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Several factors are involved in angiogenesis. To form new blood vessels, we fabricated vehicles carrying an angiogenesis-related peptide (apelin) and gene (vascular endothelial growth factor (VEGF)165) that were internalized by human mesenchymal stem cells (hMSCs). These non-toxic poly-(DL)-lactic-co-glycolic acid (PLGA) nanoparticles (NPs) easily entered hMSCs without cytotoxicity. The negatively charged outer surface of PLGA NPs can be easily complexed with highly positively charged polyethylenimine (PEI) to deliver genes into cells. PLGA NPs complexed with PEI could be coated with negatively charged VEGF plasmid DNA and loaded with apelin. The physical characteristics of these PLGA NPs were determined by size distribution, gel retardation, and morphological analyses. Transfection of VEGF-coated apelin-loaded PLGA NPs resulted in the differentiation of hMSCs into endothelial cells and vascular formation in Matrigel in vitro. Following injection of hMSCs transfected with these PLGA NPs into an ischemic hind limb mouse model, these cells differentiated into endothelial cells and accelerated neovascularization.

During embryogenesis, specific proteins expressed in cells have key roles in the formation of differentiated cells and tissues. Delivery of specific proteins into specific cells, both in vitro and in vivo, has proved to be exceedingly difficult. In this study, we developed a safe and efficient protein delivery system using encapsulation of proteins into biodegradable poly-(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs). The PLGA NPs were used to deliver proteins into human mesenchymal stem cells (hMSCs). Fluorescent markers loaded into the PLGA NPs were used to verify the internalization of NPs into hMSCs using FACS analysis and confocal microscopy. With these methods, we demonstrated that the encapsulated model proteins are readily delivered into hMSCs, released from the NP vehicles, and, finally, moved into the cytosols. Using chondrogenesis-related proteins such as aggrecan and cartilage oligomeric matrix protein (COMP), chondrogenic differentiation of hMSCs treated with aggrecan and COMP encapsulated PLGA NPs was clearly observed and caused to differentiate into chondrocytes.

Drugs, proteins, and cells can be macro- and micro-encapsulated by unique materials that respond to specific stimuli. The phases and hydrophobic interactions of these materials are reversibly altered by environmental stimuli such as pH and temperature. These changes can lead to self-assembly of the materials, which enables controlled drug release and safe gene delivery into cells and tissues. The fate of stem cells delivered by such methods is of great interest. The formation of transgenic tissues requires genes to be delivered safely into stem cells. A cell tracing vehicle and a gene delivery carrier were simultaneously introduced into human mesenchymal stem cells (hMSCs). A thermo-sensitive hydrogel, poly(N-isopropylacrylamide-co-acrylic acid) (p(NiPAAm-co-AAc)), was created to generate self-assembled nanoparticles with nanogel characteristics. Hydrophobic interactions mediated the binding of the carboxyl group on the outside of p(NiPAAm-co-AAc) with the amine group of iron oxide. Nanogels carrying iron oxide and a fluorescent dye were complexed with specific genes. These nanogels could be internalized by hMSCs, and the transplantation of these cells into mice was monitored by in vivo imaging. Self-assembled p(NiPAAm-co-dAAc) nanogels complexed with green fluorescent protein were highly expressed in hMSCs and are a potential material for gene delivery.

Microparticulated types of scaffolds have been widely applied in stem cell therapy and the tissue engineering field for the regeneration of wound tissues. During application of simple genes or growth factors and cell delivery vehicles, we designed a method that employs dexamethsone loaded PLGA microspheres consisting of polyplexed SOX9 genes plus heparinized TGF-β 3 on the surface of polymeric microspheres prepared using a layer-by-layer (LbL) method. The fabrication of the polyplexed SOX9 genes plus heparinized TGF-β 3 and their subsequent coating onto dexamethsone loaded PLGA microspheres represents a method for functionalization of the polymeric matrix. The use of SOX9 gene plus heparinized TGF-β 3 coated dexamethsone loaded PLGA microspheres was evaluated to determine their potential as both gene carriers and cell delivery vehicle. By adhesion of hMSCs onto SOX9 gene plus heparinized TGF-β 3 coated dexamethsone loaded PLGA microspheres, the chondrogenesis-related specific genes of collagen type II were increased 30 times comparing to control. Also, the specific extracellular matrix of glycosaminoglycan (GAG) production of hMSCs adhered onto SOX9 gene plus heparinized TGF-β 3 coated dexamethasone loaded PLGA microspheres increased more 2.5 times than control group. Not only in vitro culture but in vivo results, the specific genes of COMP, aggrecan, collagen type II, and SOX9 showed much more gene expressions such as 20, 15, 10, 8 times.

In this study, bone marrow-derived mesenchymal stem cells (MSCs), adipose-derived mesenchymal stem cells (ASCs) and dedifferentiated chondrocytes were transfected with SOX5, 6, and 9 genes (SOX Trio) and grown under pellet culture conditions (encapsulated in a fibrin hydrogel) to evaluate the chondrogenic potential in vitro and in vivo. RT-PCR, real-time quantitative PCR (qPCR), histology, and immunohistochemical assays were performed to determine the chondrogenic potential of the stem cells and dedifferentiated chondrocytes. Chondrogenic genes and proteins were more highly expressed in SOX Trio-expressing cells than in untransfected cells. In addition, not only specific genes and proteins, but cartilage-forming tissues were observed in nude mice transplanted with fibrin hydrogel encapsulated SOX Trio-expressing MSCs, ASCs, and dedifferentiated chondrocytes. Both in vitro and in vivo analyses revealed that fibrin hydrogel encapsulated cultured or transplanted cells transfected with the SOX Trio successfully differentiated into mature chondrocytes and could be used for the reconstruction of hyaline articular cartilage.

In this study, to drive efficient adipogenic differentiation, the adipogenic transcription factors C/EBP-α and C/EBP-β fused to green fluorescent protein (GFP) or red fluorescent protein (RFP) were complexed with poly-ethyleneimine (PEI) coupled with biodegradable PLGA nanospheres and delivered to human mesenchymal stem cell (hMSC). FACS analysis revealed that the transfection efficiency of C/EBP-α, C/EBP-β, or both genes complexed with PEI-coated PLGA nanospheres was 12.59%, 21.74%, and 28.96% of hMSCs. Expression and localization of C/EBP-α and C/EBP-β were confirmed by Western blotting and confocal laser microscopy. Overexpression of exogenous C/EBP-α and C/EBP-β significantly elevated adipogenic differentiation processes as indicated by RT-PCR, real-time PCR, Western blotting, histology, and immunofluorescence microscopy. During adipogenesis, PEI-coupled PLGA nanospheres complexed with C/EBP-α and C/EBP-β greatly increased the adipogenic capability of in vitro cultured cells, as well of in vivo transplanted cells. The expression of genes and proteins specific to adipogenic differentiation in hMSCs was significantly elevated compared to the controls.

Target gene transfection for desired cell differentiation has recently become a major issue in stem cell therapy. For the safe and stable delivery of genes into human mesenchymal stem cells (hMSCs), we employed a non-viral gene carrier system such as polycataionic polymer, poly(ethyleneimine) (PEI), polyplexed with a combination of SOX5, 6, and 9 fused to green fluorescence protein (GFP), yellow fluorescence protein (YFP), or red fluorescence protein (RFP) coated onto PLGA nanoparticles. The transfection efficiency of PEI-modified PLGA nanoparticle gene carriers was then evaluated to examine the potential for chondrogenic differentiation by carrying the exogenous SOX trio (SOX5, 6, and 9) in hMSCs. Additionally, use of PEI-modified PLGA nanoparticle gene carriers was evaluated to investigate the potential for transfection efficiency to increase the potential ability of chondrogenesis when the trio genes (SOX5, 6, and 9) polyplexed with PEI were delivered into hMSCs. SOX trio complexed with PEI-modified PLGA nanoparticles led to a dramatic increase in the chondrogenesis of hMSCs in in vitro culture systems. For the PEI/GFP and PEI/SOX5, 6, and 9 genes complexed with PLGA nanoparticles, the expressions of GFP as reporter genes and SOX9 genes with PLGA nanoparticles showed 80% and 83% of gene transfection ratios into hMSCs two days after transfection, respectively.

In stem cell therapy, transfection of specific genes into stem cells is an important technique to induce cell differentiation. To perform gene transfection in human mesenchymal stem cells (hMSCs), we designed and fabricated a non-viral vector system for specific stem cell differentiation. Several kinds of gene carriers were evaluated with regard to their transfection efficiency and their ability to enhance hMSCs differentiation. Of these delivery vehicles, biodegradable poly (DL-lactic-co-glycolic acid) (PLGA) nanoparticles yielded the best results, as they complexed with high levels of plasmid DNA (pDNA), allowed robust gene expression in hMSCs, and induced chondrogenesis. Polyplexing with polyethylenimine (PEI) enhanced the cellular uptake of SOX9 DNA complexed with PLGA nanoparticles both in vitro and in vivo. The expression of enhanced green fluorescent protein (EGFP) and SOX9 increased up to 75% in hMSCs transfected with PEI/SOX9 complexed PLGA nanoparticles 2 days after transfection. SOX9 gene expression was evaluated by RT-PCR, real time-qPCR, glycosaminoglycan (GAG)/DNA levels, immunoblotting, histology, and immunofluorescence.

The micro-environment is an important factor in the differentiation of cultured stem cells for the purpose of site specific transplantation. In an attempt to optimize differentiation conditions, co-culture systems composed of both stem cells and primary cells or cell lines were used in hydrogel with in vitro and in vivo systems. Stem cells encapsulated in hydrogel, under certain conditions, can undergo increased differentiation both in vitro and in vivo; therefore, reconstruction of transplanted stem cells in a hydrogel co-culture system is important for tissue regeneration. In order to construct such a co-culture system, we attempted to create a hydrogel scaffold which could induce neo-tissue growth from the recipient bed into the material. This material would enable encapsulation of stem cells in vitro after which they could be transferred to an in vivo system utilizing nude mice. In this case, the hydrogel was implanted in the subfascial space of nude mice and excised 4 weeks later. Cross-sections of the excised samples were stained with von Kossa or safranin-O and tubular formations into the gel were observed with and tested by doppler imaging. The data showed that the hydrogel markedly induced growth of osteogenic, chondrogenic, and vascular-rich tissue into the hydrogel by 4 weeks, which surpassed that after transplantation in a co-culture system. Further, a co-culture system with differentiated cells and stem cells potentially enhanced chondrogenesis, osteogenesis, and vascularization. These findings suggest that a co-culture system with hydrogel as scaffold material for neo-tissue formation is a useful tools for multi-lineage stem cell differentiation.

BACKGROUND Heparin binds growth factors to form a stable complex that maintains the biological activity and can retard the release pattern. To differentiate the embedded the stem cells, heparin-bind transforming growth factor (TGF)-beta3 was mixed with rabbit mesenchymal stem cells encapsulated with thermo-reversible hydrogel. It is suggested that the heparin-bound TGF-beta3 would help to increase the chondrogenic differentiation of rabbit mesenchymal stem cells in thermo-reversible hydrogel. METHODS To determine the optimal condition for neocartilage formation, we characterized hydrogel constructs with growth factor release profiles, confocal laser microscopy, reverse transcription-polymerase chain reaction analysis, and histology. RESULTS Reverse transcription-polymerase chain reaction analysis of the resultant cartilage tissue revealed that a thermo-reversible hydrogels with a heparin-bound TGF-beta3 was optimal for cartilage tissue formation as measured by production of collagen Type II, aggrecan, and SOX9, and cartilage oligomeric matrix protein gene expression. Additionally, the proliferation rate and cartilage specific ECM production were both significantly greater in the presence of heparin-bound TGF-beta3 than in the control. The amount of cartilage-associated ECM proteins was examined by immunohistochemical staining (collagen type II), Safranin-O staining, and Alcian blue staining. CONCLUSIONS These data indicate the potential use of heparin-binding TGFbeta-3 for reconstruction of neocartilage formation.

The aim of this study was to assess the efficacy of ectopic bone formation in a three-dimensional hybrid scaffold in combination with hydroxyapatite (HA) and poly(NiPAAm-co-AAc) as an injectable vehicle in the form of a supporting matrix for the osteogenic differentiation of rabbit mesenchymal stem cells (MSCs). Osteogenic differentiation of MSCs in the hybrid scaffold was greatly influenced by the addition of growth factors. When the osteoinduction activity of hybrid scaffold was studied following implantation into the back subcutis of nude mouse in terms of histological and biochemical examinations, significantly homogeneous bone formation was histologically observed throughout the hybrid scaffolds containing growth factor (BMP-2: bone morphogenic protein-2). The level of alkaline phosphatase activity and osteocalcin content at the implanted sites of hybrid scaffolds were significantly high for the perfusion group compared with those in static culture group. We conclude that combination of MSC-seeded hybrid scaffold containing BMP-2 was a promising method by which to enhance in vitro osteogenic differentiation of MSC and in vivo ectopic bone formation.

For electrical stimulation of hMSCs, gold nanoparticles were coated onto polyethyleneimine coated glass cover slips. The effects of pulsed or constant electrical stimulation upon cytotoxicity and differentiation of hMSCs were examined. The effects of co culturing hMSCs with neuronal cells were also tested. The neuronal differentiation of the stem cells was evaluated by determining the expression of neuron-specific genes and proteins using RT-PCR and Western blotting. Morphological changes were evaluated by scanning electron microscopy. The hMSCs co-cultured with mature neuronal cells and stimulated with electrical shock showed the greatest level of neurite outgrowth (150 mm) and smaller cell body sizes.

Quantum dot (QDs) have been employed as bioimaging agents and delivery vehicles for gene therapeutics in several types of cells. In this study, we fabricated multiple QD bundled nanoparticles (NPs) to investigate the effect of QD size and poly(ethylenimine) (PEI) coating on the efficiency of gene delivery into human mesenchymal stem cells (hMSCs). Several types of QDs, which exhibit different ranges of particle size and fluorescence when employed, were coated with PEI to alter their negative charges and to enable them to be bundled into larger particles. Using specific wavelengths of QDs for bioimaging, gene-complexed QD bundled NPs were easily detected in the hMSCs using several different methods such as fluorescence-activated cell sorter, confocal laser scanning microscopy, and in vivo optical imaging. These PEI-coated, bundled QD NPs exhibited significantly higher gene transfection efficacy than single-type QDs. Particularly, the largest QD bundled NPs examined, QD655, had a much higher uptake capability and greater gene expression ability than the other QD NPs (QD525, QD565, and QD605). We believe that our findings help to enrich knowledge of design considerations that will aid in the engineering of QD NPs for stem cell application in the future.

Directing the controlled differentiation and tracking of stem cells is essential to achieve successful stem cell therapy. In this work, we describe a multi-modal (MR/optical) transfection agent (MTA) for efficient gene delivery and cell tracking of human mesenchymal stem cells (hMSCs). The MTA was synthesized through a facile two-step approach with 1) ligand exchange of a catechol-functionalized polypeptide (CFP) and 2) chemical immobilization of fluorescence labelled cationic polymer via aminolysis reaction. Cationic polymer-immobilized MTAs with size of ∼40 nm exhibit greatly enhanced colloidal stability in aqueous solution. In addition, the MTAs were capable of binding DNA molecules for transfection. The MTA/pDNA complex showed relatively good transfection efficiency in hMSCs (compared to the commercial transfection agent, Lipofectamine) and good biocompatibility. MTA-treated hMSCs were successfully visualized after transplantation via MR and optical imaging system over 14 days. These studies highlight the challenges associated with the potential advantages of designing multi-modal nanostructured materials as tools for genetic materials delivery and cell-tracking in stem cell therapy.

Specific vehicles are necessary for safe and efficient gene transfection into cells. Nano-type hydrogels (nanogel) comprising carboxymethylcellulose (CMC) complexed with branched type cationic poly(ethleneimine) (bPEI) were used as gene delivery vehicles. When complexes of CMC and bPEI were used in vitro, CMC showed nano-gel type properties, as shown by the results of a viscosity test, and bPEI showed low cytotoxicity comparing to bPEI alone. Together, these properties are shown to maintain high gene transfection efficiency. In viability experiments using three types of adult stem cells, cell viability varied depending on the branch form of PEI and whether or not it is in a complex with CMC. The gene delivery efficacy showed that the CMC nanogel complexed with bPEI (CMC-bPEI) showed more uptaking and gene transfection ability in hMSCs comparing to bPEI alone. In osteogenesis, the CMC-bPEI complexed with OSX pDNA showed more easy internalization than bPEI alone complexed with OSX pDNA in hMSCs. Specific genes and proteins related in osteogenic differentiation were expressed in hMSCs when the CMC-bPEI complexed with OSX pDNA was used.

In this study, synergistic effects of electrical stimulation and exogenous Nurr1 gene expression were examined to induce the differentiation of human mesenchymal stem cells (hMSCs) into nerve cells in in vitro culture system. A two-step procedure was designed to evaluate the effects of electrical stimulus and exogenous gene delivery for inducing neurogenesis. First, an electrical stimulation device was designed using gold nanoparticles adsorbed to the surface of a cover glass. Gold nanoparticles, as an electrical conductor for stem cells, are well-defined particles adsorbed to a polyethyleneimine (PEI)-coated cover glass. The nanoparticle morphology was examined by scanning electron microscope (SEM). Second, a plasmid carrying Nurr1 cDNA was complexed with biodegradable poly-(DL)-lactic-co-glycolic acid (PLGA) nanoparticles to support neurogenesis. To evaluate the neuronal differentiation of stem cells mediated by the treatment with either electrical stimulation and exogenous Nurr1 gene delivery, or both, the expression of neuron-specific genes and proteins was examined by RT-PCR and Western blotting. Cells transfected with exogenous Nurr1 genes plus electrical stimulation (250 mV for 1000 s) showed the greatest level of neurite outgrowth with a mean neurite length of 150 μm. Neurite length in cells treated with only one stimulus was not significant, approximately 10-20 μm. These results indicate that electrical stimulation and exogenous Nurr1 gene expression together may be adequate to induce nerve regeneration using stem cells.

Some genes expressed in stem cells interrupt and/or enhance differentiation. Therefore, the aim of this study was to inhibit the expression of unnecessary genes and enhance the expression of specific genes involved in stem cell differentiation by using small interfering RNA (siRNA) and plasmid DNA (pDNA) incorporated into cationic polymers as co-delivery factors. To achieve co-delivery of siRNA and pDNA to human mesenchymal stem cells (hMSCs), two different genes were complexed with poly(ethyleneimine) (PEI) and then coated onto poly(lactide-co-glycolic acid) (PLGA) nanoparticles (NP). To evaluate co-delivery of siRNA and pDNA into hMSCs, cells were transfected with green fluorescence protein (GFP) pDNA (GFP pDNA) and GFP siRNA (GFP siRNA). The percentage of GFP-expressing hMSCs decreased from 25.35 to 3.7% after transfection with GFP-DNA/PLGA NP (NPs) or GFP siRNA/PLGA NPs, whereas GFP-DNA/PLGA NPs and scramble siRNA (MOCK)/PLGA NPs had no effect on GFP expression. hMSCs cotransfected with coSOX9-pDNA/NPs and Cbfa-1-siRNA/NPs were tested both in vitro and in vivo using gel retardation, dynamic light scattering (DLS), and scanning electron microscope (SEM). The expression of genes and proteins associated with chondrogenesis was evaluated by FACS, RT-PCR, real time-qPCR, Western blotting, immunohistochemistry, and immunofluorescence imaging.

In this study, several types of hMSCs, derived from bone marrow, adipose tissue, or amniotic fluid, were encapsulated in a fibrin hydrogel mixed with TGF-β3 and then evaluated for their capacity for differentiation in vitro and in vivo. For determination of stem cell differentiation, RT-PCR, real time quantitative PCR (qPCR), histology, and immunohistochemical assays were used for analysis of chondrogenesis. Using these analysis methods, several of the cultured hMSCS were found to highly express genes and proteins specific to cartilage forming tissues. Additionally, similar trends in expression were found in tissue recovered from nude mice transplanted with several types of hMSCs encapsulated in a fibrin hydrogel containing TGF-β3. The results of both in vitro and in vivo analyses showed that cultured or transplanted hMSCs mixed with TGF-β3 in a fibrin hydrogel differentiated into chondrocytes, suggesting that these cells would be suitable for reconstruction of hyaline articular cartilage.

In this study, mesenchymal stem cells (MSCs) embedded in biodegradable and water-swollen, elastic block copolymer scaffolds were assessed for MSC chondrogenesis. To determine the optimal conditions for chondrogenesis of the embedded rMSCs, transforming growth factor-beta 3 (TGF-beta 3) was physically conjugated with chondroitin sulfate (CS) and mixed into scaffolds, which were subsequently evaluated for the differentiation of transplanted rMSCs. In determination of CS-bound growth factors for chondrogenesis, scaffold mixed with rMSCs and TGF-beta 3 was then tested by growth factor release profiles, confocal laser microscopy, RT-PCR analysis, real time-QPCR, and histology. The results of several different analyses of the transplanted rMSCs embedded in the scaffolds showed that rMSCs coupled with a CS-bound TGF-beta 3 encapsulated scaffold evidenced superior cartilage tissue formation as measured by an assay of specific gene and protein expression. Moreover, the scaffold exhibited more rapid and more distinct morphology of differentiated rMSCs than was observed with other scaffolds, as determined by histology and immunochemical histology analysis. These results indicate that the elastic block copolymer scaffolds combined with a CS-bound TGF-beta 3 should prove very suitable matrix for cell-based cartilage tissue engineering.

In this study, in vivo studies, both nude mouse and rabbit cartilage defect, were tested for chondrogenesis using stem cells (SCs) using growth factor. Specifically, human mesenchymal stem cells (hMSCs) were embedded in a hydrogel scaffold, which was coencapsulated with transforming growth factor-β3 (TGF-β3). The specific extracellular matrices (ECMs) released from hMSCs transplanted into the animal were assessed via glycosaminoglycan (GAG)/DNA content, RT-PCR, real time-QPCR, immunohistochemical (IHC), and Safranin-O staining and were observed up to 7 weeks after injection. By detection of ECMs the GAG content per cell remained constant for all formulations, indicating that the dramatic increase in cell number for samples with TGF-β3 was accompanied by the maintenance of the cell phenotypes. The histological and IHC staining of the newly repaired tissues observed after treatment with TGF-β3 mixed with hMSCs evidenced hyaline cartilage-like characteristics. Moreover, the results observed with the animal model (rabbit) treated with hMSCs embedded in the growth factor-containing hydrogel indicate that the implantation of mixed cells with TGF-β3 may constitute a clinically efficient method for the regeneration of hyaline articular cartilage. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010

Polymeric microsphere system has been widely used in tissue-regeneration matrix and drug delivery systems. To apply these biomaterials as novel cell supporting matrix for stem cell delivery, we have devised a novel method for the fabrication of nanostructured 3D scaffolds that growth factor loaded heparin/poly(L-lysine) nanoparticles were physically attached on the positively charged surface of PLGA microspheres precoated with low molecular weight of poly(ethyleneimmine) (PEI) via a layer-by-layer (LbL) system. Based on a previous study, we have prepared poly(lactide-co-glycolide) (PLGA) microspheres harboring heparin/poly(L-lysine) loaded with growth factors. Growth factor loaded heparin/poly(L-lysine) nanoparticles, which were simply produced as polyion complex micelles (PICM) with diameters of 50-150 nm, were fabricated in the first step. Microsphere matrix (size, 20 approximately 80 nm) containing TGF-beta 3 showed a significantly higher number of specific lacunae phenotypes at the end of the 4 week study in vitro culture of mesenchymal stem cells. Thus, growth factor delivery of PLGA microsphere can be used to engineer synthetic extracellular matrix. This PLGA microsphere matrix containing TGF-beta 3 showed promise as coatings for implantable biomedical devices to improve biocompatibility and ensure in vivo performance.