This work was supported by the National Natural Science Foundation of China (No.: 81903902), the China Postdoctoral Science Foundation (No.: 2019M663457), the Sichuan Science and Technology Program (No.: 2020YJ0172), and the Xinglin Scholar Research Premotion Project of Chengdu University of TCM (No.: QJRC2022053).

The animal experiment protocol was reviewed and approved by the Management Committee of Chengdu University of Traditional Chinese Medicine (Record No. 2021-11). Male C57/BL mice (20-25 g, 6-8 weeks old) were used for the present study. The mice were kept in an animal chamber and were free to drink and eat during the experiment.
1. Preparation
<ol>
	<li>Ensure that the intubation platform consists of a base, a riser, a paper clip, two rubber bands, and some strings. Take a string, pass the string through the two holes at the top of the riser, and tie the two ends of the string, respectively, to the small protrusions at the top of the riser. 
	NOTE: Leave room for the mouse&#39;s head to pass through between the string and the two holes.</li>
	<li>Tie two rubber bands to each end of the paper clip, and tape the paper clip with the rubber bands to the back of the riser. Finally, fix the riser to the base at 90&#176; (Figure 1).</li>
	<li>Select a cannula of the appropriate size and length. For a 20&#8722;30 g mouse, a 22 G catheter (2.5&#8722;3.8 cm long) can be used11. Assemble the cannula onto a cannula pen, and turn on the pen&#39;s light (Figure 2).</li>
	<li>Prepare small surgical forceps and a Pasteur pipette by disinfecting them with 70% alcohol.</li>
</ol>
2. Preparation of the test compound
<ol>
	<li>Weight and dissolve 3 mg of LPS in 1 mL of phosphate-buffered saline (PBS, pH 7.2) to form an LPS solution with a concentration of 3 mg/mL.</li>
	<li>Weigh and dissolve 10 mg of pentobarbital sodium in 1 mL of normal saline to form a 1% pentobarbital sodium solution. Filter-sterilize the solution using a 0.45 &#181;m syringe filter.</li>
</ol>
3. Noninvasive oropharyngeal instillation
<ol>
	<li>Anesthetize the mice with an intraperitoneal injection of 1% pentobarbital sodium at a dose of 50 mg/kg12,13. Determine the depth of anesthesia by a lack of response to the righting reflex.</li>
	<li>Place the anesthetized mouse on the intubation platform. Fix the top front teeth with the thread and the two forefeet with the rubber bands (Figure 3).</li>
	<li>Pull the tongue out with tweezers, and hold it with the left hand. Push the cannula slowly, along the mouth, with the right hand up, to the mandibular epiglottis. Use the light of the cannula pen to find the trachea, and slowly insert it into the trachea (Figure 4).</li>
	<li>After the cannula has been inserted into the trachea, withdraw the intubation pen slowly, and leave the cannula inside. Insert the Pasteur pipette into the cannula joint, and press the head (Figure 5). 
	NOTE: If the chest of the mouse bulges, then the intubation is successful (Figure 6).</li>
	<li>After successful endotracheal intubation, instill the mice with 3 mg/mL LPS at 3 mg/kg through the cannula using a flat-head microsyringe14,15 (Figure 7).</li>
	<li>Once done, remove the cannula and the microsyringe. Remove the mouse from the scaffold, and place it in a cage separately to recover. Observe the respiratory state of the mouse until it has recovered and regained conciousness. 
	NOTE: At 12 h after LPS tracheal instillation, euthanize the mice following the procedure approved by the animal ethics committee. Serum TNF-&#945; assays and dry-wet lung weight measurements were performed using standard procedures.</li>
</ol>

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The authors have nothing to disclose.

Initially, we looked inside the oral cavity to find the location of the trachea19. However, during this process, we discovered that the trachea of C57/BL mice is narrow, which makes it difficult to find the correct location by this method without the help of equipment such as an endoscope20. Upon further exploration, we found that the light from the intubator lamp could penetrate the surface of the body, allowing the operator to determine the position of the cannula<sup cla...

Acute lung injury (ALI) is a common clinical syndrome. Under a variety of pathogenic factors, the disruption of the physiological barrier of the lung epithelial cells and vascular endothelial cells leads to increased alveolar permeability, thereby causing decreased lung compliance, pulmonary edema, and severe hypoxemia1. Acute respiratory distress syndrome (ARDS) is the most severe form of ALI. Uncontrolled inflammation and oxidative stress damage are considered to be the main causes of ALI and the more severe ARDS2. When alveolar epithelial cells are directly injured due to trauma, the inflammatory response chain of alveolar macrophages is activated, leading to inflammation in the lung3. Globally, there are more than 3 million patients with acute ARDS per year, and they account for approximately 10% of intensive care unit admissions; additionally, the mortality rate in severe cases is as high as 46%4,5,6. Therefore, there is a need to establish a suitable animal model of ALI to study its pathogenesis. The mouse is the most commonly used experimental animal in the study of ALI since its respiratory tract can simulate the human respiratory tract well for ALI studies. Furthermore, ALI manifests as massive inflammatory cell infiltration, increased pulmonary vascular permeability, and pulmonary edema. The changes in inflammatory cytokines in serum and the lung dry-wet weight ratio reflect the degree of ALI7.
At present, the main methods for modeling LPS-induced ALI in mice include intranasal and surgical tracheal intubation8,9. Here, we propose a new method to deliver LPS into the trachea via noninvasive oropharyngeal intubation. This method uses an illuminated intubator to find the trachea of the mouse and then delivers LPS into the trachea and lung. This method delivers LPS to the lungs more accurately than the intranasal method of delivery. Compared with surgical tracheal intubation, this method does not require surgery, avoids causing wounds, and reduces pain in mice10. Therefore, this method can be used to establish a more convincing mouse model of ALI.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Lipopolysaccharide</td>
			<td>MERK</td>
			<td>L4130</td>
			<td>LPS</td>
		</tr>
		<tr>
			<td>Microliter Syringes</td>
			<td>SHANGHAI GAOGE INDUSTRY AND TRADE CO., LTD</td>
			<td>10028505008124</td>
			<td>To deliver LPS</td>
		</tr>
		<tr>
			<td>Mouse cannula</td>
			<td>RWD Life Science</td>
			<td>803-03008-00</td>
			<td>Mouse cannula</td>
		</tr>
		<tr>
			<td>Mouse intubation kit</td>
			<td>RWD Life Science</td>
			<td>903-03027-00</td>
			<td>Including a base, a riser, a intubator, a surgical forceps and some strings</td>
		</tr>
		<tr>
			<td>Pasteur pipette</td>
			<td>Biosharp life science</td>
			<td>BS-XG-03</td>
			<td>To verify the success of intubation</td>
		</tr>
		<tr>
			<td>Pentobarbital sodium</td>
			<td>Beijing Chemical Co., China</td>
			<td>20220918</td>
			<td>To anesthetize mice</td>
		</tr>
	</tbody>
</table>

noninvasive intratracheal lipopolysaccharide instillation in mice

The acute lung injury (ALI) mouse model induced by lipopolysaccharide (LPS) or endotoxin is still among the most commonly used models in animal studies of acute lung injury or acute inflammation. The current most commonly used methods in acute lung injury mouse models are an intraperitoneal injection of LPS and tracheostomy for the tracheal infusion of LPS. However, the former method lacks lung targeting and damages other organs, and the latter method induces operative trauma, infection risk, and a low survival rate. Here, we recommend a noninvasive oropharyngeal endotracheal intubation method for LPS instillation in mice. In this method, LPS is noninvasively introduced into the trachea through the oropharyngeal cavity to be instilled into the lung with the help of an apparatus for endotracheal intubation. This method not only assures lung targeting but also avoids damage and the risk of death in the animals. We expect that this approach will become widely used in the field of acute lung injury.

The proposed method for LPS instillation in mice was verified by evaluating the expression of the inflammatory cytokine TNF-&#945; and the lung dry-wet weight ratio 12 h after LPS instillation. There were four groups in the experiment: blank control (without any treatment), surgical intubation16, intranasal17,18, and noninvasive oropharyngeal intubation (n = 6). Compared with the blank control group, the se...

Watch this Scientific Journal Video about Noninvasive Intratracheal Lipopolysaccharide Instillation in Mice at JoVE.com

Noninvasive Intratracheal Lipopolysaccharide Instillation in Mice

Here, we propose a protocol for intratracheal lipopolysaccharide (LPS) delivery via noninvasive oropharyngeal endotracheal intubation. This method minimizes the trauma of the surgical procedure for the animal and accurately delivers LPS to the trachea and then to the lungs.

The acute lung injury (ALI) mouse model induced by lipopolysaccharide (LPS) or endotoxin is still among the most commonly used models in animal studies of ...

noninvasive-intratracheal-lipopolysaccharide-instillation-in-mice

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3.9K Views.  Chengdu University of Traditional Chinese Medicine. Here, we propose a protocol for intratracheal lipopolysaccharide (LPS) delivery via noninvasive oropharyngeal endotracheal intubation. This method minimizes the trauma of the surgical procedure for the animal and accurately delivers LPS to the trachea and then to the lungs. 

Video: Noninvasive Intratracheal Lipopolysaccharide Instillation in Mice

Heterotopic Heart Transplantation in Mice

The mouse heterotopic heart transplantation has been used widely since it was introduced by Drs. Corry and Russell in 1973. It is particularly valuable for studying rejection and immune response now that newer transgenic and gene knockout mice are available, and a large number of immunologic reagents have been developed. The heart transplant model is less stringent than the skin transplant models, although technically more challenging. We have developed a modified technique and have completed over 1000 successful cases of heterotopic heart transplantation in mice. When making anastomosis of the ascending aorta and abdominal aorta, two stay sutures are placed at the proximal and distal apexes of recipient abdominal aorta with the donor s ascending aorta, then using 11-0 suture for anastomosis on both side of aorta with continuing sutures. The stay sutures make the anastomosis easier and 11-0 is an ideal suture size to avoid bleeding and thrombosis.
When making anastomosis of pulmonary artery and inferior vena cava, two stay sutures are made at the proximal apex and distal apex of the recipient s inferior vena cava with the donor s pulmonary artery. The left wall of the inferior vena cava and donor s pulmonary artery is closed with continuing sutures in the inside of the inferior vena cava after, one knot with the proximal apex stay suture the right wall of the inferior vena cava and the donor s pulmonary artery are closed with continuing sutures outside the inferior vena cave with 10-0 sutures. This method is easier to perform because anastomosis is made just on the one side of the inferior vena cava and 10-0 sutures is the right size to avoid bleeding and thrombosis. In this article, we provide details of the technique to supplement the video.

The mouse heterotopic heart transplantation model has been proven by many investigators to be an important method for studying mechanisms of rejection and immune response. However, the techniques involved are still challenging. By modifying standard techniques we have had success with more than 1000 transplants.

The mouse heterotopic heart transplantation has been used widely since it was introduced by Drs. Corry and Russell in 1973. It is particularly valuable ...

Small Bowel Transplantation In Mice

Since 1990, the development of tacrolimus-based immunosuppression and improved surgical techniques, the increased array of potent immunosuppressive medications, infection prophylaxis, and suitable patient selection helped improve actuarial graft and patient survival rates for all types of intestine transplantation. Patients with irreversible intestinal failure and complications of parenteral nutrition should now be routinely considered for small intestine transplantation. However, Survival rates for small intestinal transplantation have been slow to improve compares increasingly favorably with renal, liver, heart and lung. The small bowel transplantation is still unsatisfactory compared with other organs. Further progress may depend on better understanding of immunology and physiology of the graft and can be greatly facilitated by animal models. A wider use of mouse small bowel transplantation model is needed in the study of immunology and physiology of the transplantation gut as well as efficient methods in diagnosing early rejection. However, this model is limited to use because the techniques involved is an extremely technically challenging. We have developed a modified technique. When making anastomosis of portal vein and inferior vena cava, two stay sutures are made at the proximal apex and distal apex of the recipient s inferior vena cava with the donor s portal vein. The left wall of the inferior vena cava and donor s portal vein is closed with continuing sutures in the inside of the inferior vena cava after, after one knot with the proximal apex stay suture the right wall of the inferior vena cava and the donor s portal vein are closed with continuing sutures outside the inferior vena cave with 10-0 sutures. This method is easier to perform because anastomosis is made just on the one side of the inferior vena cava and 10-0 sutures is the right size to avoid bleeding and thrombosis.  In this article, we provide details of the technique to supplement the video.

The mouse small bowel transplantation model has been recognized as an important tool to study mechanismes of immune rejection and screen new immunosuppressive drugs. However, this model is limited to use because the techniques involved is an extremely technically challenge. Now we introduce the modified technique.

Since 1990, the development of tacrolimus-based immunosuppression and improved surgical techniques, the increased array of potent immunosuppressive ...

Noninvasive In Vivo Small Animal MRI and MRS: Basic Experimental Procedures

Small animal Magnetic Resonance (MR) research has emerged as an important element of modern biomedical research due to its non-invasive nature and the richness of biological information it provides. MR does not require any ionizing radiation and can noninvasively provide higher resolution and better signal-to-noise ratio in comparison to other tomographic or spectroscopic modalities. In this protocol, we will focus on small animal MR imaging and MR spectroscopy (MRI/MRS) to noninvasively acquire relaxation weighted 1H images of mouse and to obtain 31P spectra of mouse muscle. This work does not attempt to cover every aspect of small animal MRI/MRS but rather introduces basic procedures of mouse MRI/MRS experiments. The main goal of this work is to inform researchers of the basic procedures for in vivo MR experiments on small animals. The goal is to provide a better understanding of basic experimental procedures to allow researchers new to the MR field to better plan for non-MR components of their studies so that both MR and non-MR procedures are seamlessly integrated.

Noninvasive In Vivo Small Animal MRI and MRS: Basic Experimental Procedures

This work describes basic procedures of noninvasive small animal MRI and MRS in vivo.

Small animal Magnetic Resonance (MR) research has emerged as an important element of modern biomedical research due to its non-invasive nature and the ...

Transverse Aortic Constriction in Mice

Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model for pressure overload-induced cardiac hypertrophy and heart failure.1 TAC initially leads to compensated hypertrophy of the heart, which often is associated with a temporary enhancement of cardiac contractility. Over time, however, the response to the chronic hemodynamic overload becomes maladaptive, resulting in cardiac dilatation and heart failure.2 The murine TAC model was first validated by Rockman et al.1, and has since been extensively used as a valuable tool to mimic human cardiovascular diseases and elucidate fundamental signaling processes involved in the cardiac hypertrophic response and heart failure development. When compared to other experimental models of heart failure, such as complete occlusion of the left anterior descending (LAD) coronary artery, TAC provides a more reproducible model of cardiac hypertrophy and a more gradual time course in the development of heart failure. Here, we describe a step-by-step procedure to perform surgical TAC in mice. To determine the level of pressure overload produced by the aortic ligation, a high frequency Doppler probe is used to measure the ratio between blood flow velocities in the right and left carotid arteries.3, 4 With surgical survival rates of 80-90%, transverse aortic banding is an effective technique of inducing left ventricular hypertrophy and heart failure in mice.

Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model to study mechanisms underlying cardiac hypertrophy and heart failure development. Here, we describe procedures to constrict the aorta to create a reproducible degree of cardiac hypertrophy in mice.

Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model for pressure overload-induced cardiac hypertrophy and heart ...

Ambulatory ECG Recording in Mice

Telemetric ECG recording in mice is essential to understanding the mechanisms behind arrhythmias, conduction disorders, and sudden cardiac death. Although the surface ECG is utilized for short-term measurements of waveform intervals, it is not practical for long-term studies of heart rate variability or the capture of rare episodes of arrhythmias. Implantable ECG telemeters offer the advantages of simple surgical implantation, long-term recording of electrograms in ambulatory mice, and scalability with simultaneous recordings of multiple animals. Here, we present a step-by-step guide to the implantation of telemeters for ambulatory ECG recording in mice. Careful adherence to aseptic technique is required for favorable survival results with the possibility of implantation and recording from weeks to months. Thus, implantable ECG telemetry is a valuable tool for detection of critical information on cardiac electrophysiology in ambulatory animal models such as the mouse. 

Telemetric ECG has emerged as an essential tool in evaluating animal models for cardiac arrhythmias and sudden cardiac death. Here, we present a stepwise guide to telemetric ECG recordings for application in long-term ambulatory ECG monitoring in mice.

Telemetric ECG recording in mice is essential to understanding the mechanisms behind arrhythmias, conduction disorders, and sudden cardiac death. Although ...

Direct Tracheal Instillation of Solutes into Mouse Lung

Intratracheal instillations deliver solutes directly into the lungs. This procedure targets the delivery of the instillate into the distal regions of the lung, and is therefore often incorporated in studies aimed at studying alveoli. We provide a detailed survival protocol for performing intratracheal instillations in mice. Using this approach, one can target delivery of test solutes or solids (such as lung therapeutics, surfactants, viruses, and small oligonucleotides) into the distal lung. Tracheal instillations may be the preferred methodology, over inhalation protocols that may primarily target the upper respiratory tract and possibly expose the investigator to potentially hazardous substances. Additionally, in using the tracheal instillation protocol, animals can fully recover from the non-invasive procedure. This allows for making subsequent physiological measurements on test animals, or reinstallation using the same animal. The amount of instillate introduced into the lung must be carefully determined and osmotically balanced to ensure animal recovery. Typically, 30-75 &mu;L instillate volume can be introduced into mouse lung.

Intratracheal instillations deliver solutes directly into the lungs. This procedure targets the delivery of the instillate into the distal regions of the lung, and is therefore often incorporated in studies aimed at studying alveoli. We provide a detailed survival protocol for performing intratracheal instillations in mice.

Intratracheal instillations deliver solutes directly into the lungs.  This procedure targets the delivery of the instillate into the distal regions of the ...

A Noninvasive Hair Sampling Technique to Obtain High Quality DNA from Elusive Small Mammals

Noninvasive genetic sampling approaches are becoming increasingly important to study wildlife populations. A number of studies have reported using noninvasive sampling techniques to investigate population genetics and demography of wild populations1. This approach has proven to be especially useful when dealing with rare or elusive species2. While a number of these methods have been developed to sample hair, feces and other biological material from carnivores and medium-sized mammals, they have largely remained untested in elusive small mammals. In this video, we present a novel, inexpensive and noninvasive hair snare targeted at an elusive small mammal, the American pika (Ochotona princeps). We describe the general set-up of the hair snare, which consists of strips of packing tape arranged in a web-like fashion and placed along travelling routes in the pikas&#x2019; habitat. We illustrate the efficiency of the snare at collecting a large quantity of hair that can then be collected and brought back to the lab. We then demonstrate the use of the DNA IQ system (Promega) to isolate DNA and showcase the utility of this method to amplify commonly used molecular markers including nuclear microsatellites, amplified fragment length polymorphisms (AFLPs), mitochondrial sequences (800bp) as well as a molecular sexing marker. Overall, we demonstrate the utility of this novel noninvasive hair snare as a sampling technique for wildlife population biologists. We anticipate that this approach will be applicable to a variety of small mammals, opening up areas of investigation within natural populations, while minimizing impact to study organisms.

We present a noninvasive sampling approach to efficiently collect hair samples from elusive small mammals, as shown for the American pika. We demonstrate the utility of this method by extracting DNA from sampled hair and amplifying several types of molecular markers commonly used in studies of wildlife ecology and conservation.

Noninvasive genetic sampling approaches are becoming increasingly important to study wildlife populations. A number of studies have reported using ...

In Vivo SiRNA Transfection and Gene Knockdown in Spinal Cord via Rapid Noninvasive Lumbar Intrathecal Injections in Mice

This report describes a step-by-step guide to the technique of acute intrathecal needle injections in a noninvasive manner, i.e. independent of catheter implantation. The technical limitation of this surgical technique lies in the finesse of the hands. The injection is rapid, especially for a trained experimenter, and since tissue disruption with this technique is minimal, repeated injections are possible; moreover immune reaction to foreign tools (e.g. catheter) does not occur, thereby giving a better and more specific read out of spinal cord modulation. Since the application of the substance is largely limited to the target region of the spinal cord, drugs do not need to be applied in large dosages, and more importantly unwanted effects on other tissue, as observed with a systemic delivery, could be circumvented1,2. Moreover, we combine this technique with in vivo transfection of nucleic acid with the help of polyethylenimine (PEI) reagent3, which provides tremendous versatility for studying spinal functions via delivery of pharmacological agents as well as gene, RNA, and protein modulators.

In Vivo SiRNA Transfection and Gene Knockdown in Spinal Cord via Rapid Noninvasive Lumbar Intrathecal Injections in Mice

This report describes a simple and rapid technique of intrathecal needle puncture for a localized transfection of siRNA in the lumbar spinal cord in mouse under short lasting light anesthesia.

This report describes a step-by-step guide to the technique of acute intrathecal needle injections in a noninvasive manner, i.e. independent of catheter ...

Intravenous Injections in Neonatal Mice

Intravenous injection is a clinically applicable manner to deliver therapeutics. For adult rodents and larger animals, intravenous injections are technically feasible and routine. However, some mouse models can have early onset of disease with a rapid progression that makes administration of potential therapies difficult. The temporal (or facial) vein is just anterior to the ear bud in mice and is clearly visible for the first two days after birth on either side of the head using a dissecting microscope. During this window, the temporal vein can be injected with volumes up to 50 &#956;l. The injection is safe and well tolerated by both the pups and the dams. A typical injection procedure is completed within 1-2 min, after which the pup is returned to the home cage. By the third postnatal day the vein is difficult to visualize and the injection procedure becomes technically unreliable. This technique has been used for delivery of adeno-associated virus (AAV) vectors, which in turn can provide almost body-wide, stable transgene expression for the life of the animal depending on the viral serotype chosen.

Animal models of pediatric disease can experience early onset and aggressive disease progression. Clinically relevant therapy delivery to young mouse models can be technically difficult. This protocol describes a non-invasive intravenous injection method for newborn mice within the first two postnatal days of life.

Intravenous injection is a clinically applicable manner to deliver therapeutics. For adult rodents and larger animals, intravenous injections are ...

Noninvasive Monitoring of Lesion Size in a Heterologous Mouse Model of Endometriosis

Here, we describe a protocol for the implementation of a heterologous mouse model in which progression of endometriosis can be assessed in real time through noninvasive monitoring of fluorescence emitted by implanted ectopic human endometrial tissue. For this purpose, biopsies of human endometrium are obtained from donor women ongoing oocyte donation. Human endometrial fragments are cultured in the presence of adenoviruses engineered to express cDNA for the reporter fluorescent protein mCherry. Upon visualization, labeled tissues with an optimal rate of fluorescence after infection are subsequently chosen for the implantation in recipient mice. One week prior to the implantation surgery, recipient mice are oophorectomized, and estradiol pellets are placed subcutaneously to sustain the survival and growth of lesions. On the day of surgery mice are anesthetized, and peritoneal cavity accessed through a small (1.5 cm) incision by the linea-alba. Fluorescently labeled implants are tweezed, briefly soaked in glue and attached to the peritoneal layer. Incisions are sutured, and animals left to recover for a couple of days. Fluorescence emitted by endometriotic implants is usually non-invasively monitored every 3 days for 4 weeks with an in vivo imaging system. Variations in the size of endometriotic implants can be estimated in real time by quantification of the mCherry signal and normalization against the initial time-point showing maximal fluorescence intensity.
Traditional preclinical rodents of models of endometriosis do not allow non-invasive monitoring of lesion in real time but rather allow evaluation of the effects of drugs assayed at the end point. This protocol allows one to track lesions in real time and is more useful to explore the therapeutic potential of drugs in preclinical models of endometriosis. The main limitation of the model thus generated is that non-invasive monitoring is not possible over long periods of time due to the episomal expression of Ad-virus.

Here, we present a protocol for live-imaging of fluorescently labeled human endometrial fragments grafted in mice. The method allows studying the effects of drugs of choice on endometriotic lesion size through monitoring and quantification of fluorescence emitted by the fluorescent reporter on real time

Here, we describe a protocol for the implementation of a heterologous mouse model in which progression of endometriosis can be assessed in real time ...