Methods for Quantifying Fibrillar Collagen Alignment

Dietary Branched-Chain Amino Acids Modify Postinfarct Cardiac Remodeling and Function in the Murine Heart

BACKGROUND

Branched-chain amino acids (BCAAs), which are derived from the diet, are markedly elevated in cardiac tissue following myocardial infarction (MI). Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling.

METHODS

To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, we fed mice a low or a high BCAA diet for 2 weeks before MI and for 4 weeks after MI. Cardiac structural and functional changes were evaluated by echocardiography, gravimetry, and histopathological analyses. Immunoblotting was used to evaluate the effects of BCAAs on isolated cardiac myofibroblast differentiation.

RESULTS

The low BCAA diet decreased circulating BCAA concentrations by >2-fold when compared with the high BCAA diet. Although neither body weights nor heart masses were different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. The low BCAA diet preserved stroke volume and cardiac output after MI, whereas the high BCAA diet promoted progressive decreases in cardiac function. Although BCAAs were required for myofibroblast differentiation in vitro, cardiac fibrosis, scar collagen topography, and cardiomyocyte cross-sectional area were not different between the dietary groups; however, male mice fed the high BCAA diet had longer cardiomyocytes and higher capillary density compared with the low BCAA group.

CONCLUSIONS

A low BCAA diet mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI in mice, with dietary effects more prominent in males.

Mobilization of subcutaneous fascia contributes to the vascularization and function of acellular adipose matrix via formation of vascular matrix complex

Regenerative biomaterials are commonly used for soft-tissue repair in both pre-clinical and clinical settings, but their effectiveness is often limited by poor regenerative outcomes and volume loss. Efficient vascularization is crucial for the long-term survival and function of these biomaterials in vivo. Despite numerous pro-vascularization strategies developed over the past decades, the fundamental mechanisms of vascularization in regenerative biomaterials remain largely unexplored. In this study, we employed matrix-tracing, vessel-tracing, cell-tracing, and matrix analysis techniques, etc. to investigate the vascularization process of acellular adipose matrix (AAM) implants in a murine model. Here, we show that the mobilization of subcutaneous fascia contributes to the vascularization in AAM implants. Tracing techniques revealed that the subcutaneous fascia migrates to encase the AAM implants, bringing along fascia-embedded blood vessels, thus forming a vascular matrix complex (VMC) on the implant surface. Restricting fascia mobilization or removing fascia tissue significantly reduced AAM vascularization and hindered the regenerative process, leading to implant collapse at a later stage. Notably, VMC exhibited a dynamic matrix remodeling process closely aligned with implant vascularization. Our findings highlight the crucial role of subcutaneous fascia mobility in facilitating the vascularization of AAM implants, offering a novel direction and target for guaranteeing long-term survival and function of regenerative biomaterials in vivo.

Fibrillin-1 G234D mutation in the hybrid1 domain causes tight skin associated with dysregulated elastogenesis and increased collagen cross-linking in mice

Fibrillin-1, an extracellular matrix (ECM) protein encoded by the FBN1 gene, serves as a microfibril scaffold crucial for elastic fiber formation and homeostasis in pliable tissue such as the skin. Aside from causing Marfan syndrome, some mutations in FBN1 result in scleroderma, marked by hardened and thicker skin which limits joint mobility. Here, we describe a tight skin phenotype in the Fbn1G234D/G234D mice carrying a corresponding variant of FBN1 in the hybrid1 domain that was identified in a patient with familial aortic dissection. Unlike scleroderma, skin thickness and collagen fiber abundance do not change in the Fbn1G234D/G234D mutant skin. Instead, increased collagen cross-links were observed. In addition, short elastic fibers were sparsely located underneath the panniculus muscle layer, and an abundance of thin, aberrant elastic fibers was increased within the subcutaneous fascia, which may have tightened skin attachment to the underlying skeletal muscle. Structurally, Fbn1G234D/G234D microfibrils have a disrupted shoulder region that shares similarities with hybrid1 deletion mutant microfibrils. We then demonstrate the consequence of fibrillin-1 G234D mutation on dermal fibroblast functions. Mutant primary fibroblasts produce fewer elastic fibers, exhibit slower migration and increased cell stiffness. Moreover, secretome from mutant fibroblasts are marked by enhanced secretion of ECM, ECM-modifying enzymes, proteoglycans and cytokines, which are pro-tissue repair/fibrogenic. The transcriptome of mutant fibroblasts displays an increased expression of myogenic developmental and immune-related genes. Our study proposes that imbalanced ECM homeostasis due to a fibrillin-1 G234D mutation impacts fibroblast properties with potential ramifications on skin function.

Stress relaxation rates of myocardium from failing and non-failing hearts

The heart is a dynamic pump whose function is influenced by its mechanical properties. The viscoelastic properties of the heart, i.e., its ability to exhibit both elastic and viscous characteristics upon deformation, influence cardiac function. Viscoelastic properties change during heart failure (HF), but direct measurements of failing and non-failing myocardial tissue stress relaxation under constant displacement are lacking. Further, how consequences of tissue remodeling, such as fibrosis and fat accumulation, alter the stress relaxation remains unknown. To address this gap, we conducted stress relaxation tests on porcine myocardial tissue to establish baseline properties of cardiac tissue. We found porcine myocardial tissue to be fast relaxing, characterized by stress relaxation tests on both a rheometer and microindenter. We then measured human left ventricle (LV) epicardium and endocardium tissue from non-failing, ischemic HF and non-ischemic HF patients by microindentation. Analyzing by patient groups, we found that ischemic HF samples had slower stress relaxation than non-failing endocardium. Categorizing the data by stress relaxation times, we found that slower stress relaxing tissues were correlated with increased collagen deposition and increased α-smooth muscle actin (α-SMA) stress fibers, a marker of fibrosis and cardiac fibroblast activation, respectively. In the epicardium, analyzing by patient groups, we found that ischemic HF had faster stress relaxation than non-ischemic HF and non-failing. When categorizing by stress relaxation times, we found that faster stress relaxation correlated with Oil Red O staining, a marker for adipose tissue. These data show that changes in stress relaxation vary across the different layers of the heart during ischemic versus non-ischemic HF. These findings reveal how the viscoelasticity of the heart changes, which will lead to better modeling of cardiac mechanics for in vitro and in silico HF models.

Sulfur dioxide exposure of mice induces peribronchiolar fibrosis-A defining feature of deployment-related constrictive bronchiolitis

Deployment-related constrictive bronchiolitis (DRCB) has emerged as a health concern in military personnel returning from Southwest Asia. Exposure to smoke from a fire at the Al-Mishraq sulfur enrichment facility and/or burn pits was reported by a subset of Veterans diagnosed with this disorder. DRCB is characterized by thickening and fibrosis of small airways (SA) in the lung, but whether these are related to toxin inhalation remains uncertain. The aim of this study was to determine whether sulfur dioxide (SO2) exposure can induce histopathological features of DRCB. C57BL/6J mice were exposed to 50 ± 5 ppm SO2 for one hour/day for five consecutive days. Lungs from exposed and unexposed mice were evaluated on day 5, 10, and 20. Lung sections were stained using hematoxylin and eosin, Masson's trichrome, picrosirius red (PSR), and immunofluorescence for club cell secretory protein, acetylated-α-tubulin, and Ki67. Small airway wall thickness was determined by morphometric analysis and collagen content was quantified by measuring PSR fluorescence intensity. CurveAlign and CT-FIRE were used to enumerate collagen fibers and assess fibers' width and length, respectively. Leukocyte subpopulations were quantified by flow cytometry analysis. This protocol of SO2 exposure of mice: 1) Triggered club cell proliferation and differentiation; 2) Increased SA wall thickness by inducing subepithelial collagen deposition; and 3) Increased width, length, and number, but not density, of collagen fibers within the wall of SA. 4) Induced no peribronchiolar inflammation or respiratory bronchiolitis. Collectively, these findings implicate club cell proliferation and differentiation in the profibrotic response to SO2 and identify this SO2 exposure as a potentially effective though imperfect model for studying SA fibrosis in DRCB.

Effects of thread design on soft and hard tissue healing around implants in lipopolysaccharide-induced peri-implantitis-like lesions in rat maxillae

OBJECTIVES

This study investigated the effects of thread design on the soft and hard tissues around implants in rat maxillary peri-implantitis-like lesions.

METHODS

Fourteen, 9-week-old, female Wistar rats were used in this study. Two types of grade IV titanium tissue-level implants with a standard V-shape and buttress threads were prepared (control and test implants, respectively). The control and test implants were randomly placed into healed left or right sides four weeks after first molar extraction. Daily administration of lipopolysaccharide (LPS) into the peri-implant mucosal sulcus was performed in combination with Freund's incomplete and complete adjuvants. The maxillae were harvested 16 days after LPS administration for quantitative and qualitative analyses.

RESULTS

LPS administration induced significant marginal bone loss, with increases in osteoclasts and polymorphonuclear cells around control implants. LPS administration did not change cell numbers around t nor alter bone quality inside the buttress threads of the test implants, but resulted in a significant deterioration of bone quality, defined as the preferential alignment of collagen fibers inside the V-shaped threads of the control implant. LPS administration also significantly increased calprotectin production in the epithelium around the test implants and significantly increased calprotectin production in the connective tissue around both the control and test implants.

CONCLUSIONS

Buttress threads at specific angles provided resistance to LPS-induced inflammation in rats with LPS-induced peri-implantitis-like lesions. The upregulated production of calprotectin induced by LPS administration in the epithelium and connective tissues around the test implants may facilitate inflammation control around implants.

Collagen Density Is Associated With Pathological Complete Response to Neoadjuvant Chemotherapy in Triple-Negative Breast Cancer Patients

BACKGROUND AND OBJECTIVES

The tumor-associated stroma is an essential compartment in breast cancer, and collagen fiber organization in the stroma has been reported to be correlated with prognosis. In this study, we sought to evaluate collagen fiber characteristics in relation to pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) in breast cancer patients.

METHODS

A total of 388 breast cancer patients receiving NAC were enrolled. The stroma type was manually assessed on pretreatment hematoxylin and eosin (HE)-stained slides, and the collagen fiber features were quantified by a computer tool. The relationship between syndecan-1 expression and collagen fibers and its correlation with treatment efficacy were detected by immunohistochemistry.

RESULTS

The pCR rate of patients with collagen-dominant stroma was lower than that of patients with lymphocyte-dominant stroma (19.6% vs. 40.0%, p = 0.001). Patients who achieved pCR had straighter and less dense fibers in pretreatment biopsied tissue than non-pCR patients (p = 0.031, p = 0.044). Additionally, the pCR group had greater syndecans-1 expression on the tumor epithelium than the non-pCR group (p < 0.001), while there was no statistically significant difference in the stroma (p = 0.333). Collagen fiber density was the only factor associated with pCR after correction for other clinicopathological variables in triple-negative breast cancer (TNBC) patients (OR 0.466, 95% CI 0.227-0.956, p = 0.037); patients with lower fiber density had a greater pCR rate (37.5% vs. 12.5%, p = 0.021).

CONCLUSIONS

Collagen fiber density was associated with pCR in patients with breast cancer, and it could be a potential candidate for discriminating between responders and nonresponders for TNBC patients receiving NAC.

Sex-specific cardiovascular adaptations to simulated microgravity in Sprague-Dawley rats

Men and women have different cardiovascular responses to spaceflight; however, few studies have focused on direct comparisons between sexes. We investigated the mechanisms of aortic stiffening in socially and sexually mature 20-week-old male and female Sprague Dawley (SD) rats exposed to hindlimb unloading (HLU) for 14 days. Pulse wave velocity (PWV) was greater in the aortic arch of females after HLU versus control females (n = 6-8). HLU had no effect on aortic PWV in males (n = 5-6). Aortic α smooth muscle actin, myosin, collagen, elastin, and collagen-to-elastin ratio were not different in rats of either sex following HLU. The levels of G protein-coupled estrogen receptor (GPER) were lower in the aorta of SD females exposed to HLU compared with female controls but were not altered in males. HLU females also had lower aortic PPARγ, increased oxidative stress markers, and diastolic dysfunction compared with control females. GPER agonist G1 prevented the increase in PWV and 8-hydroxy-2'-deoxyguanosine without altering PPARγ or p47phox in HLU females (n = 4 in each group) suggesting that lower GPER may contribute to arterial stiffening in the setting of simulated microgravity. This study highlights sex-specific vascular adaptations to the state of simulated microgravity.

Rebuilding the autoimmune-damaged corneal stroma through topical lubrication

Corneal lubrication is the most common treatment for relieving the signs and symptoms of dry eye and is considered to be largely palliative with no regenerative functions. Here we challenge this notion by demonstrating that wetting the desiccated cornea of an aqueous-deficient mouse model with the simplest form of lubrication, a saline-based solution, is sufficient to rescue the severely disrupted collagen-rich architecture of the stroma, the largest corneal compartment that is essential to transparency and vision. At the single cell level we show that stromal keratocytes responsible for maintaining stromal integrity are converted from an inflammatory state into unique reparative cell states by lubrication alone, thus revealing the extensive plasticity of these cells and the regenerative function of lubricating the surface. We further show that the generation of a reparative phenotype is due, in part, to disruption of an IL1β autocrine amplification loop promoting chronic inflammation. Thus, our study uncovers the regenerative potential of topical lubrication in dry eye and represents a paradigm shift in our understanding of its therapeutic impact.

Topographical changes in extracellular matrix during skin fibrosis and recovery can be evaluated using automated image analysis algorithms

Skin fibrosis is characterized by fibroblast activation and intradermal fat loss, resulting in excess deposition and remodeling of dermal extracellular matrix (ECM). The topography of the dominant ECM proteins, such as collagens, can indicate skin stiffness and remains understudied in evaluating fibrotic skin. Here, we adapted two different unbiased image analysis algorithms to define collagen topography and alignment in a genetically inducible and reversible Wnt activation fibrosis model. We demonstrated that Wnt-activated fibrotic skin has altered collagen fiber characteristics and a loss of collagen alignment, which were restored in the reversible model. This study highlights how unbiased algorithms can be used to analyze ECM topography, providing novel avenues to evaluate fibrotic skin onset, recovery, and treatment.

Stiffness-Dependent Lysyl Oxidase Regulation through Hypoxia-Inducing Factor 1 Drives Extracellular Matrix Modifications in Psoriasis

Psoriasis is a common chronic inflammatory skin disease characterized by a thickened epidermis with elongated rete ridges and massive immune cell infiltration. It is currently unclear what impact mechanoregulatory aspects may have on disease progression. Using multiphoton second harmonic generation microscopy, we found that the extracellular matrix was profoundly reorganized within psoriatic dermis. Collagen fibers were highly aligned and assembled into thick, long collagen bundles, whereas the overall fiber density was reduced. This was particularly pronounced within dermal papillae extending into the epidermis. Furthermore, the extracellular matrix-modifying enzyme lysyl oxidase was highly upregulated in the dermis of patients with psoriasis. In vitro experiments identified a previously unreported link between hypoxia-inducing factor 1 stabilization and lysyl oxidase protein regulation in mechanosensitive skin fibroblasts. Lysyl oxidase secretion and activity directly correlated with substrate stiffness and were independent of hypoxia and IL-17. Finally, single-cell RNA-sequencing analysis identified skin fibroblasts expressing high amounts of lysyl oxidase and confirmed elevated hypoxia-inducing factor 1 expression in psoriasis. Our findings suggest a potential yet undescribed mechanical aspect of psoriasis. Deregulated mechanical forces hence may be involved in initiating or maintaining of a positive feedback loop in fibroblasts and contribute to tissue stiffening and diminished skin elasticity in psoriasis, potentially exacerbating disease pathogenesis.

Matricellular protein CCN1 promotes collagen alignment and scar integrity after myocardial infarction

BACKGROUND

Members of the cellular communication network family (CCN) of matricellular proteins, like CCN1, have long been implicated in the regulation of cellular processes underlying wound healing, tissue fibrogenesis, and collagen dynamics. While many studies suggest antifibrotic actions for CCN1 in the adult heart through the promotion of myofibroblast senescence, they largely relied on exogenous supplementation strategies in in vivo models of cardiac injury where its expression is already induced-which may confound interpretation of its function in this process. The objective of this study was to interrogate the role of the endogenous protein on fibroblast function, collagen structural dynamics, and its associated impact on cardiac fibrosis after myocardial infarction (MI).

METHODS/RESULTS

Here, we employed CCN1 loss-of-function methodologies, including both in vitro siRNA-mediated depletion and in vivo fibroblast-specific knockout mice to assess the role of the endogenous protein on cardiac fibroblast fibrotic signaling, and its involvement in acute scar formation after MI. In vitro depletion of CCN1 reduced cardiac fibroblast senescence and proliferation. Although depletion of CCN1 decreased the expression of collagen processing and stabilization enzymes (i.e., P4HA1, PLOD1, and PLOD2), it did not inhibit myofibroblast induction or type I collagen synthesis. Alone, fibroblast-specific removal of CCN1 did not negatively impact ventricular performance or myocardial collagen content but did contribute to disorganization of collagen fibrils and increased matrix compliance. Similarly, Ccn1 ablated animals subjected to MI showed no discernible alterations in cardiac structure or function one week after permanent coronary artery ligation, but exhibited marked increases in incidence of mortality and cardiac rupture. Consistent with our findings that CCN1 depletion does not assuage myofibroblast conversion or type I collagen synthesis in vitro, Ccn1 knockout animals revealed no measurable differences in collagen scar width or mass compared to controls; however, detailed structural analyses via SHG and TEM of scar regions revealed marked alterations in their scar collagen topography-exhibiting changes in numerous macro- and micro-level collagen architectural attributes. Specifically, Ccn1 knockout mice displayed heightened ECM structural complexity in post-MI scar regions, including diminished local alignment and heightened tortuosity of collagen fibers, as well as reduced organizational coherency, packing, and size of collagen fibrils. Associated with these changes in ECM topography with the loss of CCN1 were reductions in fibroblast-matrix interactions, as evidenced by reduced fibroblast nuclear and cellular deformation in vivo and reduced focal-adhesion formation in vitro; findings that ultimately suggest CCN1's ability to influence fibroblast-led collagen alignment may in part be credited to its capacity to augment fibroblast-matrix interactions.

CONCLUSIONS

These findings underscore the pivotal role of endogenous CCN1 in the scar formation process occurring after MI, directing the appropriate arrangement of the extracellular matrix's collagenous components in the maturing scar-shaping the mechanical properties that support its structural stability. While this suggests an adaptive role for CCN1 in regulating collagen structural attributes crucial for supporting scar integrity post MI, the long-term protracted expression of CCN1 holds maladaptive implications, potentially diminishing collagen structural complexity and compliance in non-infarct regions.

Spatial interactions modulate tumor growth and immune infiltration

Direct observation of tumor-immune interactions is unlikely in tumors with currently available technology, but computational simulations based on clinical data can provide insight to test hypotheses. It is hypothesized that patterns of collagen evolve as a mechanism of immune escape, but the exact nature of immune-collagen interactions is poorly understood. Spatial data quantifying collagen fiber alignment in squamous cell carcinomas indicates that late-stage disease is associated with highly aligned fibers. Our computational modeling framework discriminates between two hypotheses: immune cell migration that moves (1) parallel or (2) perpendicular to collagen fiber orientation. The modeling recapitulates immune-extracellular matrix interactions where collagen patterns provide immune protection, leading to an emergent inverse relationship between disease stage and immune coverage. Here, computational modeling provides important mechanistic insights by defining a kernel cell-cell interaction function that considers a spectrum of local (cell-scale) to global (tumor-scale) spatial interactions. Short-range interaction kernels provide a mechanism for tumor cell survival under conditions with strong Allee effects, while asymmetric tumor-immune interaction kernels lead to poor immune response. Thus, the length scale of tumor-immune interaction kernels drives tumor growth and infiltration.

Quantitative Assessment of Collagen Remodeling during a Murine Pregnancy

Uterine cervical remodeling is a fundamental feature of pregnancy, facilitating the delivery of the fetus through the cervical canal. Yet, we still know very little about this process due to the lack of methodologies that can quantitatively and unequivocally pinpoint the changes the cervix undergoes during pregnancy. We utilize polarization-resolved second harmonic generation to visualize the alterations the cervix extracellular matrix, specifically collagen, undergoes during pregnancy with exquisite resolution. This technique provides images of the collagen orientation at the pixel level (0.4 μm) over the entire murine cervical section. They show tight and ordered packing of collagen fibers around the os at the early stage of pregnancy and their disruption at the later stages. Furthermore, we utilize a straightforward statistical analysis to demonstrate the loss of order in the tissue, consistent with the loss of mechanical properties associated with this process. This work provides a deeper understanding of the parturition process and could support research into the cause of pathological or premature birth.

Extraction of collagen morphological features from second-harmonic generation microscopy images via GLCM and CT analyses: A cross-laboratory study

Second-harmonic generation (SHG) microscopy provides a high-resolution label-free approach for noninvasively detecting collagen organization and its pathological alterations. Up to date, several imaging analysis algorithms for extracting collagen morphological features from SHG images-such as fiber size and length, order and anisotropy-have been developed. However, the dependence of extracted features on experimental setting represents a significant obstacle for translating the methodology in the clinical practice. We tackled this problem by acquiring SHG images of the same kind of collagenous sample in various laboratories using different experimental setups and imaging conditions. The acquired images were analyzed by commonly used algorithms, such as gray-level co-occurrence matrix or curvelet transform; the extracted morphological features were compared, finding that they strongly depend on some experimental parameters, whereas they are almost independent from others. We conclude with useful suggestions for comparing results obtained in different labs using different experimental setups and conditions.

Dietary Branched Chain Amino Acids Modify Post-Infarct Cardiac Remodeling and Function in the Murine Heart

Introduction

Branch-chain amino acids (BCAA) are markedly elevated in the heart following myocardial infarction (MI) in both humans and animal models. Nevertheless, it remains unclear whether dietary BCAA levels influence post-MI remodeling. We hypothesize that lowering dietary BCAA levels prevents adverse cardiac remodeling after MI.

Methods and Results

To assess whether altering dietary BCAA levels would impact circulating BCAA concentrations, mice were fed a low (1/3×), normal (1×), or high (2×) BCAA diet over a 7-day period. We found that mice fed the low BCAA diet had >2-fold lower circulating BCAA concentrations when compared with normal and high BCAA diet feeding strategies; notably, the high BCAA diet did not further increase BCAA levels over the normal chow diet. To investigate the impact of dietary BCAAs on cardiac remodeling and function after MI, male and female mice were fed either the low or high BCAA diet for 2 wk prior to MI and for 4 wk after MI. Although body weights or heart masses were not different in female mice fed the custom diets, male mice fed the high BCAA diet had significantly higher body and heart masses than those on the low BCAA diet. Echocardiographic assessments revealed that the low BCAA diet preserved stroke volume and cardiac output for the duration of the study, while the high BCAA diet led to progressive decreases in cardiac function. Although no discernible differences in cardiac fibrosis, scar collagen topography, or cardiomyocyte cross-sectional area were found between the dietary groups, male mice fed the high BCAA diet showed longer cardiomyocytes and higher capillary density compared with the low BCAA group.

Conclusions

Provision of a diet low in BCAAs to mice mitigates eccentric cardiomyocyte remodeling and loss of cardiac function after MI, with dietary effects more prominent in males.

Delayed Collagen Production without Myofibroblast Formation Contributes to Reduced Scarring in Adult Skin Microwounds

In adult mammals, wound healing predominantly follows a fibrotic pathway, culminating in scar formation. However, cutaneous microwounds generated through fractional photothermolysis, a modality that produces a constellation of microthermal zones, exhibit a markedly different healing trajectory. Our study delineates the cellular attributes of these microthermal zones, underscoring a temporally limited, subclinical inflammatory milieu concomitant with rapid re-epithelialization within 24 hours. This wound closure is facilitated by the activation of genes associated with keratinocyte migration and differentiation. In contrast to macrothermal wounds, which predominantly heal through a robust myofibroblast-mediated collagen deposition, microthermal zones are characterized by absence of wound contraction and feature delayed collagen remodeling, initiating 5-6 weeks after injury. This distinct wound healing is characterized by a rapid re-epithelialization process and a muted inflammatory response, which collectively serve to mitigate excessive myofibroblast activation. Furthermore, we identify an initial reparative phase characterized by a heterogeneous extracellular matrix protein composition, which precedes the delayed collagen remodeling. These findings extend our understanding of cutaneous wound healing and may have significant implications for the optimization of therapeutic strategies aimed at mitigating scar formation.

Quantifying in vivo collagen reorganization during immunotherapy in murine melanoma with second harmonic generation imaging

Significance

Increased collagen linearization and deposition during tumorigenesis can impede immune cell infiltration and lead to tumor metastasis. Although melanoma is well studied in immunotherapy research, studies that quantify collagen changes during melanoma progression and treatment are lacking.

Aim

We aim to image in vivo collagen in preclinical melanoma models during immunotherapy and quantify the collagen phenotype in treated and control mice.

Approach

Second-harmonic generation imaging of collagen was performed in mouse melanoma tumors in vivo over a treatment time course. Animals were treated with a curative radiation and immunotherapy combination. Collagen morphology was quantified over time at an image and single-fiber level using CurveAlign and CT-FIRE software.

Results

In immunotherapy-treated mice, collagen was reorganized toward a healthy phenotype, including shorter, wider, curlier collagen fibers, with modestly higher collagen density. Temporally, collagen fiber straightness and length changed late in treatment (days 9 and 12), while width and density changed early (day 6) compared with control mice. Single-fiber collagen features calculated in CT-FIRE were the most sensitive to the changes among treatment groups compared with bulk collagen features.

Conclusions

Quantitative second-harmonic generation imaging can provide insight into collagen dynamics in vivo during immunotherapy, with key implications in improving immunotherapy response in melanoma and other cancers.

In vitro and in vivo Evaluation of Antifibrotic Properties of Verteporfin in a Composition of a Collagen Scaffold

Extensive skin damage requires specialized therapy that stimulates regeneration processes without scarring. The possibility of using combination of a collagen gel application as a wound dressing and fibroblast attractant with verteporfin as an antifibrotic agent was examined in vivo and in vitro. In vitro effects of verteporfin on viability and myofibroblast markers expression were evaluated using fibroblasts isolated from human scar tissue. In vivo the collagen gel and verteporfin (individually and in combination) were applied into the wound to investigate scarring during skin regeneration: deviations in skin layer thickness, collagen synthesis, and extracellular matrix fibers were characterized. The results indicate that verteporfin reduces fibrotic phenotype by suppressing expression of the contractile protein Sm22α without inducing cell death. However, administration of verteporfin in combination with the collagen gel disrupts its ability to direct wound healing in a scarless manner, which may be related to incompatibility of the mechanisms by which collagen and verteporfin control regeneration.

Characterisation and correction of polarisation effects in fluorescently labelled fibres

Many biological structures take the form of fibres and filaments, and quantitative analysis of fibre organisation is important for understanding their functions in both normal physiological conditions and disease. In order to visualise these structures, fibres can be fluorescently labelled and imaged, with specialised image analysis methods available for quantifying the degree and strength of fibre alignment. Here we show that fluorescently labelled fibres can display polarised emission, with the strength of this effect varying depending on structure and fluorophore identity. This can bias automated analysis of fibre alignment and mask the true underlying structural organisation. We present a method for quantifying and correcting these polarisation effects without requiring polarisation-resolved microscopy and demonstrate its efficacy when applied to images of fluorescently labelled collagen gels, allowing for more reliable characterisation of fibre microarchitecture.

Host response during unresolved urinary tract infection alters female mammary tissue homeostasis through collagen deposition and TIMP1

Exposure to pathogens throughout a lifetime influences immunity and organ function. Here, we explore how the systemic host-response to bacterial urinary tract infection (UTI) induces tissue-specific alterations to the mammary gland. Utilizing a combination of histological tissue analysis, single cell transcriptomics, and flow cytometry, we identify that mammary tissue from UTI-bearing mice displays collagen deposition, enlarged ductal structures, ductal hyperplasia with atypical epithelial transcriptomes and altered immune composition. Bacterial cells are absent in the mammary tissue and blood of UTI-bearing mice, therefore, alterations to the distal mammary tissue are mediated by the systemic host response to local infection. Furthermore, broad spectrum antibiotic treatment resolves the infection and restores mammary cellular and tissue homeostasis. Systemically, unresolved UTI correlates with increased plasma levels of the metalloproteinase inhibitor, TIMP1, which controls extracellular matrix remodeling and neutrophil function. Treatment of nulliparous and post-lactation UTI-bearing female mice with a TIMP1 neutralizing antibody, restores mammary tissue normal homeostasis, thus providing evidence for a link between the systemic host response during UTI and mammary gland alterations.

Distribution of smooth muscle actin and collagen in superficial peritoneal endometriotic lesions varies from the surrounding microenvironment

RESEARCH QUESTION

Do different subtypes of superficial peritoneal endometriotic lesions exist, based on the presence and morphology of smooth muscle, collagen fibres and immune cell populations?

DESIGN

A retrospective cohort study of 24 patients, from across the menstrual cycle, with surgically and histologically confirmed endometriosis. Immunofluorescence was used to delineate the CD10 stromal area of lesions (n = 271 lesions from 67 endometriotic biopsies), and then smooth muscle actin (SMA) positive tissue and immune cell populations (CD45+ and CD68+) were quantified within and adjacent to these lesions. Second harmonic generation microscopy was used to evaluate the presence and morphology of type-1 collagen fibres within and surrounding lesions.

RESULTS

Overall, immune cell numbers and the area of SMA and collagen within endometriotic lesions tended to be low, but a spectrum of presentations significantly varied, particularly in the adjacent tissue microenvironment, based on lesion locations, the morphology of endometriotic gland profiles, or both. Lesions in which collagen fibres formed well aligned capsules around the CD10+ stromal border were identified compared with lesions in which collagen fibre distribution was random. Considerable inter- and intra-patient variability in the morphology of SMA and collagen was observed within and surrounding lesions.

CONCLUSION

These data demonstrate considerable diversity in the presence of immune cells and morphology of SMA and collagen within, but even more so, surrounding endometriotic lesions, even within individual patients. This heterogeneity, especially within individual patients, presents a challenge to incorporating these cell and tissue types into any new endometriosis classification systems or prognostic approaches.

Novel bisphosphonate-based cathepsin K-triggered compound targets the enthesis without impairing soft tissue-to-bone healing

Background: Osteoadsorptive fluorogenic sentinel 3 (OFS-3) is a recently described compound that contains a bone-targeting bisphosphonate (BP) and cathepsin K (Ctsk)-triggered fluorescence signal. A prior study in a murine Achilles repair model demonstrated its effectiveness at targeting the site of tendon-to-bone repair, but the intrinsic effect of this novel bisphosphonate chaperone on tendon-to-bone healing has not been previously explored. We hypothesized that application of this bisphosphonate-fluorophore cargo conjugate would not affect the biomechanical properties or histologic appearance of tendon-bone repairs. Materials and Methods: Right hindlimb Achilles tendon-to-bone repair was performed on 12-week old male mice. Animals were divided into 2 groups of 18 each: 1) Achilles repair with OFS-3 applied directly to the repair site prior to closure, and 2) Achilles repair with saline applied prior to closure. Repaired hindlimbs from 12 animals per group were harvested at 6 weeks for biomechanical analysis with a custom 3D-printed jig. At 4 and 6 weeks, repaired hindlimbs from the remaining animals were assessed histologically using H&E, immunohistochemistry (IHC) staining for the presence of Ctsk, and second harmonic generation (SHG) imaging to evaluate collagen fibers. Results: At 6 weeks, there was no significant difference in failure load, stiffness, toughness, or displacement to failure between repaired hindlimbs that received OFS-3 versus saline. There was no difference in tissue healing on H&E or Ctsk staining on immunohistochemistry between animals that received OFS-3 versus saline. Finally, second harmonic generation imaging demonstrated no difference in collagen fiber parameters between the two groups. Conclusion: OFS-3 did not significantly affect the biomechanical properties or histologic appearance of murine Achilles tendon-to-bone repairs. This study demonstrates that OFS-3 can target the site of tendon-to-bone repair without causing intrinsic negative effects on healing. Further development of this drug delivery platform to target growth factors to the site of tendon-bone repair is warranted.

Collagen organization and structure in FLBN5-/- mice using label-free microscopy: implications for pelvic organ prolapse

Pelvic organ prolapse (POP) is a gynecological disorder described by the descent of superior pelvic organs into or out of the vagina as a consequence of disrupted muscles and tissue. A thorough understanding of the etiology of POP is limited by the availability of clinically relevant samples, restricting longitudinal POP studies on soft-tissue biomechanics and structure to POP-induced models such as fibulin-5 knockout (FBLN5-/-) mice. Despite being a principal constituent in the extracellular matrix, little is known about structural perturbations to collagen networks in the FBLN5-/- mouse cervix. We identify significantly different collagen network populations in normal and prolapsed cervical cross-sections using two label-free, nonlinear microscopy techniques. Collagen in the prolapsed mouse cervix tends to be more isotropic, and displays reduced alignment persistence via 2-D Fourier Transform analysis of images acquired using second harmonic generation microscopy. Furthermore, coherent Raman hyperspectral imaging revealed elevated disorder in the secondary structure of collagen in prolapsed tissues. Our results underscore the need for in situ multimodal monitoring of collagen organization to improve POP predictive capabilities.

Leader cells mechanically respond to aligned collagen architecture to direct collective migration

Leader cells direct collective migration through sensing cues in their microenvironment to determine migration direction. The mechanism by which leader cells sense the mechanical cue of organized matrix architecture culminating in a mechanical response is not well defined. In this study, we investigated the effect of organized collagen matrix fibers on leader cell mechanics and demonstrate that leader cells protrude along aligned fibers resulting in an elongated phenotype of the entire cluster. Further, leader cells show increased mechanical interactions with their nearby matrix compared to follower cells, as evidenced by increased traction forces, increased and larger focal adhesions, and increased expression of integrin-α2. Together our results demonstrate changes in mechanical matrix cues drives changes in leader cell mechanoresponse that is required for directional collective migration. Our findings provide new insights into two fundamental components of carcinogenesis, namely invasion and metastasis.

MATLAB-Based Algorithm and Software for Analysis of Wavy Collagen Fibers

Knowledge of soft tissue fiber structure is necessary for accurate characterization and modeling of their mechanical response. Fiber configuration and structure informs both our understanding of healthy tissue physiology and of pathological processes resulting from diseased states. This study develops an automatic algorithm to simultaneously estimate fiber global orientation, abundance, and waviness in an investigated image. To our best knowledge, this is the first validated algorithm which can reliably separate fiber waviness from its global orientation for considerably wavy fibers. This is much needed feature for biological tissue characterization. The algorithm is based on incremental movement of local regions of interest (ROI) and analyzes two-dimensional images. Pixels belonging to the fiber are identified in the ROI, and ROI movement is determined according to local orientation of fiber within the ROI. The algorithm is validated with artificial images and ten images of porcine trachea containing wavy fibers. In each image, 80-120 fibers were tracked manually to serve as verification. The coefficient of determination R2 between curve lengths and histograms documenting the fiber waviness and global orientation were used as metrics for analysis. Verification-confirmed results were independent of image rotation and degree of fiber waviness, with curve length accuracy demonstrated to be below 1% of fiber curved length. Validation-confirmed median and interquartile range of R2, respectively, were 0.90 and 0.05 for curved length, 0.92 and 0.07 for waviness, and 0.96 and 0.04 for global orientation histograms. Software constructed from the proposed algorithm was able to track one fiber in about 1.1 s using a typical office computer. The proposed algorithm can reliably and accurately estimate fiber waviness, curve length, and global orientation simultaneously, moving beyond the limitations of prior methods.

Stromal cells regulate mechanics of tumour spheroid

The remarkable contractility and force generation ability exhibited by cancer cells empower them to overcome the resistance and steric hindrance presented by a three-dimensional, interconnected matrix. Cancer cells disseminate by actively remodelling and deforming their extracellular matrix (ECM). The process of tumour growth and its ECM remodelling have been extensively studied, but the effect of the cellular tumour microenvironment (TME) has been ignored in most studies that investigated tumour-cell-mediated ECM deformations and realignment. This study reports the integration of stromal cells in spheroid contractility assays that impacts the ECM remodelling and invasion abilities of cancer spheroids. To investigate this, we developed a novel multilayer in vitro assay that incorporates stromal cells and quantifies the contractile deformations that tumour spheroids exert on the ECM. We observed a negative correlation between the spheroid invasion potential and the levels of collagen deformation. The presence of stromal cells significantly increased cancer cell invasiveness and altered the cancer cells' ability to deform and realign collagen gel, due to upregulation of proinflammatory cytokines. Interestingly, this was observed consistently in both metastatic and non-metastatic cancer cells. Our findings contribute to a better understanding of the vital role played by the cellular TME in regulating the invasive outgrowth of cancer cells and underscore the potential of utilising matrix deformation measurements as a biophysical marker for evaluating invasiveness and informing targeted therapeutic opportunities.

Quantifying in vivo collagen reorganization during immunotherapy in murine melanoma with second harmonic generation imaging

Significance

Increased collagen linearization and deposition during tumorigenesis can impede immune cell infiltration and lead to tumor metastasis. Although melanoma is well studied in immunotherapy research, studies that quantify collagen changes during melanoma progression and treatment are lacking.

Aim

Image in vivo collagen in preclinical melanoma models during immunotherapy and quantify the collagen phenotype in treated and control mice.

Approach

Second harmonic generation imaging of collagen was performed in mouse melanoma tumors in vivo over a treatment time-course. Animals were treated with a curative radiation and immunotherapy combination. Collagen morphology was quantified over time at an image and single fiber level using CurveAlign and CT-FIRE software.

Results

In immunotherapy-treated mice, collagen reorganized toward a healthy phenotype, including shorter, wider, curlier collagen fibers, with modestly higher collagen density. Temporally, collagen fiber straightness and length changed late in treatment (Day 9 and 12) while width and density changed early (Day 6) compared to control mice. Single fiber level collagen analysis was most sensitive to the changes between treatment groups compared to image level analysis.

Conclusions

Quantitative second harmonic generation imaging can provide insight into collagen dynamics in vivo during immunotherapy, with key implications in improving immunotherapy response in melanoma and other cancers.

A deep learning-based stripe self-correction method for stitched microscopic images

Stitched fluorescence microscope images inevitably exist in various types of stripes or artifacts caused by uncertain factors such as optical devices or specimens, which severely affects the image quality and downstream quantitative analysis. Here, we present a deep learning-based Stripe Self-Correction method, so-called SSCOR. Specifically, we propose a proximity sampling scheme and adversarial reciprocal self-training paradigm that enable SSCOR to utilize stripe-free patches sampled from the stitched microscope image itself to correct their adjacent stripe patches. Comparing to off-the-shelf approaches, SSCOR can not only adaptively correct non-uniform, oblique, and grid stripes, but also remove scanning, bubble, and out-of-focus artifacts, achieving the state-of-the-art performance across different imaging conditions and modalities. Moreover, SSCOR does not require any physical parameter estimation, patch-wise manual annotation, or raw stitched information in the correction process. This provides an intelligent prior-free image restoration solution for microscopists or even microscope companies, thus ensuring more precise biomedical applications for researchers.

Effect of the Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats

The objective of this study is to clarify the effect of restoring the lowered masticatory muscle functional pressure and correcting bilateral differences in masticatory muscle functional pressure on jawbone growth during growth and development with a quantitative evaluation of the changes in the micro/nanostructural characteristics of entheses. Male Wistar rats aged 4 weeks were divided into an experimental group injected with a botulinum toxin serotype A (BoNT/A) formulation to reduce muscle function (BTX group) and a control group (CTRL group). They were euthanised after 6, 8, 10, 12, and 16 weeks after measuring the difference between the midline of the upper and lower incisors. The mandibles were harvested for histological examination, second harmonic generation imaging, and the quantitative evaluation of biological apatite (BAp) crystal alignment. The midline difference decreased with age in weeks. In rats from 6 weeks after BoNT/A administration to 12 weeks after administration, the collagen fibre bundle diameter was significantly smaller in the BTX group; the difference between the two groups decreased with increasing age. BAp crystal alignment was significantly different on the x-axis and the y-axis on the BTX group from 6 weeks after BoNT/A administration to 10 weeks after administration. Asymmetry of mandibular bone formation caused by load imbalance during growth could be corrected by the adjustment of the function of the masseter muscle on either side.

Prostate cancer tissue classification by multiphoton imaging, automated image analysis and machine learning

Prostate carcinoma, a slow-growing and often indolent tumour, is the second most commonly diagnosed cancer among men worldwide. The prognosis is mainly based on the Gleason system through prostate biopsy analysis. However, new treatment and monitoring strategies depend on a more precise diagnosis. Here, we present results by multiphoton imaging for prostate tumour samples from 120 patients that allow to obtain quantitative parameters leading to specific tumour aggressiveness signatures. An automated image analysis was developed to recognise and quantify stromal fibre and neoplastic cell regions in each image. The set of metrics was able to distinguish between non-neoplastic tissue and carcinoma areas by linear discriminant analysis and random forest with accuracy of 89% ± 3%, but between Gleason groups of only 46% ± 6%. The reactive stroma analysis improved the accuracy to 65% ± 5%, clearly demonstrating that stromal parameters should be considered as additional criteria for a more accurate diagnosis.

Nonlinear microscopy and deep learning classification for mammary gland microenvironment studies

Tumors, their microenvironment, and the mechanisms by which collagen morphology changes throughout cancer progression have recently been a topic of interest. Second harmonic generation (SHG) and polarization second harmonic (P-SHG) microscopy are label-free, hallmark methods that can highlight this alteration in the extracellular matrix (ECM). This article uses automated sample scanning SHG and P-SHG microscopy to investigate ECM deposition associated with tumors residing in the mammary gland. We show two different analysis approaches using the acquired images to distinguish collagen fibrillar orientation changes in the ECM. Lastly, we apply a supervised deep-learning model to classify naïve and tumor-bearing mammary gland SHG images. We benchmark the trained model using transfer learning with the well-known MobileNetV2 architecture. By fine-tuning the different parameters of these models, we show a trained deep-learning model that suits such a small dataset with 73% accuracy.

Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing

'Smart' bandages based on multimodal wearable devices could enable real-time physiological monitoring and active intervention to promote healing of chronic wounds. However, there has been limited development in incorporation of both sensors and stimulators for the current smart bandage technologies. Additionally, while adhesive electrodes are essential for robust signal transduction, detachment of existing adhesive dressings can lead to secondary damage to delicate wound tissues without switchable adhesion. Here we overcome these issues by developing a flexible bioelectronic system consisting of wirelessly powered, closed-loop sensing and stimulation circuits with skin-interfacing hydrogel electrodes capable of on-demand adhesion and detachment. In mice, we demonstrate that our wound care system can continuously monitor skin impedance and temperature and deliver electrical stimulation in response to the wound environment. Across preclinical wound models, the treatment group healed ~25% more rapidly and with ~50% enhancement in dermal remodeling compared with control. Further, we observed activation of proregenerative genes in monocyte and macrophage cell populations, which may enhance tissue regeneration, neovascularization and dermal recovery.

Quantitative collagen analysis using second harmonic generation images for the detection of basal cell carcinoma with ex vivo multiphoton microscopy

Basal cell carcinoma (BCC) is the most common skin cancer, and its incidence is rising. Millions of benign biopsies are performed annually for BCC diagnosis, increasing morbidity, and healthcare costs. Non-invasive in vivo technologies such as multiphoton microscopy (MPM) can aid in diagnosing BCC, reducing the need for biopsies. Furthermore, the second harmonic generation (SHG) signal generated from MPM can classify and prognosticate cancers based on extracellular matrix changes, especially collagen type I. We explored the potential of MPM to differentiate collagen changes associated with different BCC subtypes compared to normal skin structures and benign lesions. Quantitative analysis such as frequency band energy analysis in Fourier domain, CurveAlign and CT-FIRE fibre analysis was performed on SHG images from 52 BCC and 12 benign lesions samples. Our results showed that collagen distribution is more aligned surrounding BCCs nests compared to the skin's normal structures (p < 0.001) and benign lesions (p < 0.001). Also, collagen was orientated more parallelly surrounding indolent BCC subtypes (superficial and nodular) versus those with more aggressive behaviour (infiltrative BCC) (p = 0.021). In conclusion, SHG signal from type I collagen can aid not only in the diagnosis of BCC but could be useful for prognosticating these tumors. Our initial results are limited to a small number of samples, requiring large-scale studies to validate them. These findings represent the groundwork for future in vivo MPM for diagnosis and prognosis of BCC.

Phase-specific signatures of wound fibroblasts and matrix patterns define cancer-associated fibroblast subtypes

Healing wounds and cancers present remarkable cellular and molecular parallels, but the specific roles of the healing phases are largely unknown. We developed a bioinformatics pipeline to identify genes and pathways that define distinct phases across the time-course of healing. Their comparison to cancer transcriptomes revealed that a resolution phase wound signature is associated with increased severity in skin cancer and enriches for extracellular matrix-related pathways. Comparisons of transcriptomes of early- and late-phase wound fibroblasts vs skin cancer-associated fibroblasts (CAFs) identified an "early wound" CAF subtype, which localizes to the inner tumor stroma and expresses collagen-related genes that are controlled by the RUNX2 transcription factor. A "late wound" CAF subtype localizes to the outer tumor stroma and expresses elastin-related genes. Matrix imaging of primary melanoma tissue microarrays validated these matrix signatures and identified collagen- vs elastin-rich niches within the tumor microenvironment, whose spatial organization predicts survival and recurrence. These results identify wound-regulated genes and matrix patterns with prognostic potential in skin cancer.

Discoidin domain receptor-2 enhances secondary alveolar septation in mice by activating integrins and modifying focal adhesions

The extracellular matrix (ECM) of the pulmonary parenchyma must maintain the structural relationships among resident cells during the constant distortion imposed by respiration. This dictates that both the ECM and cells adapt to changes in shape, while retaining their attachment. Membrane-associated integrins and discoidin domain receptors (DDR) bind collagen and transmit signals to the cellular cytoskeleton. Although the contributions of DDR2 to collagen deposition and remodeling during osseous development are evident, it is unclear how DDR2 contributes to lung development. Using mice (smallie, Slie/Slie, DDR2Δ) bearing a spontaneous inactivating deletion within the DDR2 coding region, we observed a decrease in gas-exchange surface area and enlargement of alveolar ducts. Compared with fibroblasts isolated from littermate controls, DDR2Δ fibroblasts, spread more slowly, developed fewer lamellipodia, and were less responsive to the rigidity of neighboring collagen fibers. Activated β1-integrin (CD29) was reduced in focal adhesions (FA) of DDR2Δ fibroblasts, less phospho-zyxin localized to and fewer FA developed over ventral actin stress fibers, and the adhesions had a lower aspect ratio compared with controls. However, DDR2 deletion did not reduce cellular displacement of the ECM. Our findings indicate that DDR2, in concert with collagen-binding β1-integrins, regulates the timing and location of focal adhesion formation and how lung fibroblasts respond to ECM rigidity. Reduced rigidity sensing and mechano-responsiveness may contribute to the distortion of alveolar ducts, where the fiber cable-network is enriched and tensile forces are concentrated. Strategies targeting DDR2 could help guide fibroblasts to locations where tensile forces organize parenchymal repair.

Label-free optical imaging of cell function and collagen structure for cell-based therapies

Cell-based therapies harness functional cells or tissues to mediate healing and treat disease. Assessment of cellular therapeutics requires methods that are non-destructive to ensure therapies remain viable and uncontaminated for use in patients. Optical imaging of endogenous collagen, by second-harmonic generation, and the metabolic coenzymes NADH and FAD, by autofluorescence microscopy, provides tissue structure and cellular information. Here, we review applications of label-free nonlinear optical imaging of cellular metabolism and collagen second-harmonic generation for assessing cell-based therapies. Additionally, we discuss the potential of label-free imaging for quality control of cell-based therapies, as well as the current limitations and potential future directions of label-free imaging technologies.

microRNA-33 deficiency in macrophages enhances autophagy, improves mitochondrial homeostasis, and protects against lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal disease. Recent findings have shown a marked metabolic reprogramming associated with changes in mitochondrial homeostasis and autophagy during pulmonary fibrosis. The microRNA-33 (miR-33) family of microRNAs (miRNAs) encoded within the introns of sterol regulatory element binding protein (SREBP) genes are master regulators of sterol and fatty acid (FA) metabolism. miR-33 controls macrophage immunometabolic response and enhances mitochondrial biogenesis, FA oxidation, and cholesterol efflux. Here, we show that miR-33 levels are increased in bronchoalveolar lavage (BAL) cells isolated from patients with IPF compared with healthy controls. We demonstrate that specific genetic ablation of miR-33 in macrophages protects against bleomycin-induced pulmonary fibrosis. The absence of miR-33 in macrophages improves mitochondrial homeostasis and increases autophagy while decreasing inflammatory response after bleomycin injury. Notably, pharmacological inhibition of miR-33 in macrophages via administration of anti-miR-33 peptide nucleic acids (PNA-33) attenuates fibrosis in different in vivo and ex vivo mice and human models of pulmonary fibrosis. These studies elucidate a major role of miR-33 in macrophages in the regulation of pulmonary fibrosis and uncover a potentially novel therapeutic approach to treat this disease.

Hardware-software co-design of an open-source automatic multimodal whole slide histopathology imaging system

Significance

Advanced digital control of microscopes and programmable data acquisition workflows have become increasingly important for improving the throughput and reproducibility of optical imaging experiments. Combinations of imaging modalities have enabled a more comprehensive understanding of tissue biology and tumor microenvironments in histopathological studies. However, insufficient imaging throughput and complicated workflows still limit the scalability of multimodal histopathology imaging.

Aim

We present a hardware-software co-design of a whole slide scanning system for high-throughput multimodal tissue imaging, including brightfield (BF) and laser scanning microscopy.

Approach

The system can automatically detect regions of interest using deep neural networks in a low-magnification rapid BF scan of the tissue slide and then conduct high-resolution BF scanning and laser scanning imaging on targeted regions with deep learning-based run-time denoising and resolution enhancement. The acquisition workflow is built using Pycro-Manager, a Python package that bridges hardware control libraries of the Java-based open-source microscopy software Micro-Manager in a Python environment.

Results

The system can achieve optimized imaging settings for both modalities with minimized human intervention and speed up the laser scanning by an order of magnitude with run-time image processing.

Conclusions

The system integrates the acquisition pipeline and data analysis pipeline into a single workflow that improves the throughput and reproducibility of multimodal histopathological imaging.

Three-dimensional analysis of load-dependent changes in the orientation of dermal collagen fibers in human skin: A pilot study

The availability of quantitative structural data on the orientation of collagen fibers is of crucial importance for understanding the behavior of connective tissues. These fibers can be visualized using a variety of imaging techniques, including second harmonic generation (SHG) microscopy. However, characterization of the collagen network requires the accurate extraction of parameters from imaging data. To this end, several automated processes have been developed to identify the preferred orientation of collagen fibers. Common methods include fast Fourier transforms and curvelet transforms, but these tools are mostly used to infer a single preferred orientation. The purpose of this pilot study was to develop an easy procedure for comprehensively comparing multiple human skin samples with the goal of analyzing load-dependent changes via SHG microscopy. We created a 3D model based upon 2D image stacks that provide fiber orientation data perpendicular and parallel to the plane of the epidermis. The SHG images were analyzed by CurveAlign to obtain angle histogram plots containing information about the multiple fiber orientations in each single image. Subsequently, contour plots of the angle histogram intensities were created to provide a useful visual plotting method to clearly show the anomalies in the angle histograms in all samples. Our results provided additional details on how the collagen network carries a load. In fact, analysis of SHG images indicated that increased stretch was accompanied by an increase in the alignment of fibers in the loading direction. Moreover, these images demonstrated that more than one type of preferred orientation is present. In particular, the 3D network of fibers appears to have two preferred orientations in the planes both perpendicular and parallel to the plane of the epidermis.

Correcting dilated cardiomyopathy with fibroblast-targeted p38 deficiency

Inherited mutations in contractile and structural genes, which decrease cardiomyocyte tension generation, are principal drivers of dilated cardiomyopathy (DCM)- the leading cause of heart failure 1,2 . Progress towards developing precision therapeutics for and defining the underlying determinants of DCM has been cardiomyocyte centric with negligible attention directed towards fibroblasts despite their role in regulating the best predictor of DCM severity, cardiac fibrosis 3,4 . Given that failure to reverse fibrosis is a major limitation of both standard of care and first in class precision therapeutics for DCM, this study examined whether cardiac fibroblast-mediated regulation of the heart's material properties is essential for the DCM phenotype. Here we report in a mouse model of inherited DCM that prior to the onset of fibrosis and dilated myocardial remodeling both the myocardium and extracellular matrix (ECM) stiffen from switches in titin isoform expression, enhanced collagen fiber alignment, and expansion of the cardiac fibroblast population, which we blocked by genetically suppressing p38α in cardiac fibroblasts. This fibroblast-targeted intervention unexpectedly improved the primary cardiomyocyte defect in contractile function and reversed ECM and dilated myocardial remodeling. Together these findings challenge the long-standing paradigm that ECM remodeling is a secondary complication to inherited defects in cardiomyocyte contractile function and instead demonstrate cardiac fibroblasts are essential contributors to the DCM phenotype, thus suggesting DCM-specific therapeutics will require fibroblast-specific strategies.

Anagen hair follicles transplanted into mature human scars remodel fibrotic tissue

Despite the substantial impact of skin scarring on patients and the healthcare system, there is a lack of strategies to prevent scar formation, let alone methods to remodel mature scars. Here, we took a unique approach inspired by how healthy hairbearing skin undergoes physiological remodelling during the regular cycling of hair follicles. In this pilot clinical study, we tested if hair follicles transplanted into human scars can facilitate tissue regeneration and actively remodel fibrotic tissue, similar to how they remodel the healthy skin. We collected full-thickness skin biopsies and compared the morphology and transcriptional signature of fibrotic tissue before and after transplantation. We found that hair follicle tranplantation induced an increase in the epidermal thickness, interdigitation of the epidermal-dermal junction, dermal cell density, and blood vessel density. Remodelling of collagen type I fibres reduced the total collagen fraction, the proportion of thick fibres, and their alignment. Consistent with these morphological changes, we found a shift in the cytokine milieu of scars with a long-lasting inhibition of pro-fibrotic factors TGFβ1, IL13, and IL-6. Our results show that anagen hair follicles can attenuate the fibrotic phenotype, providing new insights for developing regenerative approaches to remodel mature scars.

Assessment of Collagen in Translational Models of Lung Research

The extracellular matrix (ECM) plays an important role in lung health and disease. Collagen is the main component of the lung ECM, widely used for the establishment of in vitro and organotypic models of lung disease, and as scaffold material of general interest for the field of lung bioengineering. Collagen also is the main readout for fibrotic lung disease, where collagen composition and molecular properties are drastically changed and ultimately result in dysfunctional "scarred" tissue. Because of the central role of collagen in lung disease, quantification, determination of molecular properties, and three-dimensional visualization of collagen is important for both development and characterization of translational models of lung research. In this chapter, we provide a comprehensive overview on the various methodologies currently available for quantification and characterization of collagen including their detection principles, advantages, and disadvantages.

Characteristics of Collagen Changes in Small Intestine Anastomoses Induced by High-Frequency Electric Field Welding

High-frequency electric field welding-induced tissue fusion has been explored as an advanced surgical method for intestinal anastomoses; however, intrinsic mechanisms remain unclear. The aim of this study was to investigate microcosmic changes of collagen within the fusion area, with various parameters. Ex vivo small intestine was fused with mucosa-mucosa. Four levels of compressive pressure (100 kPa, 150 kPa, 200 kPa, 250 kPa) were applied for 10 s in order to fuse the colons under a power level of 140 W. Then, collagen fibers of the fusion area were examined by fibrillar collagen alignment and TEM. Three levels of power (90 W, 110 W, 140 W) and three levels of time (5 s, 10 s, 20 s) were applied in order to fuse colons at 250 kPa, and then collagen within the fusion area was examined by Raman spectroscopy. Fibrillar collagen alignment analysis showed that with the increase in compression pressure, alignment of the collagen in the fusion area gradually increased, and the arrangement of collagen fibers tended to be consistent, which was conducive to the adhesion of collagen fibers. TEM showed that pressure changed the distribution and morphology of collagen fibers. Raman spectroscopy showed that increased power and time within a certain range contributed to collagen cross linking. Peak positions of amide I band and amide III band changed. These results suggested that higher power and a longer amount of time resulted in a decrease in non-reducible cross links and an increase in reducible cross links. Compression pressure, power, and time can affect the state of collagen, but the mechanisms are different. Compressive pressure affected the state of collagen by changing its orientation; power and time denatured collagen by increasing temperature and improved the reducible cross linking of collagen to promote tissue fusion.

Physiological Impact of a Synthetic Elastic Protein in Arterial Diseases Related to Alterations of Elastic Fibers: Effect on the Aorta of Elastin-Haploinsufficient Male and Female Mice

Elastic fibers, made of elastin (90%) and fibrillin-rich microfibrils (10%), are the key extracellular components, which endow the arteries with elasticity. The alteration of elastic fibers leads to cardiovascular dysfunctions, as observed in elastin haploinsufficiency in mice (Eln+/-) or humans (supravalvular aortic stenosis or Williams-Beuren syndrome). In Eln+/+ and Eln+/- mice, we evaluated (arteriography, histology, qPCR, Western blots and cell cultures) the beneficial impact of treatment with a synthetic elastic protein (SEP), mimicking several domains of tropoelastin, the precursor of elastin, including hydrophobic elasticity-related domains and binding sites for elastin receptors. In the aorta or cultured aortic smooth muscle cells from these animals, SEP treatment induced a synthesis of elastin and fibrillin-1, a thickening of the aortic elastic lamellae, a decrease in wall stiffness and/or a strong trend toward a reduction in the elastic lamella disruptions in Eln+/- mice. SEP also modified collagen conformation and transcript expressions, enhanced the aorta constrictive response to phenylephrine in several animal groups, and, in female Eln+/- mice, it restored the normal vasodilatory response to acetylcholine. SEP should now be considered as a biomimetic molecule with an interesting potential for future treatments of elastin-deficient patients with altered arterial structure/function.

Matrix produced by diseased cardiac fibroblasts affects early myotube formation and function

The extracellular matrix (ECM) provides both physical and chemical cues that dictate cell function and contribute to muscle maintenance. Muscle cells require efficient mitochondria to satisfy their high energy demand, however, the role the ECM plays in moderating mitochondrial function is not clear. We hypothesized that the ECM produced by stromal cells with mitochondrial dysfunction (Barth syndrome, BTHS) provides cues that contribute to metabolic dysfunction independent of muscle cell health. To test this, we harnessed the ECM production capabilities of human pluripotent stem-cell-derived cardiac fibroblasts (hPSC-CFs) from healthy and BTHS patients to fabricate cell-derived matrices (CDMs) with controlled topography, though we found that matrix composition from healthy versus diseased cells influenced myotube formation independent of alignment cues. To further investigate the effects of matrix composition, we then examined the influence of healthy- and BTHS-derived CDMs on myotube formation and metabolic function. We found that BTHS CDMs induced lower fusion index, lower ATP production, lower mitochondrial membrane potential, and higher ROS generation than the healthy CDMs. These findings imply that BTHS-derived ECM alone contributes to myocyte dysfunction in otherwise healthy cells. Finally, to investigate potential mechanisms, we defined the composition of CDMs produced by hPSC-CFs from healthy and BTHS patients using mass spectrometry and identified 15 ECM and related proteins that were differentially expressed in the BTHS-CDM compared to healthy CDM. Our results highlight that ECM composition affects skeletal muscle formation and metabolic efficiency in otherwise healthy cells, and our methods to generate patient-specific CDMs are a useful tool to investigate the influence of the ECM on disease progression and to investigate variability among diseased patients. STATEMENT OF SIGNIFICANCE: Muscle function requires both efficient metabolism to generate force and structured extracellular matrix (ECM) to transmit force, and we sought to examine the interactions between metabolism and ECM when metabolic disease is present. We fabricated patient-specific cell derived matrices (CDMs) with controlled topographic features to replicate the composition of healthy and mitochondrial-diseased (Barth syndrome) ECM. We found that disease-derived ECM negatively affects metabolic function of otherwise healthy myoblasts, and we identified several proteins in disease-derived ECM that may be mediating this dysfunction. We anticipate that our patient-specific CDM system could be fabricated with other topographies and cell types to study cell functions and diseases of interest beyond mitochondrial dysfunction and, eventually, be applied toward personalized medicine.

Tissue Stromal Vascular Fraction Improves Early Scar Healing: A Prospective Randomized Multicenter Clinical Trial

BACKGROUND

Wound healing and scar formation depends on a plethora of factors. Given the impact of abnormal scar formation, interventions aimed to improve scar formation would be most advantageous. The tissue stromal vascular fraction (tSVF) of adipose tissue is composed of a heterogenous mixture of cells embedded in extracellular matrix. It contains growth factors and cytokines involved in wound-healing processes, eg, parenchymal proliferation, inflammation, angiogenesis, and matrix remodeling.

OBJECTIVES

The aim of this study was to investigate the hypothesis that tSVF reduces postsurgical scar formation.

METHODS

This prospective, double-blind, placebo-controlled, randomized trial was conducted between 2016 and 2020. Forty mammoplasty patients were enrolled and followed for 1 year. At the end of the mammoplasty procedure, all patients received tSVF in the lateral 5 cm of the horizontal scar of 1 breast and a placebo injection in the contralateral breast to serve as an intrapatient control. Primary outcome was scar quality measure by the Patient and Observer Scar Assessment Scale (POSAS). Secondary outcomes were obtained from photographic evaluation and histologic analysis of scar tissue samples.

RESULTS

Thirty-four of 40 patients completed follow-up. At 6 months postoperation, injection of tSVF had significantly improved postoperative scar appearance as assessed by the POSAS questionnaire. No difference was observed at 12 months postoperation. No improvement was seen based on the evaluation of photographs and histologic analysis of postoperative scars between both groups.

CONCLUSIONS

Injection of tSVF resulted in improved wound healing and reduced scar formation at 6 months postoperation, without any noticeable advantageous effects seen at 12 months.

LEVEL OF EVIDENCE: 2

Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting

Burns and other traumatic injuries represent a substantial biomedical burden. The current standard of care for deep injuries is autologous split-thickness skin grafting (STSG), which frequently results in contractures, abnormal pigmentation, and loss of biomechanical function. Currently, there are no effective therapies that can prevent fibrosis and contracture after STSG. Here, we have developed a clinically relevant porcine model of STSG and comprehensively characterized porcine cell populations involved in healing with single-cell resolution. We identified an up-regulation of proinflammatory and mechanotransduction signaling pathways in standard STSGs. Blocking mechanotransduction with a small-molecule focal adhesion kinase (FAK) inhibitor promoted healing, reduced contracture, mitigated scar formation, restored collagen architecture, and ultimately improved graft biomechanical properties. Acute mechanotransduction blockade up-regulated myeloid CXCL10-mediated anti-inflammation with decreased CXCL14-mediated myeloid and fibroblast recruitment. At later time points, mechanical signaling shifted fibroblasts toward profibrotic differentiation fates, and disruption of mechanotransduction modulated mesenchymal fibroblast differentiation states to block those responses, instead driving fibroblasts toward proregenerative, adipogenic states similar to unwounded skin. We then confirmed these two diverging fibroblast transcriptional trajectories in human skin, human scar, and a three-dimensional organotypic model of human skin. Together, pharmacological blockade of mechanotransduction markedly improved large animal healing after STSG by promoting both early, anti-inflammatory and late, regenerative transcriptional programs, resulting in healed tissue similar to unwounded skin. FAK inhibition could therefore supplement the current standard of care for traumatic and burn injuries.

Collagen type XIX regulates cardiac extracellular matrix structure and ventricular function

The cardiac extracellular matrix plays essential roles in homeostasis and injury responses. Although the role of fibrillar collagens have been thoroughly documented, the functions of non-fibrillar collagen members remain underexplored. These include a distinct group of non-fibrillar collagens, termed, fibril-associated collagens with interrupted triple helices (FACITs). Recent reports of collagen type XIX (encoded by Col19a1) expression in adult heart and evidence of its enhanced expression in cardiac ischemia suggest important functions for this FACIT in cardiac ECM structure and function. Here, we examined the cellular source of collagen XIX in the adult murine heart and evaluated its involvement in ECM structure and ventricular function. Immunodetection of collagen XIX in fractionated cardiovascular cell lineages revealed fibroblasts and smooth muscle cells as the primary sources of collagen XIX in the heart. Based on echocardiographic and histologic analyses, Col19a1 null (Col19a1N/N) mice exhibited reduced systolic function, thinning of left ventricular walls, and increased cardiomyocyte cross-sectional areas-without gross changes in myocardial collagen content or basement membrane morphology. Col19a1N/N cardiac fibroblasts had augmented expression of several enzymes involved in the synthesis and stability of fibrillar collagens, including PLOD1 and LOX. Furthermore, second harmonic generation-imaged ECM derived from Col19a1N/N cardiac fibroblasts, and transmission electron micrographs of decellularized hearts from Col19a1N/N null animals, showed marked reductions in fibrillar collagen structural organization. Col19a1N/N mice also displayed enhanced phosphorylation of focal adhesion kinase (FAK), signifying de-repression of the FAK pathway-a critical mediator of cardiomyocyte hypertrophy. Collectively, we show that collagen XIX, which had a heretofore unknown role in the mammalian heart, participates in the regulation of cardiac structure and function-potentially through modulation of ECM fibrillar collagen structural organization. Further, these data suggest that this FACIT may modify ECM superstructure via acting at the level of the fibroblast to regulate their expression of collagen synthetic and stabilization enzymes.