An epidermal growth factor derivative with binding affinity for hydroxyapatite and titanium surfaces.

An epidermal growth factor (EGF) derivative with affinity for apatite and titanium surfaces was designed using a peptide moiety derived from salivary statherin, a protein that adheres to hydroxyapatite. Since the active sequence has two phosphoserine residues, the EGF derivative was prepared by organic synthesis, and a 54 residue peptide was successfully prepared using this method. Circular dichroism spectra indicated that the conformation of EGF was not significantly altered by the addition of the affinity peptide sequence and the mitogenic activity was only slightly reduced when compared with the wild-type protein. However, the binding affinity of the modified EGF to hydroxyapatite and titanium was significantly higher than the unmodified EGF. The phosphate groups in the affinity sequence contributed to the affinity of modified EGF to both apatite and titanium. The modified EGF significantly enhanced the growth of cells on hydroxyapatite and titanium. It was also demonstrated that the bound EGF enhanced the signal transduction for longer periods than unbound EGF. In conclusion, the modified EGF had significantly higher binding affinity for apatite and titanium than soluble EGF, and the bound EGF significantly enhanced cell growth by long-lasting activation of intracellular signal transduction.

Recombinant hBMP4 incorporated with non-canonical amino acid for binding to hydroxyapatite.

A novel growth factor containing non-canonical amino acids was designed and synthesized to enhance the binding to hydroxyapatite (HA). The designed protein was human bone morphogenetic protein 4 (hBMP4) incorporating diphosporylated serines (pSpS) that was found in salivary protein statherin and was reported to be responsible for binding to HA. Recombinant hBMP4 and a short peptide sequences containing pSpS were ligated by enzymatice reaction of sortase A, which exchanges the terminal amino acids of two polypeptides. Resulting hBMP4 containing pSpS (hBMP4-pSpS) bound HA more efficiently than hBMP-4 tagged with canonical serines (hBMP4-SS). The HA-bound hBMP-4-pSpS exhibited osteogenesis inducing activity to multipotential mesenchyme cells (C3H10T1/2) as evidenced by increased expression of osteogenic markers, which was not seen by hBMP4-SS. This novel protein with non-canonical serines will be applicable to bone regeneration materials in combination with HA.

Visible light-induced crosslinkable gelatin.

A novel visible light-crosslinkable porcine gelatin was prepared for gelation and micropatterning. The preparation employed a photo-oxidation-induced crosslinking mechanism. First, furfuryl groups were incorporated into the gelatin. Second, the modified gelatin was mixed in water with Rose Bengal, which is a visible light sensitizer. Irradiation by visible light solidified the aqueous solution. In addition, when the solution was cast on a plate, dried and photo-irradiated in the presence of a photomask a micropattern was formed that matched the micropattern on the photomask. The gelatin-immobilized regions enhanced cell adhesion. It was also confirmed that the gelatin incorporating furfuryl and Rose Bengal have no significant toxicity. The photo-crosslinkable gelatin was employed as a direct pulp capping material in the dental field. Considering these results, this system could be useful as a new type of visible light-induced crosslinkable biosealant.

A photoimmobilizable sulfobetaine-based polymer for a nonbiofouling surface.

A novel photoreactive polymer containing sulfobetaine polar groups was prepared by copolymerization of two kinds of methacrylic acids with sulfobetaine and azidoaniline. The polymer was photoimmobilized on polyester and polystyrene surfaces. Its effects on surface modification were investigated from its interactions with water, proteins and cells. Polymer immobilization altered both of the plain surfaces to becoming hydrophilic in a similar range of static contact angles (12.5±1.6° on polyester and 14.7±2.2° on polystyrene). This suggests that the surfaces were covered with sulfobetaine polar groups. Micropattern immobilization was carried out on both polymers using a photomask. The formed pattern was identical to the photomask, showing that the polymer was formed in response to ultraviolet irradiation. Measurements using atomic force microscopy showed that the polymer was formed at a thickness of 550nm, demonstrating that the polymer was cross-linked with itself and with the substrate molecules. Measurements using time-of-flight secondary ion mass spectrometry detected an abundance of sulfur-containing ions in the patterned polymer, confirming that sulfobetaine had been immobilized. Protein adsorption and mammalian cell adhesiveness were reduced markedly on the immobilized regions. The reduction of cell adhesiveness was concentration-dependent for the immobilized polymer on polyester surfaces. In conclusion, a novel sulfobetaine-containing polymer was immobilized photoreactively on conventional polymer surfaces and significantly reduced interactions with proteins and mammalian cells.

Surface coating with a thermoresponsive copolymer for the culture and non-enzymatic recovery of mouse embryonic stem cells.

A thermoresponsive substrate based on a triblock copolymer, poly(N-isopropylacrylamide)-block-poly[(R)-3-hydroxybutyrate]-block-poly(N-isopropylacrylamide) (PNIPAAm-PHB-PNIPAAm), co-coated with gelatin, was developed for the culture and non-enzymatic recovery of mouse embryonic stem cells. After culture, the cells could be detached by cooling at 4 degrees C for 20 min without trypsin digestion. The embryonic stem cells remained undifferentiated after culture on the gelatin/copolymer-coated surfaces, similar to standard culture techniques. Overall, the triblock copolymer coating was superior to the PNIPAAm homopolymer coating in terms of supporting better cell growth, being more stable, presenting a more homogeneous surface coating, and maintaining pluripotency of the embryonic stem cells.

A chimeric epidermal growth factor with fibrin affinity promotes repair of injured keratinocyte sheets.

The aim of the present study is to create a novel chimeric protein of epidermal growth factor (EGF) with fibrin affinity and demonstrate its potential for repairing injured tissues by immobilization to fibrin. The chimeric protein (FBD-EGF) was produced by the fusion of the fibronectin fibrin-binding domain (FBD) to EGF. It showed dose-dependent binding to fibrin and its binding was stable for at least 7days, while native EGF showed little affinity. FBD-EGF promoted the growth of fibroblasts and keratinocytes in the fibrin-bound state as well as in the soluble state. Its activity was further studied in a keratinocyte culture system in which fibrin was exposed upon injury of cell sheets. Fibrin-bound FBD-EGF promoted growth of the sheets over the injured area at a significantly faster rate (approximately eightfold) than native EGF (p<0.01). Wounds 2mm wide were closed in 7-9days. This repair process was inhibited by anti-EGF. Keratinocytes proliferated more extensively in the leading edges of sheets contacting fibrin with FBD-EGF, approximately 1.7-fold more than in the adjacent regions. These results imply that the stable binding of chimeric EGF to fibrin is effective for the repair of injured keratinocyte sheets, suggesting a potential use in tissue engineering.

Surface modification of plastic, glass and titanium by photoimmobilization of polyethylene glycol for antibiofouling.

Photoreactive poly(ethylene glycol) (PEG) was prepared and the polymer was photoimmobilized on organic, inorganic and metal surfaces to reduce their interaction with proteins and cells. The photoreactive PEG was synthesized by co-polymerization of methacrylate-PEG and acryloyl 4-azidobenzene. Surface modification was carried in the presence and the absence of a micropatterned photomask. It was then straightforward to confirm the immobilization using the micropatterning. Using the micropatterning method, immobilization of the photoreactive PEG on plastic (Thermanox), glass and titanium was confirmed by time-of-flight secondary ion mass spectroscopy and atomic force microscopy observations. The contact angle on an unpatterned surface was measured. Although the original surfaces have different contact angles, the contact angle on PEG-immobilized surfaces was the same on all surfaces. This result demonstrated that the surface was completely covered with PEG by the photoimmobilization. To assess non-specific protein adsorption on the micropatterned surface, horseradish peroxidase (HRP)-conjugated proteins were adsorbed. Reduced protein adsorption was confirmed by vanishingly small staining of HRP substrates on the immobilized regions. COS-7 cells were cultured on the micropatterned surface. The cells did not adhere to the PEG-coated regions. In conclusion, photoreactive PEG was immobilized on various surfaces and tended to reduce interactions with proteins and cells.

Modification of the titan surface with photoreactive gelatin to regulate cell attachment.

Titan (TiO2) was modified with photoreactive gelatin in order to regulate the attachment of cells. Photoreactive gelatin, which was synthesized by the coupling reaction of gelatin with N-(4-azidobenzoyloxy) succinimide, was immobilized onto the n-octadecyltrimethoxysilane (ODS)-TiO2 or TiO2 surface by ultraviolet irradiation both in the absence and presence of a photo mask. In the absence of a photo mask, the modified titan surface was analyzed by measuring water contact angles and X-ray photoelectron spectroscopy (XPS). The result showed that ODS hydrophobilized the titan surface, and that the immobilization of gelatin affected the surface's hydrophilicity. XPS shows that titan was covered with organic material, including ODS and gelatin. With the photo mask in place, micropatterning of the gelatin was performed. This pattern was confirmed by optical microscopy and time-of-flight secondary ion-mass spectroscopy (TOF-SIMS). Monkey COS-7 epithelial cells were cultured on the unpattern- and pattern-immobilized plate. A significantly higher degree of cell attachment was found on the photoreactive gelatin-immobilized regions than on those that were not immobilized. It was concluded that the cellular pattern on titan was regulated by immobilized photoreactive gelatin.

Functional analysis of chick ONT1 reveals distinguishable activities among olfactomedin-related signaling factors.

The Olfactomedin family is a relatively new class of extracellular proteins. Two family members have been shown to play roles in the early development of ectodermal tissues: Noelin enhances neural crest generation in chick and Tiarin promotes dorsal neural specification in Xenopus. In this study, we introduce a novel member of the Olfactomedin family, ONT1. In the early chick embryo, ONT1 expression first appears at Hensen's node and subsequently in the axial and paraxial mesoderm. When the neural tube closes, strong expression of ONT1 is transiently found in the roof plate region from the rostral midbrain to the hindbrain. Overexpression of ONT1 in these regions prolongs the generation of neural crest cells in a manner similar to that of Noelin. Interestingly, ONT1 and Noelin have opposing effects on the expression of the migrating neural crest marker HNK-1 in the chick: they, respectively, cause suppression and ectopic induction of this marker. Differential activities among Olfactomedin-related factors are further examined in Xenopus. Microinjection of ONT1 mRNA into the Xenopus embryo expands the expression domain of the neural crest marker FoxD3 at the neurula stage whereas overexpression of Tiarin or Noelin suppresses FoxD3. ONT1 exhibits no dorsalizing effects on the Xenopus neural tube, which contrasts with the strong dorsalizing activity seen for Tiarin. Thus, distinct Olfactomedin-related factors evoke qualitatively different phenotypes even in the same experimental systems, suggesting that Olfactomedin family uses multiple response systems to mediate its signals in embryogenesis.

Gene disruption/knock-in analysis of mONT3: vector construction by employing both in vivo and in vitro recombinations.

We report the isolation, spatial/temporal expression and gene disruption phenotype of the mouse ONT3 (mONT3) gene, which encodes a novel secreted signaling protein belonging to the Olfactomedin/Noelin/Tiarin family. During early embryogenesis, mONT3 is detected in the proximal region of the allantois on embryonic day (E) 7.25, in the lateral plate mesoderm on E 8.0 and in the CNS and heart on E 8.5. The homozygous mutant is born normal and fertile. For the expression pattern and loss-of-function analyses, we have successfully generated the LacZ-knock-in targeting vector directly from BACs carrying mouse genomic fragments by combining in vivo and in vitro recombination techniques. This approach enables rapid and reproducible construction of the fully functional vectors within two weeks without the use of restriction enzyme digestion and ligation, or the use of PCR-amplification of large genomic fragments. In addition, this method is applicable to rapid generation of transgenic vectors, demonstrating its versatility in reverse genetic studies.

Dorsalization of the neural tube by Xenopus tiarin, a novel patterning factor secreted by the flanking nonneural head ectoderm.

We have isolated a novel secreted dorsalizing factor of the neural tube, Xenopus Tiarin, which belongs to the olfactomedin-related family. Tiarin expression starts at the late gastrula stage in the nonneural ectoderm adjacent to the anterior neural plate. Overexpression of Tiarin in the embryo causes expansion of dorsal neural markers and suppression of ventral markers. In the eye-forming field, Tiarin overexpression induces the retinal markers and represses optic stalk markers. Tiarin directly dorsalizes neural tissues in the absence of mesodermal tissues and antagonizes the ventralizing activity of Sonic hedghog (Shh). Unlike BMP4, another dorsalizing factor, Tiarin does not display antineuralizing activity on the ectoderm or mesoderm-ventralizing activity. These findings show that Tiarin is a novel patterning signal candidate acting in the specification of the dorsal neural tube.