Name: the mesenteric lymph duct cannulated rat model: application to the assessment of intestinal lymphatic drug transport
Uploaded: 2015-03-06T13:00:00
Description: Watch this Scientific Journal Video about The Mesenteric Lymph Duct Cannulated Rat Model: Application to the Assessment of Intestinal Lymphatic Drug Transport at JoVE.com

Funding from the Australian Research Council (ARC) and National Health and Medical Research Council (NHMRC) is gratefully acknowledged.

The studies described in this manuscript were approved by the local animal ethics committee and were conducted in accordance with the Australian and New Zealand Council for the Care of Animals in Research and Teaching guidelines. Prior to beginning any animal procedure, ensure that the appropriate permission is obtained through the local institution/organization. As with all animal surgeries, ensure that the surgery is performed by appropriately trained operators, under aseptic conditions and that anesthetics, analgesics...

The rat mesenteric lymph cannulation model enables direct quantification of the concentration and rate of transport of various cells and molecules (such as lipids and drugs) from the intestine into the lymph and the changes to these that occur in response to challenge of various substances (diet, antigen, drugs, formulations, etc.)10,27 and disease (cancer, viruses, colitis, insulin resistance, etc.)5-7. The components collected in lymph may also be further used in additional exper...

Lymph flows from the small intestine via a unidirectional process that originates at single lacteals that are contained within each small intestinal villi1. Lacteals are relatively permeable to fluid, macromolecules and cells and lymph formation thus commences with the entry of these factors into lacteals. The initial lymph in the lacteals subsequently flows from the intestine via a network of lymphatic microvessels, collecting (afferent) lymphatic vessels, a series of mesenteric lymph nodes and ultimately the post-nodal (efferent) lymph vessels. Within the nodes, lymph passes through a series of medullary sinuses where exchange occurs with node resident immune cells as well as material entering the node from the blood. All lymph flowing from the small intestine eventually converges into the efferent superior mesenteric lymph duct and subsequently the cisterna chyli. The cisterna chyli also collects lymph draining the caudal peripheral tissues, intestinal, hepatic and lumbar regions and joins the thoracic lymph duct together with lymph from the mediastinum and cranial parts of the body. The thoracic lymph duct empties lymph directly into the venous system at the junction of the left internal jugular and subclavian veins. The protocol described here, which enables the collection of lymph directly from the superior mesenteric lymph duct, thus facilitates the analysis of various factors transiting directly from the intestine to the systemic (general) circulation via the intestinal lymphatic system.
The major physiological functions assigned to the intestinal lymphatic system are to maintain fluid balance, to facilitate lipid and lipophilic molecule absorption, and to enable appropriate immune responses1. Tumor cells and viruses also propagate via the intestinal lymphatics2-4 and key changes occur within the lymphatics in several inflammatory and metabolic pathologies5-7. Cannulation of the mesenteric lymph duct to collect lymph within the mesentery enables an analysis of bulk fluid flow via the intestinal lymphatics as well as quantification of the concentration and transport rate of various cells and molecules. Changes to the concentration or transit of these factors in response to various challenges (e.g., diets, antigens, drugs) and in disease models (e.g., colitis, HIV, diabetes) can also be assessed. Whilst it is impossible to extensively describe each lymph component which may be analysed and compared here, mesenteric lymph simplistically consists of aqueous, lipid and cellular phases. Components of interest in the aqueous phase include peptides and proteins such as antigens or tolerogens8, immune messengers such as cytokines and mast cell mediators9, and metabolic mediators such as incretins10. The cellular fraction of the post-nodal mesenteric lymph consists almost entirely (over 99%) of lymphocytes11. Various immune cells (dendritic cells, mast cells, etc.) enter the pre-nodal mesenteric lymphatics but remain within the node12. If the cells within afferent lymph are of interest, it is possible to collect these cells via removal of the mesenteric lymph nodes several days before cannulation of the mesenteric lymph duct12. In this way the afferent and efferent lymph ducts are directly connected and the lymph cells in afferent lymph pass directly into the mesenteric lymph duct. The transit and phenotype of various immune cells passing through the intestinal lymphatics can thus be examined. Perhaps the most common reason cited for collecting mesenteric lymph to date, however, is to study the intestinal processing, absorption and transport of dietary lipids and lipophilic molecules10.
Following ingestion, dietary lipids are digested (for example, from triglyceride to fatty acids and monoglyceride, phospholipid to fatty acids and lysophospholipid, and cholesterol ester to fatty acid and cholesterol, etc.) and dispersed within the intestinal lumen into small micelle and vesicular structures via the addition of amphiphiles from bile (phospholipids, cholesterol and bile salts) and the action of pancreatic enzymes10,13. From here they are absorbed into enterocytes. A proportion of the absorbed components are re-esterified to form triglycerides, phospholipids and cholesterol esters within the absorptive cells (enterocytes). These re-esterified lipids are assembled from a combination of exogenously ingested lipid components and endogenous lipid components from the secreted bile, mucosal lipid pools or the intestinal blood supply13. From here the esterified lipids are either stored within enterocytes or assembled into intestinal lipoproteins (chylomicrons, very low density lipoproteins (VLDL)) together with various apoproteins and other lipophilic molecules (e.g., vitamins)10,13. After exiting enterocytes, lipoproteins are specifically transported from the intestine to the systemic circulation via the mesenteric lymphatic system as the intestinal lacteals are more permeable to their entry than the intestinal blood capillaries. A proportion of absorbed lipid components are also transported from the intestine to the systemic circulation via the blood capillaries and portal vein as single, non-lipoprotein associated, molecules14 . In general, however, the portal vein transport route is only a significant player in the absorption of short and medium chain length lipids.
The collection of mesenteric lymph thus enables the assessment of the transport of lipoproteins and associated components (lipids, lipophilic molecules, apo-proteins) from the intestine. The lipoproteins can be quantitated and characterized with the advantage that mesenteric lymph lipoproteins, in general, are in a nascent state since they have not been extensively modified by systemic enzymes such as lipoprotein lipase15. Whilst the mesenteric lymph cannulated rat model has perhaps historically been most extensively described for the analysis of lipid/lipoprotein transport from the intestine, an area of expanding interest is the role of lymphatics in the transport of lipophilic drugs, prodrugs and other xenobiotics13,16 which is the focus of the model described here. Lipophilic drugs (generally those with log P &#62; 5 and solubility in long-chain triglyceride &#62; 50 mg/g although exceptions are apparent)17,18, prodrugs19 and other xenobiotics13,16 can gain access to the intestinal lymphatics either passively or by actively integrating into intestinal lipoprotein transport pathways19.
The rat mesenteric lymph cannulation technique thus has many applications. Bollman et al. first described a technique to cannulate the mesenteric lymph duct in rats in 194820. Since then a number of variations on the model have been described. For example, collection can occur when the rat is anaesthetized with various anesthetics21,22, or in the conscious state whilst restrained15 or freely moving23,24. Rats can be administered different rehydration solutions and other substances such as lipids and drug formulations at different rates into the stomach, intestine or parenterally (typically 0 - 5 ml/hr)25. In some studies the thoracic lymph duct rather than mesenteric lymph duct is cannulated to estimate transport from the intestine via the lymphatics although this may overestimate transit from the small intestine, depending on the factor of interest, as the thoracic lymph duct also receives lymph from other regions22,26. Lymph cannulation models have also been described in several other species including mice15,27, mini-pigs12, sheep28,29, pigs30 and dogs31. However, the rat model is the most widely and consistently cited. Detailed protocols for cannulation of the mesenteric lymph duct followed by collection of lymph in conscious25 or anaesthetized22 rats and mice15,27 have been published previously and the interested reader is directed to these protocols. This protocol is the first to demonstrate the technique in a visualized format.
The lymph cannulated rat model has advantages over larger animal models in terms of expense, the ease of the surgery and ethical considerations. When compared to the mouse model, mesenteric lymph cannulation surgery is also easier in the rat although the mouse model enables more detailed studies in transgenic animals27. Nonetheless, there are some limitations of the rat model, particularly those associated with differences in physiology, that limit extrapolation to other pre-clinical and clinical situations. For example, in the rat bile flow is constant and independent of food intake whereas in higher species food or lipids stimulate bile flow32. This creates challenges to obtaining representative pre- and post-prandial environments in the rat that reflect what is seen in larger species and humans. For drug delivery studies, larger species may also be preferred when assessing lymphatic transport after the administration of realistic human dosage forms25. In a recent study, lipid transport rates in the mesenteric lymph were found to be comparable across species (mouse, rat, dog) after administration of an equivalent mass and type of lipid which provides some confidence in extrapolating lipid transport data across species27. However, the transport of a model lipophilic drug, halofantrine, ranked in the order of animal size (i.e., dog &#62; rat &#62; mouse). A scaling factor may thus be required to extrapolate lymphatic drug transport data from rat to other species.
A limitation of lymph cannulation models, in general, is that passive lymph collection directly from a lymphatic duct may modify lymph flow and transport since lymph vessels work against a pressure gradient that is altered once the vessel is cannulated33. The lymph cannulation model can also be difficult to establish in laboratories that are unfamiliar with the technique. Alternate models have thus been described. For instance, the transit of factors via the intestinal lymphatic system, such as lipoproteins and lipophilic molecules, has been indirectly studied via collection of blood. One such model involves comparing blood concentrations of lipids and/or drugs following oral administration in the presence and absence of inhibitors (e.g., colchicine, Pluronic L81, cycloheximide) of intestinal lipoprotein production that block lymphatic transport34. An advantage of models that quantify lymphatic transport indirectly via collection of blood samples is that it enables some evaluation of lymphatic transport in humans as invasive surgery is not required35. However, inhibitors of lymphatic transport are not specific and factors that are transported via the lymphatics are diluted and modified in the systemic circulation which complicates such assessments. In vitro alternatives have also been described. For example, caco-2 cell or isolated enterocyte cultures have been utilized to study in more detail the intestinal secretion of molecules that enter the lymphatics36-38. An advanced in vitro model that is more representative of the human intestinal microenvironment was also recently described39. In this model a lymphatic endothelial cell layer is co-cultured with Caco-2 cells which enables more detailed analysis of the transfer of substances from the intestine into the lymphatics. However, in vitro cell systems lack exchange flow and transfer ie interconnection with an intestinal lumen and underlying blood and lymphatic vascular supply. In an alternate approach, Kassis et al. established a dual-channel (high-speed bright-field video and fluorescence) in situ imaging system which enables quantitative comparisons between vessel contraction, lymph flow and fluorescent lipid concentrations in mesenteric lymphatic vessels33. An advantage of this model over the aforementioned in vitro systems is that it enables accurate tracking of the passage of immune cells through the lymphatics. Absolute measurements of mass lipid (or drug) transport are, however, not yet established using imaging methods. In vitro and in silico approaches to specifically predict the extent of lipophilic drug transport via the intestinal lymphatics have also been published40-42. For example, the ex vivo affinity of several compounds for plasma chylomicrons was found to correlate reasonably well with their lymphatic transport in vivo41. Subsequently, the same group established an in silico model to predict drug affinity for chylomicrons based on multiple physicochemical properties40. Holm et al. also established a relatively complex in silico model to outright predict lymphatic transport of lipophilic compounds on the basis of molecular descriptors42. These models may provide a useful approach to predict the extent of lymphatic transport of unknown drugs. Validation of the models with a wide range of drugs and across different labs will, however, be required to confirm their accuracy and reproducibility.
Cannulation of the mesenteric lymph duct thus remains the only means to directly examine the content of lymph draining the small intestine and the transit rate of the complex array of factors (cells, proteins, peptides, lipids, drugs) in lymph in an in vivo situation. Herein we describe a protocol for cannulation of the mesenteric lymph duct and carotid artery that enables the collection of mesenteric lymph and systemic blood from anaesthetized rats. Representative data demonstrate how the model can be used to examine lipid and drug transport from the intestine via the mesenteric lymphatic system. This is followed by a discussion of difficulties that can be encountered in establishing the model and a troubleshooting guide. Once established the model is a powerful tool to investigate intestinal lymphatic transport.

<table border="0" cellpadding="0" cellspacing="0" >
	<tbody>
		<tr >
			<td >Sterile saline</td>
			<td>Baxter healthcare</td>
			<td>AHB 1307</td>
			<td>Any brand can be used. Example here is Baxter 100 ml saline bags, box of 50</td>
		</tr>
		<tr >
			<td >70 % ethanol in water</td>
			<td>Any</td>
			<td></td>
			<td>Any brand can be used</td>
		</tr>
		<tr >
			<td >Chlorhexidine gluconate solution (Microshield 4)</td>
			<td>Livingstone International</td>
			<td>JJ60243L</td>
			<td>Any brand can be used. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=JJ60243L</td>
		</tr>
		<tr >
			<td >Betadine solution</td>
			<td>Livingstone International</td>
			<td>BU0510</td>
			<td>Any brand can be used. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=BU0510</td>
		</tr>
		<tr >
			<td >Ilium Ketamil (Ketamine 100 mg/ml)</td>
			<td >PROVET VICTORIA&#160;</td>
			<td >KETA I 1</td>
			<td>http://www.provet.com.au/</td>
		</tr>
		<tr >
			<td >Ilium Xylazil (Xylazine 100 mg/ml)</td>
			<td >PROVET VICTORIA&#160;</td>
			<td >TRO-3828</td>
			<td>http://www.provet.com.au/</td>
		</tr>
		<tr >
			<td >ACP 10 Injection (Acepromazine 10 mg/ml)</td>
			<td >PROVET VICTORIA&#160;</td>
			<td >VTG-DACP010020</td>
			<td>http://www.provet.com.au/</td>
		</tr>
		<tr >
			<td >Sodium pentobarbitone</td>
			<td>PROVET VICTORIA&#160;</td>
			<td>24529</td>
			<td>Any brand can be used. Example here is Lethabarb&#174; 325 mg/ml sodium pentobarbitone, Virbac Animal Health. http://www.provet.com.au</td>
		</tr>
		<tr >
			<td >Heparin (35000I.U. in 35 mL)</td>
			<td>Sigma Pharmaceuticals</td>
			<td>337220</td>
			<td>http://sigmaco.com.au/</td>
		</tr>
		<tr >
			<td >Ethylenediaminetetraacetic acid (EDTA) disodium salt dihydrate</td>
			<td >Sigma-Aldrich</td>
			<td >E1644</td>
			<td>Any brand can be used. Example here is disodium salt of EDTA from Sigma.&#160;</td>
		</tr>
		<tr >
			<td >Polyethylene (PE) cannula o.d. 0.96 mm x i.d. 0.58 mm</td>
			<td>Microtube extensions</td>
			<td>PE8050</td>
			<td>Any brand can be used. Example here is PE tubing 0.8x0.5 mm, 30 m</td>
		</tr>
		<tr >
			<td >Polyethylene (PE) cannula o.d. 0.8 mm x i.d. 0.5 mm</td>
			<td>Microtube extensions</td>
			<td>PE9658</td>
			<td>Any brand can be used. Example here is PE tubing 0.96x0.58 mm, 30 m</td>
		</tr>
		<tr >
			<td >Ruler</td>
			<td>Any</td>
			<td ></td>
			<td>Any brand can be used</td>
		</tr>
		<tr >
			<td >Markers</td>
			<td>Any</td>
			<td ></td>
			<td>Any brand can be used</td>
		</tr>
		<tr >
			<td >Cigarette lighter</td>
			<td>Any</td>
			<td ></td>
			<td>Any brand can be used</td>
		</tr>
		<tr >
			<td >Cyanoacrylate glue</td>
			<td>Any</td>
			<td ></td>
			<td>Any brand can be used</td>
		</tr>
		<tr >
			<td >23 gauge needles</td>
			<td>Livingstone International</td>
			<td>DN23GX0.75LV</td>
			<td>Any brand can be used. Example here is Livingstone Disposable Needle, Sterile, 23GX0.75inch, 100/BOX. http://www.livingstone.com.au/?PG=search_result&#38;CAT= 
			6&#38;search=DN23GX0.75LV</td>
		</tr>
		<tr >
			<td >25 gauge needles</td>
			<td>Livingstone International</td>
			<td>DN25GX1.0LV</td>
			<td>Any brand can be used. Example here is Livingstone Disposable Needle, Sterile, 25GX1.0inch, 100/BOX. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search= 
			DN25GX1.0LV</td>
		</tr>
		<tr >
			<td >1 ml syringe</td>
			<td>Livingstone International</td>
			<td>T3SS01TA</td>
			<td>Any brand can be used. Example here is Terumo syringe 1 ml Slip Tuberculin 100/Box. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=T3SS01TA</td>
		</tr>
		<tr >
			<td >10 ml syringe</td>
			<td>Livingstone International</td>
			<td>T3SS10SA</td>
			<td>Any brand can be used. Example here is Terumo syringe 10 ml Slip 100/Box. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=T3SS10SA</td>
		</tr>
		<tr >
			<td >Gauze swabs</td>
			<td>Livingstone International</td>
			<td>GSC075</td>
			<td>Any brand can be used and cut to required size. Example here is gauze swabs cotton filled 7.5x7.5 cm, 8 ply. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=GSC075</td>
		</tr>
		<tr >
			<td >Cotton buds</td>
			<td>Livingstone International</td>
			<td>CTAST075DP</td>
			<td>Any brand can be used. Example here is Livingstone cotton applicator plastic double tipped. 75MM. 100/PK. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=CTAST075DP</td>
		</tr>
		<tr >
			<td >Heating pad</td>
			<td>Ratek</td>
			<td>WT1</td>
			<td>Any brand that keeps temperature at 37C can be used. Example here is Ratek warming tray.</td>
		</tr>
		<tr >
			<td >Surgical light</td>
			<td>Harvard Apparatus</td>
			<td>72-0215 with 72-0267</td>
			<td>Any brand can be used. Example here is Harvard apparatus V-Lux 1000 Cold Light Source with Bifurcated Gooseneck Light Guide, Black, 4.7 mm fiber diameter (each arm). http://www.harvardapparatus.com/webapp/wcs/stores/servlet/product_11051_10001_50601_ 
			-1_HAI_ProductDetail and&#160; http://www.harvardapparatus.com/webapp/wcs/stores/servlet/product_11051_10001_35487_ 
			-1_HAI_ProductDetail___</td>
		</tr>
		<tr >
			<td >Surgical microscope</td>
			<td>Zeiss</td>
			<td>495005-0014-000</td>
			<td>Any brand can be used. Example here is Zeiss Stereomicroscope Stemi 2000-C with Stand S Double Spot and KL 300 LED. https://www.micro-shop.zeiss.com/?l=en&#38;p=us&#38;f=e&#38;i=10143</td>
		</tr>
		<tr >
			<td >Silk suture</td>
			<td>Livingstone International</td>
			<td>DTSK163019F4</td>
			<td>Any brand can be used. Example here is *&#160; 
			Email this item to my friend 
			3/8 Circle Reverse Cut Silk Suture 3/0 Thread 19mm. http://www.livingstone.com.au/?PG=search_result&#38;CAT=6&#38;search 
			=DTSK163019F4</td>
		</tr>
		<tr >
			<td >Scalpel blades</td>
			<td >Fine Science Tools (FST)</td>
			<td >10020-00</td>
			<td>Any brand can be used. Example here is FST Scalpel Blade #20. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=191</td>
		</tr>
		<tr >
			<td >Scalpel handle</td>
			<td >Fine Science Tools (FST)</td>
			<td>10004-13</td>
			<td>Any brand can be used. Example here is FST Scalpel Handle #4. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=298&#38;CategoryId=51</td>
		</tr>
		<tr >
			<td >1 x Small surgical scissors</td>
			<td >Fine Science Tools (FST)</td>
			<td>14060-09</td>
			<td>Any brand can be used. Example here is FST Fine Scissors, 9 cm with 21 mm cutting edge, sharp, straight. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=40&#38;CategoryId=17</td>
		</tr>
		<tr >
			<td >2 x Forceps with serrated curved tip</td>
			<td >Fine Science Tools (FST)</td>
			<td >11001-13</td>
			<td>Any brand can be used. Example here is FST 13 cm standard pattern forceps with curved 2.8x1.4 mm tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=405&#38;CategoryId=32</td>
		</tr>
		<tr >
			<td >1 x Iridectomy scissors</td>
			<td >Fine Science Tools (FST)</td>
			<td>15000-08</td>
			<td>Any brand can be used. Example here is FST Vannas Spring Scissors - 2.5mm Cutting Edge, Straight. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=17&#38;CategoryId=16&#160;</td>
		</tr>
		<tr >
			<td >1 x Forceps with straight serated tip</td>
			<td >Fine Science Tools (FST)</td>
			<td>11650-10</td>
			<td>Any brand can be used. Example here is FST Graefe 10 cm straight with serrated 1 x 0.99 mm tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=390&#38;CategoryId=32</td>
		</tr>
		<tr >
			<td >1 x Forceps with smooth sharp straight fine tip</td>
			<td >Fine Science Tools (FST)</td>
			<td>11251-10</td>
			<td>Any brand can be used. Example here is FST Dumont #5 forceps straight 11cm with 0.08 x 0.04mm tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=335&#38;CategoryId=29</td>
		</tr>
		<tr >
			<td >1 x Forceps with smooth fine curved forceps</td>
			<td >Fine Science Tools (FST)</td>
			<td>11063-07</td>
			<td>Any brand can be used. Example here is FST Delicate Forceps 9 cm with smooth 0.4 x 0.3mm tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=360</td>
		</tr>
		<tr >
			<td >2 x Hemostats</td>
			<td >Fine Science Tools (FST)</td>
			<td >13010-12</td>
			<td>Any brand can be used. Not all operators use the hemostats. Example here is FST 12 cm Micro-Mosquito Hemostats with 20 mm length x 1.3 mm width serrated, straight tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=377&#38;CategoryId=33</td>
		</tr>
		<tr >
			<td >1 x Suture needle holder</td>
			<td >Fine Science Tools (FST)</td>
			<td>12001-13</td>
			<td>Any brand can be used. Example here is FST 13cm Hasley Needle Holder with 16 mm length x 1.9 mm width tip. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=254&#38;CategoryId=70</td>
		</tr>
		<tr >
			<td >1 x Artery clamp</td>
			<td >Fine Science Tools (FST)</td>
			<td>18050-28</td>
			<td>Any brand can be used. Example here is FST Bulldog Serrefines straight, 28 mm long, 9x1.6 mm jaw dimension with medium clamp press. http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=270&#38;CategoryId=82</td>
		</tr>
		<tr >
			<td >Oleic acid</td>
			<td >Sigma Aldrich</td>
			<td >O1008</td>
			<td>When required, any brand can be used. Example here is 99% pure oleic acid. http://www.sigmaaldrich.com/catalog/product/sial/o1008?lang=en&#38;region=AU</td>
		</tr>
		<tr >
			<td >14C-oleic acid</td>
			<td >Perkin&#160;</td>
			<td>NEC317050UC&#160;</td>
			<td>Any brand can be used. Example here is Oleic Acid, [1-14C]-, 50&#181;Ci (1.85MBq). http://www.perkinelmer.com/Catalog/Product/ID/NEC317050UC</td>
		</tr>
		<tr >
			<td >Sodium taurocholate</td>
			<td >Sigma Aldrich</td>
			<td >T4009</td>
			<td>Any brand can be used. Example here is taurocholic acid sodium salt hydrate &#8805;95% (TLC) . http://www.sigmaaldrich.com/catalog/product/sigma/t4009?lang=en&#38;region=AU</td>
		</tr>
		<tr >
			<td >Halofantrine</td>
			<td >Glaxo Smith Kline</td>
			<td ></td>
			<td>Halofantrine was kindly provided as a gift from Glaxo Smith Kline</td>
		</tr>
		<tr >
			<td >Sodium phosphate monobasic</td>
			<td >Sigma Aldrich</td>
			<td >71507</td>
			<td >Any brand can be used. Example here is sodium phosphate monobasic monohydrate, BioXtra, for molecular biology, &#62;99.5%. http://www.sigmaaldrich.com/catalog/product/sigma/71643?lang=en&#38;region=AU</td>
		</tr>
		<tr >
			<td >Sodium phosphate dibasic</td>
			<td >Sigma Aldrich</td>
			<td >71643</td>
			<td >Any brand can be used. Example here is sodium phosphate dibasic dihydrate, BioUltra, for molecular biology, &#62;99%. http://www.sigmaaldrich.com/catalog/product/sigma/71507?lang=en&#38;region=AU</td>
		</tr>
	</tbody>
</table>

the mesenteric lymph duct cannulated rat model: application to the assessment of intestinal lymphatic drug transport

The intestinal lymphatic system plays key roles in fluid transport, lipid absorption and immune function. Lymph flows directly from the small intestine via a series of lymphatic vessels and nodes that converge at the superior mesenteric lymph duct. Cannulation of the mesenteric lymph duct thus enables the collection of mesenteric lymph flowing from the intestine. Mesenteric lymph consists of a cellular fraction of immune cells (99% lymphocytes), aqueous fraction (fluid, peptides and proteins such as cytokines and gut hormones) and lipoprotein fraction (lipids, lipophilic molecules and apo-proteins). The mesenteric lymph duct cannulation model can therefore be used to measure the concentration and rate of transport of a range of factors from the intestine via the lymphatic system. Changes to these factors in response to different challenges (e.g., diets, antigens, drugs) and in disease (e.g., inflammatory bowel disease, HIV, diabetes) can also be determined. An area of expanding interest is the role of lymphatic transport in the absorption of orally administered lipophilic drugs and prodrugs that associate with intestinal lipid absorption pathways. Here we describe, in detail, a mesenteric lymph duct cannulated rat model which enables evaluation of the rate and extent of lipid and drug transport via the lymphatic system for several hours following intestinal delivery. The method is easily adaptable to the measurement of other parameters in lymph. We provide detailed descriptions of the difficulties that may be encountered when establishing this complex surgical method, as well as representative data from failed and successful experiments to provide instruction on how to confirm experimental success and interpret the data obtained.

The results of a representative experiment to quantitate the cumulative extent and rate of lipid and drug transport via the lymphatic system following intestinal delivery using the mesenteric lymph cannulation model are shown in Figure 4 and Figure 5. In this experiment, 200 &#181;g of the model lipophilic drug halofantrine was administered into the duodenum of rats over 2 hr in a formulation containing 40 mg oleic acid (including 2 - 5 &#181;Ci 14C-oleic acid) and 7.1 mg 2-mo...

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The Mesenteric Lymph Duct Cannulated Rat Model: Application to the Assessment of Intestinal Lymphatic Drug Transport

Here we describe a technique to cannulate the mesenteric lymph duct in rats which enables quantification of lipid and drug transport via the lymphatic system following intestinal delivery. The technique can be adapted to assess mesenteric lymph concentrations and/or transport of fluid, immune cells, peptides, proteins and lipophilic molecules.

The intestinal lymphatic system plays key roles in fluid transport, lipid absorption and immune function. Lymph flows directly from the small intestine ...

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Research

JoVE Journal

Immunology and Infection

Intravital Microscopy of the Inguinal Lymph Node

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune response and therefore, the development of effector cells. As such, LNs are key to fighting invading pathogens and maintaining health. The choice of LN to study is dictated by accessibility and the desired model; the inguinal lymph node is well situated and easily supports studies of biologically relevant models of skin and genital mucosal infection.
The inguinal LN, like all LNs, has an extensive microvascular network supplying it with blood. In general, this microvascular network includes the main feed arteriole of the LN that subsequently branches and feeds high endothelial venules (HEVs). HEVs are specialized for facilitating the trafficking of immune cells into the LN during both homeostasis and infection. How HEVs regulate trafficking into the LN under both of these circumstances is an area of intense exploration. The LN feed arteriole, has direct upstream influence on the HEVs and is the main supply of nutrients and cell rich blood into the LN. Furthermore, changes in the feed arteriole are implicated in facilitating induction of adaptive immune response. The LN microvasculature has obvious importance in maintaining an optimal blood supply to the LN and regulating immune cell influx into the LN, which are crucial elements in proper LN function and subsequently immune response. 
The ability to study the LN microvasculature in vivo is key to elucidating how the immune system and the microvasculature interact and influence one another within the LN. Here, we present a method for in vivo imaging of the inguinal lymph node. We focus on imaging of the microvasculature of the LN, paying particular attention to methods that ensure the study of healthy vessels, the ability to maintain imaging of viable vessels over a number of hours, and quantification of vessel magnitude. Methods for perfusion of the microvasculature with vasoactive drugs as well as the potential to trace and quantify cellular traffic are also presented. 
Intravital microscopy of the inguinal LN allows direct evaluation of microvascular functionality and real-time interface of the direct interface between immune cells, the LN, and the microcirculation. This technique potential to be combined with many immunological techniques and fluorescent cell labelling as well as manipulated to study vasculature of other LNs.

A technique for performing intravital microscopy of the inguinal lymph node (LN) is outlined. Such technique allows for real-time, in vivo study of the lymph node microvasculature and structure both during homeostasis and infection. This technique can be adapted to cell trafficking studies and to other lymph node sites.

Lymph nodes (LN's), located throughout the body, are an integral component of the immune system. They serve as a site for induction of adaptive immune ...

Intravital Imaging of the Mouse Popliteal Lymph Node

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign antigens from peripheral tissues to prime the adaptive immune response. Juxtaposed between innate and adaptive immune responses, the LN is an ideal site to study immune cell interactions1,2. Lymphocytes (T cells, B cells and NK cells), dendritic cells (DCs), and macrophages comprise the bulk of bone marrow-derived cellular elements of the LN. These cells are strategically positioned in the LN to allow efficient surveillance of self antigens and potential foreign antigens3-5. The process by which lymphocytes successfully encounter cognate antigens is a subject of intense investigation in recent years, and involves an integration of molecular contacts including antigen receptors, adhesion molecules, chemokines, and stromal structures such as the fibro-reticular network2,6-12. 
Prior to the development of high-resolution real-time fluorescent in vivo imaging, investigators relied on static imaging, which only offers answers regarding morphology, position, and architecture. While these questions are fundamental in our understanding of immune cell behavior, the limitations intrinsic with this technique does not permit analysis to decipher lymphocyte trafficking and environmental clues that affect dynamic cell behavior. Recently, the development of intravital two-photon laser scanning microscopy (2P-LSM) has allowed investigators to view the dynamic movements and interactions of individual cells within live LNs in situ12-16. In particular, we and others have applied this technique to image cellular behavior and interactions within the popliteal LN, where its compact, dense nature offers the advantage of multiplex data acquisition over a large tissue area with diverse tissue sub-structures11,17-18. It is important to note that this technique offers added benefits over explanted tissue imaging techniques, which require disruption of blood, lymph flow, and ultimately the cellular dynamics of the system. Additionally, explanted tissues have a very limited window of time in which the tissue remains viable for imaging after explant. With proper hydration and monitoring of the animal's environmental conditions, the imaging time can be significantly extended with this intravital technique. Here, we present a detailed method of preparing mouse popliteal LN for the purpose of performing intravital imaging.

Recent advances in 2-photon microscopy have enabled real-time in situ imaging of live tissues in animal models, thereby enhancing our ability to investigate cellular behavior in both physiologic and pathologic conditions. Here, we outline the preparations required to perform intravital imaging of the mouse popliteal lymph node.

Lymph nodes (LNs) are secondary lymphoid organs, which are strategically located throughout the body to allow for trapping and presentation of foreign ...

Non-invasive Optical Imaging of the Lymphatic Vasculature of a Mouse

The lymphatic vascular system is an important component of the circulatory system that maintains fluid homeostasis, provides immune surveillance, and mediates fat absorption in the gut. Yet despite its critical function, there is comparatively little understanding of how the lymphatic system adapts to serve these functions in health and disease1. Recently, we have demonstrated the ability to dynamically image lymphatic architecture and lymph "pumping" action in normal human subjects as well as in persons suffering lymphatic dysfunction using trace administration of a near-infrared fluorescent (NIRF) dye and a custom, Gen III-intensified imaging system2-4. NIRF imaging showed dramatic changes in lymphatic architecture and function with human disease. It remains unclear how these changes occur and new animal models are being developed to elucidate their genetic and molecular basis. In this protocol, we present NIRF lymphatic, small animal imaging5,6 using indocyanine green (ICG), a dye that has been used for 50 years in humans7, and a NIRF dye-labeled cyclic albumin binding domain (cABD-IRDye800) peptide that preferentially binds mouse and human albumin8. Approximately 5.5 times brighter than ICG, cABD-IRDye800 has a similar lymphatic clearance profile and can be injected in smaller doses than ICG to achieve sufficient NIRF signals for imaging8. Because both cABD-IRDye800 and ICG bind to albumin in the interstitial space8, they both may depict active protein transport into and within the lymphatics. Intradermal (ID) injections (5-50 &mu;l) of ICG (645 &mu;M) or cABD-IRDye800 (200 &mu;M) in saline are administered to the dorsal aspect of each hind paw and/or the left and right side of the base of the tail of an isoflurane-anesthetized mouse. The resulting dye concentration in the animal is 83-1,250 &mu;g/kg for ICG or 113-1,700 &mu;g/kg for cABD-IRDye800. Immediately following injections, functional lymphatic imaging is conducted for up to 1 hr using a customized, small animal NIRF imaging system. Whole animal spatial resolution can depict fluorescent lymphatic vessels of 100 microns or less, and images of structures up to 3 cm in depth can be acquired9. Images are acquired using V++ software and analyzed using ImageJ or MATLAB software. During analysis, consecutive regions of interest (ROIs) encompassing the entire vessel diameter are drawn along a given lymph vessel. The dimensions for each ROI are kept constant for a given vessel and NIRF intensity is measured for each ROI to quantitatively assess "packets" of lymph moving through vessels.

Recently developed imaging techniques using near-infrared fluorescence (NIRF) may help elucidate the role the lymphatic system plays in cancer metastasis, immune response, wound repair, and other lymphatic-associated diseases.

The lymphatic  vascular system is an important component of the circulatory system that  maintains fluid homeostasis, provides immune surveillance, and ...

Generation of Lymph Node-fat Pad Chimeras for the Study of Lymph Node Stromal Cell Origin

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the mechanisms governing its formation. Lymph nodes are always encapsulated in adipose tissue and we recently demonstrated the importance of this relation for the formation of lymph node stroma. Adipocyte precursor cells migrate into the lymph node during its development and upon engagement of the Lymphotoxin-b receptor switch off adipogenesis and differentiate into lymphoid stromal cells (B&#233;n&#233;zech&#160;et al.14). Based on the lymphoid stroma potential of adipose tissue, we present a method using a lymph node/fat pad chimera that allows the lineage tracing of lymph node stromal cell precursors. We show how to isolate newborn lymph nodes and EYFP+ embryonic adipose tissue and make a LN/ EYFP+ fat pad chimera. After transfer under the kidney capsule of a host mouse, the lymph node incorporates local adipose tissue precursor cells and finishes its formation. Progeny analysis of EYFP+ fat pad cells in the resulting lymph nodes can be performed by flow-cytometric analysis of enzymatically digested lymph nodes or by immunofluorescence analysis of lymph nodes cryosections. By using fat pads from different knockout mouse models, this method will provide an efficient way of analyzing the origin of the different lymph node stromal cell populations.

Generation of lymph node/fat pad chimeras for the study of lymph node stromal cell origin is described. The method involves the isolation of lymph nodes from newborn mice and embryonic fat pads, the generation of chimeric lymph node-fat pads, and their transfer under the kidney capsule of a host mouse.

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the ...

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode larvae of the genus Trichinella. The most important sources of human infections worldwide are game meat and pork or pork products. In many countries, the prevention of human trichinellosis is based on the identification of infected animals by means of the artificial digestion of muscle samples from susceptible animal carcasses.
There are several methods based on the digestion of meat but the magnetic stirrer method is considered the gold standard. This method allows the detection of Trichinella larvae by microscopy after the enzymatic digestion of muscle samples and subsequent filtration and sedimentation steps. Although this method does not require special and expensive equipment, internal controls cannot be used. Therefore, stringent quality management should be applied throughout the test. The aim of the present work is to provide detailed handling instructions and critical control points of the method to analysts, based on the experience of the European Union Reference Laboratory for Parasites and the National Reference Laboratory of Germany for Trichinella.

Magnetic Stirrer Method for the Detection of Trichinella Larvae in Muscle Samples

The prevention of human trichinellosis in many countries worldwide is based on the laboratory examination of muscle samples from susceptible animals by methods of digestion, of which the magnetic stirrer method is considered the gold standard.

Trichinellosis is a debilitating disease in humans and is caused by the consumption of raw or undercooked meat of animals infected with the nematode ...

Quantitative Polymerase Chain Reaction-based Analyses of Murine Intestinal Microbiota After Oral Antibiotic Treatment

The gut microbiota has a central influence on human health. Microbial dysbiosis is associated with many common immunopathologies such as inflammatory bowel disease, asthma and arthritis. Thus, understanding the mechanisms underlying microbiota-immune system crosstalk is of crucial importance. Antibiotic administration, while aiding pathogen clearance, also induces drastic changes in the size and composition of intestinal bacterial communities which can have an impact on human health. Antibiotic treatment in mice recapitulates the impact and long-term changes in human microbiota from antibiotic treated patients, and enables investigation of the mechanistic links between changes in microbial communities and immune cell function. While several methods for antibiotic treatment of mice have been described, some of them induce severe dehydration and weight-loss complicating the interpretation of the data. Here, we provide two protocols for oral antibiotic administration which can be used for long-term treatment of mice without inducing major weight-loss. These protocols make use of a combination of antibiotics that target both Gram-positive and Gram-negative bacteria and can be provided either ad libitum in the drinking water or by oral gavage. Moreover, we describe a method for the quantification of microbial density in fecal samples by qPCR which can be used to validate the efficacy of the antibiotic treatment. The combination of these approaches provides a reliable methodology for the manipulation of the intestinal microbiota and the study of the effects of antibiotic treatment in mice.

Here we provide detailed protocols for the oral administration of antibiotics to mice, collection of fecal samples, DNA extraction and quantification of fecal bacteria by qPCR.

The gut microbiota has a central influence on human health. Microbial dysbiosis is associated with many common immunopathologies such as inflammatory ...

Chronic Salmonella Infection Induced Intestinal Fibrosis

Tissue fibrosis characterized by the pathological accumulation of extracellular matrix such as collagen is the outcome of persistent inflammation and dysregulated repair. In inflammatory bowel disease (IBD), fibrosis leads to recurrent stricture formations for which there is no effective therapy other than surgical resection. Due to its late onset, the processes that drive fibrosis is less studied and largely unknown. Therefore, fibrotic complications represent a major challenge in IBD. In this protocol, a robust in vivo model of intestinal fibrosis is described where streptomycin pre-treatment of C57Bl/6 mice followed by oral gavage with vaccine grade Salmonella Typhimurium &#916;AroA mutant leads to persistent pathogen colonization and fibrosis of the cecum. Methodologies for preparing S. Typhimurium &#916;AroA for inoculation, quantifying pathogen loads in the cecum and spleen, and evaluating collagen deposition in intestinal tissues are explained. This experimental disease model is useful for examining host factors that either enhance or exacerbate CD-like intestinal fibrosis.

This protocol describes a mouse model of Salmonella driven intestinal fibrosis that resembles key pathological hallmarks of Crohn&#8217;s disease including transmural inflammation and fibrosis. This method can be used to evaluate host factors that alter fibrotic outcomes using mutant mice maintained on a C57Bl/6 genetic background.

Tissue fibrosis characterized by the pathological accumulation of extracellular matrix such as collagen is the outcome of persistent inflammation and ...

Blocking Lymph Flow by Suturing Afferent Lymphatic Vessels in Mice

Lymphatic vessels are critical in maintaining tissue fluid balance and optimizing immune protection by transporting antigens, cytokines, and cells to draining lymph nodes (LNs). Interruption of lymph flow is an important method when studying the function of lymphatic vessels. The afferent lymphatic vessels from the murine footpad to the popliteal lymph nodes (pLNs) are well-defined as the only routes for lymph drainage into the pLNs. Suturing these afferent lymphatic vessels can selectively prevent lymph flow to the pLNs. This method allows for interference in lymph flow with minimal damage to the lymphatic endothelial cells in the draining pLN, the afferent lymphatic vessels, as well as other lymphatic vessels around the area. This method has been used to study how lymph impacts high endothelial venules (HEV) and chemokine expression in the LN, and how lymph flows through the adipose tissue surrounding the LN in the absence of functional lymphatic vessels. With the growing recognition of the importance of lymphatic function, this method will have broader applications to further unravel the function of lymphatic vessels in regulating the LN microenvironment and immune responses.

A protocol to block lymph flow by surgical suturing of afferent lymphatic vessels is presented.

Lymphatic vessels are critical in maintaining tissue fluid balance and optimizing immune protection by transporting antigens, cytokines, and cells to ...

Functional Assessment of Intestinal Permeability and Neutrophil Transepithelial Migration in Mice using a Standardized Intestinal Loop Model

The intestinal mucosa is lined by a single layer of epithelial cells that forms a dynamic barrier allowing paracellular transport of nutrients and water while preventing passage of luminal bacteria and exogenous substances. A breach of this layer results in increased permeability to luminal contents and recruitment of immune cells, both of which are hallmarks of pathologic states in the gut including inflammatory bowel disease (IBD). 
Mechanisms regulating epithelial barrier function and transepithelial migration (TEpM) of polymorphonuclear neutrophils (PMN) are incompletely understood due to the lack of experimental in vivo methods allowing quantitative analyses. Here, we describe a robust murine experimental model that employs an exteriorized intestinal segment of either ileum or proximal colon. The exteriorized intestinal loop (iLoop) is fully vascularized and offers physiological advantages over ex vivo chamber-based approaches commonly used to study permeability and PMN migration across epithelial cell monolayers.
We demonstrate two applications of this model in detail: (1) quantitative measurement of intestinal permeability through detection of fluorescence-labeled dextrans in serum after intraluminal injection, (2) quantitative assessment of migrated PMN across the intestinal epithelium into the gut lumen after intraluminal introduction of chemoattractants. We demonstrate feasibility of this model and provide results utilizing the iLoop in mice lacking the epithelial tight junction-associated protein JAM-A compared to controls. JAM-A has been shown to regulate epithelial barrier function as well as PMN TEpM during inflammatory responses. Our results using the iLoop confirm previous studies and highlight the importance of JAM-A in regulation of intestinal permeability and PMN TEpM in vivo during homeostasis and disease. 
The iLoop model provides a highly standardized method for reproducible in vivo studies of intestinal homeostasis and inflammation and will significantly enhance understanding of intestinal barrier function and mucosal inflammation in diseases such as IBD.

Dysregulated intestinal epithelial barrier function and immune responses are hallmarks of inflammatory bowel disease that remain poorly investigated due to a lack of physiological models. Here, we describe a mouse intestinal loop model that employs a well-vascularized and exteriorized bowel segment to study mucosal permeability and leukocyte recruitment in vivo.

The intestinal mucosa is lined by a single layer of epithelial cells that forms a dynamic barrier allowing paracellular transport of nutrients and water ...

Canine Intestinal Organoids in a Dual-Chamber Permeable Support System

The permeable support system is typically used in conjunction with traditional two-dimensional (2D) cell lines as an in vitro tool for evaluating the oral permeability of new therapeutic drug candidates. However, the use of these conventional cell lines has limitations, such as altered expression of tight junctions, partial cell differentiation, and the absence of key nuclear receptors. Despite these shortcomings, the Caco-2 and MDCK models are widely accepted and validated for the prediction of human in vivo oral permeability.
Dogs are a relevant translational model for biomedical research due to their similarities in gastrointestinal anatomy and intestinal microflora with humans. Accordingly, and in support of parallel drug development, the elaboration of an efficient and accurate in vitro tool for predicting in vivo drug permeability characteristics both in dogs and humans is highly desirable. Such a tool could be the canine intestinal organoid system, characterized by three-dimensional (3D), self-assembled epithelial structures derived from adult stem cells.
The (1) Permeable Support Seeding Protocol describes the experimental methods for dissociating and seeding canine organoids in the inserts. Canine organoid isolation, culture, and harvest have been previously described in a separate set of protocols in this special issue. Methods for general upkeep of the canine intestinal organoid monolayer are discussed thoroughly in the (2) Monolayer Maintenance Protocol. Additionally, this protocol describes methods to assess the structural integrity of the monolayer via transepithelial electrical resistance (TEER) measurements and light microscopy. Finally, the (3) Permeability Experimental Protocol&#160;describes the tasks directly preceding an experiment, including in vitro validation of experimental results.
Overall, the canine organoid model, combined with a dual-chamber cell culture technology, overcomes limitations associated with 2D experimental models, thereby improving the reliability of predictions of the apparent oral permeability of therapeutic drug candidates both in the canine and human patient.

Here, we present a protocol describing the culture of canine intestinal organoids in a dual-chamber, permeable support system. Organoid seeding in the permeable supports, the monolayer maintenance, and subsequent drug permeability experiments are described.

The permeable support system is typically used in conjunction with traditional two-dimensional (2D) cell lines as an in vitro tool for evaluating the oral ...