"Mechanical loads play a pivotal role in the growth, maintenance, remodeling, and disease onset in connective tissues. Harnessing the relationship between mechanical signals and how cells remodel their surrounding extracellular matrix would provide new insights into the fundamental processes of wound healing and fibrosis and also assist in the creation of custom-tailored tissue equivalents for use in regenerative medicine. In 3D tissue models, uniaxial cyclic stretch has been shown to stimulate the synthesis and crosslinking of collagen while increasing the matrix density, fiber alignment, stiffness, and tensile strength in the direction of principal stretch. Unfortunately, the profound fiber realignment in these systems render it difficult to differentiate between passive effects and cell-mediated remodeling. Further, these previous studies generally focus on a single level of stretch magnitude and duration, and they also investigate matrix remodeling under a homogeneous strain conditions. Therefore, these studies are not sufficient to establish key information regarding stretch-dependent remodeling for use in tissue engineering and also do not simulate the complex mechanical environment of connective tissue. We first developed a novel in vitro model system using equibiaxial stretch on fibrin gels (early models of wound healing) that enabled the isolation of mechanical effects on cell-mediated matrix remodeling. Using this system we demonstrated that in the absence of in-plane alignment, stretch stimulates fibroblasts to produce a stronger tissue by synthesizing collagen and condensing their surrounding matrix. We then developed dose-response curves for multiple aspects of tissue remodeling as a function of stretch magnitude and duration (intermittent versus continuous stretch). Our results indicate that both the magnitude and the duration per day of stretch are important factors in mechanically induced cell activity, as evidenced by dose-dependent responses of several remodeling metrics in response to these two parameters (UTS, matrix stiffness, collagen content, cell number). In addition, we found that cellularity, collagen content, and resistance to tension increased when the tissues were mechanically loaded intermittently as opposed to continuously. Finally, we developed a novel model system that produces non-homogeneous strain distribution, allowing for the simultaneous study of strain gradients, strain anisotropy, and strain magnitude in 2D and 3D. Establishing a system that produces complex strain distributions provides a more accurate model of the mechanical conditions found in connective tissue, and also allows for the investigation of cellular adaptations to a changing mechanical environment. "

Extracellular microenvironment, including its components and biophysical parameters such as matrix structure and stiffness, is a crucial determinant of cellular function. There exists interdependency between cellular behaviors and the extracellular matrix (ECM), whereby cells are constantly sensing and modifying their surroundings in response to physical stress or during processes like wound repair, cancer cell invasion, and morphogenesis, to create an environment which supports adaptation. To date, knowledge of the distinct regulatory mechanisms of this complex relationship is little, while the urge is evident as it plays a significant role in understanding tissue remodeling. Cells are observed to align with the parallel arrays of collagen fibrils found in tissues such as bone, tendon, and cornea, suggesting the importance of ordered matrices in defining cell functions. In this study, epitaxial growths of ordered two-dimensional collagen matrices were created, with parallelly aligned fibrils on muscovite mica, and novel triangular pattern matrix on phlogopite mica. Using Fluorescence and Atomic Force Microscopy, we were able to observe cell polarization along with stress fiber formation and matrix deformation at high resolution. Cells were observed to be able to penetrate between collagen fibrils and generate traction anisotropically to polarize. These ordered collagen matrices serve as an excellent model to study cellular remodeling of ECM in vitro, in which this fundamental apprehension of cell-matrix relationship is of crucial importance to manipulate the system and obtain desired cell functions.

No description available.

Introduction: Articular cartilage (AC) is a low friction load bearing material found in synovial joints. The natural repair of damaged tissue is difficult and often requires surgical intervention. With large defects it becomes necessary to match the original tissue geometry. We hypothesized that localized collagen (COL) and/or proteoglycan (PG) remodeling occurs during AC spherical reshaping. The objective of this study was to determine the presence, magnitude and depth dependence of COL and PG remodeling that accompanies AC reshaping. Methods: Full thickness AC blocks (7x7 mm2 surface area) were harvested from the ridges of the patellofemoral groove of immature (1-3 week old) bovine knees. The top 0-1 mm with intact articular surface was sliced off with a vibrating microtome. A 6 mm diameter disk was punched out of the slice and the most anterior edge was notched to mark directionality. The final sample was a 1 mm thick, 6 mm diameter disk with a notch on the most anterior edge. Samples were either not treated (day 0; D0) or allowed to free swell overnight in 20% FBS. Then cultured samples were placed in culture with 20% FBS in either free swelling (FS), static bending with the articular surface concave (concave) or in static bending with the articular surface convex (convex). Wet-weight and opening angle were measured before and 2 hours after removal from culture. Following culture, samples were cut in half in the anterior posterior direction. One half of each sample was frozen and later analyzed for PG, COL and cell content. The other half was fixed for 24-48 hours in 4% paraformaldehyde; samples were then transferred to 20% Hexabrix for 24 hours before imaging by micro-computed tomography (μCT) to assess PG distribution. Following μCT, samples were again placed in 4% paraformaldehyde for 24-48 hours and then prepared for qPLM to assess collagen orientation (α), parallelism index (PI), and area fraction of non-birefringent tissue (AFNBR). Variations were assessed by ANOVA with post hoc tests for significant ANOVA (pResults: Four days of spherical bending significantly changed (pDiscussion: Spherical bending reshapes AC into a cup shape. Trends of decreasing α standard deviation (αSD) with depth in concave samples and increasing αSD with depth in convex samples indicate that COL matrix disorganization is associated with regions of compressive strain. Consequently, further evaluation on the disorganization of the collagen network should be studied to elucidate mechanisms of cartilage reshaping.

Every year there are nearly two million new cases of invasive breast cancer worldwide and over 500,000 deaths, the majority from metastatic sites. While cellular changes during tumorigenesis and progression have been studied, our understanding of extracellular matrix remodeling, at the fiber level, by individual and collective cellular cohorts remains limited. Furthermore, recent studies suggest that there is a correlation between the organization of collagen I fibers perpendicular to the tumor and patient survival. However, the underlying mechanism of this alignment remains unknown. The central hypothesis proposed in this dissertation is that breast cancer tumors reorganize collagen I fibers perpendicular to the tumor surface via integrin β1 and matrix metalloproteinases (MMPs). To investigate this hypothesis, we developed a novel in vitro assay that replicates collagen I fiber alignment previously reported in vivo and a new quantitative collagen I fiber orientation algorithm. Our studies using multicellular aggregates, derived from the triple negative breast cancer cell line MDA-MB-231, embedded into collagen I matrices and confocal reflectance microscopy provide novel insights into how the local microenvironment is affected and into local orientation of the collagen I fibers near the spheroid-collagen I interface. These results agree well with our computational studies. Furthermore, the viability of the algorithm is demonstrated using both in silico and in vitro derived images, and shows that this algorithm is more accurate than similar algorithms previously published. Using the developed in vitro assay and computational algorithm it is also demonstrated that knocking down integrin β1 reduces the amount of collagen I aligned perpendicularly to the tumor surface, while inhibiting MMP activity using the broad spectrum MMP inhibitor GM6001 increases the amount of collagen I aligned perpendicularly to the tumor surface at early time points. The work presented here has implications in three-dimensional multicellular assays, accurate fiber orientation analysis, and understanding the role of integrins in matrix reorganization and cancer cell metastasis. / 2019-08-09T00:00:00Z

No description available.

Recentemente, descobrimos que coelhos, Nova Zelândia, imunizados com colágeno tipo V humano mais adjuvante de Freund apresentavam fibrose e vasculite de órgãos normalmente afetados na esclerose sistêmica. Deste modo, nós estudamos o processo de fibrilogênese para identificar possíveis fatores envolvidos na alteração do remodelamento observado neste modelo de esclerodermia. Adicionalmente, fizemos uma comparação preliminar com pele humana obtida de pacientes com esclerodermia (n=3). Coelhos fêmeas, Nova Zelândia (n=14), foram imunizados subcutaneamente com duas doses de 1mg de colágeno V mais adjuvante completo de Freund, com intervalo de 30 dias, seguido de duas imunizações em adjuvante incompleto de Freund, via intramuscular, com intervalo de 15 dias. Os animais do grupo controle (n- 14) foram inoculados somente com adjuvante completo e incompleto de Freund, nas mesmas condições dos imunizados. Foram realizadas análises histológicas das peles dos animais e pacientes através da coloração com tricrômico de Masson e imunofluorescêcia, a fim de detectar fibras de colágeno e interação dos colágenos I, III e V. A análise da pele dos animais demonstrou depósito precoce de fibras de colágeno na derme após 7 dias da sensibilização, com aumento destes depósitos após 75 e 120 dias respectivamente. Depósito de colágeno na pele e atrofia de anexos foram mais intensos nos animais sacrificados em 120 dias e se correlacionaram com a quantidade aumentada de colágeno. Surpreendentemente, o colágeno V foi expresso em animais e pacientes, formando fibras densas e atípicas na derme. Sugerimos que esta expressão anômala de colágeno V, morfologicamente diferente, possa justificar o remodelamento observado na placa esclerodérmica / Recently, we discovered that New Zealand rabbits immunized with human type V collagen plus Freund`s adjuvant presented fibrosis and vasculitis of organs usually affected in systemic sclerosis. In this way, we studied the fibrillogenesis process regarding to identify any possible factor involved in altered remodeling observed in this scleroderma-like model. Additionally, we done a very preliminary comparison with human skins obtained from scleroderma patients (N=3). Female New Zealand rabbits (N=14) were immunized subcutaneously with two doses of 1mg collagen V plus complete Freunds adjuvant at a 30 days interval, followed by two additional intramuscular booster immunizations in incomplete Freunds adjuvant at a 15-day interval. Animals from control group (N=14), were only inoculated with complete and incomplete Freunds adjuvant given at same conditions of collagen type V group. Histological analysis of skins from animals and patients were done by Massons trichrome staining, and immunofluorescence method used to detect collagen fibers and interactions of types I, III and V collagen in the remodeling process. The analysis of animal skins showed precocious collagen fibril deposits in the dermis after 7 days of immunization and increase of this process in 75 and 120 days. Skin collagen deposit and atrophy of annexes were progressively more intense in late sacrificed animals and correlated with increased amount of collagen deposition. Surprisingly, type V collagen was over expressed both in animals and patients, forming dense and atypical collagen fibers in the dermis. We suggest that this anomalous expression of morphologically different type V collagen could justify the remodeling observed in scleroderma plaque

Recentemente, descobrimos que coelhos, Nova Zelândia, imunizados com colágeno tipo V humano mais adjuvante de Freund apresentavam fibrose e vasculite de órgãos normalmente afetados na esclerose sistêmica. Deste modo, nós estudamos o processo de fibrilogênese para identificar possíveis fatores envolvidos na alteração do remodelamento observado neste modelo de esclerodermia. Adicionalmente, fizemos uma comparação preliminar com pele humana obtida de pacientes com esclerodermia (n=3). Coelhos fêmeas, Nova Zelândia (n=14), foram imunizados subcutaneamente com duas doses de 1mg de colágeno V mais adjuvante completo de Freund, com intervalo de 30 dias, seguido de duas imunizações em adjuvante incompleto de Freund, via intramuscular, com intervalo de 15 dias. Os animais do grupo controle (n- 14) foram inoculados somente com adjuvante completo e incompleto de Freund, nas mesmas condições dos imunizados. Foram realizadas análises histológicas das peles dos animais e pacientes através da coloração com tricrômico de Masson e imunofluorescêcia, a fim de detectar fibras de colágeno e interação dos colágenos I, III e V. A análise da pele dos animais demonstrou depósito precoce de fibras de colágeno na derme após 7 dias da sensibilização, com aumento destes depósitos após 75 e 120 dias respectivamente. Depósito de colágeno na pele e atrofia de anexos foram mais intensos nos animais sacrificados em 120 dias e se correlacionaram com a quantidade aumentada de colágeno. Surpreendentemente, o colágeno V foi expresso em animais e pacientes, formando fibras densas e atípicas na derme. Sugerimos que esta expressão anômala de colágeno V, morfologicamente diferente, possa justificar o remodelamento observado na placa esclerodérmica / Recently, we discovered that New Zealand rabbits immunized with human type V collagen plus Freund`s adjuvant presented fibrosis and vasculitis of organs usually affected in systemic sclerosis. In this way, we studied the fibrillogenesis process regarding to identify any possible factor involved in altered remodeling observed in this scleroderma-like model. Additionally, we done a very preliminary comparison with human skins obtained from scleroderma patients (N=3). Female New Zealand rabbits (N=14) were immunized subcutaneously with two doses of 1mg collagen V plus complete Freunds adjuvant at a 30 days interval, followed by two additional intramuscular booster immunizations in incomplete Freunds adjuvant at a 15-day interval. Animals from control group (N=14), were only inoculated with complete and incomplete Freunds adjuvant given at same conditions of collagen type V group. Histological analysis of skins from animals and patients were done by Massons trichrome staining, and immunofluorescence method used to detect collagen fibers and interactions of types I, III and V collagen in the remodeling process. The analysis of animal skins showed precocious collagen fibril deposits in the dermis after 7 days of immunization and increase of this process in 75 and 120 days. Skin collagen deposit and atrophy of annexes were progressively more intense in late sacrificed animals and correlated with increased amount of collagen deposition. Surprisingly, type V collagen was over expressed both in animals and patients, forming dense and atypical collagen fibers in the dermis. We suggest that this anomalous expression of morphologically different type V collagen could justify the remodeling observed in scleroderma plaque

Le carcinome hépatocellulaire (CHC) est une des principales causes de mortalité par cancer dans le monde. Dans environ 50% des tumeurs, on observe les signes d’une activation de la voie Wnt/β-caténine, causée par une mutation de l’exon 3 du gène CTNNB1 ou par stimulation du récepteur FRZD. Des études transcriptomiques du CHCs ont montré que ces deux modes d’activation étaient associés à des sous-types de tumeurs différents. Nous avons cherché à mieux comprendre les caractéristiques cliniques et le phénotype moléculaire de ces deux sous-types de CHCs. Dans un premier temps, nous avons fait le lien entre l'activation Wnt extracellulaire, un phénotype de cellules cancéreuses souches ou progénitrices et la présence de foyers de fibrose discrète intra-tumorale, observable par examen histopathologique, que nous avons appelés "nids fibreux". Nous avons également mis en évidence HAPLN1, une protéine de la matrice extracellulaire dont l’expression est stimulée par Wnt3a dans un modèle de cellules hépatiques progénitrices HepaRG, comme un nouveau marqueur d’agressivité du CHC. Ces résultats montrent une association entre l’activation Wnt extracellulaire et une agressivité tumorale passant par un remodelage matriciel. Dans un second temps, une Méta-analyse de données publiques de transcriptomique a permis de mettre évidence 4 sous-types de CHCs. La mutation CTNNB1, prédite par l’expression de 5 marqueurs par une méthode développée durant la thèse, était associée à un de ces sous-types et à un bon pronostic clinique. Nous avons également isolé un nouveau sous-type de CHC de bon pronostic exprimant un phénotype de tumeur différenciée et des signatures de métabolisme hépatique périportales. Ce sous-type a probablement été un facteur confondant dans les études précédentes mesurant l’association de la mutation CTNNB1 avec un bon pronostic. Enfin, nous avons mis en évidence une forte association négative entre la mutation CTNNB1 et l’inflammation ainsi que la fibrose tumorale dans trois cohortes indépendantes. Cet effet pourrait être provoqué par une inhibition de NF-κB par la β-caténine mutée, comme suggérée par des résultats préliminaires issue d’un modèle in vitro d’HepaRG mutés T41 stimulés par LPS. Nos résultats suggèrent donc que les deux modes d’activation de la voie Wnt/β-caténine sont associés à des mécanismes moléculaires, des profils d’expression, des phénotypes et des pronostics cliniques très différents. / Hepatocellular carcinoma (HCC) is the third cause of cancer-related death worldwide. Half of them show activation of Wnt/β-catenin pathway, caused by activating CTNNB1 exon 3 mutation of by stimulation of FRZD receptor. Transcriptomic based HCC classifications showed that this two types of activation were associated with distinct tumor subtypes. We tried to better understand the molecular phenotypes and the clinical features associated with these subtypes. In a first part, we linked extracellular Wnt activation with a stem/progenitor phenotype and with fibrous hotspot in HCC. Fibrous hotspot, which were called “fibrous nest”, can be detected by routine anatomic pathology analyses. We also showed that HAPLN1, an extracellular matrix protein induced by Wnt3a in progenitor HepaRG cells, was a new marker of stemness and bad outcome in HCC. Those results shows the associations between extracellular Wnt activation, extracellular matrix remodeling and tumor aggressiveness. In a second part, a transcriptome meta-analysis of 1133 HCCs highlighted 4 robust subclasses. CTNNB1 mutation, predicted by a 5-genes score based method, was associated with one of these subclasses and with good clinical features. We also highlighted a new subclass of CTNNB1 wild type HCCs associated with tumor differentiation, signatures of periportal metabolism and good outcome. This subclass was probably a confounding factor in survival studies comparing HCCs carrying mutant versus those carrying wild-type CTNNB1. Finally, we highlighted strong negative associations between CTNNB1 mutation and inflammation as well as tumor fibrosis in three independent cohorts. Preliminary results of in vitro HepaRG cells mutated for CTNNB1 in T41 and stimulated by LPS suggest an inhibitory effect of β-caténine on NF-κB. In conclusion, our results show that the two types of Wnt activation in HCC are associated with very distinct molecular phenotypes and clinical features.

The tumor microenvironment is a key modulator in cancer progression and has become a novel target in cancer therapy. An increase in hyaluronan (HA) accumulation and metabolism can be found in advancing tumor progression and are often associated with aggressive malignancy, drug resistance and poor prognosis. Wound-healing related myofibroblasts or activated cancer-associated fibroblasts (CAF) are assumed to be the major sources of HA. Both cell types are capable to synthesize new matrix components as well as reorganize the extracellular matrix. However, to which extent myofibroblasts and CAF perform these actions are still unclear. In this work, we investigated the matrix remodeling and HA production potential in normal human dermal fibroblasts (NHFB) and CAF in the absence and presence of transforming growth factor beta -1 (TGF-β1), with TGF-β1 being a major factor of regulating fibroblast differentiation. Three-dimensional (3D) collagen matrix was utilized to mimic the extracellular matrix of the tumor microenvironment. We found that CAF appeared to response insensitively towards TGF-β1 in terms of cell proliferation and matrix remodeling when compared to NHFB. In regards of HA production, we found that both cell types were capable to produce matrix bound HA, rather than a soluble counterpart, in response to TGF-β1. However, activated CAF demonstrated higher HA production when compared to myofibroblasts. The average molecular weight of produced HA was found in the range of 480 kDa for both cells. By analyzing gene expression of HA metabolizing enzymes, namely hyaluronan synthase (HAS1-3) and hyaluronidase (HYAL1-3) isoforms, we found expression of specific isoforms in dependence of TGF-β1 present in both cells. In addition, HAS2 and HYAL1 are highly expressed in CAF, which might contribute to a higher production and degradation of HA in CAF matrix. Overall, our results suggested a distinct behavior of NHFB and CAF in 3D collagen matrices in the presence of TGF-β1 in terms of matrix remodeling and HA production pointing to a specific impact on tumor modulation.