Biopathologic Characterization and Grade Assessment of Breast Cancer With 3-D Multiparametric Ultrasound Combining Shear Wave Elastography and Backscatter Tensor Imaging

OBJECTIVE

Despite recent improvements in medical imaging, the final diagnosis and biopathologic characterization of breast cancers currently still requires biopsies. Ultrasound is commonly used for clinical examination of breast masses. B-Mode and shear wave elastography (SWE) are already widely used to detect suspicious masses and differentiate benign lesions from cancers. But additional ultrasound modalities such as backscatter tensor imaging (BTI) could provide relevant biomarkers related to tissue organization. Here we describe a 3-D multiparametric ultrasound approach applied to breast carcinomas in the aims of (i) validating the ability of BTI to reveal the underlying organization of collagen fibers and (ii) assessing the complementarity of SWE and BTI to reveal biopathologic features of diagnostic interest.

METHODS

Three-dimensional SWE and BTI were performed ex vivo on 64 human breast carcinoma samples using a linear ultrasound probe moved by a set of motors. Here we describe a 3-D multiparametric representation of the breast masses and quantitative measurements combining B-mode, SWE and BTI.

RESULTS

Our results reveal for the first time that BTI can capture the orientation of the collagen fibers around tumors. BTI was found to be a relevant marker for assessing cancer stages, revealing a more tangent tissue orientation for in situ carcinomas than for invasive cancers. In invasive cases, the combination of BTI and SWE parameters allowed for classification of invasive tumors with respect to their grade with an accuracy of 95.7%.

CONCLUSION

Our results highlight the potential of 3-D multiparametric ultrasound imaging for biopathologic characterization of breast tumors.

Uniaxial mechanical stretch properties correlated with three-dimensional microstructure of human dermal skin

The intact and healthy skin forms a barrier to the outside world and protects the body from mechanical impact. The skin is a complex structure with unique mechano-elastic properties. To better direct the design of biomimetic materials and induce skin regeneration in wounds with optimal outcome, more insight is required in how the mechano-elastic properties emerge from the skin's main constituents, collagen and elastin fibers. Here, we employed two-photon excited autofluorescence and second harmonic generation microscopy to characterize collagen and elastin fibers in 3D in 24 human dermis skin samples. Through uniaxial stretching experiments, we derive uni-directional mechanical properties from resultant stress-strain curves, including the initial Young's modulus, elastic Young's modulus, maximal stress, and maximal and mid-strain values. The stress-strain curves show a large variation, with an average Young's modules in the toe and linear regions of 0.1 MPa and 21 MPa. We performed a comprehensive analysis of the correlation between the key mechanical properties with age and with microstructural parameters, e.g., fiber density, thickness, and orientation. Age was found to correlate negatively with Young's modulus and collagen density. Moreover, real-time monitoring during uniaxial stretching allowed us to observe changes in collagen and elastin alignment. Elastin fibers aligned significantly in both the heel and linear regions, and the collagen bundles engaged and oriented mainly in the linear region. This research advances our understanding of skin biomechanics and yields input for future first principles full modeling of skin tissue.

Histoarchitecture of stromal collagen fibers in gastrointestinal hollow organs of mice after a 30-day space flight

The digestive organs are highly sensitive to the influence of orbital flight factors and can limit the professional activities of crew members aboard the International Space Station. Connective tissue, as a system-forming matrix of the integrative-buffer metabolic environment, is of particular relevance in space biomedicine, ensuring the functioning of internal organs under an altered gravitational stimulus. However, the adaptive mechanisms of the fibrous extracellular matrix of the gastric and intestinal connective tissue have not been fully investigated under prolonged microgravity weightlessness. Using histochemical techniques, we experimentally studied the state of collagen fibers in the specific tissue microenvironment of the gastric and intestinal membranes in C57BL/6 N mice after a 30-day space flight, subsequent 7-day ground readaptation, and in animals of the relevant control groups. The 30-day stay of laboratory animals aboard the Bion-M 1 biosatellite resulted in a reduction in the fibrous extracellular matrix of connective tissue in the studied digestive organs, excepting the gastric lamina propria. Increased fibrillogenesis was revealed in the gastrointestinal mucous membranes of animals 7 days after biosatellite landing compared with the parameters of animals in the space flight group. During the experiment with ground simulated orbital flight conditions, changes in collagen fibers were not significant compared to the vivarium control group. Thus, the results obtained evidence gravisensitivity of the fibrous extracellular matrix of the intraorgan connective tissue. This fact also highlights the necessity to further improve gastrointestinal tract-related preventive measures for astronauts during orbital flight.

Effects of different subcutaneous sites on heterotopic autotransplantation of canine ovarian tissue

Ovarian tissue transplantation makes it possible to restore fertility; however, the success of this technique depends on the transplant region used. Therefore, this study aimed to evaluate the effect of two subcutaneous regions on canine ovarian transplantation, pinna (Pi) and neck (Ne), for 7 and 15 days. Ovaries collected by ovariosalpingohysterectomy were fragmented using a punch device. Fresh fragments were fixed, and the others were immediately grafted onto the animal itself in the Pi and Ne regions for 7 and 15 days. Recovered fragments were evaluated for histology (morphology, development and stromal density), picrosirius (collagen fibers), and immunohistochemistry (fibrosis and cell proliferation). The results showed that follicular normality rates were lower in Pi-7 (78%) vs. control (90%) and Pi-15 (86%), similar in Ne-7 (92%) and superior in Ne-15 (97%) compared to the control, with the effect of the region Ne (94%) superior (P < 0.05) to Pi (82%). Stromal density reduced in both regions vs. control but was similar within 15 days. Fragments from both regions showed higher fibronectin labeling and deposition of type I and lower type III collagen fibers (P < 0.05) vs. control. Proliferation rates in Ne-7 were higher (P < 0.05) than in control, and Pi-15 was higher (P < 0.05) than Ne-15. In conclusion, the pinna may be a region with greater potential than the neck after a 15-day autotransplantation of canine ovarian tissue.

The value of a dual-energy CT Iodine map radiomics model for the prediction of collagen fiber content in the ccRCC tumor microenvironment

BACKGROUND AND PURPOSE

Renal cell carcinoma (RCC) is a heterogeneous group of cancers. The collagen fiber content in the tumor microenvironment of renal cancer has an important role in tumor progression and prognosis. A radiomics model was developed from dual-energy CT iodine maps to assess collagen fiber content in the tumor microenvironment of ccRCC.

METHODS

A total of 87 patients with ccRCC admitted to our hospital were included in this retrospective study. Among them, 59 cases contained large amounts of collagen fibers and 28 cases contained a small amount of collagen fibers. We established a radiomics model using preoperative dual-energy CT scan Iodine map (IV) imaging to distinguish patients with multiple collagen fibers from those with few collagen fibers in the tumor microenvironment of ccRCC. We extracted features from dual-energy CT Iodine map images to evaluate the effects of six classifiers, namely k-nearest neighbor (KNN), support vector machine (SVM), extreme gradient boosting (XGBoost), random forest (RF), logistic regression (LR), and decision tree (DT). The effects of the models built based on the dynamic and venous phases are also compared. Model performance was evaluated using quintuple cross-validation and area under the receiver operating characteristic curve (AUC). In addition, a clinical model was developed to assess the clinical factors affecting collagen fiber content.

RESULTS

Compared to KNN, SVM, and LR classifiers, RF, DT, and XGBoost classifiers trained with higher AUC values, with training sets of 0.997, 1.0, and 1.0, respectively. In the validation set, the highest AUC was found in the SVM classifier with a size of 0.722. In the comparative test of the active and intravenous phase models, the SVM classifier had the best effect with its validation set AUC of 0.698 and 0.741. In addition, there was a statistically significant effect of patient age and maximum tumor diameter on the collagen fiber content in the tumor microenvironment of kidney cancer.

CONCLUSION

Radionics features based on preoperative dual-energy CT IV can be used to predict the amount of collagen fibers in the tumor microenvironment of renal cancer. This study better informs clinical prognosis and patient management. Iodograms may add additional value to dual-energy CTs.

A multiscale investigation into the role of collagen-hyaluronan interface shear on the mechanical behaviour of collagen fibers in annulus fibrosus - Molecular dynamics-cohesive finite element-based study

Multi-directional deformation exhibited by annulus fibrosus (AF) is contributed by chemo-mechanical interactions among its biomolecular constituents' collagen type I (COL-I), collagen type II (COL-II), proteoglycans (aggrecan and hyaluronan) and water. However, the nature and role of such interactions on AF mechanics are unclear. This work employs a molecular dynamics-cohesive finite element-based multiscale approach to investigate role of COL-I-COL-II interchanging distribution and water concentration (WC) variations from outer annulus (OA) to inner annulus (IA) on collagen-hyaluronan (COL-HYL) interface shear, and the mechanisms by which interface shear impacts fibril sliding during collagen fiber deformation. At first, COL-HYL interface atomistic models are constructed by interchanging COL-I with COL-II and increasing COL-II and WC from 0 to 75%, and 65%-75% respectively. Thereafter, a multiscale approach is employed to develop representative volume elements (RVEs) of collagen fibers by incorporating COL-HYL shear as traction-separation behaviour at fibril-hyaluronan contact. Results show that increasing COL-II and WC increases interface stiffness from 0.6 GPa/nm to 1.2 GPa/nm and reduces interface strength from 155 MPa to 58 MPa from OA to IA, contributed by local hydration alterations. A stiffer and weaker interface enhances fibril sliding with increased straining at the contact - thereby contributing to reduction in modulus from 298 MPa to 198 MPa from OA to IA. Such reduction further contributes to softer mechanical response towards IA, as reported by earlier studies. Presented multiscale analysis provides deeper understanding of hierarchical structure-mechanics relationships in AF and can further aid in developing better substitutes for AF repair.

Postnatal morpho-functional development of a dog's meniscus

This study evaluates the morpho-functional modifications that characterize meniscal development from neonatal to adult dogs. Even if menisci are recognized as essential structures for the knee joint, poor information is available about their morphogenesis, in particular in dog models. Menisci from a group of Dobermann Pinchers aged 0, 10, 30 days, and 4 years (T0, T10, T30, adult, respectively) were analyzed by SEM, histochemistry (Safranin O and Picro Sirius Red Staining analyzed under a polarized light microscope), immunofluorescences (collagen type I and II), biomechanical (compression) and biochemical analyses (glycosaminoglycans, GAGs, and DNA content). SEM analyses revealed that the T0 meniscus is a bulgy structure that during growth tends to flatten, firstly in the inner zone (T10) and then even in the outer zone (T30), until the achievement of the completely smooth adult final shape. These results were further supported by the histochemistry analyses in which the deposition of GAGs started from T30, and the presence of type I birefringent collagen fibers was observed from T0 to T30, while poorly refringent type III collagen fibers were observed in the adult dogs. Double immunofluorescence analyses also evidenced that the neonatal meniscus contains mainly type I collagen fibers, as well as the T10 meniscus, and demonstrated a more evident regionalization and crimping in the T30 and adult meniscus. Young's elastic modulus of the meniscus in T0 and T10 animals was lower than the T30 animals, and this last group was also lower than adult ones (T0-T10 vs T30 vs adult). Biochemical analysis confirmed that cellularity decreases over time from neonatal to adult (p < 0.01). The same decreasing trend was observed in GAGs deposition. These results may suggest that the postnatal development of canine meniscus may be related to the progressive functional locomotory development: after birth, the meniscus acquires its functionality over time, through movement, load, and growth itself.

Multimodal and multiscale characterization reveals how tendon structure and mechanical response are altered by reduced loading

Tendons are collagen-based connective tissues where the composition, structure and mechanics respond and adapt to the local mechanical environment. Adaptation to prolonged inactivity can result in stiffer tendons that are more prone to injury. However, the complex relation between reduced loading, structure, and mechanical performance is still not fully understood. This study combines mechanical testing with high-resolution synchrotron X-ray imaging, scattering techniques and histology to elucidate how reduced loading affects the structural properties and mechanical response of rat Achilles tendons on multiple length scales. The results show that reduced in vivo loading leads to more crimped and less organized fibers and this structural inhomogeneity could be the reason for the altered mechanical response. Unloading also seems to change the fibril response, possibly by altering the strain partitioning between hierarchical levels, and to reduce cell density. This study elucidates the relation between in vivo loading, the Achilles tendon nano-, meso‑structure and mechanical response. The results provide fundamental insights into the mechanoregulatory mechanisms guiding the intricate biomechanics, tissue structural organization, and performance of complex collagen-based tissues. STATEMENT OF SIGNIFICANCE: Achilles tendon properties allow a dynamic interaction between muscles and tendon and influence force transmission during locomotion. Lack of physiological loading can have dramatic effects on tendon structure and mechanical properties. We have combined the use of cutting-edge high-resolution synchrotron techniques with mechanical testing to show how reduced loading affects the tendon on multiple hierarchical levels (from nanoscale up to whole organ) clarifying the relation between structural changes and mechanical performance. Our findings set the first step to address a significant healthcare challenge, such as the design of tailored rehabilitations that take into consideration structural changes after tendon immobilization.

Influence of surface nanotopography and wettability on early phases of peri-implant soft tissue healing: an in-vivo study in dogs

BACKGROUND

It is well established that nanotopography and wettability of implant surfaces contribute to osseointegration and long-term implant success. However, the effects of a hydrogenated surface with nanotubular and superhydrophilic properties on peri-implant soft tissue remain unclear. This study was designed to study the impact of a modified abutment surface on early soft tissue integration compared with a machined surface.

METHODS

Thirty-six implants were placed at the bone level in the bilateral mandible of six beagles, followed by healing abutments belonging to the standard machined Ti-6Al-4V alloy abutments (TC4-M), anodized abutments with nanotubes (TC4-Nano), and hydrogenated abutments (TC4-H/Nano) groups, which were randomly screwed to the implants. After two and four weeks of wound healing, the animals were euthanized for histological evaluation.

RESULTS

A superhydrophilic nanotubular surface developed on the hydrogenated abutment. Histological and histometric analyses revealed similar peri-implant soft tissue healing and dimensions for the three types of abutments at two and four weeks. Connective tissue (CT) length was longer around TC4-H/Nano abutments compared with standard abutments; however, the differences were not statistically significant. Moreover, collagen fibers in the TC4-H/Nano group extended and were attached perpendicularly to the superhydrophilic surface.

CONCLUSIONS

Our results revealed that the soft tissue interface adjacent to the hydrogenated abutment is comparable to that of the machined abutment. A tendency of increased CT length and perpendicular collagen fibers was observed around the modified abutment. This study suggests that nanotubular/superhydrophilic surfaces could be a promising modification to enhance soft tissue sealing. However, comprehensive studies should be conducted to evaluate the peri-implant soft tissue around the modified abutment immunohistochemically, histopathologically, and clinically.

Pathological features of vascular wall in Dieulafoy's disease

AIMS

Although there are many clinical reports on Dieulafoy's disease, there are few studies on the pathological structure of vascular wall in Dieulafoy's disease.

METHODS

In this study, the main structural changes of the intima and media of the vascular wall were observed by special staining and immunohistochemical methods in the subjects of Dieulafoy's disease of stomach and intestine.

RESULTS

There were many vessels of different sizes in the submucosa, with uneven wall thickness of the vessels. Compared with the normal control group, the content of blue collagen fibers between the vascular smooth muscle cells in the lesion group was increased, the elastic fibers were thickened, and the internal elastic plate was arranged stiff or even interrupted.

CONCLUSIONS

The increase of collagen and elastic fibers between the smooth muscle cells of the medium membrane and the destruction of the structure of the inner elastic plate may be the structural basis of vascular lesions leading to Dieulafoy's disease.

Liver fibrotic development is reduced through inflammation prevention by an adenosine derivative compound

BACKGROUND

Liver fibrosis is a global health problem, and studying its development provides important information to address its treatment. Here, we characterized the effects of an adenosine compound (IFC-305) on preventing fibrosis and liver inflammation.

METHODS

We studied the impact of IFC-305 on a carbon tetrachloride-induced liver fibrosis model in Wistar male rats at 4, 6, and 8 weeks. The effects were characterized by liver tissue histology, macrophages identification by flow cytometry with CD163+/CD11b/c+ antibodies, hepatic and plasmatic cytokine levels employing MILLIPLEX MAP and ELISA, Col1a1 and Il6 gene expression by RTqPCR, lipoperoxidation by TBARS reaction, and reactive oxygen species using 2'-7'dichlorofluorescin diacetate.

RESULTS

CCl4-induced liver fibrosis and inflammation were significantly reduced in rats treated with IFC-305 at 6 and 8 weeks. In addition, we observed diminished expression of Col1a1; a decrease in the inflammatory cytokines IL-1β, IL-6, MCP-1, TNF-α, and IL-4 a; reduction in inflammatory macrophages; inhibition of lipoperoxidation; and ROS production in Kupffer cells.

CONCLUSION

This study showed that IFC-305 can inhibit liver fibrosis establishment by regulating the immune response during CCl4-induced damage. The immunomodulatory action of IFC-305 supports its use as a potential therapeutic strategy for preventing liver fibrosis.

Cardioprotective Effects of the 4-Week Aerobic Running Exercises Before Treatment with Doxorubicin in Rats

Doxorubicin is associated with cardiotoxicity, and physical exercise seeks to minimize the toxic effects of doxorubicin through physiological cardiac remodeling, as well as the reduction of oxidative stress, evidenced by previous studies. This study aimed to analyze whether running training before treatment with doxorubicin influences tolerance to physical exertion and cardiotoxicity. Thirty-nine male Wistar rats, aged 90 days and weighing between 250 and 300 g, were divided into 4 groups: Control (C), Doxorubicin (D), Trained (T), and Trained + Doxorubicin (TD). Animals in groups T and DT were submitted to treadmill running for 3 weeks, 5 times a week at 18 m/min for 20-30 min before treatment with doxorubicin. Animals in groups D and DT received intraperitoneal injections of doxorubicin hydrochloride three times a week for two weeks, reaching a total cumulative dose of 7.50 mg/kg. Our results show an increase in total collagen fibers in the D group (p = 0.01), but no increase in the TD group, in addition to the attenuation of the number of cardiac mast cells in the animals in the TD group (p = 0.05). The animals in the TD group showed maintenance of tolerance to exertion compared to group D. Therefore, running training attenuated the cardiac damage caused by the treatment with doxorubicin, in addition to maintaining the tolerance to exertion in the rats.

A biomass fiber adsorbent grafted with phosphate/amidoxime for efficient extraction of uranium from seawater by synergistic effect

There are approximately 4 billion tons of uranium in the ocean, which is unmatched by the surface. Nevertheless, it's very challenging to extract uranium from the ocean due to the exceedingly low concentration of uranium in the ocean (about 3.3 μg L^-1) as well as high salinity level. Current methods are often limited by selectivity, sustainability, economics, etc. Herein, phosphoric acid group and amidoxime group were grafted to skin collagen fibers through " initiated access" to design a new uranium extraction material, abbreviated as CGPA. Through laboratory simulation experiments, it is concluded that the maximum adsorption capacity of CGPA for uranium reaches 263.86 mg g^-1. It has high adsorption, selectivity, and reusability for uranium. In the actual seawater extraction experiment, CGPA obtained 29.64 μg of uranium after extracting 10.0 L of seawater, and the extraction rate was 90.1%. The adsorbent has excellent effects in kinetics, selectivity, extraction capacity, renewability, etc. In the extraction of uranium from seawater, and is an economically feasible and industrially expandable adsorbent.

A specialized protocol for mechanical testing of isolated networks of type II collagen

The mechanical responses of most soft biological tissues rely heavily on networks of collagen fibers, thus quantifying the mechanics of both individual collagen fibers and networks of these fibers advances understanding of biological tissues in health and disease. The mechanics of type I collagen are well-studied and quantified. Yet no data exist on the tensile mechanical responses of individual type II collagen fibers nor of isolated networks comprised of type II collagen. We aimed to establish methods to facilitate studies of networked and individual type II collagen fibers within the native networked structure, specifically to establish best practices for isolating and mechanically testing type II collagen networks in tension. We systematically investigated mechanical tests of networks of type II collagen undergoing uniaxial extension, and quantified ranges for each of the important variables to help ensure that the experiment itself does not affect the measured mechanical parameters. Specifically we determined both the specimen (establishing networks of isolated collagen, the footprint and thickness of the specimen) and the mechanical test (both the device and the strain rate) to establish a repeatable and practical protocol. Mechanical testing of isolated networks of type II collagen fibers leveraging this protocol will lead to better understanding of the mechanics both of these networks and of the individual fibers. Such understanding may aid in developing and testing therapeutics, understanding inter-constituent interactions (and their roles in bulk-tissue biomechanics), investigating mechanical/biochemical modifications to networked type II collagen, and proposing, calibrating, and validating constitutive models for finite element analyses.

Differentiation of pancreatic ductal adenocarcinoma and chronic pancreatitis using graph neural networks on histopathology and collagen fiber features

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human cancers. However, the symptoms and radiographic appearance of chronic pancreatitis (CP) mimics that of PDAC, and sometimes the 2 entities can also be difficult to differentiate microscopically. The need for accurate differentiation of PDAC and CP has become a major topic in pancreatic pathology. These 2 diseases can present similar histomorphological features, such as excessive deposition of fibrotic stroma in the tissue microenvironment and inflammatory cell infiltration. In this paper, we present a quantitative analysis pipeline empowered by graph neural networks (GNN) capable of automatic detection and differentiation of PDAC and CP in human histological specimens. Modeling histological images as graphs and deploying graph convolutions can enable the capture of histomorphological features at different scales, ranging from nuclear size to the organization of ducts. The analysis pipeline combines image features computed from co-registered hematoxylin and eosin (H&E) images and Second-Harmonic Generation (SHG) microscopy images, with the SHG images enabling the extraction of collagen fiber morphological features. Evaluating the analysis pipeline on a human tissue micro-array dataset consisting of 786 cores and a tissue region dataset consisting of 268 images, it attained 86.4% accuracy with an average area under the curve (AUC) of 0.954 and 88.9% accuracy with an average AUC of 0.957, respectively. Moreover, incorporating topological features of collagen fibers computed from SHG images into the model further increases the classification accuracy on the tissue region dataset to 91.3% with an average AUC of 0.962, suggesting that collagen characteristics are diagnostic features in PDAC and CP detection and differentiation.

Hierarchical collagen fibers complexed with tannic acid and Fe3+ as a heterogeneous catalyst for enhancing sulfate radical-based advanced oxidation process

Efficient sulfate radical-based advanced oxidation processes (SR-AOPs) are important for treating organic contaminants of industrial wastewater. To achieve this goal, tannic acid (TA)-modified skin collagen fibers (CFs) were prepared for the enhanced immobilization of Fe³⁺ based on multiple complexation interactions, resulting in a heterogeneous catalyst with more catalytic sites (defined as TA-Fe-CFs) for activating peroxymonosulfate (PMS). During the removal of an organic dye (rhodamine B, RhB) from water, the hierarchical TA-Fe-CFs exhibited excellent adsorption capacity at the early stage before the introduction of PMS, which can be ascribed to the π-π interaction between TA and aromatic RhB. Such improved mass transfer of target contaminants into the catalytic support was proved to be beneficial for improving the utilization efficiency of sulfate radicals in subsequent SR-AOPs. After introducing PMS, the reductive TA moieties of the heterogeneous catalyst were able to accelerate the redox cycle of Fe³⁺/Fe²⁺ in Fenton reactions, facilitating the activation of PMS to generate sulfate radicals for the degradation of organic RhB.

The influence of glutaraldehyde on the microscopic structure of human pericardium

OBJECTIVES

In our study we investigate the collagen structure of human pericardium microscopically in dependence of glutaraldehyde (GA) concentration and fixation time.

METHODS

Pericardial samples were taken from 9 patients aged 40+ years who underwent cardiac surgery, either coronary artery bypass surgery or valve implantation/reconstruction. Specimens were cut in five equal pieces and treated with GA at fixed concentrations (0.3125 %, 0.625 % or 1.25 %) but different exposer times (5 min, 10 min, 20 min, 30 min and 60 min). Elastica van Gieson (EvG) staining was used for microscopic examination of pericardial collagen structure.

RESULTS

The collagen structure studied microscopically depended on both GA incubation time and GA concentration. At low GA concentrations (0.3125 %, 0.625 %) and short incubation times, individual collagen fibers appeared separately. After one hour incubation period, single collagen fibers could not be distinguished at any GA concentration. For fixed incubation times no differences were seen in the collagen structure when 0.3125 % and 0.625 % GA were used. However, at a concentration of 1.25 % GA fusion of individual collagen fibers was already observed at low incubation times.

CONCLUSION

Pericardial collagen structure changes with increasing incubation time and increasing GA concentration by raising fusion of single fibers. For GA concentrations of ≤ 0.625 %, fiber fusion depends plainly on incubation time. That is relevant as this concentration is used in cardiac surgery. At a concentration of 1.25 % GA, single collagen fibers could not be separated, even at short incubation times. Fusion of individual collagen fibers and changes in appearance (less undulating) were assumed to be responsible for stiffening of GA-fixed pericardium.

Microstructure and mechanics of the bovine trachea: Layer specific investigations through SHG imaging and biaxial testing

The trachea is a complex tissue made up of hyaline cartilage, fibrous tissue, and muscle fibers. Currently, the knowledge of microscopic structural organization of these components and their role in determining the tissue's mechanical response is very limited. The purpose of this study is to provide data on the microstructure of the tracheal components and its influence on tissue's mechanical response. Five bovine tracheae were used in this study. Adventitia, cartilage, mucosa/submucosa, and trachealis muscle layers were methodically cut out from the whole tissue. Second-harmonic generation(SHG) via multi-photon microscopy (MPM) enabled imaging of collagen fibers and muscle fibers. Simultaneously, a planar biaxial test rig was used to record the mechanical behavior of each layer. In total 60 samples were tested and analyzed. Fiber architecture in the adventitia and mucosa/submucosa layer showed high degree of anisotropy with the mean fiber angle varying from sample to sample. The trachealis muscle displayed neat layers of fibers organized in the longitudinal direction. The cartilage also displayed a structure of thick mesh-work of collagen type II organized predominantly towards the circumferential direction. Further, mechanical testing demonstrated the anisotropic nature of the tissue components. The cartilage was identified as the stiffest component for strain level < 20% and hence the primary load bearing component. The other three layers displayed a non-linear mechanical response which could be explained by the structure and organization of their fibers. This study is useful in enhancing the utilization of structurally motivated material models for predicting tracheal overall mechanical response.

Imaging of fluorescent polymer dots in relation to channels and immune cells in the lymphatic system

Polymer dots (Pdots) have been applied to imaging lymph nodes (LNs) and lymphatic vessels (LVs) in living mice and rats. However, the mechanism of absorption, distribution, metabolism, and excretion of Pdots in LNs and LVs is still unclear. Therefore, the relationship between Pdots and immune cells, LVs and collagen fibers in lymphatics was studied by multiple in vivo and ex vivo microscopic imaging methods and detection techniques. Flow cytometry showed that Pdots could be phagocytosed by macrophages and monocytes, and had no relationship with B cells, T cells and dendric cells in LNs. Silver staining, immunofluorescence and two-photon microscope showed that Pdots gathered in collagen fibers and LVs of LNs. Furthermore, immunofluorescence imaging results verified that Pdots were distributed in the extracellular space of collecting LVs endothelial cells. In addition, Pdots in the collecting LVs were basically cleared by leaking into the surrounding tissue or draining LNs after 21 days of injection. During the long-time observation, Pdots also helped monitor the contraction frequency and variation range of LV. Our study lays a foundation on the research of Pdots as the carrier to study lymphatic structure and function in the future.

Stiffness of tongue squamous cell carcinoma measured using strain elastography correlates with the amount of collagen fibers in the tumor

OBJECTIVES

To evaluate the stiffness of tongue squamous cell carcinoma (TSCC) using ultrasound strain elastography, a relatively new sonographic imaging technique, and to identify the factors that affect this stiffness.

METHODS

We treated 62 patients diagnosed with muscle invasive TSCC, who were treated at the department of oral surgery of our institution. Each patient's tumor stiffness was semi-quantified according to the ratio of cancer to tongue muscle strain measured using ultrasound strain elastography (the strain ratio). Histopathological diagnosis was made on the same section as the ultrasound strain elastography. We set the following histopathological parameters: cancer cell content in the tumor area (%CCC), collagen fiber content in the tumor area (%CFC), and tumor-infiltrating inflammatory cell content in the stromal compartment (%TIIC). Spearman's rank correlation (rs) was used to assess correlations, and P values < 0.05 were considered significant.

RESULTS

The mean strain ratio was 9.7 ± 9.8. The mean %CCC was 38.4 ± 11.3%, and % CFC was 31.1 ± 7.8%, % TIICs was 19.9 ± 8.9%. Log (strain ratio) by ultrasound strain elastography was positively correlated with %CFC (r_s = 0.379, P = 0.024). %CFC was negatively correlated with %TIICs (r_s =  - 0.318, P = 0.012). No correlations were observed between other clinico-histopathological factors and either strain ratio, or %CFC.

CONCLUSION

The strain ratio of the cancer to the strain of the tongue muscle measured through ultrasound strain elastography positively correlates with the collagen fiber content of the tumor area.

Integration of collagen fibers in connective tissue with dental implant in the transmucosal region

Dental implants have been widely accepted as an ideal therapy to replace the missing teeth for its good performance in aspects of mechanical properties and aesthetic outcomes. Its restorative success is contributed by not only the successful osseointegration of the implant but also the tight soft tissue integration, especially the collagen fibers, in the transmucosal region. Soft tissue attaching to the dental implant/abutment is overall similar, but in some aspects distinct with that seen around natural teeth and soft tissue integration can be enhanced via several surface modification methods. This review is going to focus on the current knowledge of the transmucosal zone around the dental implants (compared with natural teeth), and latest strategies in use to fine-tune the collagen fibers assembly in the connective tissue, in an attempt to enhance soft tissue integration.

Development, maturation and growth of the myodural bridge within the posterior atlanto-axial interspace in the rat

The myodural bridge complex are fibrous bridges that functionally connect the spinal dura mater to the suboccipital musculature. Previously, we described the maturational sequence of the myodural bridge (MDB) within the posterior atlanto-occipital interspace of the rat. The present paper describes the morphology and developmental maturation of the MDB within the posterior atlanto-axial interspace of the rat. In the present study, E18 embryonic rats, newborn rats, and adult rats were selected to evaluate the development and growth of the MDB. Within the posterior atlanto-axial interspace of the rat, the fibers of the MDB and its associated muscles, in the embryonic rat, were observed to be scarce and lightly stained. In contrast, these same structures observed in the postnatal rat were quite apparent and robustly stained. After birth, it was observed that MDB originated from the rectus capitis dorsal major muscle, extended forward and downward, and finally merged with the posterior atlanto-axial membrane. As the rats developed/matured, the observed MDB fibers passing through the posterior atlanto-axial interspace appeared denser and more organized. This study evidenced that the MDB fibers within the posterior atlanto-axial interspace were primarily composed of type I collagen fibers in the postnatal rat. By observing the suboccipital region, we are able to hypothesize that the MDB complex plays a key role in maintaining the subdural space located within the upper cervical segment during growth and development. This study provides a morphological basis for future research on the function of the MDB complex. This article is protected by copyright. All rights reserved.

EDTA-chitosan is a feasible conditioning agent for dentin bonding

OBJECTIVES

The bonding effects of EDTA-chitosan, phosphoric acid, and SE-Bond were compared.

MATERIALS AND METHODS

Material synthesis, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, laser confocal microscopy, microtensile bond strength, stereomicroscope observation section, CCK8 cytotoxicity assay, and microfluidic experiments were applied.

RESULTS

EDTA-chitosan was synthesized, and it was found by transmission electron microscopy that the application of EDTA-chitosan to dentin can extrafibrillarly demineralize collagen fibers. Scanning electron microscopy provided evidence for the retention of smear plugs in dentin conditioned with 1 wt% EDTA-chitosan. Mixed layer and long resin protrusions can be formed after bonding under a laser confocal microscope. The microtensile strength test found that the bonding strength and the durability obtained by applying the chelating agent EDTA-chitosan to dentin were equivalent to SE-Bond and better than the phosphoric acid wet bonding commonly used clinically (P < 0.05). The cytotoxicity of EDTA-chitosan was lower than that of phosphoric acid and SE-Bond in the CCK-8 assay and lower than that of phosphoric acid in the microfluidics experiment.

CONCLUSIONS

Taken together, the EDTA-chitosan extrafibrillar demineralization strategy retains intrafibrillar minerals and provides better bonding strength and durability with lower cytotoxicity.

CLINICAL RELEVANCE

EDTA-chitosan has the potential to be applied to dentin resin for direct bonding restoration and has good clinical application prospects.

Mechanical properties of meniscal circumferential fibers using an inverse finite element analysis approach

The extracellular matrix (ECM) of the meniscus is a gel-like water solution of proteoglycans embedding bundles of collagen fibers mainly oriented circumferentially. Collagen fibers significantly contribute to meniscal mechanics, however little is known about their mechanical properties. The objective of this study was to propose a constitutive model for collagen fibers embedded in the ECM of the meniscus and to characterize the tissue's pertinent mechanical properties. It was hypothesized that a linear fiber reinforced viscoelastic constitutive model is suitable to describe meniscal mechanical behavior in shear. It was further hypothesized that the mechanical properties governing the model depend on the tissue's composition. Frequency sweep tests were conducted on eight porcine meniscal specimens. A first cohort of experimental data resulted from tissue specimens where collagen fibers oriented parallel with respect to the shear plane were used. This was done to eliminate the contribution of collagen fibers from the mechanical response and characterize the mechanical properties of the ECM. A second cohort with fibers orthogonally oriented with respect to the shear plane that were used to determine the elastic properties of the collagen fibers via inverse finite element analysis. Our testing protocol revealed that tissue ECM mechanical behavior could be described by a generalized Maxwell model with 3 relaxation times. The inverse finite element analysis suggested that collagen fibers can be modeled as linear elastic elements having an average elastic modulus of 287.5 ± 62.6 MPa. Magnitudes of the mechanical parameters governing the ECM and fibers were negatively related to tissue water content.

Manipulate the nano-structure of layered double hydroxides via calcination for enhancing immobilization of anionic dyes on collagen fibers

In this work, we present an effective approach for promoting the immobilization of anionic dyes on the collagen fibers of the leather matrix via introducing layered double oxide (LDO), which is obtained by calcining layered double hydroxides (LDH), inspired by incorporating their memory effect and charge effect. The results indicate that the calcination increases specific surface area, oxygen vacancies, and Al³⁺ defects of LDH nanosheets, and the structure of LDH nanosheets can be reconstructed by rehydration. Diffusion behavior of both LDH and LDO nanosheets into the collagen fibers follows the Langmuir model. The LDO nanosheets can penetrate into the collagen fibers more easily and evenly than that of the LDH nanosheets. Moreover, the formation of ionic bonds, hydrogen bonds, and coordination bonds between the nanosheets and the collagen stabilizing the collagen microstructures can endow the collagen fibers with improved thermal stability. Increased porosity of the collagen fibers results in enhanced adsorption and immobilization capacity for anionic dyes on the collagen fibers of the leather matrix in leather post-tanning process. Furthermore, adsorption behavior of anionic dye on the collagen fibers can be well accorded with pseudo-second-order and Langmuir model, exhibiting a monolayer adsorption process. This established cooperative approach will be helpful to extend the application of clay for improving the dyeing performance of leather matrix towards eco-leather manufacture and effectively reduce emission of dyes from the source in leather manufacturing.

Membrane curvature and connective fiber alignment in guinea pig round window membrane

The round window membrane (RWM) covers an opening between the perilymph fluid-filled inner ear space and the air-filled middle ear space. As the only non-osseous barrier between these two spaces, the RWM is an ideal candidate for aspiration of perilymph for diagnostics purposes and delivery of medication for treatment of inner ear disorders. Routine access across the RWM requires the development of new surgical tools whose design can only be optimized with a thorough understanding of the RWM's structure and properties. The RWM possesses a layer of collagen and elastic fibers so characterization of the distribution and orientation of these fibers is essential. Confocal and two-photon microscopy were conducted on intact RWMs in a guinea pig model to characterize the distribution of collagen and elastic fibers. The fibers were imaged via second-harmonic-generation, autofluorescence, and Rhodamine B staining. Quantitative analyses of both fiber orientation and geometrical properties of the RWM uncovered a significant correlation between mean fiber orientations and directions of zero curvature in some portions of the RWM, with an even more significant correlation between the mean fiber orientations and linear distance along the RWM in a direction approximately parallel to the cochlear axis. The measured mean fiber directions and dispersions can be incorporated into a generalized structure tensor for use in the development of continuum anisotropic mechanical constitutive models that in turn will enable optimization of surgical tools to access the cochlea. STATEMENT OF SIGNIFICANCE: The Round Window Membrane (RWM) is the only non-osseous barrier separating the middle and inner ear spaces, and thus is an ideal portal for medical access to the cochlea. An understanding of RWM structure and mechanical response is necessary to optimize the design of surgical tools for this purpose. The RWM geometry and the connective fiber orientation and dispersion are measured via confocal and 2-photon microscopy. A region of the RWM geometry is characterized as a hyperbolic paraboloid and another region as a tapered parabolic cylinder. Predominant fiber directions correlate well with directions of zero curvature in the hyperbolic paraboloid region. Overall fiber directions correlate well with position along a line approximately parallel to the central axis of the cochlea's spiral.

A substrate protection approach to applying the calcium ion for improving the proteolysis resistance of the collagen

Enzymatic dehairing, as a crucial part of cleaner leather processing, has reached processive advancement with potentially replacing the traditional hair removal due to increasing pressure from environmental demand. However, this cleaner technology based on proteases has a problem that the hide grain (collagen-rich structure) is susceptible to be hydrolyzed, decreasing the quality of finished leather. From the perspective of improving the stability of collagen fibers and their resistance to proteolysis, a method for protecting the hide grain during the enzymatic dehairing process was developed. The results showed that calcium ions had a swelling effect on collagen fibers under near-neutral conditions (pH 6.0-10.0), decreasing the thermal stability of collagen and the proteolysis resistance of collagen significantly. The alkaline environment (pH 10.0-12.0) will promote the dissociation of carboxyl groups in hide collagen, promoting the combination of calcium ions and carboxyl groups. This strategy can change the surface charge of collagen fibers and strengthen the connection between collagen fibers, thus improving protease resistance and the thermal stability of collagen. However, collagen fibers could swell violently once the alkalinity of the solution environment was extreme. Despite the above situation, calcium ion was still conducive to maintain the structural stability of collagen fibers. At pH 10.0-12.0, pretreating animal hide with a solution containing calcium ions can improve the protease resistance of hide grain, making the hide grain well-protected. This method provided an effective way to establish a safer enzymatic unhairing technology based on substrate protection. KEY POINTS: • A collagen protection method for hair removal of animal hide was developed. • This method applied calcium ions to collagen at alkaline conditions (pH 10.0-12.0). • Pretreatment results of calcium ions at different pH values on animal hide were compared.

Mammary collagen architecture and its association with mammographic density and lesion severity among women undergoing image-guided breast biopsy

Background

Elevated mammographic breast density is a strong breast cancer risk factor with poorly understood etiology. Increased deposition of collagen, one of the main fibrous proteins present in breast stroma, has been associated with increased mammographic density. Collagen fiber architecture has been linked to poor outcomes in breast cancer. However, relationships of quantitative collagen fiber features assessed in diagnostic biopsies with mammographic density and lesion severity are not well-established.

Methods

Clinically indicated breast biopsies from 65 in situ or invasive breast cancer cases and 73 frequency matched-controls with a benign biopsy result were used to measure collagen fiber features (length, straightness, width, alignment, orientation and density (fibers/µm²)) using second harmonic generation microscopy in up to three regions of interest (ROIs) per biopsy: normal, benign breast disease, and cancer. Local and global mammographic density volumes were quantified in the ipsilateral breast in pre-biopsy full-field digital mammograms. Associations of fibrillar collagen features with mammographic density and severity of biopsy diagnosis were evaluated using generalized estimating equation models with an independent correlation structure to account for multiple ROIs within each biopsy section.

Results

Collagen fiber density was positively associated with the proportion of stroma on the biopsy slide (p < 0.001) and with local percent mammographic density volume at both the biopsy target (p = 0.035) and within a 2 mm perilesional ring (p = 0.02), but not with global mammographic density measures. As severity of the breast biopsy diagnosis increased at the ROI level, collagen fibers tended to be less dense, shorter, straighter, thinner, and more aligned with one another (p < 0.05).

Conclusions

Collagen fiber density was positively associated with local, but not global, mammographic density, suggesting that collagen microarchitecture may not translate into macroscopic mammographic features. However, collagen fiber features may be markers of cancer risk and/or progression among women referred for biopsy based on abnormal breast imaging.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01482-z.

Morphometric analysis of the His bundle (atrioventricular fascicle) in humans and other animal species. Histological and immunohistochemical study

The His bundle is a part of the specialized electrical conduction system that provides a connection between the atrial and ventricular myocardial compartments in both normal and abnormal hearts. The aim of this study was to perform a morphometric analysis of His bundle characteristics of in humans, dogs, horses and pigs and compare them in these studied species. Histological sections of 5 μm thickness were obtained and stained with hematoxylin-eosin and Masson's trichrome; the desmin and periodic acid-Schiff methods were also used for precise identification of cells. The His bundle was found to be longer in horses (2.85 ± 1.02 mm) and pigs (1.77 ± 0.9 mm) than in dogs (1.53 ± 0.8 mm) or humans, in which it was shortest (1.06 ± 0.6 mm). The area and diameters in His bundle cells, were significantly larger in pigs and horses than in humans (p < 0.001) or dogs (p < 0.001). We found two organizational patterns of His bundle components: group I, with large cells and a high amount of collagen fibers in ungulates (pigs and horses); and group II, with smaller cells and lower abundance of collagen fibers in humans and dogs. Documenting cell size variations in the His bundle allows us not only to identify this bundle by histological or anatomical location but also to differentiate these cells from others such as nodal or Purkinje cells. Our analysis revealed that His bundle cells have discrete identities based on their morphometric and histological characteristics.

Histologic composition of marginal mucosal tissue augmented by a resorbable volume-stable collagen matrix in soft tissue thickening procedures in humans: a morphometric observational study

AIM

This study aims to examine the composition of lining and masticatory mucosa at the pre- and post-soft tissue augmentation procedures with a volume-stable cross-linking collagen matrix (VCMX) in humans.

MATERIALS AND METHODS

In 12 patients, single implant sites were augmented with a VCMX. Biopsies were obtained including masticatory (MM) and lining (LM) mucosa before augmentation and at 12 weeks post-augmentation procedures. Rete pegs density (RPD), length (RPL), and blood vessel density (BVD) were histomorphometrically analyzed at both time points. Picrosirius red staining under polarized light microscopy was used to evaluate collagen fiber organization. The effects of time and tissue type were evaluated by ANOVA with repeated measures.

RESULTS

Both MM and LM areas demonstrated an increase in mean RPL following augmentation, 382.6 µm ± 95.1 vs. 290.5 µm ± 79.3 and 335.6 µm ± 94.2 vs. 292.9 µm ± 77.0, respectively (p < .05). There was a significant difference in the numbers of RP per 1 mm length (RPD) between the MM (9.2 ± 1.7) and LM (6.1 ± 2.8) mucosa but not between the pre- and post-VCMX augmentation time points. The mean BVD in the LM was greater than in the MM (5.5 ± 2.4 and 6.3 ± 2.4 vs. 3.4 ± 3.3 and 3.7 ± 1.8, respectively, p < .05) but not between time points. The collagen fiber arrangements pre- and post-augmentation were not significantly different.

CONCLUSION

Augmentation with VCMX did not alter the composition of lining and masticatory mucosa at implant sites.

CLINICAL RELEVANCE

A thick soft tissue phenotype around the implant neck is an important factor to maintain peri-implant health. A non-autogenous cross-linking collagen matrix is proposed as an alternate graft substitute in soft tissue augmentation procedures in order to improve implant soft tissue phenotype.

Evaluation of affine fiber kinematics in porcine tricuspid valve leaflets using polarized spatial frequency domain imaging and planar biaxial testing

Collagen fibers are the primary load-bearing microstructural constituent of bodily soft tissues, and, when subjected to external loading, the collagen fibers reorient, uncrimp, and elongate. Specific to the atrioventricular heart valve leaflets, the collagen fiber kinematics form the basis of many constitutive models; however, some researchers claim that modeling the affine fiber kinematics (AFK) are sufficient for accurately predicting the macroscopic tissue deformations, while others state that modeling the non-affine kinematics (i.e., fiber uncrimping together with elastic elongation) is required. Experimental verification of the AFK theory has been previously performed for the mitral valve leaflets in the left-side heart; however, this same evaluation has yet to be performed for the morphologically distinct tricuspid valve (TV) leaflets in the right-side heart. In this work, we, for the first time, evaluated the AFK theory for the TV leaflets using an integrated biaxial testing-polarized spatial frequency domain imaging device to experimentally quantify the load-dependent collagen fiber reorientations for comparison to the AFK theory predictions. We found that the AFK theory generally underpredicted the fiber reorientations by 3.1°, on average, under the applied equibiaxial loading with greater disparity when the tissue was subjected to the applied non-equibiaxial loading. Furthermore, increased AFK errors were observed with increasing collagen fiber reorientations (Pearson coefficient r = -0.36, equibiaxial loading), suggesting the AFK theory is better suited for relatively smaller reorientations. Our findings suggest the AFK theory may require modification for more accurate predictions of the collagen fiber kinematics in the TV leaflets, which will be useful in refining modeling efforts for more accurate TV simulations.

The morphological and microscopical characteristics of posterior layer of human thoracolumbar fascia; A potential source of low back pain

BACKGROUND

Posterior layer of thoracolumbar fascia (PTLF) is the deep fascia of back of the trunk, which connects the trunk, upper limb and lower limb muscles. Very few cadaveric studies of posterior layer of thoracolumbar fascia (PTLF) are found in the literature, which mention the presence of nerve receptors in it but, quantification of the nerve receptors where not found. Providing the morphological and morphometrical data of PTLF may help the exercise physiologists, sports physicians, occupational health assistants and, physiotherapists to modify or invent new protocol of treatment to help the society.

METHODS

In this study, twenty formalin embalmed human cadavers were used and we have documented the orientation of the PTLF and quantified the number of peripheral nerve endings at the different vertebral levels.

RESULTS

Mean distance of PTLF from vertebral spines to the musculofascial junction was at thoracic region 3.38cm and 3.34cm; at lumbar region, it was 7.4cm and 7.36cm and at sacral region it was 2.98cm and 2.96cm on right and left side, respectively. The angulation of PTLF varies from 18-110 degrees at different vertebral levels. The microscopic data shows the thickness of PTLF and number of nerve endings in the sacral level is increased compared to that of thoracic vertebral levels.

CONCLUSIONS

We have contributed the novel morphological and microscopical details to the limited existing data on PTLF. We also have provided the quantitative data of nerve fibers, which are possible nociceptors of PTLF.

Biomechanical properties of acellular scar ECM during the acute to chronic stages of myocardial infarction

After myocardial infarction (MI), the infarcted tissue undergoes dynamic and time-dependent changes. Previous knowledge on MI biomechanical alterations has been obtained by studying the explanted scar tissues. In this study, we decellularized MI scar tissue and characterized the biomechanics of the obtained pure scar ECM. By thoroughly removing the cellular content in the MI scar tissue, we were able to avoid its confounding effects. Rat MI hearts were obtained from a reliable and reproducible model based on permanent left coronary artery ligation (PLCAL). MI heart explants at various time points (15 min, 1 week, 2 weeks, 4 weeks, and 12 weeks) were subjected to decellularization with 0.1% sodium dodecyl sulfate solution for ~1-2 weeks to obtain acellular scar ECM. A biaxial mechanical testing system was used to characterize the acellular scar ECM under physiologically relevant loading conditions. After decellularization, large decrease in wall thickness was observed in the native heart ECM and 15 min scar ECM, implying the collapse of cardiomyocyte lacunae after removal of heart muscle fibers. For scar ECM 1 week, 2 weeks, and 4 weeks post infarction, the decrease in wall thickness after decellularization was small. For scar ECM 12 weeks post infarction, the reduction amount of wall thickness due to decellularization was minimal. We found that the scar ECM preserved the overall mechanical anisotropy of the native ventricle wall and MI scar tissue, in which the longitudinal direction is more extensible. Acellular scar ECM from 15 min to 12 weeks post infarction showed an overall stiffening trend in biaxial behavior, in which longitudinal direction was mostly affected and manifested with a decreased extensibility and increased modulus. This reduction trend of longitudinal extensibility also led to a decreased anisotropy index in the scar ECM from the acute to chronic stages of MI. The post-MI change in biomechanical properties of the scar ECM reflected the alterations of collagen fiber network, confirmed by the histology of scar ECM. In short, the reported structure-property relationship reveals how scar ECM biophysical properties evolve from the acute to chronic stages of MI. The obtained information will help establish a knowledge basis about the dynamics of scar ECM to better understand post-MI cardiac remodeling.

Tracking tendon fibers to their insertion - a 3D analysis of the Achilles tendon enthesis in mice

Tendon insertions to bone are heavily loaded transitions between soft and hard tissues. The fiber courses in the tendon have profound effects on the distribution of stress along and across the insertion. We tracked fibers of the Achilles tendon in mice in micro-computed tomographies and extracted virtual transversal sections. The fiber tracks and shapes were analyzed from a position in the free tendon to the insertion. Mechanically relevant parameters were extracted. The fiber number was found to stay about constant along the tendon. But the fiber cross-sectional areas decrease towards the insertion. The fibers mainly interact due to tendon twist, while branching only creates small branching clusters with low levels of divergence along the tendon. The highest fiber curvatures were found within the unmineralized entheseal fibrocartilage. The fibers inserting at a protrusion of the insertion area form a distinct portion within the tendon. Tendon twist is expected to contribute to a homogeneous distribution of stress among the fibers. According to the low cross-sectional areas and the high fiber curvatures, tensile and compressive stress are expected to peak at the insertion. These findings raise the question whether the insertion is reinforced in terms of fiber strength or by other load-bearing components besides the fibers. STATEMENT OF SIGNIFICANCE: The presented study is the first analysis of the 3D fiber tracks in macroscopic tendon samples as determined by a combination of cell-maceration, phase-contrast µCT and template-based tracking. The structural findings change the understanding of the tendon-bone insertion and its biomechanics: (1) The insertion is not reinforced in terms of fiber numbers or sizes. Its robustness remains unexplained. (2) The orientation of fibers in the tendon center is higher than in the margins. This arrangement could inspire material development. (3) Fibers inserting at a protrusion of the insertion area stem from a distinct portion within the tendon. The results show that fibrous structure analysis can link macro- to micromechanics and that it is ready for the application to complete muscle-tendon units.

Macroscopic and Histological Morphology of the Equine Digital Cushion and Its Association with Subcutaneous Fat Thickness

This study evaluated the influence of the Body Condition Score (BCS) and subcutaneous fat thickness on the tissue composition of the digital cushion in horses. Sixty mixed breeds of Criollo horses (21 males and 39 females) were sent for slaughter. All animals were submitted to BCS analysis, through visual antemortem evaluation, and then ultrasound evaluation to estimate the subcutaneous fat thickness. Macroscopic analyses of the thoracic and a pelvic limb (weight, volume, and density of the hooves and digital cushions) were performed. In addition, measurements of the area of internal structures to the hoof and histological analyzes were carried out to measure the areas of adipose, fibroelastic, and collagen fibers of the digital cushion. There were no macroscopic differences in the digital cushion between thoracic and pelvic limbs or between genders (P > .05). Likewise, the histological characteristics between the limbs and the genders were similar (P > .05). There was no correlation between the weight, volume, and density of the digital cushion with the BCS (P > .05). A positive correlation was observed with the area of adipose tissue (P = .038, R² = 0.28) and a negative correlation with area of fibroelastic tissue (P = .005, R² = -0.37) and collagen fibers (P = .003, R² = -0.39). In conclusion, the adipose tissue, fibroelastic tissue, and collagen fibers of equine digital cushion alter their areas in the functions of the various subcutaneous fat patterns in horses.

Effect of age on the failure properties of human meniscus: High-speed strain mapping of tissue tears

The knee meniscus is a soft fibrous tissue with a high incidence of injury in older populations. The objective of this study was to determine the effect of age on the failure behavior of human knee meniscus when applying uniaxial tensile loads parallel or perpendicular to the primary circumferential fiber orientation. Two age groups were tested: under 40 and over 65 years old. We paired high-speed video with digital image correlation to quantify for the first time the planar strains occurring in the tear region at precise time points, including at ultimate tensile stress, when the tissue begins losing load-bearing capacity. On average, older meniscus specimens loaded parallel to the fiber axis had approximately one-third less ultimate tensile strain and absorbed 60% less energy to failure within the tear region than younger specimens (p < 0.05). Older specimens also had significantly reduced strength and material toughness when loaded perpendicular to the fibers (p < 0.05). These age-related changes indicate a loss of collagen fiber extensibility and weakening of the non-fibrous matrix with age. In addition, we found that when loaded perpendicular to the circumferential fibers, tears propagated near the planes of maximum tensile stress and strain. Whereas when loaded parallel to the circumferential fibers, tears propagated oblique to the loading axis, closer to the planes of maximum shear stress and strain. Our experimental results can assist the selection of valid failure criteria for meniscus, and provide insight into the effect of age on the failure mechanisms of soft fibrous tissue.

A novel eco-friendly imidazole ionic liquids based amphoteric polymers for high performance fatliquoring in chromium-free tanned leather production

The potential environmental pollution of chrome tanned leather results in the development of ecological chromium-free leather tanning production in leather industry. However, with weakly positive charge, chromium-free tanned leather cannot strongly bind to anionic dyes, thus causing low quality of finished leather. Herein, p(DM-co-[DDVIM]Br)PS was synthesized by free radical polymerization method. The structure and properties of the targeted products were synthetically characterized. The results indicated that the use of p(DM-co-[DDVIM]Br)PS fatliquoring agent can not only make leather fibers become loose, but also improve the binding affinity between leather and anionic dye during the fatliquoring process. The fatliquoring agent adsorption rates and the dye absorption rate of the leather were as high as 99.26% and 99.01%, respectively; the fatliquoring and dye solutions were clear, so they can be used as clean materials in the fatliquoring process of chromium-free tanned leather. Leather treated with p(DM-co-[DDVIM]Br)PS fatliquoring agent had higher K/S value (12.80) and is softer than those treated with commercial fatliquoring agent. Consequently, this study can not only help improve the absorption rate of anionic wet finishing materials, but also reduce the pollution caused by chrome tanning agents, thus providing a new way for the cleaner production in leather industry.

Degradation of subchondral bone collagen in the weight-bearing area of femoral head is associated with osteoarthritis and osteonecrosis

Background

The aim of the study was to evaluate the change of subchondral bone collagen and trabecular bone in the weight-bearing area of femoral head from patients with osteoarthritis (OA) or osteonecrosis of femoral head (ONFH), and discuss the effect of collagen degradation on OA and ONFH.

Methods

Femoral heads from patients with femoral neck fracture (FNF) were collected as control group. All collected samples were divided into OA group (N = 10), ONFH group (N = 10), and FNF group (N = 10). Differences of subchondral bone collagen were compared through scanning electron microscope (SEM) observation, immunohistochemistry staining, and Masson’s trichrome staining. Alteration of subchondral bone was displayed through hematoxylin and eosin (H&E) staining and gross morphology.

Results

SEM results showed that collagen fibers in OA and ONFH group appeared to be thinner, rougher, sparser, and more wizened. Immunohistochemistry and Masson’s trichrome staining results demonstrated that the content of collagen fibers in the OA and ONFH group was obviously less than the FNF group. H&E staining results showed that trabecular bone in OA and ONFH group appeared to be thinner and ruptured. Gross morphology results showed that the degeneration and destruction of cartilage and subchondral bone in OA and ONFH group were severer than FNF group. The characteristics mentioned above in ONFH group were more apparent than OA group.

Conclusions

This study revealed that degradation of collagen fibers from subchondral bone in the weight-bearing area of femoral head was associated with OA and ONFH, which may help to find new therapeutic strategies of the diseases.

Protein solubility, secondary structure and microstructure changes in two types of undenatured type II collagen under different gastrointestinal digestion conditions

Sodium dodecyl sulfonate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism spectroscopy (CD), transmission electron microscope (TEM) and atomic force microscope (AFM) were used to analyze the structural properties and gastrointestinal digestive characteristics of natural insoluble undenatured type II collagen (IC II) and pepsin soluble undenatured type II collagen (SC II). Results showed that, after gastric digestion, especially under low pH conditions, some thick and short collagen fibers were dissolved from IC II, which was accompanied by the release of soluble protein with triple helix structure. As to SC II, when gastric digestion was performed under higher pH conditions, collagen fibers were mildly thinned and curved, and the triple helix structure was slightly destroyed. However, those changes hardly occurred during the intestinal digestion. Moreover, the undenatured type II collagen existing in SC II digestive supernatant was 1.2-12.4 times higher than that of IC II depending on the pH conditions. These results suggested that, it is more likely for SC II to exert its activity of relieving arthritis, and it should be taken when the pH of gastric environment is high.

Quantification of load-dependent changes in the collagen fiber architecture for the strut chordae tendineae-leaflet insertion of porcine atrioventricular heart valves

Atrioventricular heart valves (AHVs) regulate the unidirectional flow of blood through the heart by opening and closing of the leaflets, which are supported in their functions by the chordae tendineae (CT). The leaflets and CT are primarily composed of collagen fibers that act as the load-bearing component of the tissue microstructures. At the CT-leaflet insertion, the collagen fiber architecture is complex, and has been of increasing focus in the previous literature. However, these previous studies have not been able to quantify the load-dependent changes in the tissue's collagen fiber orientations and alignments. In the present study, we address this gap in knowledge by quantifying the changes in the collagen fiber architecture of the mitral and tricuspid valve's strut CT-leaflet insertions in response to the applied loads by using a unique approach, which combines polarized spatial frequency domain imaging with uniaxial mechanical testing. Additionally, we characterized these microstructural changes across the same specimen without the need for tissue fixatives. We observed increases in the collagen fiber alignments in the CT-leaflet insertion with increased loading, as described through the degree of optical anisotropy. Furthermore, we used a leaflet-CT-papillary muscle entity method during uniaxial testing to quantify the chordae tendineae mechanics, including the derivation of the Ogden-type constitutive modeling parameters. The results from this study provide a valuable insight into the load-dependent behaviors of the strut CT-leaflet insertion, offering a research avenue to better understand the relationship between tissue mechanics and the microstructure, which will contribute to a deeper understanding of AHV biomechanics.

Mast cells and collagen fibrillogenesis

This article presents 20 combinations of histochemical stainings for the determination of mast cell co-localization with the fibrous component of the connective tissue in the fibrillogenesis course. Best results were obtained using metachromatic detection of mast cells in combination with silver or picro-fuchsin impregnation, staining with brilliant green using van Gieson staining, and a combination of aniline blue staining with neutral red. Proposed variants of histochemical protocols open up new opportunities to analyze the participation of mast cells in extracellular matrix remodeling of the tissue microenvironment in the course of adaptive and pathological processes. Results obtained expand the current theoretical views of the process of fibrillogenesis in the extracellular matrix. They also shed new light on the participation of mast cell secretion components in the molecular mechanisms of fiber formation.

Effects of electromechanical reshaping on mechanical behavior of exvivo bovine tendon

BACKGROUND

Electromechanical reshaping is a novel, minimally invasive means to induce mechanical changes in connective tissues, and has the potential to be utilized in lieu of current orthopedic therapies that involve tendons and ligaments. Electromechanical reshaping delivers an electrical current to tissues while under mechanical deformation, causing in situ redox changes that produce reliably controlled and spatially limited mechanical and structural changes. In this study, we examine the feasibility of altering Young's modulus and inducing a shape deformation using an ex vivo bovine Achilles tendon model.

METHODS

Tendon was mechanically deformed in two different modes: (1) elongation to assess for tensile modulus and (2) compression to assess for compressive modulus. Electromechanical reshaping was applied to tendon specimens via flat plate platinum electrodes (6 V, 3 min) while simultaneously under mechanical strain for 15 min.

FINDINGS

In elongation mode, post-electromechanical reshaping samples demonstrated a significant decrease in Young's modulus compared to pretreatment samples (66.02 and 45.12 MPa, respectively, p < 0.0049). In compression mode, posttreatment samples illustrated a significant shape change, with an increase in diameter (10.62 to 11.36 mm, p < 0.05) and decrease in thickness (4.13 to 3.62 mm, p < 0.05).

INTERPRETATION

Results demonstrated a tissue softening effect without lengthening deformation during elongation, and a shortening effect without compromising compressive stiffness during compression. Electromechanical reshaping's reliable, low-cost, and efficacious methodology in inducing mechanical and structural connective tissue modifications illustrates a potential for future alternative orthopedic applications. Future studies will optimize and refine electromechanical reshaping to address clinically relevant geometries and methods such as needle techniques.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

CD248 and integrin alpha-8 are candidate markers for differentiating lung fibroblast subtypes

Background

Lung fibrosis is a serious life-threatening condition whose manifestation varies according to the localization and characteristics of fibroblasts, which are considered heterogeneous. Therefore, to better understand the pathology and improve diagnosis and treatment of this disease, it is necessary to elucidate the nature of this heterogeneity and identify markers for the accurate classification of human lung fibroblast subtypes.

Methods

We characterized distinct mouse lung fibroblast subpopulations isolated by fluorescence-activated cell sorting (FACS) and performed microarray analysis to identify molecular markers that could be useful for human lung fibroblast classification. Based on the expression of these markers, we evaluated the fibroblast-like cell subtype localization in normal human lung samples and lung samples from patients with idiopathic pulmonary fibrosis (IPF).

Results

Mouse lung fibroblasts were classified into Sca-1^high fibroblasts and Sca-1^low fibroblasts by in vitro biological analyses. Through microarray analysis, we demonstrated CD248 and integrin alpha-8 (ITGA8) as cell surface markers for Sca-1^high fibroblasts and Sca-1^low fibroblasts, respectively. In mouse lungs, Sca-1^high fibroblasts and Sca-1^low fibroblasts were localized in the collagen fiber-rich connective tissue and elastic fiber-rich connective tissue, respectively. In normal human lungs and IPF lungs, two corresponding major fibroblast-like cell subtypes were identified: CD248^highITGA8^low fibroblast-like cells and CD248^lowITGA8^high fibroblast-like cells, localized in the collagen fiber-rich connective tissue and in the elastic fiber-rich connective tissue, respectively.

Conclusion

CD248^highITGA8^low fibroblast-like cells and CD248^lowITGA8^high fibroblast-like cells were localized in an almost exclusive manner in human lung specimens. This human lung fibroblast classification using two cell surface markers may be helpful for further detailed investigations of the functions of lung fibroblast subtypes, which can provide new insights into lung development and the pathological processes underlying fibrotic lung diseases.

Histological evaluation of the acetabular labrum after bipolar hip hemiarthroplasty: a case report

We report herein the microstructure of the acetabular labrum obtained from a patient with stem loosening but without bipolar cup migration who had undergone hemiarthroplasty for femoral neck fracture 18 years ago. We used light and scanning electron microscopy to investigate the influence of bipolar cup on acetabular labrum in vivo. Deparaffinized blocks were treated with 2 N NaOH to digest the cell matrix, allowing the collagen fibers, constituting the acetabular labrum, to be observed under scanning electron microscopy. Although chondrocyte atrophy was seen, the basic structure was not different from the normal tissue images of the elderly. However, in the deep part of the acetabular labrum, there was an area that was not stained with Alcian blue observed with light microscopy, and there was an amorphous tissue without type II collagen fibrils observed with scanning electron microscopy. These findings proved that the acetabular labrum has partially degenerated over the long term after bipolar hemiarthroplasty, and that the acetabular labrum can survive in vivo in such a condition. Given that hemiarthroplasty has a possibility to preserve the face-to-face tissue in the long term in vivo, it may be one of the valuable options for modern or future joint reconstruction surgery.

Topical application of silk fibroin-based hydrogel in preventing hypertrophic scars

Current medications for the treatment of hypertrophic scars suffer from bottlenecks of limited therapeutic efficacy and a slow recovery rate. Silk fibroin (SF) has gained attention for its ability to promote wound healing in burns and cutaneous wounds, but its therapeutic effects against hypertrophic scar have not been thoroughly investigated. We prepared SF-based hydrogels (SFHs) with various SF concentrations (1.5 %, 3 %, and 6 %) and characterized their physicochemical properties. Cell experiments showed that these SFHs had favorable biocompatibility in vitro. Further animal experiments in rabbits revealed that the SFH (3 %)-treated group achieved scars on their ears that were thinner and significantly lighter in color compared with the negative control group. Moreover, treatment with SFHs reduced the density and led to the orderly arrangement of collagen fibers. It was found that the therapeutic effects of SFHs were attributed to the reduced expression levels of α-smooth muscle actin. These results are the first to demonstrate that SFH can be exploited as an effective therapeutic agent for the treatment of hypertrophic scars.

Migration dynamics of ovarian epithelial cells on micro-fabricated image-based models of normal and malignant stroma

A profound remodeling of the collagen in the extracellular matrix (ECM) occurs in human ovarian cancer but it is unknown how this affects migration dynamics and ultimately tumor growth. Here, we investigate the influence of collagen morphology on ovarian cell migration through the use of second harmonic generation (SHG) image-based models of ovarian tumors. The scaffolds are fabricated by multiphoton excited (MPE) polymerization, where the process is akin to 3D printing except it achieves much greater resolution (∼0.5 µm) and utilizes collagen and collagen analogs. We used this technique to create scaffolds with complex 3D submicron features representing the collagen fiber morphology in normal stroma, high risk stroma, benign tumors, and high grade ovarian tumors. We found the highly aligned malignant stromal structure promoted enhanced motility and also increased cell and f-Actin alignment relative to the other tissues. However, using models based on fiber crimping characteristics, we found cells seeded on linear fibers based on normal stromal models yielded the highest degree of alignment but least motility. These results show that both the fiber properties themselves and as well as their overall alignment govern the resulting migration dynamics. These models cannot be synthesized by other conventional fabrication methods and we suggest the MPE image-based fabrication method will enable a variety of studies in cancer biology. STATEMENT OF SIGNIFICANCE: The extracellular matrix collagen in ovarian cancer is highly remodeled but the consequences on cell function remain unknown. It is important to understand the operative cell matrix interactions, as this could lead to better prognostics and better prediction of therapeutic efficacy. We probe migration dynamics using high resolution (∼0.5 µm) multiphoton excited fabrication to synthesize scaffolds whose designs are derived directly from Second Harmonic Generation microscope images of the collagen in normal ovarian tissues as well as benign and malignant tumors. Collectively our results show the importance of the matrix morphology (fiber shape and alignment) on driving cell motility, cell shape and f-Actin alignment. These collagen-based models have complex fiber morphology and cannot be created by conventional fabrication technologies.

The architecture and spatial organization of the living human body as revealed by intratissular endoscopy - An osteopathic perspective

This article presents an overview of research conducted by Dr Jean-Claude Guimberteau into the architecture and spatial organization of living matter and the relationship between the cells and the extracellular matrix. His research is discussed in the context of previous and current research into fascial anatomy. Andrew Taylor Still, the founder of Osteopathy, did not have access to modern research and yet his observations are proving to be surprisingly accurate in the light of recent findings. This article sets out to highlight the relevance of his insights from a purely anatomical perspective, and to draw parallels with a new way of thinking about the architecture of the living human body that is slowly emerging. Dr Guimberteau's research shows that a force applied to the surface of the skin is transmitted deep into living tissue via a continuous bodywide multifibrillar network. It also confirms the concept of the body as a dynamic functional unit, as proposed by A.T. Still. Still also proposed that structure and function are interrelated at all levels within the living human body. There is a growing body of research to support this. Intratissular endoscopy has highlighted the importance of the quality of the mobility and adaptability of the network of collagen and elastin fibers that structures the ECM in healthy living tissue. Factors such as abnormal stiffness of collagen fibers in the ECM are thought to have adverse effects on local tissue health.

P-cadherin-induced decorin secretion is required for collagen fiber alignment and directional collective cell migration

Directional collective cell migration (DCCM) is crucial for morphogenesis and cancer metastasis. P-cadherin (also known as CDH3), which is a cell-cell adhesion protein expressed in carcinoma and aggressive sarcoma cells and associated with poor prognosis, is a major DCCM regulator. However, it is unclear how P-cadherin-mediated mechanical coupling between migrating cells influences force transmission to the extracellular matrix (ECM). Here, we found that decorin, a small proteoglycan that binds to and organizes collagen fibers, is specifically expressed and secreted upon P-cadherin, but not E- and R-cadherin (also known as CDH1 and CDH4, respectively) expression. Through cell biological and biophysical approaches, we demonstrated that decorin is required for P-cadherin-mediated DCCM and collagen fiber orientation in the migration direction in 2D and 3D matrices. Moreover, P-cadherin, through decorin-mediated collagen fiber reorientation, promotes the activation of β1 integrin and of the β-Pix (ARHGEF7)/CDC42 axis, which increases traction forces, allowing DCCM. Our results identify a novel P-cadherin-mediated mechanism to promote DCCM through ECM remodeling and ECM-guided cell migration.