Novel mineral contrast agent for magnetic resonance studies of bone implants grown on a chick chorioallantoic membrane

Development and characterization of a chick embryo chorioallantoic membrane (CAM) based platform for evaluation of vasoactive medications

Among various anti-cancer therapies, tumor vascular disrupting agents (VDAs) play a crucial role, for which their off-targeting effects on normal vessels need also to be investigated. The purpose of this study was to set up an in-ovo platform that combines a laser speckle contrast imaging (LSCI) modality with chick embryo chorioallantoic membrane (CAM) to real-time monitor vascular diameters and perfusion without and with intravascular injection. Two eggshell windows for both observation or measurement and injection were opened. Dynamic blood perfusion images and corresponding statistic graphs were acquired by using a LSCI unit on CAMs from embryo date (ED) 9 to ED15. A dedicated fine needle catheter was made for slow intravascular administration over 30 min with simultaneous LSCI acquisition. To verify the connectivity between CAM vessels and the embryonic circulations in the egg, contrast-enhanced 3D micro computed tomography (μCT), 2D angiography and histology were executed. This platform was successfully established to acquire, quantify and demonstrate vascular and hemodynamic information from the CAM. Chick embryos even with air cell opened remained alive from ED9 to ED15. Through collecting LSCI derived CAM vascular diameter and perfusion parameters, ED12 was determined as the best time window for vasoactive drug studies. A reverse correlation between CAM vessel diameter and blood perfusion rate was found (p < 0.002). Intravascular infusion and simultaneous LSCI acquisition for 30 min in ovo proved feasible. Contrast-enhanced angiography and histomorphology could characterize the connectivity between CAM vasculature and embryonic circulation. This LSCI-CAM platform was proved effective for investigating the in-ovo hemodynamics, which paves the road for further preclinical research on vasoactive medications including VDAs.

The Chicken Embryo Chorioallantoic Membrane as an In Vivo Model for Photodynamic Therapy

For many decades the chicken embryo chorioallantoic membrane (CAM) has been used for research as an in vivo model in a large number of different fields, including toxicology, bioengineering, and cancer research. More specifically, the CAM is also a suitable and convenient model system in the field of photodynamic therapy (PDT), mainly due to the easy access of its membrane and the possibility of grafting or growing tumors on the membrane and, interestingly, to study the PDT effects on its dense vascular network. In addition, the CAM is simple to handle and cheap. Since the CAM is not innervated until later stages of the embryo development, its use in research is simplified compared to other in vivo models as far as ethical and regulatory issues are concerned. In this review different incubation and drug administration protocols of relevance for PDT are presented. Moreover, data regarding the propagation of light at different wavelengths and CAM development stages are provided. Finally, the effects induced by photobiomodulation on the CAM angiogenesis and its impact on PDT treatment outcome are discussed.

Utilisation of Chick Embryo Chorioallantoic Membrane as a Model Platform for Imaging-Navigated Biomedical Research

The fertilised chick egg and particularly its chorioallantoic membrane (CAM) have drawn continuing interest in biomedicine and bioengineering fields, especially for research on vascular study, cancer, drug screening and development, cell factors, stem cells, etc. This literature review systemically introduces the CAM's structural evolution, functions, vascular features and the circulation system, and cell regulatory factors. It also presents the major and updated applications of the CAM in assays for pharmacokinetics and biodistribution, drug efficacy and toxicology testing/screening in preclinical pharmacological research. The time course of CAM applications for different assays and their advantages and limitations are summarised. Among these applications, two aspects are emphasised: (1) potential utility of the CAM for preclinical studies on vascular-disrupting agents (VDAs), promising for anti-cancer vascular-targeted therapy, and (2) modern imaging technologies, including modalities and their applications for real-time visualisation, monitoring and evaluation of the changes in CAM vasculature as well as the interactions occurring after introducing the tested medical, pharmaceutical and biological agents into the system. The aim of this article is to help those working in the biomedical field to familiarise themselves with the chick embryo CAM as an alternative platform and to utilise it to design and optimise experimental settings for their specific research topics.

Evolving applications of the egg: chorioallantoic membrane assay and ex vivo organotypic culture of materials for bone tissue engineering

The chick chorioallantoic membrane model has been around for over a century, applied in angiogenic, oncology, dental and xenograft research. Despite its often perceived archaic, redolent history, the chorioallantoic membrane assay offers new and exciting opportunities for material and growth factor evaluation in bone tissue engineering. Currently, superior/improved experimental methodology for the chorioallantoic membrane assay are difficult to identify, given an absence of scientific consensus in defining experimental approaches, including timing of inoculation with materials and the analysis of results. In addition, critically, regulatory and welfare issues impact upon experimental designs. Given such disparate points, this review details recent research using the ex vivo chorioallantoic membrane assay and the ex vivo organotypic culture to advance the field of bone tissue engineering, and highlights potential areas of improvement for their application based on recent developments within our group and the tissue engineering field.

PHYSICOCHEMICAL CHARACTERIZATION: COMPARATIVE EVALUATION OF ALLOGRAFT BIOMATERIALS AND AUTOGENOUS BONE

Objectives: bone substitutes used in oral surgery include allografts, xenografts and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone by encouraging new bone ingrowth into the defect site. The aim of this study was to evaluate a number ofphysical and chemical properties in a variety of allografts biomaterials used in oral surgery and to compare them with those of autogenous bone. Materials and methods: autogenous bone andfive different allograft biomaterials were studied by high-resolution X-ray diffractometry, atomic absorption spectrometry, laser diffraction, and checked for their chemical composition, calcium release concentration, crystallinity and granulation size. Results: the highest calcium release concentration was 24.94 mg/gforPuros® and the lowest one was 4.05 mg/gfor OsteoSponge® compared to 20.15 mg/g to natural bone. The range ofparticles size, in term of median size D50, varied between 394.24 pm for DIZG Spongiosa® and 902.41 pm for OsteoSponge®, compared to 282.1 pm for natural bone. Bone and Puros® displayed a hexagonal shape as bone except and OsteoSponge® which showed a triclinic shape and all the rest showed monoclinic shape. Conclusion: a bone substitute of choice depends largely on its clinical application that is associated to its biological and mechanical performance. These morphological differences between biomaterials greatly influence their in-vivo behavior of biomaterials. Significant differences were detected in terms of calcium concentration, particles size, and crystallinity.

Bedside, Benchtop, and Bioengineering: Physicochemical Imaging Techniques in Biomineralization

The need to quantify physicochemical properties of mineralization spans many fields. Clinicians, mineralization researchers, and bone tissue bioengineers need to be able to measure the distribution, quantity, and the mechanical and chemical properties of mineralization within a wide variety of substrates from injured muscle to electrospun polymer scaffolds and everything in between. The techniques available to measure these properties are highly diverse in terms of their complexity and utility. Therefore it is of the utmost importance that those who intend to use them have a clear understanding of the advantages and disadvantages of each technique and its appropriateness to their specific application. This review provides all of this information for each technique and uses heterotopic ossification and engineered bone substitutes as examples to illustrate how these techniques have been applied. In addition, we provide novel data using advanced techniques to analyze human samples of combat related heterotopic ossification.

Comparison of medetomidine, thiopental and ketamine/midazolam anesthesia in chick embryos for in ovo Magnetic Resonance Imaging free of motion artifacts

Non-invasive assessment of the perfusion capacity of tissue engineered constructs grown on the chorioallantoic membrane by MRI is often hampered by motion artifacts. Therefore, we examined the suitability of three anesthetic regimes for sufficient sedation of the chick embryo. Medetomidine at a dosage of 0.3 mg/kg, was compared to thiopental at 100 mg/kg and ketamine/midazolam at 50 mg/kg and 1 mg/kg, respectively. These soluble anesthetics were applied by dropping a total volume of 0.3 mL onto the surface of the CAM. Motion was videotaped through the window of the eggshell and scored semi-quantitatively. Medetomidine performed best in terms of reduced motion; onset of anesthesia occurred within 10 minutes and for the following 30 minutes, allowing proper in vivo MRI measurements. The other regimen were not sedating deep enough (ketamine/midazolam) and not long enough (thiopental). In sum, medetomidine allows proper sedation for MRI assessment of the perfusion capacity in a tissue engineered construct placed on the CAM.

A new in vivo magnetic resonance imaging method to noninvasively monitor and quantify the perfusion capacity of three-dimensional biomaterials grown on the chorioallantoic membrane of chick embryos

Adequate vascularization in biomaterials is essential for tissue regeneration and repair. Current models do not allow easy analysis of vascularization of implants in vivo, leaving it a highly desirable goal. A tool that allows monitoring of perfusion capacity of such biomaterials noninvasively in a cheap, efficient, and reliable in vivo model would hence add great benefit to research in this field. We established, for the first time, an in vivo magnetic resonance imaging (MRI) method to quantify the perfusion capacity of a model biomaterial, DegraPol(®) foam scaffold, placed on the embryonic avian chorioallantoic membrane (CAM) in ovo. Perfusion capacity was assessed through changes in the longitudinal relaxation rate before and after injection of a paramagnetic MRI contrast agent, Gd-DOTA (Dotarem(®); Guerbet S.A.). Relaxation rate changes were compared in three different regions of the scaffold, that is, at the interface to the CAM, in the middle and on the surface of the scaffold (p<0.05). The highest relaxation rate changes, and hence perfusion capacities, were measured in the interface region where the scaffold was attached to the CAM, whereas the surface of the scaffold showed the lowest relaxation rate changes. A strong positive correlation was obtained between relaxation rate changes and histologically determined vessel density (R(2) = 0.983), which corroborates our MRI findings. As a proof-of-principle, we measured the perfusion capacity in different scaffold materials, silk fibroin either with or without human dental pulp stem cells. For these, three to four times larger perfusion capacities were obtained compared to DegraPol; demonstrating that our method is sensitive to reveal such differences. In summary, we present a novel in vivo method for analyzing the perfusion capacity in three-dimensional-biomaterials grown on the CAM, enabling the determination of the perfusion capacity of a large variety of bioengineered materials.

The chicken chorioallantoic membrane model in biology, medicine and bioengineering

The chicken chorioallantoic membrane (CAM) is a simple, highly vascularized extraembryonic membrane, which performs multiple functions during embryonic development, including but not restricted to gas exchange. Over the last two decades, interest in the CAM as a robust experimental platform to study blood vessels has been shared by specialists working in bioengineering, development, morphology, biochemistry, transplant biology, cancer research and drug development. The tissue composition and accessibility of the CAM for experimental manipulation, makes it an attractive preclinical in vivo model for drug screening and/or for studies of vascular growth. In this article we provide a detailed review of the use of the CAM to study vascular biology and response of blood vessels to a variety of agonists. We also present distinct cultivation protocols discussing their advantages and limitations and provide a summarized update on the use of the CAM in vascular imaging, drug delivery, pharmacokinetics and toxicology.

Physicochemical characteristics of bone substitutes used in oral surgery in comparison to autogenous bone

Bone substitutes used in oral surgery include allografts, xenografts, and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone, but little is currently known about their physicochemical characteristics. The aim of this study was to evaluate a number of physical and chemical properties in a variety of granulated mineral-based biomaterials used in dentistry and to compare them with those of autogenous bone. Autogenous bone and eight commercial biomaterials of human, bovine, and synthetic origins were studied by high-resolution X-ray diffraction, atomic absorption spectrometry, and laser diffraction to determine their chemical composition, calcium release concentration, crystallinity, and granulation size. The highest calcium release concentration was 24. 94 mg/g for Puros and the lowest one was 2.83 mg/g for Ingenios β-TCP compared to 20.15 mg/g for natural bone. The range of particles sizes, in terms of median size D50, varied between 1.32 μm for BioOss and 902.41 μm for OsteoSponge, compared to 282.1 μm for natural bone. All samples displayed a similar hexagonal shape as bone, except Ingenios β-TCP, Macrobone, and OsteoSponge, which showed rhomboid and triclinic shapes, respectively. Commercial bone substitutes significantly differ in terms of calcium concentration, particle size, and crystallinity, which may affect their in vivo performance.

Imaging the hard/soft tissue interface

Interfaces between different tissues play an essential role in the biomechanics of native tissues and their recapitulation is now recognized as critical to function. As a consequence, imaging the hard/soft tissue interface has become increasingly important in the area of tissue engineering. Particularly as several biotechnology based products have made it onto the market or are close to human trials and an understanding of their function and development is essential. A range of imaging modalities have been developed that allow a wealth of information on the morphological and physical properties of samples to be obtained non-destructively in vivo or via destructive means. This review summarizes the use of a selection of imaging modalities on interfaces to date considering the strengths and weaknesses of each. We will also consider techniques which have not yet been utilized to their full potential or are likely to play a role in future work in the area.

Zero echo time magnetic resonance imaging of contrast-agent-enhanced calcium phosphate bone defect fillers

Calcium phosphate cements (CPCs) are widely used bone substitutes. However, CPCs have similar radiopacity as natural bone, rendering them difficult to be differentiated in classical X-ray and computed tomography imaging. As conventional magnetic resonance imaging (MRI) of bone is cumbersome, due to low water content and very short T(2) relaxation time, ultra-short echo time (UTE) and zero echo time (ZTE) MRI have been explored for bone visualization. This study examined the possibility to differentiate bone and CPC by MRI. T(1) and T(2)* values determined with UTE MRI showed little difference between bone and CPC; hence, these materials were difficult to separate based on T(1) or T(2) alone. Incorporation of ultra-small particles of iron oxide and gadopentetatedimeglumine (Gd-DTPA; 1 weight percentage [wt%] and 5 wt% respectively) into CPC resulted in visualization of CPC with decreased intensity on ZTE images in in vitro and ex vivo experiments. However, these additions had unfavorable effects on the solidification time and/or mechanical properties of the CPC, with the exception of 1% Gd-DTPA alone. Therefore, we tested this material in an in vivo experiment. The contrast of CPC was enhanced at an early stage postimplantation, and was significantly reduced in the 8 weeks thereafter. This indicates that ZTE imaging with Gd-DTPA as a contrast agent could be a valid radiation-free method to visualize CPC degradation and bone regeneration in preclinical experiments.