This work was supported by NIH R21 AG072011 to OL.

The procedures have been reviewed and approved by the University of Florida IACUC (#202200000227). Male C57BL/6J mice, 17 weeks old, with a body mass ranging from 27 g to 34 g, were used for the present study. The experimental procedures and timeline outlined in this protocol are depicted in Figure 1. As indicated, the protocol spans a total of 11 days. Animals undergo survival surgery (CLP/Sham) on Day 0, followed by four days of fluid and analgesic support. On Day 4, animals begin HLS for ...

Mouse Model for Studying Sepsis-Induced Myopathy with Hindlimb Suspension

<ol>
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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deletion+of+muscle+Igf1+exacerbates+disuse+atrophy+weakness+in+mice.">Deletion of muscle Igf1 exacerbates disuse atrophy weakness in mice.</a> J App Physiol. 131 (3), 881-894 (2021).</li><li>Shrum, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+robust+scoring+system+to+evaluate+sepsis+severity+in+an+animal+model.">A robust scoring system to evaluate sepsis severity in an animal model.</a> BMC Res Notes. 7 (1), 233 (2014).</li><li>Mai, S. H. 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The authors have no conflicts of interest to disclose.

The current protocol provides technical guidelines for the implementation of a new preclinical model of sepsis-induced myopathy. All materials and important steps are described in detail for the reproduction of the model. This approach can reproduce the skeletal muscle dysfunction observed in septic patients, highlighting the role of disuse as a crucial component in worsening myopathy. Thus far, the majority of the preclinical studies addressing sepsis-induced myopathy did not include the disuse as an active component of...

Sepsis is a life-threatening condition due to an overactive immune response that adversely affects multiple organ systems, resulting in a major burden to health systems worldwide1. More recently, the in-hospital mortality linked to sepsis has decreased due to improved intensity care unit (ICU) management1,2. However, approximately 75% of the patients surviving the initial septic insult develop skeletal muscle atrophy (e.g., reductions in cross-sectional area) and weakness (e.g., reductions in force production capacity)3,4. This phenomenon has been characterized as sepsis-induced myopathy, highly linked to impaired physical activity and lack of independence to perform daily living tasks, leading to re-hospitalization and mortality within five years of the initial episode5.
Due to an aggressive and generalized infection, septic patients are exposed to prolonged periods of bed rest while recovering in the ICU. In this context, the skeletal muscle undergoes severe disuse, which likely exacerbates muscle atrophy and weakness3,4. Currently, no treatment has effectively addressed sepsis-induced myopathy. The available preclinical models designed to address the myopathy have used cecal ligation and puncture (CLP)6, cecal slurry7, or injection of purified lipopolysaccharide (LPS), which is a component of the cellular wall in gram-negative bacteria8. Although these models succeed in delivering infection, they do not properly reproduce the muscle disuse observed in septic hosts beyond a natural reduction in physical activity observed in septic animals9. 
The main objective of this study is to provide a detailed description of how to properly execute the model of sepsis-induced myopathy with disuse in mice. We demonstrate the feasibility of combining CLP as a model of sepsis with hindlimb suspension (HLS) as a model of disuse to study sepsis-induced myopathy in mice3. Furthermore, representative results of muscle mechanics and typical morphological changes in response to the model are also provided.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-0 Ethicon Coated Vicryl</td>
			<td>Ethicon</td>
			<td>D5792</td>
			<td>Absorbable suture used for closure of muscle layer and for ligation of the cecum.</td>
		</tr>
		<tr>
			<td>4-0 Ethilon Black 18&#34;&#160;</td>
			<td>Ethicon</td>
			<td>662G</td>
			<td>Non absorbable suture for closure of the skin layer.</td>
		</tr>
		<tr>
			<td>BD&#160; PrecisionGlide Needle 26-28 G</td>
			<td>BD</td>
			<td>305136 for 27g needle</td>
			<td>Needle for puncturing the cecum.</td>
		</tr>
		<tr>
			<td>C57BL/6J mice&#160;</td>
			<td>Jackson Laboratory&#160;</td>
			<td>strain #000664</td>
			<td></td>
		</tr>
		<tr>
			<td>Cotton Tipped Applicators</td>
			<td>Puritan</td>
			<td>S-18991</td>
			<td>Swabs for topical application of iodine.</td>
		</tr>
		<tr>
			<td>Cryostat</td>
			<td>(Leica CM1950)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dynarex Povidone Iodine Prep Solution</td>
			<td>Dynarex</td>
			<td>1415</td>
			<td>Topical Antiseptic Liquid for Skin and Mucosa</td>
		</tr>
		<tr>
			<td>Ethanol 200 Proof (100%)</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td>To make 70% ethanol for cleaning skin.</td>
		</tr>
		<tr>
			<td>Hindlimb Suspension Cages</td>
			<td>Custom Made</td>
			<td>N/A</td>
			<td>These custom made cages will be highlighted in the video recordings of the MS.</td>
		</tr>
		<tr>
			<td>Optixcare Eye Lube</td>
			<td>Optixcare</td>
			<td></td>
			<td>Eye lube for protection during survival surgery.</td>
		</tr>
		<tr>
			<td>Scalpel blades #11</td>
			<td>Fine Science</td>
			<td></td>
			<td>Blade used to make incisions on skin and muscle.</td>
		</tr>
		<tr>
			<td>Skin-Trac</td>
			<td>Zimmer</td>
			<td>736579</td>
			<td>Foam tape for fixing the tail to the suspension apparatus.</td>
		</tr>
		<tr>
			<td>SomnoSuite Low-Flow Digital Vaporizer</td>
			<td>Kent Scientific Corporation</td>
			<td>SS-01</td>
			<td>Vaporizer for Isoflurane Anesthesia</td>
		</tr>
		<tr>
			<td>Tissue bath apparatus&#160;</td>
			<td>Aurora Scientific</td>
			<td>Model 800A, Dual Mode Muscle Lever 300C</td>
			<td></td>
		</tr>
	</tbody>
</table>

a preclinical model of sepsis-induced myopathy with disuse in mice

Sepsis is a major cause of in-hospital deaths. Improvements in treatment result in a greater number of sepsis survivors. Approximately 75% of the survivors develop muscle weakness and atrophy, increasing the incidence of hospital readmissions and mortality. However, the available preclinical models of sepsis do not address skeletal muscle disuse, a key component for the development of sepsis-induced myopathy. Our objective in this protocol is to provide a step-by-step guideline for a mouse model that reproduces the clinical setting experienced by a bedridden septic patient. Male C57Bl/6 mice were used to develop this model. Mice underwent cecal ligation and puncture (CLP) to induce sepsis. Four days post-CLP, mice were subjected to hindlimb suspension (HLS) for seven days. Results were compared with sham-matched surgeries and/or animals with normal ambulation (NA). Muscles were dissected for in vitro muscle mechanics and morphological assessments. The model results in marked muscle atrophy and weakness, a similar phenotype observed in septic patients. The model represents a platform for testing potential therapeutic strategies for the mitigation of sepsis-induced myopathy.

Author Spotlight: Advanced Integrated Model for Sepsis-Induced Myopathy and Single-Cell Metabolic Analysis

A Preclinical Model of Sepsis-Induced Myopathy with Disuse in Mice

Our research focuses on understanding the mechanisms behind sepsis induced myopathy. Current models overlook the disuse component, which is crucial for bad reading septic patients. We aim to integrate this aspect for a more accurate disease model.We have significantly advanced the field by combining cecal ligation and puncture model with high limb suspension. This integrated approach allow us to study the systematic effect of sepsis and the impact of muscle disuse on sepsis induced myopathy, providing a more realistic model for understanding the disease progression and potential interventions. Our protocol combines cecal ligation and puncture with high limb suspension to replicate the clinical scenario of human sepsis more accurately in mice.By simulating muscle atrophy and weakness seen in septic patients, our approach provides a comprehensive model for studying the interplay between sepsis and muscle function, allowing for more targeted investigations into therapeutic interventions.

For the representative data shown in the results, male C57BL/6J mice, 17 weeks old, with a body mass ranging from 27 to 34 g, were used. The entire protocol takes eleven days to complete and consists of the surgery intervention (CLP or sham), saline and analgesic support (days 0 to 4), and the HLS disuse (days 4 to 11). Terminal experiments can be performed at any point over the suspension phase. To better understand the impact of the model on skeletal muscle function, the results are compiled from several experiments ac...

This murine model combines a septic insult with hindlimb muscle disuse to recapitulate the bedridden feature of the typical septic patient. The model represents a significant departure from previous models to study muscle dysfunction in sepsis and is a reproducible approach to addressing therapeutic strategies to treat this condition.

Sepsis is a major cause of in-hospital deaths. Improvements in treatment result in a greater number of sepsis survivors. Approximately 75% of the ...

a-preclinical-model-of-sepsis-induced-myopathy-with-disuse-in-mice

Research

JoVE Journal

Medicine

Combining Cecal Ligation and Puncture (CLP) with Hindlimb Suspension (HLS) to Study Sepsis-Induced Myopathy in Mice

To begin, transfer the prepared anesthetized mouse to the surgical area and isolate the surgical site with an adhesive drape. Under deep anesthesia, use a scalpel blade to make a ventral midline incision in the skin. Next, use scissors to separate the skin from the muscle layer.With the help of a scalpel blade, make a smaller incision in the muscle layer. Once the bowels are visualized, use blunt forceps to locate the cecum and exteriorize it. Then ligate the cecum with a sterile 5/0 polyglactin absorbable suture.Using a 27-gauge needle, perforate the secum through and through allowing the fecal content to leak. Gently squeeze the secum to externalize the fecal content with caution. Afterward, relocate the secum into the abdominal cavity and close the muscle layer with a sterile 5/0 absorbable suture.Then use a 5/0 nylon non-absorbable suture to close the skin. After that, provide sterile saline via subcutaneous injection in the back of the animal. After four days of recovery from CLP, or sham surgery, use foam tape to attach the anesthetized mouse tail to a short metal chain.Then attach the metal chain to a hook connected to a crossbar along the center of the cage. Affix a second small bar that can move along the crossbar to allow the animal greater movement ability. Then adjust the height of the suspended limbs to prevent the paws from contacting the chow pellets.Ensure that the animals can move via their forelimbs using the metal grid on the cage floor. CLP animals demonstrated increased immune cell populations in their peritoneal lavage compared to sham animals. CLP and HLS lead to approximately 11.8%of body mass loss.A marked decrease in soleus mass was observed when HLS was superimposed with CLP, indicating that smaller fibers comprise a major part of the muscle section. Compared to the control animals, CLP-HLS caused significant impairment in both the absolute and peak forces of the soleus.

343 Views.  University of Florida.  This murine model combines a septic insult with hindlimb muscle disuse to recapitulate the bedridden feature of the typical septic patient. The model represents a significant departure from previous models to study muscle dysfunction in sepsis and is a reproducible approach to addressing therapeutic strategies to treat this condition.

Mouse Model for Studying Sepsis-Induced Myopathy with Hindlimb Suspension

Summary