Ms. Audrey Thomas-Gahring is acknowledged for her GC/MS work. We would also like to thank Massimo Marzorati for editing the manuscript.

1. Materials and Preparations
NOTE: The defined medium is purchased as a powder (see Table of Materials). The composition of the defined medium in g/L is the following: Arabinogalactan (1.2), Pectin (2.0), Xylan (0.5), Glucose (0.4), Yeast extract (3.0), Special peptone (1.0), Mucin (2.0), L-cysteine-HCl (0.2).
<ol>
	<li>Prepare the defined medium
	<ol>
		<li>Fill a 4 L flask with 2 L of double distilled, deionized water.</li>
		<li>Add 29.2...

<ol>
	<li>Johansson, M., Larsson, J., Hansson, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+two+mucus+layers+of+colon+are+organized+by+the+MUC2+mucin,+whereas+the+outer+layer+is+a+legislator+of+host-microbial+interactions.">The two mucus layers of colon are organized by the MUC2 mucin, whereas the outer layer is a legislator of host-microbial interactions.</a> Proceedings of the National Academy of Sciences of the United States of America. 108 (1), 4659-4665 (2011).</li><li>Xu, J., Gordon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Honor+thy+symbionts.">Honor thy symbionts.</a> Proceedings of the National Academy of Sciences of the United States of America. 100 (18), 10452-10459 (2003).</li><li>Jandhyala, S., Talukdar, R., Subramanyam, C., Vuyyuru, H., Sasikala, M., Reddy, D. <a target="_blank" 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In vitro culturing systems have been developed to study the gut microbiota of the large intestine. They use apparatuses designed to simulate the physiological conditions of the gastro intestinal tract, promoting the growth of a mature gut microbial community for each region of the colon33. While the concept is logical and comprehensible, the actual running of in vitro culturing systems to study the gut microbiota requires precision and an understanding of what is required and expected to produce r...

The gut microbiota is a community of micro-organisms that reside in the human gastrointestinal tract (GIT).&#160; This community reaches maximum concentration in the colon, which is estimated to hold 1013-1014 bacteria, from 500-1,000 species, that live in symbiosis with the colon milieu1,2. The composition and functionality of the gut microbiota change spatially along the GIT, forming region specific communities, with the most diversity found distally2,3,4,5. For each anatomical region, separate microbial communities reside in the lumen and on the mucosal lining6. The lumen community has more direct access to nutrients as substrates move through the luminal compartment7. Despite this, some bacteria reside preferentially in the mucus layer, utilizing mucin produced by the colon cells as an energy source1,5,8. The difference in microenvironments between the luminal and mucosal phases results in divergence and the development of phase specific communities. Together, these communities provide metabolic functions, such as nutrient metabolism and the production of vitamins, and immunological functions, such as preventing the colonization of human pathogens1,3,9. The gut microbiota also works functionally in conjugation with the human colon cells3.
As an important part of the human GIT, it is not surprising that the gut microbiota is known to contribute to both host health and disease status3,9,10,11,12. A shift in the gut microbial population has been associated with multiple human diseases, including GIT disorders like intestinal bowel disease (IBD) and intestinal bowel syndrome (IBS), but also other diseases, such as obesity, circulatory disease, and autism3,9,10,11,12.&#160; Metabolites produced from the gut microbiota have a global effect, reaching locations far from the gut12,13. For example, the gut-brain axis is associated with mental disorders like anxiety and depression14. Therefore, studying the gut microbiota is important to multiple fields of research, and is applicable to many diseases, even those not often associated with the GIT.
While it is widely acknowledged that studying the gut microbiota is important, it is a complicated endeavor. Multiple animal models are available, from small animals like zebrafish, rats, and mice, to larger ones like monkeys and pigs15-19. However, the application of these animals in terms of the human gut microbiota is not straightforward, since these animals have a unique bacterial community that has evolved based on environment and diet, and they are anatomically distinct from humans20,21. The use of human subjects removes the question of relevance yet introduces another set of challenges. Human studies are expensive, time consuming, and are ethically constrained11. Moreover, confounding factors influence the gut microbiota in human studies, including age or developmental stage, environment, diet, medication, and genetic factors2,4,22.&#160; There are also restrictions on what can be tested in humans, and which type of samples can be harvested at what times4.&#160;
One critical disadvantage of using an in vivo system to study the gut microbiota is the presence of mammalian components. The gut microbiota and human cells interact with one another, and in an in vivo setting, it is impossible to distinguish the two. The metabolites produced by the gut microbiota are taken in by the colon cells, so measurements cannot be calculated with precision. Therefore, any mechanistic study must be limited to end-point measurements11. Another major disadvantage for in vivo studies is the inability to harvest samples from the different regions of the GIT longitudinally23. This does not allow for the assessment of changes that may occur in the microenvironments of the colon over time12.&#160; Many in vivo studies, including human studies, rely on analysis of fecal samples to detect changes to the gut microbiota12. While this is informative, it does not provide data on the gut microbiota across the GIT and does not differentiate between the luminal and mucosal communities5,6,7,8.
For the gut microbiota, the application of an in vitro method is required to study the dynamics of the bacterial community, without interference from the mammalian components. Using an in vitro method allows for the tight control of environmental conditions10, testing of multiple parameters simultaneously, and the ability to sample longitudinally, and in large volumes11. Since an in vitro method utilizes a mechanical device and not a host, no considerations are needed for age, environment, diet, or genetic background. These systems can be used to test either the entire gut microbiota community, only selected organisms, or even single strains. Importantly, in vitro results are reproducible, yet retain a level of diversity comparable to in vivo studies11,22.
Depending on the hypothesis in question and the desired results, in vitro studies can be performed in numerous ways.&#160; They can utilize single-vessel systems and simple methods, such as incubating samples with fecal homogenate24 or performing single batch cultures over the course of 24-48 h25. They can also be accomplished using single-vessel systems and more complex methods, such as using a chemostat system to produce a stable gut microbial community11. However, the use of a single reactor can over-simplify the microbiota12 since it only represents one section of the colon, even though the colon is composed of the ascending, transverse, and descending regions.
In order to study the gut microbiota community that develops in the different regions of the colon (the ascending, transverse, and descending regions), a complex, multi-stage system can be employed. In these systems, multiple vessels are set up to mimic the different regions of the colon, so the gut microbiota of the ascending, transverse, and descending regions are cultivated independently. These vessels are connected, using pumps to move substrates in sequence, from the ascending to the transverse to the descending colon regions, mimicking the flow of nutrients through the GIT.
The objective of this study was to demonstrate how a 5-stage in vitro culture system (see Table of Materials) can be used to cultivate the gut microbiota community, and to demonstrate community dynamics in terms of stability and composition. In this system, one vessel represents the stomach and one represent the small intestine. The colon is divided into three regions (ascending, transverse, descending), with one vessel representing each region26. In this experimental setup, two complete systems were run in parallel, with Unit 1 containing mucin carriers to represents the mucosal surface and Unit 2 containing no mucin carriers. The communities that developed in the luminal and mucosal phases of each region were compared to each other, and to the fecal inoculum over time using 16S rRNA gene sequencing and SCFA analysis. The results presented demonstrate the type of community, both in terms of composition and functionality, which can be produced from this type of in vitro system.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>TWINSHIME</td>
			<td>Prodigest</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>defined medium (Adult M-SHIME growth medium with starch)</td>
			<td>Prodigest</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Masterflex tubing</td>
			<td>cole Parmer</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Urine Drainage bag</td>
			<td>Bard</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Labsorb</td>
			<td>Sigma-Aldrich</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Fecal sample</td>
			<td>Openbiome</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringes</td>
			<td>Becton Dickson</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Defined medium</td>
			<td>Prodigest</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Oxgall Bile</td>
			<td>Becton Dickson</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Pancreatin</td>
			<td>Sigma-Aldrich</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass ware</td>
			<td>Ace Glass</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Porcine mucin</td>
			<td>Sigma-Aldrich</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacteriological agar</td>
			<td>Sigma-Aldrich</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilization pouches</td>
			<td>VWR</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>BeadBug</td>
			<td>Benchmark Scientific</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Triple-Pure High Impact Zirconium 0.1mm Bead beater tube</td>
			<td>Benchmark Scientific</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAse free, DNAse free, sterile water</td>
			<td>Roche</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Shimadzu QP2010 Ultra GC/MS</td>
			<td>Shimadzu</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Stabilwax-DA column, 30m, 0.25mm ID, 0.25&#181;m</td>
			<td>Restek</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>plastic mucin carriers</td>
			<td>Prodigest</td>
			<td>NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

applying advanced in vitro culturing technology to study the human gut microbiota

The human gut microbiota plays a vital role in both human health and disease. Studying the gut microbiota using an in vivo model, is difficult due to its complex nature, and its diverse association with mammalian components. The goal of this protocol is to culture the gut microbiota in vitro, which allows for the study of the gut microbiota dynamics, without having to consider the contribution of the mammalian milieu. Using in vitro culturing technology, the physiological conditions of the gastro intestinal tract are simulated, including parameters such as pH, temperature, anaerobiosis, and transit time. The intestinal surface of the colon is simulated by adding mucin-coated carriers, creating a mucosal phase, and adding further dimension. The gut microbiota is introduced by inoculating with the human fecal material. Upon inoculation with this complex mixture of bacteria, specific microbes are enriched in the different longitudinal (ascending, transverse and descending colons) and transversal (luminal and mucosal) environments of the in vitro model. It is crucial to allow the system to reach a steady state, in which the community and the metabolites produced remain stable. The experimental results in this manuscript demonstrate how the inoculated gut microbiota community develops into a stable community over time. Once steady state is achieved, the system can be used to analyze bacterial interactions and community functions or to test the effects of any additives on the gut microbiota, such as food, food components, or pharmaceuticals.

The above protocol describes set up, inoculation, and running of a 5-stage in vitro system to study the gut microbiota of the colon. To generate the data presented below, following DNA extraction, 16S rRNA marker gene DNA sequencing of the V1V2 region was performed using the high throughput sequencing (e.g., MiSeq Illumina platform) by the Microbiome Center at the Children&#8217;s Hospital of Philadelphia27. QIIME (Quantitative Insight into Microbial Ecolo...

Watch this Scientific Journal Video about Applying Advanced In Vitro Culturing Technology to Study the Human Gut Microbiota at JoVE.com

Applying Advanced In Vitro Culturing Technology to Study the Human Gut Microbiota

Here, we present a protocol for culturing the gut microbiota of the colon in vitro, using a series of bioreactors that simulate the physiological conditions of the gastro intestinal tract.

The human gut microbiota plays a vital role in both human health and disease. Studying the gut microbiota using an in vivo model, is difficult due to its ...

The goal of this protocol is to culture gut microbiota in vitro. It will allow for the study of microbiota dynamics without having to consider the contribution of a modern component. Using this multi-stage in vitro system, we count the microbiota community to develop in the lumin and on the mucosal of multi-regions of the colon can be started simultaneously.A visual demonstration of this method is helpful due to the complexity of this in vitro system. Begin by filling the ascending colon with 500 milliliters of defined medium, the transverse colon with 800 milliliters of defined medium, and the descending colon with 600 milliliters of defined medium. Add mucin agricarriers to the colon regions in an amount proportional to the volume of the reactor, and use the sample tube and syringe to remove any excess defined medium from each reactor.Use the pH probes to adjust the pH in each reactor. And turn on the nitrogen flush for 20 minutes. Next, thaw the fecal homogenate according to the manufacturer's guidelines before loading a 60 milliliter syringe with the fecal homogenate sample.Then, inoculate each colon reactor through the sample port with an amount of homogenate equal to 5%of each reactor volume for overnight culture with pH control. The next morning, clean the luer lock on the sample port of each bioreactor with alcohol. When the ports have dried, connect the 30 milliliter syringe, cleared of all air, to one of the sample ports.Withdraw the plunger three to five times to ensure a thorough mixing of the vessel components before aspirating 15 milliliters of the culture's supernate from the bioreactor. Then transfer the luminal sample into a sterile Falcon tube and place on ice. For DNA analysis, collect one to three milliliters of luminal fluid using a five milliliter syringe.Collect the supernate form the other bioreactors in the same manner. To set aside sample material for short chain fatty acid analysis, centrifuge 15 milliliters of the luminal sample of interest, and syringe filter the supernate through a 0.2 micrometer pore filter for minus 80 degree Celsius storage. To set aside sample material for DNA analysis, centrifuge one milliliter of luminal fluid and store the pellet at minus 80 degrees Celsius.For mucosal sample harvest, remove the prepared mucin carriers from four degrees Celsius storage and turn on the nitrogen flush. Quickly open the reactor lid and replace 50%of the carriers in each reactor with new ones. When all of the carriers have been replaced, quickly reseal the lid and maintain the nitrogen flush for another 20 minutes.Then aliquot 0.25 to 0.5 grams of mucin carrier agar into individual two milliliter tubes for minus 80 degree Celsius storage until DNA extraction. Three times a day the system automatically cycles. This begins with 140 milliliters of defined medium transferred into the stomach bioreactor followed by a one hour incubation with pH control.At the end of the incubation, the contents of the stomach are transferred into the small intestine along with 60 milliliters of pancreatic juice. In the small intestine bioreactor, the pH is adjusted automatically to 6.7 to 6.9, and the contents incubate for 90 minutes. During this incubation, the nitrogen flush for each system is turned on for a total of 10 minutes.At the end of this incubation, the contents from the small intestine are transferred into the ascending colon, from the ascending colon to the transverse colon, from the transverse colon to the descending colon, and from the descending colon to the waste. In this representative principal coordinates analysis, the community changed depreciably between days one and seven. However, from day 11 post inoculation until the end of the experiment, the samples occupied a small region of the principal coordinates analysis space for both sample to sample distance scores based on operational taxonomic unit, presence to absence, and abundance.The measurement of three prominent short-chained fatty acids reveals that Propionic acid, Butanoic acid, and Acetic acid fluctuate from the start of the experiment until day 15 post inoculation. After day 15, the amounts of these acids produced in each colon region remained constant with only minimal changes until the end of the experiment. Analysis of the stable community for the luminal and mucosal phase of each colon region demonstrates that the communities that develop in the individual colon regions of the in vitro system are similar to the fecal inoculum composition.Comparison of the alpha diversity of the in vitro system reveals a similar level of diversity as that of the inoculum for all of the regions except the luminal samples from the ascending region. Demonstrating that the in vitro culture system is able to produce a community comparable to the fecal inoculum both in terms of composition and diversity. To produce a stable gut microbiota community using this protocol, it is critical to ensure that solutions are prepared accurately and that anerobic conditions and pH parameters are maintained throughout the experiment.Following this procedure, samples can be analyzed for community composition using next gen DNA sequencing followed by bioinformatic analysis and for functionality using metabolomics.

applying-advanced-vitro-culturing-technology-to-study-human-gut

Research

JoVE Journal

Bioengineering

13.7K Views.  Agricultural Research Service, United States Department of Agriculture. The goal of this protocol is to culture gut microbiota in vitro. It will allow for the study of microbiota dynamics without having to consider the contribution of a modern component. Using this multi-stage in vitro system, we count the microbiota community to develop in the lumin and on the mucosal of multi-regions of the colon can be started simultaneously.A visual demonstration of this method is helpful due to the complexity of this in vitro system. Begin by filling the ascending col...

Video: Applying Advanced In Vitro Culturing Technology to Study the Human Gut Microbiota

Here, we present a protocol for culturing the gut microbiota of the colon in vitro, using a series of bioreactors that simulate the physiological conditions of the gastro intestinal...

analysis of interactions between endobiotics and human gut microbiota using in vitro bath fermentation systems

Analysis of Interactions between Endobiotics and Human Gut Microbiota Using In Vitro Bath Fermentation Systems

Described here is a protocol to investigate the interactions between endobiotics and human gut microbiota using in vitro batch fermentation...

a method to assess bacteriocin effects on the gut microbiota of mice

A Method to Assess Bacteriocin Effects on the Gut Microbiota of Mice

Bacteriocins are believed to play a key role in defining microbial diversity in different ecological niches. Here, we describe an efficient procedure to assess how bacteriocins affect gut microbiota composition in an animal model.

an ex vivo gut organ culture system to study host-microbiota interactions

When the PDMS is set, pull out the needles from the mold and carefully release the culture device and lid from the plastic molds. Remove PDMS residues from the well outline using a surgical...

An Ex Vivo Gut Organ Culture System to Study Host-Microbiota Interactions

In this video, we describe the methodology for setting up an ex vivo gut organ culture system to study the interactions between mouse intestinal tissue fragments and specific gut bacteria. The device consists of two pairs of input-output ports, the first connecting the intestinal tissue lumen and supplying the specific bacterial suspension into it, and the second continuously supplying media to the device&#39;s wells to maintain ex vivo tissue...

an in vitro batch-culture model to estimate the effects of interventional regimens on human fecal microbiota

An In Vitro Batch-culture Model to Estimate the Effects of Interventional Regimens on Human Fecal Microbiota

This protocol describes an in vitro batch-culture fermentation system of human fecal microbiota, using inulin (a well-known prebiotic and one of the most widely studied microbiota modulators) to demonstrate the use of this system in estimating effects of specific interventions on fecal microbiota composition and metabolic...

fecal microbiota transplantation and detection of prevalence of iga-coated bacteria in the gut

Fecal Microbiota Transplantation and Detection of Prevalence of IgA-Coated Bacteria in the Gut

We established an efficient way to deplete intestinal bacteria in three days, and subsequently transplant fecal microbiota via gavage of fecal fluid prepared from fresh or frozen intestinal contents in mice. We also present an optimized method to detect the frequency of IgA-coated bacteria in the...

a gut-on-a-chip model to study the gut microbiome-nervous system axis

A Gut-on-a-Chip Model to Study the Gut Microbiome-Nervous System Axis

neuroHuMiX is an advanced gut-on-a-chip model to study the interactions of bacterial, epithelial, and neuronal cells under proximal and representative co-culture conditions. This model allows unravelling of the molecular mechanisms underlying the communication between the gut microbiome and the nervous...

an intestinal gut organ culture system for analyzing host-microbiota interactions

An Intestinal Gut Organ Culture System for Analyzing Host-Microbiota Interactions

This article presents a unique method for analyzing host-microbiome interactions using a novel gut organ culture system for ex vivo experiments.

visualization of gut microbiota-host interactions via fluorescence in situ hybridization, lectin staining, and imaging

Visualization of Gut Microbiota-host Interactions via Fluorescence In Situ Hybridization, Lectin Staining, and Imaging

This streamlined protocol details a workflow to detect and image bacteria in complex tissue samples, from fixing the tissue to staining microbes with fluorescent in situ hybridization.

Visualization of Gut Microbiota-host Interactions via Fluorescence In Situ Hybridization, Lectin Staining, and Imaging

an in vivo method for evaluating the gut-blood barrier and liver metabolism of microbiota products

An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

The access of nutrients, microbiota metabolites and medicines to the circulation is controlled by the gut-blood barrier (GBB). We describe a direct method for measuring the GBB permeability in vivo, which, in contrast to commonly used indirect methods, is virtually not affected by liver and kidney...

An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

investigating the alleviating effects of bacillus cereus administration on colitis through gut microbiota modulation

Investigating the Alleviating Effects of Bacillus cereus Administration on Colitis through Gut Microbiota Modulation

Here, we present a protocol to establish the antibiotic-induced pseudo-germ-free dextran sulfate sodium-induced colitis mouse model to investigate the role of gut microbiota in regulating the positive effects of Bacillus cereus on colitis.

Investigating the Alleviating Effects of Bacillus cereus Administration on Colitis through Gut Microbiota Modulation

methods for culturing human femur tissue explants to study breast cancer cell colonization of the metastatic niche

Methods for Culturing Human Femur Tissue Explants to Study Breast Cancer Cell Colonization of the Metastatic Niche

Protocols are described for studying breast cancer cell migration, proliferation and colonization in a human bone tissue explant model...

optimized ex-ovo culturing of chick embryos to advanced stages of development

Optimized Ex-ovo Culturing of Chick Embryos to Advanced Stages of Development

Viewing and accessing the chicken embryo during development can be challenging. We have developed an ex ovo method that is simple, cost effective, and can easily be used in a classroom or research setting. This method provides access to the embryo into late stages of embryonic development (HH 40).

Optimized Ex-ovo Culturing of Chick Embryos to Advanced Stages of Development

cardiac spheroids as in vitro bioengineered heart tissues to study human heart pathophysiology

Cardiac Spheroids as in vitro Bioengineered Heart Tissues to Study Human Heart Pathophysiology

This protocol aims to fabricate 3D cardiac spheroids (CSs) by co-culturing cells in hanging drops.&#160;Collagen-embedded CSs are treated with doxorubicin (DOX, a cardiotoxic agent) at physiological concentrations to model heart failure. In vitro testing using DOX-treated CSs may be used to identify novel therapies for heart failure...

preparing and rearing axenic insects with tissue cultured seedlings for host-gut microbiota interaction studies of the leaf beetle

Preparing and Rearing Axenic Insects with Tissue Cultured Seedlings for Host-Gut Microbiota Interaction Studies of the Leaf Beetle

To obtain an axenic insect, its egg surface is sterilized, and the hatched larva is subsequently reared using axenic leaves. This method provides an efficient way for axenic insect preparation without administering antibiotics or developing an artificial diet, which can also be applied to other leaf-eating...

advanced cardiac rhythm management by applying optogenetic multi-site photostimulation in murine hearts

Advanced Cardiac Rhythm Management by Applying Optogenetic Multi-Site Photostimulation in Murine Hearts

This work reports a method for controlling the cardiac rhythm of intact murine hearts of transgenic channelrhodopsin-2 (ChR2) mice using local photostimulation with a micro-LED array and simultaneous optical mapping of epicardial membrane...

assessing the viability of a synthetic bacterial consortium on the in vitro gut host-microbe interface

Assessing the Viability of a Synthetic Bacterial Consortium on the In Vitro Gut Host-microbe Interface

Gut host-microbe interactions were assessed using a novel approach combining a synthetic oral community, in vitro gastrointestinal digestion, and a model of the small intestine epithelium. We present a method that can be adapted to evaluate cell invasion of pathogens and multi-species biofilms, or even to test probiotic formulations&#39;...

Assessing the Viability of a Synthetic Bacterial Consortium on the In Vitro Gut Host-microbe Interface

in vitro model of fetal human vessel on-chip to study developmental mechanobiology

Author Spotlight: Studying hiPSC-Derived Endothelial Cells Cultured Under Fluidic-Mediated Mechanical Stimulation 

Described here is a simple workflow to differentiate endothelial cells from human pluripotent stem cells followed by a detailed protocol for their mechanical stimulation. This allows for the study of the developmental mechanobiology of endothelial cells. This approach is compatible with downstream assays of live cells collected from the culture chip after mechanical...

In Vitro Model of Fetal Human Vessel On-chip to Study Developmental Mechanobiology

an in vitro model to study heterogeneity of human macrophage differentiation and polarization

An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization

Monocyte-derived macrophages are important cells of the innate immune system. Here, we describe an easy to use in vitro model to generate these cells. Using gradient centrifugation, negative bead isolation and specific cell culture conditions, monocyte-derived macrophages can be generated for phenotypic and functional...

An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Human Cartilage Tissue Fabrication Using Three-dimensional Inkjet Printing Technology

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and regenerative medicine. With digital control&#160;cells, scaffolds, and growth factors can be precisely deposited to the desired two-dimensional (2D) and three-dimensional (3D) locations rapidly. Therefore, this technology is an ideal approach to fabricate tissues mimicking their native anatomic structures. In order to engineer cartilage with native zonal organization, extracellular matrix composition (ECM), and mechanical properties, we developed a bioprinting platform using a commercial inkjet printer with simultaneous photopolymerization capable for 3D cartilage tissue engineering. Human chondrocytes suspended in poly(ethylene glycol) diacrylate (PEGDA) were printed for 3D neocartilage construction via layer-by-layer assembly. The printed cells were fixed at their original deposited positions, supported by the surrounding scaffold in simultaneous photopolymerization. The mechanical properties of the printed tissue were similar to the native cartilage. Compared to conventional tissue fabrication, which requires longer UV exposure, the viability of the printed cells with simultaneous photopolymerization was significantly higher. Printed neocartilage demonstrated excellent glycosaminoglycan (GAG) and collagen type II production, which was consistent with gene expression. Therefore, this platform is ideal for accurate cell distribution and arrangement for anatomic tissue engineering.

The methods described in this paper show how to convert a commercial inkjet printer into a bioprinter with simultaneous UV polymerization. The printer is capable of constructing 3D tissue structure with cells and biomaterials. The study demonstrated here constructed a 3D neocartilage.

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and ...

Culturing Mouse Cardiac Valves in the Miniature Tissue Culture System

Heart valve disease is a major burden in the Western world and no effective treatment is available. This is mainly due to a lack of knowledge of the molecular, cellular and mechanical mechanisms underlying the maintenance and/or loss of the valvular structure. 
Current models used to study valvular biology include in vitro cultures of valvular endothelial and interstitial cells. Although, in vitro culturing models provide both cellular and molecular mechanisms, the mechanisms involved in the 3D-organization of the valve remain unclear. While in vivo models have provided insight into the molecular mechanisms underlying valvular development, insight into adult valvular biology is still elusive. 
In order to be able to study the regulation of the valvular 3D-organization on tissue, cellular and molecular levels, we have developed the Miniature Tissue Culture System. In this ex vivo flow model the mitral or the aortic valve is cultured in its natural position in the heart. The natural configuration and composition of the leaflet are maintained allowing the most natural response of the valvular cells to stimuli. The valves remain viable and are responsive to changing environmental conditions. This MTCS may provide advantages on studying questions including but not limited to, how does the 3D organization affect valvular biology, what factors affect 3D organization of the valve, and which network of signaling pathways regulates the 3D organization of the valve.

Here, we present an ex vivo flow model in which murine cardiac valves can be cultured allowing the study of the biology of the valve.

Heart valve disease is a major burden in the Western world and no effective treatment is available. This is mainly due to a lack of knowledge of the ...

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

TAPE: A Biodegradable Hemostatic Glue Inspired by a Ubiquitous Compound in Plants for Surgical Application

This video describes the simplest protocol for preparing biodegradable surgical glue that has an effective hemostatic ability and greater water-resistant adhesion strength than commercial tissue adhesives. Medical adhesives have attracted great attention as potential alternative tools to sutures and staples due to their convenience in usage with minimal invasiveness. Although there are several protocols for developing tissue adhesives including those commercially available such as fibrin glues and cyanoacrylate-based materials, mostly they require a series of chemical syntheses of organic molecules, or complicated protein-purification methods, in the case of bio-driven materials (i.e., fibrin glue). Also, the development of surgical glues exhibiting high adhesive properties while maintaining biodegradability is still a challenge due to difficulties in achieving good performance in the wet environment of the body. We illustrate a new method to prepare a medical glue, known as TAPE, by the weight-based separation of a water-immiscible supramolecular aggregate formed after a physical mixing of a plant-derived, wet-resistant adhesive molecule,&#160;Tannic Acid (TA), and a well-known biopolymer, Poly(Ethylene) glycol (PEG). With our approach, TAPE shows high adhesion strength, which is 2.5-fold more than commercial fibrin glue in the presence of water. Furthermore, TAPE is biodegradable in physiological conditions and can be used as a potent hemostatic glue against tissue bleeding. We expect the widespread use of TAPE in a variety of medical settings and drug delivery applications, such as polymers for muco-adhesion, drug depots, and others.

We describe the simplest protocol to prepare biodegradable medical glue that has an effective hemostatic ability. TAPE is a water-immiscible supramolecular aggregate prepared by mixing of tannic acid, a ubiquitous compound found in plants, and poly(ethylene) glycol, yielding a 2.5 times greater water-resistant adhesion compared with commercial fibrin glue.

This video describes the simplest protocol for preparing biodegradable surgical glue that has an effective hemostatic ability and greater water-resistant ...

Co-culture of Living Microbiome with Microengineered Human Intestinal Villi in a Gut-on-a-Chip Microfluidic Device

Here, we describe a protocol to perform long-term co-culture of multi-species human gut microbiome with microengineered intestinal villi in a human gut-on-a-chip microphysiological device. We recapitulate the intestinal lumen-capillary tissue interface in a microfluidic device, where physiological mechanical deformations and fluid shear flow are constantly applied to mimic peristalsis. In the lumen microchannel, human intestinal epithelial Caco-2 cells are cultured to form a &#39;germ-free&#39; villus epithelium and regenerate small intestinal villi. Pre-cultured microbial cells are inoculated into the lumen side to establish a host-microbe ecosystem. After microbial cells adhere to the apical surface of the villi, fluid flow and mechanical deformations are resumed to produce a steady-state microenvironment in which fresh culture medium is constantly supplied and unbound bacteria (as well as bacterial wastes) are continuously removed. After extended co-culture from days to weeks, multiple microcolonies are found to be randomly located between the villi, and both microbial and epithelial cells remain viable and functional for at least one week in culture. Our co-culture protocol can be adapted to provide a versatile platform for other host-microbiome ecosystems that can be found in various human organs, which may facilitate in vitro study of the role of human microbiome in orchestrating health and disease.

We describe an in vitro protocol to co-culture gut microbiome and intestinal villi for an extended period using a human gut-on-a-chip microphysiological system.

Here, we describe a protocol to perform long-term co-culture of multi-species human gut microbiome with microengineered intestinal villi in a human ...

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and dampen loads in the spine. The IVD consists of a proteoglycan-rich nucleus pulposus (NP) and a collagen-rich annulus fibrosis (AF) sandwiched by cartilaginous end-plates. Together with the adjacent vertebrae, the vertebrae-IVD structure forms a functional spine unit (FSU). These microstructures contain unique cell types as well as unique extracellular matrices. Whole organ culture of the FSU preserves the native extracellular matrix, cell differentiation phenotypes, and cellular-matrix interactions. Thus, organ culture techniques are particularly useful for investigating the complex biological mechanisms of the IVD. Here, we describe a high-throughput approach for culturing whole lumbar mouse FSUs that provides an ideal platform for studying disease mechanisms and therapies for the IVD. Furthermore, we describe several applications that utilize this organ culture method to conduct further studies including contrast-enhanced microCT imaging and three-dimensional high-resolution finite element modeling of the IVD.

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Whole organ culture of the intervertebral disc (IVD) preserves the native extracellular matrix, cell phenotypes, and cellular-matrix interactions. Here we describe an IVD culture system using mouse lumbar and caudal IVDs in their functional spinal units and several applications utilizing this system.

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and ...

Melt Electrospinning Writing of Three-dimensional Poly(&#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

Melt Electrospinning Writing of Three-dimensional Poly(&amp;#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This protocol serves as a comprehensive guideline to fabricate scaffolds via electrospinning with polymer melts in a direct writing mode. We systematically outline the process and define the appropriate parameter settings for achieving targeted scaffold architectures.

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology ...

Creating a Structurally Realistic Finite Element Geometric Model of a Cardiomyocyte to Study the Role of Cellular Architecture in Cardiomyocyte Systems Biology

With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal microscopy, the scientific community has unprecedented access to large datasets at sub-micrometer resolution that characterize the architectural remodeling that accompanies changes in cardiomyocyte function in health and disease. However, these datasets have been under-utilized for&#160;investigating the role of cellular architecture remodeling in cardiomyocyte function. The purpose of this protocol is to outline how to create an accurate finite element model of a cardiomyocyte using high resolution electron microscopy and confocal microscopy images. A detailed and accurate model of cellular architecture has significant potential to provide new insights into cardiomyocyte biology, more than experiments alone can garner. The power of this method lies in its ability to computationally fuse information from two disparate imaging modalities of cardiomyocyte ultrastructure to develop one unified and detailed model of the cardiomyocyte. This protocol outlines steps to integrate electron tomography and confocal microscopy images of adult male Wistar (name for a specific breed of albino rat) rat cardiomyocytes to develop a half-sarcomere finite element model of the cardiomyocyte. The procedure generates a 3D finite element model that contains an accurate, high-resolution depiction (on the order of ~35 nm) of the distribution of mitochondria, myofibrils and ryanodine receptor clusters that release the necessary calcium for cardiomyocyte contraction from the sarcoplasmic reticular network (SR) into the myofibril and cytosolic compartment. The model generated here as an illustration does not incorporate details of the transverse-tubule architecture or the sarcoplasmic reticular network and is therefore a minimal model of the cardiomyocyte. Nevertheless, the model can already be applied in simulation-based investigations into the role of cell structure in calcium signaling and mitochondrial bioenergetics, which is illustrated and discussed using two case studies that are presented following the detailed protocol.

This protocol outlines a novel method to create a spatially detailed finite element model of the intracellular architecture of cardiomyocytes from electron microscopy and confocal microscopy images. The power of this spatially detailed model is demonstrated using case studies in calcium signaling and bioenergetics.

With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal ...

Bioparticle Microarrays for Chemotactic and Molecular Analysis of Human Neutrophil Swarming in vitro

Neutrophil swarming is a cooperative process by which neutrophils seal off a site of infection and promote tissue reorganization. Swarming has classically been studied in vivo in animal models showing characteristic patterns of cell migration. However, in vivo models have several limitations, including intercellular mediators that are difficult to access and analyze, as well as the inability to directly analyze human neutrophils. Because of these limitations, there is a need for an in vitro platform that studies swarming with human neutrophils and provides easy access to the molecular signals generated during swarming. Here, a multistep microstamping process is used to generate a bioparticle microarray that stimulates swarming by mimicking an in vivo infection. The bioparticle microarray induces neutrophils to swarm in a controlled and stable manner. On the microarray, neutrophils increase in speed and form stable swarms around bioparticle clusters. Additionally, supernatant generated by the neutrophils was analyzed and 16 proteins were discovered to have been differentially expressed over the course of swarming. This in vitro swarming platform facilitates direct analysis of neutrophil migration and protein release in a reproducible, spatially controlled manner.

This protocol generates bioparticle microarrays that provide spatially controlled neutrophil swarming. It provides easy access to the mediators that neutrophils release during migration and allows for quantitative imaging analysis.

Neutrophil swarming is a cooperative process by which neutrophils seal off a site of infection and promote tissue reorganization. Swarming has classically ...