Characterization of adhesion and differentiation markers of osteogenic marrow stromal cells

Evaluation of the Osteogenic Potential of Different Scaffolds Embedded with Human Stem Cells Originated from Schneiderian Membrane: An In Vitro Study

BACKGROUND

Novel treatments for bone defects, particularly in patients with poor regenerative capacity, are based on bone tissue engineering strategies which include mesenchymal stem cells (MSCs), bioactive factors, and convenient scaffold supports.

OBJECTIVE

In this study, we aimed at comparing the potential for different scaffolds to induce osteogenic differentiation of human maxillary Schneiderian sinus membrane- (hMSSM-) derived cells. Methods. hMSSM-derived cells were seeded on gelatin, collagen, or Hydroxyapatite β-Tricalcium phosphate-Fibrin (Haβ-TCP-Fibrin) scaffolds. Cell viability was determined using an MTT assay. Alizarin red staining method, Alkaline phosphatase (ALP) activity assay, and quantitative real-time PCR analysis were performed to assess hMSSM-derived cells osteogenic differentiation.

RESULTS

Cell viability, calcium deposition, ALP activity, and osteoblastic markers transcription levels were most striking in gelatin scaffold-embedded hMSSM-derived cells.

CONCLUSION

Our findings suggest a promising potential for gelatin-hMSSM-derived cell construct for treating bone defects.

Three-dimensional in vitro modeling of malignant bone disease recapitulates experimentally accessible mechanisms of osteoinhibition

Malignant bone disease (MBD) occurs when tumors establish in bone, causing catastrophic tissue damage as a result of accelerated bone destruction and inhibition of repair. The resultant so-called osteolytic lesions (OL) take the form of tumor-filled cavities in bone that cause pain, fractures, and associated morbidity. Furthermore, the OL microenvironment can support survival of tumor cells and resistance to chemotherapy. Therefore, a deeper understanding of OL formation and MBD progression is imperative for the development of future therapeutic strategies. Herein, we describe a novel in vitro platform to study bone-tumor interactions based on three-dimensional co-culture of osteogenically enhanced human mesenchymal stem cells (OEhMSCs) in a rotating wall vessel bioreactor (RWV) while attached to micro-carrier beads coated with extracellular matrix (ECM) composed of factors found in anabolic bone tissue. Osteoinhibition was recapitulated in this model by co-culturing the OEhMSCs with a bone-tumor cell line (MOSJ-Dkk1) that secretes the canonical Wnt (cWnt) inhibitor Dkk-1, a tumor-borne osteoinhibitory factor widely associated with several forms of MBD, or intact tumor fragments from Dkk-1 positive patient-derived xenografts (PDX). Using the model, we observed that depending on the conditions of growth, tumor cells can biochemically inhibit osteogenesis by disrupting cWnt activity in OEhMSCs, while simultaneously co-engrafting with OEhMSCs, displacing them from the niche, perturbing their activity, and promoting cell death. In the absence of detectable co-engraftment with OEhMSCs, Dkk-1 positive PDX fragments had the capacity to enhance OEhMSC proliferation while inhibiting their osteogenic differentiation. The model described has the capacity to provide new and quantifiable insights into the multiple pathological mechanisms of MBD that are not readily measured using monolayer culture or animal models.

Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells Using Microbubbles and Low Intensity Pulsed Ultrasound on 3D Printed Scaffolds

Lipid-coated microbubbles, clinically approved as contrast enhancing agents for ultrasound imaging, are investigated for the first time for their possible applications in bone tissue engineering. Effects of microbubbles (average diameter 1.1 µm) coated by a mixture of lipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000], and 1,2-dipalmitoyl-3-trimethylmmonium-propane) in the presence of low intensity pulsed ultrasound (LIPUS) on human mesenchymal stem cells seeded on 3D printed poly(lactic acid) porous scaffolds are investigated. LIPUS stimulation (30 mW cm^-2 , 1.5 MHz, 20% duty cycle) for 3 min a day with 0.5% v/v microbubbles results in a significant increase in proliferation (up to 19.3%) when compared to control after 1, 3, and 5 d. A 3-week osteogenic differentiation study shows a significant increase in total protein content (up to 27.5%), calcium deposition (up to 4.3%), and alkaline phosphatase activity (up to 43.1%) initiated by LIPUS with and without the presence of microbubbles. The microbubbles are found to remain stable during exposure, and their sustained oscillations demonstrably help focus the LIPUS energy toward enhanced cellular response. Integrating LIPUS and microbubbles promises to be a novel and effective strategy for bone tissue engineering and regeneration therapies.

Improved vasculogenesis and bone matrix formation through coculture of endothelial cells and stem cells in tissue-specific methacryloyl gelatin-based hydrogels

The coculture of osteogenic and angiogenic cells and the resulting paracrine signaling via soluble factors are supposed to be crucial for successfully engineering vascularized bone tissue equivalents. In this study, a coculture system combining primary human adipose-derived stem cells (hASCs) and primary human dermal microvascular endothelial cells (HDMECs) within two types of hydrogels based on methacryloyl-modified gelatin (GM) as three-dimensional scaffolds was examined for its support of tissue specific cell functions. HDMECs, together with hASCs as supporting cells, were encapsulated in soft GM gels and were indirectly cocultured with hASCs encapsulated in stiffer GM hydrogels additionally containing methacrylate-modified hyaluronic acid and hydroxyapatite particles. After 14 days, the hASC in the stiffer gels (constituting the "bone gels") expressed matrix proteins like collagen type I and fibronectin, as well as bone-specific proteins osteopontin and alkaline phosphatase. After 14 days of coculture with HDMEC-laden hydrogels, the viscoelastic properties of the bone gels were significantly higher compared with the gels in monoculture. Within the soft vascularization gels, the formed capillary-like networks were significantly longer after 14 days of coculture than the structures in the control gels. In addition, the stability as well as the complexity of the vascular networks was significantly increased by coculture. We discussed and concluded that osteogenic and angiogenic signals from the culture media as well as from cocultured cell types, and tissue-specific hydrogel composition all contribute to stimulate the interplay between osteogenesis and angiogenesis in vitro and are a basis for engineering vascularized bone.

Dental pulp stem cells and osteogenesis: an update

Dental pulp stem cells constitute an attractive source of multipotent mesenchymal stem cells owing to their high proliferation rate and multilineage differentiation potential. Osteogenesis is initiated by osteoblasts, which originate from mesenchymal stem cells. These cells express specific surface antigens that disappear gradually during osteodifferentiation. In parallel, the appearance of characteristic markers, including alkaline phosphatase, collagen type I, osteocalcin and osteopontin characterize the osteoblastic phenotype of dental pulp stem cells. This review will shed the light on the osteogenic differentiation potential of dental pulp stem cells and explore the culture medium components, and markers associated with osteodifferentiation of these cells.

The effect of pulsed electromagnetic field exposure on osteoinduction of human mesenchymal stem cells cultured on nano-TiO2 surfaces

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) are considered a great promise in the repair and regeneration of bone. Considerable efforts have been oriented towards uncovering the best strategy to promote stem cells osteogenic differentiation. In previous studies, hBM-MSCs exposed to physical stimuli such as pulsed electromagnetic fields (PEMFs) or directly seeded on nanostructured titanium surfaces (TiO₂) were shown to improve their differentiation to osteoblasts in osteogenic condition. In the present study, the effect of a daily PEMF-exposure on osteogenic differentiation of hBM-MSCs seeded onto nanostructured TiO₂ (with clusters under 100 nm of dimension) was investigated. TiO₂-seeded cells were exposed to PEMF (magnetic field intensity: 2 mT; intensity of induced electric field: 5 mV; frequency: 75 Hz) and examined in terms of cell physiology modifications and osteogenic differentiation. Results showed that PEMF exposure affected TiO₂-seeded cells osteogenesis by interfering with selective calcium-related osteogenic pathways, and greatly enhanced hBM-MSCs osteogenic features such as the expression of early/late osteogenic genes and protein production (e.g., ALP, COL-I, osteocalcin and osteopontin) and ALP activity. Finally, PEMF-treated cells resulted to secrete into conditioned media higher amounts of BMP-2, DCN and COL-I than untreated cell cultures. These findings confirm once more the osteoinductive potential of PEMF, suggesting that its combination with TiO₂ nanostructured surface might be a great option in bone tissue engineering applications.

Inverse Opal Scaffolds with Gradations in Mineral Content for Spatial Control of Osteogenesis

The design and fabrication of inverse opal scaffolds with gradations in mineral content to achieve spatial control of osteogenesis are described. The gradient in mineral content is established via the diffusion-limited transport of hydroxyapatite nanoparticles in a closely packed lattice of gelatin microbeads. The mineral-graded scaffold has an array of uniform pores and interconnected windows to facilitate efficient transport of nutrients and metabolic wastes, ensuring high cell viability. The graded distribution of mineral content can provide biochemical and mechanical cues for spatially regulating the osteogenic differentiation of adipose-derived stromal cells. This new class of scaffolds holds promise for engineering the interfaces between mineralized and unmineralized tissues.

Osteogenic Differentiation of Human Mesenchymal Stromal Cells on Surface-Modified Titanium Alloys for Orthopedic and Dental Implants

Purpose

Surface properties of titanium alloys, used for orthopedic and dental applications, are known to affect implant interactions with host tissues. Osteointegration, bone growth and remodeling in the area surrounding the implants can be implemented by specific biomimetic treatments; these allow the preparation of micro/nanostructured titanium surfaces with a thickened oxide layer, doped with calcium and phosphorus ions. We have challenged these experimental titanium alloys with primary human bone marrow stromal cells to compare the osteogenic differentiation outcomes of the cells once they are seeded onto the modified surfaces, thus simulating a prosthetic device-biological interface of clinical relevance.

Methods

A specific anodic spark discharge was the biomimetic treatment of choice, providing experimental titanium disks treated with different alkali etching approaches. The disks, checked by electron microscopy and spectroscopy, were subsequently used as substrates for the proliferation and osteogenic differentiation of human cells. Expression of markers of the osteogenic lineage was assessed by means of qualitative and quantitative PCR, by cytochemistry, immunohistochemistry Western blot and matrix metalloprotease activity analyses.

Results

Metal surfaces were initially less permissive for cell growth. Untreated control substrates were less efficient in sustaining mineralized matrix deposition upon osteogenic induction of the cells. Interestingly, bone sialo protein and matrix metalloprotease 2 levels were enhanced on experimental metals compared to control surfaces, particularly for titanium oxide coatings etched with KOH.

Discussion

As a whole, the KOH-modification of titanium surfaces seems to allow the best osteogenic differentiation of human mesenchymal stromal cells, representing a possible plus for future clinical prosthetic applications.

3D printing of pearl/CaSO4 composite scaffolds for bone regeneration

The development of biomaterials with high osteogenic ability for fast osteointegration with a host bone is of great interest. In this study, pearl/CaSO₄ composite scaffolds were fabricated using three-dimensional (3D) printing, followed by a hydration process. The pearl/CaSO₄ scaffolds showed uniform interconnected macropores (∼400 μm), high porosity (∼60%), and enhanced compressive strength. With CaSO₄ scaffolds as a control, the biological properties of the pearl/CaSO₄ scaffolds were evaluated in vitro and in vivo. The results showed that the pearl/CaSO₄ scaffolds possessed a good apatite-forming ability and stimulated the proliferation and differentiation of rat bone mesenchymal stem cells (rBMSCs), as well as giving a better expression of related osteogenic genes. Importantly, micro-computed tomography and histology of the critical-sized rabbit femoral condyle defects implanted with the scaffolds illustrated the osteogenic capacity of the pearl/CaSO₄ scaffolds. New bone was observed within 8 weeks. The bone-implant contact index was significantly higher for the pearl/CaSO₄ scaffolds implant than for the CaSO₄ scaffolds implant, indicating that the pearl/CaSO₄ scaffolds would be promising implants for bone regeneration.

The Osteogenic Differentiation Effect of the FN Type 10-Peptide Amphiphile on PCL Fiber

The fibronectin type 10-peptide amphiphile (FNIII10-PA) was previously genetically engineered and showed osteogenic differentiation activity on rat bone marrow stem cells (rBMSCs). In this study, we investigated whether FNIII10-PA demonstrated cellular activity on polycaprolactone (PCL) fibers. FNIII10-PA significantly increased protein production and cell adhesion activity on PCL fibers in a dose-dependent manner. In cell proliferation results, there was no effect on cell proliferation activity by FNIII10-PA; however, FNIII10-PA induced the osteogenic differentiation of MC3T3-E1 cells via upregulation of bone sialoprotein (BSP), collagen type I (Col I), osteocalcin (OC), osteopontin (OPN), and runt-related transcription factor 2 (Runx2) mitochondrial RNA (mRNA) levels; it did not increase the alkaline phosphatase (ALP) mRNA level. These results indicate that FNIII10-PA has potential as a new biomaterial for bone tissue engineering applications.

Chitosan composite scaffold combined with bone marrow-derived mesenchymal stem cells for bone regeneration: in vitro and in vivo evaluation

The study aimed to develop a chitosan (CS)-based scaffold for repairing calvarial bone defects. We fabricated composite scaffolds made of CS and bovine-derived xenograft (BDX), characterized their physicochemical properties including pore size and porosity, absorption, degradation, and compressive strength, compared their efficacy to support in vitro proliferation and differentiation of human jaw bone marrow-derived mesenchymal stem cells (hJBMMSCs), and evaluated their bone regeneration capacity in critical-size rat calvarial defects. The CS/BDX (mass ratio of 40:60) composite scaffold with porosity of 46.23% and pore size of 98.23 μm exhibited significantly enhanced compressive strength than the CS scaffold (59.33 ± 4.29 vs. 18.82 ± 2.49 Kpa). The CS/BDX (40:60) scaffold induced better cell attachment and promoted more osteogenic differentiation of hJBMMSCs than the CS scaffold. The CS/BDX (40:60) scaffold seeded with hJBMMSCs was the most effective in supporting new bone formation, as evidenced by better histomorphometry results, larger new bone area, and more obvious mature lamellar bone formation compared to other groups in rat calvarial defects 8 weeks after implantation. These results suggest that CS/BDX composite scaffold combining with hJBMMSCs has the potential for bone defect regeneration.

Efficient in vitro delivery of Noggin siRNA enhances osteoblastogenesis

Several types of serious bone defects would not heal without invasive clinical intervention. One approach to such defects is to enhance the capacity of bone-formation cells. Exogenous bone morphogenetic proteins (BMP) have been utilized to positively regulate matrix mineralization and osteoblastogenesis, however, numerous adverse effects are associated with this approach. Noggin, a potent antagonist of BMPs, is an ideal candidate to target and decrease the need for supraphysiological doses of BMPs. In the current research we report a novel siRNA-mediated gene knock-down strategy to down-regulate Noggin. We utilized a lipid nanoparticle (LNP) delivery strategy in pre-osteoblastic rat cells. In vitro LNP-siRNA treatment caused inconsequential cell toxicity and transfection was achieved in over 85% of cells. Noggin siRNA treatment successfully down-regulated cellular Noggin protein levels and enhanced BMP signal activity which in turn resulted in significantly increased osteoblast differentiation and extracellular matrix mineralization evidenced by histological assessments. Gene expression analysis showed that targeting Noggin specifically in bone cells would not lead to a compensatory effect from other BMP negative regulators such as Gremlin and Chordin. The results from this study support the notion that novel therapeutics targeting Noggin have the clinically relevant potential to enhance bone formation without the need for toxic doses of exogenous BMPs. Such treatments will undeniably provide safe and economical treatments for individuals whose poor bone repair results in permanent morbidity and disability.

An nMgO containing scaffold: Antibacterial activity, degradation properties and cell responses

Bone repair failure caused by implant-related infections is a common and troublesome problem. In this study, an antibacterial scaffold was developed via selective laser sintering with incorporating nano magnesium oxide (nMgO) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The results indicated the scaffold exerted high antibacterial activity. The antibacterial mechanism was that nMgO could cause oxidative damage and mechanical damage to bacteria through the production of reactive oxygen species (ROS) and direct contact action, respectively, which resulted in the damage of their structures and functions. Besides, nMgO significantly increased the compressive properties of the scaffold including strength and modulus, due to its excellent mechanical properties and uniform dispersion in the PHBV matrix. Moreover, the degradation tests indicated nMgO neutralized the acid degradation products of PHBV and benefited the degradation of the scaffold. The cell culture demonstrated that nMgO promoted the cellular adhesion and proliferation, as well as osteogenic differentiation. The present work may open the door to exploring nMgO as a promising antibacterial material for tissue engineering.

Oxidative stress induces imbalance of adipogenic/osteoblastic lineage commitment in mesenchymal stem cells through decreasing SIRT1 functions

With rapidly ageing populations worldwide, the incidence of osteoporosis has reached epidemic proportions. Reactive oxygen species (ROS), a by‐product of oxidative stress and ageing, has been thought to induce osteoporosis by inhibiting osteogenic differentiation of mesenchymal stem cells (MSCs). However, specific mechanisms of how ROS results in alterations on MSC differentiation capacity have been inconsistently reported. We found that H₂O₂, an ROS, simultaneously induced MSC lineage commitment towards adipogenesis and away from osteogenesis at the functional as well as transcriptional level. In addition, H₂O₂ decreased the activities of SIRT1, a histone deacetylase and longevity gene. By silencing and reconstituting SIRT1 in MSCs, we demonstrated that H₂O₂ exerted its disparate effects on adipogenic/osteoblastic lineage commitment mainly through modulating SIRT1 expression levels. Treatment with resveratrol, a SIRT1 agonist, can also reverse this ROS‐induced adipogenesis/osteogenesis lineage imbalance. Moreover, SIRT1 regulation of RUNX2 transcriptional activity was mediated through deacetylation of the ROS‐sensitive transcription factor FOXO3a. Taken together, our data implicate SIRT1 as playing a vital role in ROS‐directed lineage commitment of MSCs by modulating two lineages simultaneously. Our findings on the critical role of SIRT1 in ROS/age‐related perturbations of MSC differentiation capacity highlight this molecule as a target for maintenance of MSC stemness as well as a potential anabolic target in osteoporosis.

Estradiol‑enhanced osteogenesis of rat bone marrow stromal cells is associated with the JNK pathway

Bone marrow stromal cells (BMSCs) can differentiate into osteoblasts. The present study investigated the osteogenic effects of estradiol, as well as the role of the c-Jun N-terminal kinase (JNK) signaling pathway in promoting estradiol-enhanced osteogenesis of rat (r)BMSCs. rBMSCs were treated for 7 days with or without estradiol and further treated with or without the JNK-specific inhibitor SP600125. The role of estrogen during rBMSC osteogenesis was evaluated by alkaline phosphatase activity and mineralized nodule formation using the Gomori method and Alizarin red S staining, respectively. Subsequently, the mRNA expression levels of transforming growth factor-β1 (TGF-β1) and core-binding factor α1 (Cbfα1) were evaluated by reverse transcription-quantitative polymerase chain reaction, and TGF-β1, Cbfα1 and phosphorylated (p)-JNK protein expression was detected by western blotting. All groups treated with SP600125 expressed low levels of TGF-β1 and Cbfα1 mRNA and protein, and low p-JNK protein expression. Compared with the control cells, rBMSCs cultured with estradiol exhibited a significant upregulation in the expression levels of osteogenic genes and proteins. The present study demonstrated that estradiol enhanced osteogenic differentiation of rBMSCs and that the JNK signaling pathway was involved in this process, providing insights into the molecular mechanisms involved in rBMSC osteogenesis upon estradiol stimulation.

HPLC-MS/MS: A potential method to track the in vivo degradation of zein-based biomaterial

Given the inadequacies of existing clinic tracking strategies, such as isotopic tracer techniques, one of the major thrusts in protein-based tissue engineering substitutes prior to use in clinic is to develop a safe technique that can effectively track their degradation in vivo. Keeping in view the possible application of a natural polymer, zein as a novel bone substitute, with the advantages of good bio-compatibility, bio-degradability and outstanding mechanical properties, we attempted here to construct a HPLC-MS/MS method to track the in vivo degradation of zein porous scaffold. Histological observation and immunohistochemistry analysis using the intramuscular implantation model of rats clearly indicated that zein porous scaffold has certain osteoinductive ability. More importantly, HPLC-MS/MS detected the changes of amino acids levels in plasma and different organs after the implantation of scaffolds. With these findings, it could be concluded that HPLC-MS/MS might be a potential method to track the in vivo degradation of protein-based tissue engineering substitutes. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 606-613, 2018.

Stem cell-mediated functionalization of titanium implants

Prosthetic implants are used daily to treat edentulous people and to restore mobility in patients affected by skeletal defects. Titanium (Ti) is the material of choice in prosthetics, because it can form a stable bond with the surrounding bone following implantation-a process known as osseointegration. Yet, full integration of prosthetic implants takes time, and fails in clinical situations characterized by limited bone quantity and/or compromised regenerative capacity, and in at-risk patients. Intense research efforts are thus made to develop new implants that are cost-effective, safe, and suited to every patient in each clinical situation. In this study, we tested the possibility to functionalize Ti implants using stem cells. Human induced pluripotent stem cell-derived mesenchymal progenitor (iPSC-MP) cells were cultured on Ti model disks for 2 weeks in osteogenic conditions. Samples were then treated using four different decellularization methods to wash off the cells and expose the matrix. The functionalized disks were finally sterilized and seeded with fresh human iPSC-MP cells to study the effect of stem cell-mediated surface functionalization on cell behavior. The results show that different decellularization methods produce diverse surface modifications, and that these modifications promote proliferation of human iPSC-MP cells, affect the expression of genes involved in development and differentiation, and stimulate the release of alkaline phosphatase. Cell-mediated functionalization represents an attractive strategy to modify the surface of prosthetic implants with cues of biological relevance, and opens unprecedented possibilities for development of new devices with enhanced therapeutic potential.

Redifferentiation of aged human articular chondrocytes by combining bone morphogenetic protein-2 and melanoma inhibitory activity protein in 3D-culture

Melanoma inhibitory activity (MIA) affects the differentiation to hyaline cartilage and can inhibit the osteogenic potential of bone morphogenetic protein (BMP)-2 in mesenchymal stem cells (MSC). The aim of this study was to investigate if MIA also inhibits the osteogenic potential of BMP-2 in human articular chondrocytes during redifferentiation, which may lead to a higher grade of differentiation without calcification. HAC of four female patients (mean age: 73.75 ±6.98) were seeded into 3D culture for 28 days; after adding the recombinant proteins, four groups were formed (Control, BMP-2, MIA, BMP-2+MIA). Samples were analysed for gene expression, glycosaminoglycan (GAG) content and histology on day 0, 14 and 28. Collagen type 2 (COL2A1) was significantly increased in the BMP-2 containing groups on day 28; BMP-2 (100-fold, p = 0.001), BMP-2+MIA (65-fold, p = 0.009) and similar to the level of native cartilage. Higher aggrecan (Agg) levels were present in the BMP-2 (3-fold, p = 0.007) and BMP-2+MIA (4-fold, p = 0.002) group after 14 days and in the BMP-2 (9-fold, p = 0.001) group after 28 days. Collagen type 10 (COL10A1) was increased in the BMP-2 containing groups (6-fold, p = 0.006) but these levels were significantly below native cartilage. Alkaline phosphatase (ALP), collagen type 1 (COL1A1) and the glycosaminoglycan (GAG) content did not reveal any relevant differences between groups. BMP-2 is a potent inducer for differentiation of HAC. A significant enhancement of this effect in combination with MIA could not be observed. Furthermore no significant reduction of osteogenic markers during re-differentiation of chondrocytes was present combining BMP-2 and MIA.

A novel akermanite/poly (lactic-co-glycolic acid) porous composite scaffold fabricated via a solvent casting-particulate leaching method improved by solvent self-proliferating process

Desirable scaffolds for tissue engineering should be biodegradable carriers to supply suitable microenvironments mimicked the extracellular matrices for desired cellular interactions and to provide supports for the formation of new tissues. In this work, a kind of slightly soluble bioactive ceramic akermanite (AKT) powders were aboratively selected and introduced in the PLGA matrix, a novel l-lactide modified AKT/poly (lactic-co-glycolic acid) (m-AKT/PLGA) composite scaffold was fabricated via a solvent casting-particulate leaching method improved by solvent self-proliferating process. The effects of m-AKT contents on properties of composite scaffolds and on MC3T3-E1 cellular behaviors in vitro have been primarily investigated. The fabricated scaffolds exhibited three-dimensional porous networks, in which homogenously distributed cavities in size of 300–400 μm were interconnected by some smaller holes in a size of 100–200 μm. Meanwhile, the mechanical structure of scaffolds was reinforced by the introduction of m-AKT. Moreover, alkaline ionic products released by m-AKT could neutralize the acidic degradation products of PLGA, and the apatite-mineralization ability of scaffolds could be largely improved. More valuably, significant promotions on adhesion, proliferation, and differentiation of MC3T3-E1 have been observed, which implied the calcium, magnesium and especially silidous ions released sustainably from composite scaffolds could regulate the behaviors of osteogenesis-related cells.

Investigating the effect of fibulin-1 on the differentiation of human nasal inferior turbinate-derived mesenchymal stem cells into osteoblasts

Many extracellular matrix proteins have positive influences on the adhesion, proliferation, and differentiation of stem cells into specific cell linages. Fibulin-1 (FBLN1), a member of a growing family of extracellular glycoproteins, contributes to the structure of the extracellular matrix. Here, we investigated the effect of FBLN1 on the ability of human nasal inferior turbinate-derived mesenchymal stem cells (hTMSCs) to undergo osteogenic differentiation. After we generated recombinant FBLN1, the characteristics of FBLN1-treated hTMSCs were evaluated using MTT assay, ALP and mineralization activities, and quantitative real-time PCR. FBLN1 significantly enhanced the adhesion activity (p < 0.001) and proliferation of hTMSCs (p < 0.05). The ALP and mineralization activities of cells were dramatically increased (p < 0.01) after 9 and 12 days of FBLN1 treatment, respectively. This indicated the ability of FBLN1 to induce hTMSCs to differentiate into osteoblasts. Furthermore, increasing the mRNA levels of osteogenic marker genes, such as a transcriptional coactivator with a PDZ-binding motif (TAZ), alkaline phosphatase (ALP), collagen type I (Col I), and osteocalcin (OCN), improved bone repair and regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2291-2298, 2017.

Scaffolds containing chitosan, gelatin and graphene oxide for bone tissue regeneration in vitro and in vivo

Critical-sized bone defects are augmented with cell free and cell loaded constructs to bridge bone defects. Improving the properties of three-dimensional scaffolds with multiple polymers and others is of growing interest in recent decades. Chitosan (CS), a natural biopolymer has limitations for its use in bone regeneration, and its properties can be enhanced with other materials. In the present study, the composite scaffolds containing CS, gelatin (Gn) and graphene oxide (GO) were fabricated through freeze-drying. These scaffolds (GO/CS/Gn) were characterized by the SEM, Raman spectra, FT-IR, EDS, swelling, biodegradation, protein adsorption and biomineralization studies. The inclusion of GO in the CS/Gn scaffolds showed better physico-chemical properties. The GO/CS/Gn scaffolds were cyto-friendly to rat osteoprogenitor cells, and they promoted differentiation of mouse mesenchymal stem cells into osteoblasts. The scaffolds also accelerated bridging of the rat tibial bone defect with increased collagen deposition in vivo. Hence, these results strongly suggested the potential nature of GO/CS/Gn scaffolds for their application in bone tissue regeneration.

Tantalum nitride coatings prepared by magnetron sputtering to improve the bioactivity and osteogenic activity for titanium alloy implants

TaN film has a positive effect on the biocompatibility and osteoinductive ability of Ti6Al4V-based implants.

Assessment of the Role of Noni (Morinda citrifolia) Juice for Inducing Osteoblast Differentiation in Isolated Rat Bone Marrow Derived Mesenchymal Stem Cells

Background and Objectives

Morinda citrifolia (Noni), an important traditional medicinal plant still used in patients with bone fractures or dislocation to promote connective tissue repair and to reduce inflammation. However, the effects of Noni on bone metabolism and whether it influences the osteogenic differentiation is yet to be clarified. In this study, we investigated the effect of Morinda citrifolia (Noni) juice on the proliferation rate of rat bone marrow derived mesenchymal stem cells (BMSC) and the osteoblastic differentiation as shown by alkaline phosphatase (ALP), Runt-related transcription factor 2 (Runx2) and osteocalcin (OCN) mRNA expression in vitro.

Methods and Results

Treatment with 200 μg/ml Noni juice enhanced the proliferation rate of the BMSC and also upregulated the osteogenic differentiation marker genes ALP and OCN, and Runx2 measured by RTPCR. Consistent with these results collagen scaffolds implanted in vivo, which were loaded with BMSC pre-exposed to Noni, showed increased bone density measured by computed tomography and histological analysis revealed neo-angiogenesis for bone formation.

Conclusions

These results suggest that Noni stimulates osteoblastogenesis and can be used as adjuvant natural medicine for bone diseases such as osteoporosis.

Surface guidance of stem cell behavior: Chemically tailored co-presentation of integrin-binding peptides stimulates osteogenic differentiation in vitro and bone formation in vivo

Surface modification stands out as a versatile technique to create instructive biomaterials that are able to actively direct stem cell fate. Chemical functionalization of titanium has been used in this work to stimulate the differentiation of human mesenchymal stem cells (hMSCs) into the osteoblastic lineage, by covalently anchoring a synthetic double-branched molecule (PTF) to the metal that allows a finely controlled presentation of peptidic motifs. In detail, the effect of the RGD adhesive peptide and its synergy motif PHSRN is studied, comparing a random distribution of the two peptides with the chemically-tailored disposition within the custom made synthetic platform, which mimics the interspacing between the motifs observed in fibronectin. Contact angle measurement and XPS analysis are used to prove the efficiency of functionalization. We demonstrate that, by rationally designing ligands, stem cell response can be efficiently guided towards the osteogenic phenotype: In vitro, PTF-functionalized surfaces support hMSCs adhesion, with higher cell area and formation of focal contacts, expression of the integrin receptor α5β1 and the osteogenic marker Runx2, and deposition a highly mineralized matrix, reaching values of mineralization comparable to fibronectin. Our strategy is also demonstrated to be efficient in promoting new bone growth in vivo in a rat calvarial defect. These results highlight the efficacy of chemical control over the presentation of bioactive peptides; such systems may be used to engineer bioactive surfaces with improved osseointegrative properties, or can be easily tuned to generate multi-functional coatings requiring a tailored disposition of the peptidic motifs.

STATEMENT OF SIGNIFICANCE

Organic coatings have been proposed as a solution to foster osseointegration of orthopedic implants. Among them, extracellular matrix-derived peptide motifs are an interesting biomimetic strategy to harness cell-surface interactions. Nonetheless, the combination of multiple peptide motifs in a controlled manner is essential to achieve receptor specificity and fully exploit the potentiality of synthetic peptides. Herein, we covalently graft to titanium a double branched molecule to guide stem cell fate in vitro and generate an osseoinductive titanium surface in vivo. Such synthetic ligand allows for the simultaneous presentation of two bioactive motifs, thus is ideal to test the effect of synergic sequences, such as RGD and PHSRN, and is a clear example of the versatility and feasibility of rationally designed biomolecules.

Mussel-inspired alginate gel promoting the osteogenic differentiation of mesenchymal stem cells and anti-infection

Alginate hydrogels have been used in cell encapsulation for many years but a prevalent issue with pure alginates is that they are unable to provide enough bioactive properties to interact with mammalian cells. This paper discusses the modification of alginate with mussel-inspired dopamine for cell loading and anti-infection. Mouse bone marrow stem cells were immobilized into alginate and alginate-dopamine beads and fibers. Through live-dead and MTT assay, alginates modified by dopamine promoted cell viability and proliferation. In vitro cell differentiation results showed that such an alginate-dopamine gel can promote the osteogenic differentiation of mesenchymal stem cell after PCR and ALP assays. In addition to that, the adhesive prosperities of dopamine allowed for coating the surface of alginate-dopamine gel with silver nanoparticles, which provided the gel with significant antibacterial characteristics. Overall, these results demonstrate that a dopamine-modified alginate gel can be a great tool for cell encapsulation to promote cell proliferation and can be applied to bone regeneration, especially in contaminated bone defects.

A Novel Nanosilver/Nanosilica Hydrogel for Bone Regeneration in Infected Bone Defects

Treating bone defects in the presence of infection is a formidable clinical challenge. The use of a biomaterial with the dual function of bone regeneration and infection control is a novel therapeutic approach to this problem. In this study, we fabricated an innovative, dual-function biocomposite hydrogel containing nanosilver and nanosilica (nAg/nSiO2) particles and evaluated its characteristics using FT-IR, SEM, swelling ratio, and stiffness assays. The in vitro antibacterial analysis showed that this nAg/nSiO2 hydrogel inhibited both Gram-positive and Gram-negative bacteria. In addition, this nontoxic material could promote osteogenic differentiation of rat bone marrow stromal cells (BMSCs). We then created infected bone defects in rat calvaria in order to evaluate the function of the hydrogel in vivo. The hydrogel demonstrated effective antibacterial ability while promoting bone regeneration in these defects. Our results indicate that this nAg/nSiO2 hydrogel has the potential to both control infection and to promote bone healing in contaminated defects.

Synergistic effect of exogeneous and endogeneous electrostimulation on osteogenic differentiation of human mesenchymal stem cells seeded on silk scaffolds

Bioelectrical regulation of bone fracture healing is important for many cellular events such as proliferation, migration, and differentiation. The aim of this study was to investigate the osteogenic differentiation potential of human mesenchymal stem cells (hMSCs) cultivated on silk scaffolds in response to different modes of electrostimulation (e.g., exogeneous and/or endogeneous). Endogeneous electrophysiology was altered through the use of monensin (10 nM) and glibenclamide (10 μM), along with external electrostimulation (60 kHz; 100-500 mV). Monensin enhanced the expression of early osteogenic markers such as alkaline phosphatase (ALP) and runt-related transcription factor 2 (RUNX-2). When exogeneous electrostimulation was combined with glibenclamide, more mature osteogenic marker upregulation based on bone sialoprotein expression (BSP) and mineralization was found. These results suggest the potential to exploit both exogeneous and endogeneous biophysical control of cell functions towards tissue-specific goals.

Retardation of fracture healing by cerclage wire near the elbow in radius fracture models

Cerclage wire is widely used in the treatment of fracture internal fixation and is shown effective in clinic. But a report by S.L. has pointed that the wire loop delayed the growth of bone. We have established a radius fracture model to study the possible detrimental effects of cerclage wire on fracture healing and the potential mechanism. By high-resolution CT analysis cerclage wire is found to delay fracture healing, by histological assessment cerclage wire is found to extended the time of hematoma and the marrow cavity appearing, by confocal microscopy cerclage wire decreased the content of calcium and the expression of alkaline phosphatase (ALP), and by RT-PCR analysis cerclage wire decreased the mRNA levels of bone sialoprotein and ALP. These results suggest that the cerclage wire near the elbow delayed the fracture healing in radius fracture models.

Towards functional 3D-stacked electrospun composite scaffolds of PHBV, silk fibroin and nanohydroxyapatite: Mechanical properties and surface osteogenic differentiation

Bone tissue engineering scaffolds have two challenging functional tasks to fulfil: to encourage cell proliferation, differentiation and matrix synthesis and to provide suitable mechanical stability upon implantation. Composites of biopolymers and bioceramics combine the advantages of both types of materials, resulting in better processability and enhanced mechanical and biological properties through matrix reinforcement. In the present study, novel thick bone composite scaffolds were successfully fabricated using electrospun flat sheets of polyhydroxybutyrate–polyhydroxyvalerate/nanohydroxyapatite/silk fibroin essence (2% nanohydroxyapatite – 2% silk fibroin essence and 5% nanohydroxyapatite – 5% silk fibroin essence, respectively). Their potential as in vitro bone regeneration scaffolds was evaluated using mouse calvarian osteoblast cells (MC3T3-E1), in terms of morphology (scanning electron microscope), cell attachment, cell proliferation, Col type I, osteopontin and bone alkaline phosphatase activity (Quantitative Real Time Polymerase Chain Reaction [qRT-PCR], enzyme-linked immunosorbent assay, immunocytochemistry). Electrospun polyhydroxybutyrate–polyhydroxyvalerate scaffolds were used as reference constructs. The results showed that the compressive and tensile mechanical properties of the scaffolds are dependent on the change in their composition, and the treatment these underwent. Furthermore, methanol-treated and autoclaved (MA) P2 (2% nanohydroxyapatite, 2% silk fibroin essence) samples appeared to exhibit more promising tensile properties. Additionally, the compressive tests results confirmed that the methanol pre-treatment and the autoclaving step lead to an increase in the P2 secant modulus when compared to the non-methanol-treated ones, P2 and P5 (5% nanohydroxyapatite, 5% silk fibroin essence), respectively.

Both formulations of polyhydroxybutyrate–polyhydroxyvalerate/nanohydroxyapatite/silk fibroin essence composite promoted greater cell adhesion and proliferation than the corresponding polyhydroxybutyrate–polyhydroxyvalerate control ones. Cells seeded on the composite fibrous scaffolds were extensively expanded and elongated on the fibre surface after one day in culture, whereas those seeded on the polyhydroxybutyrate–polyhydroxyvalerate scaffolds were not completely elongated. In addition, cells grown on P2 and P5 scaffolds had higher alkaline phosphatase activity when compared to those containing no nanohydroxyapatite/silk fibroin essence.

Injectable dual-gelling cell-laden composite hydrogels for bone tissue engineering

The present work investigated the osteogenic potential of injectable, dual thermally and chemically gelable composite hydrogels for mesenchymal stem cell (MSC) delivery in vitro and in vivo. Composite hydrogels comprising copolymer macromers of N-isopropylacrylamide were fabricated through the incorporation of gelatin microparticles (GMPs) as enzymatically digestible porogens and sites for cellular attachment. High and low polymer content hydrogels with and without GMP loading were shown to successfully encapsulate viable MSCs and maintain their survival over 28 days in vitro. GMP incorporation was also shown to modulate alkaline phosphatase production, but enhanced hydrogel mineralization along with higher polymer content even in the absence of cells. Moreover, the regenerative capacity of 2 mm thick hydrogels with GMPs only, MSCs only, or GMPs and MSCs was evaluated in vivo in an 8 mm rat critical size cranial defect for 4 and 12 weeks. GMP incorporation led to enhanced bony bridging and mineralization within the defect at each timepoint, and direct bone-implant contact as determined by microcomputed tomography and histological scoring, respectively. Encapsulation of both GMPs and MSCs enabled hydrogel degradation leading to significant tissue infiltration and osteoid formation. The results suggest that these injectable, dual-gelling cell-laden composite hydrogels can facilitate bone ingrowth and integration, warranting further investigation for bone tissue engineering.

Surface topography of hydroxyapatite promotes osteogenic differentiation of human bone marrow mesenchymal stem cells

Effective and safe induction of osteogenic differentiation is one of the key elements of bone tissue engineering. Surface topography of scaffold materials was recently found to promote osteogenic differentiation. Utilization of this topography may be a safer approach than traditional induction by growth factors or chemicals. The aim of this study is to investigate the enhancement of osteogenic differentiation by surface topography and its mechanism of action. Hydroxyapatite (HA) discs with average roughness (Ra) of surface topography ranging from 0.2 to 1.65 μm and mean distance between peaks (RSm) ranging from 89.7 to 18.6 μm were prepared, and human bone-marrow mesenchymal stem cells (hBMSCs) were cultured on these discs. Optimal osteogenic differentiation was observed on discs with surface topography characterized by Ra ranging from 0.77 to 1.09 μm and RSm ranging from 53.9 to 39.3 μm. On this surface configuration of HA, hBMSCs showed oriented attachment, F-actin arrangement, and a peak in the expression of Yes-associated protein (YAP) and PDZ binding motif (TAZ) (YAP/TAZ). These results indicated that the surface topography of HA promoted osteogenic differentiation of hBMSCs, possibly by increasing cell attachment and promoting the YAP/TAZ signaling pathway.

Differential osteogenic potential of human adipose-derived stem cells co-cultured with human osteoblasts on polymeric microfiber scaffolds

The osteogenic potential of human adipose-derived stem cells (HADSCs) co-cultured with human osteoblasts (HOBs) using selected HADSCs/HOBs ratios of 1:1, 2:1, and 1:2, respectively, is evaluated. The HADSCs/HOBs were seeded on electrospun three-dimensional poly[(R)-3-hydroxybutyric acid] (PHB) blended with bovine-derived hydroxyapatite (BHA). Monocultures of HADSCs and HOBs were used as control groups. The effects of PHB-BHA scaffold on cell proliferation and cell morphology were assessed by AlamarBlue assay and field emission scanning electron microscopy. Cell differentiation, cell mineralization, and osteogenic-related gene expression of co-culture HADSCs/HOBs were examined by alkaline phosphatase (ALP) assay, alizarin Red S assay, and quantitative real time PCR, respectively. The results showed that co-culture of HADSCs/HOBs, 1:1 grown into PHB-BHA promoted better cell adhesion, displayed a significant higher cell proliferation, higher production of ALP, extracellular mineralization and osteogenic-related gene expression of run-related transcription factor, bone sialoprotein, osteopontin, and osteocalcin compared to other co-culture groups. This result also suggests that the use of electrospun PHB-BHA in a co-culture HADSCs/HOBs system may serve as promising approach to facilitate osteogenic differentiation activity of HADSCs through direct cell-to-cell contact with HOBs.

Osteoblast response to zirconia surfaces with different topographies

Zirconia-3 mol% yttria ceramics were prepared with as-sintered, abraded, polished, and porous surfaces in order to explore the attachment, proliferation and differentiation of osteoblast-like cells. After modification, all surfaces were heated to 600°C to extinguish traces of organic contamination. All surfaces supported cell attachment, proliferation and differentiation but the surfaces with grain boundary grooves or abraded grooves provided conditions for enhanced initial cell attachment. Nevertheless, overall cell proliferation and total DNA were highest on the polished surface. Zirconia sintered at a lower temperature (1300°C vs. 1450°C) had open porosity and presented reduced proliferation as assessed by alamarBlue™ assay, possibly because the openness of the pores prevented cells developing a local microenvironment. All cells retained the typical polygonal morphology of osteoblast-like cells with variations attributable to the underlying surface notably alignment along the grooves of the abraded surface.

Simple coating with fibronectin fragment enhances stainless steel screw osseointegration in healthy and osteoporotic rats

Metal implants are widely used to provide structural support and stability in current surgical treatments for bone fractures, spinal fusions, and joint arthroplasties as well as craniofacial and dental applications. Early implant-bone mechanical fixation is an important requirement for the successful performance of such implants. However, adequate osseointegration has been difficult to achieve especially in challenging disease states like osteoporosis due to reduced bone mass and strength. Here, we present a simple coating strategy based on passive adsorption of FN7-10, a recombinant fragment of human fibronectin encompassing the major cell adhesive, integrin-binding site, onto 316-grade stainless steel (SS). FN7-10 coating on SS surfaces promoted α5β1 integrin-dependent adhesion and osteogenic differentiation of human mesenchymal stem cells. FN7-10-coated SS screws increased bone-implant mechanical fixation compared to uncoated screws by 30% and 45% at 1 and 3 months, respectively, in healthy rats. Importantly, FN7-10 coating significantly enhanced bone-screw fixation by 57% and 32% at 1 and 3 months, respectively, and bone-implant ingrowth by 30% at 3 months compared to uncoated screws in osteoporotic rats. These coatings are easy to apply intra-operatively, even to implants with complex geometries and structures, facilitating the potential for rapid translation to clinical settings.

Poly(ADP-ribose) in the bone: from oxidative stress signal to structural element

Contrary to common perception bone is a dynamic organ flexibly adapting to changes in mechanical loading by shifting the delicate balance between bone formation and bone resorption carried out by osteoblasts and osteoclasts, respectively. In the past decades numerous studies demonstrating production of reactive oxygen or nitrogen intermediates, effects of different antioxidants, and involvement of prototypical redox control mechanisms (Nrf2-Keap1, Steap4, FoxO, PAMM, caspase-2) have proven the central role of redox regulation in the bone. Poly(ADP-ribosyl)ation (PARylation), a NAD-dependent protein modification carried out by poly(ADP-ribose) polymerase (PARP) enzymes recently emerged as a new regulatory mechanism fine-tuning osteoblast differentiation and mineralization. Interestingly PARylation does not simply serve as a signaling mechanism during osteoblast differentiation but also couples it to osteoblast death. Even more strikingly, the poly(ADP-ribose) polymer likely released from succumbed cells at the terminal stage of differentiation is incorporated into the bone matrix representing the first structural role of this versatile biopolymer. Moreover, this new paradigm explains why and how osteodifferentiation and death of cells entering this pathway are closely coupled to each other. Here we review the role of reactive oxygen and nitrogen intermediates as well as PARylation in osteoblast and osteoclast differentiation, function, and cell death.