Fourier transform infrared spectroscopic imaging of cardiac tissue to detect collagen deposition after myocardial infarction

Corneal Wound Healing in the Presence of Antifibrotic Antibody Targeting Collagen Fibrillogenesis: A Pilot Study

Highly organized collagen fibrils interlacing with proteoglycans form the crucial architecture of the cornea and facilitate its transparency. Corneal scarring from accidental injury, surgery, or infection alters this highly organized tissue, causing severe consequences, including blindness. There are no pharmacological or surgical methods to effectively and safely treat excessive corneal scarring. Thus, we tested the anticorneal scarring utility of a rationally designed anticollagen antibody (ACA) whose antifibrotic effects have already been demonstrated in nonocular models. Utilizing a rabbit model with an incisional corneal wound, we analyzed ACA's effects on forming collagen and proteoglycan-rich extracellular matrices in scar neotissue. We used microscopic and spectroscopic techniques to quantify these components and measure crucial parameters characterizing the structure and organization of collagen fibrils. Moreover, we analyzed the spatial distribution of collagen and proteoglycans in normal and healing corneas. Our study demonstrated significant changes in the quality and quantity of the analyzed molecules synthesized in scar neotissue. It showed that these changes extend beyond incision margins. It also showed ACA's positive impact on some crucial parameters defining proper cornea structure. This pilot study provides a stepping stone for future tests of therapeutic approaches that target corneal extracellular scar matrix assembly.

Scar formation in the presence of mitomycin C and the anti-fibrotic antibody in a rabbit model of glaucoma microsurgery: A pilot study

Purpose

This study aimed to evaluate the utility of a rationally engineered antibody that directly blocks collagen fibrillogenesis to reduce scar tissue formation associated with subconjunctival glaucoma surgery.

Material and methods

Fourteen eyes of 7 adult rabbits underwent glaucoma filtering surgery using XEN 45 Gel Stent. The rabbits' eyes were divided randomly into three treatment groups: (i) treated with the antibody, (ii) treated with mitomycin C, and (iii) treated with the antibody and mitomycin C. Following surgeries, the intraocular pressure and bleb appearance were evaluated in vivo. The rabbits were sacrificed 8 weeks after the surgery, and their eyes were harvested and processed for tissue analysis. Subsequently, tissue samples were analyzed microscopically for fibrotic tissue and cellular markers of inflammation. Moreover, the collagen-rich fibrotic tissue formed around the stents was analyzed using quantitative histology and infrared spectroscopy. The outcomes of this study were analyzed using the ANOVA test.

Results

This study demonstrated no significant differences in intraocular pressure, bleb appearance, or presence of complications such as bleb leak among the treatment groups. In contrast, we observed significant differences among the subpopulations of collagen fibrils formed within scar neo-tissue. Based on the spectroscopic analyses, we determined that the relative content of mature collagen cross-links in the antibody-treated group was significantly reduced compared to other groups.

Conclusions

Direct blocking of collagen fibrillogenesis with the anti-collagen antibody offers potentially beneficial effects that may reduce the negative impact of the subconjunctival scarring associated with glaucoma filtering surgery.

Infrared Spectroscopic Verification of a α-Helical Collagen Structure in Glutaraldehyde-Free Crosslinked Bovine Pericardium for Cardiac Implants

The degeneration of heart valve bioprostheses due to calcification processes is caused by the intercalation of calciumhydroxyapatite in pericardium collagen bundles. Variations of the protein secondary structure of biomaterials according to preparation are relevant for this mineralization process and thus the structural characterization of innovative bioprostheses materials is of great importance. The gold standard for prostheses preparation is glutaraldehyde (GA)-fixation of bovine pericardium that adversely promotes calcification. The novel GA-free SULEEI-treatment of bovine pericardium includes decellularization, UV-crosslinking, and electron beam sterilization. The aim of this study is the structural characterization of SULEEI-treated and GA-fixed bovine pericardium. IR spectroscopic imaging combined with multivariate data and curve fit analysis was applied to investigate the amide I and amide II regions of SULEEI-treated and GA-fixed samples. The spectroscopic images of GA-fixed pericardial tissue exhibited a generally high content of amine groups and side chains providing nucleation points for calcification processes. In contrast, in SULEEI-treated tissue, the typical α-helical structure was retained and was supposed to be less prone to deterioration.

N, Adigal S, Lukose J, Kartha VB, Chidangil S. Cardiovascular biomarkers in body fluids: progress and prospects in optical sensors

Cardiovascular diseases (CVD) are the major causative factors for high mortality and morbidity in developing and developed nations. The biomarker detection plays a crucial role in the early diagnosis of several non-infectious and life-threatening diseases like CVD and many cancers, which in turn will help in more successful therapy, reducing the mortality rate. Biomarkers have diagnostic, prognostic and therapeutic significances. The search for novel biomarkers using proteomics, bio-sensing, micro-fluidics, and spectroscopic techniques with good sensitivity and specificity for CVD is progressing rapidly at present, in addition to the use of gold standard biomarkers like troponin. This review is dealing with the current progress and prospects in biomarker research for the diagnosis of cardiovascular diseases.

Expert opinion.

Fast diagnosis of cardiovascular diseases (CVDs) can help to provide rapid medical intervention, which can affect the patient’s short and long-term health. Identification and detection of proper biomarkers for early diagnosis are crucial for successful therapy and prognosis of CVDs. The present review discusses the analysis of clinical samples such as whole blood, blood serum, and other body fluids using techniques like high-performance liquid chromatography-LASER/LED-induced fluorescence, Raman spectroscopy, mainly, optical methods, combined with nanotechnology and micro-fluidic technologies, to probe patterns of multiple markers (marker signatures) as compared to conventional techniques.

Uterine leiomyoma as useful model to unveil morphometric and macromolecular collagen state and impairment in fibrotic diseases: An ex-vivo human study

Collagen is one of the main components of the extracellular matrix (ECM), involved, among all, in the maintenance of the structural support of tissues. In fibrotic diseases, collagen is overexpressed, and its production determines the formation of a significantly stiffer ECM. The cross-linking of high-resolution analytical tools, able to investigate both the tridimensional organization and the secondary structure of collagen in fibrotic diseases, could be useful to identify defined markers correlating the status of this protein with specific pathological conditions. To this purpose, an innovative multidisciplinary approach based on Phase-Contrast MicroComputed Tomography, Transmission Electron Microscopy, and Fourier Transform Infrared Imaging Spectroscopy was exploited on leiomyoma samples and adjacent myometrium to characterize microstructural collagen features. Uterine leiomyoma is a common gynecological disorder affecting women in fertile age. It is characterized by a massive collagen production due to the repairing processes occurring at myometrium level, and, hence, it represents a valuable model to investigate collagen self-organization in a pathological condition. Moreover, to evaluate the sensitivity of this multidisciplinary approach, the effects of eicosapentaenoic (EPA) and docosahexaenoic (DHA) omega-3 fatty acids in collagen reduction were also investigated.

Non/mini-invasive monitoring of diabetes-induced myocardial damage by Fourier transform infrared spectroscopy: Evidence from biofluids

Early identification of diabetic cardiomyopathy (DCM) can help clinicians develop targeted treatment plans and forensic pathologists make accurate postmortem diagnoses. In the present study, diabetes-induced metabolic abnormalities in the myocardium and biofluids (plasma, urine, and saliva) of db/db mice of various ages (7, 12, and 21 weeks) were investigated by attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy. The results indicated that the diabetic and control groups had significantly different changes in the function groups of lipids, phosphate macromolecules (mostly nucleic acids), protein compositions and conformations, and carbohydrates (primarily glucose) in the myocardium and biofluids. The prediction model for quantifying DCM severity was developed on db/db mice's myocardial spectra using a genetic algorithm (GA)-partial least squares (PLS) regression method. Following that, the linear correlations between the predicted values for DCM severity and spectra for db/db biofluids were evaluated using the GA-PLS regression algorithm. The results showed there were good linear correlations between the predicted values for DCM severity and spectra for plasma (R² = 0.929), saliva (R² = 0.967), urine (R² = 0.954), and combination of plasma and saliva (R² = 0.980). This study provides a novel perspective on detecting diabetes-related biofluid and cardiac metabolic abnormalities and demonstrates the potential of biofluid infrared spectro-diagnostic models for non/mini-invasive assessment of DCM.

Development and preliminary validation of infrared spectroscopic device for transdermal assessment of elevated cardiac troponin

Background

The levels of circulating troponin are principally required in addition to electrocardiograms for the effective diagnosis of acute coronary syndrome. Current standard-of-care troponin assays provide a snapshot or momentary view of the levels due to the requirement of a blood draw. This modality further restricts the number of measurements given the clinical context of the patient. In this communication, we present the development and early validation of non-invasive transdermal monitoring of cardiac troponin-I to detect its elevated state.

Methods

Our device relies on infrared spectroscopic detection of troponin-I through the dermis and is tested in stepwise laboratory, benchtop, and clinical studies. Patients were recruited with suspected acute coronary syndrome.

Results

We demonstrate a significant correlation (r = 0.7774, P < 0.001, n = 52 biologically independent samples) between optically-derived data and blood-based immunoassay measurements with and an area under receiver operator characteristics of 0.895, sensitivity of 96.3%, and specificity of 60% for predicting a clinically meaningful threshold for defining elevated Troponin I.

Conclusion

This preliminary work introduces the potential of a bloodless transdermal measurement of troponin-I based on molecular spectroscopy. Further, potential pitfalls associated with infrared spectroscopic mode of inquiry are outlined including requisite steps needed for improving the precision and overall diagnostic value of the device in future studies.

The number one cause of death in the US is heart disease. With 10 million patients visiting the emergency departments in a year with chest pain, 8 million are unrelated to cardiac issues. This places a burden on hospitals leading to suboptimal patient outcomes. In patients with cardiac issues, the time clinicians take to intervene dictates reversible or irreversible heart damage. However, current markers used to test for cardiac issues require blood sampling, limiting access to and frequency of testing. This study introduces a non-invasive cardiac marker measurement device without any form of blood draw, based on measurements taken by a wearable device through the skin. Preliminary studies show high conformance to the standard of care technologies, indicating that the technology has potential to enable more rapid, frequent, accessible and non-invasive detection of cardiac issues such as heart attacks.

Titus et al. develop a technological platform for the non-invasive transdermal measurement of cardiac troponin-I, a marker of myocardial injury. Preliminary testing of their device, which works via infrared spectroscopy, indicates that troponin can be detected with reasonable performance, in the absence of a blood draw.

Identification of myocardial fibrosis by ATR-FTIR spectroscopy combined with chemometrics

Different degrees of myocardial fibrosis can often be observed in sudden cardiac death cases, so that the identification of myocardial fibrosis is an important step in forensics to identify cardiac death. Previous methods are restricted by complex algorithms, high cost, low sensitivity and high requirements. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is an efficient and rapid method to identify tissue types, which has been used increasingly in forensics. This study aims to identify novel biophysical biomarkers of myocardial fibrosis and establish a prediction model by using ATR-FTIR analysis combined with chemometrics. A total of 129 tissue blocks taken from human hearts were cut into slices, and then ATR-FTIR spectroscopy and hematoxylin and eosin (HE) staining were performed. By using HE staining, the samples were divided into the experimental group (with myocardial fibrosis) and the control group (without myocardial fibrosis). The chemometrics classification results showed that the sensitivity and specificity of the training dataset were 0.91 and 1.0 respectively, and the sensitivity and specificity of the predictive dataset were 0.862 and 0.900. This study demonstrated that ATR-FTIR spectroscopy combined with chemometrics is a novel method for identifying myocardial fibrosis.

Identification of remodeled collagen fibers in tumor stroma by FTIR Micro-spectroscopy: A new approach to recognize the colon carcinoma

The tumor stroma plays a pivotal role in colon cancer genesis and progression. It was observed that collagen fibers in the extracellular matrix (ECM) of cancer stroma, undergo a strong remodeling. These fibrous proteins result more aligned and compact than in physiological conditions, creating a microenvironment that favors cancer development. In this work, micro-FTIR spectroscopy was applied to investigate the chemical modifications in the tumor stroma. Using Fuzzy C-means clustering, mean spectra from diseased and normal stroma were compared and collagen was found to be responsible for the main differences between them. Specifically, the modified absorptions at 1203, 1238, 1284 cm^-1 and 1338 cm^-1 wavenumbers, were related to the amide III band and CH₂ bending of side chains. These signals are sensitive to the interactions between the α-chains in the triple helices of collagen structure. This provided robust chemical evidence that in cancer ECM, collagen fibers are more parallelized, stiff and ordered than in normal tissue. Principal Component Analysis (PCA) applied to the spectra from malignant and normal stroma confirmed these findings. Using LDA (Linear Discriminant Analysis) classification, the absorptions 1203, 1238, 1284 and 1338 cm^-1 were examined as spectral biomarkers, obtaining quite promising results. The use of a PCA-LDA prediction model on samples with moderate tumor degree further showed that the stroma chemical modifications are more indicative of malignancy compared to the epithelium. These preliminary findings have shown that micro-FTIR spectroscopy, focused on collagen signals, could become a promising tool for colon cancer diagnosis.

Mechanisms of reducing joint stiffness by blocking collagen fibrillogenesis in a rabbit model of posttraumatic arthrofibrosis

Posttraumatic fibrotic scarring is a significant medical problem that alters the proper functioning of injured tissues. Current methods to reduce posttraumatic fibrosis rely on anti-inflammatory and anti-proliferative agents with broad intracellular targets. As a result, their use is not fully effective and may cause unwanted side effects. Our group previously demonstrated that extracellular collagen fibrillogenesis is a valid and specific target to reduce collagen-rich scar buildup. Our previous studies showed that a rationally designed antibody that binds the C-terminal telopeptide of the α2(I) chain involved in the aggregation of collagen molecules limits fibril assembly in vitro and reduces scar formation in vivo. Here, we have utilized a clinically relevant arthrofibrosis model to study the broad mechanisms of the anti-scarring activity of this antibody. Moreover, we analyzed the effects of targeting collagen fibril formation on the quality of healed joint tissues, including the posterior capsule, patellar tendon, and subchondral bone. Our results show that blocking collagen fibrillogenesis not only reduces collagen content in the scar, but also accelerates the remodeling of healing tissues and changes the collagen fibrils’ cross-linking. In total, this study demonstrated that targeting collagen fibrillogenesis to limit arthrofibrosis affects neither the quality of healing of the joint tissues nor disturbs vital tissues and organs.

Infrared spectroscopic imaging study of BV-2 microglia altering tumor cell biological activity and cellular fraction

Tumor brain metastasis is a severe threat to patients' neurological function, in which microglia may be involved in the process of tumor cell metastasis among nerve cells. Our study focused on the interaction between microglia and breast and lung cancer cells. Changes in the proliferation and migration ability of cocultured tumor cells were examined; synchrotron radiation-based fourier transform infrared microspectroscopy (SR-FTIR) was used to detect changes in the structures and contents of biomolecules within the tumor cells. The experimental results showed that the proliferation and migration ability of tumor cells increased after coculture, and the structures and contents of biological macromolecules in tumor cells changed. The absorption peak positions of the amide Ⅱ and amide Ⅰ bands observed for the four kinds of tumor cells changed, and the absorption intensities were significantly enhanced, indicating changes in the secondary structures and contents of proteins in tumor cells, which may be the root cause of the change in tumor cell characteristics. Therefore, the metabolites of microglia may be involved in the progression of tumor cells in the nervous system. In this study, we focused on the interaction between microglia and tumor cells by using SR-FTIR and provided a new understanding of the mechanism of brain metastasis.

Detection and Quantification of Myocardial Fibrosis Using Stain-Free Infrared Spectroscopic Imaging

CONTEXT.—

Myocardial fibrosis underpins a number of cardiovascular conditions and is difficult to identify with standard histologic techniques. Challenges include imaging, defining an objective threshold for classifying fibrosis as mild or severe, as well as understanding the molecular basis for these changes.

OBJECTIVE.—

To develop a novel, rapid, label-free approach to accurately measure and quantify the extent of fibrosis in cardiac tissue using infrared spectroscopic imaging.

DESIGN.—

We performed infrared spectroscopic imaging and combined that with advanced machine learning-based algorithms to assess fibrosis in 15 samples from patients belonging to the following 3 classes: (1) nonpathologic (control) donor hearts; (2) patients receiving transplant; and (3) tissue from patients undergoing implantation of ventricular assist device.

RESULTS.—

Our results show excellent sensitivity and accuracy for detecting myocardial fibrosis as demonstrated by high area under the curve of 0.998 in the receiver-operating characteristic curve measured from infrared imaging. Fibrosis of various morphologic subtypes are then demonstrated with virtually generated picrosirius red images, which show good visual and quantitative agreement (correlation coefficient = 0.92, ρ = 7.76 × 10-15) with stained images of the same sections. Underlying molecular composition of the different subtypes were investigated with infrared spectra showing reproducible differences presumably arising from differences in collagen subtypes and/or crosslinking.

CONCLUSIONS.—

Infrared imaging can be a powerful tool in studying myocardial fibrosis and gleaning insights into the underlying chemical changes that accompany it. Emerging methods suggest that the proposed approach is compatible with conventional optical microscopy and its consistency makes it translatable to the clinical setting for real-time diagnoses as well as for objective and quantitative research.

Tailoring the assembly of collagen fibers in alginate microspheres

The application of microspheres instead of bulk hydrogels in cell-laden biomaterials offers multiple advantages such as a high surface-to-volume-ratio and, consequently, a better nutrition and oxygen transfer to and from cells. The preparation of inert alginate microspheres is facile, quick, and well-established and the fabrication of alginate-collagen microspheres has been previously reported. However, no detailed characterization of the collagen fibrillogenesis in the alginate matrix is available. We use second-harmonic imaging microscopy reflection confocal microscopy and turbidity assay to study the assembly of collagen in alginate microspheres. We show that the assembly of collagen fibers in a gelled alginate matrix is a complex process that can be aided by addition of small polar molecules, such as glycine and by a careful selection of the gelling buffer used to prepare alginate hydrogels.

Biophysical and Lipidomic Biomarkers of Cardiac Remodeling Post-Myocardial Infarction in Humans

Few studies have analyzed the potential of biophysical parameters as markers of cardiac remodeling post-myocardial infarction (MI), particularly in human hearts. Fourier transform infrared spectroscopy (FTIR) illustrates the overall changes in proteins, nucleic acids and lipids in a single signature. The aim of this work was to define the FTIR and lipidomic pattern for human left ventricular remodeling post-MI. A total of nine explanted hearts from ischemic cardiomyopathy patients were collected. Samples from the right ventricle (RV), left ventricle (LV) and infarcted left ventricle (LV INF) were subjected to biophysical (FTIR and differential scanning calorimetry, DSC) and lipidomic (liquid chromatography-high-resolution mass spectrometry, LC-HRMS) studies. FTIR evidenced deep alterations in the myofibers, extracellular matrix proteins, and the hydric response of the LV INF compared to the RV or LV from the same subject. The lipid and esterified lipid FTIR bands were enhanced in LV INF, and both lipid indicators were tightly and positively correlated with remodeling markers such as collagen, lactate, polysaccharides, and glycogen in these samples. Lipidomic analysis revealed an increase in several species of sphingomyelin (SM), hexosylceramide (HexCer), and cholesteryl esters combined with a decrease in glycerophospholipids in the infarcted tissue. Our results validate FTIR indicators and several species of lipids as useful markers of left ventricular remodeling post-MI in humans.

Orientation Matters: Polarization Dependent IR Spectroscopy of Collagen from Intact Tendon Down to the Single Fibril Level

Infrared (IR) spectroscopy has been used for decades to study collagen in mammalian tissues. While many changes in the spectral profiles appear under polarized IR light, the absorption bands are naturally broad because of tissue heterogeneity. A better understanding of the spectra of ordered collagen will aid in the evaluation of disorder in damaged collagen and in scar tissue. To that end, collagen spectra have been acquired with polarized far-field (FF) Fourier Transform Infrared (FTIR) imaging with a Focal Plane Array detector, with the relatively new method of FF optical photothermal IR (O-PTIR), and with nano-FTIR spectroscopy based on scattering-type scanning near-field optical microscopy (s-SNOM). The FF methods were applied to sections of intact tendon with fibers aligned parallel and perpendicular to the polarized light. The O-PTIR and nano-FTIR methods were applied to individual fibrils of 100–500 nm diameter, yielding the first confirmatory and complementary results on a biopolymer. We observed that the Amide I and II bands from the fibrils were narrower than those from the intact tendon, and that both relative intensities and band shapes were altered. These spectra represent reliable profiles for normal collagen type I fibrils of this dimension, under polarized IR light, and can serve as a benchmark for the study of collagenous tissues.

The role of organic phosphate in the spatial control of periodontium complex bio-mineralization: an in vitro study

The periodontal structure is a particularly exquisite model of hierarchical spatial control of mineralization. Extracellular matrix control in the selective mineralization of the periodontium complex remains elusive since the extracellular matrix is a set of mineralization promoters and inhibitors. The phosphorylated proteins, which are ubiquitous in the extracellular matrix of the periodontium complex, are well-documented as primary factors in the regulation of tissue mineralization. Whether organic phosphates are key regulators in defining the interfaces between dentin, cementum, periodontal ligament and alveolar bone is an issue worthy of research. Here, we investigated the in vitro remineralization process of demineralized and dephosphorylated periodontal tissue sections. When exposed to a metastable mineralization solution, a large number of calcospherulites deposited on the surface of the dephosphorylated sections and the tissue selective mineralization were disrupted. Interestingly, on adding a dentin matrix protein-1 analogue named polyacrylic acid, the surface mineralization rate in the dephosphorylated periodontal complex reduced dramatically. In contrast, hierarchical mineralization was displayed by the demineralized section at the tissue collagen fibrillar levels in both alveolar bone and dentin regions. These results demonstrated that the organic phosphate could prevent surface mineral deposition, and the minerals could penetrate the collagen fibrils to initiate a selective and hierarchal tissue mineralization with the assistance of the dentin matrix protein-1 analogue in the periodontal complex. This study enhances our understanding of the mineralization discrepancy in the periodontal tissues, which will provide some insight into the development of biomaterials for the regeneration of soft-hard tissue interfaces.

Engineering Tissue Fabrication With Machine Intelligence: Generating a Blueprint for Regeneration

Regenerating lost or damaged tissue is the primary goal of Tissue Engineering. 3D bioprinting technologies have been widely applied in many research areas of tissue regeneration and disease modeling with unprecedented spatial resolution and tissue-like complexity. However, the extraction of tissue architecture and the generation of high-resolution blueprints are challenging tasks for tissue regeneration. Traditionally, such spatial information is obtained from a collection of microscopic images and then combined together to visualize regions of interest. To fabricate such engineered tissues, rendered microscopic images are transformed to code to inform a 3D bioprinting process. If this process is augmented with data-driven approaches and streamlined with machine intelligence, identification of an optimal blueprint can become an achievable task for functional tissue regeneration. In this review, our perspective is guided by an emerging paradigm to generate a blueprint for regeneration with machine intelligence. First, we reviewed recent articles with respect to our perspective for machine intelligence-driven information retrieval and fabrication. After briefly introducing recent trends in information retrieval methods from publicly available data, our discussion is focused on recent works that use machine intelligence to discover tissue architectures from imaging and spectral data. Then, our focus is on utilizing optimization approaches to increase print fidelity and enhance biomimicry with machine learning (ML) strategies to acquire a blueprint ready for 3D bioprinting.

Reliability of Histopathology for the Early Recognition of Fibrosis in Traction Alopecia: Correlation with Clinical Severity

Traction alopecia (TA) is hair loss caused by prolonged pulling or repetitive tension on scalp hair; it belongs to the biphasic group of primary alopecia. It is non-scarring, typically with preservation of follicular stem cells and the potential for regrowth of early lesions especially if traction hairstyles are stopped. However, the alopecia may become permanent (scarring) and fail to respond to treatment if the traction is excessive and prolonged. Hence, the ability to detect fibrosis early in these lesions could predict patients who respond to treatment. Histopathological diagnosis based on scalp biopsies has been used as a gold standard to delineate various forms of non-scarring alopecia and to differentiate them from scarring ones. However, due to potential discrepant reporting as a result of the type of biopsy, method of sectioning, and site of biopsy, histopathology often tends to be unreliable for the early recognition of fibrosis in TA. In this study, 45 patients were assessed using the marginal TA severity scoring system, and their biopsies (both longitudinal and transverse sections) were systematically assessed by three dermatopathologists, the aim being to correlate histopathological findings with clinical staging. Intraclass correlation coefficients were used to determine the level of agreement between the assessors. We found poor agreement of the identification and grading of perifollicular and interfollicular fibrosis (0.55 [0.23–0.75] and 0.01 [2.20–0.41], respectively), and no correlation could be drawn with the clinical severity score. Better methods of diagnosis are needed for grading and for recognition of early fibrosis in TA.

Histochemical quantification of collagen content in articular cartilage

Background

Articular cartilage (AC) is mainly composed of water, type II collagen, proteoglycans (PGs) and chondrocytes. The amount of PGs in AC is routinely quantified with digital densitometry (DD) from Safranin O-stained sections, but it is unclear whether similar method could be used for collagens.

Objective

The aim of this study was to clarify whether collagens can be quantified from histological AC sections using DD.

Material and methods

Sixteen human AC samples were stained with Masson’s trichrome or Picrosirius red. Optical densities of histological stains were compared to two commonly used collagen parameters (amide I and collagen CH₂ side chain peak at 1338cm^-1) measured using Fourier Transform Infrared (FTIR) spectroscopic imaging.

Results

Optical density of Modified Masson’s trichrome staining, which included enzymatic removal of PGs before staining, correlated significantly with FTIR-derived collagen parameters at almost all depths of cartilage. The other studied staining protocols displayed significant correlations with the reference parameters at only few depth layers.

Conclusions

Based on our findings, modified Masson’s trichrome staining protocol is suitable for quantification of AC collagen content. Enzymatic removal of PGs prior to staining is critical as us allows better staining of the collagen. Further optimization of staining protocols may improve the results in the future studies.

Fourier transform infrared spectroscopy based spectral biomarkers of metastasized breast cancer progression

Breast cancer is a global health issue and the second leading cause of cancer death in women. Breast cancer tends to migrate to bone and causes bone metastases which is ultimately the cause of death. Here, we report the use of FTIR to identify spectral biomarkers of cancer progression on 3D in vitro model of breast cancer bone metastasis. Our results indicate that the following spectral biomarkers can monitor cancer progression, for example, lipids (CH2 asymmetric/CH2 symmetric stretch), Amide I/Amide II, and RNA/DNA. Principal component analysis also confirmed the involvement of protein, lipids and nucleic acids in cancer progression on sequential culture. The collective observations from this study suggest successful application of FTIR as a non-invasive and accurate method to identify biochemical changes in cancer cells during the progression of breast cancer bone metastasis.

A protocol for rapid, label-free histochemical imaging of fibrotic liver

Mid-infrared microscopy is a non-destructive, quantitative and label-free spectroscopic imaging technique that, as a result of recent instrument advancements, is now at the point of enabling high-throughput automated biochemical screening of whole histology samples. Currently the mid-infrared field is undergoing a paradigm shift that has not been seen since the introduction of scanning Fourier Transform interferometric spectrometers. The latest mid-infrared microscopes are powered by tunable quantum cascade laser (QCL) sources which offer a number of advantages including measurement protocol flexibility, ease-of-use and a greatly enhanced data acquisition speed at high spectral and spatial resolution. In this study we use a wide-field QCL infrared microscope to develop and validate a fast four-frequency protocol for imaging fibrosis in unstained liver tissue. We compare our results to the gold standard Masson's trichrome histochemical staining protocol.

Identification of new biophysical markers for pathological ventricular remodelling in tachycardia-induced dilated cardiomyopathy

Our aim was to identify biophysical biomarkers of ventricular remodelling in tachycardia-induced dilated cardiomyopathy (DCM). Our study includes healthy controls (N = 7) and DCM pigs (N = 10). Molecular analysis showed global myocardial metabolic abnormalities, some of them related to myocardial hibernation in failing hearts, supporting the translationality of our model to study cardiac remodelling in dilated cardiomyopathy. Histological analysis showed unorganized and agglomerated collagen accumulation in the dilated ventricles and a higher percentage of fibrosis in the right (RV) than in the left (LV) ventricle (P = .016). The Fourier Transform Infrared Spectroscopy (FTIR) 1st and 2nd indicators, which are markers of the myofiber/collagen ratio, were reduced in dilated hearts, with the 1st indicator reduced by 45% and 53% in the RV and LV, respectively, and the 2nd indicator reduced by 25% in the RV. The 3rd FTIR indicator, a marker of the carbohydrate/lipid ratio, was up-regulated in the right and left dilated ventricles but to a greater extent in the RV (2.60-fold vs 1.61-fold, P = .049). Differential scanning calorimetry (DSC) showed a depression of the freezable water melting point in DCM ventricles - indicating structural changes in the tissue architecture - and lower protein stability. Our results suggest that the 1st, 2nd and 3rd FTIR indicators are useful markers of cardiac remodelling. Moreover, the 2nd and 3rd FITR indicators, which are altered to a greater extent in the right ventricle, are associated with greater fibrosis.

Spatial correlation of native and engineered cartilage components at micron resolution

Tissue engineering (TE) approaches are being widely investigated for repair of focal defects in articular cartilage. However, the amount and/or type of extracellular matrix (ECM) produced in engineered constructs does not always correlate with the resultant mechanical properties. This could be related to the specifics of ECM distribution throughout the construct. Here, we present data on the amount and distribution of the primary components of native and engineered cartilage (i.e., collagen, proteoglycan (PG), and water) using Fourier transform infrared imaging spectroscopy (FT-IRIS). These data permit visualization of matrix and water at 25 μm resolution throughout the tissues, and subsequent colocalization of these components using image processing methods. Native and engineered cartilage were cryosectioned at 80 μm for evaluation by FT-IRIS in the mid-infrared (MIR) and near-infrared (NIR) regions. PG distribution correlated strongly with water in native and engineered cartilage, supporting the binding of water to PG in both tissues. In addition, NIR-derived matrix peaks correlated significantly with MIR-derived collagen peaks, confirming the interpretation that these absorbances arise primarily from collagen and not PG. The combined use of MIR and NIR permits assessment of ECM and water spatial distribution at the micron level, which may aid in improved development of TE techniques.

Infrared spectroscopic imaging: Label-free biochemical analysis of stroma and tissue fibrosis

Infrared spectroscopic tissue imaging is a potentially powerful adjunct tool to current histopathology techniques. By coupling the biochemical signature obtained through infrared spectroscopy to the spatial information offered by microscopy, this technique can selectively analyze the chemical composition of different features of unlabeled, unstained tissue sections. In the past, the tissue features that have received the most interest were parenchymal and epithelial cells, chiefly due to their involvement in dysplasia and progression to carcinoma; however, the field has recently turned its focus toward stroma and areas of fibrotic change. These components of tissue present an untapped source of biochemical information that can shed light on many diverse disease processes, and potentially hold useful predictive markers for these same pathologies. Here we review the recent applications of infrared spectroscopic imaging to stromal and fibrotic regions of diseased tissue, and explore the potential of this technique to advance current capabilities for tissue analysis.

Lumican delays melanoma growth in mice and drives tumor molecular assembly as well as response to matrix-targeted TAX2 therapeutic peptide

Lumican is a small leucine-rich proteoglycan (SLRP) being known as a key regulator of collagen fibrillogenesis. However, little attention has been given so far in studying its influence on tumor-associated matrix architecture. Here, we investigate the role of host lumican on tumor matrix organization as well as on disease progression considering an immunocompetent model of melanoma implanted in Lum ^-/- vs. wild type syngeneic mice. Conjointly, lumican impact on tumor response to matrix-targeted therapy was evaluated considering a previously validated peptide, namely TAX2, that targets matricellular thrombospondin-1. Analysis of available genomics and proteomics databases for melanoma first established a correlation between lumican expression and patient outcome. In the B16 melanoma allograft model, endogenous lumican inhibits tumor growth and modulates response to TAX2 peptide. Indeed, IHC analyses revealed that lumican deficiency impacts intratumoral distribution of matricellular proteins, growth factor and stromal cells. Besides, innovative imaging approaches helped demonstrating that lumican host expression drives biochemical heterogeneity of s.c. tumors, while modulating intratumoral collagen deposition as well as organization. Altogether, the results obtained present lumican as a strong endogenous inhibitor of tumor growth, while identifying for the first time this proteoglycan as a major driver of tumor matrix coherent assembly.

Conformational and thermal characterization of left ventricle remodeling post-myocardial infarction

Adverse cardiac remodeling after myocardial infarction (MI) causes impaired ventricular function and heart failure. Histopathological characterization is commonly used to detect the location, size and shape of MI sites. However, the information about chemical composition, physical structure and molecular mobility of peri- and infarct zones post-MI is rather limited. The main objective of this work was to explore the spatiotemporal biochemical and biophysical alterations of key cardiac components post-MI. The FTIR spectra of healthy and remote myocardial tissue shows amides A, I, II and III associated with proteins in freeze-died tissue as major absorptions bands. In infarcted myocardium, the spectrum of these main absorptions was deeply altered. FITR evidenced an increase of the amide A band and the distinct feature of the collagen specific absorption band at 1338cm^-1 in the infarct area at 21days post-MI. At 21days post-MI, it also appears an important shift of amide I from 1646cm^-1 to 1637cm^-1 that suggests the predominance of the triple helical conformation in the proteins. The new spectra bands also indicate an increase in proteoglycans, residues of carbohydrates in proteins and polysaccharides in ischemic areas. Thermal analysis indicates a deep increase of unfreezable water/freezable water in peri- and infarcted tissues. In infarcted tissue is evidenced the impairment of myofibrillar proteins thermal profile and the emergence of a new structure. In conclusion, our results indicate a profound evolution of protein secondary structures in association with collagen deposition and reorganization of water involved in the scar maturation of peri- and infarct zones post-MI.

Renal ischemia/reperfusion-induced cardiac hypertrophy in mice: Cardiac morphological and morphometric characterization

Background

Tissue remodeling is usually dependent on the deposition of extracellular matrix that may result in tissue stiffness and impaired myocardium contraction.

Objectives

We had previously demonstrated that renal ischemia/reperfusion (I/R) is able to induce development of cardiac hypertrophy in mice. Therefore, we aimed to characterize renal I/R-induced cardiac hypertrophy.

Design

C57BL/6 J mice were subjected to 60 minutes’ unilateral renal pedicle occlusion, followed by reperfusion (I/R) for 5, 8, 12 or 15 days. Gene expression, protein abundance and morphometric analyses were performed in all time points.

Results

Left ventricle wall thickening was increased after eight days of reperfusion (p < 0.05). An increase in the number of heart ventricle capillaries and diameter after 12 days of reperfusion (p < 0.05) was observed; an increase in the density of capillaries starting at 5 days of reperfusion (p < 0.05) was also observed. Analyses of MMP2 protein levels showed an increase at 15 days compared to sham (p < 0.05). Moreover, TGF-β gene expression was downregulated at 12 days as well TIMP 1 and 2 (p < 0.05). The Fourier-transform infrared spectroscopy analysis showed that collagen content was altered only in the internal section of the heart (p < 0.05); such data were supported by collagen mRNA levels.

Conclusions

Renal I/R leads to impactful changes in heart morphology, accompanied by an increase in microvasculature. Although it is clear that I/R is able to induce cardiac remodeling, such morphological changes is present in only a section of the heart tissue.

Fourier Transform Infrared Spectroscopic Imaging-Derived Collagen Content and Maturity Correlates with Stress in the Aortic Wall of Abdominal Aortic Aneurysm Patients

Abdominal aortic aneurysm (AAA) is a degenerative disease of the aorta characterized by severe disruption of the structural integrity of the aortic wall and its major molecular constituents. From the early stages of disease, elastin in the aorta becomes highly degraded and is replaced by collagen. Questions persist as to the contribution of collagen content, quality and maturity to the potential for rupture. Here, using our recently developed Fourier transform infrared imaging spectroscopy (FT-IRIS) method, we quantified collagen content and maturity in the wall of AAA tissues in pairs of specimens with different wall stresses. CT scans of AAAs from 12 patients were used to create finite element models to estimate stress in different regions of tissue. Each patient underwent elective repair of the AAA, and two segments of the AAA tissues from anatomic regions more proximal or distal with different wall stresses were evaluated by histology and FT-IRIS after excision. For each patient, collagen content was generally greater in the tissue location with lower wall stress, which corresponded to the more distal anatomic regions. The wall stress/collagen ratio was greater in the higher stress region compared to the lower stress region (1.01 ± 1.09 vs. 0.55 ± 0.084, p = 0.02). The higher stress region also corresponded to the location with reduced intraluminal thrombus thickness. Further, collagen maturity tended to decrease with increased collagen content (p = 0.068, R = 0.38). Together, these results suggest that an increase in less mature collagen content in AAA patients does not effectively compensate for the loss of elastin in the aortic wall, and results in a reduced capability to endure wall stresses.

Biochemical Monitoring of Spinal Cord Injury by FT-IR Spectroscopy--Effects of Therapeutic Alginate Implant in Rat Models

Spinal cord injury (SCI) induces complex biochemical changes, which result in inhibition of nervous tissue regeneration abilities. In this study, Fourier-transform infrared (FT-IR) spectroscopy was applied to assess the outcomes of implants made of a novel type of non-functionalized soft calcium alginate hydrogel in a rat model of spinal cord hemisection (n = 28). Using FT-IR spectroscopic imaging, we evaluated the stability of the implants and the effects on morphology and biochemistry of the injured tissue one and six months after injury. A semi-quantitative evaluation of the distribution of lipids and collagen showed that alginate significantly reduced injury-induced demyelination of the contralateral white matter and fibrotic scarring in the chronic state after SCI. The spectral information enabled to detect and localize the alginate hydrogel at the lesion site and proved its long-term persistence in vivo. These findings demonstrate a positive impact of alginate hydrogel on recovery after SCI and prove FT-IR spectroscopic imaging as alternative method to evaluate and optimize future SCI repair strategies.

Fourier transform infrared microspectroscopy monitoring of 5-fluorouracil-induced apoptosis in SW620 colon cancer cells

Colon cancer is associated with a high incidence and a poor prognosis. The aim of the present study was to determine whether Fourier transform infrared (FTIR) microspectroscopy can be used to monitor the chemotherapy drug-induced apoptosis of SW620 colon cancer cells. The 50% inhibitory concentration (IC₅₀) of 5-fluorouracil (5-FU), the main chemotherapeutic agent used for the treatment of colorectal cancer, was determined as the inhibition of growth of the SW620 cells using an MTT assay. Cell starvation and 5-FU treatment synergized to arrest the cells in the G1 and S phases of the cell cycle. FTIR combined with fluorescence activated cell sorting (FACS) analysis were used to analyze the SW620 cells following treatment with 5-FU for 12, 24 and 48 h. The apoptotic cells had several spectral characteristics. The relative peak intensity ratio (I₁₇₄₀/I₁₄₆₀) was significantly increased (P<0.05), the I₁₇₄₀/I₁₄₆₀ ratio, associated with a band of amino acid residues at 1,410 cm⁻¹ was significantly increased at the early and late phases of cell death (P<0.05), the peaks at 1,240 cm⁻¹ increased in wave number, a band at 1,040 cm⁻¹, associated with polysaccharides, appeared at 24 and 48 h and then moved to a higher wave number and the I₁₀₄₀/I₁₄₆₀ ratio increased at the late stage of apoptosis. These results demonstrated that FTIR can be used as a label-free technique to monitor cancer cell apoptosis and to understand the spectral fingerprints of apoptotic cells. This suggested that FTIR spectral features have potential as a powerful tool to monitor cancer cell apoptosis.

Fourier transform infrared spectroscopy to quantify collagen and elastin in an in vitro model of extracellular matrix degradation in aorta

Extracellular matrix (ECM) is a key component and regulator of many biological tissues including aorta. Several aortic pathologies are associated with significant changes in the composition of the matrix, especially in the content, quality and type of aortic structural proteins, collagen and elastin. The purpose of this study was to develop an infrared spectroscopic methodology that is comparable to biochemical assays to quantify collagen and elastin in aorta. Enzymatically degraded porcine aorta samples were used as a model of ECM degradation in abdominal aortic aneurysm (AAA). After enzymatic treatment, Fourier transform infrared (FTIR) spectra of the aortic tissue were acquired by an infrared fiber optic probe (IFOP) and FTIR imaging spectroscopy (FT-IRIS). Collagen and elastin content were quantified biochemically and partial least squares (PLS) models were developed to predict collagen and elastin content in aorta based on FTIR spectra. PLS models developed from FT-IRIS spectra were able to predict elastin and collagen content of the samples with strong correlations (RMSE of validation = 8.4% and 11.1% of the range respectively), and IFOP spectra were successfully used to predict elastin content (RMSE = 11.3% of the range). The PLS regression coefficients from the FT-IRIS models were used to map collagen and elastin in tissue sections of degraded porcine aortic tissue as well as a human AAA biopsy tissue, creating a similar map of each component compared to histology. These results support further application of FTIR spectroscopic techniques for evaluation of AAA tissues.

Rapid approach to analyze biochemical variation in rat organs by ATR FTIR spectroscopy

ATR FTIR spectra were collected from rat tissue homogenates (myocardium, brain, liver, lung, intestine, and kidney) to analyze their biochemical content. Based on the second derivative of an average spectral profile it was possible to assign bands e.g. to triglycerides and cholesterol esters, proteins, phosphate macromolecules (DNA, RNA, phospholipids, phosphorylated proteins) and others (glycogen, lactate). Peaks in the region of 1600-1700 cm(-1) related to amide I mode revealed the secondary structure of proteins. The collected spectra do not characterize morphological structure of the investigated tissues but show their different composition. The comparison of spectral information gathered from FTIR spectra of the homogenates and those obtained previously from FTIR imaging of the tissue sections implicates that the presented here approach can be successfully employed in the investigations of biochemical variation in animal tissues. Moreover, it can be used in the pharmacological and pharmacokinetic studies to correlate the overall biochemical status of the tissue with the pathological changes it has undergone.