The osteogenic differentiation of human bone marrow MSCs on HUVEC-derived ECM and β-TCP scaffold

Looking into the Future: Toward Advanced 3D Biomaterials for Stem-Cell-Based Regenerative Medicine

Stem-cell-based therapies have the potential to provide novel solutions for the treatment of a variety of diseases, but the main obstacles to such therapies lie in the uncontrolled differentiation and functional engraftment of implanted tissues. The physicochemical microenvironment controls the self-renewal and differentiation of stem cells, and the key step in mimicking the stem cell microenvironment is to construct a more physiologically relevant 3D culture system. Material-based 3D assemblies of stem cells facilitate the cellular interactions that promote morphogenesis and tissue organization in a similar manner to that which occurs during embryogenesis. Both natural and artificial materials can be used to create 3D scaffolds, and synthetic organic and inorganic porous materials are the two main kinds of artificial materials. Nanotechnology provides new opportunities to design novel advanced materials with special physicochemical properties for 3D stem cell culture and transplantation. Herein, the advances and advantages of 3D scaffold materials, especially with respect to stem-cell-based therapies, are first outlined. Second, the stem cell biology in 3D scaffold materials is reviewed. Third, the progress and basic principles of developing 3D scaffold materials for clinical applications in tissue engineering and regenerative medicine are reviewed.

Functionalization of porous BCP scaffold by generating cell-derived extracellular matrix from rat bone marrow stem cells culture for bone tissue engineering

The potential of decellularized cell-derived extracellular matrix (ECM) deposited on biphasic calcium phosphate (BCP) scaffold for bone tissue engineering was investigated. Rat derived bone marrow mesenchymal stem cells were cultured on porous BCP scaffolds for 3 weeks and decellularized with two different methods (freeze-thaw [F/T] or sodium dodecyl sulfate [SDS]). The decellularized ECM deposited scaffolds (dECM-BCP) were characterized through scanning electron microscopy, energy dispersive X-ray spectrometer, and confocal microscopy. The efficiency of decellularization was evaluated by quantifying remaining DNA, sulfated glycosaminoglycans, and collagens. Results revealed that F/T method was more effective procedure for removing cellular components of cultured cells (95.21% DNA reduction) than SDS treatment (92.49%). Although significant loss of collagen was observed after decellularization with both F/T (56.68%) and SDS (70.87%) methods, F/T treated sample showed higher retaining amount of sulfated glycosaminoglycans content (75.64%) than SDS (33.28%). In addition, we investigated the cell biocompatibility and osteogenic effect of dECM-BCP scaffolds using preosteoblasts (MC3T3-E1). Compared to bare BCP scaffolds, dECM-BCP_F/T scaffolds showed improved cell attachment and proliferation based on immunofluorescence staining and water soluble tetrazolium salts assay (p < .001). Moreover, dECM-BCP scaffolds showed increased osteoblastic differentiation of newly seeded preosteoblasts by up-regulating three types of osteoblastic genes (osteopontin, alkaline phosphatase, and bone morphogenic protein-2). This study demonstrated that functionalization of BCP scaffold using cell-derived ECM could be useful for improving the bioactivity of materials and providing suitable microenvironment, especially for osteogenesis. Further study is needed to determine the potential of dECM-BCP scaffold for bone formation and regeneration in vivo.

Decellularized matrix of adipose-derived mesenchymal stromal cells enhanced retinal progenitor cell proliferation via the Akt/Erk pathway and neuronal differentiation

BACKGROUND AIMS

Retinal progenitor cells (RPCs) are a promising cell therapy treatment for retinal degenerative diseases. However, problems with limited proliferation ability and differentiation preference toward glia rather than neurons restrict the clinical application of these RPCs. The extracellular matrix (ECM) has been recognized to provide an appropriate microenvironment to support stem cell adhesion and direct cell behaviors, such as self-renewal and differentiation.

METHODS

In this study, decellularized matrix of adipose-derived mesenchymal stromal cells (DMA) was manufactured using a chemical agent method (0.5% ammonium hydroxide Triton + 20 mmol/L NH4OH) in combination with a biological agent method (DNase solution), and the resulting DMA were evaluated by scanning electron microscopy (SEM) and immunocytochemistry. The effect of DMA on RPC proliferation and differentiation was evaluated by quantitative polymerase chain reaction, Western blot and immunocytochemistry analysis.

RESULTS

DMA was successfully fabricated, as demonstrated by SEM and immunocytochemistry. Compared with tissue culture plates, DMA may effectively enhance the proliferation of RPCs by activating Akt and Erk phosphorylation; when the two pathways were blocked, the promoting effect was reversed. Moreover, DMA promoted the differentiation of RPCs toward retinal neurons, especially rhodopsin- and recoverin-positive photoreceptors, which is the most interesting class of cells for retinal degeneration treatment.

CONCLUSIONS

These results indicate that DMA has important roles in governing RPC proliferation and differentiation and may contribute to the application of RPCs in treating retinal degenerative diseases.

Light-Controlled BMSC Sheet-Implant Complexes with Improved Osteogenesis via an LRP5/β-Catenin/Runx2 Regulatory Loop

The combination of bone marrow mesenchymal stem cell (BMSC) sheets and titanium implants (BMSC sheet-implant complexes) can accelerate osseointegration. However, methods of fabricating BMSC sheet-implant complexes are quite limited, and the survival of BMSC sheet-implant complexes is one of the key barriers. Here, we show that a light-controlled fabricating system can generate less injured BMSC sheet-implant complexes with improved viability and osteogenesis and that noninvasive monitoring of the viability of BMSC sheet-implant complexes using a lentiviral delivery system is feasible. Enhanced green fluorescent protein- and luciferase-expressing BMSC sheets were used to track the viability of BMSC sheet-implant complexes in vivo. The experiments of micro-computed tomography analysis and hard tissue slices were performed to evaluate the osteogenic ability of BMSC sheet-implant complexes in vivo. The results showed that BMSC sheet-implant complexes survived for almost 1 month after implantation. Notably, BMSC sheet-implant complexes fabricated by the light-controlled fabricating system had upregulating expression levels of low-density lipoprotein-receptor-related protein 5 (LRP5), β-catenin, and runt-related transcription factor 2 (Runx2) compared to the complexes fabricated by mechanical scraping. Furthermore, we found that Runx2 directly bound to the rat LRP5 promoter and the LRP5/β-catenin/Runx2 regulatory loop contributed to the enhancement of the osseointegrating potentials. In this study, we successfully fabricated BMSC sheet-implant complexes with improved viability and osteogenesis and established a feasible, noninvasive, and continuous method for tracking BMSC sheet-implant complexes in vivo. Our findings lay the foundation for the application of BMSC sheet-implant complexes in vivo and open new avenues for engineered BMSC sheet-implant complexes.

Bone marrow stem cells-derived extracellular matrix is a promising material

The extracellular matrix(ECM), which is primarily composed of collagens and proteoglycans, plays a key role in cell proliferation, differentiation, and migration and interactions between cells. In this study, we produced chitosan/gelatin/bone marrow stem cells-derived extracellular matrix(C/G/BMSCs-dECM) scaffolds via lyophilization and cross-linking, and chitosan/gelatin(C/G) scaffolds were used as controls. For the C/G/BMSCs-dECM scaffolds, the average pore size was 289.17 ± 80.28 μm; the average porosity was 89.25 ± 3.75%; the average compressive modulus was 0.82 ± 0.07 MPa; and the average water uptake ratio was 13.81 ± 1.00. In vitro, the C/G/BMSCs-dECM scaffolds promoted bone marrow stem cells(BMSCs) attachment and proliferation. Moreover, improved osteogenic differentiation was observed for these scaffolds. Thus, C/G/BMSCs-dECM is a promising material for bone tissue engineering.

Comparison of the osteogenic capability of rat bone mesenchymal stem cells on collagen, collagen/hydroxyapatite, hydroxyapatite and biphasic calcium phosphate

Collagen (COL), collagen/hydroxyapatite (COL/HA), HA and biphasic calcium phosphate were prepared as representative bone grafting materials with composition analogous to bone, and their structural characteristics were analyzed. The rat bone mesenchymal stem cells (BMSCs) were further seeded onto four groups of materials, and BMSCs grown in basic medium and standard osteogenic medium were set as controls of a reference model to show the basic and osteogenic behavior of cells without the intervention of materials. Cellular behaviors were characterized, including proliferation, spreading morphology and expression of osteogenesis factors. The rat BMSCs proliferated properly with time on four groups of materials as well on two groups of controls, and typical cuboidal, polygonal and extremely-elongated morphologies of cells were observed. According to the real-time polymerase chain reaction data, a higher osteogenic gene expression level was dependent upon the growing morphology but not the proliferation rate of cells, and the osteogenic differentiation capacity of cells onto four groups of materials varied in specific genes. In general, BMSCs exhibited the highest osteogenic capacity onto COL/HA, but the poorest onto HA. The growing behaviors of cells on materials were further discussed in comparison with the cases of OC and BC of the reference model. The present attempt to comparatively analyze cell experimental data with a reference model is expected to be useful for revealing the difference in the osteogenic capability of MSCs onto materials or even the bioactivity of materials.

Decellularized extracellular matrix of human umbilical vein endothelial cells promotes endothelial differentiation of stem cells from exfoliated deciduous teeth

Dental stem cells can serve as a potential source of functional endothelial cells for tissue engineering applications, but the endothelial-lineage differentiation efficiency is rather low even with growth factors and mechanical stimuli, which greatly limits their clinical applications. This is partly due to the deficiency of standard two-dimensional (2-D) culture systems, which is unable to recapitulate the three-dimensional (3-D) in vivo milieu that is rich in extracellular matrix. Hence, we extracted decellularized extracellular matrix from human umbilical vein endothelial cells (HUVECs-DECM) to provide a bioactive substratum conducive to the endothelial differentiation of dental stem cells. Compared to cells plated on tissue culture polystyrene (TCP), stem cells from exfoliated deciduous teeth (SHED) cultured on the HUVECs-DECM demonstrated more regular arrangement and elongated morphology. HUVECs-DECM significantly enhanced the rapid adhesion and proliferation rates of SHED, as demonstrated by WST-8 assay and immunocytochemistry indicating higher expression levels of vinculin by newly adherent SHED on HUVECs-DECM versus TCP. In addition, there was twofold to fivefold higher mRNA expression levels of endothelial-specific markers CD31 and VEGFR-2 in SHED after seven days of culture on DECM versus TCP. Functional testing with in vitro matrigel angiogenesis assay identified more capillary-like structure formation with significantly higher tubule length in SHED induced by DECM versus TCP. Hence, the results of this study provide a better understanding of the unique characteristics of cell-specific ECM and demonstrated the potential use of HUVECs-DECM as a culture substratum conducive for stimulating the endothelial differentiation of SHED for therapeutic angiogenic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1083-1093, 2017.

Hypoxia-Mimicking Nanofibrous Scaffolds Promote Endogenous Bone Regeneration

Utilizing biomimetic materials to potentiate endogenous cell growth or signaling is superior to relying on exogenous cells or signals for bone formation. Desferoxamine (DFO), which is a hypoxia-mimetic agent that chelates iron (Fe³⁺), mimics hypoxia to encourage bone healing. However, high cytotoxicity, off-target effects, and the short half-life of DFO have significantly impeded its further applications. We mitigated these side effects by locally immobilizing DFO onto a gelatin nanofibrous (GF) scaffold that retained DFO's ability to chelate Fe³⁺. Moreover, DFO-functionalized GF (GF-DFO) scaffolds, which have similar micro/macrostructures to GF scaffolds, not only demonstrated decreased cytotoxicity on both human umbilical vein endothelial cells and human mesenchymal stem cells but also significantly increased vascular endothelial growth factor (VEGF) expression in vitro. Most importantly, in our in vivo experiments on a critical-sized cranial bone defect mouse model, a significant amount of bone was formed in most of the GF-DFO scaffolds after six weeks, while very little new bone was observed in the GF scaffolds. These data suggest that use of a hypoxia-mimicking nanofibrous scaffold is a promising strategy for promoting endogenous bone formation.

Enhancement of neurite adhesion, alignment and elongation on conductive polypyrrole-poly(lactide acid) fibers with cell-derived extracellular matrix

Extracellular matrix (ECM) can promote peripheral nerve repair. In this study, a conductive fiber-film (CFF) with core-sheath structure and conductivity of ∼10Scm^-1 was prepared by electrospinning of aligned poly(l-lactide acid) (PLLA) fibers and electrochemical deposition of polypyrole (PPy) nanoparticles. Then the multiple components of ECM, including laminin, fibronectin and collagen, were coated on the surface of CFF by culturing and lysing L929 cells to fabricate the bioactive scaffold of ECM-linked CFF (ECM-CFF). The electrical stimulation (ES) of 100mV/cm for 14days and 2h per day did not significantly decrease the conductivity of ECM-CFF. The results of PC12 cells test indicated that, cells adhesion rate, neurite-bearing cell rate and neurite alignment rate on ECM-CFF were ∼95%, ∼77%, ∼70%, respectively, significantly larger than the corresponding values on bare CFF (17%, 29% and 14%, respectively). The neurites length on ECM-CFF (∼79mm) was also larger than that on bare CFF (∼25mm). ES of 100mV/cm onto PC12 cells through ECM-CFF could significantly promote neurite extension in first 3days of the neurite growth. These results indicated that, the combination of ECM-CFF with ES could improve the nerve regeneration by encouraging neural-cell adhesion, neurite growth and extension.

Fabrication and characterization of polycaprolactone and tricalcium phosphate composites for tissue engineering applications

Background/purpose

β-Tricalcium phosphate (β-TCP) is an osteoconductive material which has been used for clinical purposes for several years, as is polycaprolactone (PCL), which has already been approved for a number of medical and drug delivery devices. In this study we have incorporated various concentrations of β-TCP into PCL with the aim of developing an injectable, mechanically strong, and biodegradable material which can be used for medical purposes without organic solvents.

Materials and methods

This study assesses the physical and chemical properties of this material, evaluates the in vitro bioactivity of the PCL/β-TCP composites, and analyzes cell proliferation and osteogenic differentiation when using human bone marrow mesenchymal stem cells (hBMSCs).

Results

The results show that weight losses of approximately 5.3%, 12.1%, 18.6%, and 25.2%, were observed for the TCP0, TCP10, TCP30, and TCP50 composites after immersion in simulated body fluid for 12 weeks, respectively, indicating significant differences (P < 0.05). In addition, PCL/β-TCP composites tend to have lower contact angles (47 ± 1.5° and 58 ± 1.7° for TCP50 and TCP30, respectively) than pure PCL (85 ± 1.3°), which are generally more hydrophilic. After 7 days, a significant (22% and 34%, respectively) increase (P < 0.05) in alkaline phosphatase level was measured for TCP30 and TCP50 in comparison with the pure PCL.

Conclusion

PCL/TCP is biocompatible with hBMSCs. It not only promotes proliferation of hBMSCs but also helps to differentiate reparative hard tissue. We suggest 50% (weight) PCL-containing β-TCP biocomposites as the best choice for hard tissue repair applications.

The effect of local delivery of adiponectin from biodegradable microsphere-scaffold composites on new bone formation in adiponectin knockout mice

Adiponectin (APN) is the most abundant adipocyte-secreted adipokine; it regulates energy homeostasis and exerts well-characterized insulin-sensitizing properties. Previous studies have verified that globular adiponectin (gAPN) is also involved in bone metabolism, although observations have been controversial. The purpose of the current study is to use an APN-knockout (APN-KO) mouse model to evaluate the local delivery of gAPN to new bone formation. Using chitosan microspheres (CMs), we found that following an initial burst at 1 week, the release behavior of gAPN from the scaffold was sustained in a linear manner for the first 4 weeks, followed by a slower, more stable release from week 5 onwards. Interestingly, PLGA/β-TCP/CM-loaded gAPN scaffolds implanted in APN-KO mice increased bone formation and mineralization, and enhanced osteogenic marker expression 28 days post-implantation. gAPN also promoted preosteoblast (MC3T3-E1) cellular proliferation in vitro. In MC3T3-E1 cells, adaptor protein-containing pleckstrin homology domain, phosphotyrosine domain, leucine zipper motif (APPL1) and phosphoinositide 3-kinase (PI3K) expression was upregulated in a time-dependent manner upon gAPN treatment, while APPL1 small interfering RNA (siRNA) pre-treatment reversed this enhanced expression. In conclusion, modified bone graft substitutes loaded with gAPN increase bone formation and mineralization in part by promoting osteoblast proliferation via the APPL1/PI3K pathway.

Perichondrium mesenchymal stem cells inhibit the growth of breast cancer cells via the DKK-1/Wnt/β-catenin signaling pathway

In recent years, mesenchymal stem cells (MSCs), which possess the ability to specifically home to tumor sites, with the potential of multi-directional differentiation and low immunogenicity, have been reported to inhibit the growth of various types of tumors. In the present study, we isolated MSCs from the rib perichondrium (PMSCs). By comparing PMSCs with bone marrow‑derived mesenchymal stem cells (BMSCs), we demonstrated that PMSCs present biological characteristics similar to those of BMSCs. Furthermore, we explored the effect and antitumor mechanism of PMSCs in rat SHZ-88 breast cancer cells. The growth, migration and invasion of the SHZ-88 cells were significantly inhibited, and the Wnt/β-catenin pathway and its target genes were downregulated in the SHZ-88 cells by PMSC-conditioned medium. The expression level of dickkopf-1 (DKK-1) was higher in the PMSCs than that noted in the SHZ-88 cells. Neutralization of DKK-1 in the PMSC‑conditioned medium attenuated the inhibitory effects of PMSCs on SHZ-88 cells. Therefore, PMSC-secreted DKK-1 is involved in the inhibition of SHZ-88 cell growth, migration and invasion, via the Wnt/β‑catenin signaling pathway. In addition, we demonstrated that PMSCs inhibited the growth of breast cancer in vivo and prolonged the survival time of tumor‑bearing rats. PMSCs inhibited the growth of transplanted breast tumors through the Wnt/β-catenin signaling pathway. In conclusion, our data confirmed that MSCs derived from the perichondrium present biological characteristics similar to those of BMSCs and inhibit the growth of breast cancer cells through the Wnt/β-catenin signaling pathway in vitro and in vivo. DKK-1 secreted by PMSCs played a vital role in controlling the Wnt/β-catenin signaling pathway in breast cancer.

Bioprinting Organotypic Hydrogels with Improved Mesenchymal Stem Cell Remodeling and Mineralization Properties for Bone Tissue Engineering

3D-manufactured hydrogels with precise contours and biological adhesion motifs are interesting candidates in the regenerative medicine field for the culture and differentiation of human bone-marrow-derived mesenchymal stem cells (MSCs). 3D-bioprinting is a powerful technique to approach one step closer the native organization of cells. This study investigates the effect of the incorporation of collagen type I in 3D-bioprinted polysaccharide-based hydrogels to the modulation of cell morphology, osteogenic remodeling potential, and mineralization. By combining thermo-responsive agarose hydrogels with collagen type I, the mechanical stiffness and printing contours of printed constructs can be improved compared to pure collagen hydrogels which are typically used as standard materials for MSC osteogenic differentiation. The results presented here show that MSC not only survive the 3D-bioprinting process but also maintain the mesenchymal phenotype, as proved by live/dead staining and immunocytochemistry (vimentin positive, CD34 negative). Increased solids concentrations of collagen in the hydrogel blend induce changes in cell morphology, namely, by enhancing cell spreading, that ultimately contribute to enhanced and directed MSC osteogenic differentiation. 3D-bioprinted agarose-collagen hydrogels with high-collagen ratio are therefore feasible for MSC osteogenic differentiation, contrarily to low-collagen blends, as proved by two-photon microscopy, Alizarin Red staining, and real-time polymerase chain reaction.

Variation of mechanical behavior of β-TCP/collagen two phase composite scaffold with mesenchymal stem cell in vitro

The primary aim of this study is to characterize the variational behavior of the compressive mechanical property of bioceramic-based scaffolds using stem cells during the cell culture period. β-Tricalcium phosphate (TCP)/collagen two phase composites and β-TCP scaffolds were fabricated using the polyurethane template technique and a subsequent freeze-drying method. Rat bone-marrow mesenchymal stem cells (rMSCs) were then cultured in these scaffolds for up to 28 days. Compression tests of the scaffolds with rMSCs were periodically conducted. Biological properties, such as the cell number, alkaline phosphatase (ALP) activity, and gene expressions of osteogenesis, were evaluated. The microstructural change due to cell growth and the formation of extracellular matrices was examined using a field-emission scanning electron microscope. The compressive property was then correlated with the biological properties and microstructures to understand the mechanism of the variational behavior of the macroscopic mechanical property. The porous collagen structure in the β-TCP scaffold effectively improved the structural stability of the composite scaffold, whereas the β-TCP scaffold exhibited structural instability with the collapse of the porous structure when immersed in a culture medium. The β-TCP/collagen composite scaffold exhibited higher ALP activity and more active generation of osteoblastic markers than the β-TCP scaffold.

Polymer mesh scaffold combined with cell-derived ECM for osteogenesis of human mesenchymal stem cells

Background

Tissue-engineered scaffold should mimic the structure and biological function of the extracellular matrix and have mechanically supportive properties for tissue regeneration. In this study, we utilized a PLGA/PLA mesh scaffold, coated with cell-derived extracellular matrix (CDM) and assessed its potential as an osteogenic microenvironment for human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs). CDM was obtained by decellularization of in vitro-cultured type I collagen overexpressing (Col I -293 T-DK) cells. Test groups are mesh itself (control), fibronectin-coated (FN-mesh), and CDM-coated mesh scaffold (CDM-mesh). CDM was then solubilized and used for scaffold coating.

Results

CDM was successfully collected and applied to mesh scaffolds. The presence of CDM was confirmed via SEM and FN immunofluorescence. After then, UCB-MSCs were seeded into the scaffolds and subjected to the induction of osteogenic differentiation for 21 days in vitro. We found that the seeded cells were viable and have better proliferation activity on CDM-mesh scaffold. In addition, when osteogenic differentiation of UCB-MSCs was examined for up to 21 days, alkaline phosphatase (ALP) activity and osteogenic marker (COL I, ALP, osteocalcin, bone sialoprotein) expression were significantly improved with UCB-MSCs when cultured in the CDM-mesh scaffold compared to the control and FN-mesh.

Conclusion

Polymer mesh scaffold incorporated with CDM can provide UCB-MSCs with a better microenvironment for osteogenesis in vitro.

Transcriptomic Changes in Osteoblasts Following Endothelial Cell-Cocultivation Suggest a Role of Extracellular Matrix in Cellular Interaction

Vascularization is important for bone development, fracture healing and engineering of artificial bone tissue. In the context of bone tissue engineering, it was shown that coimplantation of human primary umbilical vein endothelial cells (HUVECs) and human osteoblasts (hOBs) results in the formation of functional blood vessels and enhanced bone regeneration. Implanted endothelial cells do not only contribute to blood vessel formation, but also support proliferation, cell survival and osteogenic differentiation of coimplanted hOBs. These effects are partially mediated by direct heterotypic cell contacts. In a previous report we could show that cocultivated hOBs strongly increase the expression of genes involved in extracellular matrix (ECM) formation in HUVECs, suggesting that ECM may be involved in the intercellular communication between hOBs and HUVECs. The present study aimed at investigating whether comparable changes occur in hOBs. We therefore performed a microarray analysis of hOBs cultivated in direct contact with HUVECs, revealing 1,004 differentially expressed genes. The differentially expressed genes could be assigned to the functional clusters ECM, proliferation, apoptosis and osteogenic differentiation. The microarray data could be confirmed by performing quantitative real time RT-PCR on selected genes. Furthermore, we could show that the ECM produced by HUVECs increased the expression of the osteogenic differentiation marker alkaline phosphatase (ALP) in hOBs. In summary, our data demonstrate that HUVECs provoke complex changes in gene expression patterns in cocultivated hOBs and that ECM plays and important role in this interaction. J. Cell. Biochem. 117: 1869-1879, 2016. © 2016 Wiley Periodicals, Inc.

Preparation and characterization of calcium phosphate/pectin scaffolds for bone tissue engineering

A calcium phosphate cement (CPC) scaffold has been used to repair bone defects, but its low compressive strength and poor osteogenesis greatly hinder its clinical application.

Osteogenic Differentiation Evaluation of an Engineered Extracellular Matrix Based Tissue Sheet for Potential Periosteum Replacement

Due to the indispensable role of periosteum in bone defect healing and regeneration, a promising method to enhance osteogenesis of bone grafts by using an engineered biomimetic periosteum would be highly beneficial. The stromal microenvironment of periosteum is composed of various highly organized extracellular matrix (ECM) fibers, so an aligned natural ECM sheet, derived from the human dermal fibroblast cell sheet, may be advantageous when applied for artificial periosteum fabrication. Human mesenchymal stem cells (hMSCs) have been used to replace the osteoprogenitor cell population in native periosteum due to hMSCs' great osteogenic potential and fast in vitro expansion capacity. The objective of this work is to investigate if the natural ECM sheet and the substrate alignment can promote in vitro osteogenesis of hMSCs. The conventional cell culture substrates collagen I-coated polydimethylsiloxane (PDMS) and tissue culture plastic (TCP) were used as controls. It was found that the ECM sheet significantly increased alkaline phosphatase activity and calcium deposition. The enhanced osteogenic potential was further confirmed by increased bone-specific gene expression. The ECM sheet can bind significantly higher amounts of growth factors including ANG-1, TGF-β1, bFGF, and VEGF, as well as calcium phosphate nanoparticles, which contributed to high osteogenesis of the hMSCs on ECM sheet. However, the alignment of the substrates did not show significant influence on osteogenic activity and growth factor binding. These results demonstrated the great potential of hMSC-seeded ECM sheet as a biomimetic periosteum to improve critical sized bone regeneration.

Collagen/Beta-Tricalcium Phosphate Based Synthetic Bone Grafts via Dehydrothermal Processing

Millions of patients worldwide remain inadequately treated for bone defects related to factors such as disease or trauma. The drawbacks of metallic implant and autograft/allograft use have steered therapeutic approaches towards tissue engineering solutions involving tissue regeneration scaffolds. This study proposes a composite scaffold with properties tailored to address the macro- and microenvironmental conditions deemed necessary for successful regeneration of bone in defect areas. The biodegradable scaffold composed of porous beta-tricalcium phosphate particles and collagen type I fibers is prepared from a mixture of collagen type-I and β-tricalcium phosphate (β-TCP) particles via lyophilization, followed by dehydrothermal (DHT) processing. The effects of both sterilization via gamma radiation and the use of DHT processing to achieve cross-linking were investigated. The impact of the chosen fabrication methods on scaffold microstructure and β-TCP particle-collagen fiber combinations were analyzed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and microcomputerized tomography (µ-CT). Electron spinning resonance (ESR) analysis was used to investigate free radicals formation following sterilization. Results revealed that the highly porous (65% porosity at an average of 100 µm pore size), mechanically adequate, and biocompatible scaffolds can be utilized for bone defect repairs.

Human Dental Pulp Cells Responses to Apatite Precipitation from Dicalcium Silicates

Unraveling the mechanisms behind the processes of cell attachment and the enhanced proliferation that occurs as a response to the presence of calcium silicate-based materials needs to be better understood so as to expand the applications of silicate-based materials. Ions in the environment may influence apatite precipitation and affect silicate ion release from silicate-based materials. Thus, the involvement of apatite precipitate in the regulation of cell behavior of human dental pulp cells (hDPCs) is also investigated in the present study, along with an investigation of the specific role of cell morphology and osteocalcin protein expression cultured on calcium silicate (CS) with different Dulbecco's modified Eagle's medium (DMEM). The microstructure and component of CS cement immersion in DMEM and P-free DMEM are analyzed. In addition, when hDPCs are cultured on CS with two DMEMs, we evaluate fibronectin (FN) and collagen type I (COL) secretion during the cell attachment stage. The facilitation of cell adhesion on CS has been confirmed and observed both by scanning with an electron microscope and using immunofluorescence imaging. The results indicate that CS is completely covered by an apatite layer with tiny spherical shapes on the surface in the DMEM, but not in the P-free DMEM. Compared to the P-free DMEM, the lower Ca ion in the DMEM may be attributed to the formation of the apatite on the surfaces of specimens as a result of consumption of the Ca ion from the DMEM. Similarly, the lower Si ion in the CS-soaked DMEM is attributed to the shielding effect of the apatite layer. The P-free DMEM group releases more Si ion increased COL and FN secretion, which promotes cell attachment more effectively than DMEM. This study provides new and important clues regarding the major effects of Si-induced cell behavior as well as the precipitated apatite-inhibited hDPC behavior on these materials.

Characterization of bone marrow mononuclear cells on biomaterials for bone tissue engineering in vitro

Bone marrow mononuclear cells (BMCs) are suitable for bone tissue engineering. Comparative data regarding the needs of BMC for the adhesion on biomaterials and biocompatibility to various biomaterials are lacking to a large extent. Therefore, we evaluated whether a surface coating would enhance BMC adhesion and analyze the biocompatibility of three different kinds of biomaterials. BMCs were purified from human bone marrow aspirate samples. Beta tricalcium phosphate (β-TCP, without coating or coated with fibronectin or human plasma), demineralized bone matrix (DBM), and bovine cancellous bone (BS) were assessed. Seeding efficacy on β-TCP was 95% regardless of the surface coating. BMC demonstrated a significantly increased initial adhesion on DBM and β-TCP compared to BS. On day 14, metabolic activity was significantly increased in BMC seeded on DBM in comparison to BMC seeded on BS. Likewise increased VEGF-synthesis was observed on day 2 in BMC seeded on DBM when compared to BMC seeded on BS. The seeding efficacy of BMC on uncoated biomaterials is generally high although there are differences between these biomaterials. Beta-TCP and DBM were similar and both superior to BS, suggesting either as suitable materials for spatial restriction of BMC used for regenerative medicine purposes in vivo.

Enzyme-assisted calcium phosphate biomineralization on an inert alumina surface

In this study a bioinspired approach to induce self-mineralization of bone-like material on alumina surfaces is presented. The mineralizing enzyme alkaline phosphatase (ALP) is covalently immobilized by a carbodiimide-mediated chemoligation method. The enzymatic activity of immobilized ALP and its mineralization capability are investigated under acellular conditions as well as in the presence of human bone cells. Analytical, biochemical and immunohistochemical characterization show that ALP is efficiently immobilized, retains its activity and can trigger calcium phosphate mineralization on alumina at acellular conditions. In vitro cell tests demonstrate that ALP-functionalized alumina clearly boosts and enhances bone cell mineralization. Our results underpin the great potential of ALP-functionalized alumina for the development of bioactive surfaces for applications such as orthopaedic and dental implants, enabling a fast and firm implant osseointegration.

Effects of calcium phosphate nanocrystals on osseointegration of titanium implant in irradiated bone

Radiotherapy may compromise the integration of implant and cause implant loss. Implant surface modifications have the possibility of promoting cell attachment, cell growth, and bone formation which ultimately enhance the osseointegration process. The present study aimed to investigate the effects of calcium phosphate nanocrystals on implant osseointegration in irradiated bone. Sixteen rabbits were randomly assigned into control and nano-CaP groups, receiving implants with dual acid-etched surface or dual acid-etched surface discretely deposited of nanoscale calcium-phosphate crystals, respectively. The left leg of all the rabbits received 15 Gy radiation, followed by implants placement one week after. Four animals in each group were sacrificed after 4 and 12 weeks, respectively. Implant stability quotient (ISQ), ratio of bone volume to total volume (BV/TV), bone growth rate, and bone-to-implant contact (BIC) were evaluated. The nano-CaP group showed significantly higher ISQ (week 12, P = 0.031) and bone growth rate (week 6, P = 0.021; week 9, P = 0.001) than that in control group. No significant differences in BV/TV and BIC were found between two groups. Titanium implant surface modified with CaP nanocrystals provides a potential alternative to improve bone healing around implant in irradiated bone.

Ornamenting 3D printed scaffolds with cell-laid extracellular matrix for bone tissue regeneration

3D printing technique is the most sophisticated technique to produce scaffolds with tailorable physical properties. But, these scaffolds often suffer from limited biological functionality as they are typically made from synthetic materials. Cell-laid mineralized ECM was shown to be potential for improving the cellular responses and drive osteogenesis of stem cells. Here, we intend to improve the biological functionality of 3D-printed synthetic scaffolds by ornamenting them with cell-laid mineralized extracellular matrix (ECM) that mimics a bony microenvironment. We developed bone graft substitutes by using 3D printed scaffolds made from a composite of polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) and mineralized ECM laid by human nasal inferior turbinate tissue-derived mesenchymal stromal cells (hTMSCs). A rotary flask bioreactor was used to culture hTMSCs on the scaffolds to foster formation of mineralized ECM. A freeze/thaw cycle in hypotonic buffer was used to efficiently decellularize (97% DNA reduction) the ECM-ornamented scaffolds while preserving its main organic and inorganic components. The ECM-ornamented 3D printed scaffolds supported osteoblastic differentiation of newly-seeded hTMSCs by upregulating four typical osteoblastic genes (4-fold higher RUNX2; 3-fold higher ALP; 4-fold higher osteocalcin; and 4-fold higher osteopontin) and increasing calcium deposition compared to bare 3D printed scaffolds. In vivo, in ectopic and orthotopic models in rats, ECM-ornamented scaffolds induced greater bone formation than that of bare scaffolds. These results suggest a valuable method to produce ECM-ornamented 3D printed scaffolds as off-the-shelf bone graft substitutes that combine tunable physical properties with physiological presentation of biological signals.

Effects of proliferation and differentiation of mesenchymal stem cells on compressive mechanical behavior of collagen/β-TCP composite scaffold

The primary aim of this study is to characterize the effects of cell culture on the compressive mechanical behavior of the collagen/β-tricalcium phosphate (TCP) composite scaffold. The composite and pure collagen scaffolds were fabricated by the solid-liquid phase separation technique and the subsequent freeze-drying method. Rat bone marrow mesenchymal stem cells (rMSCs) were then cultured in these scaffolds up to 28 days. Compression test of the scaffolds with rMSCs were conducted periodically. Biological properties such as cell number, alkaline phosphatase (ALP) activity, and gene expressions of osteogenetic bone markers were evaluated during cell culture. The microstructural changes in the scaffolds during cell culture were also examined using a scanning electron microscope. The compressive elastic modulus was then correlated with those of the biological properties and microstructures to understand the mechanism of variational behavior of the macroscopic elastic property. The composite scaffold exhibited higher ALP activity and more active generation of osteoblastic markers than the collagen scaffold, indicating that β-TCP can activate the differentiation of rMSCs into osteoblasts and extracellular matrix (ECM) formation such as type I collagen and the following mineralization. The variational behavior of the compressive modulus of the composite scaffold was affected by both the material degradation and the proliferation of cells and the ECM formation. In the first stage, the modulus of the composite scaffold tended to increase due to cell proliferation and the following formation of network structure. In the second stage, the modulus tended to decrease because the material degradation such as ductile deformation of collagen and decomposition of β-TCP were more effective on the property than the ECM formation. In the third stage, active calcification by formation and growth of mineralized nodules resulted in the recovery of modulus. It is concluded that the introduction of β-TCP powder into the porous collagen matrix is very effective to improve the mechanical and biological properties of collagen scaffold prepared for bone tissue engineering. Furthermore, the compressive modulus of the composite scaffold is strongly affected by the material degradation and the ECM formation by stem cells under in vitro culture condition.

Biological assessment of a calcium silicate incorporated hydroxyapatite-gelatin nanocomposite: a comparison to decellularized bone matrix

Our laboratory utilized biomimicry to develop a synthetic bone scaffold based on hydroxyapatite-gelatin-calcium silicate (HGCS). Here, we evaluated the potential of HGCS scaffold in bone formation in vivo using the rat calvarial critical-sized defect (CSD). Twelve Sprague-Dawley rats were randomized to four groups: control (defect only), decellularized bone matrix (DECBM), and HGCS with and without multipotent adult progenitor cells (MAPCs). DECBM was prepared by removing all the cells using SDS and NH₄OH. After 12 weeks, the CSD specimens were harvested to evaluate radiographical, histological, and histomorphometrical outcomes. The in vitro osteogenic effects of the materials were studied by focal adhesion, MTS, and alizarin red. Micro-CT analysis indicated that the DECBM and the HGCS scaffold groups developed greater radiopaque areas than the other groups. Bone regeneration, assessed using histological analysis and fluorochrome labeling, was the highest in the HGCS scaffold seeded with MAPCs. The DECBM group showed limited osteoinductivity, causing a gap between the implant and host tissue. The group grafted with HGCS+MAPCs resulting in twice as much new bone formation seems to indicate a role for effective bone regeneration. In conclusion, the novel HGCS scaffold could improve bone regeneration and is a promising carrier for stem cell-mediated bone regeneration.

Engineering vascularized bone grafts by integrating a biomimetic periosteum and β-TCP scaffold

Treatment of large bone defects using synthetic scaffolds remain a challenge mainly due to insufficient vascularization. This study is to engineer a vascularized bone graft by integrating a vascularized biomimetic cell-sheet-engineered periosteum (CSEP) and a biodegradable macroporous beta-tricalcium phosphate (β-TCP) scaffold. We first cultured human mesenchymal stem cells (hMSCs) to form cell sheet and human umbilical vascular endothelial cells (HUVECs) were then seeded on the undifferentiated hMSCs sheet to form vascularized cell sheet for mimicking the fibrous layer of native periosteum. A mineralized hMSCs sheet was cultured to mimic the cambium layer of native periosteum. This mineralized hMSCs sheet was first wrapped onto a cylindrical β-TCP scaffold followed by wrapping the vascularized HUVEC/hMSC sheet, thus generating a biomimetic CSEP on the β-TCP scaffold. A nonperiosteum structural cell sheets-covered β-TCP and plain β-TCP were used as controls. In vitro studies indicate that the undifferentiated hMSCs sheet facilitated HUVECs to form rich capillary-like networks. In vivo studies indicate that the biomimetic CSEP enhanced angiogenesis and functional anastomosis between the in vitro preformed human capillary networks and the mouse host vasculature. MicroCT analysis and osteocalcin staining show that the biomimetic CSEP/β-TCP graft formed more bone matrix compared to the other groups. These results suggest that the CSEP that mimics the cellular components and spatial configuration of periosteum plays a critical role in vascularization and osteogenesis. Our studies suggest that a biomimetic periosteum-covered β-TCP graft is a promising approach for bone regeneration.

Fabrication of PLLA/β-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering

Polymer and ceramic composite scaffolds play a crucial role in bone tissue engineering. In an attempt to mimic the architecture of natural extracellular matrix (ECM), poly(l-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) nanocomposite scaffolds with a hierarchical pore structure were fabricated by combining thermal induced phase separation and salt leaching techniques. The nanocomposite scaffold consisted of a nanofibrous PLLA matrix with a highly interconnected, high porosity (>93%) hierarchical pore structure with pore diameters ranging from 500nm to 300μm and a homogeneously distributed β-TCP nanoparticle phase. The nanofibrous PLLA matrix had a fiber diameter of 70-300nm. The nanocomposite scaffolds possess three levels of hierarchical structure: (1) porosity; (2) nanofibrous PLLA struts comprising the pore walls; and (3) β-TCP nanoparticle phase. The β-TCP nanoparticle phase improved the mechanical properties and bioactivity of the PLLA matrix. The nanocomposite scaffolds supported MG-63 osteoblast proliferation, penetration, and ECM deposition, indicating the potential of PLLA/β-TCP nanocomposite scaffolds with hierarchical porosity for bone tissue engineering applications.

Decellularization and Recellularization Technologies in Tissue Engineering

Decellularization is the process by which cells are discharged from tissues/organs, but all of the essential cues for cell preservation and homeostasis are retained in a three-dimensional structure of the organ and its extracellular matrix components. During tissue decellularization, maintenance of the native ultrastructure and composition of the extracellular matrix (ECM) is extremely acceptable. For recellularization, the scaffold/matrix is seeded with cells, the final goal being to form a practical organ. In this review, we focus on the biological properties of the ECM that remains when a variety of decellularization methods are used, comparing recellularization technologies, including bioreactor expansion for perfusion-based bioartificial organs, and we discuss cell sources. In the future, decellularization–recellularization procedures may solve the problem of organ assembly on demand.

Mineral trioxide aggregate upregulates odonto/osteogenic capacity of bone marrow stromal cells from craniofacial bones via JNK and ERK MAPK signalling pathways

OBJECTIVES

The aim of this study was to investigate effects of mineral trioxide aggregate (MTA) on odonto/osteogenic differentiation of bone marrow stromal cells (BMSCs) from craniofacial bones.

MATERIALS AND METHODS

Craniofacial BMSCs were isolated from rat mandible and effects of MTA on their proliferation, differentiation and MAPK pathway involvement were subsequently investigated, in vitro. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2,5-tetrazoliumbromide) assay was performed to evaluate proliferation of the MTA-treated cells. Alkaline phosphatase (ALP) activity, alizarin red staining, real-time reverse transcription polymerase chain reaction and western blot assays were used to assess differentiation capacity as well as MAPK pathway involvement.

RESULTS

0.02 mg/ml MTA-treated BMSCs had significantly higher ALP activity and formed more mineralized nodules than the untreated group. Odonto/osteoblastic marker genes/proteins (Alp, Runx2/RUNX2, Osx/OSX, Ocn/OCN and Dspp/DSP respectively) in MTA-treated cells were remarkably upregulated compared to untreated ones. Mechanistically, phosphorylated Jun N-terminal kinase (P-JNK) and phosphorylated extracellular regulated protein kinases (P-ERK) in MTA-treated BMSCs increased significantly in a time-dependent manner, while inhibition of JNK and ERK MAPK pathways dramatically blocked MTA-induced odonto/osteoblastic differentiation, as indicated by reduced ALP levels, weakened mineralization capacity and downregulated levels of odonto/osteoblastic marker genes (Alp, Runx2, Osx, Ocn and Dspp).

CONCLUSION

Mineral trioxide aggregate promoted odonto/osteogenic capacity of craniofacial BMSCs via JNK and ERK MAPK signalling pathways.

Potential application of hydrolyzed fish collagen for inducing the multidirectional differentiation of rat bone marrow mesenchymal stem cells

Hydrolyzed fish collagen (HFC) has recently attracted considerable attention because of its outstanding bioactivity. However, few studies have been performed to determine the biological effects of HFC on bone marrow mesenchymal stem cells (BMSCs), which are often used in regenerative medicine. In this study, the molecular weight, amino acid composition, and contact angle of HFC were measured. The influence of HFC on cell viability and the multidirectional differentiation of BMSCs into osteogenic, endothelial, adipogenic, chondrogenic, and neural lineages were also assessed. Furthermore, the mechanism by which HFC promotes osteogenesis was investigated at the protein level. The molecular weight of HFC ranged from 700 to 1300 Da, the contact angle of HFC was approximately 26°, and HFC was found to be composed of various amino acids, including glycine, proline, and hydroxyproline. At a concentration of 0.2 mg/mL, HFC promoted cell viability, and significantly up-regulated the expression of osteogenic markers (RUNX2, ALP, OPN, and OCN), as well as endothelial markers (CD31, VE-cadherin, and VEGFR2). Western blot results indicated that treatment of BMSCs with 0.2 mg/mL HFC could activate the MAPK/ERK signaling pathway and then increase the protein level of RUNX2, while treatment with PD98059, a specific inhibitor of ERK1/2, could significantly inhibit the expression of P-ERK and RUNX2. Interestingly, real-time PCR demonstrated that HFC inhibited the expression of adipogenic markers (LPL and ADFP) and chondrogenic markers (aggrecan and COLII), whereas it had no effect on neural differentiation markers (MAP2 and β3-tubulin). In summary, this study suggests that without the use of any additional inducing reagent, HFC has the potential to actively promote osteogenic and endothelial differentiation because of its high hydrophilicity and the optimal extracellular microenvironment supplied by its amino acids. This research also revealed that HFC inhibited adipogenic and chondrogenic differentiation, but it had no influence on the neural differentiation of rat bone marrow mesenchymal stem cells (rBMSCs).

Biomaterials for tissue engineering

Biomaterials serve as an integral component of tissue engineering. They are designed to provide architectural framework reminiscent of native extracellular matrix in order to encourage cell growth and eventual tissue regeneration. Bone and cartilage represent two distinct tissues with varying compositional and mechanical properties. Despite these differences, both meet at the osteochondral interface. This article presents an overview of current biomaterials employed in bone and cartilage applications, discusses some design considerations, and alludes to future prospects within this field of research.