Collagen Fiber Diameter Research Articles

Restoration of the Ultrastructural Integrity of the Dermal Collagen Network by 12-Week Ingestion of Special Collagen Peptides.

This pilot study investigated the effects of a 12-week administration of a nutritional supplement containing special collagen peptides on the structural and molecular properties of the collagen fiber network in the human skin. For the assessments, the suction blister method and electron microscopical comparisons were used. Three suction blisters were generated on the inner forearm of each test subject before and after the 12-week administration of the nutritional supplement. High-resolution scanning electron microscopy (SEM) was employed to meticulously investigate the structural characteristics of the skin's collagen network, including the length and diameter of collagen fibers within the suction blister roof. Furthermore, the analysis included immunohistochemistry and fluorescence light microscopy to study hyaluronic acid within the extracellular matrix. Additional assessments encompassed changes in various epidermal parameters. Nine female participants within the age range of 43.7-61.8years (mean: 52.5 ± 5.9years) completed the study in accordance with the study protocol. Compared with baseline, the 12-week supplementation regimen led to a statistically significant average increase in the collagen fiber network size of 34.56% (p < 0.0001). Additionally, collagen fiber cross-linking and fiber length were substantially increased. The ingestion of the supplement also resulted in an 18.08% elevation in epidermal hyaluronic acid concentration (p < 0.0001). No adverse events were recorded during the study. Using an innovative approach, this study demonstrated the ability of a targeted nutritional supplement to effectively restore the ultrastructural integrity of the dermal collagen network, which is typically disrupted by the natural aging process of the skin. These findings not only corroborate existing data regarding the positive effects of oral collagen peptides on skin structure and function but also contribute to our understanding of ultrastructural morphological aspects of changes in the skin's collagen network. Supplementation can induce regeneration of the collagen fiber network in the human skin. German Clinical Trials Register, DRKS-ID DRKS00034161- Date of registration: 06.05.2024, retrospectively registered.

Changes of bone and articular cartilage in broilers with femoral head necrosis

Femoral head necrosis (FHN) in broilers is a common leg disorder in intensive poultry farming, giving rise to poor animal health and welfare. Abnormal mechanical stress in the hip joint is a risk factor for FHN, and articular cartilage is attracting increasing attention as a cushion and lubrication structure for the joint. In the present study, broilers aged 3 to 4 wk with FHN were divided into femoral head separation (FHS) and femoral head separation with growth plate lacerations (FHSL) groups, with normal broilers as control. The features of the hip joint, bone, and cartilage were assessed in FHN progression using devices including computed tomography (CT), atomic force microscope (AFM), and transmission electron microscopy (TEM). Broilers with FHN demonstrated decreased bone mechanical properties, narrow joint space, and thickened femoral head stellate structures. Notably, abnormal cartilage morphology was observed in FHN-affected broilers, characterized by increased cartilage thickness and rough cartilage surfaces. In addition, as FHN developed, cartilage surface friction and friction coefficient dramatically increased, while cartilage modulus and stiffness decreased. The ultramicro-damage occurred in chondrocytes and the extracellular matrix (ECM) of cartilage. Cell disintegration, abnormal mitochondrial accumulation, and oxidative stress damage were observed in chondrocytes. A notable decline in cartilage collagen content was observed in ECM during the initial stages of FHN, accompanied by a pronounced reduction in collagen fiber diameter and proteoglycan content as FHN progressed. Furthermore, the noticeable loosening of the collagen fiber structure and the appearance of type I collagen were noted in cartilage. In conclusion, there was a progressive decrease in bone quality and multifaceted damage of cartilage in the femoral head, which was closely linked to the severity of FHN in broilers.

Planar biaxial testing of CXL strengthening effects

The stiffening effect of corneal crosslinking (CXL) treatment, a therapeutic approach for managing the progression of keratoconus, has been primarily investigated using uniaxial tensile experiments. However, this testing technique has several drawbacks and is unable to measure the mechanical response of cornea under a multiaxial loading state. In this work, we used biaxial mechanical testing method to characterize biomechanical properties of porcine cornea before and after CXL treatment. We also investigated the influence of preconditioning on measured properties and used TEM images to determine microstructural characteristics of the extracellular matrix. The conventional method of CXL treatment was used for crosslinking the porcine cornea. The biaxial experiments were done by an ElectroForce TestBench system at a stretch ratio of 1:1 and a displacement rate of 2 mm/min with and without preconditioning. The experimental measurements showed no significant difference in the mechanical properties of porcine cornea along the nasal temporal (NT) and superior inferior (SI) direction. Furthermore, the CXL therapy significantly enhanced the mechanical properties along both directions without creating anisotropic response. The samples tested with preconditioning showed significantly stiffer response than those tested without preconditioning. The TEM images showed that the CXL therapy did not increase the diameter of collagen fibers but significantly decreased their interfibrillar spacing, consistent with the mechanical property improvement of CXL treated samples.

Effect of exogenous calcitriol on myopia development and axial length in guinea pigs with form deprivation myopia

The annual increase in myopia prevalence poses a significant economic and health challenge. Our study investigated the effect of calcitriol role in myopia by inducing the condition in guinea pigs through form deprivation for four weeks. Untargeted metabolomics methods were used to analyze the differences in metabolites in the vitreous body, and the expression of vitamin D receptor (VDR) in the retina was detected. Following form deprivation, the guinea pigs received intraperitoneal injections of calcitriol at different concentrations. We assessed myopia progression using diopter measurements and biometric analysis after four weeks. Results indicated that form deprivation led to a pronounced shift towards myopia, characterized by reduced choroidal and scleral thickness, disorganized collagen fibers, and decreased scleral collagen fiber diameter. Notably, a reduction in calcitriol expression in vitreous body, diminished vitamin D and calcitriol levels in the blood, and decreased VDR protein expression in retinal tissues were observed in myopic guinea pigs. Calcitriol administration effectively slowed myopia progression, preserved choroidal and scleral thickness, and prevented the reduction of scleral collagen fiber diameter. Our findings highlight a significant decrease in calcitriol and VDR expressions in myopic guinea pigs and demonstrate that exogenous calcitriol supplementation can halt myopia development, enhancing choroidal and scleral thickness and scleral collagen fiber diameter.

Clearing the light path: Proteoglycans and their important roles in the lens and cornea

AbstractSome of the earliest studies of glycans were performed on mammalian corneas and lenses with many of the key concepts we currently recognize as being fundamental to our understanding of basic cell biology arising from these studies. Proteoglycans and their glycosaminoglycan (GAG) side chains are essential components of the extracellular matrix (ECM) of the lens capsule. They also are present in the anterior corneal epithelial basement membrane and the posterior (Decemet's) basement membrane, and they organize collagen fiber diameters and spacing in the corneal stroma to maintain stromal clarity. Studies using genetically engineered mice and characterization of spontaneously arising mutations in genes controlling proteoglycan synthesis have generated new insight into the roles played by proteoglycans in signal transduction. We now know that proteoglycans and GAGs can regulate cell signaling and the maintenance of avascularity and immune privilege that are hallmarks of these tissues. In addition, proteoglycan‐rich matrices provide the pathways for immune cells to populate the surface of the lens as a response to corneal wounding and in a model of experimental autoimmune uveitis. Here we describe what is known about proteoglycans and GAGs in the cornea and lens. This knowledge has begun to provide promising leads into new proteoglycan‐based treatments aimed at restoring and maintaining homeostasis in the cornea. Future studies are needed to determine how these new drugs impact the recruitment of immune cells to the lens for functions in restoring/maintaining homeostasis in the eye.

Engineering Anisotropic Cell Models: Development of Collagen Hydrogel Scaffolds with Magneto‐Responsive PEG Microgels for Tissue Engineering Applications

AbstractMimicking tissue‐oriented organization in vitro has been extensively studied in recent years, using both natural and synthetic materials in combination with external magnetic fields to establish anisotropic conditions. Here, a new combination between magneto‐responsive anisometric PEG microgels and collagen hydrogels is explored to establish anisotropic in vitro models. Different sizes of PEG microgels are tested to assess the impact of both width and aspect ratio on the formation and alignment of collagen hydrogels. Results show that the key properties of collagen hydrogels, regarding fibrillogenesis, rheological properties, and fiber diameter are kept consistent upon the combination with PEG microgels. Furthermore, partial collagen fiber alignment is observed when larger (width 10 µm) PEG microgels are employed and magnetically aligned. In vitro studies show cell alignment within the anisotropic collagen hydrogels from the first day in culture. Interestingly, PEG microgels with higher width and length tend to induce less hydrogel contraction even after 7 days in culture. The results demonstrate the ability to establish a 3D unidirectional collagen hydrogel by magnetically aligning anisometric microgels during the gelation process, which can be promising for different tissue engineering applications.

Early delivery of human umbilical cord mesenchymal stem cells improves healing in a rat model of Achilles tendinopathy.

Objective: This study aimed to explore the efficacy and optimal delivery time of human umbilical cord mesenchymal stem cells (hUC-MSCs) in treating collagenase-induced Achilles tendinopathy. Methods: Achilles tendinopathy in rats at early or advanced stages was induced by injecting collagenase I into bilateral Achilles tendons. A total of28 injured rats were injected with a hUC-MSCsolution or normal saline into bilateral tendons twice andsampled after 4weeks for histological staining, gene expression analysis, transmission electron microscope assayand biomechanical testing analysis. Results: The results revealed better histological performance and a larger collagen fiber diameter in theMSC group. mRNA expressionof TNF-α, IL-1βand MMP-3 was lower after MSC transplantation. Early MSC delivery promoted collagen I and TIMP-3 synthesis, and strengthened tendon toughness. Conclusion: hUC-MSCs demonstrated atherapeutic effect in treating collagenase-induced Achilles tendinopathy, particularly in the early stage of tendinopathy.

Cervical Collagen Network Porosity Assessed by SHG Endomicroscopy Distinguishes Preterm and Normal Pregnancy - a Pilot Study.

Preterm birth (PTB) remains a pressing global health concern associated with premature cervical ripening and weakened cervical mechanical strength. Second harmonic generation (SHG) microscopy has proved instrumental in tracking progressive changes in cervical collagen morphology during pregnancy. To translate this imaging modality into clinical practice, we have developed a flexible SHG endomicroscope for label-free visualization of cervical collagen architecture. This study aims to assess the feasibility of our SHG endomicroscope for non-invasive differentiation of normal and PTB mouse models, with the ultimate goal of enabling early diagnosis and risk assessment of PTB in vivo. in this pilot investigation, we conducted endomicroscopic SHG imaging on frozen cervical tissue sections and intact cervices resected from both normal pregnant mice and mifepristone-induced PTB mouse models, and then analyzed the acquired images to identify collagen morphology characteristics associated with abnormal cervical collagen remodeling. quantitative image analysis revealed significantly altered collage spatial distribution, larger collagen fiber diameter and pore size, along with reduced pore numbers in SHG endomicroscopy images from PTB mouse models compared to normal pregnant mice. Similar trends were consistent across SHG endomicroscopy images of subepithelial collagen fibers acquired directly from intact cervices. overall, the experiment results underscore the potential of SHG endomicroscopy, coupled with quantitative image analysis, for clinically evaluating cervical collagen remodeling and PTB risk.

Effect of collagen denaturation degree on mechanical properties and biological activity of nanofibrous scaffolds.

Further progress in regenerative medicine and bioengineering highly depends on the development of 3D polymeric scaffolds with active biological properties. The most attention is paid to natural extracellular matrix components, primarily collagen. Herein, nonwoven nanofiber materials with various degrees of collagen denaturation and fiber diameters 250-500 nm were produced by electrospinning, stabilized by genipin, and characterized in detail. Collagen denaturation has been confirmed using DSC and FTIR analysis. The comparative study of collagen and gelatin nonwoven materials (NWM) revealed only minor differences in their biocompatibility with skin fibroblasts and keratinocytes in vitro. In long-term subcutaneous implantation study, the inflammation was less evident on collagen than on gelatin NWM. Remarkably, the pronounced calcification was revealed in the collagen NWM only. The results obtained can be useful in terms of improving the electrospinning technology of collagen from aqueous solutions, as well as emphasize the importance of long-term study to ensure proper implementation of the material, taking into account the ability of collagen to provoke calcification.

Chondroitinase ABC Treatment Improves the Organization and Mechanics of 3D Bioprinted Meniscal Tissue.

The meniscus is a fibrocartilage tissue that is integral to the correct functioning of the knee joint. The tissue possesses a unique collagen fiber architecture that is integral to its biomechanical functionality. In particular, a network of circumferentially aligned collagen fibers function to bear the high tensile forces generated in the tissue during normal daily activities. The limited regenerative capacity of the meniscus has motivated increased interest in meniscus tissue engineering; however, the in vitro generation of structurally organized meniscal grafts with a collagen architecture mimetic of the native meniscus remains a significant challenge. Here we used melt electrowriting (MEW) to produce scaffolds with defined pore architectures to impose physical boundaries upon cell growth and extracellular matrix production. This enabled the bioprinting of anisotropic tissues with collagen fibers preferentially oriented parallel to the long axis of the scaffold pores. Furthermore, temporally removing glycosaminoglycans (sGAGs) during the early stages of in vitro tissue development using chondroitinase ABC (cABC) was found to positively impact collagen network maturation. Specially we found that temporal depletion of sGAGs is associated with an increase in collagen fiber diameter without any detrimental effect on the development of a meniscal tissue phenotype or subsequent extracellular matrix production. Moreover, temporal cABC treatment supported the development of engineered tissues with superior tensile mechanical properties compared to empty MEW scaffolds. These findings demonstrate the benefit of temporal enzymatic treatments when engineering structurally anisotropic tissues using emerging biofabrication technologies such as MEW and inkjet bioprinting.

A mouse model of brittle cornea syndrome type 2

AbstractPurpose: Brittle Cornea Syndrome (BCS) is a rare disease that affects 1 in 1 000 000 people world wide. With a reduction in cornea thickness and therefore strength sufferers have an increase in loss of vision through injury. Our lab has previously published the first mouse model of BCS Type 1(1) and are currently characterizing a novel model of BCS type 2 in order to elucidate the underlying mechanisms causing this disease.Methods: Mice carrying a 7 bp deletion which causes a frameshift and premature stop codon within the causative gene Prdm5 have been extensively phenotyped using Optical Coherence Tomography (OCT), Transmission Electron Microscopy (TEM) and Histology.Results: These mice show a reduced central corneal thickness by OCT from as early as 1 month of age. TEM and histological analysis indicates that this reduction in thickness may be due to the dysregulation of collagen assembly – as stromal collagen fibre diameter is significantly reduced.Conclusions: The structure of the stroma is crucial to corneal function: mechanical strength and transparency are achieved by the intricate arrangement of collagen fibrils, synthesized by keratocytes. Although it is known that the corneal stroma has a unique composition in which the ratio of Type I to Type V collagen is very different to anywhere else in the body, it remains unclear how the synthesis and maintenance of this specialized extracellular matrix by keratocytes is controlled. Characterization of the nature and extent of developmental defects in the cornea of this mouse model will be important to devise future therapeutic interventions.Reference1. Stanton, C. M., Findlay, A. S., Drake, C., Mustafa, M. Z., Gautier, P., McKie, L., Jackson, I. J., &amp; Vitart, V. (2021). A mouse model of brittle cornea syndrome caused by mutation in Zfp469. Disease models &amp; mechanisms, 14(9), dmm049175. https://doi.org/10.1242/dmm.049175

Differences in Collagen Fiber Diameter and Waviness between Healthy and Aneurysmal Abdominal Aortas.

Collagen plays a key role in the strength of aortic walls, so studying micro-structural changes during disease development is critical to better understand collagen reorganization. Second-harmonic generation microscopy is used to obtain images of human aortic collagen in both healthy and diseased states. Methods are being developed in order to efficiently determine the waviness, that is, tortuosity and amplitude, as well as the diameter, orientation, and dispersion of collagen fibers, and bundles in healthy and aneurysmal tissues. The results show layer-specific differences in the collagen of healthy tissues, which decrease in samples of aneurysmal aortic walls. In healthy tissues, the thick collagen bundles of the adventitia are characterized by greater waviness, both in the tortuosity and in the amplitude, compared to the relatively thin and straighter collagen fibers of the media. In contrast, most aneurysmal tissues tend to have a more uniform structure of the aortic wall with no significant difference in collagen diameter between the luminal and abluminal layers. An increase in collagen tortuosity compared to the healthy media is also observed in the aneurysmal luminal layer. The data set provided can help improve related material and multiscale models of aortic walls and aneurysm formation.

Species variation in the cartilaginous endplate of the lumbar intervertebral disc.

BackgroundsCartilaginous endplate (CEP) plays an essential role in intervertebral disc (IVD) health and disease. The aim was to compare the CEP structure of lumbar IVD and to reveal the detailed pattern of integration between the CEP and bony endplate (BEP) from different species.MethodsA total of 34 IVDs (5 human, 5 goat, 8 pig, 8 rabbit, and 8 rat IVDs) were collected, fixed and midsagittally cut; in each IVD, one‐half was used for histological staining to observe the CEP morphology, and the other half was used for scanning electron microscopy (SEM) analysis to measure the diameters and distributions of collagen fibers in the central and peripheral CEP areas and to observe the pattern of CEP‐BEP integration from different species.ResultsThe human, pig, goat, and rabbit IVDs had the typical BEP‐CEP structure, but the rat CEP was directly connected with the growth plate. Human CEP was the thickest (896.95 ± 87.71 μm) among these species, followed by pig, goat, rat, and rabbit CEPs. Additionally, the mean cellular density of the rabbit CEP was the highest, which was 930 ± 202 per mm2, followed by the rat, goat, pig, and human CEPs. In all the species, the collagen fiber diameter in the peripheral area was much bigger than that in the central area. The collagen fiber diameters of CEP from the human, pig, goat, and rat were distributed between 35 nm and 65 nm. The BEP and CEP were connected by the collagen from the CEP, aggregating into bundles or cross links with each other to form a network, and anchored to BEP.ConclusionsSignificant differences in the thickness, cellular density, and collagen characterization of CEPs from different species were demonstrated; the integration of BEP‐CEP in humans, pigs, goats, and rabbits was mainly achieved by the collagen bundles anchoring system, while the typical BEP‐CEP interface did not exist in rats.

Effects of Chemical Sterilization and Gamma Irradiation on the Biochemical and Biomechanical Properties of Human Tendon Allografts In Vitro Study.

ObjectivePre‐implantation sterilization procedures for tendons are important measures to reduce the risk of disease transmission, however these procedures may compromise tendon microarchitecture and biomechanical properties to varying degrees. We explore the effects of different sterilization procedures on the micro‐histology, biomechanical strength and biochemical properties of human tendon allografts in vitro study.MethodsThe tendon allografts were harvested from cadaveric donors after the donors were serologically screened by antibody or nucleic acid testing of infectious agents. All samples were divided into five groups, which were fresh‐frozen group (control group), 15 kGy gamma irradiation group, 25 kGy gamma irradiation group, 70% ethanol group, and peracetic acid‐ethanol group. Each group included 10 tendons for testing. Histological staining and transmission electron microscopy were applied to observe the internal structure and arrangement of tendon collagen fibers, while the machine learning classifier was trained to distinguish the darker cross‐sections of collagen fibers and brighter backgrounds of the electron micrograph to detect the distribution of diameters of tendon collagen fibers. The viscoelasticity, mechanical properties and material properties of tendon allografts were examined to detect the influence of different intervention factors on the biomechanical properties of tendons.ResultsHistological staining and transmission electron microscopy showed that the structure of fresh‐frozen tendons was similar to the structures of other experimental groups, and no obvious fiber disorder or delamination was observed. In the uniaxial cyclic test, the cyclic creep of 25 kGy irradiation group (1.5%) and peracetic acid‐ethanol group (1.5%) were significantly lower than that of the control group (3.6%, F = 1.52, P = 0.039) while in the load‐to‐failure test, the maximum elongation and maximum strain of the peracetic acid‐ethanol group were significantly higher than those of the control group (F = 4.60, P = 0.010), and there was no significant difference in other biomechanical indicators. According to the experimental results of denatured collagen, it could be seen that no matter which disinfection procedure was used, the denaturation of the tendon sample would be promoted (F = 1.97, P = 0.186), and high‐dose irradiation seemed to cause more damage to collagen fibers than the other two disinfection procedures (296.2 vs 171.1 vs 212.9 μg/g).ConclusionBiomechanical experiments and collagen denaturation tests showed that 15 kGy gamma irradiation and 70% ethanol can preserve the biomechanical strength and biochemical properties of tendons to the greatest extent, and these two sterilization methods are worthy of further promotion.

Poster 249: Evaluation of ACL Reconstruction Using a Bone-ACL-Bone Complex Allograft in a Rabbit Model

Objectives:Anatomic anterior cruciate ligament (ACL) reconstruction is defined as the restoration of the native insertion sites, tissue dimensions, and collagen orientation. However, the microstructure and composition of standard tendon grafts used for ACL reconstruction differs from ligament. A bone-ACL-bone allograft (B-ACL-B) could represent a potential solution to ACL reconstruction, and thus the purpose of this study is to evaluate incorporation of a B-ACL-B graft used for ACL reconstruction in a rabbit model.Methods:Our study was approved by the Institutional Animal Care and Use Committee. A total of 71 New Zealand white rabbits were used, with 30 donor rabbits for harvesting bilateral B-ACL-B allografts, and recipient rabbits undergoing unilateral ACL resection followed by reconstruction with B-ACL-B allograft. Animals were euthanized for biomechanical testing (n = 14) at 4 and 8 weeks after surgery, and for micro–computed tomography (μCT), multi-photon microscopy, transmission electron microscopy (n=12), and histological analysis (n= 15) at 2, 4 and 8 weeks after surgery. Multi-photon microscopy analysis used Fast Fourier Transform in imageJ to calculate the proportion of fibers that deviated from orthogonal as a measure of collagen alignment and organization. One-way analysis of variance (ANOVA) with the post-hoc Tukey test was used to analyze differences among groups.Results:Gross inspection and radiographs confirmed intact ACL allograft in the proper anatomic position without evidence of complication. There was no significant difference between 4 and 8 weeks in mean failure force (4 weeks: 18.21 ± 8.74 N, 8 weeks: 21.75 ± 4.21 N, p=0.39) or stiffness (4 weeks: 8.08 ± 3.36 N/mm, 8 weeks: 10.88 ± 2.88 N/mm, p=0.15) for the B-ACL-B allografts. Progressive healing occurred between the bone block and the bone tunnel as demonstrated by a gradual increase in average bone-volume fraction (BVF) and total mineral density (TMD) between the bone block and tunnel wall in both femoral and tibial tunnels at 4 and 8 weeks. There was a significant decrease in TMD of both femoral and tibial bone blocks compared to day 0, indicating remodeling of the bone block (both p<0.001). Histological analysis showed bone block resorption at 2 weeks, followed by gradual new bone formation at the bone block-tunnel interface at 4 and 8 weeks. There was a gradual decrease in cellularity at the interface between bone block and tunnel wall (p=0.014), and increase in cellularity along the superficial aspect of the intra-articular ligament (p =0.008). Multi-photon microscopy demonstrated that the native control ACL demonstrated a mean % deviation from orthogonal value of 9.03± 1.81, 13.5±3.83 and 9.24±3.42 for femoral enthesis, mid-ACL, and tibial enthesis, respectively. The two-week specimens had a mean value of 6.50±3.34 (femoral enthesis), 10.4±1.73 (mid-ACL) and 10.97±3.666 (tibial enthesis) with none being statistically significantly different from control. The four-week samples had a mean of 9.10±1.87 for femoral enthesis, 8.39±3.28 for mid-ACL and 8.36±4.65 for tibial enthesis. Lastly, the 8-week specimens demonstrated that the mean deviation for the femoral enthesis was 7.26±1.67, mid-ACL was 7.89±1.58, and tibial enthesis was 10.8±2.55. The values for the mid-ACL was significantly less than controls at 4 and 8 weeks (p=0.0126 and 0.0063, respectively), suggesting maintenance of collagen fibril organization in the grafts. EM analysis of collagen fiber diameter demonstrated significantly lower average fibril diameter at all post-operative time points compared to age-matched native control ACLs (p<0.001).Conclusions:In conclusion, our rabbit model of B-ACL-B allograft ACL reconstruction demonstrates restoration of the normal macroscopic anatomy of the ACL, with progressive graft incorporation and remodeling. The B-ACL-B allograft, rather than a tendon graft, may provide the closest possible structural and biomechanical match to the native ACL, resulting in improved functional outcomes and may serve as a future option for ACL reconstruction. The results of this study provide important preliminary information to allow further study of this approach to ACL reconstruction and may serve as a baseline for future investigations.NoneFigure 1.Illustration of reconstruction plan for the B-Acl-B allograftFigure 2.Histolgy of interface and ligament.Figure 3.Results of TEM and MPM Analysis.

Multimodal Structural Analysis of the Human Aorta: From Valve to Bifurcation

The aims of the present study were to assess the relative proportion of collagen and elastin in the arterial wall and to evaluate the collagen microstructure from the aortic root to the external iliac artery. Arterial wall tissue samples sampled during post-mortem examination from 16 sites in 14 individuals without aneurysm disease were fixed and stained for collagen and elastin. Stained sections were imaged and analysed to calculate collagen and elastin content as a percentage of overall tissue area. Scanning electron microscopy was used to quantify the collagen microstructure at six specific arterial regions. From the aortic root to the level of the suprarenal aorta, the percentages (area fractions) of collagen (ascending, descending, and suprarenal aorta respectively with 95% confidence interval [CI] 37.5%, 31.7 – 43.2; 38.9%, 33.1 – 44.7; 44.8%, 37.4 – 52.1) and elastin (43.0%, 37.3 – 48.8; 40.3%, 34.8 – 46.1; 32.4%, 25.2 – 39.6) in the aortic wall were similar. From the suprarenal aorta to the internal iliac arteries, the percentage of collagen increased (abdominal aorta, common and internal iliac arteries and external iliac artery respectively with 95% CI 50.6%, 42.7 – 58.7; 51.2%, 45.5 – 56.9; 49.2%, 42.0 – 56.4) reaching a double percentage for elastin (23.6%, 15.7 – 31.6; 20.8%, 15.1 – 26.5; 22.2%, 14.9 – 29.5). Mean collagen fibre diameter (MFD) and average segment length (ASL) were significantly larger in the external iliac artery (MFD 6.03, 95% CI 5.95 – 6.11; ASL 22.21, 95% CI 20.80 – 23.61) than in the ascending aorta (MFD 5.81, 5.72 – 5.89; ASL 19.47, 18.07 – 20.88) and the abdominal aorta (MFD 5.92, 5.84 – 6.00; ASL 21.10, 19.69 – 22.50). In subjects lacking aneurysmal disease, the aorta and iliac arteries are not structurally uniform along their length. There is an increase in collagen percentage and decrease in elastin percentage progressing distally along the aorta. Mean collagen fibre diameter and average segment length are larger in the external iliac artery, compared with the ascending and the abdominal aorta.

The histopathological findings in excised upper eyelids of patients with dermatochalasis following collagen cross-linking treatment.

To evaluate the histopathological effects of collagen cross-linking (CCL) on excised skin samples of patients undergoing upper eyelid blepharoplasty due to dermatochalasis. This study examined 74 excised eyelid skin samples from 37 dermatochalasis patients. Following an upper eyelid blepharoplasty, CCL with hypotonic riboflavin (0.1%) was applied. Both treated (right eyelid, CCL group) and untreated eyelid specimen (left eyelid, non-CCL group) sections were stained with hematoxylin-eosin and Masson's trichrome. The sections were evaluated for the following parameters: the collagen status (parallel, oblique, and perpendicular), the distance between collagen fibers, the diameter of collagen fibers, and the length of collagen fibers. There were no statistically significant differences in the collagen status, the distance between collagen fibers, the diameter of collagen fibers, and the length of collagen fibers between the CCL and non-CCL groups (p > 0.05 for all). Although the lack of statistically significant differences, the structure of the treated eyelid collagen fibers was more parallel in 48% of the participants than in the untreated ones. For male patients, a statistically significant shorter distance between collagen fibers was observed in the CCL group (8.05 ± 2.04µm) compared to the non-CCL group (9.97 ± 2.33µm) (p = 0.042). In this study, more parallel collagen structures and tightly packed collagen fibers were detected in eyelid samples following CCL treatment. The authors note that the results of this study may be promising for further research, so the effect of CCL therapy on the eyelid may be an interesting subject for the treatment of non-severe or surgically inadequately corrected dermatochalasis.

Multimodal Structural Analysis of the Human Aorta: From Valve to Bifurcation

The aims of the present study were to assess the relative proportion of collagen and elastin in the arterial wall and to evaluate the collagen microstructure from the aortic root to the external iliac artery. Arterial wall tissue samples sampled during post-mortem examination from 16 sites in 14 individuals without aneurysm disease were fixed and stained for collagen and elastin. Stained sections were imaged and analysed to calculate collagen and elastin content as a percentage of overall tissue area. Scanning electron microscopy was used to quantify the collagen microstructure at six specific arterial regions. From the aortic root to the level of the suprarenal aorta, the percentages (area fractions) of collagen (ascending, descending, and suprarenal aorta respectively with 95% confidence interval [CI] 37.5%, 31.7 - 43.2; 38.9%, 33.1 - 44.7; 44.8%, 37.4 - 52.1) and elastin (43.0%, 37.3 - 48.8; 40.3%, 34.8 - 46.1; 32.4%, 25.2 - 39.6) in the aortic wall were similar. From the suprarenal aorta to the internal iliac arteries, the percentage of collagen increased (abdominal aorta, common and internal iliac arteries and external iliac artery respectively with 95% CI 50.6%, 42.7 - 58.7; 51.2%, 45.5 - 56.9; 49.2%, 42.0 - 56.4) reaching a double percentage for elastin (23.6%, 15.7 - 31.6; 20.8%, 15.1 - 26.5; 22.2%, 14.9 - 29.5). Mean collagen fibre diameter (MFD) and average segment length (ASL) were significantly larger in the external iliac artery (MFD 6.03, 95% CI 5.95 - 6.11; ASL 22.21, 95% CI 20.80 - 23.61) than in the ascending aorta (MFD 5.81, 5.72 - 5.89; ASL 19.47, 18.07 - 20.88) and the abdominal aorta (MFD 5.92, 5.84 - 6.00; ASL 21.10, 19.69 - 22.50). In subjects lacking aneurysmal disease, the aorta and iliac arteries are not structurally uniform along their length. There is an increase in collagen percentage and decrease in elastin percentage progressing distally along the aorta. Mean collagen fibre diameter and average segment length are larger in the external iliac artery, compared with the ascending and the abdominal aorta.

Comparison of the efficacies of polycaprolactone filler and lidocaine-added filler on neocollagenesis in a rat model.

Polycaprolactone (PCL) is a semi-permanent filler stimulating neocollagenesis. Lidocaine is frequently used to reduce the pain and, however, may have negative effects on collagen. It was aimed to compare the histological changes on rat skin and efficacies of PCL filler and lidocaine addition. In this study, results of PCL and PCL+Lidocaine application on rat skin were compared using hematoxylin-eosin (H&E) staining, Masson's trichrome (MT) staining, and electron microscope (EM). A total of 30 adult female rats were divided into three groups: the control group, the PCL group, and the PCL+Lidocaine group. The tissue samples taken at months 2 and 4 were examined using H&E, MT, and EM. At month 2, dermis thickness, fibroblast count, and collagen fiber diameter increased similarly in the PCL and PCL+Lidocaine groups. Collagen fiber diameter was significantly higher in the PCL group than in the PCL+Lidocaine (p:0.016) and control groups (p:0.009). At month 4, no significant difference was detected between the PCL and PCL+Lidocaine groups in terms of fibroblast count, collagen fiber count, and collagen fiber diameter; dermis thickness was lower in the PCL+Lidocaine group at month 4 (p<0.46). Dermis thickness, fibroblast count, collagen fiber count, and collagen fiber diameter were found to be significantly lower than in the PCL and PCL+Lidocaine groups. Our study showed that lidocaine addition to PCL filler does not affect the efficacy of the filler and PCL filler stimulates neocollagenesis.

Adipose-Derived Stem Cell Sheets Improve Early Biomechanical Graft Strength in Rabbits After Anterior Cruciate Ligament Reconstruction

Background: Although various reconstruction techniques are available for anterior cruciate ligament (ACL) injuries, a long recovery time is required before patients return to sports activities, as the reconstructed ACL requires time to regain strength. To date, several studies have reported use of mesenchymal stem cells in orthopaedic surgery; however, no studies have used adipose-derived stem cell (ADSC) sheets in ACL reconstruction (ACLR). Hypothesis: ADSC sheet transplantation can improve biomechanical strength of the autograft used in ACLR. Study Design: Controlled laboratory study. Methods: A total of 68 healthy Japanese white rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into a control group (no sheet; n = 34) and a sheet group (ADSC sheet; n = 34). At 2, 4, 8, 16, and 24 weeks after surgery, rabbits in each group were sacrificed to evaluate tendon-bone healing using histological staining, micro–computed tomography, and biomechanical testing. At 24 weeks, scanning transmission electron microscopy of the graft midsubstance was performed. Results: The ultimate failure load for the control and sheet groups, respectively, was as follows: 17.2 ± 5.5 versus 37.3 ± 10.3 (P = .01) at 2 weeks, 28.6 ± 1.9 versus 47.4 ± 10.4 (P = .003) at 4 weeks, 53.0 ± 14.3 versus 48.1 ± 9.3 (P = .59) at 8 weeks, 66.2 ± 9.3 versus 95.2 ± 43.1 (P = .24) at 16 weeks, and 66.7 ± 27.3 versus 85.3 ± 29.5 (P = .39) at 24 weeks. The histological score was also significantly higher in the sheet group compared with the control group at early stages up to 8 weeks. On micro–computed tomography, relative to the control group, the bone tunnel area was significantly narrower in the sheet group at 4 weeks, and the bone volume/tissue volume of the tendon-bone interface was significantly greater at 24 weeks. Scanning transmission electron microscopy at 24 weeks indicated that the mean collagen fiber diameter in the midsubstance was significantly greater, as was the occupation ratio of collagen fibers per field of view, in the sheet group. Conclusion: ADSC sheets improved biomechanical strength, prevented bone tunnel enlargement, and promoted tendon-bone interface healing and graft midsubstance healing in an in vivo rabbit model. Clinical Relevance: ADSC sheets may be useful for early tendon-bone healing and graft maturation in ACLR.