This work was supported by National Institutes of Health (NIH) grants R01-DK080752 and P50-DK064540. We thank J. Loughman for her efforts in establishing this assay.

1. Culturing 5637 Bladder Epithelial Cells
Perform the following steps in a laminar flow tissue-culture hood prepared with UV irradiation and wiped down with 70% ethanol.
<ol>
	<li>Prepare RPMI-1640 medium containing 10% fetal bovine serum (FBS) [termed RPMI+], filter sterilize using a 0.22 &#181;m pore size filter, and warm to 37 &#176;C in a water bath.</li>
	<li>Thaw a cryovial of 5637 cells (American Type Culture Collection HTB-9; derived from bladder carcinoma) in a 37 &#176;C water bat...

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attenuation+of+human+neutrophil+migration+and+function+by+uropathogenic+bacteria.">Attenuation of human neutrophil migration and function by uropathogenic bacteria.</a> Microbes Infect. 13, 555-565 (2011).</li><li>Lau, M. E., Loughman, J. A., Hunstad, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=YbcL+of+uropathogenic+Escherichia+coli+suppresses+transepithelial+neutrophil+migration.">YbcL of uropathogenic Escherichia coli suppresses transepithelial neutrophil migration.</a> Infect. Immun. 80, 4123-4132 (2012).</li><li>Loughman, J. A., Hunstad, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+indoleamine+2,3-dioxygenase+by+uropathogenic+bacteria+attenuates+innate+responses+to+epithelial+infection.">Induction of indoleamine 2,3-dioxygenase by uropathogenic bacteria attenuates innate responses to epithelial infection.</a> J. Infect. Dis. 205, 1830-1839 (2012).</li><li>Foxman, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+epidemiology+of+urinary+tract+infection.">The epidemiology of urinary tract infection.</a> Nat. Rev. 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Using a cultured bladder epithelial cell line and freshly isolated human PMN, we established an in vitro model of transuroepithelial neutrophil migration. This model has been instrumental in beginning to dissect the complexities of the innate immune response during urinary tract infection (UTI), an extremely common bacterial infection typically caused by UPEC9. During infection of the bladder, or cystitis, recruitment of PMN to the bladder lumen is essential for bacterial clearance10. To es...

The movement of cells throughout the body, often across long distances, is required for growth and development, wound healing, and immune response. Cell migration is complex and requires the coordination of many different processes, including signaling cascades and the rearrangement of cytoskeletal components. Cells can move randomly (chemokinesis) as well as toward defined chemical gradients (chemotaxis). Many techniques have been developed to study cell migration in vitro. The oldest and most common technique, the Boyden chamber, consists of a vertical two-chamber system where a chemoattractant substance is placed in the bottom chamber and cells of interest are placed in the top chamber1. The movement of cells across the permeable filter, with pores of defined size, separating the two chambers is monitored. Additional techniques have been developed to investigate cell migration, including the Zigmond chamber2 and the Dunn chamber3. These collective approaches have yielded significant insight into the movement of many different cell types.
In addition to interrogating the basic principles of chemokinesis and chemotaxis, two-chamber assays have facilitated the investigation of cell migration through extracellular matrix components and both endothelial and epithelial cell layers. An advantage of two-chamber systems over other techniques is that the porous membrane can be coated with proteins such as collagen or fibrinogen, and cell migration across an extracellular matrix-like barrier can be assessed. Additionally, cultured cell lines can be grown and differentiated on the permeable supports. To investigate the movement of cells across an endothelial barrier, cultured endothelial cells are seeded and grown in the upper reservoir of the permeable supports. Motile cells, such as immune cells, are added to the upper reservoir and migration into the lower reservoir across the endothelial barrier in the physiologic apical-to-basolateral direction is observed. This model has been invaluable in understanding extravasation of immune cells out of the blood stream. In contrast to transendothelial migration, the movement of cells across an epithelial barrier typically occurs in the basolateral-to-apical direction. In order to model these events in vitro, researchers seed and grow cultured epithelial cells on the underside of the permeable supports. Motile cells are added to the upper reservoir and migration across the epithelial barrier, representing the basolateral-to-apical direction, is monitored. Such models of transepithelial migration have significantly contributed to our understanding of inflammatory responses at mucosal surfaces, particularly those of the lung and gut4,5.
In contrast, immune cell trafficking through the epithelium of the urinary tract has received much less attention. To further our understanding of innate immune responses in the urinary tract during infection with uropathogenic Escherichia coli (UPEC), we developed an in vitro assay, the transuroepithelial neutrophil migration assay, that enables investigation of polymorphonuclear leukocyte (PMN; neutrophil) movement across a bladder epithelial barrier 6-8. As with other two-chamber models of transepithelial migration, cultured human bladder epithelial cells are grown on the underside of a permeable support and form confluent epithelial layers. Human neutrophils, isolated from venous blood, are applied to the basolateral side of the epithelial layer, and migration across the epithelium in the physiologically relevant basolateral-to-apical direction is quantified in response to infection with different strains of E. coli or the presence of chemoattractant molecules. Much research had focused on neutrophil movement, both chemokinesis and chemotaxis, in the absence of additional cell types. The transuroepithelial neutrophil migration assay is advantageous as it takes into account complex interactions between bladder epithelial cells and immune cells during infection. This tractable in vitro model has the potential to permit the detailed investigation of immune responses at uroepithelial surfaces.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>Transwell Inserts (i.e.&#160;permeable supports)</td>
			<td>Corning</td>
			<td>3472</td>
			<td>6.5 mm, 3 &#956;m pore, polyester membrane insert</td>
		</tr>
		<tr>
			<td>BD Vacutainer Blood Collection Tubes</td>
			<td>Becton, Dickinson and Company (BD)</td>
			<td>366480</td>
			<td>16 mm x 100 mm x 10 ml green cap tubes containing sodium heparin</td>
		</tr>
		<tr>
			<td>BD Safety-Lok Blood Collection and Infusion Set</td>
			<td>Becton, Dickinson and Company (BD)</td>
			<td>367281</td>
			<td>21 G x 0.75 in needle x 12 in tubing</td>
		</tr>
		<tr>
			<td>BD Vacutainer one-use, nonstackable holder</td>
			<td>Becton, Dickinson and Company (BD)</td>
			<td>364815</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran</td>
			<td>Sigma-Aldrich</td>
			<td>D4876</td>
			<td>From Leuconostoc mesenteroides</td>
		</tr>
		<tr>
			<td>Ficoll-Paque PLUS density centrifugation solution</td>
			<td>GE Healthcare</td>
			<td>17-1440-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra-Low Attachment Plates</td>
			<td>Corning</td>
			<td>3473</td>
			<td>24-well, clear flat bottom</td>
		</tr>
		<tr>
			<td>N-Formyl-Met-Leu-Phe (fMLF)</td>
			<td>Sigma-Aldrich</td>
			<td>F3506</td>
			<td>Reconstituted in DMSO to 10 mM</td>
		</tr>
		<tr>
			<td>Recombinant Human CXCL8/IL-8</td>
			<td>R&#38;D Systems</td>
			<td>208-IL</td>
			<td>Reconstituted in PBS to 100 &#956;g/ml</td>
		</tr>
	</tbody>
</table>

quantitative assessment of human neutrophil migration across a cultured bladder epithelium

The recruitment of immune cells from the periphery to the site of inflammation is an essential step in the innate immune response at any mucosal surface. During infection of the urinary bladder, polymorphonuclear leukocytes (PMN; neutrophils) migrate from the bloodstream and traverse the bladder epithelium. Failure to resolve infection in the absence of a neutrophilic response demonstrates the importance of PMN in bladder defense. To facilitate colonization of the bladder epithelium, uropathogenic Escherichia coli (UPEC), the causative agent of the majority of urinary tract infections (UTIs), dampen the acute inflammatory response using a variety of partially defined mechanisms. To further investigate the interplay between host and bacterial pathogen, we developed an in vitro model of this aspect of the innate immune response to UPEC. In the transuroepithelial neutrophil migration assay, a variation on the Boyden chamber, cultured bladder epithelial cells are grown to confluence on the underside of a permeable support. PMN are isolated from human venous blood and are applied to the basolateral side of the bladder epithelial cell layers. PMN migration representing the physiologically relevant basolateral-to-apical direction in response to bacterial infection or chemoattractant molecules is enumerated using a hemocytometer. This model can be used to investigate interactions between UPEC and eukaryotic cells as well as to interrogate the molecular requirements for the traversal of bladder epithelia by PMN. The transuroepithelial neutrophil migration model will further our understanding of the initial inflammatory response to UPEC in the bladder.

The transuroepithelial neutrophil migration assay enables the quantitative assessment of human PMN migration across cultured bladder epithelial cell layers in response to various stimuli (Figure 1B). While the protocol is straightforward, there are a number of variables that can influence PMN migration and consequently affect the reproducibility of this assay. Measures should be taken while preparing the permeable supports and the PMN to reduce variability between technical and biological replicates. For...

Watch this Scientific Journal Video about Quantitative Assessment of Human Neutrophil Migration Across a Cultured Bladder Epithelium at JoVE.com

Quantitative Assessment of Human Neutrophil Migration Across a Cultured Bladder Epithelium

We developed an in vitro model that mimics an important component of the acute inflammatory response during infection of the bladder with uropathogenic Escherichia coli. The transuroepithelial neutrophil migration assay enables quantitative assessment of human neutrophil migration across bladder epithelia, cultured on permeable supports, in response to bacterial infection or chemoattractant substances.

The recruitment of immune cells from the periphery to the site of inflammation is an essential step in the innate immune response at any mucosal surface. ...

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Immunology and Infection

14.9K Views.  Washington University School of Medicine. We developed an in vitro model that mimics an important component of the acute inflammatory response during infection of the bladder with uropathogenic Escherichia coli. The transuroepithelial neutrophil migration assay enables quantitative assessment of human neutrophil migration across bladder epithelia, cultured on permeable supports, in response to bacterial infection or chemoattractant substances.