Search Results (167)

Background: The structural integrity of the abdominal wall is critically dependent on the organization of aponeurotic tissue, a dense collagen-rich connective structure responsible for directional force transmission. While the clinical relevance of the aponeurosis is well recognized in abdominal wall reconstruction, its nano-scale structural organization remains insufficiently characterized. Atomic force microscopy (AFM) provides a suitable approach for investigating surface morphology and nano-architectural features of biological tissues. Methods: Human aponeurotic tissue samples were analyzed using atomic force microscopy operated in contact-mode deflection and topography imaging. Two-dimensional and three-dimensional surface topographies were acquired at the micrometer scale to assess nano-architectural organization. Areal surface roughness parameters (Sa, Sq, Sp, Sv, Sy) were calculated to quantify morphological heterogeneity. AFM deflection imaging was used to evaluate relative spatial variations in deflection imaging contrast under the applied scanning conditions across collagen-dense and interfibrillar regions. Results: AFM analysis revealed a well-organized fibrillar architecture with preferential orientation, consistent with the anisotropic organization of aponeurotic connective tissue. Deflection images demonstrated spatial heterogeneity in deflection contrast at the scanned scale, reflecting variations in the tip–sample interaction signal between collagen-dense and interfibrillar regions. Surface topography showed a continuous morphology with moderate height variations and smooth transitions between structural elements. Roughness parameters reflected a compact extracellular matrix organization within the scanned areas, without features suggestive of surface disruption. Conclusions: Atomic force microscopy enables detailed nano-scale structural characterization of human aponeurotic tissue and reveals spatial heterogeneity in deflection imaging contrast under specific contact-mode scanning conditions. These findings provide a baseline nano-scale descriptive reference dataset for macroscopically normal aponeurotic tissue, supporting future comparative investigations without implying validated mechanical differences or direct tissue–implant interaction analysis within the present study. Full article

Background and Objectives: Extracellular matrix (ECM) and collagen remodeling contribute to chronic kidney disease (CKD) progression and vascular access dysfunction. Conventional histological techniques rely on staining and provide limited sensitivity for detecting early or subtle ECM alterations. Nonlinear optical imaging modalities, including second-harmonic generation (SHG), third-harmonic generation (THG), and multiphoton fluorescence (MPF) microscopy, enable label-free, high-resolution visualization of fibrillar collagen and may offer additional structural information. This study aimed to evaluate the added value of nonlinear imaging beyond conventional histology for assessing ECM remodeling in renal and vascular tissues. Materials and Methods: A systematic literature review was conducted in accordance with the PRISMA 2020 guidelines. PubMed and Web of Science were searched for studies published between 1 January 2015, and 4 April 2025, investigating ECM or collagen remodeling in renal or vascular tissues using SHG, THG, or MPF microscopy. After screening 115 records, 10 studies were included in the qualitative synthesis. In addition, representative SHG, THG, and MPF images of excised human arteriovenous fistula (AVF) tissue were acquired as illustrative feasibility examples to demonstrate the application of these imaging modalities. The use of human tissue was approved by the Vilnius Regional Biomedical Research Ethics Committee (approval No. 2022/6-1443-917). Results: The included studies demonstrated that nonlinear microscopy enables label-free assessment of collagen density, organization, and fiber orientation. SHG imaging differentiated healthy from diseased tissues and has been reported to support fibrosis assessment and staging in preclinical and selected clinical studies and revealed microstructural remodeling patterns not readily detected by conventional histology. The illustrative AVF images demonstrated collagen disorganization consistent with patterns reported in the reviewed literature and are presented solely to demonstrate imaging feasibility, without implying disease phenotype or clinical outcome associations. Conclusions: Nonlinear optical microscopy provides complementary structural information on ECM organization that is not accessible with standard histological techniques. Further validation and methodological standardization are required to support its broader application in clinical nephrology and vascular medicine. Full article

Non-alcoholic fatty liver disease (NAFLD) is a silent condition that can lead to fatal cirrhosis, with dietary factors playing a central role. The effect of various dietary interventions on male Wistar rats were evaluated in four diets: control, arsenic, sucrose, and arsenic–sucrose. SHG microscopy images from the right ventral lobe of the liver tissue were analyzed with a neural network trained to detect the presence or absence of collagen fibers, followed by the assessment of their orientation and angular distribution. Machine learning classification of SHG microscopy images revealed a marked increase in fibrosis risk with dietary interventions: <10% in controls, 24% with arsenic, 40% with sucrose, and 62% with combined arsenic–sucrose intake. Angular width distribution of collagen fibers narrowed dramatically across groups: 26° (control), 24° (arsenic), 15.7° (sucrose), and 2.8° (arsenic–sucrose). This analysis revealed four key statistical features for classifying the images according to the presence or absence of collagen fibers: (1) the percentage of pixels whose intensity is above the 15% noise threshold, (2) the Mean-to-Standard Deviation ratio (Mean/std), (3) the mode, and (4) the total intensity (sum). These results demonstrate that a diet rich in sucrose, particularly in combination with arsenic, constitutes a significant risk factor for liver collagen fiber remodeling. Full article

Segment regeneration in earthworms is a remarkable example of postembryonic morphogenesis, yet its fidelity and cellular mechanisms remain incompletely understood. The present study investigated posterior segment regeneration in adult specimens of the earthworm model Eisenia andrei from wound closure to the 5th postoperative week using anatomical, histological, and ultrastructural approaches. Rapid wound closure occurred through fusion of the cut edges of the body wall and midgut without direct involvement of coelomocytes. The regeneration blastema consisted of dedifferentiated epithelial and muscle cells, innervated by fibers from the last intact ventral nerve cord ganglion. Coelomocytes accumulated in the last intact segments and were primarily involved in debris clearance. Notably, early regenerating tissues lacked collagen fibers, which appeared only after the third postoperative week and remained sparse until the fifth week, whereas original segments exhibited intense, region-specific collagen deposition. Transmission electron microscopy revealed characteristic cytological changes in distinct stages of body wall regeneration, including muscle dedifferentiation and the emergence of collagen-producing fibroblasts. These findings indicate that early cell migration, proliferation, and orientation in the blastema proceed independently of collagen and that collagen functions as a delayed structural scaffold, supporting tissue integrity without impeding regeneration. Importantly, no scar formation was observed between old and new tissues, resembling scarless fetal wound healing. Overall, we clarified previously controversial cellular mechanisms and propose a new, comprehensive model for the early stages of segment regeneration. Our results highlight that coordinated dedifferentiation, spatiotemporal extracellular remodeling, and delayed collagen deposition underlie effective, scar-free regeneration in earthworms, offering insights into conserved mechanisms of regenerative repair across metazoans and potential strategies for enhancing tissue regeneration in mammals. Full article

Skin meshing is widely used to treat extensive burn injuries due to its cost-efficiency and capacity to cover large wound areas. As biomimetics focuses on deriving engineering principles from biological structure–function relationships, this review examines how to optimize skin-meshing expansion and investigates factors contributing to reported discrepancies between clinical and manufacturer-reported expansion ratios. The biology and mechanical behavior of skin layer are discussed, emphasizing the anisotropic properties govern by collagen fiber orientation associated with Langer’s lines in the dermis. The epidermis and hypodermis show isotropic properties and therefore have minimal influence on load-bearing capacity. Surveying 111 studies, the review evaluates which constitutive equations employed for skin modelling is suitable to replicate mechanical behavior of skin meshing undergoing large expansion. Elastic models fail to capture large expansion ratios. Viscoelastic and QLV are excluded due to negligible sliding of collagen fibers at slow strain rates and limited importance of hysteresis. Consequently, hyperelastic models are recognized as more suitable for predicting large deformations. Among these, the structural GOH model, which represents fiber dispersion through a probability-density function, demonstrates strong agreement with experimental data using few parameters; its damage extensions improve prediction of mesh tearing. Additionally, emerging auxetic mesh geometries with negative Poisson ratios are examined, highlighting their potential to achieve greater expansion when combined with suitable structural anisotropic constitutive models, e.g., GOH. Full article

Bone is one of the most important organs of mammals, consisting of collagen and apatite. Various diseases, such as osteoporosis, can affect the components of bone tissue, their chemical composition and bone ultrastructure, which leads to changes in properties. In this paper, the effect of initial osteoporosis on the chemical composition of bone apatite and the ultrastructure of bone tissue from a mineralogical point of view is analyzed using rat femurs as an example. The chemical composition of bone apatite was studied using SEM, EDS and FTIR-ATR spectroscopy. The bone ultrastructure was examined using a transmission electron microscope. An increase in the content of carbonate ion in the position of the phosphorus group and a change in the orientation of apatite crystals inside mineral plates were revealed against the background of initial osteoporosis, which can affect not only the mechanical properties of bone, but also the stability of apatite under biological conditions. Full article

Osteogenesis imperfecta (OI) and Ehlers–Danlos syndrome (EDS) are inherited connective tissue disorders caused by diverse genetic defects, many of which affect collagen biosynthesis. However, the identified genetic variants do not always fully explain the clinical heterogeneity observed in patients, highlighting the need for advanced models and imaging techniques to assess collagen structure and fibroblast behavior at the microscopic level. In this study, we employed 5-week three-dimensional (3D) dermal fibroblast cultures derived from patients with haploinsufficient (HI) and dominant-negative (DN) OI, EDS, and healthy controls. Using label-free higher harmonic generation microscopy (HHGM), we visualized and quantified secreted collagen fibers and fibroblast morphology in situ. We analyzed fibroblast 3D orientation, collagen fiber diameter, collagen amount per cell, and the spatial alignment between fibroblasts and collagen fibers. HI OI fibroblasts secreted significantly less collagen than both control and EDS-derived cells, while EDS samples exhibited thinner collagen fibers compared to controls. Across all groups, collagen fiber orientation was strongly correlated with fibroblast alignment, in line with the role of fibroblasts in matrix organization. In healthy controls and HI OI samples, we observed a depth-dependent, counterclockwise rotation in fibroblast orientation from the culture bottom to the surface—a pattern that was less prominent in DN OI and EDS samples, potentially reflecting altered matrix guidance in diseased tissues. Overall, the quantity and quality of collagen, as well as fibroblast morphology and organization, were markedly altered in the OI and EDS model systems. These alterations may mirror tissue-level manifestations of the diseases, demonstrating the physiological relevance of patient-derived 3D fibroblast models for OI and EDS, as well as the power of harmonic generation microscopy in probing the cellular and extracellular consequences of disease-related gene defects in collagen or its biosynthetic pathways. Extensions of this methodological approach provide a way towards deeper understanding of tissue-level manifestations of collagen dysregulation in connective tissue disorders. Full article

Background/Objective: Soft-tissue volume augmentation with gingival grafts enhances implant-prosthodontic esthetics by maintaining or reconstructing a convex contour of the vestibular mucosa. However, it presents disadvantages related to donor site, surgical complexity, and post-procedural discomfort. This study evaluated clinical performance of a native porcine-derived collagen–elastin matrix with uniquely oriented porous structure for soft-tissue volume augmentation at single implant sites. Method and Materials: Soft-tissue augmentation was performed at sites of a single implant, which underwent immediate, early, or late loading protocols. Implant success, its survival, and mucosal health status including change in tissue thickness acquired through 3D scans of casts prepared from impressions before and after tissue augmentation were evaluated. Biocompatibility of the collagen matrix (CM) was assessed through histological analyses. Results: Forty-five patients received 50 implants with simultaneous augmentation using CM. At the last follow-up (mean 22.1 ± 15.0 months), the peri-implant soft tissue was healthy and stable, and all implants were surviving and successful. Tissue thickness change at augmented sites did not vary with time interval between pre- and post-treatment, indicating stability of augmentation. Soft-tissue biopsies (n = 3) showed healthy peri-implant soft tissue with good vascularization and no inflammation. Conclusions: This retrospective analysis demonstrated good clinical performance and high biocompatibility of CM for soft-tissue volume augmentation around dental implants. Full article

Tissue responses to zirconia-coated implants treated with molecular precursor method were evaluated. The zirconia film was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Cylindrical titanium (ZrO₂/Ti) specimens were sandblasted, acid-etched, and coated with zirconia using the molecular precursor method. Control specimens were sandblasted and acid-etched only (SLA/Ti). After maxillary first molar extraction, four ZrO₂/Ti and four SLA/Ti implants were placed in the alveolar bone of the rats, and tissue responses were observed after 3 weeks. Surface analysis using SEM and AFM showed zirconia was present on ZrO₂/Ti surface, with coating not affecting surface morphology compared to SLA/Ti. EDX, XPS, and XRD measurements confirmed the ZrO₂ coating on the roughened Ti. The amount of new bone was greater in ZrO₂/Ti (77.0 ± 7.2%) than in SLA/Ti (59.7 ± 5.8%) (p = 0.807). Collagen fibers oriented perpendicular to implant surface were observed more frequently in ZrO₂/Ti (67.3 ± 9.5%) than in SLA/Ti (18.8 ± 10.01%) (p < 0.001). The area of perpendicular collagen fibers was significantly larger in ZrO₂/Ti (53.1 ± 13.4%) than in SLA/Ti (16.8 ± 2.6%) (p = 0.002). Zirconia-coated implants maintained surface morphology and improved bone formation and fiber orientation in the gingiva compared to conventional titanium implants in short-term animal experiments. Full article

Skin meshing facilitates the greater expansion of donor skin through patterned slits and is widely used for treating extensive burn injuries. However, the actual expansion often falls below manufacturers’ claims. Previous computational analyses using the isotropic Yeoh model have shown that Langer’s line orientation and slit direction significantly affect induced stress and meshing ratios, yet the use of nonlinear anisotropic models that represent collagen fiber alignment corresponding to Langer’s lines remains unexplored. This study employs a nonlinear anisotropic Gasser–Ogden–Holzapfel (GOH) model with slit orientations of 0°, 45°, and 90°, consistent with geometries reported in the literature, to quantify induced stress in skin meshing by incorporating collagen fibers within the dermis layer. The GOH parameters were calibrated to human back skin data uniaxially stretched parallel and perpendicular to Langer’s lines using Levenberg–Marquardt optimization in the GIBBON toolbox (MATLAB R2023a) coupled with FEBio v4.0, achieving a standard deviation of 3% relative to experimental data. The GOH model predicted the highest induced stress at 100% strain for the 45° slit parallel to Langer’s lines and the lowest for the 90° slit perpendicular, exceeding 40 MPa due to absence of damage and rupture modeling but accurately representing anisotropic mesh behavior. Full article

The myometrium is the smooth muscle layer of the uterus, whose dysfunctions are involved in various pathologies leading to infertility, such as adenomyosis and uterine fibroids. Developing relevant in vitro models of the myometrium is crucial for investigating the pathogenesis of these diseases. In this study, we propose a novel approach for cultivating mouse myometrial smooth muscle cells (SMCs) using plant-derived cellulose scaffolds. The scaffolds were obtained through the decellularization of green onion leaf, celery stalk, or bluegrass leaf, subsequently coated with collagen type I. We found that the structure of the green onion leaf scaffold provides unidirectional orientation of cultured cells, mimicking the tissue-specific organization of mouse myometrial SMCs in vivo. The mouse myometrial SMCs, cultured on this scaffold, proliferated, maintained viability up to 2.5 months, and retained the expression of the main markers of smooth muscle contractility (α-smooth muscle actin, transgelin, calponin, smooth muscle myosin heavy chains, connexin-43). To reproduce the native myometrium structure, a multilayered cultivation system was created. In a system of two overlaying scaffolds, cells also retained the viability and expression of smooth muscle contractility markers. The developed approach can be used for three-dimensional myometrium modeling to study the pathogenesis of myometrium-associated diseases. Full article

Centella asiatica, a widely used medicinal herb in Oriental and increasingly Western medicine, is applied for wound healing, dermatological disorders, and gastrointestinal illness. We investigated the effects of fermented C. asiatica extract (FCAE), prepared with Lactobacillus, on airway inflammation in a murine model of chronic obstructive pulmonary disease (COPD) induced by cigarette smoke extract (CSE) and lipopolysaccharide (LPS). CSE/LPS stimulation caused marked immune cell infiltration in airways. FCAE (100 and 200 mg/kg) reduced neutrophils in the bronchoalveolar lavage fluid (BALF) by 26.03% and 70.11%, respectively, and decreased activated T cells and B cells in the lung, mediastinal lymph nodes, and Peyer’s patches, while inhibiting collagen fibrosis. FCAE significantly reduced IL-1α (32.51%), CXCL1 (47.63%), CXCL2 (45.37%), and TNF-α (39.51%) levels in the BALF compared with the control group. It also downregulated the expression of muc5ac (58.39%), CXCL1 (67.32%), CXCL2 (57.60%), and TNF-α (54.61%) and suppressed p-STAT3 activation by 50.22%. Furthermore, FCAE enhanced tracheal phenol red secretion by 229.62%, indicating expectorant activity. UPLC analysis identified nine components, which, together with FCAE, inhibited RANTES, TNF-α, and IL-6 in inflammation-induced BEAS-2B cells. Overall, FCAE attenuates immune activation and airway inflammation, supporting its potential as a candidate therapy or functional food for respiratory diseases. Full article

Background: This paper aims to provide an overview of corneal birefringence (CB), systematize the knowledge and current understanding of CB, and identify difficulties associated with introducing CB into mainstream clinical practice. Methods: Literature reviews were conducted, seeking articles focused on CB published between the early 19th century and the present time. Secondary-level searches were made examining relevant publications referred to in primary-level publications, ranging back to the early 17th century. The key search words were “corneal birefringence” and “non-invasive measurements”. Results: CB was first recorded by Brewster in 1815. Orthogonally polarized rays travel at different speeds through the cornea, creating a slow axis and a fast axis. The slow axis aligns with the pattern of most corneal stromal collagen fibrils. In vivo, it is oriented along the superior temporal–inferior nasal direction at an angle of about 25° (with an approximate range of −54° to 90°) from the horizontal. CB has been reported to (i) influence the estimation of retinal nerve fiber layer thickness; (ii) be affected by corneal interventions; (iii) be altered in keratoconus; (iv) vary along the depth of the cornea; and (v) be affected by intra-ocular pressure. Conclusions: Under precisely controlled conditions, capturing the CB pattern is the first step in a non-destructive process used to model the ultra-fine structure of the individual cornea, and changes thereof, in vivo. Full article

The tissue covering the bones in synovial joints is called articular cartilage. Chondrocytes produce and maintain the extracellular matrix and, based on their shape and the orientation of the collagen fibers, articular cartilage is separated into four histological zones: superficial, middle, deep, and calcified zones. Osteoarthritis is a degenerative joint disorder in which mechanical, biochemical, and inflammatory factors contribute to the disruption of the balance between extracellular matrix synthesis and degradation. This article aims to review the literature published to date by identifying the techniques most used in immunohistochemistry and histology for the detection and grading of knee osteoarthritis in rabbit/rat models. A systematic review was carried out using databases to find publications that assessed osteoarthritis in rabbit/rat knee models using histological and immunohistochemical methods. Out of 766 initial articles, 56 met the criteria. Hematoxylin–Eosin and Safranin O demonstrated clear distinctions between healthy and osteoarthritis cartilage. Immunohistochemical findings showed decreased expression of type II collagen and increased expression of matrix metalloproteinases and caspase-3 in osteoarthritis cartilage. Although both have limitations, histology stains are useful for evaluating cartilage structure and osteoarthritis progression. On the other hand, immunohistochemistry techniques support established osteoarthritis processes, including apoptosis, metalloproteinases activity, and collagen degradation. Future research should explore additional pathways to improve osteoarthritis understanding. Full article

Background: Dental implants are widely used to replace missing teeth, particularly in aesthetically sensitive areas. The implant’s macrogeometry is crucial for ensuring primary stability and successful osseointegration. Internal conical connections and reactive surfaces on implants have shown positive outcomes in tissue and bone stability. In response, a hybrid conical dental implant was designed to address a variety of clinical scenarios. Materials and Methods: This pilot study evaluated the performance of the hybrid conical implant using histological and micro-CT analysis in a preclinical model with immediate loading. Five implants were placed in a mongrel dog, and histomorphometric and micro-CT assessments were performed after 60 days of healing. Results: Analysis showed a high degree of osseointegration, with BIC at 61.56% and BT/TV at 77%. Micro-CT confirmed these findings, with nBIC at 82.20%. Vertical measurements indicated stable crestal bone. Peri-implant tissue displayed organized supracrestal connective tissue, without signs of inflammation or bone saucerization. Polarized light microscopy revealed collagen fibers in perpendicular and oblique orientations around the abutment, suggesting mechanical integration and biological sealing despite the absence of a prosthetic crown. Conclusions: Within the limitations of this exploratory study with one animal study, the hybrid conical implant showed favorable biological and structural responses under immediate loading. These preliminary findings provide useful insights for the refinement of implant design, although further investigations in larger preclinical and clinical studies are required before clinical applicability can be confirmed. Full article