Jooyeon Park

Graphene-Regulated Cardiomyogenic Differentiation Process of Mesenchymal Stem Cells by Enhancing the Expression of Extracellular Matrix Proteins and Cell Signaling Molecules

The potential of graphene as a mesenchymal stem cell (MSC) culture substrate to promote cardiomyogenic differentiation is demonstrated. Graphene exhibits no sign of cytotoxicity for stem cell culture. MSCs are committed toward cardiomyogenic lineage by simply culturing them on graphene. This may be attributed, at least partially, to the regulation of expression levels of extracellular matrix and signaling molecules.

Graphene oxide flakes as a cellular adhesive: prevention of reactive oxygen species mediated death of implanted cells for cardiac repair.

Mesenchymal stem cell (MSC) implantation has emerged as a potential therapy for myocardial infarction (MI). However, the poor survival of MSCs implanted to treat MI has significantly limited the therapeutic efficacy of this approach. This poor survival is primarily due to reactive oxygen species (ROS) generated in the ischemic myocardium after the restoration of blood flow. ROS primarily causes the death of implanted MSCs by inhibiting the adhesion of the MSCs to extracellular matrices at the lesion site (i.e., anoikis). In this study, we proposed the use of graphene oxide (GO) flakes to protect the implanted MSCs from ROS-mediated death and thereby improve the therapeutic efficacy of the MSCs. GO can adsorb extracellular matrix (ECM) proteins. The survival of MSCs, which had adhered to ECM protein-adsorbed GO flakes and were subsequently exposed to ROS in vitro or implanted into the ischemia-damaged and reperfused myocardium, significantly exceeded that of unmodified MSCs. Furthermore, the MSC engraftment improved by the adhesion of MSCs to GO flakes prior to implantation enhanced the paracrine secretion from the MSCs following MSC implantation, which in turn promoted cardiac tissue repair and cardiac function restoration. This study demonstrates that GO can effectively improve the engraftment and therapeutic efficacy of MSCs used to repair the injury of ROS-abundant ischemia and reperfusion by protecting implanted cells from anoikis.

Enhanced skin wound healing by a sustained release of growth factors contained in platelet-rich plasma

Platelet-rich plasma (PRP) contains growth factors that promote tissue regeneration. Previously, we showed that heparin-conjugated fibrin (HCF) exerts the sustained release of growth factors with affinity for heparin. Here, we hypothesize that treatment of skin wound with a mixture of PRP and HCF exerts sustained release of several growth factors contained in PRP and promotes skin wound healing. The release of fibroblast growth factor 2, platelet-derived growth factor-BB, and vascular endothelial growth factor contained in PRP from HCF was sustained for a longer period than those from PRP, calcium-activated PRP (C-PRP), or a mixture of fibrin and PRP (F-PRP). Treatment of full-thickness skin wounds in mice with HCF-PRP resulted in much faster wound closure as well as dermal and epidermal regeneration at day 12 compared to treatment with either C-PRP or F-PRP. Enhanced skin regeneration observed in HCF-PRP group may have been at least partially due to enhanced angiogenesis in the wound beds. Therefore, this method could be useful for skin wound treatment.

The effect of the delivery carrier on the quality of bone formed via bone morphogenetic protein-2.

Bone morphogenetic protein-2 (BMP-2) can induce bone generation in vivo. Although many studies have demonstrated an increased quantity of regenerated bone after the delivery of BMP-2 using various carriers, little is known about the effect of the carrier type on the quality of the regenerated bone. In this study, we compared the quality of regenerated bone when BMP-2 was delivered with either β-tricalcium phosphate (β-TCP) or heparin-conjugated fibrin (HCF), both of which are shown to be excellent carriers for BMP-2. The profile of the release of BMP-2 was not significantly different between the delivery carriers. However, the alkaline phosphate activity of cultured osteoblasts was significantly higher when BMP-2 was delivered using HCF than when BMP-2 was delivered using β-TCP. To evaluate the quality of the regenerated bone, both types of BMP-2 carriers were implanted into critical-sized calvarial defects in mice. Eight weeks after implantation, the regenerated bone was examined by histomorphometry. Importantly, the treatment using HCF + BMP-2 and β-TCP + BMP-2 resulted in similar bone formation areas. However, the treatment using HCF + BMP-2 resulted in significantly higher bone density than the treatment using β-TCP + BMP-2. This study shows that a BMP-2 delivery carrier can modulate the quality of bone regenerated via BMP-2 delivery.

Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets

Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells.

Three‐Dimensional Scaffolds of Carbonized Polyacrylonitrile for Bone Tissue Regeneration

Carbon-based materials have been extensively studied for stem cell culture. However, difficulties associated with engineering pure carbon materials into 3D scaffolds have hampered applications in tissue engineering and regenerative medicine. Carbonized polyacrylonitrile (cPAN) could be a promising alternative, as cPAN is a highly ordered carbon isomorph that resembles the graphitic structure and can be easily processed into 3D scaffolds. Despite the notable features of cPAN, application of cPAN in tissue engineering and regenerative medicine have not been explored. This study, for the first time, demonstrates the fabrication of microporous 3D scaffolds of cPAN and excellent osteoinductivity of cPAN, suggesting utility of 3D cPAN scaffolds as synthetic bone graft materials. The combination of excellent processability and unique bioactive properties of cPAN may lead to future applications in orthopedic regenerative medicine.

Integration of mesenchymal stem cells with nanobiomaterials for the repair of myocardial infarction

The integration of nanobiomaterials with stem cells represents a promising strategy for the treatment of myocardial infarction. While stem cells and nanobiomaterials each demonstrated partial success in cardiac repair individually, the therapeutic efficacy of the clinical settings for each of these has been low. Hence, a combination of nanobiomaterials with stem cells is vigorously studied to create synergistic effects for treating myocardial infarction. To date, various types of nanomaterials have been incorporated with stem cells to control cell fate, modulate the therapeutic behavior of stem cells, and make them more suitable for cardiac repair. Here, we review the current stem cell therapies for cardiac repair and describe the combinatorial approaches of using nanobiomaterials and stem cells to improve therapeutic efficacy for the treatment of myocardial infarction.

Platelet-rich plasma enhances the dermal regeneration efficacy of human adipose-derived stromal cells administered to skin wounds.

The administration of human adipose-derived stromal cells (hASCs) enhances skin wound healing. However, poor survival of hASCs that are administered to avascular wound regions may limit the therapeutic efficacy of the hASCs. The aim of this study was to determine whether the coadministration of platelet-rich plasma (PRP) and hASCs enhanced the skin wound-healing efficacy of hASCs. Skin regeneration was examined in skin wounds of athymic mice that were either untreated or treated with hASCs, PRP, or both hASCs and PRP. Coadministration of PRP and hASCs resulted in better skin regeneration than hASC administration alone in part by significantly improving the proliferation of administered hASCs by the angiogenic growth factor secretion of the hASCs and surrounding mouse host cells in the wound areas and by promoting neovascularization in the wound beds.

Engineering structures and functions of mesenchymal stem cells by suspended large-area graphene nanopatterns

Inspired by the hierarchical nanofibrous and highly oriented structures of natural extracellular matrices, we report a rational design of chemical vapor deposition graphene-anchored scaffolds that provide both physical and chemical cues in a multilayered organization to control the adhesion and functions of cells for regenerative medicine. These hierarchical platforms are fabricated by transferring large graphene film onto nanogroove patterns. The top graphene layer exhibits planar morphology with slight roughness (~20 nm between peaks) due to the underlying topography, which results in a suspended structure between the nanoridges. We demonstrate that the adhesion and differentiation of human mesenchymal stem cells were sensitively controlled and enhanced by the both the nanotopography and graphene cues in our scaffolds. Our results indicate that the layered physical and chemical cues can affect the apparent cell behaviors, and can synergistically enhance cell functionality. Therefore, these suspended graphene platforms may be used to advance regenerative medicine.

Efficient Bone Regeneration Induced by Bone Morphogenetic Protein-2 Released from Apatite-Coated Collagen Scaffolds

Abstract Bone morphogenetic proteins (BMPs) are the most potent osteoinductive growth factors. Clinically utilized BMP-2 uses a type-I collagen scaffold as a carrier. Here we hypothesized that an apatite coating on a type-I collagen scaffold would prolong the BMP-2 release period and enhance bone regeneration in calvarial defects in mice. Apatite coating was achieved by incubating collagen scaffolds in simulated body fluid. BMP-2 release kinetics and bioactivity were evaluated by enzyme-linked immunosorbent assay and alkaline phosphatase activity measurement of cultured osteoblasts. Computed tomography and histomorphometry were performed eight weeks after various doses of BMP-2 were delivered to mouse calvarial defects using either non-modified or apatite-coated collagen scaffolds. Apatite-coated collagen scaffolds released 91.8 ± 11.5% of the loaded BMP-2 over 13 days in vitro, whereas non-modified collagen scaffolds released 98.3 ± 2.2% over the initial one day. The in vivo study showed that BMP-2 delivery with apatite-coated collagen scaffolds resulted in a significantly greater bone formation area and higher bone density than that with non-modified collagen scaffolds. This study suggests that simple apatite coating on collagen scaffolds can enhance the bone regeneration efficacy of BMP-2 released from collagen scaffolds.