Kinetic and mechanistic considerations in the gelation of genipin-crosslinked gelatin

The gelling properties (gel time (t(gel)) and gel strength) of a 10% (w/w) gelatin sol were investigated as a function of genipin (GP) concentration (0-15 mM) and temperature (25-55 degrees C) to discern mechanisms and optimal conditions for fixation. Gel time increased with increasing temperature, reached a maximum, and then declined as temperature was raised further. By contrast, network strength data followed the opposite trend. From the thermal behavior of t(gel) and network strength, it was inferred that gelation in the low-temperature regime was dominated by hydrogen bonding, while in the high-temperature regime it was dominated by covalent crosslinking. At higher temperatures, crosslinking was described by an Arrhenius rate law expression, with activation energies between 63.2 and 67.8 kJ/mol, depending on GP concentration. In the low temperature regime, an Arrhenius plot resulted in negative activation energies of -75.8 and -64.4 kJ/mol in the presence of 10 and 15 mM GP, respectively. With an increase in both GP concentration and temperature, the gelatin network gradually shifted from being dominated by hydrogen bonds (physical crosslinks) to covalent crosslinking (chemical crosslinks).

Controlled in vivo degradation of genipin crosslinked polyethylene glycol hydrogels within osteochondral defects

Polyethylene glycol (PEG) hydrogels show promise as scaffolds for growth factor delivery to enhance cartilage repair. However, methods to control growth factor release in vivo are needed. We have recently shown that in vitro polymer degradation and in vitro growth factor release kinetics can be altered using PEG crosslinked with different concentrations of genipin. However, the degradation and behavior of PEG-genipin in vivo within the cartilage repair site are unknown. This study was conducted to test the hypotheses that the degradation of PEG-genipin can be altered in vivo within osteochondral defects by changing the concentration of genipin, and that PEG-genipin is biocompatible within the mammalian diarthrodial environment. PEG-genipin cylindrical polymers crosslinked using 8mM, 17.6 mM, or 35.2 mM of genipin were implanted into osteochondral defects made in the trochlea of 24 male Sprague- Dawley rats (48 knees). Rats were sacrificed at 5 weeks and gross, cross-sectional, and histologic assessments were performed. Altering the genipin concentration changed the in vivo degradation properties of the hydrogel ( p < 0.01). Consistent with in vitro findings, polymer degradation was inversely related to the concentration of genipin. Near-complete degradation was seen at 8 mM, intermediate degradation at 17.6 mM, and minimal degradation at 35.2 mM. The results of this study show the degradation of PEGgenipin can be altered in vivo within osteochondral defects by changing the concentration of genipin and that PEG-genipin is biocompatible within osteochondral defects. This new in vivo data support potential use of PEG-genipin polymer as an innovative delivery system to control in vivo release of growth factors for improving articular cartilage repair.

Genipin suppression of fibrogenic behaviors of the α-TN4 lens epithelial cell line

PURPOSE

To determine in a lens epithelial cell line, alpha-TN4, whether genipin, an intestinal metabolite component of the herbal medicine inchin-ko-to, suppresses profibrogenic myofibroblast generation and upregulation of fibrogenic cytokines and to evaluate the potential benefit of the medicine in preventing posterior capsule opacification (PCO).

SETTING

Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan.

METHODS

In this study, alpha-TN4 cell proliferation, migration, and expression of alpha-smooth muscle actin (alpha-SMA), the hallmark of myofibroblast generation, were assayed with a colorimetric assay, scratch wound assay, immunohistochemistry, and Western blot analysis. Gene expression of transforming growth factor-beta1 (TGF-beta1) and connective tissue growth factor (CTGF) was characterized with real-time reverse transcription-polymerase chain reaction. In addition, p38 mitogen-activated protein kinase (p 38 MAPK), extracellular signal-regulated kinase (ERK) limb, and Smad signalings were evaluated by Western blotting and immunohistochemistry. Cytotoxicity of genipin was evaluated using a commercial colorimetric assay kit for nuclear matrix protein 41/7 (NMP41/7) in culture medium.

RESULTS

Genipin suppressed cell proliferation and migration in association with inhibition of Smad and p38 MAPK phosphorylation, although ERK signaling was enhanced. Genipin suppressed mRNA expression of TGF-beta1 and CTGF. Cytoplasmic fiber formation declined based on less intense alpha-SMA immunocytochemical staining. However, alpha-SMA protein expression was actually not altered. This negative result suggests that genipin attenuated formation of alpha-SMA-containing cytoskeleton. Treatment of the cells with genipin for 48 hours did not increase the release of NMP41/7 to the medium, indicating this compound is not cytotoxic.

CONCLUSION

Because genipin suppressed alpha-TN4 lens cell fibrogenic behaviors, it may be of therapeutic value in preventing PCO.

Exogenous cross-linking increases the stability of spinal motion segments

STUDY DESIGN

The mechanical stability of cross-linked and control spinal motion segments was evaluated using neutral zone, range of motion (ROM), and instability score metrics.

OBJECTIVE

To determine if exogenous cross-linking could increase the stability of spinal motion segments.

SUMMARY OF BACKGROUND DATA

The microstructure of the anulus fibrosus extracellular matrix can affect the stability of the intervertebral joint. Parallel testing in our laboratory has shown that exogenous cross-linking can improve the fatigue resistance of anulus fibrosus.

METHODS

There were 3 separate experimental protocols conducted. The first study used calf lumbar intervertebral joints randomly divided into a genipin cross-linked group and phosphate buffered saline-soaked controls. After 2 days of soaking, flexion-extension ramp cycles were applied to the specimens. The second study repeated the test protocol using 22 moderately and severely degenerated human lumbar intervertebral joints. The third experiment compared the effect of cross-linking treatment on human discs with known degrees of preexisting mechanical instability. Each data set was used to assess joint instability by 3 calculations: ROM, neutral zone, and an instability score. Joint instability for each data set was evaluated using 3 calculations: ROM, neutral zone, and a novel instability score.

RESULTS

These results show that cross-link augmentation can effectively reduce instability of intervertebral discs. The stabilizing effect was observed to be higher in the more mechanically unstable discs. However, cross-linking did not appear to affect the total range of sagittal motion.

CONCLUSIONS

By reducing the neutral zone, exogenous cross-linking may help combat the progression of instability in degenerative disc disease.

Genipin Cross-Linked Alginate-Chitosan Microcapsules: Membrane Characterization and Optimization of Cross-Linking Reaction

The genipin cross-linked alginate-chitosan (GCAC) microcapsule, composed of an alginate core and a genipin cross-linked chitosan membrane, was recently proposed for live cell encapsulation and other delivery applications. This article for the first time describes the details of the microcapsule membrane characterization using a noninvasive and in situ method without any physical or chemical modifications on the samples. Results showed that the cross-linking reaction generated the fluorescent chitosan-genipin conjugates. The cross-linked chitosan membrane was clearly visualized by confocal laser scanning microscopy (CLSM). A straightforward assessment on the membrane thickness and relative intensity was successfully achieved. CLSM studies showed that the shell-like cross-linked chitosan membranes of approximately 37 microm in thickness were formed surrounding the microcapsule. The reaction variables, including cross-linking temperature and time significantly affected the fluorescence intensity of the membranes. Elevating the cross-linking temperature from 4 to 37 degrees C drastically intensified the membrane fluorescence, suggesting the attainment of a high degree of cross-linking on the chitosan membrane. Extended cross-linking time altered the cross-linked membranes in modulation. Although genipin concentration and cross-linking time had little effects on the membrane thickness, cross-linking at higher temperatures tended to form relatively thinner membranes.

Genipin inhibits UCP2-mediated proton leak and acutely reverses obesity- and high glucose-induced beta cell dysfunction in isolated pancreatic islets

Uncoupling protein 2 (UCP2) negatively regulates insulin secretion. UCP2 deficiency (by means of gene knockout) improves obesity- and high glucose-induced beta cell dysfunction and consequently improves type 2 diabetes in mice. In the present study, we have discovered that the small molecule, genipin, rapidly inhibits UCP2-mediated proton leak. In isolated mitochondria, genipin inhibits UCP2-mediated proton leak. In pancreatic islet cells, genipin increases mitochondrial membrane potential, increases ATP levels, closes K(ATP) channels, and stimulates insulin secretion. These actions of genipin occur in a UCP2-dependent manner. Importantly, acute addition of genipin to isolated islets reverses high glucose- and obesity-induced beta cell dysfunction. Thus, genipin and/or chemically modified variants of genipin are useful research tools for studying biological processes thought to be controlled by UCP2. In addition, these agents represent lead compounds that comprise a starting point for the development of therapies aimed at treating beta cell dysfunction.

Proton and Sodium Cation Affinities of Harpagide: A Computational Study

The aim of this work was to estimate the proton and sodium cation affinities of harpagide (Har), an iridoid glycoside responsible for the antiinflammatory properties of the medicinal plant Harpagophytum. Monte Carlo conformational searches were performed at the semiempirical AM1 level to determine the most stable conformers for harpagide and its protonated and Na+-cationized forms. The 10 oxygen atoms of the molecule were considered as possible protonation and cationization sites. Geometry optimizations were then refined at the DFT B3LYP/6-31G level from the geometries of the most stable conformers found. Final energetics were obtained at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G level. The proton and sodium ion affinities of harpagide have been estimated at 223.5 and 66.0 kcal/mol, respectively. Since harpagide mainly provides HarNa+ ions in electrospray experiments, the DeltarG298 associated with the reaction of proton/sodium exchange between Har and methanol, MeOHNa+ + HarH+ --> MeOH2+ + HarNa+ (1), has been calculated; it has been estimated to be 1.9 kcal/mol. Complexing a methanol molecule to each reagent and product of reaction 1 makes the reaction become exothermic by 1.7 kcal/mol. These values are in the limit of the accuracy of the method and do not allow us to conclude definitely whether the reaction is endo- or exothermic, but, according to these very small values, the cation exchange reaction is expected to proceed easily in the final stages of the ion desolvation process.

The effect of nucleus pulposus crosslinking and glycosaminoglycan degradation on disc mechanical function

Altered mechanical loading, secondary to biochemical changes in the nucleus pulposus, is a potential mechanism in disc degeneration. An understanding of the role of this altered mechanical loading is only possible by separating the mechanical and biological effects of early nucleus pulposus changes. The objective of this study was to quantify the mechanical effect of decreased glycosaminoglycans (GAG) and increased crosslinking in the nucleus pulposus using in vitro rat lumbar discs. Following initial mechanical testing the discs were injected according to the four treatment groups: PBS control, chondroitinase-ABC (ChABC) for GAG degradation, genipin (Gen) for crosslinking, or a combination of chondroitinase and genipin (ChABC+Gen). After treatment the discs were again mechanically tested, followed by histology or biochemistry. Neutral zone mechanical properties were changed by approximately 20% for PBS, ChABC, and ChABC+Gen treatments (significant only for PBS in a paired comparison). These trends were reversed with genipin crosslinking alone. With ChABC treatment the effective compressive modulus increased and the GAG content decreased; with the combination of ChABC+Gen the mechanics and GAG content were unchanged. Degradation of nucleus pulposus GAG alters disc axial mechanics, potentially contributing to the degenerative cascade. Crosslinking is unlikely to contribute to degeneration, but may be a potential avenue of treatment.

Controlled release of bioactive TGF-β1 from microspheres embedded within biodegradable hydrogels

Transforming growth factor-beta1 (TGF-beta1) is of great relevance to cartilage development and regeneration. A delivery system for controlled release of growth factors such as TGF-beta1 may be therapeutic for cartilage repair. We have encapsulated TGF-beta1 into poly(DL-lactide-co-glycolide) (PLGA) microspheres, and subsequently incorporated the microspheres into biodegradable hydrogels. The hydrogels are poly(ethylene glycol) based, and the degradation rate of the hydrogels is controlled by the non-toxic cross-linking reagent, genipin. Release kinetics of TGF-beta1 were assessed using ELISA and the bioactivity of the released TGF-beta1 was evaluated using a mink lung cell growth inhibition assay. The controlled release of TGF-beta1 encapsulated within microspheres embedded in scaffolds is better controlled when compared to delivery from microspheres alone. ELISA results indicated that TGF-beta1 was released over 21 days from the delivery system, and the burst release was decreased when the microspheres were embedded in the hydrogels. The concentration of TGF-beta1 released from the gels can be controlled by both the mass of microspheres embedded in the gel, and by the concentration of genipin. Additionally, the scaffold permits containment and conformation of the spheres to the defect shape. Based on these in vitro observations, we predict that we can develop a microsphere-loaded hydrogel for controlled release of TGF-beta1 to a cartilage wound site.

Anti-inflammatory evaluation of gardenia extract, geniposide and genipin

Gardenia fruit has been traditionally used as a folk medicine for centuries in Asian countries. Extraction with ethanol was used to obtain an extract (GFE) that contains two known constituents, geniposide and genipin, which were subsequently evaluated for anti-inflammatory activity. GFE, genipin, and geniposide showed acute anti-inflammatory activities in carrageenan-induced rat paw edema. In a dose-dependent manner, GFE also inhibited vascular permeability induced by acetic acid. Both genipin and geniposide inhibited production of exudate and nitric oxide (NO) in the rat air pouch edema model. However, genipin possessed stronger anti-inflammatory activity than geniposide, as demonstrated by the results with carrageenan-induced rat paw edema, carrageenan-induced air pouch formation, and measurement of NO content in the exudates. GFE caused a dose-dependent inhibition of acetic acid-induced abdominal writhing in mice. Collectively, genipin, rather than geniposide, is the major anti-inflammatory component of gardenia fruit.

Some physical and microstructural properties of genipin-crosslinked gelatin–maltodextrin hydrogels

The physical properties and microstructure of gelatin-maltodextrin hydrogels fixed with genipin (GP) were investigated as a function of pH (3-7), maltodextrin (MD) (0-9%, w/w) and GP (0-10 mM levels), at a constant gelatin (G) concentration (10%, w/w). Network strength (elastic modulus, E) and swelling behavior were characterized by large deformation testing and by swelling index (SI). In general, network strength increased and swelling decreased at higher pH, MD and GP levels, except at pH 3, where E was independent of the GP concentration until approximately 7.5 mM, above which it declined. Confocal scanning laser microscopy (CLSM) images showed phase separation to be suppressed at pH 3, whereas at pH 7, separation into a self-similar dispersed phase was apparent. Overall, the judicious use of GP to crosslink G was an appropriate means of kinetically trapping MD within the gelatin network.

The potential of chitosan-based gels containing intervertebral disc cells for nucleus pulposus supplementation

The suitability of chitosan-based hydrogels as scaffolds for the encapsulation of intervertebral disc (IVD) cells and the accumulation of a functional extracellular matrix mimicking that of the nucleus pulposus (NP) was investigated. The specific hypothesis under study was that the cationic chitosan would form an ideal environment in which large quantities of newly synthesized anionic proteoglycan could be entrapped. Indeed, all the formulations of cell-seeded chitosan hydrogels, studied under in vitro culture conditions, showed that the majority of proteoglycan produced by encapsulated NP cells was retained within the gel rather than released into the culture medium. This was not always the case when annulus fibrosus cells were encapsulated, as unlike the nucleus cells the annulus cells often did not survive when cultured in chitosan. The results support the concept that chitosan may be a suitable scaffold for cell-based supplementation to help restore the function of the NP during the early stages of IVD degeneration.

A New Method for Microcapsule Characterization: Use of Fluorogenic Genipin to Characterize Polymeric Microcapsule Membranes

Numerous microcapsule systems have been developed for a wide range of applications, including the sustained release of drugs, cell transplantation for therapy, cell immobilization, and other biotechnological applications. Despite the fact that microcapsule membrane is a dominant factor governing overall microcapsule performance, its characterization is challenging. We report a new method for characterizing microcapsule membranes, using the most common alginate-poly-L-lysine-alginate (APA) microcapsule as an example. Our data demonstrate that genipin, a naturally derived reagent extracted from gardenia fruits, interacts with poly-L-lysine (PLL) and generates fluorescence. This fluorescence allows clear visualization and easy analysis of the PLL membrane in the APA microcapsules using confocal laser scanning microscopy. The results also show that PLL binding correlates to the reaction variables during PLL coating such as PLL concentration and coating time. In addition, five other different microcapsule formulations consisting of PLL and/or chitosan membranes were examined, and the results imply that this method can be extended to characterize a variety of microcapsule membranes. These findings suggest that genipin can serve as a fluorogenic marker for rapid characterization of microcapsule membranes, a superior method that would have important implications for microcapsule research and potential in many other applications.

Liquid chromatography/electrospray ionization mass spectrometric characterization of Harpagophytum in equine urine and plasma

A method has been developed for the analysis and characterization in equine urine and plasma of iridoid glycosides: harpagide, harpagoside and 8-para-coumaroyl harpagide, which are the main active principles of Harpagophytum, a plant with antiinflammatory properties. The method involves liquid chromatography coupled with positive electrospray ionization mass spectrometry. The addition of sodium or lithium chloride instead of formic acid in the eluting solvent has been studied in order to enhance the signal and to modify the ion's internal energy. Fragmentation pathways and associated patterns are proposed for each analyte. A comparison of three types of mass spectrometer: a 3D ion trap, a triple quadrupole and a linear ion trap, has been conducted. The 3D ion trap was selected for drug screening analysis whereas the linear ion trap was retained for identification and quantitation analysis.

Effect of genipin-crosslinked chitin-chitosan scaffolds with hydroxyapatite modifications on the cultivation of bovine knee chondrocytes

Chitin and chitosan were hybridized in various weight percentages by genipin crosslinkage under various prefreezing temperatures to form tissue-engineering scaffolds via lyophilization. In addition, deposition of hydroxyapatite (HA) on the surface of the porous scaffolds was performed by precipitation method to achieve modified chemical compositions for chondrocyte attachments and growths. The experimental results revealed that a lower prefreezing temperature or a higher weight percentage of chitin in the chitin-chitosan scaffolds would yield a smaller pore diameter, a greater porosity, a larger specific surface area, a higher Young's modulus, and a lower extensibility. Moreover, a higher chitin percentage could also result in a higher content of amine groups after crosslink and a lower onset temperature for the phase transition after thermal treatment. A decrease in the prefreezing temperature from -4 degrees C to -80 degrees C, an increase in the chitin percentage from 20% to 50%, and an increase in the cycle number of alternate immersion for HA deposition from 1 to 5 generated positive effects on the cell number, the content of glycosaminoglycans, and the collagen level over 28-day cultivation of bovine knee chondrocytes.

Tissue regeneration observed in a porous acellular bovine pericardium used to repair a myocardial defect in the right ventricle of a rat model

OBJECTIVE

Nonliving synthetic materials have been widely used to repair myocardial defects; however, material-related failures do occur. To overcome these problems, an acellular bovine pericardium with a porous structure fixed with genipin (the AGP patch) was developed.

METHODS

The AGP patch was used to repair a surgically created myocardial defect in the right ventricle of a rat model. A commercially available expanded polytetrafluoroethylene (e-PTFE) patch was used as a control. At retrieval, a computerized mapping system was used to acquire local epicardial electrograms of each implanted sample, and the appearance of each retrieved sample was grossly examined. The retrieved samples were then processed for histologic examination.

RESULTS

The amplitude of local electrograms on the AGP patch increased significantly with increasing implantation duration, whereas only low-amplitude electrograms were observed on the e-PTFE patch throughout the entire course of the study. No aneurysmal dilation of the implanted patches was seen for either studied group. Additionally, no tissue adhesion was observed on the outer (epicardial) surface of the AGP patch, whereas a moderate tissue adhesion was observed on the e-PTFE patch. On the inner (endocardial) surface, intimal thickening was observed for both studied groups; however, no thrombus formation was found. Intact layers of endothelial and mesothelial cells were identified on the inner and outer surfaces of the AGP patch, respectively. At 4 weeks postoperatively, smooth muscle cells, together with neomuscle fibers (with a few neocollagen fibrils), neoglycosaminoglycans, and neocapillaries, were observed to fill the pores in the AGP patch, an indication of tissue regeneration. These observations were more pronounced at 12 weeks postoperatively. In contrast, no apparent tissue regeneration was observed in the e-PTFE patch.

CONCLUSION

The present study indicated that the AGP patch holds promise to become a suitable patch for surgical repair of myocardial defects.

Genipin-induced apoptosis in hepatoma cells is mediated by reactive oxygen species/c-Jun NH2-terminal kinase-dependent activation of mitochondrial pathway

Genipin, the aglycone of geniposide, exhibits anti-inflammatory and anti-angiogenic activities. Here we demonstrate that genipin induces apoptotic cell death in FaO rat hepatoma cells and human hepatocarcinoma Hep3B cells, detected by morphological cellular changes, caspase activation and release of cytochrome c. During genipin-induced apoptosis, reactive oxygen species (ROS) level was elevated, and N-acetyl-l-cysteine (NAC) and glutathione (GSH) suppressed activation of caspase-3, -7 and -9. Stress-activated protein kinase/c-Jun NH2-terminal kinase 1/2(SAPK/JNK1/2) but neither MEK1/2 nor p38 MAPK was activated in genipin-treated hepatoma cells. SP600125, an SAPK/JNK1/2 inhibitor, markedly suppressed apoptotic cell death in the genipin-treated cells. The FaO cells stably transfected with a dominant-negative c-Jun, TAM67, was less susceptible to apoptotic cell death triggered by genipin. Diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase, inhibited ROS generation, apoptotic cell death, caspase-3 activation and JNK activation. Consistently, the stable expression of Nox1-C, a C-terminal region of Nox1 unable to generate ROS, blocked the formation of TUNEL-positive apoptotic cells, and activation of caspase-3 and JNK in FaO cells treated with genipin. Our observations imply that genipin signaling to apoptosis of hepatoma cells is mediated via NADPH oxidase-dependent generation of ROS, which leads to downstream of JNK.

A novel drug-eluting stent spray-coated with multi-layers of collagen and sirolimus

In the study, a novel drug-eluting stent for treating the coronary arterial stenosis was developed. Using a spray-coating method, aqueous bovine type I collagen and sirolimus were coated layer-by-layer alternatively onto the surface of a metallic stent and a topcoat of collagen was used as a barrier to control drug release. To prevent dissolution of the collagen matrices, the spray-coated collagen was further crosslinked by genipin, a naturally occurring crosslinking agent. The results obtained in the atomic force microscopy (AFM) examination suggested that the spray-coated collagen was tightly adhered to the surface of the stent. Additionally, the collagen coating was demonstrated by the scanning electron microscopy (SEM) to be sufficiently flexible to allow balloon expansion of the stent without cracking or peeling from the wire. The resistance against enzymatic degradation and the hemocompatibility of the collagen matrices increased significantly as their degree of crosslinking increased. All the studied sirolimus-loaded stents exhibited a nearly linear sustained-release profile (except at the end stage of release) with no significant burst releases. It was found that a topcoat of collagen on the collagen/sirolimus coated stent did slow down the release of sirolimus to some extent. Additionally, the number of layers of collagen/sirolimus coated significantly affected the duration of sirolimus released. Furthermore, the sustained-release duration of sirolimus was proportional to the actual amount of drug loaded on the stent. The aforementioned results indicated that the drug-eluting stent developed had a tightly adhered collagen coating and can be used as a drug reservoir to sustain release of sirolimus.

Genipin, a novel fingerprint reagent with colorimetric and fluorogenic activity, part II: optimization, scope and limitations

Genipin, a hydrolytic product of geniposide extracted from gardenia fruit, was thoroughly studied as a potential fingerprint reagent, and optimal conditions for fingerprint development have been determined. Latent fingerprints on paper items that have been treated with a non-ink running formulation containing 0.17% of the reagent, showed up as both colored and fluorescent images. On brown wrapping paper and on papers with highly luminescent backgrounds, genipin developed more visible and clearer prints than did classical reagents such as ninhydrin or DFO. Another potential advantage of genipin is that it is totally harmless and an environmentally friendly reagent.

Differences in neuritogenic response to nitric oxide in PC12 and PC12h cells

We have demonstrated that a natural iridoid compound, genipin, induces neurite outgrowth through the nitric oxide (NO)-cGMP-protein kinase G signaling pathway in PC12h cells. PC12 cells, the parental cell line of PC12h cells, have been shown to carry out neurite extension that accompanies NO production in response to nerve growth factor (NGF). This neurite outgrowth was significantly inhibited by NG-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, in both PC12 and PC12h cells, suggesting that the neuritogenesis is NO-dependent in both cells. In this report, we investigated whether genipin also induces neurite outgrowth in PC12 cells in order to determine the NO-dependent neurotrophic action of genipin in more than just one cell type. Genipin induced marked neurite outgrowth in PC12h cells but not in PC12 cells. The genipin-induced neurite outgrowth was significantly inhibited by L-NAME in PC12h cells. An NO donor, NOR4, also significantly induced neurite outgrowth in a concentration-dependent manner in PC12h cells but not in PC12 cells. On the other hand, NGF-primed PC12 cells exhibited significant neurite extension, which was inhibited by L-NAME, in response to genipin. Interestingly, NGF-primed PC12 cells responded to NOR4 extending neurites and expressed detectable neuronal NO synthase protein which is not detected in naive PC12 cells. These results suggest that genipin exerts a neuritogenic action on neuronal cells which are responsive to NO itself. Furthermore, the results also suggest that PC12h cells are more suitable for the study of NO-dependent neuronal function than PC12 cells which were not responsive to NO.

Cell-free xenogenic vascular grafts fixed with glutaraldehyde or genipin: in vitro and in vivo studies

Chronic rejection of arterial xenografts results in aneurysmal dilation, due to immune mediated processes. To minimize the immunologic degradation of the graft, a cell-extraction process employing sodium dodecyl sulfate (SDS) was used in the study to remove the cellular components in bovine carotid arteries. To further reduce their immunogenicity, the acellular arteries were fixed with glutaraldehyde (A-GA) or genipin (A-GP). The in vitro properties of all test samples were analyzed. Additionally, the in vivo performance of the heparinized A-GA and A-GP grafts (H-A-GA and H-A-GP) was evaluated in a canine model. It was found that the SDS treatment effectively removed cells from the arterial wall, but the main structures of the extracellular matrix were preserved with a portion of the water-soluble glycosaminoglycans removed. After cell extraction, the elastic lamellae in the media became straightened, and thus made the tissue less extensile. The heparinized tissues significantly reduced platelet adhesion. At retrieval, all implanted grafts were patent and not dilated. Chronic inflammatory response surrounding the implants was observed. However, fixation of acellular tissues by glutaraldehyde or genipin inhibited immune cell penetration into the media and limited tissue degradation, and therefore prevented the arterial wall from dilation. Nevertheless, the H-A-GP graft was superior to the H-A-GA graft in completeness of endothelialization on its luminal surface, and thus precluded thrombus formation.

[Isolation and characterization of phenylethanoid glycosides from Clerodendron bungei]

AIM

To study the chemical constituents from Clerodendron bungei Steud.

METHODS

The compounds were isolated and purified by various chromatographic techniques and identified by their physicochemical properties and spectral data.

RESULTS

Ten phenylethanoid glycosides were isolated and identified as clerodendronoside (1), acteoside (2), isoacteoside (3), cistanoside C (4), jionoside C (5), leucosceptoside A (6), cistanoside D (7), campneoside I (8), campneoside II (9), cistanoside F (10).

CONCLUSION

Compound 1 is a new phenylethanoid glycoside, while compounds 4-10 are obtained from this plant for the first time.

Peritoneal Regeneration Induced by an Acellular Bovine Pericardial Patch in the Repair of Abdominal Wall Defects

BACKGROUND

This study was to evaluate the feasibility of using an acellular bovine pericardium fixed with genipin (AGP) to repair an abdominal wall defect created in a rat model.

MATERIALS AND METHODS

The glutaraldehyde-fixed acellular pericardium (AGA), the genipin-fixed cellular pericardium (GP), and a commercially available polypropylene mesh were used as controls.

RESULTS

Gross examination at 3-month post-operatively revealed that dense adhesions to the visceral organs were observed for the polypropylene mesh and the AGA patch, while a filmy to dense adhesion was seen for the GP patch. In contrast, no adhesion to the visceral organs was observed for the AGP patch. Histologically, inflammatory cells were found mainly surrounding the GP patch. In contrast, host cells (inflammatory cells, fibroblasts, and neo-capillaries) were able to infiltrate into the AGA and AGP patches. Unlike the AGA patch, the AGP patch retrieved at 1-month post-operatively became well integrated with the host tissue near the suture line. Additionally, there were some mesothelial cells, identified by the van Gieson stain, observed on the AGP patch. At 3-month post-operatively, a neo-peritoneum was observed on the AGP patch. The neo-peritoneum consisted of organized vascularized connective tissues covered by an intact layer of mesothelial cells. The calcium contents of the polypropylene mesh and the AGA patch increased significantly at 3-month post-operatively, while those of the GP and AGP patches stayed minimal throughout the entire course of the study.

CONCLUSIONS

The results obtained in the study revealed that the AGP patch effectively repaired abdominal wall defects in rats and successfully prevented the formation of post-surgical abdominal adhesions.

PEG-grafted chitosan as an injectable thermosensitive hydrogel for sustained protein release

Thermosensitive polymer hydrogels that undergo a sol-to-gel transition in response to temperature changes are of great interest in therapeutic delivery and tissue engineering as injectable depot systems. A chitosan-based, injectable thermogel was prepared by grafting an appropriate amount of PEG onto the chitosan backbone and studied for drug release in vitro using bovine serum albumin (BSA) as a model protein. When more than approximately 40 wt.% of PEG was grafted to chitosan chains via covalent bonding, the aqueous solution of the resultant copolymer was an injectable liquid at low temperature and transformed to a semisolid hydrogel at body temperature. After an initial burst release in the first 5 h, a steady linear release of protein from the hydrogel was achieved for a period of approximately 70 h. Prolonged quasi-linear release of protein up to 40 days was achieved by crosslinking the hydrogel with genipin in situ, in a fashion suitable for protein encapsulation while maintaining the injectability of the hydrogel. The crosslinkage transformed the copolymer from a physical gel to an insoluble chemical gel and substantially reduced the initial burst release of protein. Both high performance liquid chromatography (HPLC) and gel electrophoresis indicated that the primary structure of BSA released from the hydrogels with or without genipin-crosslinking was generally conserved. The hydrogel can be prepared in solutions with a physiological pH, allowing the safe incorporation of bioactive molecules for a broad range of medical applications, particularly for sustained in vivo drug release and tissue engineering.

An in vivo evaluation of a biodegradable genipin-cross-linked gelatin peripheral nerve guide conduit material

We evaluated peripheral nerve regeneration using a biodegradable nerve conduit, which was made of genipin-cross-linked gelatin. The genipin-cross-linked gelatin conduit (GGC) was dark blue in appearance, which was concentric and round with a rough outer surface whereas its inner lumen was smooth. After subcutaneous implantation on the dorsal side of the rat, the GGC only evoked a mild tissue response, forming a thin tissue capsule surrounding the conduit. Biodegradability of the GGC and its effectiveness as a guidance channel were examined as it was used to repair a 10 mm gap in the rat sciatic nerve. As a result, tube fragmentation was not obvious until 6 weeks post-implantation and successful regeneration through the gap occurred in all the conduits at the three experimental periods of 4, 6, and 8 weeks. Histological observation showed that numerous regenerated nerve fibers, mostly unmyelinated and surrounded by Schwann cells, crossed through and beyond the gap region 6 weeks after operation. Peak amplitude and area under the muscle action potential curve both showed an increase as a function of the recovery period, indicating that the nerve had undergone adequate regeneration. Thus, the GGC can not only be an effective aids for regenerating nerves but can also lead to favorable nerve functional recovery.