Hyok Jin Seo

Asiaticoside enhances normal human skin cell migration, attachment and growth in vitro wound healing model.

Wound healing proceeds through a complex collaborative process involving many types of cells. Keratinocytes and fibroblasts of epidermal and dermal layers of the skin play prominent roles in this process. Asiaticoside, an active component of Centella asiatica, is known for beneficial effects on keloid and hypertrophic scar. However, the effects of this compound on normal human skin cells are not well known. Using in vitro systems, we observed the effects of asiaticoside on normal human skin cell behaviors related to healing. In a wound closure seeding model, asiaticoside increased migration rates of skin cells. By observing the numbers of cells attached and the area occupied by the cells, we concluded that asiaticoside also enhanced the initial skin cell adhesion. In cell proliferation assays, asiaticoside induced an increase in the number of normal human dermal fibroblasts. In conclusion, asiaticoside promotes skin cell behaviors involved in wound healing; and as a bioactive component of an artificial skin, may have therapeutic value.

Biological Advantages of Porous Hydroxyapatite Scaffold Made by Solid Freeform Fabrication for Bone Tissue Regeneration

Presently, commercially available porous bone substitutes are manufactured by the sacrificial template method, direct foaming method, and polymer replication method (PRM). However, current manufacturing methods provide only the simplest form of the bone scaffold and cannot easily control pore size. Recent developments in medical imaging technology, computer-aided design, and solid freeform fabrication (SFF), have made it possible to accurately produce porous synthetic bone scaffolds to fit the defected bone shape. Porous scaffolds were fabricated by SFF and PRM for a comparison of physical and mechanical properties of scaffold. The suggested three-dimensional model has interconnected cubic pores of 500 μm and its calculated porosity is 25%. Whereas hydroxyapatite scaffolds fabricated by SFF had connective macropores, those by PRM formed a closed pore external surface with internally interconnected pores. SFF was supposed to be a proper method for fabricating an interconnected macroporous network. Biocompatibility was confirmed by testing the cytotoxicity, hemolysis, irritation, sensitization, and implantation. In summary, the aim was to verify the safety and efficacy of the scaffolds by biomechanical and biological tests with the hope that this research could promote the feasibility of using the scaffolds as a bone substitute.

Control of neonatal human dermal fibroblast migration on poly(lactic-co-glycolic acid)-coated surfaces by electrotaxis

Many types of cells respond to applied direct current electric fields (dcEFs) by directional cell migration, a phenomenon called galvanotaxis or electrotaxis. In this study, electrotaxis was used to control cell migration. We designed a new electrotaxis incubator and chamber system to facilitate long‐term (> 12 h) observation and to allow for alterations to the direction of the current. Poly(lactic‐co‐glycolic acid) (PLGA) was coated onto surfaces to mimic a commonly used tissue‐engineering scaffolding environment. Neonatal human dermal fibroblasts (nHDFs) were grown on PLGA‐coated surfaces and exposed to EFs at increasing currents in the range 0–1 V/cm. These cells migrated toward the cathode during 3 h of dcEF stimulation; however, the migration speed decreased with increasing electric fields. Cells exposed to dcEFs in the range 1–2 V/cm showed no changes to migration speed or x forward migration indices (xFMIs) and the cells continued to move toward the cathode. nHDFs showed directional migration towards the cathode in direct current (dc) EFs (1 V/cm) and they moved in the opposite direction when the polarity of the dcEF was reversed. Reorganization of the actin cytoskeleton and polarization of the Golgi apparatus were evaluated by immunostaining, which showed that the actin cytoskeleton elongated towards the cathode and the Golgi apparatus polarized in the direction of the dcEF. This study revealed that cell migration could potentially be controlled on PLGA scaffolds through electrotaxis. Copyright

Titanium surface modification by using microwave-induced argon plasma in various conditions to enhance osteoblast biocompatibility

BackgroundTitanium is a well proven implantable material especially for osseointegratable implants by its biocompatibility and anti-corrosive surface properties. Surface characteristics of the implant play an important role for the evolution of bone tissue of the recipient site. Among the various surface modification methods, plasma treatment is one of the promising methods for enhance biocompatibility. We made microwave-induced argon plasma at atmospheric pressure to improve in titanium surface biocompatibility.ResultsVarious states of emission spectra from excited species-argon, nitrogen atoms and oxygen atoms were observed. The electron energy band structures are the unique characteristics of atoms and functional groups. Microwave-induced argon plasma treatment changed the titanium surface to be very hydrophilic especially on the 5 s short treatment and 30 s, 90 s long treatment samples that detected by contact angle measurement. MC3T3-E1 attachment and proliferation assay significantly increased in 5 s at short treatment, 30 s, and 90 s at long treatment after 5 days incubation.ConclusionsResult indicated that microwave-induce argon plasma treatment would be an effective method to modify titanium surface for enhancing cell-material interactions.

Resveratrol Inhibits Phenotype Modulation by Platelet Derived Growth Factor-bb in Rat Aortic Smooth Muscle Cells

Dedifferentiated vascular smooth muscle cells (VSMCs) are phenotypically modulated from the contractile state to the active synthetic state in the vessel wall. In this study, we investigated the effects of resveratrol on phenotype modulation by dedifferentiation and the intracellular signal transduction pathways of platelet derived growth factor-bb (PDGF-bb) in rat aortic vascular smooth muscle cells (RAOSMCs). Treatment of RAOSMCs with resveratrol showed dose-dependent inhibition of PDGF-bb-stimulated proliferation. Resveratrol treatment inhibited this phenotype change and disassembly of actin filaments and maintained the expression of contractile phenotype-related proteins such as calponin and smooth muscle actin-alpha in comparison with only PDGF-bb stimulated RAOSMC. Although PDGF stimulation elicited strong and detectable Akt and mTOR phosphorylations lasting for several hours, Akt activation was much weaker when PDGF was used with resveratrol. In contrast, resveratrol only slightly inhibited phosphorylations of 42/44 MAPK and p38 MAPK. In conclusion, RAOSMC dedifferentiation, phenotype, and proliferation rate were inhibited by resveratrol via interruption of the balance of Akt, 42/44MAPK, and p38MAPK pathway activation stimulated by PDGF-bb.

Fabrication of three-dimensional poly(lactic-co-glycolic acid) mesh by electrospinning using different solvents with dry ice

AbstractScaffolds used in tissue engineering are usually porous for providing a passage and cell infiltration. In this study, we have investigated the effects of vapor pressure of solvents during electrospinning with dry ice on the pore sizes of the poly(lactic-co-glycolic acid) (PLGA) meshes and the cell behaviors in these meshes. The meshes fabricated with dry ice using 1,1,1,3,3,3,-hexafluoro-2-propanol (HFIP), which was the lowest vapor pressure of the experimental solvents, were not significantly different on the fiber connections as compared to those fabricated without dry ice. When electrospinning was processed using acetone with dry ice, numerous beads were observed in the meshes. The meshes which were fabricated using the tetrahydrofuran/dimethylformamide (THF/DMF) admixture with dry ice had loose connections between the fibers and showed large voids. In addition, the infiltration and the attachment of cells increased on these meshes due to large voids. Therefore, dry ice during electrospinning could cause an increase in pore size; however, these electrospinning processing was sensitive to the vapor pressure of the experimental solvent.

Effect of PLGA Nano-Fiber/Film Composite on HUVECs for Vascular Graft Scaffold

Potential application of the PLGA nanofiber/ film composite for vascular tissue regeneration was examined. The composite was prepared by solvent-casting and electro-spinning method. The PLGA nano-fiber was coated on the surface of the prepared PLGA film. The surface of the composite film was characterized by contact angle measurement and scanning electron microscope (SEM). The film made by only nano-fiber showed more hydrophobic than control (PLGA film made by solvent-casting); however, optimal amount of nano fibers coating could assist cell adhesion and spreading on the film. For human umbilical vein endothelial cells (HUVECs) proliferation on 6-day culture, the NF-30 (30min. nano-fiber spread specimen) composite was 1.5 times more cells proliferated than that of the NFO-1h (nano-fiber only specimen). The SEM images showed that the HUVECs on the NF-30 specimen spread widely than the other groups. The result indicates that the nano-fibers on films have an effect on cell adhesion and spreading because the adequate amount of nano-fibers on the surface of the films provide similar structure to natural ECM morphology. Conclusively, nanofiber/ film composite provided an adequate environment for cell proliferation and showed the potential application for vascular tissue regeneration.

Plasma treatment induces internal surface modifications of electrospun poly(L-lactic) acid scaffold to enhance protein coating

Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion and maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold...