Low-melt Agarose Research Articles

Electro-elution-based purification of covalent DNA-protein cross-links.

Covalent DNA-protein cross-links (DPCs) are pervasive DNA lesions that challenge genome stability and can be induced by metabolic or chemotherapeutic cross-linking agents including reactive aldehydes, topoisomerase poisons and DNMT1 inhibitors. The purification of x-linked proteins (PxP), where DNA-cross-linked proteins are separated from soluble proteins via electro-elution, can be used to identify DPCs. Here we describe a versatile and sensitive strategy for PxP. Mammalian cells are collected following exposure to a DPC-inducing agent, embedded in low-melt agarose plugs and lysed under denaturing conditions. Following lysis, the soluble proteins are extracted from the agarose plug by electro-elution, while genomic DNA and cross-linked proteins are retained in the plug. The cross-linked proteins can then be analyzed by standard analytical techniques such as sodium dodecyl-sulfate-polyacrylamide gel electrophoresis followed by western blotting or fluorescent staining. Alternatively, quantitative mass spectrometry-based proteomics can be used for the unbiased identification of DPCs. The isolation and analysis of DPCs by PxP overcomes the limitations of alternative methods to analyze DPCs that rely on precipitation as the separating principle and can be performed by users trained in molecular or cell biology within 2-3 d. The protocol has been optimized to study DPC induction and repair in mammalian cells but may also be adapted to other sample types including bacteria, yeast and tissue samples.

Molecular Imaging in Precision-Cut Non-Small Cell Lung Cancer Slices

BackgroundSmall animal models remain invaluable for the preclinical study of emerging molecular imaging agents. However, the data obtained in this setting are generated in genetically homogenous animals that do not mimic human pathophysiology. The purpose of this study was to prospectively validate precision-cut lung slices (PCLSs) obtained from patients with lung cancer as a translational tool for the development of targeted fluorophores. MethodsThe lung tissue was gently inflated with 2% Low-Melt Agarose (Fisher, 16520050) to avoid lung damage and minimize inflation pressure. The slices were then loaded into specialized cylindrical cartridges and inserted into a compressotome, and slices 150 to 350 μm thick were cut. Samples were incubated with fluorophore conjugates for ex vivo validation and immunohistochemical staining for receptor expression. ResultsA total of 184 unique 3-dimensional, architecturally preserved normal lung and non-small cell lung cancer samples were obtained between 2020 and 2022. The median nodule size was 1.1 ± 0.21 cm for benign lesions and 2.1 ± 0.19 cm for malignant nodules. A total of 101 of 135 (74.8%) malignant lesions were adenocarcinoma spectrum lung cancers. The median viability was 9.78 ± 1.86 days, and 1 μM of FAPL-S0456 (high-affinity fibroblast activation protein [FAP] targeting ligand linked to the near-infrared fluorophore S0456, On Target Laboratories)–targeted near-infrared fluorochrome localization demonstrated correlative labeling of FAP-positive tumor areas with a correlation coefficient of +0.94 (P < .01). There was no FAP fluorochrome uptake in normal lungs (r = −1; P < .001). ConclusionsPCLSs comprise a novel human tissue–based translational model that can be used to validate the efficacy of molecular imaging fluorochromes. PCLSs preserve the tumor microenvironment and parenchymal architecture that closely resemble the interactions of the immune and stromal components in humans.

Spinal stiffness assessment by shear wave imaging in a genetic zebrafish scoliosis model treated with anti-inflammatory medication

Background: Idiopathic scoliosis (IS) is a disease characterized by an abnormal lateral curvature of the spine that affects up to 4% of the population. Recent models in zebrafish have elucidated genetic variants which contribute to scoliotic curvature through mechanisms of neuroinflammation, and oxidative stress. Additionally, in-vivo clinical studies have demonstrated that spinal structures stiffen in patients with IS. Shear wave elastography (SWE) is novel, non-invasive imaging technique used to quantitatively estimate tissue stiffness. Objective: Here, we investigated spinal stiffness using SWE in genetically mutant zebrafish with a heterozygous scoliosis variant ( dmh4/+) treated with N-acetylcysteine ethyl ester (NACET), a potent anti-oxidant and anti-inflammatory medication which has been demonstrated to reduce scoliosis curvature formation in zebrafish by up to 70%. Hypothesis: Compared to wildtype, spinal stiffness will increase in dmh4/+ zebrafish and there will be no difference in stiffness for NACET treated zebrafish. Methods: Wildtype (WT; n=20) and mutant ( dmh4/+; n=20) zebrafish aged 10 days post fertilization (dpf) (n=10 &amp; n=10 treated with 500 μM of NACET), 16 dpf (n=10), and 21 dpf (n=10) were sacrificed and submerged in a dish containing 2% low melt agarose gel. An 18.75 MHz linear ultrasound probe was clamped to the dish apparatus dorsal to the zebra fish. Spinal stiffness was assessed by SWE, where faster shear wave velocities (SWV) represent stiffer tissue. The SWV data was processed using a well-verified, custom SWE analysis program on MATLAB by a n operator blinded to the zebrafish genotypes. Results: The spinal curvature of dmh4/+ zebrafish aged 10 dpf were morphologically indistinguishable from WT zebrafish aged 10 dpf. SWV was significantly increased in dmh4/+ zebrafish aged 10 dpf compared to WT (p&lt;0.05). There was no difference in SWV between NACET treated dmh4/+ and NACET treated WT zebrafish aged 10 dpf (p&gt;0.05). Furthermore, NACET treated dmh4/+ and WT zebrafish aged 10 dpf exhibited no difference in SWV compared to untreated WT zebrafish aged 10 dpf (p&gt;0.05). Additionally, SWV was significantly increased in dmh4/+ zebrafish aged 16 and 21 dpf compared to WT (p&lt;0.05). Conclusion: Here we demonstrate that spinal stiffness increases in zebrafish with scoliosis before the curvature pheno type is present and this increase in stiffness is sustained throughout development in later ages. Additionally, spinal stiffness in scoliosis is reduced following treatment with NACET. Our results provide evidence to support clinical trials assessing stiffness as preclinical diagnostic criteria for IS in children. Biotalent Canada - public grant This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Systematic evaluation of agarose- and agar-based bioinks for extrusion-based bioprinting of enzymatically active hydrogels.

Extrusion-based 3D bioprinting enables the production of customized hydrogel structures that can be employed in flow reactors when printing with enzyme-containing inks. The present study compares inks based on either low-melt agarose or agar at different concentrations (3-6%) and loaded with the thermostable enzyme esterase 2 from the thermophilic organism Alicyclobacillus acidocaldarius (AaEst2) with regard to their suitability for the fabrication of such enzymatically active hydrogels. A customized printer setup including a heatable nozzle and a cooled substrate was established to allow for clean and reproducible prints. The inks and printed hydrogel samples were characterized using rheological measurements and compression tests. All inks were found to be sufficiently printable to create lattices without overhangs, but printing quality was strongly enhanced at 4.5% polymer or more. The produced hydrogels were characterized regarding mechanical strength and diffusibility. For both properties, a strong correlation with polymer concentration was observed with highly concentrated hydrogels being more stable and less diffusible. Agar hydrogels were found to be more stable and show higher diffusion rates than comparable agarose hydrogels. Enzyme leaching was identified as a major drawback of agar hydrogels, while hardly any leaching from agarose hydrogels was detected. The poor ability of agar hydrogels to permanently immobilize enzymes indicates their limited suitability for their employment in perfused biocatalytic reactors. Batch-based activity assays showed that the enzymatic activity of agar hydrogels was roughly twice as high as the activity of agarose hydrogels which was mostly attributed to the increased amount of enzyme leaching. Agarose bioinks with at least 4.5% polymer were identified as the most suitable of the investigated inks for the printing of biocatalytic reactors with AaEst2. Drawbacks of these inks are limited mechanical and thermal stability, not allowing the operation of a reactor at the optimum temperature of AaEst2 which is above the melting point of the employed low-melt agarose.

96. Activating MAP2K1 Mutation in Zebrafish Endothelial Cells Causes Arteriovenous Shunts

Purpose: Arteriovenous malformation (AVM) is a sporadic vascular malformation defined by a nidus of irregular blood vessels connecting arteries to veins instead of a normal capillary bed. Somatic activating mutations in MAP2K1 cause extracranial AVM. The purpose of this study was to create an AVM animal model using zebrafish. Methods: Single-cell stage casper;Tg(gata1:dsred) zebrafish embryos were injected with 1 nL of transgenesis mixture: 100 ng/μL of either (1) Control (pTol2-Fli:GFP) or (2) Mutant (pTol2-Fli:GFP-kdrl:MAP2K1K57N) plasmid DNA + 40 ng/μL Tol2 transposase mRNA. Erythrocytes in these fish express the fluorescent protein dsRed. Embryos were anesthetized with 0.4 mg/mL Tricaine, embedded in 1% low-melt agarose and then imaged using a Zeiss LSM 800 Confocal Microscope or a Nikon SMZ18 Fluorescence Microscope. Confocal images were obtained using Zen Blue version 2.5. Embryos were imaged 72 hours post-fertilization. Blood flow was visualized using dsRed fluorescence. Results: Injection of MAP2K1K57N plasmid resulted in abnormal arteriovenous shunts (58/96 transgenic embryos, 60%). The phenotype consisted of either (1) a proximal shunt with blood flowing through a direct connection between proximal aortic vessels to the common cardinal vein and immediately back into the heart (39/58 embryos, 67%) or (2) a mid-trunk shunt between the dorsal artery and posterior cardinal vein (19/58 embryos, 33%). Shunts were not present in control zebrafish (n=65). Endothelial cells at the site of the shunt expressed high levels of the marker transgene confirming shunts contained mutant endothelial cells. Conclusion: Zebrafish endothelial cells expressing mutant MAP2K1 form abnormal arteriovenous shunts. The phenotype recapitulates extracranial human AVM. Mutant MAP2K1 zebrafish are a promising animal model for testing pharmacotherapy to treat AVM.

Investigation of Lysozyme Diffusion in Agarose Hydrogels Employing a Microfluidics-Based UV Imaging Approach.

Hydrogels are polymer-based materials with a high water content. Due to their biocompatible and cell-friendly nature, they play a major role in a variety of biotechnological applications. For many of these applications, diffusibility is an essential property influencing the choice of material. We present an approach to estimate diffusion coefficients in hydrogels based on absorbance measurements of a UV area imaging system. A microfluidic chip with a y-junction was employed to generate a fluid-hydrogel interface and the diffusion of lysozyme from the fluid into the hydrogel phase was monitored. Employing automated image and data processing, analyte concentration profiles were generated from the absorbance measurements and fits with an analytical solution of Fick’s second law of diffusion were applied to estimate diffusion coefficients. As a case study, the diffusion of lysozyme in hydrogels made from different concentrations (0.5–1.5% (w/w)) of an unmodified and a low-melt agarose was investigated. The estimated diffusion coefficients for lysozyme were between 0.80 ± 0.04×10−10 m2 s−1 for 1.5% (w/w) low-melt agarose and 1.14 ± 0.02×10−10 m2 s−1 for 0.5% (w/w) unmodified agarose. The method proved sensitive enough to resolve significant differences between the diffusion coefficients in different concentrations and types of agarose. The microfluidic approach offers low consumption of analyte and hydrogel and requires only relatively simple instrumentation.

Organotypic Slice Cultures as Preclinical Models of Tumor Microenvironment in Primary Pancreatic Cancer and Metastasis.

Realistic preclinical models of primary pancreatic cancer and metastasis are urgently needed to test the therapy response ex vivo and facilitate personalized patient treatment. However, the absence of tumor-specific microenvironment in currently used models, e.g., patient-derived cell lines and xenografts, only allows limited predictive insights. Organotypic slice cultures (OTSCs) comprise intact multicellular tissue, which can be rapidly used for the spatially resolved drug response testing. This protocol describes the generation and cultivation of viable tumor slices of pancreatic cancer and its metastasis. Briefly, tissue is casted in low melt agarose and stored in cold isotonic buffer. Next, tissue slices of 300 µm thickness are generated with a vibratome. After preparation, slices are cultured at an air-liquid interface using cell culture inserts and an appropriate cultivation medium. During cultivation, changes in cell differentiation and viability can be monitored. Additionally, this technique enables the application of treatment to viable human tumor tissue ex vivo and subsequent downstream analyses, such as transcriptome and proteome profiling. OTSCs provide a unique opportunity to test the individual treatment response ex vivo and identify individual transcriptomic and proteomic profiles associated with the respective response of distinct slices of a tumor. OTSCs can be further explored to identify therapeutic strategies to personalize treatment of primary pancreatic cancer and metastasis.

A Layered Mounting Method for Extended Time-Lapse Confocal Microscopy of Whole Zebrafish Embryos.

Dynamics of development can be followed by confocal time-lapse microscopy of live transgenic zebrafish embryos expressing fluorescence in specific tissues or cells. A difficulty with imaging whole embryo development is that zebrafish embryos grow substantially in length. When mounted as regularly done in 0.3-1% low melt agarose, the agarose imposes growth restriction, leading to distortions in the soft embryo body. Yet, to perform confocal time-lapse microscopy, the embryo must be immobilized. This article describes a layered mounting method for zebrafish embryos that restrict the motility of the embryos while allowing for the unrestricted growth. The mounting is performed in layers of agarose at different concentrations. To demonstrate the usability of this method, whole embryo vascular, neuronal and muscle development was imaged in transgenic fish for 55 consecutive hours. This mounting method can be used for easy, low-cost imaging of whole zebrafish embryos using inverted microscopes without requirements of molds or special equipment.

Murine Short Axis Ventricular Heart Slices for Electrophysiological Studies.

Murine cardiomyocytes have been extensively used for in vitro studies of cardiac physiology and new therapeutic strategies. However, multicellular preparations of dissociated cardiomyocytes are not representative of the complex in vivo structure of cardiomyocytes, non-myocytes and extracellular matrix, which influences both mechanical and electrophysiological properties of the heart. Here we describe a technique to prepare viable ventricular slices of adult mouse hearts with a preserved in vivo like tissue structure, and demonstrate their suitability for electrophysiological recordings. After excision of the heart, ventricles are separated from the atria, perfused with Ca2+-free solution containing 2,3-butanedione monoxime and embedded in a 4% low-melt agarose block. The block is placed on a microtome with a vibrating blade, and tissue slices with a thickness of 150-400 µm are prepared keeping the vibration frequency of the blade at 60-70 Hz and moving the blade forward as slowly as possible. Thickness of the slices depends on the further application. Slices are stored in ice cold Tyrode's solution with 0.9 mM Ca2+ and 2,3-butanedione monoxime (BDM) for 30 min. Afterwards, slices are transferred to 37 °C DMEM for 30 min to wash out the BDM. Slices can be used for electrophysiological studies with sharp electrodes or micro electrode arrays, for force measurements to analyze contractile function or to investigate the interaction of transplanted stem cell-derived cardiomyocytes and host tissue. For sharp electrode recordings, a slice is placed into a 3 cm cell culture dish on the heating plate of an inverted microscope. The slice is stimulated with a unipolar electrode, and intracellular action potentials of cardiomyocytes within the slice are recorded with a sharp glass electrode.

Murine Short Axis Ventricular Heart Slices for Electrophysiological Studies

Murine cardiomyocytes have been extensively used for in vitro studies of cardiac physiology and new therapeutic strategies. However, multicellular preparations of dissociated cardiomyocytes are not representative of the complex in vivo structure of cardiomyocytes, non-myocytes and extracellular matrix, which influences both mechanical and electrophysiological properties of the heart. Here we describe a technique to prepare viable ventricular slices of adult mouse hearts with a preserved in vivo like tissue structure, and demonstrate their suitability for electrophysiological recordings. After excision of the heart, ventricles are separated from the atria, perfused with Ca2+-free solution containing 2,3-butanedione monoxime and embedded in a 4% low-melt agarose block. The block is placed on a microtome with a vibrating blade, and tissue slices with a thickness of 150-400 µm are prepared keeping the vibration frequency of the blade at 60-70 Hz and moving the blade forward as slowly as possible. Thickness of the slices depends on the further application. Slices are stored in ice cold Tyrode's solution with 0.9 mM Ca2+ and 2,3-butanedione monoxime (BDM) for 30 min. Afterwards, slices are transferred to 37 °C DMEM for 30 min to wash out the BDM. Slices can be used for electrophysiological studies with sharp electrodes or micro electrode arrays, for force measurements to analyze contractile function or to investigate the interaction of transplanted stem cell-derived cardiomyocytes and host tissue. For sharp electrode recordings, a slice is placed into a 3 cm cell culture dish on the heating plate of an inverted microscope. The slice is stimulated with a unipolar electrode, and intracellular action potentials of cardiomyocytes within the slice are recorded with a sharp glass electrode.

A Method for Sectioning and Immunohistochemical Analysis of Stem Cell-Derived 3-D Organoids.

This unit describes a protocol for embedding, sectioning, and immunocytochemical analysis of pluripotent stem cell-derived 3-D organoids. Specifically, we describe a method to embed iPSC-derived retinal cups in low-melt agarose, acquire thick sections using a vibratome tissue slicer, and perform immunohistochemical analysis. This method includes an approach for antibody labeling that minimizes the amount of antibody needed for individual experiments and that utilizes large-volume washing to increase the signal-to-noise ratio, allowing for clean, high-resolution imaging of developing cell types. The universal methods described can be employed regardless of the type of pluripotent stem cell used and 3-D organoid generated. © 2016 by John Wiley & Sons, Inc.

Hydrogel microstructure live-cell array for multiplexed analyses of cancer stem cells, tumor heterogeneity and differential drug response at single-element resolution.

Specific phenotypic subpopulations of cancer stem cells (CSCs) are responsible for tumor development, production of heterogeneous differentiated tumor mass, metastasis, and resistance to therapies. The development of therapeutic approaches based on targeting rare CSCs has been limited partially due to the lack of appropriate experimental models and measurement approaches. The current study presents new tools and methodologies based on a hydrogel microstructure array (HMA) for identification and multiplex analyses of CSCs. Low-melt agarose integrated with type I collagen, a major component of the extracellular matrix (ECM), was used to form a solid hydrogel array with natural non-adhesive characteristics and high optical quality. The array contained thousands of individual pyramidal shaped, nanoliter-volume micro-chambers (MCs), allowing concomitant generation and measurement of large populations of free-floating CSC spheroids from single cells, each in an individual micro-chamber (MC). The optical live cell platform, based on an imaging plate patterned with HMA, was validated using CSC-enriched prostate and colon cancer cell lines. The HMA methodology and quantitative image analysis at single-element resolution clearly demonstrates several levels of tumor cell heterogeneity, including morphological and phenotypic variability, differences in proliferation capacity and in drug response. Moreover, the system facilitates real-time examination of single stem cell (SC) fate, as well as drug-induced alteration in expression of stemness markers. The technology may be applicable in personalized cancer treatment, including multiplex ex vivo analysis of heterogeneous patient-derived tumor specimens, precise detection and characterization of potentially dangerous cell phenotypes, and for representative evaluation of drug sensitivity of CSCs and other types of tumor cells.

The RAS Guanyl Nucleotide-releasing Protein RasGRP1 Is Involved in Lymphatic Development in Zebrafish

The molecular basis of the lymphatic development remains largely unknown. Using zebrafish as a model, we discovered a novel role for the Ras guanine-releasing protein 1 (RasGRP1), a protein involved in Ras activation in lymphangiogenesis. Secondary lymphatic sprouts from the posterior cardinal vein give rise to thoracic duct which is the first lymphatic vessel in zebrafish. Knockdown of rasgrp1 by injecting morpholino in zebrafish embryos impaired formation of thoracic duct accompanied by pericardial and truck edema, whereas blood vessel development of the embryos was largely unaffected. In rasgrp1-knockdown embryos, the number of sprouts producing the string of parachordal lymphangioblast cells was reduced. Meanwhile the total number of the secondary sprouts was not changed. As a result, the number of venous intersegmental vessels was increased, whereas the number of lymphatic vessel was reduced at a later stage. The lymphatic developmental defects caused by rasgrp1 knockdown could be rescued by ectopic expression of a constitutively active HRas. Further analysis revealed that RasGRP1 knockdown could synergize with flt4/vegfr3 knockdown to induce defects in lymphangiogenesis. Taken together, this finding demonstrates a critical role for RasGRP1 in lymphatic development in zebrafish.

The Phenotypic Characterization of A13/BACii, a Novel Bovine Chondrocytic Cell Line with Differentiation Potential

In cartilage research bovine articular cartilage is used as an alternative to human tissue. However, animal material is subject to availability and primary cultures undergo senescence, limiting their use. Here we report the immortalization of primary bovine chondrocytes, which could be used as a surrogate for freshly isolated chondrocytes. Chondrocytes were isolated from cartilage explants and immortalized using 1.0 µg/ml benzo[alpha]pyrene. For 3-dimensional culture, chondrocytes were resuspended in 0.5% low-melt agarose at high density (HD) and cultured for 24 h prior to determining changes in expression profile and morphology. A13/BACii chondrocytes acquired a ‘flat’ irregular morphology and a foetal-like cell volume (1,509.59 ± 182.04 µm³). The human cell line C-20/A4 showed a statistically similar volume and length to A13/BACii. Two-dimensional-cultured A13/BACii expressed elevated levels of type I collagen (col1), reduced levels of type II collagen (col2) compared to freshly isolated chondrocytes and an overall col2 to col1 expression ratio (col2:col1) of 0.11 ± 0.01. Upon 3-dimensional encapsulation, there was a significant rise in col2 expression in both A13/BACii and C-20/A4, suggesting a capacity for redifferentiation in both cell lines with a return of col2:col1 values of A13/BACii to values previously observed in primary chondrocytes. A13/BACii chondrocytes expressed aggrecan, matrix metalloproteinase (MMP)-3, MMP-9 and MMP-13, further supporting indications of the differentiated phenotype. Here we report the creation of a novel chondrocytic cell line and demonstrate its strong potential for redifferentiation upon HD 3-dimensional encapsulation, providing an alternative to conventional dedifferentiated cell lines and primary culture.

Targeted Deletion of Jun/AP-1 in Alveolar Epithelial Cells Causes Progressive Emphysema and Worsens Cigarette Smoke–Induced Lung Inflammation

Chronic obstructive pulmonary disease appears to occur slowly and progressively over many years, with both genetic factors and environmental modifiers contributing to its pathogenesis. Although the c-Jun/activator protein 1 transcriptional factor regulates cell proliferation, apoptosis, and inflammatory responses, its role in lung pathogenesis is largely unknown. In this study, we report decreased expression levels of c-Jun mRNA and protein in the lung tissues of patients with advanced chronic obstructive pulmonary disease, and the genetic deletion of c-Jun specifically in alveolar epithelial cells causes progressive emphysema with lung inflammation and alveolar air space enlargement, which are cardinal features of emphysema. Although mice lacking c-Jun specifically in lung alveolar epithelial cells appear normal at the age of 6 weeks, when exposed to long-term cigarette smoke, c-Jun-mutant mice display more lung inflammation with perivascular and peribronchiolar infiltrates compared with controls. These results demonstrate that the c-Jun/activator protein 1 pathway is critical for maintaining lung alveolar cell homeostasis and that loss of its expression can contribute to lung inflammation and progressive emphysema.

Cocultures of Adult and Juvenile Chondrocytes Compared With Adult and Juvenile Chondral Fragments

Background: The use of allogenic juvenile chondrocytes or autologous chondral fragments has shown promising laboratory results for the repair of chondral lesions. Hypothesis: Juvenile chondrocytes would not affect matrix production when mixed with adult chondrocytes or cartilage fragments. Study Design: Controlled laboratory study. Methods: Cartilage sources consisted of 3 adult and 3 juvenile (human) donors. In part 1, per each donor, juvenile chondrocytes were mixed with adult chondrocytes in 5 different proportions: 100%, 50%, 25%, 12.5%, and 0%. Three-dimensional cultures in low-melt agarose were performed. At 6 weeks, biochemical and histologic analyses were performed. In part 2, isolated adult, isolated juvenile, and mixed 3-dimensional cultures (1:1) were performed with chondral fragments (<1 mm), both with low-melt agarose and a hyaluronic acid scaffold. At 2 and 6 weeks, cultures were evaluated with biochemical and histologic analyses. Results: Part 1: Biochemical and histologic analyses showed that isolated juvenile cultures performed significantly better than mixed and isolated adult cultures. No significant differences were noted between mixed cultures (1:1) and isolated adult cultures. Part 2: Biochemical and histologic results at 6 weeks showed that mixed cartilage fragment cultures performed better than isolated adult cultures in terms of proteoglycans/DNA ratio (P = .014), percentage of safranin O–positive cells (P = .012), Bern score (P = .001), and collagen type II. No statistically significant difference was noted between juvenile and mixed cultures. Conclusion: Extracellular matrix production of juvenile chondrocytes is inhibited by adult chondrocytes. The addition of juvenile cartilage fragments to adult fragments improves matrix production, with a positive interaction between the 2 sources. Clinical Relevance: Even if the underlying mechanisms are still unknown, this study describes the behavior of juvenile/adult cocultures using both chondrocytes and cartilage fragments, with potential for new research and clinical applications.

Three-Dimensional Construction of Bilayer Networks using Shape Encoded Hydrogel

The newly invented system - droplet interface bilayer (DIB) - is beginning to emerge as a versatile platform not only for studying the basic properties of membrane proteins but also to construct novel nano-devices. Small volumes of aqueous buffer when injected into hexadecane take the form of droplets. These droplets when loaded with lipids assemble a lipid monolayer at the water/oil interface. By carefully touching two such monolayer encased aqueous droplets a bilayer can be formed which is conducive to the insertion of membrane proteins.Here we demonstrate that contacting two hydrogel surfaces coated with lipid monolayers can form a lipid bilayer, forming a so-called hydrogel interface bilayer (HIB). We use two of the most commonly available hydrogels, a natural polymer agarose and a synthetic polymer polyethylene glycol diacrylate (PEG-DA), to form HIBs. The lipid bilayers formed using both the polymers are conducive to the insertion of membrane proteins as shown by the insertion of α-hemolysin pore.Thus far, solid-supported lipid bilayers for reconstituting membrane proteins have been assembled in a 2-D plane. We present a simple approach to form lipid monolayers on a manipulable 3-D system based on hydrogels. Millimeter sized particles were formed by using low melt agarose or PEG-diacrylate. Agarose and PEG-DA based hydrogels can be molded in different shapes and coated with a lipid monolayer, which on bringing together gives a lipid bilayer as monitored by an increase in the capacitance. Polymers molded in different shapes have been used in a number of applications ranging from reaction coding in enzyme catalysis to providing a 3-D environment for cell growth to drug delivery. We propose the use of such solid particles incorporating membrane pores for the use of constructing communicating electrical devices.

Mouse Models of Congenital Heart Defects

One of the puzzling things about genetic disruptions in mice that affect heart development is the overwhelming number of conotruncal anomalies and the infrequency with which certain other malformations are reported. For instance, venous malformations such as total anomalous pulmonary venous return (TAPVR) or partial anomalous pulmonary venous return (PAPVR) have not been reported in a mutant mouse. Coronary artery anomalies are reported infrequently, and when they are reported it is because they are obvious. Conotruncal anomalies such as common trunk, double-outlet right ventricle, and pulmonary stenosis with overriding aorta are frequently associated with mouse germ line and conditional gene deletions. Although conotruncal malformations represent the highest percentage of congenital heart defects in the human population, TAPVR and PAPVR occur in a significant number of babies. Further, coronary anomalies affecting the stems of the coronary arteries frequently are seen in conotruncal malformations in babies but are rarely reported in mouse models. Article see p 314 Isolated TAPVR is a rare lesion and occurs in only about 1 in 17 000 live births.1 PAPVR is much more common and has been reported in 1 in 160 individuals (0.6%) and 0.4% to 0.7% of postmortem examinations, with 90% of these associated with an atrial septal defect.2 The majority of patients with TAPVR have symptoms of cyanosis and congestion within the first year of life. If left untreated, about 80% would die. In contrast, PAPVR frequently is not discovered until adulthood and is not usually a cause of death. Although the overall incidence of PAPVR in autopsy cases has been estimated to be 0.7%,3 the true prevalence may be higher,4 as several reports have appeared with PAPVR as an incidental finding that in most of these cases is asymptomatic. PAPVR can present as an isolated structural abnormality, but it …

Organotypic Slice Culture of E18 Rat Brains

Organotypic slice cultures from embryonic rodent brains are widely used to study brain development. While there are often advantages to an in-vivo system, organotypic slice cultures allow one to perform a number of manipulations that are not presently feasible in-vivo. To date, organtotypic embryonic brain slice cultures have been used to follow individual cells using time-lapse microscopy, manipulate the expression of genes in the ganglionic emanances (a region that is hard to target by in-utero electroporation), as well as for pharmacological studies. In this video protocol we demonstrate how to make organotypic slice cultures from rat embryonic day 18 embryos. The protocol involves dissecting the embryos, embedding them on ice in low melt agarose, slicing the embedded brains on the vibratome, and finally plating the slices onto filters in culture dishes. This protocol is also applicable in its present form to making organotypic slice cultures from different embryonic ages for both rats and mice.

Organotypic Slice Culture of E18 Rat Brains

Organotypic slice cultures from embryonic rodent brains are widely used to study brain development. While there are often advantages to an in-vivo system, organotypic slice cultures allow one to perform a number of manipulations that are not presently feasible in-vivo. To date, organtotypic embryonic brain slice cultures have been used to follow individual cells using time-lapse microscopy, manipulate the expression of genes in the ganglionic emanances (a region that is hard to target by in-utero electroporation), as well as for pharmacological studies. In this video protocol we demonstrate how to make organotypic slice cultures from rat embryonic day 18 embryos. The protocol involves dissecting the embryos, embedding them on ice in low melt agarose, slicing the embedded brains on the vibratome, and finally plating the slices onto filters in culture dishes. This protocol is also applicable in its present form to making organotypic slice cultures from different embryonic ages for both rats and mice.