Name: shrinky-dink hanging drops: a simple way to form and culture embryoid bodies
Uploaded: 2008-03-05T22:18:00
Description: Watch this Scientific Journal Video about Shrinky-Dink Hanging Drops: A Simple Way to Form and Culture Embryoid Bodies at JoVE.com

We would like to thank CIRM for support of this work. The cell line was generously donated from Dr. Andras Nagy at Mount Sinai Hospital, Toronto, Ontario.

1. Making Shrinky-Dink Mold
<ol>
<li>Print the desired pattern on shrinky-dink sheet using a good definition printer.</li>
<li>Bake shrinky-dink sheet at 163&deg; C for about 10 minutes, or until fully shrunk and having aquired a regular shape.</li>
<li>After shrinky-dink mold has cooled down, submerge it in an isopropanol bath until the complete surface is barely covered.</li>
<li>Carefully, spray some acetone over the mold and shake container a few times. Add more isopropanol to wash out acetone excess and&nbsp;repeat...

<ol>
	<li>Keller, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+differentiation+of+embryonic+stem+cells.">In vitro differentiation of embryonic stem cells.</a> Curr Opin Cell Biol. 7, 862-869 (1995).</li><li>Doetschman, T. C., Eistetter, H., Katz, M., Schmidt, W., Kemler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+in+vitro+development+of+blastocyst-derived+embryonic+stem+cell+lines:+Formation+of+visceral+yolk+sac,+blood+islands+and+myocardium.">The in vitro development of blastocyst-derived embryonic stem cell lines: Formation of visceral yolk sac, blood islands and myocardium.</a> Journal of Embryology and Experimental Morphology. 87, 27-45 (1985).</li><li>Park, J., Cho, C. H., Parashurama, N., Li, Y., Berthiaume, F., Toner, M., Tilles, A. W., Yarmush, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfabrication-based+modulation+of+embryonic+stem+cell+differentiation.">Microfabrication-based modulation of embryonic stem cell differentiation.</a> Lab Chip. 7, 1018-1028 (2007).</li><li>Koike, M., Sakaki, S., Amano, Y., Kurosawa, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+embryoid+bodies+of+mouse+embryonic+stem+cells+formed+under+various+culture+conditions+and+estimation+of+differentiation+status+of+such+bodies.">Characterization of embryoid bodies of mouse embryonic stem cells formed under various culture conditions and estimation of differentiation status of such bodies.</a> J Biosci Bioeng. 104, 294-299 (2007).</li><li>Hwang, N. S., Varghese, S., Elisseeff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+differentiation+of+stem+cells.">Controlled differentiation of stem cells.</a> Advanced Drug Delivery Reviews. 60, 199-204 (2008).</li><li>Adelman, C. A., Chattopadhyay, S., Bieker, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+BMP/BMPR/Smad+pathway+directs+expression+of+the+erythroid-specific+EKLF+and+GATA1+transcription+factors+during+embryoid+body+differentiation+in+serum-free+media.">The BMP/BMPR/Smad pathway directs expression of the erythroid-specific EKLF and GATA1 transcription factors during embryoid body differentiation in serum-free media.</a> Development. 129, 539-549 (2002).</li><li>Tanaka, N., Takeuchi, T., Neri, O. V., Sills, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser-assisted+blastocyst+dissection+and+subsequent+cultivation+of+embryonic+stem+cells+in+a+serum/cell+free+culture+system:+applications+and+preliminary+results+in+a+murine+model.">Laser-assisted blastocyst dissection and subsequent cultivation of embryonic stem cells in a serum/cell free culture system: applications and preliminary results in a murine model.</a> J Transl Med. 4, (2006).</li></ol>

We have developed a simple, rapid, and scalable culture method to load pre-defined numbers of cells into microfabricated wells (molded from Shrinky-Dinks) and maintain them for embryoid body development. Finally, these cells are easily accessible for further analysis and experimentation. This method is amenable to any lab and requires no dedicated equipment because we obviate the need for photolithography. We can vary the size of the microwells as well as the concentration of cells/ wells to change the number and size of...

<div>
<table border="1">
	<thead>
		<tr>
			<th>Material Name</th>
			<th>Type</th>
			<th>Company</th>
			<th>Catalogue Number</th>
			<th>Comment</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>Shrink-Dink Film</td>
			<td>Material</td>
			<td>K&#38;B Innovations</td>
			<td>D300-10A</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS</td>
			<td>Material</td>
			<td>Dow Corning</td>
			<td>Sylgard 184</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Reagent</td>
			<td>Fisher Scientific</td>
			<td>A16P-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Reagent</td>
			<td>Fisher Scientific</td>
			<td>A405P-4</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Reagent</td>
			<td>Sigma</td>
			<td>P4417</td>
			<td></td>
		</tr>
		<tr>
			<td>BMP-4</td>
			<td>Reagent</td>
			<td>R and D systems</td>
			<td>314-BP-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Knock-Out DMEM (KO DMEM)</td>
			<td>Reagent</td>
			<td>Invitrogen</td>
			<td>10829</td>
			<td></td>
		</tr>
		<tr>
			<td>KnockOut Sirum Replacement (KSR)</td>
			<td>Reagent</td>
			<td>Invitrogen</td>
			<td>10828</td>
			<td></td>
		</tr>
		<tr>
			<td>Penn-Strep</td>
			<td>Reagent</td>
			<td>Invitrogen</td>
			<td>15070-063</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Reagent</td>
			<td>Invitrogen</td>
			<td>25030-081</td>
			<td></td>
		</tr>
		<tr>
			<td>Non-essential Amino Acids (NEAA)</td>
			<td>Reagent</td>
			<td>Invitrogen</td>
			<td>11140</td>
			<td></td>
		</tr>
		<tr>
			<td>D-mercaptoethanol (BME)</td>
			<td>Reagent</td>
			<td>Calbiochem</td>
			<td>444203</td>
			<td></td>
		</tr>
		<tr>
			<td>Leukemia Inhibitory Factor (LIF) {ESGRO 106 units}</td>
			<td>Reagent</td>
			<td>Chemicon</td>
			<td>ESG1106</td>
			<td></td>
		</tr>
		<tr>
			<td>Printer</td>
			<td>Tool</td>
			<td>HP</td>
			<td>Laser Jet 2420d</td>
			<td></td>
		</tr>
		<tr>
			<td>Oven</td>
			<td>Tool</td>
			<td>Yamato Scientific</td>
			<td>DP-22</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="5">For the mESC media(McCloskey lab protocol): (for total media prepared: 50ml; 100ml) KO DMEM: 40.8ml; 81.6ml 15% KSR: 7.5ml; 15ml 1x Penn-Strep: .5ml; 1ml 2mM L-glutamine: .5ml; 1ml NEAA : .5ml; 1ml LIF: 100ul; 200ul BMP-4 (10ng/ml): 50ul; 100ul Diluted BME: 50ul; 100ul (Add 35ul of sterile filtered BME to 5ml of PBS and syringe filter sterilize. Discard after 2 weeks. Final concentration in the solution is .1mM)</td>
		</tr>
	</tbody>
</table>
</div>

shrinky-dink hanging drops: a simple way to form and culture embryoid bodies

Embryoid bodies (EB) are aggregates of embryonic stem cells. The most common way of creating these aggregates is the hanging drop method, a laborious approach of pipetting an arbitrary number of cells into well plates. The interactions between the stem cells forced into close proximity of one another promotes the generation of the EBs. Because the media in each of the wells has to be manually exchanged every day, this approach is manually intensive.
Moreover, because environmental parameters including cell-cell, cell-soluble factor interactions, pH, and oxygen availability can be functions of EB size, cell populations obtained from traditional hanging drops can vary dramatically even when cultured under identical conditions. Recent studies have indeed shown that the initial number of cells forming the aggregate can have significant effects on stem cell differentiation. We have developed a simple, rapid, and scalable culture method to load pre-defined numbers of cells into microfabricated wells and maintain them for embryoid body development. Finally, these cells are easily accessible for further analysis and experimentation. This method is amenable to any lab and requires no dedicated equipment. We demonstrate this method by creating embryoid bodies using a red fluorescent mouse cell line (129S6B6-F1).

Watch this Scientific Journal Video about Shrinky-Dink Hanging Drops: A Simple Way to Form and Culture Embryoid Bodies at JoVE.com

Shrinky-Dink Hanging Drops: A Simple Way to Form and Culture Embryoid Bodies

We show a simple and rapid method to load pre-defined numbers of cells into microfabricated wells and maintain them for embryoid body development.

Embryoid bodies (EB) are aggregates of embryonic stem cells. The most common way of creating these aggregates is the hanging drop method, a laborious ...

shrinky-dink-hanging-drops-simple-way-to-form-culture-embryoid

Research

JoVE Journal

Biology

Pyrosequencing: A Simple Method for Accurate Genotyping

Pharmacogenetic research benefits first-hand from the abundance of information provided by the completion of the Human Genome Project. With such a tremendous amount of data available comes an explosion of genotyping methods. Pyrosequencing(R) is one of the most thorough yet simple methods to date used to analyze polymorphisms. It also has the ability to identify tri-allelic, indels, short-repeat polymorphisms, along with determining allele percentages for methylation or pooled sample assessment. In addition, there is a standardized control sequence that provides internal quality control. This method has led to rapid and efficient single-nucleotide polymorphism evaluation including many clinically relevant polymorphisms. The technique and methodology of Pyrosequencing is explained.


Pyrosequencing(R) is one of the most thorough yet simple methods to date used to analyze polymorphisms. This method has led to rapid and efficient single-nucleotide polymorphism evaluation including many clinically relevant polymorphisms. The technique and methodology of Pyrosequencing is explained.

Pharmacogenetic research benefits first-hand from the abundance of information provided by the completion of the Human Genome Project. With such a ...

Method for Culture of Early Chick Embryos ex vivo (New Culture)

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying  the formation and patterning of brain, neural tube, somite and heart primordia. Applications of chick embryo culture include electroporation of DNA or RNA constructs in order to analyze gene function, grafts of growth factor coated beads such as FGFs and BMPs , as well as whole mount in situ hybridization and immunohistochemistry. This video demonstrates the different steps in chick embryo culture; First, the embryo is explanted in saline. Then, the embryo is centered on a glass ring. The membranes surrounding the embryo are lifted along the walls of the ring. The ring is then placed in a culture dish containing a pool of albumine. The culture dish is sealed and placed in a humid chamber, where the embryo is cultured for up to 24 hrs. Finally, the embryo is removed from the ring, fixed and processed for further applications. A troubleshooting guide is also presented.

Method for Culture of Early Chick Embryos ex vivo New Culture

This video demonstrates New culture, a method by which chick embryos are cultured outside the egg for up to 24 hr. This method enables one to study early development (primitive streak to 14 som.), a period corresponding to E7-9 in mouse. Applications of this technique include electroporation, in situ hybridization and immunohistochemistry.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Analysis of Pluripotent Stem Cells by using Cryosections of Embryoid Bodies

Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of blastocyst-stage early mammalian embryos 1. A crucial stage in the differentiation of ES cells is the formation of embryoid bodies (EBs) aggregates 2, 3. EB formation is based on spontaneous aggregation when ES cells are cultured in non adherent plates. Three-dimensional EB recapitulates many aspects of early mammalian embryogenesis and differentiate into the three germ layers: ectoderm, mesoderm and endoderm 4.
Immunofluorescence and in situ hybridization are widely used techniques for the detection of target proteins and mRNA present in cells of a tissue section 5, 6, 7. Here we present a simple technique to generate high quality cryosections of embryoid bodies. This approach relies on the spatial orientation of EB embedding in OCT followed by the cryosection technique. The resulting sections can be subjected to a wide variety of analytical procedures in order to characterize populations of cells containing certain proteins, RNA or DNA. In this sense, the preparation of EB cryosections (10&mu;m) are essential tools for histology staining analysis (e.g. Hematoxilin and Eosin, DAPI), immunofluorescence (e.g. Oct4, nestin) or in situ hybridization. This technique can also help to understand aspects of embryogenesis with regards to the maintenance of the tri-dimensional spherical structure of EBs.

Pluripotent stem cells growing in suspension differentiate into embryoid bodies (EBs). Here we demonstrate how to obtain high quality EB cryosections useful for studying cellular and molecular aspects of embryogenesis, while preserving their organization as aggregates.

Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of blastocyst-stage early mammalian embryos 1. A crucial stage in the ...

Simple and Efficient Technique for the Preparation of Testicular Cell Suspensions

Mammalian testes are very complex organs that contain over 30 different cell types, including somatic testicular cells and different stages of germline cells. This heterogeneity is an important drawback concerning the study of the bases of mammalian spermatogenesis, as pure or enriched cell populations in certain stages of sperm development are needed for most molecular analyses1.
 Various strategies such as Staput2,3, centrifugal elutriation1, and flow cytometry (FC)4,5 have been employed to obtain enriched or purified testicular cell populations in order to enable differential gene expression studies. 
It is required that cells are in suspension for most enrichment/ purification approaches. Ideally, the cell suspension will be representative of the original tissue, have a high proportion of viable cells and few multinucleates - which tend to form because of the syncytial nature of the seminiferous epithelium6,7 - and lack cell clumps1 . Previous reports had evidenced that testicular cell suspensions prepared by an exclusively mechanical method clumped more easily than trypsinized ones1 . On the other hand, enzymatic treatments with RNAses and/or disaggregating enzymes like trypsin and collagenase lead to specific macromolecules degradation, which is undesirable for certain downstream applications. The ideal process should be as short as possible and involve minimal manipulation, so as to achieve a good preservation of macromolecules of interest such as mRNAs. Current protocols for the preparation of cell suspensions from solid tissues are usually time-consuming, highly operator-dependent, and may selectively damage certain cell types1,8 . 
	The protocol presented here combines the advantages of a highly reproducible and extremely brief mechanical disaggregation with the absence of enzymatic treatment, leading to good quality cell suspensions that can be used for flow cytometric analysis and sorting4, and ulterior gene expression studies9 .

A novel protocol for the mechanical preparation of testicular cell suspensions from rodent material, avoiding enzymes and detergents, is described. The method is very simple, fast, reproducible, and renders good quality cell suspensions, which are suitable for flow sorting and RNA extraction.

Mammalian testes are very complex organs that contain over 30 different cell types, including somatic testicular cells and different stages of germline ...

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly effective at mapping highly repetitive sequences to heterochromatic regions, where computational approaches face prohibitive challenges. Here we describe a streamlined protocol for DNA ISH that circumvents formamide washes that are standard steps in other DNA ISH protocols. Our protocol is optimized for hybridization with short single strand DNA probes that carry fluorescent dyes, which effectively mark repetitive DNA sequences within heterochromatic chromosomal regions across a number of different insect tissue types. However, applications may be extended to use with larger probes and visualization of single copy (non-repetitive) DNA sequences. We demonstrate this method by mapping several different repetitive sequences to squashed chromosomes from Drosophila melanogaster neural cells and Nasonia vitripennis spermatocytes. We show hybridization patterns for both small, commercially synthesized probes and for a larger probe for comparison. This procedure uses simple laboratory supplies and reagents, and is ideal for investigators who have little experience with performing DNA ISH.

Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

Here, we present a simple method for performing fluorescence DNA in situ hybridization (DNA ISH) to visualize repetitive heterochromatic sequences on slide-mounted chromosomes. The method requires minimal reagents and it is versatile for use with short or long probes, different tissues, and detection with fluorescence or non-fluorescence-based signals.

DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly ...

Using Mouse Mammary Tumor Cells to Teach Core Biology Concepts: A Simple Lab Module

Undergraduate biology students are required to learn, understand and apply a variety of cellular and molecular biology concepts and techniques in preparation for biomedical, graduate and professional programs or careers in science. To address this, a simple laboratory module was devised to teach the concepts of cell division, cellular communication and cancer through the application of animal cell culture techniques. Here the mouse mammary tumor (MMT) cell line is used to model for breast cancer. Students learn to grow and characterize these animal cells in culture and test the effects of traditional and non-traditional chemotherapy agents on cell proliferation. Specifically, students determine the optimal cell concentration for plating and growing cells, learn how to prepare and dilute drug solutions, identify the best dosage and treatment time course of the antiproliferative agents, and ascertain the rate of cell death in response to various treatments. The module employs both a standard cell counting technique using a hemocytometer and a novel cell counting method using microscopy software. The experimental procedure lends to open-ended inquiry as students can modify critical steps of the protocol, including testing homeopathic agents and over-the-counter drugs. In short, this lab module requires students to use the scientific process to apply their knowledge of the cell cycle, cellular signaling pathways, cancer and modes of treatment, all while developing an array of laboratory skills including cell culture and analysis of experimental data not routinely taught in the undergraduate classroom.

A feasible laboratory module for biology undergraduates that explores advanced cellular and molecular concepts using animal cell culture is described. Students grow, characterize and manipulate a breast cancer cell model by exposure to chemotherapy agents. Cell viability is assayed through cell counting using both a standard and novel method.

Undergraduate biology students are required to learn, understand and apply a variety of cellular and molecular biology concepts and techniques in ...

Filtration Isolation of Nucleic Acids:  A Simple and Rapid DNA Extraction Method

FINA, filtration isolation of nucleic acids, is a novel extraction method which utilizes vertical filtration via a separation membrane and absorbent pad to extract cellular DNA from whole blood in less than 2 min. The blood specimen is treated with detergent, mixed briefly and applied by pipet to the separation membrane. The lysate wicks into the blotting pad due to capillary action, capturing the genomic DNA on the surface of the separation membrane. The extracted DNA is retained on the membrane during a simple wash step wherein PCR inhibitors are wicked into the absorbent blotting pad. The membrane containing the entrapped DNA is then added to the PCR reaction without further purification. This simple method does not require laboratory equipment and can be easily implemented with inexpensive laboratory supplies. Here we describe a protocol for highly sensitive detection and quantitation of HIV-1 proviral DNA from 100 &#181;l whole blood as a model for early infant diagnosis of HIV that could readily be adapted to other genetic targets.

We describe here a simple and rapid paper-based DNA extraction method of HIV proviral DNA from whole blood detected by quantitative PCR. This protocol can be extended for use in detecting other genetic markers or using alternative amplification methods.

FINA, filtration isolation of nucleic acids, is a novel extraction method which utilizes vertical filtration via a separation membrane and absorbent pad ...

A Simple Fluorescence-based Reporter Assay to Identify Cellular Components Required for Ricin Toxin A Chain (RTA) Trafficking in Yeast

Bacterial and plant A/B toxins exploit the natural trafficking pathways in eukaryotic cells to reach their intracellular target(s) in the cytosol and to ultimately kill. Such A/B toxins generally consist of an enzymatically active Asubunit (e.g., ricin toxin A (RTA)) and one or more cell binding Bsubunit(s), which are responsible for toxin binding to specific cell surface receptors. Our current knowledge of how A/B toxins are capable of efficiently intoxicating cells helped scientists to understand fundamental cellular mechanisms, like endocytosis and intracellular protein sorting in higher eukaryotic cells. From a medical point of view, it is likewise important to identify the major toxin trafficking routes to find adequate treatment solutions for patients or to eventually develop therapeutic toxin-based applications for cancer therapy.
Since genome-wide analyses of A/B toxin trafficking in mammalian cells is complex, time-consuming, and expensive, several studies on A/B toxin transport have been performed in the yeast model organism Saccharomyces cerevisiae. Despite being less complex, fundamental cellular processes in yeast and higher eukaryotic cells are similar and very often results obtained in yeast can be transferred to the mammalian situation.
Here, we describe a fast and easy to use reporter assay to analyze the intracellular trafficking of RTA in yeast. An essential advantage of the new assay is the opportunity to investigate not only RTA retro-translocation from the endoplasmic reticulum (ER) into the cytosol, but rather endocytosis and retrograde toxin transport from the plasma membrane into the ER. The assay makes use of a reporter plasmid that allows indirect measurement of RTA toxicity through fluorescence emission of the green fluorescent protein (GFP) after in vivo translation. Since RTA efficiently prevents the initiation of protein biosynthesis by 28S rRNA depurination, this assay allows the identification of host cell proteins involved in intracellular RTA transport through the detection of changes in fluorescence emission.

A Simple Fluorescence-based Reporter Assay to Identify Cellular Components Required for Ricin Toxin A Chain RTA Trafficking in Yeast

In the manuscript, we describe the use of a yeast-based fluorescence reporter assay to identify cellular components involved in the trafficking and killing processes of the cytotoxic A subunit of the plant toxin ricin (RTA).

Bacterial and plant A/B toxins exploit the natural trafficking pathways in eukaryotic cells to reach their intracellular target(s) in the cytosol and to ...

A Simple Method for Isolation of Soybean Protoplasts and Application to Transient Gene Expression Analyses

Soybean (Glycine max (L.) Merr.) is an important crop species and has become a legume model for the studies of genetic and biochemical pathways. Therefore, it is important to establish an efficient transient gene expression system in soybean. Here, we report a simple protocol for the preparation of soybean protoplasts and its application for transient functional analyses. We found that young unifoliate leaves from soybean seedlings resulted in large quantities of high quality protoplasts. By optimizing a PEG-calcium-mediated transformation method, we achieved high transformation efficiency using soybean unifoliate protoplasts. This system provides an efficient and versatile model for examination of complex regulatory and signaling mechanisms in live soybean cells and may help to better understand diverse cellular, developmental and physiological processes of legumes.

We developed a simple and efficient protocol for the preparation of large quantities of soybean protoplasts to study complex regulatory and signaling mechanisms in live cells.

Soybean (Glycine max (L.) Merr.) is an important crop species and has become a legume model for the studies of genetic and biochemical pathways. ...

A Proximal Culture Method to Study Paracrine Signaling Between Cells

Intercellular interactions play an important role in many biological processes, including tumor progression, immune responses, angiogenesis, and development. Paracrine or juxtacrine signaling mediates such interactions. The use of a conditioned medium and coculture studies are the most common methods to discriminate between these two types of interactions. However, the effect of localized high concentrations of secreted factors in the microenvironment during the paracrine interactions is not accurately recapitulated by conditioned medium and, thus, may lead to imprecise conclusions. To overcome this problem, we have devised a proximal culture method to study paracrine signaling. The two cell types are grown on either surface of a 10 &#181;m-thick polycarbonate membrane with 0.4 &#181;m pores. The pores allow the exchange of secreted factors and, at the same time, inhibit juxtacrine signaling. The cells can be collected and lysed at the endpoint to determine the effects of the paracrine signaling. In addition to allowing for localized concentration gradients of secreted factors, this method is amenable to experiments involving prolonged periods of culture, as well as the use of inhibitors. While we use this method to study the interactions between ovarian cancer cells and the mesothelial cells they encounter at the site of metastasis, it can be adapted to any two adherent cell types for researchers to study paracrine signaling in various fields, including tumor microenvironment, immunology, and development.

Paracrine and juxtacrine cellular interactions play an important role in many biological processes, including tumor progression, immune responses, angiogenesis, and development. Here, a proximal culture method is used to study paracrine signaling where the localized concentrations of the secreted factors are maintained while preventing direct cellular contact.