Ye-Rang Yun

Fibroblast Growth Factors: Biology, Function, and Application for Tissue Regeneration

Fibroblast growth factors (FGFs) that signal through FGF receptors (FGFRs) regulate a broad spectrum of biological functions, including cellular proliferation, survival, migration, and differentiation. The FGF signal pathways are the RAS/MAP kinase pathway, PI3 kinase/AKT pathway, and PLCγ pathway, among which the RAS/MAP kinase pathway is known to be predominant. Several studies have recently implicated the in vitro biological functions of FGFs for tissue regeneration. However, to obtain optimal outcomes in vivo, it is important to enhance the half-life of FGFs and their biological stability. Future applications of FGFs are expected when the biological functions of FGFs are potentiated through the appropriate use of delivery systems and scaffolds. This review will introduce the biology and cellular functions of FGFs and deal with the biomaterials based delivery systems and their current applications for the regeneration of tissues, including skin, blood vessel, muscle, adipose, tendon/ligament, cartilage, bone, tooth, and nerve tissues.

Efficacy of mesoporous silica nanoparticles in delivering BMP-2 plasmid DNA for in vitro osteogenic stimulation of mesenchymal stem cells.

We report the ability of aminated mesoporous silica nanoparticles (MSN-NH2) with large mesopore space and positive-charged surface to deliver genes within rat mesenchymal stem cells (MSCs). The amine functionalized inorganic nanoparticles were complexed with bone morphogenetic protein-2 (BMP2) plasmid DNA (pDNA) to study their transfection efficiency in MSCs. Intracellular uptake of the complex BMP2 pDNA/MSN-NH2 occurred significantly, with a transfection efficiency of approximately 68%. Furthermore, over 66% of the transfected cells produced BMP2 protein. The osteogenic differentiation of the transfected MSCs was demonstrated by the expression of bone-related genes and proteins including bone sialoprotein, osteopontin, and osteocalcin. The MSN-NH2 delivery vehicle for BMP2 pDNA developed in this study may be a potential gene delivery system for bone tissue regeneration.

Administration of growth factors for bone regeneration

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the in vitro and in vivo performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Biointerface control of electrospun fiber scaffolds for bone regeneration: Engineered protein link to mineralized surface

Control over the interface of biomaterials that favors the initial adhesion and subsequent differentiation of stem cells is one of the key strategies in bone tissue engineering. Here we engineer the interface of biopolymer electrospun fiber matrices with a fusion protein of fibronectin 9-10 domain (FNIII9-10) and osteocalcin (OCN), aiming to stimulate mesenchymal stem cell (MSC) functions, including initial adhesion, growth and osteogenic differentiation. In particular, a specific tethering of FNIII9-10-OCN protein was facilitated by the hydroxyapatite (HA) mineralization of the biopolymer surface through a molecular recognition of OCN to the HA crystal lattice. The FNIII9-10-OCN anchorage to the HA-mineralized fiber was observed to be highly specific and tightly bound to preserve stability over a long period. Initial cell adhesion levels, as well as the spreading shape and process, of MSCs within 24h were strikingly different between the fibers linked with and without fusion protein. Significant up-regulations in the mRNA expression of adhesion signaling molecules occurred with the fusion protein link, as analyzed by the reverse transcriptase polymerase chain reaction. The expression of a series of osteogenic-related genes at later stages, over 2-3weeks, was significantly improved in the fusion protein-tailored fiber, and the osteogenic protein levels were highly stimulated, as confirmed by immunofluorescence imaging and fluorescence-activated cell sorting analyses. In vivo study in a rat calvarium model confirmed a higher quantity of new bone formation in the fiber linked with fusion protein, and a further increase was noticed when the MSCs were tissue-engineered with the fusion protein-linked fiber. Collectively, these results indicate that FN-OCN fusion protein links via HA mineralization is a facile tool to generate a biointerface with cell-attractive and osteogenic potential, and that the engineered fibrous matrix is a potential bone regenerative scaffold.

Mineralized poly(lactic acid) scaffolds loading vascular endothelial growth factor and the in vivo performance in rat subcutaneous model

The functionalization of degradable polymeric scaffolds with therapeutic molecules such as vascular endothelial growth factor (VEGF) is a key strategy to gain better regenerative ability of damaged bone tissue by stimulating vascularization and tissue perfusion. Here, we combined VEGF with poly(lactic acid) (PLA) porous scaffold, after modifying the PLA surface with calcium phosphate (CaP) mineral. The mineralized PLA scaffold (mPLA) showed more effective loading capacity of VEGF than the PLA without mineralization as well as profiled sustainable release of VEGF for up to a couple of weeks. The VEGF-loaded mPLA scaffold presented significantly improved proliferation of primary endothelial cells for up to 7 days, with respect to the scaffold without the VEGF loading. The performance of the engineered scaffold was assessed after subcutaneous implantation in rats for 4 weeks. Histological results showed favorable tissue compatibility of both the mPLA scaffolds (with and without VEGF loading), as characterized by infiltration of inflammatory cells, formation of fibrous capsule, and ingrowth of fibroblasts into the matrices. Immunohistochemical staining of the von Willebrand Factor revealed significantly improved formation of neo-capillaries in the VEGF-loaded mPLA. Based on this study, the strategy of VEGF loading onto mineralized PLA scaffold is considered beneficial for gaining improved vascularization of the polymeric scaffolds, suggesting potential applications for bone tissue engineering.

Therapeutic foam scaffolds incorporating biopolymer-shelled mesoporous nanospheres with growth factors.

A novel therapeutic scaffolding system of engineered nanocarriers within a foam matrix for the long-term and sequential delivery of growth factors is reported. Mesoporous silica nanospheres were first functionalized to have an enlarged mesopore size (12.2nm) and aminated surface, which was then shelled by a biopolymer, poly(lactic acid) (PLA) or poly(ethylene glycol) (PEG), via electrospraying. The hybrid nanocarrier was subsequently combined with collagen to produce foam scaffolds. Bovine serum albumin (BSA), used as a model protein, was effectively loaded within the enlarged nanospheres. The biopolymer shell substantially prolonged the release period of BSA (2-3weeks from shelled nanospheres vs. within 1week from bare nanospheres), and the release rate was highly dependent on the shell composition (PEG>PLA). Collagen foam scaffolding of the shelled nanocarrier further slowed down the protein release, while enabling the incorporation of a rapidly releasing protein, which is effective for sequential protein delivery. Acidic fibroblast growth factor (aFGF), loaded onto the shelled-nanocarrier scaffolds, was released over a month at a highly sustainable rate, profiling a release pattern similar to that of BSA. The biological activity of the aFGF was evidenced by the significant proliferation of osteoblastic precursor cells in the aFGF-releasing scaffolds. Furthermore, the aFGF-delivering scaffolds implanted in rat subcutaneous tissue for 2weeks showed a substantially enhanced invasion of fibroblasts with a homogeneous population. Taken together, it is concluded that the biopolymer encapsulation of mesoporous nanospheres effectively prolongs the release of growth factors over weeks to a month, providing a nanocarrier platform for a long-term growth factor delivery. Moreover, the foam scaffolding of the nanocarrier system is a potential therapeutic three-dimensional matrix for cell culture and tissue engineering.

Tethering bi-functional protein onto mineralized polymer scaffolds to regulate mesenchymal stem cell behaviors for bone regeneration

Modifying three-dimensional scaffolds with bioactive extracellular matrix (ECM) molecules enhances their potential use in tissue engineering, by providing natural biochemical/physical cues for cell recognition. Here, we engineered the surface of poly(caprolactone) (PCL) scaffolds, first with bone mineral hydroxyapatite (HA), and then with fibronectin-osteocalcin (FN-OCN) bi-functional protein by means of affinity binding between OCN and HA. While FN is expected to enhance initial adhesion of immature precursor cells, OCN is considered to regulate osteogenic differentiation. Quartz crystal microbalance dissipation analysis revealed FN-OCN protein had a more stable and stronger adherence to the HA-mineralized surface than to the native PCL-surface. Initial adhesion and the spreading of rat mesenchymal stem cells were significantly enhanced on the FN-OCN tethered scaffold. Expression of bone-associated genes (osteopontin, bone sialoprotein II and OCN) was significantly higher on the FN-OCN tethered scaffold. Moreover, those proteins were more abundantly found when cultured on the scaffolds with FN-OCN than those without, as confirmed by immunofluorescence cell labeling and fluorescence activated cell sorting analysis. All taken, the tethering of FN-OCN to a HA-mineralized surface is an effective strategy to provide biopolymer scaffolds improved bi-functional capacity for bone tissue engineering, in terms of initial cell adhesion and osteogenic differentiation.

Engineering and application of collagen‐binding fibroblast growth factor 2 for sustained release

The sustained release of growth factors plays a critical role in therapeutic applications because of the instability of these factors in the body. Here, we designed a fibroblast growth factor 2 (FGF2) fused with a collagen-binding domain (rhCBD-FGF2) for collagen-based sustained release of FGF2.The release profile of rhCBD-FGF2 showed sustained release from collagen matrices. Further, rhCBD-FGF2 also stimulated adhesion of the MC3T3-E1 cells to the collagen matrices. In addition, rhCBD-FGF2 increased the cell proliferation activity at 3 and 5 days in the MC3T3-E1 cells attached to the collagen matrices compared to that in the control. Further, rhCBD-FGF2 significantly induced the osteogenic differentiation of MC3T3-E1 cells on collagen matrices by up-regulating the alkaline phosphatase activity at 7 days. These osteogenic differentiation activities were confirmed in gene expression of MC3T3-E1 cell. Taken together, rhCBD-FGF2 could specifically bind with collagen matrices, which indicates important advancements in bone tissue engineering.

Emerging role of vitamin D in colorectal cancer

Colorectal cancer is a common cancer and the fourth leading cause of death in Korea. The incidence and mortality of colorectal cancer varies according to risk factors, such as age, family history, genetic history, food habits, and physical activities. Some studies have focused on the association between vitamin D and colorectal cancer. Today, there is growing evidence that high vitamin D intake and a plasma level of 25(OH)D(3) reduce the incidence of colorectal cancer by modifying cancer angiogenesis, cell apoptosis, differentiation, and proliferation. Taken together, these results suggest that vitamin D supplementation alone, or in combination with anti-cancer agents, might reduce the incidence of colorectal cancer. In this review, we discuss the function and mechanism of vitamin D including the effect of vitamin D on colorectal cancer.

Engineering of a multi-functional extracellular matrix protein for immobilization to bone mineral hydroxyapatite

Purpose of WorkWe have developed a strategy of designing multi-functional extracellular matrix proteins for functionalizing bone tissue engineering scaffolds and other biomedical surfaces to achieve improvements in bone grafting, bone repair and bone regeneration.We developed a novel extracellular matrix protein designed to have a cell adhesive RGD sequence derived from fibronectin and active functional unit of osteocalcin (OC) containing Ca2+-binding sites for immobilization to mineral component of bone, hydroxyapatite (HA). The fusion protein, designated FNRGD/OC, was expressed in Escherichia coli and purified with affinity chromatography using a His-tag. The resultant FNRGD/OC fusion protein preferentially bound to HA, promoted cell adhesive activity, and stimulated differentiation of MC3T3-E1 cell.