The stability of bFGF against thermal denaturation

Heparan Sulfate-Collagen Surface Multilayers Support Serum-Free Microcarrier Culture of Mesenchymal Stem Cells

The increasing cost of high-volume cultures and dependence on serum and growth factor supplementation limit the affordability of mesenchymal stromal cell (MSC) therapies. This has spurred interest in developing strategies that support adherent cell expansion while reducing raw material costs. Culture surfaces coated with sulfated glycosaminoglycans (GAGs), specifically heparan sulfate (HS), are an alternative to prolong growth factor retention in cell cultures. Unlike heparin, recombinant HS (rHS) offers strong binding affinity for multiple growth factors and extracellular matrix components, such as collagen I, without undesirable anticoagulant effects or xenobiotic health risks. The potential of rHS as a factor reservoir in MSC cultures remains underexplored. This study investigated the impact of rHS on the growth and anti-inflammatory properties of undifferentiated bone marrow MSCs in both planar and microcarrier-based cultures. It was hypothesized that rHS would enable MSC growth with minimal growth factor supplementation in a sulfation level-dependent manner. Cell culture surfaces were assembled via the layer-by-layer (LbL) method, combining alternating collagen I (COL) and rHS. These bilayers support cell adhesion and enable the incorporation of distinct sulfation levels on the culture surface. Examination of pro-mitogenic FGF and immunostimulatory IFN-γ release dynamics confirmed prolonged availability and sulfate level dependencies. Sulfated surfaces supported cell growth in low serum (2% FBS) and serum-free (SF) media at levels equivalent to standard culture conditions. Cell growth on rHS-coated surfaces in SF was comparable to that on heparin-coated surfaces and commercial surface-coated microcarriers in low serum. These growth benefits were observed in both planar and microcarrier (μCs) cultures. Additionally, rHS surfaces reduced β-galactosidase expression relative to uncoated surfaces, delaying cell senescence. Multivariate analysis of cytokines in conditioned media indicated that rHS-containing surfaces enhanced cytokine levels relative to uncoated surfaces during IFN-γ stimulation and correlated with decreased pro-inflammatory macrophage activity. Overall, utilizing highly sulfated rHS with COL reduces the need for exogenous growth factors and effectively supports MSC growth and anti-inflammatory potency on planar and microcarrier surfaces under minimal factor supplementation.

Fibroblast growth factor-2 bound to specific dermal fibroblast-derived extracellular vesicles is protected from degradation

Fibroblast growth factor-2 (FGF2) has multiple roles in cutaneous wound healing but its natural low stability prevents the development of its use in skin repair therapies. Here we show that FGF2 binds the outer surface of dermal fibroblast (DF)-derived extracellular vesicles (EVs) and this association protects FGF2 from fast degradation. EVs isolated from DF cultured in the presence of FGF2 harbor FGF2 on their surface and FGF2 can bind purified EVs in absence of cells. Remarkably, FGF2 binding to EVs is restricted to a specific subpopulation of EVs, which do not express CD63 and CD81 markers. Treatment of DF with FGF2-EVs activated ERK and STAT signaling pathways and increased cell proliferation and migration. Local injection of FGF2-EVs improved wound healing in mice. We further demonstrated that binding to EVs protects FGF2 from both thermal and proteolytic degradation, thus maintaining FGF2 function. This suggests that EVs protect soluble factors from degradation and increase their stability and half-life. These results reveal a novel aspect of EV function and suggest EVs as a potential tool for delivering FGF2 in skin healing therapies.

Heparinized Gelatin-Based Hydrogels for Differentiation of Induced Pluripotent Stem Cells

Chemically defined hydrogels are increasingly utilized to define the effects of extracellular matrix (ECM) components on cellular fate determination of human embryonic and induced pluripotent stem cell (hESC and hiPSCs). In particular, hydrogels cross-linked by orthogonal click chemistry, including thiol-norbornene photopolymerization and inverse electron demand Diels–Alder (iEDDA) reactions, are explored for 3D culture of hESC/hiPSCs owing to the specificity, efficiency, cytocompatibility, and modularity of the cross-linking reactions. In this work, we exploited the modularity of thiol-norbornene photopolymerization to create a biomimetic hydrogel platform for 3D culture and differentiation of hiPSCs. A cell-adhesive, protease-labile, and cross-linkable gelatin derivative, gelatin-norbornene (GelNB), was used as the backbone polymer for constructing hiPSC-laden biomimetic hydrogels. GelNB was further heparinized via the iEDDA click reaction using tetrazine-modified heparin (HepTz), creating GelNB-Hep. GelNB or GelNB-Hep was modularly cross-linked with either inert macromer poly(ethylene glycol)-tetra-thiol (PEG4SH) or another bioactive macromer-thiolated hyaluronic acid (THA). The formulations of these hydrogels were modularly tuned to afford biomimetic matrices with similar elastic moduli but varying bioactive components, enabling the understanding of each bioactive component on supporting hiPSC growth and ectodermal, mesodermal, and endodermal fate commitment under identical soluble differentiation cues.

Induction of Cartilage Regeneration by Nanoparticles Loaded with Dentin Matrix Extracted Proteins

Due to the limited self-repair capacity of articular cartilage, tissue engineering has good application prospects for cartilage regeneration. Dentin contains several key growth factors involved in cartilage regeneration. However, it remains unknown whether dentin matrix extracted proteins (DMEP) can be utilized as a complex growth-factor mixture to induce cartilage regeneration. In this work, we extracted DMEP from human dentin and improved the content and activity of chondrogenic-related growth factors in DMEP by alkaline conditioning. Afterwards, mesoporous silica nanoparticles (MSNs) with particular physical and chemical properties were composed to selectively load and sustain the release of proteins in DMEP. MSN-DMEP promoted chondrogenic differentiation of rat bone marrow-derived mesenchymal stem cells with fewer growth factors than exogenously added transforming growth factor-β1 (TGF-β1). Therefore, MSN-DMEP may serve as a promising candidate for cartilage regeneration as an alternative to expensive synthetic growth factors.

New 1,3,4-oxadiazoles linked with the 1,2,3-triazole moiety as antiproliferative agents targeting the EGFR tyrosine kinase

A series of 1,3,4-oxadiazole-1,2,3-triazole hybrids bearing different pharmacophoric moieties has been designed and synthesized. Their antiproliferative activity was evaluated against four human cancer cell lines (Panc-1, MCF-7, HT-29, and A-549) using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The preliminary activity test displayed that the most active compounds, 6d, 6e, and 8a-e, suppressed cancer cell growth (GI₅₀  = 0.23-2.00 µM) comparably to erlotinib (GI₅₀  = 0.06 µM). Compounds 6d, 6e, and 8a-e inhibited the epidermal growth factor receptor tyrosine kinase (EGFR-TK) at IC₅₀  = 0.11-0.73 µM, compared to erlotinib (IC₅₀  = 0.08 ± 0.04 µM). The apoptotic mechanism revealed that the most active hybrid 8d induced expression levels of caspase-3, caspase-9, and cytochrome-c in the human cancer cell line Panc-1 by 7.80-, 19.30-, and 13-fold higher than doxorubicin. Also, 8d increased the Bax level by 40-fold than doxorubicin, along with decreasing Bcl-2 levels by 6.3-fold. Cell cycle analysis after treatment of Panc-1 cells with hybrid 8d revealed a high proportion of cell accumulation (41.53%) in the pre-G1 phase, indicating cell cycle arrest at the G1 transition. Computational docking of the 8d and 8e hybrids with the EGFR binding site revealed their ability to bind with EGFR similar to erlotinib. Finally, in silico absorption, distribution, metabolism, and excretion/pharmacokinetic studies for the most active hybrids are discussed.

Stabilisation of Recombinant Human Basic Fibroblast Growth Factor (FGF-2) against Stressors Encountered in Medicinal Product Processing and Evaluation

Basic fibroblast growth factor (FGF-2) is a highly labile protein with strong potential for tissue engineering. The aim of this study was to develop FGF-2 formulations that are stable against physical stressors encountered in pharmaceutical processing and evaluation. Pharmaceutical excipients, alone or in combination, were added to aqueous FGF-2 (770 ng/mL) solution and the stability of the resulting solutions on storage at 4–37 °C was evaluated. Stability of the solutions to repeated freeze-thaw cycles and lyophilisation was also evaluated, as well as the stability of the lyophilised stabilised protein to storage at −4, 4 and 18 °C for up to 12 months. In all of these experiments FGF-2 was quantified by ELISA assay. The as-received FGF-2, when dissolved in water, was highly unstable, retaining only 50% of baseline protein content after 30 min at 37 °C or 1 h at 25 °C. By contrast, FGF-2 solutions prepared with 0.5% w/v methylcellulose (MC) and 20 mM alanine (formulation F5) or with 0.5% w/v MC and 1 mg/mL human serum albumin (HSA) (formulation F6) were highly stable, having residual FGF-2 content comparable to baseline levels even after 2 h at 37 °C and 5 h at 25 °C. F5 and F6 were also highly stable to repeated freeze-thaw cycles, with >99% of FGF-2 load remaining after the third cycle. In addition, F5 and F6 were stable to lyophilisation, and the lyophilised products could be stored at −4, 4 or 18 °C for at least 12 months, with less than 1% loss in mean FGF-2 content. Thus, FGF-2 solution is effectively stabilised against both thermal and processing stressors in the presence of MC and alanine (F5), or MC and HSA (F6). The resultant FGF-2 solutions may be applied as medicinal products or further processed into more advanced medicinal products, e.g., scaffolds, for wound healing and tissue regeneration.

Externally triggered release of growth factors - A tissue regeneration approach

Tissue regeneration aims to achieve functional restoration following injury by creating an environment to enable the body to self-repair. Strategies for regeneration rely on the introduction of biomaterial scaffolding, cells and bioactive molecules into the body, at or near the injury site. Of these bioactive molecules, growth factors (GFs) play a pivotal role in directing regenerative pathways for many cell populations. However, the therapeutic use of GFs has been limited by the complexity of biological injury and repair, and the properties of the GFs themselves, including their short half-life, poor tissue penetration, and off-target side effects. Externally triggered delivery systems have the potential to facilitate the delivery of GFs into the target tissues with considerations of the timing, sequence, amount, and location of GF presentation. This review briefly discusses the challenges facing the therapeutic use of GFs, then, we discuss approaches to externally trigger GF release from delivery systems categorised by stimulation type; ultrasound, temperature, light, magnetic fields and electric fields. Overall, while the use of GFs for tissue regeneration is still in its infancy, externally controlled GF delivery technologies have the potential to achieve robust and effective solutions to present GFs to injured tissues. Future technological developments must occur in conjunction with a comprehensive understanding of the biology at the injury site to ensure translation of promising technologies into real world benefit.

Heparin-conjugated collagen as a potent growth factor-localizing and stabilizing scaffold for regenerative medicine

Introduction

Growth factors are crucial bioactive molecules in vitro and in vivo. Among them, basic fibroblast growth factor (bFGF) has been used widely for various applications such as cell culture and regenerative medicine. However, bFGF has extremely poor stability in aqueous solution; thus, it is difficult to maintain its high local concentration. Heparin-conjugated materials have been studied recently as promising scaffold-immobilizing growth factors for biological and medical applications. The previous studies have focused on the local concentration maintenance and sustained release of the growth factors from the scaffold.

Methods

In this paper, we focused on the biological stability of bFGF immobilized on the heparin-conjugated collagen (hep-col) scaffold. The stability of the immobilized bFGF was quantitatively evaluated at physiological temperature (37 °C) using cell culture and ELISA.

Results

The immobilized bFGF had twice higher stability than the bFGF solution. Furthermore, the hep-col scaffold was able to immobilize not only bFGF but also other growth factors (i.e., vascular endothelial growth factor and hepatocyte growth factor) at high efficiency.

Conclusions

The hep-col scaffold can localize several kinds of growth factors as well as stabilize bFGF under physiological temperature and is a promising potent scaffold for regenerative medicine.

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Heparin-conjugated collagen scaffold immobilized bFGF, VEGF, and HGF with a high efficiency of 80–90% even at 100 ng/mL.

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Cell proliferation of HUVECs was promoted depending on the bFGF amount on the scaffold, and slowed by pre-incubation at 37 °C.

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Growth factor-immobilization on the scaffold stabilized bFGF and maintained its bioactivity longer than bFGF solution.

Fibroblast Growth Factor 2-A Review of Stabilisation Approaches for Clinical Applications

Basic fibroblast growth factor (FGF)-2 has been shown to regulate many cellular functions including cell proliferation, migration, and differentiation, as well as angiogenesis in a variety of tissues, including skin, blood vessel, muscle, adipose, tendon/ligament, cartilage, bone, tooth, and nerve. These multiple functions make FGF-2 an attractive component for wound healing and tissue engineering constructs; however, the stability of FGF-2 is widely accepted to be a major concern for the development of useful medicinal products. Many approaches have been reported in the literature for preserving the biological activity of FGF-2 in aqueous solutions. Most of these efforts were directed at sustaining FGF-2 activity for cell culture research, with a smaller number of studies seeking to develop sustained release formulations of FGF-2 for tissue engineering applications. The stabilisation approaches may be classified into the broad classes of ionic interaction modification with excipients, chemical modification, and physical adsorption and encapsulation with carrier materials. This review discusses the underlying causes of FGF-2 instability and provides an overview of the approaches reported in the literature for stabilising FGF-2 that may be relevant for clinical applications. Although efforts have been made to stabilise FGF-2 for both in vitro and in vivo applications with varying degrees of success, the lack of comprehensive published stability data for the final FGF-2 products represents a substantial gap in the current knowledge, which has to be addressed before viable products for wider tissue engineering applications can be developed to meet regulatory authorisation.

Cytotoxic Conjugates of Fibroblast Growth Factor 2 (FGF2) with Monomethyl Auristatin E for Effective Killing of Cells Expressing FGF Receptors

Antibody-drug conjugates (ADCs) are a new class of anticancer therapeutics that combine the selectivity of targeted treatment, ensured by monoclonal antibodies, with the potency of the cytotoxic agent. Here, we applied an analogous approach, but instead of an antibody, we used fibroblast growth factor 2 (FGF2). FGF2 is a natural ligand of fibroblast growth factor receptor 1 (FGFR1), a cell-surface receptor reported to be overexpressed in several types of tumors. We developed and characterized FGF2 conjugates containing a defined number of molecules of highly cytotoxic drug monomethyl auristatin E (MMAE). These conjugates effectively targeted FGFR1-expressing cells, were internalized upon FGFR1-mediated endocytosis, and, in consequence, revealed high cytotoxicity, which was clearly related to the FGFR1 expression level. Among the conjugates tested, the most potent was that bearing three MMAE molecules, showing that the cytotoxicity of protein-drug conjugates in vitro is directly dependent on drug loading.

Influence of polymerization properties of 4-META/MMA-based resin on the activity of fibroblast growth factor-2

Dental adhesive resins based on 4-methacryloxyethyl trimellitate anhydride (4-META)/methyl methacrylate (MMA) have been utilized for root-end filling and the bonding of fractured roots. To increase the success rate of these treatments, it would be beneficial to promote the healing of surrounding tissue by applying growth factors. In this study, the influences of the polymerization properties of 4-META/MMA-based resins on the activity of fibroblast growth factor-2 (FGF-2) were evaluated in vitro. The temperature increase caused by the heat generation during polymerization of the 4-META/MMA-based resin was insufficient to change the structure and function of FGF-2. Unpolymerized monomers released from the cured 4-META/MMA-based resin had no negative influences on the ability of FGF-2 to promote the proliferation of osteoblast-like cells. These findings suggest that it is possible to use FGF-2 in combination with 4-META/MMA-based resins.

Affinity Selection of FGF2-Binding Heparan Sulfates for Ex Vivo Expansion of Human Mesenchymal Stem Cells

The future of human mesenchymal stem cells (hMSCs) as a successful cell therapy relies on bioprocessing strategies to improve the scalability of these cells without compromising their therapeutic ability. The culture-expansion of hMSCs can be enhanced by supplementation with growth factors, particularly fibroblast growth factor 2 (FGF2). The biological activity of FGF2 is controlled through interactions with heparan sulfate (HS) that facilitates ligand-receptor complex formation. We previously reported on an FGF2-interacting HS variant (termed HS2) isolated from embryonic tissue by anionic exchange chromatography that increased the proliferation and potency of hMSCs. Here, we detail the isolation of an FGF2 affinity-purified HS variant (HS8) using a scalable platform technology previously employed to generate HS variants with increased affinity for BMP-2 or VEGF₁₆₅ . This process used a peptide sequence derived from the heparin-binding domain of FGF2 as a substrate to affinity-isolate HS8 from a commercially available source of porcine mucosal HS. Our data show that HS8 binds to FGF2 with higher affinity than to FGF1, FGF7, BMP2, PDGF-BB, or VEGF₁₆₅ . Also, HS8 protects FGF2 from thermal destabilization and increases FGF signaling and hMSC proliferation through FGF receptor 1. Long-term supplementation of cultures with HS8 increased both hMSC numbers and their colony-forming efficiency without adversely affecting the expression of hMSC-related cell surface antigens. This strategy further exemplifies the utility of affinity-purifying HS variants against particular ligands important to the stem cell microenvironment and advocates for their addition as adjuvants for the culture-expansion of hMSCs destined for cellular therapy. J. Cell. Physiol. 232: 566-575, 2017. © 2016 Wiley Periodicals, Inc.

Effect of locally applied bFGF on implant stability: biomechanical evaluation of 2 different implant surfaces in rabbits

OBJECTIVES

The aim of this study was to evaluate the implant stability with the addition of local application of basic fibroblast growth factor (bFGF) during the osseointegration of 2 different dental implant surfaces using rabbit tibia model.

MATERIALS AND METHODS

Fifty-six dental implants, 28 of hydrophilic surface (SLActive) and 28 of hydrophobic surface (OsseoSpeed), were placed in 14 mature New Zealand rabbits. The rabbits each received both SLActive and OsseoSpeed implants per tibia, and bFGF was applied locally on 1 randomly selected tibia. Half of the subjects were killed at the fourth week of healing period, and the other half were killed at the twelfth week. Stabilization was assessed using resonance frequency analysis (RFA) and removal torque value (RTV).

RESULTS

The local application of bFGF was found to enhance osseointegration, especially at the fourth week of healing period after application (P = 0.046). RFAs and RTVs were found to be higher in bFGF-treated implant with hydrophilic surfaces when compared with both bFGF-treated hydrophobic implants and nontreated hydrophilic controls.

CONCLUSION

Local application of bFGF seems to increase the stabilization values in implants with hydrophilic surfaces and those with hydrophobic surfaces.

Cell-Demanded VEGF Release via Nanocapsules Elicits Different Receptor Activation Dynamics and Enhanced Angiogenesis

Although the delivery of vascular endothelial growth factor (VEGF) with extended release profiles has consistently shown beneficial therapeutic effects compared with bolus delivery, [Martino, M. M., F. Tortelli, M. Mochizuki, S. Traub, D. Ben-David, G. A. Kuhn, R. Muller, E. Livne, S. A. Eming, and J. A. Hubbell. Sci. Transl. Med. 3(100):100ra189, 2011; Martino, M. M., P. S. Briquez, A. Ranga, M. P. Lutolf, and J. A. Hubbell. Proc. Natl. Acad. Sci. USA. 110(12):4563-4568, 2013; Amiram, M., K. M. Luginbuhl, X. Li, M. N. Feinglos, and A. Chilkoti. Proc. Natl. Acad. Sci. USA. 110(8):2792-2797, 2013] it remains unclear if the reason is solely due to the physical availability and the reduced degradation of the protein. Here we studied the activation of VEGF receptor 2 (VR-2) by sustained released VEGF compared with bolus delivered VEGF to unveil that sustained delivery system alters the dynamics of receptor activation and affects the actions of cells between sprouting and proliferation. We utilized a protein nanocapsule delivery strategy that releases VEGF as mediated by extracellular proteases. These protein nanocapsules were synthesized through an aqueous assembly of a nanogel-peptide shell around the protein, leading to one to two proteins encapsulated per nanocapsule. Receptor activation studies revealed differential dynamics of receptor activation for slowly released VEGF compared with bolus delivered VEGF. As expected sustained released VEGF via nanocapsules resulted in enhanced vascular sprouting in vitro and in vivo. These studies demonstrate the physical presentation of VEGF, in this case of a slow release with time, can affect its molecular mechanism of actions and cause alterations in cellular responses and therapeutic outcomes.

Fibroblast growth factor 2 dimer with superagonist in vitro activity improves granulation tissue formation during wound healing

Site-specific chemical dimerization of fibroblast growth factor 2 (FGF2) with the optimal linker length resulted in a FGF2 homodimer with improved granulation tissue formation and blood vessel formation at exceptionally low concentrations. Homodimers of FGF2 were synthesized through site-specific linkages to both ends of different molecular weight poly(ethylene glycols) (PEGs). The optimal linker length was determined by screening dimer-induced metabolic activity of human dermal fibroblasts and found to be that closest to the inter-cysteine distance, 70 Å, corresponding to 2 kDa PEG. A straightforward analysis of the kinetics of second ligand binding as a function of tether length showed that, as the polymerization index (the number of monomer repeat units in the polymer, N) of the tether decreases, the mean time for second ligand capture decreases as ∼N(3/2), leading to an enhancement of the number of doubly bound ligands in steady-state for a given (tethered) ligand concentration. FGF2-PEG2k-FGF2 induced greater fibroblast metabolic activity than FGF2 alone, all other dimers, and all monoconjugates, at each concentration tested, with the greatest difference observed at low (0.1 ng/mL) concentration. FGF2-PEG2k-FGF2 further exhibited superior activity compared to FGF2 for both metabolic activity and migration in human umbilical vein endothelial cells, as well as improved angiogenesis in a coculture model in vitro. Efficacy in an in vivo wound healing model was assessed in diabetic mice. FGF2-PEG2k-FGF2 increased granulation tissue and blood vessel density in the wound bed compared to FGF2. The results suggest that this rationally designed construct may be useful for improving the fibroblast matrix formation and angiogenesis in chronic wound healing.

Synthesis and biological evaluation of a new class of quinazolinoneazoles as potential antimicrobial agents and their interactions with calf thymus DNA and human serum albumin

A series of quinazolinone azoles were synthesized and screened for their antimicrobial activities, and further studies of their binding behaviors with calf thymus DNA and human serum albumin were investigated.

Effects of heparin and cholesterol sulfate on the activity and stability of human matrix metalloproteinase 7

Sulfated glycosaminoglycans and sulfated lipids are involved in the biological functions of human matrix metalloproteinase 7 (MMP-7). In this study, the effects of heparin and cholesterol sulfate (CS) on the activity and stability of MMP-7 in the hydrolysis of a synthetic substrate, (7-methoxycoumarin-4-yl)acetyl-l-Pro-l-Leu-Gly-l-Leu-[N(3)-(2,4-dinitrophenyl)-l-2,3-diaminopropionyl]-l-Ala-l-Arg-NH2, were examined. Heparin increased activity by decreasing Km, and the Km values for 0 and 50 μM heparin were 57 ± 8 and 19 ± 5 μM, respectively. CS decreased activity in a non-competitive inhibitory manner with a Ki value of 11 ± 3 μM. In thermal incubation at 50-70 °C, heparin increased relative activity (the ratio of kcat/Km of MMP-7 with incubation to that without it), while CS decreased relative activity. These results indicate that heparin increases the activity and stability of MMP-7, while CS decreases them.

The effects of excipients on protein aggregation during agitation: an interfacial shear rheology study

We investigated the effects of excipients in solutions of keratinocyte growth factor 2 (KGF-2) on protein aggregation during agitation as well as on interfacial shear rheology at the air-water interface. Samples were incubated with or without agitation, and in the presence or absence of the excipients heparin, sucrose, or polysorbate 80 (PS80). The effect of excipients on the extent of protein aggregation was determined by UV-visible spectroscopy and micro-flow imaging. Interfacial shear rheology was used to detect the gelation time and strength of protein gels at the air-water interface. During incubation, protein particles of size ≥1 μm and insoluble aggregates formed faster for KGF-2 solutions subjected to agitation. Addition of either heparin or sucrose promoted protein aggregation during agitation. In contrast, PS80 substantially inhibited agitation-induced KGF-2 aggregation but facilitated protein particulate formation in quiescent solutions. The combination of PS80 and heparin or sucrose completely prevented protein aggregation during both nonagitated and agitated incubations. Interfacial rheological measurements showed that KGF-2 in buffer alone formed an interfacial gel within a few minutes. In the presence of heparin, KGF-2 interfacial gels formed too quickly for gelation time to be determined. KGF-2 formed gels in about 10 min in the presence of sucrose. The presence of PS80 in the formulation inhibited gelation of KGF-2. Furthermore, the interfacial gels formed by the protein in the absence of PS80 were reversible when PS80 was added to the samples after gelation. Therefore, there is a correspondence between formulations that exhibited interfacial gelation and formulations that exhibited agitation-induced aggregation.

Following protein-glycosaminoglycan polysaccharide interactions with differential scanning fluorimetry

Studies of the structural changes invoked in proteins by the binding of the glycosaminoglycan (GAG) polysaccharide portion of proteoglycans are of increasing importance to research in a wide range of fields, from biochemistry and molecular biology to biotechnology and medicine. One important aspect is the degree of stabilisation or destabilisation induced in a protein by the binding of these anionic materials, and this can affect enzyme activity, the stability of complexes, folding and the formation of aggregates, including those in neurodegenerative processes. A simple method, able to determine the effect of interactions with GAG polysaccharides on protein stability is described, based on the propensity of a fluorescent dye-Sypro™ Orange-to present differentiable fluorescence emission spectra following contact with exposed core amino acid residues. The method requires only commonly available and inexpensive equipment and is suitable for a multi-well format, allowing multiple readings to be made simultaneously.

Gelatin microspheres encapsulated with a nonpeptide angiogenic agent, ginsenoside Rg1, for intramyocardial injection in a rat model with infarcted myocardium

Angiogenic therapies may need to select a stable agent to be delivered. In the study, a nonpeptide angiogenic agent, ginsenoside Rg(1) (Rg(1)), was encapsulated in the gelatin microspheres (MSs) crosslinked with genipin and intramuscularly injected into a rat model with infarcted myocardium. bFGF was used as a control. After swelling in an aqueous environment, the MSs without crosslinking became collapsed and stuck together. For those crosslinked, the swollen MSs appeared to be more stable with an increasing the degree of crosslinking. After it was released from MSs in vitro, the remaining activity of bFGF on HUVEC proliferation reduced significantly, while that of Rg(1) remained constant. An inspection of the retrieved hearts revealed a large aneurysmal left ventricle (LV) with a thinned myocardium and a significant myocardial fibrosis for that treated with the Empty MSs (without drug encapsulation). However, those receiving the MSs encapsulated with bFGF or Rg(1) attenuated the enlargement of the LV cavity and the development of myocardial fibrosis. The densities of microvessels found in the border zones of the infarct treated with the bFGF or Rg(1) MSs were significantly greater than that treated with the Empty MSs. These results indicated that Rg(1), a stable angiogenic agent, successfully enhanced the myocardial perfusion and preserved the infarcted LV function.

Immobilization of bioactive fibroblast growth factor-2 into cubic proteinous microcrystals (Bombyx mori cypovirus polyhedra) that are insoluble in a physiological cellular environment

The supramolecular architecture of the extracellular matrix and the disposition of its specific accessory molecules give rise to variable heterotopic signaling cues for single cells. Here we have described the successful occlusion of human fibroblast growth factor-2 (FGF-2) into the cubic inclusion bodies (FGF-2 polyhedra) of the Bombyx mori cytoplasmic polyhedrosis virus (BmCPV). The polyhedra are proteinous cubic crystals of several microns in size that are insoluble in the extracellular milieu. Purified FGF-2 polyhedra were found to stimulate proliferation and phosphorylation of p44/p42 mitogen-activated protein kinase in cultured fibroblasts. Moreover, cellular responses were blocked by a synthetic inhibitor of the FGF signaling pathway, SU5402, suggesting that FGF-2 polyhedra indeed act through FGF receptors. Furthermore, FGF-2 polyhedra retained potent growth stimulatory properties even after desiccation. We have demonstrated that BmCPV polyhedra microcrystals that occlude extracellular signaling proteins are a novel and versatile tool that can be employed to analyze cellular behavior at the single cell level.

Stability of angiogenic agents, ginsenoside Rg1 and Re, isolated from Panax ginseng: In vitro and in vivo studies

The study was designed to investigate the stability of ginsenoside Rg(1) (Rg(1)) and Re (Re), two natural herbal compounds isolated from Panax ginseng, based on their activity to promote angiogenesis in vitro and in vivo. After being treated at different temperatures, pHs, and solvent species for distinct durations, the remaining activities of Rg(1) and Re on human umbilical vein endothelial cell (HUVEC) proliferation, migration, and tube formation were examined in vitro. Additionally, the remaining activity of each treated test agent, mixed in a growth factor-reduced Matrigel, in stimulating angiogenesis was evaluated subcutaneously in a mouse model. Basic fibroblast growth factor (bFGF) was used as a control. It was found in vitro that HUVEC proliferation, migration in a Transwell plate, and tube formation on Matrigel were all significantly enhanced in the presence of bFGF, Rg(1), or Re. However, after being treated at different temperatures, pHs, or solvent species, the remaining activity of bFGF on HUVEC behaviors reduced significantly. This observation was more significant with increasing the duration of treatment. In contrast, the activities of Rg(1) and Re remained unchanged throughout the entire course of the study. The in vivo results observed on day 7 after implantation showed that the blank control (Matrigel alone) was slightly vascularized. In contrast, the density of neo-vessels in the Matrigel plug mixed with bFGF, Rg(1), or Re was significantly enhanced. However, after being treated, the density of neo-vessels was significantly reduced in the Matrigel plug mixed with bFGF, while those of Rg(1) and Re remained unchanged. The aforementioned results suggested that Rg(1) and Re could be a novel group of nonpeptide angiogenic agents with a superior stability and may be used for the management of tissue regeneration.

Effects of Cyclodextrins on Chemically and Thermally Induced Unfolding and Aggregation of Lysozyme and Basic Fibroblast Growth Factor

Effects of cyclodextrin (CyDs) on unfolding and aggregation of lysozyme and basic fibroblast growth factor (bFGF) were investigated. CyDs inhibited the chemically induced aggregation and its inhibition was generally in the order of gamma-CyDs < alpha-CyDs < beta-CyDs. Among these CyDs, branched beta-CyDs and dimethyl-beta-CyD (DM-beta-CyD) significantly reduced the aggregation of lysozyme. Hydrophilic CyDs reduced the thermally induced unfolding of lysozyme as shown by a decrease in the thermal unfolding temperature (T(m)) value of lysozyme, suggesting that CyDs destabilize native lysozyme or stabilize the unfolded state of lysozyme. In the case of bFGF, branched beta-CyDs showed greater effects on inhibition of the chemically and thermally induced denaturation. Interestingly, sulfobutyl ether beta-CyD (SBE-beta-CyD), which was not effective in case of lysozyme, provided the inhibitory effect for bFGF on the chemically, thermally and acid-induced denaturation, suggesting that both the inclusion and electrostatic interaction may be operative in the inhibition of aggregation of the positively charged protein. The results indicated that the use of CyDs for protein stabilization is dependent not only on the structure and property of CyDs but also on the nature of the denaturing stimuli, and the most appropriate CyD should be used for the stabilization of each protein.

Fibroblast growth factor 2 induced proliferation in osteoblasts and bone marrow stromal cells: a whole cell model

Fibroblast growth factor 2 (FGF2) can enhance the proliferative capacity of bone and bone marrow stromal cells; however, the mechanisms behind this effect are not well described. We present a whole-cell kinetic model relating receptor-mediated binding, internalization, and processing of FGF2 to osteoblastic proliferative response. Focusing on one of the potential signaling complex stoichiometries, we utilized experimentally measured and modeled estimated rate constants to predict in vitro proliferation and distinguish between potential binding orders. We found that piecewise assemblage of a ternary signaling complex may occur in several ways depending on the local binding environment. Using experimental data of endocytosed FGF2 as a constraint, we have also shown evidence of potential multistep processes involved in heparan-sulfate proteoglycans-bound FGF2 release, internalization, and fragment formation in conjunction with the normal metabolism of the proteoglycan.

Delivery of basic fibroblast growth factor (bFGF) from photoresponsive hydrogel scaffolds

Exogenous growth factor therapy has shown a notable promise in accelerating the healing of acute and chronic wounds. However, their susceptibility to enzymatic degradation and short contact time with the wound bed warrant the use of sophisticated delivery vehicles that stabilize the encapsulated peptides and control their rate of release. Herein, we describe the synthesis of a nitrocinnamate-derived polyethylene glycol (PEG-NC) hydrogel system and study the release kinetics of basic fibroblast growth factor (bFGF) as a function of hydrogel properties. Long-wave ultraviolet irradiation (365 nm) was used to alter the physical properties of the gel scaffold (i.e. degree of swelling) and consequently control the release rates of the encapsulated bFGF. The degree of swelling (DS) decreased from 10.7 to 8 as the length of irradiation increased from 5 to 30 min. Similarly, the DS decreased from 17.5 to 11.5 by increasing the initial PEG-NC concentration from 10 to 30 w/v% while keeping the crosslinking irradiation at 10 min. Radiolabeled I(125) studies were used to monitor the release of bFGF from PEG-NC hydrogels with variable swellabilities. By increasing the length of irradiation from 2 to 10 min the rate of bFGF release from PEG-NC gel scaffolds was decreased by 29% due to the enhanced crosslinking density. The bFGF-releasing PEG-NC hydrogels were not cytotoxic to human neonatal fibroblast cells and the released growth factor maintained its activity and induced fibroblast proliferation and collagen production in vitro. The addition of heparin within the gel scaffolds further increased the growth factor's activity.

Nonclassical transport proteins and peptides: an alternative to classical macromolecule delivery systems

The number of peptides and proteins known to exhibit nonclassical transport activity has increased significantly in recent years. In most cases, these entities have been studied in relation to their ability to deliver high molecular weight compounds, including proteins and DNA, for the ultimate purpose of developing new drug delivery strategies. In this review, an overview of the various types of vectors is presented. The in vitro and in vivo delivery successes of this technology, as well as preliminary therapeutic efforts, are described. Although a comprehensive mechanism of nonclassical transport has not yet been clearly established, we propose a straightforward model based on the cationic nature of the vectors and the need for lack of highly organized structure. In this hypothesis we suggest that the movement of polycations is mediated by a network of extra- and intracellular polyanions while transport across the bilayer is facilitated by cation-pi interactions between the vectors' basic groups and aromatic amino acid side chains in the bilayer spanning helices of membrane proteins.

Identification of a novel domain of fibroblast growth factor 2 controlling its angiogenic properties

Fibroblast growth factor 2 (FGF-2) is a potent factor modulating the activity of many cell types. Its dimerization and binding to high affinity receptors are considered to be necessary steps to induce FGF receptor phosphorylation and signaling activation. A structural analysis was carried out and a region encompassing residues 48-58 of human FGF-2 was identified, as potentially involved in FGF-2 dimerization. A peptide (FREG-48-58) derived from this region strongly and specifically inhibited FGF-2 induced proliferation and migration of primary bovine aorta endothelial cells (BAEC) in vitro, and markedly reduced FGF-2-dependent angiogenesis in two distinct in vivo assays. To further investigate the role of region 48-58, a polyclonal antibody raised against FREG-(48-58) was tested and was found to block FGF-2 action in vitro. Human FGF-2 has three histidine residues, one falling within the region 48-58. Chemical modification of histidine residues blocked FGF-2 activity and FREG-(48-58) inhibitory effect in vitro, indicating that histidine residues, in particular the one within FREG-(48-58) region, play a crucial role in the observed activity. Additional experiments showed that FREG-(48-58) specifically interacted with FGF-2, impaired FGF-2-interaction with itself, with heparin and with FGF receptor 1, and inhibited FGF-2-induced receptor phosphorylation and FGF-2 internalization. These data indicate for the first time that region 48-58 of FGF-2 is a functional domain controlling FGF-2 activity.

Impact of serum basic fibroblast growth factor on prognosis in human renal cell carcinoma

Renal cell carcinoma is often characterised by extensive vascularity and angiogenic factors may be of importance for disease progression. Using a sandwich enzyme immunoassay, basic fibroblast growth factor (bFGF) was analysed in the sera from 206 patients with renal cell carcinoma before the initiation of therapy. The median bFGF level was 3.0 pg/ml (range <1.0-70.9 pg/ml). The serum levels were significantly correlated to tumour stage and nuclear grade. Patients with tumour thrombus to the renal or the inferior caval vein had significantly higher serum bFGF levels compared with those with non-invading tumours (P=0.007). Patients with serum bFGF levels above 3.0 pg/ml had a worse prognosis, compared with those with lower levels (P=0.001). Furthermore, patients with tumours with vein invasion had a worse prognosis compared with those without invasion. After multivariate analysis, only tumour stage and grade remained as independent prognostic factors.

Heparin dodecasaccharide binding to platelet factor-4 and growth-related protein-alpha. Induction of a partially folded state and implications for heparin-induced thrombocytopenia

alpha-Chemokines are known heparin-binding proteins. Here, a heparin dodecasaccharide (H12) was purified and used in NMR studies to investigate binding to growth-related protein-alpha (Gro-alpha) and to platelet factor-4-M2 (PF4-M2), an N-terminal chimera of PF4. Pulsed field gradient NMR was used to derive diffusion coefficients as the protein (monomer):H12 ratio was varied. In the absence of H12, both PF4-M2 and Gro-alpha give diffusion coefficients consistent with the presence of mostly dimers. As the PF4-M2:H12 ratio is increased from 1:6 to 2:1, the diffusion coefficient increases, indicating dissociation to the monomer state. On addition of H12 to either protein, (15)N/(1)H heteronuclear single quantum coherence NMR data demonstrate loss of (1)H resonance dispersion and intensity, particularly at protein:H12 ratios of 2:1 to 4:1, indicating significant perturbation to native structures. For Gro-alpha in particular, (1)H resonance dispersion appears random coil-like. At these same ratios, circular dichroism (CD) data show general retention of secondary structure elements with a slight shift to additional helix formation. Random coil NMR resonance dispersion suggests a shift to a less compact, partially folded, and/or more flexible state. Further addition of H12 causes resonance intensity and dispersion to return making NMR spectra appear native-like. At low PF4-M2:H12 ratios, loss of resonance intensity for residues proximal to Arg-20 and Arg-22 in three-dimensional NMR HCCH-TOCSY spectra suggests that the Arg-20-Arg-22 loop either interacts most strongly with H12 and/or that binding at this site is heterogeneous. This domain was previously shown to be crucial to heparin binding. Of particular interest to the biology of PF4-heparin complex formation, heparin-induced thrombocytopenia antibody binding occurs at about the same PF4-M2:H12 ratio as does this transition to a partially folded PF4-M2 state, strongly suggesting that heparin-induced thrombocytopenia antibody recognizes a less folded, lower aggregate state of the protein.

Susceptibility towards intramolecular disulphide-bond formation affects conformational stability and folding of human basic fibroblast growth factor

The conformational stability and the folding properties of the all-beta-type protein human basic fibroblast growth factor (hFGF-2) were studied by means of fluorescence spectroscopy. The results show that the instability of the biological activity of hFGF-2 is also reflected in a low conformational stability of the molecule. The reversibility of the unfolding and refolding process was established under reducing conditions. Determination of the free-energy of unfolding in the presence of reducing agents revealed that the conformational stability of hFGF-2 (DeltaGH2Oapp congruent with21 kJ. mol-1, 25 degreesC) is low compared with other globular proteins under physiological conditions (20-60 kJ.mol-1). However, the conformational stability of hFGF-2 is particularly low under non-reducing conditions. This instability is attributed to intramolecular disulphide-bond formation, rendering the molecule more susceptible to denaturant-induced unfolding. In addition, denaturant-induced unfolding of hFGF-2 renders the protein more susceptible to irreversible oxidative denaturation. Experimental evidence is provided that the irreversibility of the unfolding and refolding process in the absence of reducing agents is linked to the formation of an intramolecular disulphide bond involving cysteines 96 and 101.

Two-step chromatographic procedure for purification of basic fibroblast growth factor from recombinant Escherichia coli and characterization of the equilibrium parameters of adsorption

A two-step chromatographic procedure for purification of basic fibroblast growth factor (bFGF) from high-cell-density cultures of recombinant E. coli is described. Heparin-Sepharose as a material which shows a high affinity to endothelial growth factors was used as sorbent for purification of bFGF from the soluble cell fraction. A one-step affinity chromatographic procedure resulted in very pure bFGF. However, this one-step affinity isolation of bFGF caused the loss of around 60% of the recombinant protein. A combination of ion-exchange chromatography with heparin-Sepharose affinity chromatography was favored for bFGF purification. A first cation-exchange chromatographic step resulted in a solution of bFGF with a purity of around 70%. The weak cation exchanger CM Sepharose C50 was preferred in comparison to the strong cation exchanger S-Sepharose because of the higher recovery of bFGF. With the ion-exchange chromatographic step prior to the heparin-Sepharose affinity chromatography, the total yield of recovery of bFGF increased to 56% compared to 40% using the one-step purification procedure with heparin-Sepharose. To characterize the equilibrium parameters of adsorption, batch experiments for the calculation of maximum capacities and dissociation constants for CM-Sepharose C50 and heparin-Sepharose were carried out. The equilibrium experiments revealed that adsorption of bFGF to the ion-exchange sorbent followed single-site interaction according to the Langmuir model of adsorption. The adsorption of bFGF to heparin-Sepharose was described by a double Langmuir approach of two independent binding sites with different maximum capacities and dissociation constants. The purified bFGF showed a high biological activity and circular dichroic spectra of a proper folded molecule. The analysis of the N-terminal amino acid sequence revealed a mixture of two fractions of bFGF, which both are characterized by the cleavage of the first amino acid methionine. In addition, half of the bFGF molecules lacked the second amino acid alanine.

Approaches to analysis of aggregates and demonstrating mass balance in pharmaceutical protein (basic fibroblast growth factor) formulations

Denaturation, aggregation, and precipitation, which are common events in protein aging, limit the development of pharmaceutical protein formulations. Using the example of basic fibroblast growth factor (bFGF), we describe a systematic approach for quantitative recovery of soluble and insoluble aggregates in aged samples to achieve mass balance in three analytical methods, UV spectroscopy, size exclusion HPLC (HP-SEC), and reverse phase HPLC. Soluble aggregates were evaluated by UV spectroscopy and HP-SEC; the latter method was modified to include 2 M guanidine hydrochloride (GnHCl) in the mobile phase in order to differentiate and simultaneously analyze native and denatured protein. Insoluble aggregates were first solubilized with GnHCl and then recovered quantitatively with the modified HP-SEC method. Chaotrope treatment did not affect the UV peak absorbance but altered the HPLC profiles. The changes were consistent with dissociation of disulfide-linked multimers to monomers with an intramolecular disulfide linkage. This phenomenon was used for estimation of the monomer-multimer distribution in the untreated aggregated sample. These methods established approaches for quantitative recovery and characterization of bFGF aggregates.