Fluorogenic Hyaluronan Nanogels Track Individual Early Protein Aggregates Originated under Oxidative Stress

Proteins are broadly versatile biochemical materials, whose functionality is tightly related to their folding state. Native folding can be lost to yield misfolded conformations, often leading to formation of protein oligomers, aggregates, and biomolecular phase condensates. The fluorogenic hyaluronan HA-RB, a nonsulfonated glycosaminoglycan with a combination of polyanionic character and of hydrophobic spots due to rhodamine B dyes, binds to early aggregates of the model protein cytoplasmic glyceraldehyde-3-phosphate dehydrogenase 1 from Arabidopsis thaliana (AtGAPC1) since the very onset of the oligomeric phase, making them brightly fluorescent. This initial step of aggregation has, until now, remained elusive with other fluorescence- or scattering-based techniques. The information gathered from nanotracking (via light-sheet fluorescence microscopy) and from FCS in a confocal microscope converges to highlight the ability of HA-RB to bind protein aggregates from the very early steps of aggregation and with high affinity. Altogether, this fluorescence-based approach allows one to monitor and track individual early AtGAPC1 aggregates in the size range from 10 to 100 nm with high time (∼10-2 s) and space (∼250 nm) resolution.

CXCL17 binds efficaciously to glycosaminoglycans with the potential to modulate chemokine signaling

Introduction

CXCL17 is a mucosally secreted protein, and the most recently identified human chemokine, an assignment based on protein fold prediction and chemotactic activity for leukocytes. However, these credentials have been the subject of much recent discussion and no experimental evidence has been presented regarding the definitive structure of CXCL17. In this study, we evaluated the structural and chemoattractant credentials of CXCL17 to better characterize this molecule, and gain deeper insights into its functional role as a glycosaminoglycan (GAG) binding protein.

Methods

In the absence of structural information, in silico modeling techniques assessed the likelihood of CXCL17 adopting a chemokine fold. Recombinant CXCL17 was synthesized in mammalian and prokaryotic systems. Modified Boyden chamber and real-time chemotaxis assays assessed the ability of CXCL17 to promote chemotaxis of murine splenocytes, human neutrophils, and CXCR1 transfectants. The efficacy of CXCL17 binding to GAGs was quantified with solid-phase assays and bio-layer interferometry techniques.

Results

All modeling efforts failed to support classification of CXCL17 as a chemokine based on its predicted conformation. Recombinant CXCL17 was observed to dimerize as a function of concentration, a characteristic of several chemokines. Contrary to a previous report, CXCL17 was not chemotactic for murine splenocytes, although it was a low-potency chemoattractant for human neutrophils at micromolar concentrations, several orders of magnitude higher than those required for CXCL8. As anticipated owing to its highly basic nature, CXCL17 bound to GAGs robustly, with key C-terminal motifs implicated in this process. While inactive via CXCR1, CXCL17 was found to inhibit CXCR1-mediated chemotaxis of transfectants to CXCL8 in a dose-dependent manner.

Discussion

In summary, despite finding little evidence for chemokine-like structure and function, CXCL17 readily bound GAGs, and could modulate chemotactic responses to another chemokine in vitro. We postulate that such modulation is a consequence of superior GAG binding, and that C-terminal fragments of CXCL17 may serve as prototypic inhibitors of chemokine function.

Novel Insight Into Glycosaminoglycan Biosynthesis Based on Gene Expression Profiles

Glycosaminoglycans (GAGs) including chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate, except for hyaluronan that is a free polysaccharide, are covalently attached to core proteins to form proteoglycans. More than 50 gene products are involved in the biosynthesis of GAGs. We recently developed a comprehensive glycosylation mapping tool, GlycoMaple, for visualization and estimation of glycan structures based on gene expression profiles. Using this tool, the expression levels of GAG biosynthetic genes were analyzed in various human tissues as well as tumor tissues. In brain and pancreatic tumors, the pathways for biosynthesis of chondroitin and dermatan sulfate were predicted to be upregulated. In breast cancerous tissues, the pathways for biosynthesis of chondroitin and dermatan sulfate were predicted to be up- and down-regulated, respectively, which are consistent with biochemical findings published in the literature. In addition, the expression levels of the chondroitin sulfate-proteoglycan versican and the dermatan sulfate-proteoglycan decorin were up- and down-regulated, respectively. These findings may provide new insight into GAG profiles in various human diseases including cancerous tumors as well as neurodegenerative disease using GlycoMaple analysis.

Intra-articular low-dose parathyroid hormone (1-34) improves mobility and articular cartilage quality in a preclinical age-related knee osteoarthritis model

Aims

Osteoarthritis (OA) is prevalent among the elderly and incurable. Intra-articular parathyroid hormone (PTH) ameliorated OA in papain-induced and anterior cruciate ligament transection-induced OA models; therefore, we hypothesized that PTH improved OA in a preclinical age-related OA model.

Methods

Guinea pigs aged between six and seven months of age were randomized into control or treatment groups. Three- or four-month-old guinea pigs served as the young control group. The knees were administered 40 μl intra-articular injections of 10 nM PTH or vehicle once a week for three months. Their endurance as determined from time on the treadmill was evaluated before kill. Their tibial plateaus were analyzed using microcalculated tomography (μCT) and histological studies.

Results

PTH increased the endurance on the treadmill test, preserved glycosaminoglycans, and reduced Osteoarthritis Research Society International score and chondrocyte apoptosis rate. No difference was observed in the subchondral plate bone density or metaphyseal trabecular bone volume and bone morphogenetic 2 protein staining.

Conclusion

Subchondral bone is crucial in the initiation and progression of OA. Although previous studies have shown that subcutaneous PTH alleviates knee OA by improving subchondral and metaphyseal bone mass, we demonstrated that intra-articular PTH injections improved spontaneous OA by directly affecting the cartilage rather than the subchondral or metaphyseal bone in a preclinical age-related OA model.

Cite this article: Bone Joint Res 2021;10(8):514–525.

Electron-Activated Tandem Mass Spectrometry Analysis of Glycosaminoglycans

Glycosaminoglycans (GAGs) are linear polysaccharides found in a variety of organisms. GAGs contribute to biochemical pathway regulation, cell signaling, and disease progression. GAG sequence information is imperative for determining structure-function relationships. Recent advances in electron-activation techniques paired with high-resolution mass spectrometry allow for full sequencing of GAG structures. Electron detachment dissociation (EDD) and negative electron transfer dissociation (NETD) are two electron-activation methods that have been utilized for GAG characterization. Both methods produce an abundance of informative glycosidic and cross-ring fragment ions without producing a high degree of sulfate decomposition. Here, we provide detailed protocols for using EDD and NETD to sequence GAG chains. In addition to protocols directly involving performing these MS/MS methods, protocols include sample preparation, method development, internal calibration, and data analysis. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of glycosaminoglycan samples Basic Protocol 2: FTICR method development Basic Protocol 3: Internal calibration with NaTFA Basic Protocol 4: Electron Detachment Dissociation (EDD) of GAG samples Basic Protocol 5: Negative electron transfer dissociation (NETD) of GAG samples Basic Protocol 6: Analysis of MS/MS data.

Novel Flavivirus Attenuation Markers Identified in the Envelope Protein of Alfuy Virus

Alfuy (ALFV) is an attenuated flavivirus related to the Murray Valley encephalitis virus (MVEV). We previously identified markers of attenuation in the envelope (E) protein of the prototype strain (ALFV₃₉₂₉), including the hinge region (E273-277) and lack of glycosylation at E154-156. To further determine the mechanisms of attenuation we assessed ALFV₃₉₂₉ binding to glycosaminoglycans (GAG), a known mechanism of flaviviruses attenuation. Indeed, ALFV₃₉₂₉ exhibited reduced binding to GAG-rich cells in the presence of heparin; however, low-passage ALFV isolates were relatively unaffected. Sequence comparisons between ALFV strains and structural modelling incriminated a positively-charged residue (K327) in ALFV₃₉₂₉ as a GAG-binding motif. Substitution of this residue to the corresponding uncharged residue in MVEV (L), using a previously described chimeric virus containing the prM & E genes of ALFV₃₉₂₉ in the backbone of MVEV (MVEV/ALFV-prME), confirmed a role for K327 in enhanced GAG binding. When the wild type residues at E327, E273-277 and E154-156 of ALFV₃₉₂₉ were replaced with the corresponding residues from virulent MVEV, it revealed each motif contributed to attenuation of ALFV₃₉₂₉, with the E327/E273-277 combination most dominant. These data demonstrate that attenuation of ALFV₃₉₂₉ is multifactorial and provide new insights for the rational design of attenuated flavivirus vaccines.

Pediatric laryngotracheal reconstruction with tissue-engineered cartilage in a rabbit model

OBJECTIVES/HYPOTHESIS

To develop an effective rabbit model of in vitro- and in vivo-derived tissue-engineered cartilage for laryngotracheal reconstruction (LTR).

STUDY DESIGN

1) Determination of the optimal scaffold 1% hyaluronic acid (HA), 2% HA, and polyglycolic acid (PGA) and in vitro culture time course using a pilot study of 4 by 4-mm in vitro-derived constructs analyzed on a static culture versus zero-gravity bioreactor for 4, 8, and 12 weeks, with determination of compressive modulus and histology as outcome measures. 2) Three-stage survival rabbit experiment utilizing autologous auricular chondrocytes seeded in scaffolds, either 1% HA or PGA. The constructs were cultured for the determined in vitro time period and then cultured in vivo for 12 weeks. Fifteen LTRs were performed using HA cartilage constructs, and one was performed with a PGA construct. All remaining specimens and the final reconstructed larynx underwent mechanical testing, histology, and glycosaminoglycan (GAG) content determination, and then were compared to cricoid control specimens (n = 13) and control LTR using autologous thyroid cartilage (n = 18).

METHODS

1) One rabbit underwent an auricular punch biopsy, and its chondrocytes were isolated and expanded and then encapsulated in eight 4 by 4-mm discs of 1% HA, 2% HA, PGA either in rotary bioreactor or static culture for 4, 8, and 12 weeks, respectively, with determination of compressive modulus, GAG content, and histology. 2) Sixteen rabbits underwent ear punch biopsy; chondrocytes were isolated and expanded. The cells were seeded in 13 by 5 by 2.25-mm UV photopolymerized 1% HA (w/w) or calcium alginate encapsulated synthetic PGA (13 × 5 × 2 mm); the constructs were then incubated in vitro for 12 weeks (the optimal time period determined above in paragraph 1) on a shaker. One HA and one PGA construct from each animal was tested mechanically and histologically, and the remaining eight (4 HA and 4 PGA) were implanted in the neck. After 12 weeks in vivo, the most optimal-appearing HA construct was used as a graft for LTR in 15 rabbits and PGA in one rabbit. The seven remaining specimens underwent hematoxylin and eosin, Safranin O, GAG content determination, and flexural modulus testing. At 12 weeks postoperative, the animals were euthanized and underwent endoscopy. The larynges underwent mechanical and histological testing. All animals that died underwent postmortem examination, including gross and microhistological analysis of the reconstructed airway.

RESULTS

Thirteen of the 15 rabbits that underwent LTR with HA in vitro- and in vivo-derived tissue-engineered cartilage constructs survived. The 1% HA specimens had the highest modulus and GAG after 12 weeks in vitro. The HA constructs became well integrated in the airway, supported respiration for the 12 weeks, and were histologically and mechanically similar to autologous cartilage.

CONCLUSIONS

The engineering of in vitro- and in vivo-derived cartilage with HA is a novel approach for laryngotracheal reconstruction. The data suggests that the in vitro- and in vivo-derived tissue-engineered approaches may offer a promising alternative to current strategies used in pediatric airway reconstruction, as well as other head and neck applications.

LEVEL OF EVIDENCE

NA. Laryngoscope, 126:S5-S21, 2016.

Solution NMR characterization of chemokine CXCL8/IL-8 monomer and dimer binding to glycosaminoglycans: structural plasticity mediates differential binding interactions

Structural plasticity plays a major role in determining differential binding of CXCL8 monomer and dimer to glycosaminoglycans (GAGs) and that dimer is the high-affinity GAG ligand. We propose that these properties play important roles in orchestrating in vivo chemokine-mediated neutrophil function.

Chemokine CXCL8/interleukin-8 (IL-8) plays a crucial role in directing neutrophils and oligodendrocytes to combat infection/injury and tumour cells in metastasis development. CXCL8 exists as monomers and dimers and interaction of both forms with glycosaminoglycans (GAGs) mediate these diverse cellular processes. However, very little is known regarding the structural basis underlying CXCL8–GAG interactions. There are conflicting reports on the affinities, geometry and whether the monomer or dimer is the high-affinity GAG ligand. To resolve these issues, we characterized the binding of a series of heparin-derived oligosaccharides [heparin disaccharide (dp2), heparin tetrasaccharide (dp4), heparin octasaccharide (dp8) and heparin 14-mer (dp14)] to the wild-type (WT) dimer and a designed monomer using solution NMR spectroscopy. The pattern and extent of binding-induced chemical shift perturbation (CSP) varied between dimer and monomer and between longer and shorter oligosaccharides. NMR-based structural models show that different interaction modes coexist and that the nature of interactions varied between monomer and dimer and oligosaccharide length. MD simulations indicate that the binding interface is structurally plastic and provided residue-specific details of the dynamic nature of the binding interface. Binding studies carried out under conditions at which WT CXCL8 exists as monomers and dimers provide unambiguous evidence that the dimer is the high-affinity GAG ligand. Together, our data indicate that a set of core residues function as the major recognition/binding site, a set of peripheral residues define the various binding geometries and that the structural plasticity of the binding interface allows multiplicity of binding interactions. We conclude that structural plasticity most probably regulates in vivo CXCL8 monomer/dimer–GAG interactions and function.

Myrtol ameliorates cartilage lesions in an osteoarthritis rat model

PURPOSE

The aim of this study is to evaluate the effects of myrtol standardized on cartilage lesions in osteoarthritis (OA) rats.

METHODS

Fifty-six healthy Sprague-Dawley rats were randomly divided into sham group (13 rats) and OA model group (43 rats) with interior meniscus excision. Then serum estradiol (E2) and glycosaminoglycan (GAG) content in cartilage tissue were measured by radioimmunoassay and toluidine blue staining, respectively. After that, the model rats were randomly divided into low dose myrtol (LDM) group, middle dose myrtol (MDM) group and high dose myrtol (HDM) group (10 rats in each group) with treatment of 450 mg/kg, 300 mg/kg and 150 mg/kg myrtol, respectively. Then, Mankin scores were used to evaluate lesion extent of knee joint cartilage. Expression of tumor necrosis factor α (TNF-α), transforming growth factor β1 (TGF-β1), interleukin (IL)-6, Bax and Bcl-2 were investigated using PCR gel electrophoresis method.

RESULTS

Mankin cores were lower in sham group and myrtol group than in model group. There were statistically significant differences (P < 0.01) between sham group and model group in expression of TNF-α, TGF-β1, IL-6, Bax and Bcl-2 in the cartilage tissue. Myrtol significantly reduced the expression of TNF-α, IL-6 and Bax, and increased the expression of TGF-β1 and Bcl-2 in myrtol group, comparing with those in model group (P < 0.01).

CONCLUSIONS

Myrtol could down-regulate the expression of TNF-α, IL-6 and Bax, and up-regulate the expression of TGF-β1 and Bcl-2. Myrtol standardized is a promising drug to ameliorate knee cartilage lesions in the OA rat model.

Prevention of recurrent urinary tract infections by intravesical administration of heparin: a pilot study

OBJECTIVE

To assess the effect of bladder instillations using heparin on the rate of urinary tract infections in women resistant to standard therapy.

PATIENTS AND METHODS

The medical records of all women who received bladder instillations between May 2009 and January of 2010 at the University of Wisconsin urogynecology clinic were reviewed. Eighteen women (mean age 67 years) with a history of recurrent urinary tract infections received intravesical instillations (heparin 40,000 U, 2% lidocaine 8 ml, sodium bicarbonate 4 ml) once weekly for 6 weeks. Patients were considered resistant to standard therapy if their condition failed to respond to chronic suppression antibiotic therapy; they had chronic infections and for this reason could not be placed on chronic suppression; or they were not candidates for chronic suppression due to drug allergies. The number of urinary tract infections was monitored during treatment and for 6 months after therapy. The urinary tract infection rates were compared with the rates of urinary tract infection in the 6 months before treatment.

RESULTS

Seventy-eight percent of patients responded to therapy. Subjects were thought to have responded to therapy if there was a greater than 50% reduction in the rate of urinary tract infection. Other variables reviewed included evidence of chronic infection, hormonal status, glomerular filtration rate, age, body mass index, antibiotic allergies, diabetes, hypertension, and chronic antibiotic therapy during bladder instillations. None of these variables were found to be statistically significant.

CONCLUSION

Bladder instillations decreased the rate of urinary tract infection in this pilot study; this effect persisted into the post-treatment period. More research is needed to confirm these preliminary findings.

Chondrocyte spheroids on microfabricated PEG hydrogel surface and their noninvasive functional monitoring

A two-dimensional microarray of 10 000 (100 × 100) chondrocyte spheroids was constructed with a 100 μm spacing on a micropatterned gold electrode that was coated with poly(ethylene glycol) (PEG) hydrogels. The PEGylated surface as a cytophobic region was regulated by controlling the gel structure through photolithography. In this way, a PEG hydrogel was modulated enough to inhibit outgrowth of chondrocytes from a cell adhering region in the horizontal direction, which is critical for inducing formation of three-dimensional chondrocyte aggregations (spheroids) within 24 h. We further report noninvasive monitoring of the cellular functional change at the cell membrane using a chondrocyte-based field effect transistor. This measurement is based on detection of extracellular potential change induced as a result of the interaction between extracellular matrix protein secreted from spheroid and substrate at the cell membrane. The interface potential change at the cell membrane/gate interface can be monitored during the differentiation of spheroids without any labeling materials. Our measurements of the time evolution of the interface potential provide important information for understanding the uptake kinetics for cellular differentiation.