. But the mechanism of miR-214-3p in osteogenic differentiation in AS is not clearly understood yet. In this study, fibroblasts were obtained from the capsular ligament of patients with AS and femoral neck fracture and cultured for osteogenic induction and identified. The roles of miR-214-3p and bone morphogenic protein 2 (BMP2) in AS fibroblast osteogenesis were assessed via gain- and loss-of-function, alizarin red S staining, and alkaline phosphatase (ALP) detection. Levels of miR-214-3p, BMP2, osteogenic differentiation-related proteins, and BMP-TGFβ axis-related proteins were further measured. Consequently, miR-214-3p was downregulated in AS fibroblasts, with enhanced ALP activity and calcium nodules, which were reversed by miR-214-3p overexpression. BMP2 was a target gene of miR-214-3p and promoted AS fibroblast osteogenesis by activating BMP-TGFβ axis, while miR-214-3p inhibited AS fibroblast osteogenesis by targeting BMP2. Together, miR-214-3p could prevent AS fibroblast osteogenic differentiation by targeting BMP2 and blocking BMP-TGFβ axis. This study may offer a novel insight for AS treatment.

microRNA-132 inhibits osteogenic differentiation of periodontal ligament stem cells via GDF5 and the NF-κB signaling pathway

BACKGROUND

Periodontal ligament stem cells (PDLSCs) could differentiate into osteoblasts and have a great prospect in treating bone diseases. microRNAs (miRs) and nuclear factor kappa-B (NF-κB) signaling pathway have proved pivotal in regulating osteogenic differentiation. This study intended to discuss the mechanism of miR-132 and NF-κB in PDLSC osteogenesis.

METHODS

PDLSCs were firstly cultured, induced, and identified by detecting the surface markers and observing cell morphology. Levels of osteogenic markers alkaline phosphatase (ALP), bone morphogenetic proteins 2 (BMP2), runt-related transcription factor 2 (Runx2) and osteocalcin (OCN), along with miR-132 expression were measured. The osteoblast activity and mineral deposition were detected by ALP and alizarin red S (ARS) stainings. The targeting relationship between miR-132 and growth differentiation factor 5 (GDF5) was verified. The gain-and loss-of-function was performed to discuss roles of miR-132 and GDF5 in osteogenic differentiation of PDLSCs. Besides, levels of NF-κB signaling pathway-related proteins were measured.

RESULTS

In osteogenic differentiation of PDLSCs, levels of ALP, BMP2, Runx2 and OCN were upregulated while miR-132 was downregulated. Overexpressing miR-132 reduced levels of osteogenic markers, osteoblast activity, ALP and ARS intensity and the activation of NF-κB axis. GDF5 is a target of miR-132 and GDF5 overexpression reversed the inhibitory effects of overexpressed miR-132 on PDLSC osteogenesis.

CONCLUSION

Together, miR-132 could inhibit PDLSC osteogenesis via targeting GDF5 and activating NF-κB axis. These data provide useful information for PDLSC application in periodontal therapy.

Thermal cycling effect on osteogenic differentiation of MC3T3-E1 cells loaded on 3D-porous Biphasic Calcium Phosphate (BCP) scaffolds for early osteogenesis

The application of heat stress on a defect site during the healing process is a promising technique for early bone regeneration. The primary goal of this study was to investigate the effect of periodic heat shock on bone formation. MC3T3-E1 cells were seeded onto biphasic calcium phosphate (BCP) scaffolds, followed by periodic heating to evaluate osteogenic differentiation. Heat was applied to cells seeded onto scaffolds at 41 °C for 1 h once, twice, and four times a day for seven days and their viability, morphology, and differentiation were analyzed. BCP scaffolds with interconnected porous structures mimic bone biology for cellular studies. MTT and confocal studies have shown that heat shock significantly increased cell proliferation without any toxic effects. Compared to non-heated samples, heat shock enhanced calcium deposition and mineralization, which could be visualized by SEM observation and Alizarin red S staining. Immunostaining images showed the localization of osteogenic proteins ALP and OPN on heat-shocked cells. qRT-PCR analysis revealed the presence of more osteospecific markers, osteopontin (OPN), osteocalcin, collagen type X, and Runx2, in the heat-shocked samples than in the non-heated sample. Periodic heat shock significantly upregulated both heat shock proteins (HSP70 and HSP27) in differentiated MC3T3-E1 cells. The results of this study demonstrated that periodically heat applied especially two times a day was better approach for osteogenic differentiation. Hence, this work provides a define temperature and time schedule for the development of a clinical heating device in future for early bone regeneration during the postsurgical period.

High Glucose Enhances the Odonto/Osteogenic Differentiation of Stem Cells from Apical Papilla via NF-KappaB Signaling Pathway. Biomed Res Int. 2019;2019:5068258. [PMID: 31080819 PMCID: PMC6476152 DOI: 10.1155/2019/5068258]

Objective

The transport and metabolism of glucose are important during mammalian development. High glucose can mediate the biological characteristics of mesenchymal stem cells (MSCs). However, the role of high glucose in the odonto/osteogenic differentiation of stem cells from apical papilla (SCAPs) is unclear.

Materials and Methods

SCAPs were isolated and identified in vitro. Then, SCAPs were cultured in normal α-MEM and high glucose α-MEM separately. MTT assay was applied to observe the proliferation of SCAPs. ALP activity, alizarin red staining, real-time RT-PCR, and western blot were used to detect the odonto/osteogenic capacity of SCAPs as well as the participation of NF-κB pathway.

Results

SCAPs in 25mmol/L glucose group expressed the maximum proteins of RUNX2 and ALP as compared with those in 5, 10, and 15 mmol/L groups. MTT assay showed that 25 mmol/L glucose suppressed the proliferation of SCAPs. ALP assay, alizarin red staining, real-time RT-PCR, and western blot showed 25 mmol/L high glucose can obviously enhance the odonto/osteogenic capacity of SCAPs. Moreover, the NF-κB pathway was activated in 25mmol/L glucose-treated SCAPs and the odonto/osteogenic differentiation was inhibited following the inhibition of NF-κB signaling pathway.

Conclusions

High glucose can enhance the odonto/osteogenic capacity of SCAPs via NF-κB pathway.

Sal B targets TAZ to facilitate osteogenesis and reduce adipogenesis through MEK-ERK pathway

Salvianolic acid B (Sal B), a major bioactive component of Chinese herb, was identified as a mediator for bone metabolism recently. The aim of this study is to investigate the underlying mechanisms by which Sal B regulates osteogenesis and adipogenesis. We used MC3T3-E1 and 3T3-L1 as the study model to explore the changes of cell differentiation induced by Sal B. The results indicated that Sal B at different concentrations had no obvious toxicity effects on cell proliferation during differentiation. Furthermore, Sal B facilitated osteogenesis but inhibited adipogenesis by increasing the expression of transcriptional co-activator with PDZ-binding motif (TAZ). Accordingly, TAZ knock-down offset the effects of Sal B on cell differentiation into osteoblasts or adipocytes. Notably, the Sal B induced up-expression of TAZ was blocked by U0126 (the MEK-ERK inhibitor), rather than LY294002 (the PI3K-Akt inhibitor). Moreover, Sal B increased the p-ERK/ERK ratio to regulate the TAZ expression as well as the cell differentiation. In summary, this study suggests for the first time that Sal B targets TAZ to facilitate osteogenesis and reduce adipogenesis by activating MEK-ERK signalling pathway, which provides evidence for Sal B to be used as a potential therapeutic agent for the management of bone diseases.

The Potential of Different Origin Stem Cells in Modulating Oral Bone Regeneration Processes

Tissue engineering has gained much momentum since the implementation of stem cell isolation and manipulation for regenerative purposes. Despite significant technical improvements, researchers still have to decide which strategy (which type of stem cell) is the most suitable for their specific purpose. Therefore, this short review discusses the advantages and disadvantages of the three main categories of stem cells: embryonic stem cells, mesenchymal stem cells and induced pluripotent stem cells in the context of bone regeneration for dentistry-associated conditions. Importantly, when deciding upon the right strategy, the selection needs to be made in concordance with the morbidity and the life-threatening level of the condition in discussion. Therefore, even when a specific type of stem cell holds several advantages over others, their availability, invasiveness of the collection method and ethical standards become deciding parameters.

IRS-1 increases TAZ expression and promotes osteogenic differentiation in rat bone marrow mesenchymal stem cells

Whether insulin receptor substrate 1 (IRS-1) inhibits or promotes the osteogenic proliferation and differentiation in vitro remains controversial. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in the osteogenesis of bone marrow mesenchymal stem cells (BMSCs), and strongly activates the expression of the osteogenic differentiation markers. In this study, we found that IRS-1 and TAZ followed similar increasing expression patterns at the early stage of osteogenic differentiation. Knocking down IRS-1 decreased the TAZ, RUNX2 and OCN expression, and overexpressing IRS induced the upregulation of the TAZ, RUNX2 and OCN expression. Furthermore, our results showed that it was LY294002 (the PI3K-Akt inhibitor), other than UO126 (the MEK-ERK inhibitor), that inhibited the IRS-1 induced upregulation of TAZ expression. Additionally, SiTAZ blocked the cell proliferation in G1 during the osteogenic differentiation of BMSCs. Taken together, we provided evidence to demonstrate that IRS-1 gene modification facilitates the osteogenic differentiation of rat BMSCs by increasing TAZ expression through the PI3K-Akt signaling pathway.This article has an associated First Person interview with the first author of the paper.

MicroRNA‑92a overexpression promotes the osteogenic differentiation of bone mesenchymal stem cells by impeding Smad6‑mediated runt‑related transcription factor 2 degradation

Bone mesenchymal stem cells (BMSCs) are an important source of stem cells for tissue repair and regeneration; therefore, understanding the mechanisms that regulate stem cell differentiation in a specific lineage is critical. Runt‑related transcription factor 2 (Runx2) is a bone‑specific transcription factor that serves an important role in promoting osteogenic differentiation. However, Runx2 protein levels are regulated by the ubiquitin‑proteasome pathway. Previous research has identified that Smad6 can interact with Runx2 and enhance Smurf1‑induced Runx2 degradation in a ubiquitin‑proteasome‑dependent manner. Bioinformatics analysis demonstrated that miR‑92a can target Smad6. To characterize the regulatory effect of miR‑92a on osteogenic differentiation of BMSCs and assess the interactive association between Smad6 and miR‑92a, BMSCs were obtained from mice and miR‑92a or Smad6 overexpression vectors were constructed. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blots were used to analyze the expression of miR‑92a and Smad6, and the luciferase reporter assay was used to examine the interaction between miR‑92a and Smad6. BMSCs were induced in osteogenic differentiation media for 21 days. The alkaline phosphatase activity was assessed and Alizarin Red histochemical staining was also performed. The results suggested that the expression of miR‑92a suppressed Smad6‑mediated Runx2 degradation by direct integration with the 3'‑UTR of Smad6 mRNA, which was confirmed by a luciferase reporter assay. In addition, the expression of miR‑92a promoted the osteogenic differentiation of BMSCs. However, the regulatory effect of miR‑92a was inhibited by overexpression of Smad6. Taken together, the results suggest that miR‑92a expression inhibits the osteogenic differentiation of BMSCs by targeting Smad6.

Low oxygen tension modulates the osteogenic differentiation of mouse embryonic stem cells

This study examined the effects of low oxygen tension on the osteogenic differentiation of embryonic stem cells (ESCs) in a three-dimensional culture system. The high expression levels of hypoxia-related proteins hypoxia-inducible factor-1α and vascular endothelial growth factor were first validated in ESCs subjected to hypoxic conditions compared with normoxic controls. The osteogenic differentiation of hypoxic ESCs with either osteogenic or osteogenic factor-free media was subsequently evaluated by measuring alkaline phosphatase activity, intracellular calcium levels, matrix mineralization, and the protein levels of osteogenic markers Runt-related transcription factor 2 and osterix. We confirmed that hypoxia significantly stimulated ESC osteogenic activity; the strongest stimulation of ESC osteogenesis was exerted when cells were grown in osteogenic media. To identify differentially expressed genes associated with hypoxia-induced ESC differentiation, we performed microarray analysis of ESCs cultured in osteogenic media under normoxic and hypoxic conditions. This study demonstrated that differences in oxygen tension induced the differential expression of genes known to play roles in such processes as skeletal system development and signaling pathways for bone morphogenetic protein, Wnt, Notch, mitogen-activated protein kinase, and integrin. These findings reveal the effects of low oxygen tension on osteogenic progression in ESCs and provide insight into the molecular pathways that regulate ESC differentiation following exposure to hypoxia.

Attributes of Bio-Oss® and Moa-Bone® graft materials in a pilot study using the sheep maxillary sinus model

BACKGROUND AND OBJECTIVE

The aim of this pilot study was to characterize surface morphology and to evaluate resorption and osseous healing of two deproteinated bovine bone graft materials after sinus grafting in a large animal model.

MATERIAL AND METHODS

Surfaces of a novel particulate bovine bone graft, Moa-Bone^® were compared with Bio-Oss^® using scanning electron microscopy. Six sheep then had maxillary sinus grafting bilaterally, covered with BioGide^® . Grafted maxillae were harvested after 4, 6 and 12 weeks. Healing was described for half of each site using resin-embedded ground sections. For the other half, paraffin-embedded sections were examined using tartrate resistant acid phosphatase staining for osteoclast activity, runt-related transcription factor2 immunohistochemistry for pre-osteoblasts and osteoblasts and proliferating cell nuclear antigen for proliferative cells.

RESULTS

Moa-Bone^® had a smoother, more porous fibrous structure with minimal globular particles compared with Bio-Oss^® . After 4 weeks, woven bone formed on both grafts and the Moa-Bone^® particles also showed signs of resorption. After 12 weeks, Moa-Bone^® continued to be resorbed, however Bio-Oss^® did not; both grafts were surrounded by maturing lamellar bone. Moa-Bone^® was associated with earlier evidence of runt-related transcription factor 2-positive cells. Moa-Bone^® but not Bio-Oss^® was associated with strong tartrate resistant acid phosphatase-positive osteoclasts on the graft surface within resorption lacunae at both 4 and 6 weeks post-grafting.

CONCLUSION

Both materials supported osseous healing and maturation without inflammation. Moa-Bone^® showed marked osteoclast activity after 4 and 6 weeks and demonstrated positive attributes for grafting, if complete remodeling of the graft within the site is desired. Further optimization of Moa-Bone^® for maxillofacial applications is warranted.

Comparative Study of Osteogenic Activity of Multilayers Made of Synthetic and Biogenic Polyelectrolytes

Polyelectrolyte multilayer (PEM) coatings on biomaterials are applied to tailor adhesion, growth, and function of cells on biomedical implants. Here, biogenic and synthetic polyelectrolytes (PEL) are used for layer-by-layer assembly to study the osteogenic activity of PEM with human osteosarcoma MG-63 cells in a comparative manner. Formation of PEM is achieved with biogenic PEL fibrinogen (FBG) and poly-l-lysine (PLL) as well as biotinylated chondroitin sulfate (BCS) and avidin (AVI), while poly(allylamine hydrochloride) (PAH) and polystyrene sulfonate (PSS) represent a fully synthetic PEM used as a reference system here. Surface plasmon resonance measurements show highest layer mass for FBG/PLL and similar for PSS/PAH and BCS/AVI systems, while water contact angle and zeta potential measurements indicate larger differences for PSS/PAH and FBG/PLL but not for BCS/AVI multilayers. All PEM systems support cell adhesion and growth and promote osteogenic differentiation as well. However, FBG/PLL layers are superior regarding MG-63 cell adhesion during short-term culture, while the BCS/AVI system increases alkaline phosphatase activity in long-term culture. Particularly, a multilayer system based on affinity interaction like BCS/AVI may be useful for controlled presentation of biotinylated growth factors to promote growth and differentiation of cells for biomedical applications.

LRG1 promotes proliferation and inhibits apoptosis in colorectal cancer cells via RUNX1 activation

Leucine-rich-alpha-2-glycoprotein 1 (LRG1) has been shown to be involved in various human malignancies. Whether it plays a role in colorectal cancer (CRC) development remains unclear. Here, we investigated whether and through what mechanism LRG1 functions in human CRC cells. The plasma level of LRG1 was significantly increased in CRC patients, but it was remarkably decreased in patients with resected colorectal cancers. Meanwhile, both mRNA and protein levels of LRG1 were remarkable overexpressed in CRC tissues than normal tissues. The knockdown of LRG1 significantly inhibited cell proliferation, induced cell cycle arrest at the G0/G1 phase, and promoted apoptosis in SW480 and HCT116 cells in vitro. In addition, LRG1 silencing led to the downregulation of the levels of key cell cycle factors, such as cyclin D1, B, and E and anti-apoptotic B-cell lymphoma-2(Bcl-2). However, it up-regulated the expression of pro-apoptotic Bax and cleaved caspase-3. Furthermore, RUNX1 could be induced by LRG1 in a concentration-dependent manner, while the knockdown of RUNX1 blocked the promotion of the proliferation and inhibition of apoptosis induced by LRG1. Collectively, these findings indicate that LRG1 plays a crucial role in the proliferation and apoptosis of CRC by regulating RUNX1 expression. Thus, LRG1 may be a potential detection biomarker as well as a marker for monitoring recurrence and therapeutic target for CRC.