Glycosaminoglycan profiling in different cell types using infrared spectroscopy and imaging

Vibrational spectroscopy coupled with machine learning sheds light on the cellular effects induced by rationally designed TLR4 agonists

In this work, we present the potential of Fourier transform infrared (FTIR) microspectroscopy to compare on whole cells, in an unbiased and untargeted way, the capacity of bacterial lipopolysaccharide (LPS) and two rationally designed molecules (FP20 and FP20Rha) to activate molecular circuits of innate immunity. These compounds are important drug hits in the development of vaccine adjuvants and tumor immunotherapeutics. The biological assays indicated that FP20Rha was more potent than FP20 in inducing cytokine production in cells and in stimulating IgG antibody production post-vaccination in mice. Accordingly, the overall significant IR spectral changes induced by the treatment with LPS and FP20Rha were similar, lipids and glycans signals being the most diagnostic, while the effect of the less potent molecule FP20 on cells resulted to be closer to control untreated cells. We propose here the use of FTIR spectroscopy supported by artificial intelligence (AI) to achieve a more holistic understanding of the cell response to new drug candidates while screening them in cells.

In vitro assessment of antimicrobial potential of low molecular weight chitosan and its ability to mechanically reinforce and control endogenous proteolytic activity of dentine

AIMS

Chitosan-based biomaterials exhibit several properties of biological interest for endodontic treatment. Herein, a low molecular weight chitosan (CH) solution was tested for its antimicrobial activity against Enterococcus faecalis (E. faecalis) and effects on dentine structure.

METHODOLOGY

The root canal of 27 extracted uniradicular teeth were biomechanically prepared, inoculated with a suspension of E. faecalis and randomly assigned to be irrigated with either 5.25% sodium hypochlorite (NaClO), 0.2% CH or sterile ultrapure water (W). Bacteriologic samples were collected from root canals and quantified for of E. faecalis colony-forming units (CFUs). The effectiveness of CH over E. faecalis biofilms was further measured using the MBEC Assay®. Additionally, dentine beams and dentine powder were obtained, respectively, from crowns and roots of 20 extracted third molars. Dentine samples were treated or not with 17% EDTA and immersed in either CH or W for 1 min. The effects of CH on dentine structure were evaluated by assessment of the modulus of elasticity, endogenous proteolytic activity and biochemical modifications.

RESULTS

The number of E. faecalis CFUs was significantly lower for samples irrigated with CH and NaClO. No significant differences were found between CH and NaClO treatments. Higher modulus of elasticity and lower proteolytic activity were reported for dentine CH-treated specimens. Chemical interaction between CH and dentine was observed for samples treated or not with EDTA.

CONCLUSIONS

Present findings suggest that CH could be used as an irrigant during root canal treatment with the triple benefit of reducing bacterial activity, mechanically reinforcing dentine and inhibiting dentine proteolytic activity.

A Global Picture of Molecular Changes Associated to LPS Treatment in THP-1 Derived Human Macrophages by Fourier Transform Infrared Microspectroscopy

Macrophages are among the first immune cells involved in the initiation of the inflammatory response to protect the host from pathogens. THP-1 derived macrophages (TDM) are used as a model to study the pro-inflammatory effects of lipopolysaccharide (LPS) exposure. Intact TDM cells were analysed by Fourier transform infrared (FTIR) microspectroscopy, supported by multivariate analysis, to obtain a snapshot of the molecular events sparked by LPS stimulation in macrophage-like cells. This spectroscopic analysis enabled the untargeted identification of the most significant spectral components affected by the treatment, ascribable mainly to lipid, protein, and sulfated sugar bands, thus stressing the fundamental role of these classes of molecules in inflammation and in immune response. Our study, therefore, shows that FTIR microspectroscopy enabled the identification of spectroscopic markers of LPS stimulation and has the potential to become a tool to assess those global biochemical changes related to inflammatory and anti-inflammatory stimuli of synthetic and natural immunomodulators different from LPS.

Investigating the molecular structure of plasma in type 2 diabetes mellitus and diabetic nephropathy by synchrotron Fourier-transform infrared microspectroscopy

Diabetes mellitus (DM) is associated with a high incidence of morbidity and mortality which, in many cases, is derived from the progressive kidney dysfunction due to diabetic nephropathy (DN). In this study, synchrotron-Fourier-transform infrared (SR-FTIR) microspectroscopy was used to identify molecular changes in the lipid and protein regions in the plasma of patients with different stages of DN (mild, moderate, severe and end-stage), and patients with type 2 diabetes mellitus (T2DM) without DN. Our results revealed different conformational changes in the proteins secondary structure between DN stages, and between DN and T2DM groups illustrated by peak shifts and intensity alterations. End-stage DN showed the highest CH₂/CH₃ ratio and intensity of the carbonyl group in protein-carbonyl region compared to other DN stages indicating high level of unsaturation and lipid peroxidation and oxidation conditions. Moreover, end-stage DN group was characterized by a decrease in amide I and amide II absorption signals which reflected a sign of hypoalbuminemia. When compared to T2DM, DN group demonstrated a higher oxidation state as confirmed via the high intensity of the carbonyl group and the high level of malondialdehyde. The current study highlights the promising role of SR-FTIR microspectroscopy as a new sensitive analytical approach that can be used to provide better understanding of the pathophysiology of DN, and guide the development of new preventive therapies and treatments.

Ex Vivo Vibration Spectroscopic Analysis of Colorectal Polyps for the Early Diagnosis of Colorectal Carcinoma

Colorectal cancer is one of the most common and often fatal cancers in humans, but it has the highest chance of a cure if detected at an early precancerous stage. Carcinogenesis in the colon begins as an uncontrolled growth forming polyps. Some of these polyps can finally be converted to colon cancer. Early diagnosis of adenomatous polyps is the main approach for screening and preventing colorectal cancer, and vibration spectroscopy can be used for this purpose. This work is focused on evaluating FTIR and Raman spectroscopy as a tool in the ex vivo analysis of colorectal polyps, which could be important for the early diagnosis of colorectal carcinoma. Multivariate analyses (PCA and LDA) were used to assist the spectroscopic discrimination of normal colon tissue, as well as benign and malignant colon polyps. The spectra demonstrated evident differences in the characteristic bands of the main tissue constituents, i.e., proteins, nucleic acids, lipids, polysaccharides, etc. Suitable models for discriminating the three mentioned diagnostic groups were proposed based on multivariate analyses of the spectroscopic data. LDA classification was especially successful in the case of a combined set of 55 variables from the FTIR, FT Raman and dispersion Raman spectra. This model can be proposed for ex vivo colorectal cancer diagnostics in combination with the colonoscopic extraction of colon polyps for further testing. This pilot study is a precursor for the further evaluation of the diagnostic potential for the simultaneous in vivo application of colonoscopic Raman probes.

Hair Histology and Glycosaminoglycans Distribution Probed by Infrared Spectral Imaging: Focus on Heparan Sulfate Proteoglycan and Glypican-1 during Hair Growth Cycle

The expression of glypicans in different hair follicle (HF) compartments and their potential roles during hair shaft growth are still poorly understood. Heparan sulfate proteoglycan (HSPG) distribution in HFs is classically investigated by conventional histology, biochemical analysis, and immunohistochemistry. In this report, a novel approach is proposed to assess hair histology and HSPG distribution changes in HFs at different phases of the hair growth cycle using infrared spectral imaging (IRSI). The distribution of HSPGs in HFs was probed by IRSI using the absorption region relevant to sulfation as a spectral marker. The findings were supported by Western immunoblotting and immunohistochemistry assays focusing on the glypican-1 expression and distribution in HFs. This study demonstrates the capacity of IRSI to identify the different HF tissue structures and to highlight protein, proteoglycan (PG), glycosaminoglycan (GAG), and sulfated GAG distribution in these structures. The comparison between anagen, catagen, and telogen phases shows the qualitative and/or quantitative evolution of GAGs as supported by Western immunoblotting. Thus, IRSI can simultaneously reveal the location of proteins, PGs, GAGs, and sulfated GAGs in HFs in a reagent- and label-free manner. From a dermatological point of view, IRSI shows its potential as a promising technique to study alopecia.

Impact of extracellular matrix stiffness on genomic heterogeneity in MYCN-amplified neuroblastoma cell line

Background

Increased tissue stiffness is a common feature of malignant solid tumors, often associated with metastasis and poor patient outcomes. Vitronectin, as an extracellular matrix anchorage glycoprotein related to a stiff matrix, is present in a particularly increased quantity and specific distribution in high-risk neuroblastoma. Furthermore, as cells can sense and transform the proprieties of the extracellular matrix into chemical signals through mechanotransduction, genotypic changes related to stiffness are possible.

Methods

We applied high density SNPa and NGS techniques to in vivo and in vitro models (orthotropic xenograft vitronectin knock-out mice and 3D bioprinted hydrogels with different stiffness) using two representative neuroblastoma cell lines (the MYCN-amplified SK-N-BE(2) and the ALK-mutated SH-SY5Y), to discern how tumor genomics patterns and clonal heterogeneity of the two cell lines are affected.

Results

We describe a remarkable subclonal selection of genomic aberrations in SK-N-BE(2) cells grown in knock-out vitronectin xenograft mice that also emerged when cultured for long times in stiff hydrogels. In particular, we detected an enlarged subclonal cell population with chromosome 9 aberrations in both models. Similar abnormalities were found in human high-risk neuroblastoma with MYCN amplification. The genomics of the SH-SY5Y cell line remained stable when cultured in both models.

Conclusions

Focus on heterogeneous intratumor segmental chromosome aberrations and mutations, as a mirror image of tumor microenvironment, is a vital area of future research.

Infrared Microspectroscopy and Imaging Analysis of Inflammatory and Non-Inflammatory Breast Cancer Cells and Their GAG Secretome

Glycosaminoglycans (GAGs)/proteoglycans (PGs) play a pivotal role in the metastasis of inflammatory breast cancer (IBC). They represent biomarkers and targets in diagnosis and treatment of different cancers including breast cancer. Thus, GAGs/PGs could represent potential prognostic/diagnostic biomarkers for IBC. In the present study, non-IBC MDA-MB-231, MCF7, SKBR3 cells and IBC SUM149 cells, as well as their GAG secretome were analyzed. The latter was measured in toto as dried drops with high-throughput (HT) Fourier Transform InfraRed (FTIR) spectroscopy and imaging. FTIR imaging was also employed to investigate single whole breast cancer cells while synchrotron-FTIR microspectroscopy was used to specifically target their cytoplasms. Data were analyzed by hierarchical cluster analysis and principal components analysis. Results obtained from HT-FTIR analysis of GAG drops showed that the inter-group variability enabled us to delineate between cell types in the GAG absorption range 1350–800 cm⁻¹. Similar results were obtained for FTIR imaging of GAG extracts and fixed single whole cells. Synchrotron-FTIR data from cytoplasms allowed discrimination between non-IBC and IBC. Thus, by using GAG specific region, not only different breast cancer cell lines could be differentiated, but also non-IBC from IBC cells. This could be a potential diagnostic spectral marker for IBC detection useful for patient management.

HS2ST1-dependent signaling pathways determine breast cancer cell viability, matrix interactions, and invasive behavior

Heparan sulfate proteoglycans (HSPGs) act as signaling co‐receptors by interaction of their sulfated glycosaminoglycan chains with numerous signaling molecules. In breast cancer, the function of heparan sulfate 2‐O‐sulfotransferase (HS2ST1), the enzyme mediating 2‐O‐sulfation of HS, is largely unknown. Hence, a comparative study on the functional consequences of HS2ST1 overexpression and siRNA knockdown was performed in the breast cancer cell lines MCF‐7 and MDA‐MB‐231. HS2ST1 overexpression inhibited Matrigel invasion, while its knockdown reversed the phenotype. Likewise, cell motility and adhesion to fibronectin and laminin were affected by altered HS2ST1 expression. Phosphokinase array screening revealed a general decrease in signaling via multiple pathways. Fluorescent ligand binding studies revealed altered binding of fibroblast growth factor 2 (FGF‐2) to HS2ST1‐expressing cells compared with control cells. HS2ST1‐overexpressing cells showed reduced MAPK signaling responses to FGF‐2, and altered expression of epidermal growth factor receptor (EGFR), E‐cadherin, Wnt‐7a, and Tcf4. The increased viability of HS2ST1‐depleted cells was reduced to control levels by pharmacological MAPK pathway inhibition. Moreover, MAPK inhibitors generated a phenocopy of the HS2ST1‐dependent delay in scratch wound repair. In conclusion, HS2ST1 modulation of breast cancer cell invasiveness is a compound effect of altered E‐cadherin and EGFR expression, leading to altered signaling via MAPK and additional pathways.

Label-Free Infrared Spectral Histology of Skin Tissue Part II: Impact of a Lumican-Derived Peptide on Melanoma Growth

Melanoma is the most aggressive type of cutaneous malignancies. In addition to its role as a regulator of extracellular matrix (ECM) integrity, lumican, a small leucine-rich proteoglycan, also exhibits anti-tumor properties in melanoma. This work focuses on the use of infrared spectral imaging (IRSI) and histopathology (IRSH) to study the effect of lumican-derived peptide (L9Mc) on B16F1 melanoma primary tumor growth. Female C57BL/6 mice were injected with B16F1 cells treated with L9Mc (n = 10) or its scrambled peptide (n = 8), and without peptide (control, n = 9). The melanoma primary tumors were subjected to histological and IR imaging analysis. In addition, immunohistochemical staining was performed using anti-Ki-67 and anti-cleaved caspase-3 antibodies. The IR images were analyzed by common K-means clustering to obtain high-contrast IRSH that allowed identifying different ECM tissue regions from the epidermis to the tumor area, which correlated well with H&E staining. Furthermore, IRSH showed good correlation with immunostaining data obtained with anti-Ki-67 and anti-cleaved caspase-3 antibodies, whereby the L9Mc peptide inhibited cell proliferation and increased strongly apoptosis of B16F1 cells in this mouse model of melanoma primary tumors.

Investigating the molecular structure of placenta and plasma in pre-eclampsia by infrared microspectroscopy

Pre-eclampsia (PE) is a serious hypertensive disorder with unclear etiology and lack of reliable diagnostic tests. In this study, IR microspectroscopy was applied to identify molecular changes associated with the pathogenesis of PE in placental tissues and plasma samples from pre-eclamptic women and normotensive matched controls. The obtained spectra were analyzed by multivariate analysis in the spectral ranges of 3050-2800 cm^-1 and 1855-1485 cm^-1 corresponding to lipid and protein-carbonyl components, respectively. In the lipid region, an increase in CH₂/CH₃ ratio was noticed and higher level of unsaturation index in placenta was evident. New lipid species emerged as a consequence of oxidative stress. The more intense peak at 1740 cm^-1 in PE reflected higher level of LDL and VLDL. In the protein region, a decrease in the α-helix structure associated with gain in β-sheet and β-turn structures was detected. Our results revealed significant conformational changes in the protein secondary structure in PE illustrated by peak shifts and intensity alterations, particularly in amide I component. Variations in lipid order, membrane integrity, fatty acid saturation and plasma lipid profile were also detected in PE. The ROC curve generated from plasma samples yielded AUC values of 98.4% and 99.9% for lipid and protein-carbonyl regions, respectively. The current study shed light on the promising role of IR microspectroscopy as a new analytical tool that can aid in providing better diagnosis and understanding of the pathophysiology of PE.

Diagnosis of idiopathic amyotrophic lateral sclerosis using Fourier-transform infrared spectroscopic analysis of patient-derived skin

One of the great challenges in identifying effective therapy in many neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), is the lack of reliable biomarkers. In this study, we applied infrared imaging microspectroscopy, a valuable technique to investigate biomolecule fingerprints and secondary structure of proteins within biological tissue. We hypothesized that, since skin and CNS have the same embryonic origin, spectral differences associated with ALS-specific pathological events will be readily detectable through skin testing using this technique. Cells from healthy individuals and ALS patients were isolated from skin biopsies in order to generate tissue-engineered in vitro skin (TES). Infrared spectra of the generated TES were recorded using a focal-plane-array Fourier transform infrared (FPA-FTIR) spectrometer, and hierarchical cluster analysis of the spectral data was performed in order to establish clear differences between the tested TES specimens. Interestingly, our analyses showed that it was readily possible to discriminate ALS- and control-TES solely based on differences in associated FTIR spectra, mainly located between 1149 and 1473 cm^-1, attributed to disruption of phospholipid cell membranes, extracellular matrix remodeling or cholesterol accumulation. Spectral differences within the TES samples may therefore be associated with disease state, paving the way for the identification of biomarkers in ALS.

Glycosaminoglycans from Co-Products of «Scyliorhinus canicula»: Extraction and Purification in Reference to the European Pharmacopoeia Requirement

Background

Glycosaminoglycans (GAGs), including hyaluronic acid (HA), dermatan sulfate (DS) and chondroitin sulfate (CS) are essential components of the bone and cartilage tissues. CS isolated from the cartilage tissue of various animals has found application in pharmaceuticals, cosmetics and food industries. In the first part of the present work, three methods were used and compared to extract and purify glycosaminoglycans (GAGs) from the cartilage powder of a local cartilaginous marine species «Scyliorhinus canicula». One of these GAGs, chondroitin sulfate (CS), will be exploited for the development of an anti-osteoarthritis generic at the request of a collaborative pharmaceutical industry. Thus this active ingredient must meet the requirements and tests described by the European Pharmacopoeia (Ph. Eur.). These tests are treated in the second part of this work.

Results

Among the three methods that have been applied in the present work, in order to optimize the best process for GAGs preparation, enzymatic hydrolysis with papain followed by deproteinisation using trichloroacetic acid (TCA) was found the best one. The separation of the extracted GAGs using agarose gel electrophoresis, and the identification of bands by Fourier Transform Infrared (FT-IR) Spectroscopy, revealed that the cartilage GAGs of « Scyliorhinus canicula» are exclusively chondroitin sulfate (CS) and dermatane sulfate (DS), with proportions of 12.889 and 87.111% respectively, and that CS is of type C. The extraction technique with papain provides a product with GAGs content of around 90%. The TCA deproteinisation yielded the lowest level of protein (2.8%) in the extracted GAGs, less than 3%, which is the standard required by the European Pharmacopoeia (Ph. Eur.).Cetylpyridinium chloride (CPC) assay suggests that the titration technique, although is introduced by the Ph. Eur. for the determination of CS content, is not an accurate method, and that the values obtained by the optimized and validated HPLC method, described in this work, are more exact.

Conclusion

The extracted and purified active ingredient is perfectly conform to the tests described by the Ph. Eur. The results suggest that the co-product of Scyliorhinus canicula would be a perfect source of molecules of pharmacological interest, obtained by a simple and non-agressive process.

IR action spectroscopy of glycosaminoglycan oligosaccharides

Glycosaminoglycans (GAGs) are a physio- and pharmacologically highly relevant class of complex saccharides, possessing a linear sequence and strongly acidic character. Their repetitive linear core makes them seem structurally simple at first glance, yet differences in sulfation and epimerization lead to an enormous structural diversity with only a few GAGs having been successfully characterized to date. Recent infrared action spectroscopic experiments on sulfated mono- and disaccharide ions show great promise. Here, we assess the potential of two types of gas-phase action spectroscopy approaches in the range from 1000 to 1800 cm⁻¹ for the structural analysis of complex GAG oligosaccharides. Synthetic tetra- and pentasaccharides were chosen as model compounds for this benchmark study. Utilizing infrared multiple photon dissociation action spectroscopy at room temperature, diagnostic bands are largely unresolved. In contrast, cryogenic infrared action spectroscopy of ions trapped in helium nanodroplets yields resolved infrared spectra with diagnostic features for monosaccharide composition and sulfation pattern. The analysis of GAGs could therefore significantly benefit from expanding the conventional MS-based toolkit with gas-phase cryogenic IR spectroscopy.

ATR-FTIR Spectroscopy Supported by Multivariate Analysis for the Characterization of Adipose Tissue Aspirates from Patients Affected by Systemic Amyloidosis

Deposition of misfolded proteins as extracellular amyloid aggregates is the pathological hallmark of systemic amyloidoses. Subcutaneous fat acquired by fine needle aspiration is the preferred screening tissue in suspected patients. In this study we employed Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection (ATR) to investigate human abdominal fat aspirates with the aim of detecting disease-related changes in the molecular structure and composition of the tissue and exploiting the potentiality of the method to discriminate between amyloid-positive and -negative samples. The absorption and second-derivative spectra of Congo Red (CR) positive and CR-negative specimens were analyzed by three multivariate methods in four spectral regions. The proposed ATR-FTIR method is label-free, rapid, and relatively inexpensive and requires minimal sample preparation. We found that the ATR-FTIR approach can differentiate fat aspirates containing amyloid deposits from control specimens with high sensitivity and specificity, both at 100 [89-100]%. It is worth noting that the wavenumbers most important for discrimination indicate that changes both in the protein conformation and in resident lipids are intrinsic features of affected subcutaneous fat in comparison with the CR-negative controls. In this proof of concept study, we show that this approach could be useful for assessing tissue amyloid aggregates and for acquiring novel knowledge of the molecular bases of the disease.

Probing glycosaminoglycan spectral signatures in live cells and their conditioned media by Raman microspectroscopy

Spectroscopic markers characteristic of reference glycosaminoglycan molecules were identified previously based on their vibrational signatures. Infrared spectral signatures of glycosaminoglycans in fixed cells were also recently demonstrated but probing live cells still remains challenging. Raman microspectroscopy is potentially interesting to perform studies under physiological conditions. The aim of the present work was to identify the Raman spectral signatures of GAGs in fixed and live cells and in their conditioned media. Biochemical and Raman analyses were performed on five cell types: chondrocytes, dermal fibroblasts, melanoma (SK-MEL-28), wild type CHO, and glycosaminoglycan-defective mutant CHO-745 cells. The biochemical assay of sulfated GAGs in conditioned media was only possible for chondrocytes, dermal fibroblasts, and wild type CHO due to the detection limit of the test. In contrast, Raman microspectroscopy allowed probing total glycosaminoglycan content in conditioned media, fixed and live cells and the data were analysed by principal component analysis. Our results showed that the Raman technique is sensitive enough to identify spectral markers of glycosaminoglycans that were useful to characterise the conditioned media of the five cell types. The results were confirmed at the single cell level on both live and fixed cells with a good differentiation between the cell types. Furthermore, the principal component loadings revealed prominent glycosaminoglycan-related spectral information. Raman microspectroscopy allows monitoring of the glycosaminoglycan profiles of single live cells and could therefore be developed for cell screening purposes and holds promise for identifying glycosaminoglycan signatures as a marker of cancer progression in tissues.

Human Stem Cell-Derived Endothelial-Hepatic Platform for Efficacy Testing of Vascular-Protective Metabolites from Nutraceuticals

Atherosclerosis underlies many cardiovascular and cerebrovascular diseases. Nutraceuticals are emerging as a therapeutic moiety for restoring vascular health. Unlike small-molecule drugs, the complexity of ingredients in nutraceuticals often confounds evaluation of their efficacy in preclinical evaluation. It is recognized that the liver is a vital organ in processing complex compounds into bioactive metabolites. In this work, we developed a coculture system of human pluripotent stem cell-derived endothelial cells (hPSC-ECs) and human pluripotent stem cell-derived hepatocytes (hPSC-HEPs) for predicting vascular-protective effects of nutraceuticals. To validate our model, two compounds (quercetin and genistein), known to have anti-inflammatory effects on vasculatures, were selected. We found that both quercetin and genistein were ineffective at suppressing inflammatory activation by interleukin-1β owing to limited metabolic activity of hPSC-ECs. Conversely, hPSC-HEPs demonstrated metabolic capacity to break down both nutraceuticals into primary and secondary metabolites. When hPSC-HEPs were cocultured with hPSC-ECs to permit paracrine interactions, the continuous turnover of metabolites mitigated interleukin-1β stimulation on hPSC-ECs. We observed significant reductions in inflammatory gene expressions, nuclear translocation of nuclear factor κB, and interleukin-8 production. Thus, integration of hPSC-HEPs could accurately reproduce systemic effects involved in drug metabolism in vivo to unravel beneficial constituents in nutraceuticals. This physiologically relevant endothelial-hepatic platform would be a great resource in predicting the efficacy of complex nutraceuticals and mechanistic interrogation of vascular-targeting candidate compounds. Stem Cells Translational Medicine 2017;6:851-863.

Implementation of infrared and Raman modalities for glycosaminoglycan characterization in complex systems

Glycosaminoglycans (GAGs) are natural, linear and negatively charged heteropolysaccharides which are incident in every mammalian tissue. They consist of repeating disaccharide units, which are composed of either sulfated or non-sulfated monosaccharides. Depending on tissue types, GAGs exhibit structural heterogeneity such as the position and degree of sulfation or within their disaccharide units composition being heparin, heparan sulfate, chondroitine sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. They are covalently linked to a core protein (proteoglycans) or as free chains (hyaluronan). GAGs affect cell properties and functions either by direct interaction with cell receptors or by sequestration of growth factors. These evidences of divert biological roles of GAGs make their characterization at cell and tissue levels of importance. Thus, non-invasive techniques are interesting to investigate, to qualitatively and quantitatively characterize GAGs in vitro in order to use them as diagnostic biomarkers and/or as therapeutic targets in several human diseases including cancer. Infrared and Raman microspectroscopies and imaging are sensitive enough to differentiate and classify GAG types and subtypes in spite of their close molecular structures. Spectroscopic markers characteristic of reference GAG molecules were identified. Beyond these investigations of the standard GAG spectral signature, infrared and Raman spectral signatures of GAG were searched in complex biological systems like cells. The aim of the present review is to describe the implementation of these complementary vibrational spectroscopy techniques, and to discuss their potentials, advantages and disadvantages for GAG analysis. In addition, this review presents new data as we show for the first time GAG infrared and Raman spectral signatures from conditioned media and live cells, respectively.

Glycosaminoglycanomics: where we are

Glycosaminoglycans regulate numerous physiopathological processes such as development, angiogenesis, innate immunity, cancer and neurodegenerative diseases. Cell surface GAGs are involved in cell-cell and cell-matrix interactions, cell adhesion and signaling, and host-pathogen interactions. GAGs contribute to the assembly of the extracellular matrix and heparan sulfate chains are able to sequester growth factors in the ECM. Their biological activities are regulated by their interactions with proteins. The structural heterogeneity of GAGs, mostly due to chemical modifications occurring during and after their synthesis, makes the development of analytical techniques for their profiling in cells, tissues, and biological fluids, and of computational tools for mining GAG-protein interaction data very challenging. We give here an overview of the experimental approaches used in glycosaminoglycomics, of the major GAG-protein interactomes characterized so far, and of the computational tools and databases available to analyze and store GAG structures and interactions.

In situ characterization of protein aggregates in human tissues affected by light chain amyloidosis: a FTIR microspectroscopy study

Light chain (AL) amyloidosis, caused by deposition of amyloidogenic immunoglobulin light chains (LCs), is the most common systemic form in industrialized countries. Still open questions, and premises for developing targeted therapies, concern the mechanisms of amyloid formation in vivo and the bases of organ targeting and dysfunction. Investigating amyloid material in its natural environment is crucial to obtain new insights on the molecular features of fibrillar deposits at individual level. To this aim, we used Fourier transform infrared (FTIR) microspectroscopy for studying in situ unfixed tissues (heart and subcutaneous abdominal fat) from patients affected by AL amyloidosis. We compared the infrared response of affected tissues with that of ex vivo and in vitro fibrils obtained from the pathogenic LC derived from one patient, as well as with that of non amyloid-affected tissues. We demonstrated that the IR marker band of intermolecular β-sheets, typical of protein aggregates, can be detected in situ in LC amyloid-affected tissues, and that FTIR microspectroscopy allows exploring the inter- and intra-sample heterogeneity. We extended the infrared analysis to the characterization of other biomolecules embedded within the amyloid deposits, finding an IR pattern that discloses a possible role of lipids, collagen and glycosaminoglycans in amyloid deposition in vivo.