Fractal analysis of extra-embryonic vessels of chick embryos under the effect of glucosamine and chondroitin sulfates

A new fractal index to classify forest fragmentation and disorder

Context

Forest loss and fragmentation pose extreme threats to biodiversity. Their efficient characterization from remotely sensed data therefore has strong practical implications. Data are often separately analyzed for spatial fragmentation and disorder, but no existing metric simultaneously quantifies both the shape and arrangement of fragments.

Objectives

We present a fractal fragmentation and disorder index (FFDI), which advances a previously developed fractal index by merging it with the Rényi information dimension. The FFDI is designed to work across spatial scales, and to efficiently report both the fragmentation of images and their spatial disorder.

Methods

We validate the FFDI with 12,600 synthetic hierarchically structured random map (HRM) multiscale images, as well as several other categories of fractal and non-fractal test images (4880 images). We then apply the FFDI to satellite imagery of forest cover for 10 distinct regions of the Romanian Carpathian Mountains from 2000–2021.

Results

The FFDI outperformed its two individual components (fractal fragmentation index and Rényi information dimension) in resolving spatial patterns of disorder and fragmentation when tested on HRM classes and other image types. The FFDI thus offers a clear advantage when compared to the individual use of fractal fragmentation index and the Information Dimension, and provided good classification performance in an application to real data.

Conclusions

This work improves on previous characterizations of landscape patterns. With the FFDI, scientists will be able to better monitor and understand forest fragmentation from satellite imagery. The FFDI may also find wider applicability in biology wherever image analysis is used.

Visualizing the spatiotemporal pattern of yolk sac membrane vascular network by enhanced local fractal analysis

OBJECTIVE

To establish methods for providing a comprehensive and detailed description of the spatial distribution of the vascular networks, and to reveal the spatiotemporal pattern of the yolk sac membrane vascular network during the angiogenic procedure.

METHODS

Addressing the limitations in the conventional local fractal analysis, an improved approach, named scanning average local fractal dimension, was proposed. This method was conducted on 6 high-resolution vascular images of the yolk sac membrane for 3 eggs at two stages (E3 and E4) to characterize the spatial distribution of the complexity of the vascular network.

RESULTS

With the proposed method, the spatial distribution of the complexity of the yolk sac membrane vascular network was visualized. From E3 to E4, the local fractal dimension increased in 3 eggs, 1.80 ± 0.02 vs. 1.85 ± 0.02, 1.72 ± 0.03 vs. 1.83 ± 0.02, and 1.77 ± 0.03 vs. 1.82 ± 0.02, respectively. The mean local fractal dimension in the most distal area from the embryo proper was the lowest at E3 while the highest at E4. At E3, the most peaks of the local fractal dimension were located in the vein territories and shifted to artery territories at E4.

CONCLUSIONS

The spatial distribution of the complexity of the yolk sac membrane vascular network exhibited diverse patterns at different stages. In addition from E3 to E4, the increment of complexity at the intersection areas between arteries and sinus terminalis was with the most advance. This is consistent with the physiologic evidence. The present work provides a potential approach for investigating the spatiotemporal pattern of the angiogenic process.

Functional Hydrogels with Chondroitin Sulfate Release Properties Regulate the Angiogenesis Behaviors of Endothelial Cells

Functional hydrogels with properties that mimic the structure of extracellular matrix (ECM) and regulate cell behaviors have drawn much attention in biomedical applications. Herein, gelatin-based hydrogels were designed and loaded with chondroitin sulfate (CS) to endow biological regulation on the angiogenesis behaviors of endothelial cells (ECs). Manufactured hydrogels containing various amounts of CS were characterized via methods including mechanical tests, cytocompatibility, hemolysis, and angiogenesis assays. The results showed that the prepared hydrogels exhibited excellent mechanical stability, cytocompatibility, and hemocompatibility. Additionally, the angiogenesis behaviors of ECs were obviously promoted. However, excessive loading of CS would weaken the effect due to a higher proportion of occupation on the cell membrane. In conclusion, this investigation highlights the great potential of these hydrogels in treating ischemic diseases and accelerating tissue regeneration in terms of regulating the angiogenesis process via CS release.

Morphological characterization of Etv2 vascular explants using fractal analysis and atomic force microscopy

The rapid engraftment of vascular networks is critical for functional incorporation of tissue explants. However, existing methods for inducing angiogenesis utilize approaches that yield vasculature with poor temporal stability or inadequate mechanical integrity, which reduce their robustness in vivo. The transcription factor Ets variant 2 (Etv2) specifies embryonic hematopoietic and vascular endothelial cell (EC) development, and is transiently reactivated during postnatal vascular regeneration and tumor angiogenesis. This study investigates the role for Etv2 upregulation in forming stable vascular beds both in vitro and in vivo. Control and Etv2⁺ prototypical fetal-derived human umbilical vein ECs (HUVECs) and adult ECs were angiogenically grown into vascular beds. These vessel beds were characterized using fractal dimension and lacunarity, to quantify their branching complexity and space-filling homogeneity, respectively. Atomic force microscopy (AFM) was used to explore whether greater complexity and homogeneity lead to more mechanically stable vessels. Additionally, markers of EC integrity were used to probe for mechanistic clues. Etv2⁺ HUVECs exhibit greater branching, vessel density, and structural homogeneity, and decreased stiffness in vitro and in vivo, indicating a greater propensity for stable vessel formation. When co-cultured with colon tumor organoid tissue, Etv2⁺ HUVECs had decreased fractal dimension and lacunarity compared to Etv2⁺ HUVECs cultured alone, indicating that vessel density and homogeneity of vessel spacing increased due to the presence of Etv2. This study sets forth the novel concept that fractal dimension, lacunarity, and AFM are as informative as conventional angiogenic measurements, including vessel branching and density, to assess vascular perfusion and stability.

Fractal Analysis of the Distribution and Morphology of Pores in Dinosaur Eggshells Collected in Mexico: Implications to Understand the Biomineralization of Calcium Carbonate

In this work, we present an investigation of the surface area and roughness of different dinosaur eggshells of 70 million years old using fractal dimension analysis obtained from atomic force microscopy (AFM) and scanning electron microscopy (SEM) information. We also conduct qualitative analyses on the external and inner surfaces of eggshells, which are mainly composed of calcium carbonate. The morphological characteristics of both surfaces can be revealed by both SEM and AFM techniques. It is observed that the inner surface of the eggshell has greater roughness that increases the surface area due to the vaster number of pores compared to the external face, making, therefore, the fractal dimension also greater. The aim of this contribution is to identify the morphology of the pores, as well as the external and inner surfaces of the eggshells, since the morphology is very similar on both surfaces and will otherwise be difficult to determine with the naked eye by SEM and AFM. In addition, the sole AFM analysis is very complicated for these types of samples due to the intrinsic roughness. However, it needs additional methods or strategies to complete this purpose. This contribution used the fractal dimension to show the same behavior obtained in both SEM and AFM techniques, indicating the fractal nature of the structures.

Teucrium polium Alters the Vascular Branching Pattern and VEGF-A Expression in the Chick Extra-Embryonic Membrane Model

Background: The Teucrium polium is used in traditional medicine for the treatment of various diseases, including inflammations, rheumatism, diabetes, and ulcers. While this herb and its aqueous extract have been consumed in Iran for hypoglycemia treatment, medicine has proved several side effects such as hepatitis, vomiting, changes in the kidney functions, and allergic responses. Also, using this herb is not safe during pregnancy or lactation. The chick embryo is a live animal model applicable for assessing the pathological property of herbs. In this regard, some details of the embryonic vascular toxicity of the Teucrium polium were evaluated via a chick embryo model. Objectives: The current study assessed vessels' alteration in the chick's extra embryonic membrane following Teucrium polium treatment. Change in molecular cues involved in early embryonic angiogenesis has also been investigated. Methods: The eggs of the chicken were divided into three equal treatment groups; as follow: first group one: considered as a sham, next groups: herbal extract that eggs injected with T. polium extract of 3 (150 µg/50 µL) or 6 (300 µg/50 µL) mg/kg, respectively. Results: The anti-angiogenic effect of the herb extract in which vessel area, total vessel length, and vascular branching decreased, whereas lacunarity increased in a dose-dependent manner. VEGF-A expression was also down-regulated in herb-exposed extra-embryonic membranes. Concerns regarding the side effects of T. polium during pregnancy were confirmed. Conclusions: We conclude that changes in early vascular expansion and gene expression might finally lead to developmental defects in embryos following consumption of T. polium. Thus, this herb's consumption should be decreased during embryonic development, and clinicians should limit the herb prescription in pregnant women, particularly at dosages > 3 mg/kg.

Vascular alteration in relation to fosfomycine: In silico and in vivo investigations using a chick embryo model

Fosfomycin residues are found in the egg following administration in the layer hen. In this regard, some aspects of embryo-toxicity of fosfomycin have been documented previously. The exact mechanism by which fosfomycin causes embryo-toxicity is not clearly understood. We hypothesis that fosfomycin may alter vasculature as well as normal expression of genes, which are associated with vascular development. Therefore, the present study aimed to address these issues through in silico and in vivo investigations. At first, embryo-toxicity and anti-angiogenic effects of fosfomycin were tested using computerized programs. After that, fertile chicken eggs were treated with fosfomycin and chorioallantoic membrane vasculature was assessed through morphometric, molecular and histopathological assays. The results showed that fosfomycin not only interacted with VEGF-A protein and promoter, but also altered embryonic vasculature and decreased expression level of VEGF-A. Reticulin staining of treated group was also confirmed decreased vasculature. The minor groove of DNA was the preferential binding site for fosfomycin with its selective binding to GC-rich sequences. We suggested that the affinity of fosfomycin for VEGF-A protein and promoter as well as alteration of the angiogenic signaling pathway may cause vascular damage during embryonic growth. Hence, veterinarians should be aware of such effects and limit the use of this drug during the developmental stages of the embryo, particularly in breeder farms. Considering the anti-angiogenic activity and sequence selectivity of fosfomycin, a major advantage that seems to be very promising is the fact that it is possible to achieve a sequence-selective binding drug for cancer.

Antibacterial Activity and Cytotoxicity of Immobilized Glucosamine/Chondroitin Sulfate on Polylactic Acid Films

Polylactic acid (PLA) is one of the most produced polymeric materials, due to its exceptional chemical and mechanical properties. Some of them, such as biodegradability and biocompatibility, make them attractive for biomedical applications. Conversely, the major drawback of PLA in the biomedical field is their vulnerability to bacterial contamination. This study focuses on the immobilization of saccharides onto the PLA surface by a multistep approach, with the aim of providing antibacterial features and evaluting the synergistic effect of these saccharides. In this approach, after poly (acrylic acid) (PAA) brushes attached non-covalently to the PLA surface via plasma post-irradiation grafting technique, immobilization of glucosamine (GlcN) and chondroitin sulfate (ChS) to the PAA brushes was carried out. To understand the changes in surface properties, such as chemical composition, surface topography and hydrophilicity, the untreated and treated PLA films were analyzed using various characterization techniques (contact angle, scanning electron microscopy, X-ray photoelectron spectroscopy). In vitro cytotoxicity assays were investigated by the methyl tetrazolium test. The antibacterial activity of the PLA samples was tested against Escherichia coli and Staphylococcus aureus bacteria strains. Plasma-treated films immobilized with ChS and GlcN, separately and in combination, demonstrated bactericidal effect against the both bacteria strains and also the results revealed that the combination has no synergistic effect on antibacterial action.

Improved recovery from limb ischaemia by delivery of an affinity-isolated heparan sulphate

Peripheral arterial disease is a major cause of limb loss and its prevalence is increasing worldwide. As most standard-of-care therapies yield only unsatisfactory outcomes, more options are needed. Recent cell- and molecular-based therapies that have aimed to modulate vascular endothelial growth factor-165 (VEGF₁₆₅) levels have not yet been approved for clinical use due to their uncertain side effects. We have previously reported a heparan sulphate (termed HS7) tuned to avidly bind VEGF₁₆₅. Here, we investigated the ability of HS7 to promote vascular recovery in a murine hindlimb vascular ischaemia model. HS7 stabilised VEGF₁₆₅ against thermal and enzyme degradation in vitro, and isolated VEGF₁₆₅ from serum via affinity-chromatography. C57BL6 mice subjected to unilateral hindlimb ischaemia injury received daily intramuscular injections of respective treatments (n = 8) and were assessed over 3 weeks by laser Doppler perfusion, magnetic resonance angiography, histology and the regain of function. Mice receiving HS7 showed improved blood reperfusion in the footpad by day 7. In addition, they recovered hindlimb blood volume two- to fourfold faster compared to the saline group; the greatest rate of recovery was observed in the first week. Notably, 17% of HS7-treated animals recovered full hindlimb function by day 7, a number that grew to 58% and 100% by days 14 and 21, respectively. This was in contrast to only 38% in the control animals. These results highlight the potential of purified glycosaminoglycan fractions for clinical use following vascular insult, and confirm the importance of harnessing the activity of endogenous pro-healing factors generated at injury sites.

Chondroitin sulfate proteoglycans from salmon nasal cartilage inhibit angiogenesis

Because cartilage lacks nerves, blood vessels, and lymphatic vessels, it is thought to contain factors that inhibit the growth and development of those tissues. Chondroitin sulfate proteoglycans (CSPGs) are a major extracellular component in cartilage. CSPGs contribute to joint flexibility and regulate extracellular signaling via their attached glycosaminoglycan, chondroitin sulfate (CS). CS and CSPG inhibit axonal regeneration; however, their role in blood vessel formation is largely unknown. To clarify the function of CSPG in blood vessel formation, we tested salmon nasal cartilage proteoglycan (PG), a member of the aggrecan family of CSPG, for endothelial capillary-like tube formation. Treatment with salmon PG inhibited endothelial cell adhesion and in vitro tube formation. The anti-angiogenic activity was derived from CS in the salmon PG but not the core protein. Salmon PG also reduced matrix metalloproteinase expression and inhibited angiogenesis in the chick chorioallantoic membrane. All of these data support an anti-angiogenic role for CSPG in cartilage.

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The role of CSPGs in blood vessel formation in cartilage is largely unknown.

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Treatment of salmon PG inhibited in vitro and in vivo angiogenesis.

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The CS portion of salmon PG was responsible for the anti-angiogenic activity.

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Salmon PG also reduced MMP expression and inhibited cell adhesion.

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Our results support an anti-angiogenic role for CSPG in cartilage.