The authors would like to thank Adriane Mosley and Libuse Jerabek (Stanford) for assistance with the surgical technique.

All animal studies were performed according to the guidelines of UCLA&#39;s animal care and use committee and the National Institutes of Health Guide for the Care and Use of Laboratory Animals. The duration of the procedure described below is approximately 45-60 min from beginning to end.
1. Preparation of Surgical Field
<ol>
	<li>Perform procedure in a clean animal surgery room.</li>
	<li>Equipment: isoflurane Vaporizer, Gaymer T Pump with heating pad.</li>
	<li>Sterile tools: two curved forceps, fine scissors, needle holder.</li>
	<li>Sterile gloves must be used during the entire procedure.</li>
</ol>
2. Preparation of Animals
<ol>
	<li>Place two male or female mice, from same genetic background, of similar weight and size in the same cage and monitor for at least two weeks to ensure harmonious cohabitation. Female mice are preferred due to their less aggressive behavior.</li>
	<li>Anesthetize animals by using an isoflurane vaporizer. Place mice in a Posi-Seal Induction Chamber connected to the isoflurane vaporizer (4-5% v/v). Once anesthesia is induced, transfer the animal to the fur shaving area and maintain the anesthesia throughout the procedure through a nose cone connected to isoflurane (1.5-2% v/v). Apply ophthalmic ointment with a Q-tip to prevent dry eyes.</li>
	<li>Place the animal on the supine position. Thoroughly shave the left side of the mouse placed on the left and the right side of the mouse placed on the right starting at approximately 1 cm above the elbow to 1 cm below the knee.</li>
	<li>Aseptically prepare the shaved areas by thoroughly wiping (2-3x) with Betadine-soaked wipes followed by alcohol wipes. Place the mice on a heated pad covered by a sterile pad.</li>
	<li>For analgesia, administer Carprofen and Buprenorphine intraperitoneally or subcutaneously at a dose of 10 mg/kg and 0.1 mg/kg respectively.</li>
	<li>Place animals on their side, back to back, with adjacent shaved areas facing up. To avoid any contamination of the surgical area, cover the mice with a sterile drape exposing only the operation area. Create a small drape opening to stay sterile when performing the surgery. We made the drape window large to have a better viewing during videotaping.</li>
</ol>
3. Parabiosis
<ol>
	<li>Using a sharp scissor, perform longitudinal skin incisions to the shaved sides of each animal starting at 0.5 cm above the elbow all the way to 0.5 cm below the knee joint (Figure 1). Following the incision, gently detach the skin from the subcutaneous fascia by holding the skin up with a pair of curved forceps and separate the fascia with a second pair to create 0.5 cm of free skin. Perform this separation along the entire incision.</li>
	<li>Begin the joining by attaching the left olecranon of one animal to the right olecranon of the other. Both olecranons and knee joints are clearly distinguishable following the skin incision. To facilitate the joining, bend the elbow of the first mouse and pass the needle of the non-absorbable 3-0 suture under the olecranon. Similarly, bend the elbow of the second mouse and pass the same suture under it. Attach joints tightly by a double surgical knot.</li>
	<li>Connect the knee joints following the same procedure.</li>
	<li>Following the attachment of the joints, connect the skin of the two animals with a continuous absorbable 5-0 Vicryl suture starting ventrally from the elbow towards the knee. To prevent skin rupture and separation perform a tight suture closure of the skin in the area around the elbows and knees. Once the ventral skin attachment has been completed, perform a double surgical knot. Place the mice in the prone position and continue the suture dorsally ending with a double surgical knot. Verify the continuity of the suture and confirm the lack of openings.</li>
	<li>Administer 0.5 ml of 0.9% NaCl subcutaneously to each mouse to prevent dehydration.</li>
</ol>
4. Postoperative Recovery
<ol>
	<li>Keep animals on heated pad until recovery.</li>
	<li>Following recovery, provide analgesics carprofen and buprenorphine. Repeat intraperitoneally or subcutaneously every 24 and 12 hr, respectively, for 48 hr at the same doses described above (step 2.5). Monitor animals for signs of pain and distress such as shaking, lethargy, chewing of tail, arched back, lack of grooming, etc. daily for two weeks.</li>
	<li>Prophylactically, treat mice with Sulfamethoxazole /Trimethoprim oral suspension in their water bottle 2 mg sulfa/ml +0.4 mg trim/ml for 10 days to prevent bacterial infections.</li>
	<li>House each parabiotic pair in a clean cage with monolithic bedding material (e.g. paper towel or absorbent sterile pad) to prevent aspiration of bedding material. Return the animals to a bedding filled cage when they are able to maintain sternal recumbency with their head up. To minimize the strain of reaching for food while adjusting to parabiotic existence, place the moistened food pellets on the cage floor. Provide nesting material. In 1-2 weeks parabiotic mice have the ability to ambulate normally on surgically paired fore-and hind-limbs.</li>
	<li>Blood chimerism occurs 10-14 days following the surgery.</li>
</ol>
5. Confirmation and Reverse Procedure
<ol>
	<li>After two weeks draw blood from the tail veins of each mouse for flow-cytometric analysis to confirm blood chimerism (Figure 3).</li>
	<li>Blood processing for flow cytometric analysis: dilute 2-3 drops of blood in 500 &#956;l of 10 mM EDTA. Add 500 &#956;l of 2% dextran (diluted in PBS), mix thoroughly and incubate at 37 &#176;C for 30 min. Transfer the supernatant in a new tube, spin at 1,200 rpm for 5 min and resuspend the pelleted cells in PBS (or other buffer) for flow cytometric analysis.</li>
	<li>Depending on experimental design, the parabiotic pair can be separated at later time points. In our experience, we have maintained parabiosed pairs for up to 9 months without any complications.</li>
	<li>Perform reverse procedure on a sterile surgical surface. Anesthetize mice by placing them in an induction chamber connected to an isoflurane vaporizer (4-5%) and maintain anesthesia with 1.5-2% isoflurane, as described above (step 2.2).</li>
	<li>Remove hair from the area surrounding the initial suture and aseptically prepare the shaved areas as described above (steps 2.3, 2.4).</li>
	<li>For analgesia, administer Carprofen and Buprenorphine intraperitoneally or subcutaneously at a dose of 10 mg/kg and 0.1 mg/kg, respectively.</li>
	<li>Cover surgical area with a sterile drape as described above (step 2.6).</li>
	<li>Using sharp scissors, separate the mice through a longitudinal incision along the lateral suture and gently detach the newly formed fascia between the two mice with a pair of curved forceps. To separate the joints, cut the knots of the suture connecting them. Trim off the skin along the incision to achieve smooth edges and reattach skin with an absorbable continuous 5-0 coated Vicryl suture.</li>
	<li>To prevent dehydration, administer 0.5 ml of 0.9% NaCl subcutaneously to each mouse. Keep animals on heated pad until recovery.</li>
	<li>After recovery, repeat analgesic administration, carprofen (10 mg/kg) every 24 hr and buprenorphine (0.1 mg/kg) every 12 hr for 48 hr.</li>
	<li>To prevent bacterial infections treat mice with Sulfamethoxazole /Trimethoprim oral suspension (2 mg sulfa/ml +0.4 mg trim/ml) in their water bottle for 10 days.</li>
</ol>

<ol><li>Bert, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Exp%C3%A9riences+et+consid%C3%A9rations+sur+la+greffe+animale%5BTitle%5D)+AND+%22Journal+de+l%27Anatomie+et+de+la+Physiologie%22%5BJournal%5D)">Expériences et considérations sur la greffe animale.</a> Journal de l'Anatomie et de la Physiologie. 1, 69-87 Forthcoming.</li>
<li>Bunster, E., Meyer, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Improved+methods+of+parabiosis%5BTitle%5D)+AND+%22Anat.+Rec%22%5BJournal%5D)">Improved methods of parabiosis.</a> Anat. Rec. 57, 339-380 (1933).</li>
<li>Waskow, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Generation+of+parabiotic+mice+for+the+study+of+DC+and+DC+precursor+circulation%5BTitle%5D)+AND+%22Methods+Mol.+Biol%22%5BJournal%5D)">Generation of parabiotic mice for the study of DC and DC precursor circulation.</a> Methods Mol. Biol. 595, 413-428 (2010).</li>
<li>Finerty, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Parabiosis+in+physiological+studies%5BTitle%5D)+AND+%22Physiol.+Rev%22%5BJournal%5D)">Parabiosis in physiological studies.</a> Physiol. Rev. 32, 277-302 (1952).</li>
<li>Aicher, A., Heeschen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nonbone+marrow-derived+endothelial+progenitor+cells%3A+what+is+their+exact+location%5BTitle%5D)+AND+%22Circ.+Res%22%5BJournal%5D)">Nonbone marrow-derived endothelial progenitor cells: what is their exact location.</a> Circ. Res. 101, e102(2007).</li>
<li>Abe, S., Boyer, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cells+derived+from+the+circulation+contribute+to+the+repair+of+lung+injury%5BTitle%5D)+AND+%22Am.+J.+Respir.+Crit.+Care+Med%22%5BJournal%5D)">Cells derived from the circulation contribute to the repair of lung injury.</a> Am. J. Respir. Crit. Care Med. 170, 1158-1163 (2004).</li>
<li>Donskoy, E., Goldschneider, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Thymocytopoiesis+is+maintained+by+blood-borne+precursors+throughout+postnatal+life.+A+study+in+parabiotic+mice%5BTitle%5D)+AND+%22J.+Immunol%22%5BJournal%5D)">Thymocytopoiesis is maintained by blood-borne precursors throughout postnatal life. A study in parabiotic mice.</a> J. Immunol. 148, 1604-1612 (1992).</li>
<li>Powell, A. E., Anderson, E. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fusion+between+Intestinal+epithelial+cells+and+macrophages+in+a+cancer+context+results+in+nuclear+reprogramming%5BTitle%5D)+AND+%22Cancer+Res%22%5BJournal%5D)">Fusion between Intestinal epithelial cells and macrophages in a cancer context results in nuclear reprogramming.</a> Cancer Res. 71, 1497-1505 (2011).</li>
<li>Duyverman, A. M., Kohno, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+transient+parabiosis+skin+transplantation+model+in+mice%5BTitle%5D)+AND+%22Nat.+Protoc%22%5BJournal%5D)">A transient parabiosis skin transplantation model in mice.</a> Nat. Protoc. 7, 763-770 (2012).</li>
<li>Ajami, B., Bennett, J. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Local+self-renewal+can+sustain+CNS+microglia+maintenance+and+function+throughout+adult+life%5BTitle%5D)+AND+%22Nat.+Neurosci%22%5BJournal%5D)">Local self-renewal can sustain CNS microglia maintenance and function throughout adult life.</a> Nat. Neurosci. 10, 1538-1543 (2007).</li>
<li>Weissman, I. L., Jerabek, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tolerance+and+the+H-Y+antigen%3A+Requirement+for+male+T+cells%2C+but+not+B+cells%2C+to+induce+tolerance+in+neonatal+female+mice%5BTitle%5D)+AND+%22Transplantation%22%5BJournal%5D)">Tolerance and the H-Y antigen: Requirement for male T cells, but not B cells, to induce tolerance in neonatal female mice.</a> Transplantation. 37, 3-6 (1984).</li>
</ol>

The authors have no competing financial interests.

The parabiosis method discussed here presents minimal technical difficulties and results in low mortality rates. The attachment of knee and elbow joints is a significant improvement of the Bunster and Meyer technique. However, the procedure remains invasive thus maintenance of sterile conditions throughout the surgery is imperative. To further prevent infection of the surgical site, it is important that the parabiosed animals receive a combination of antibiotics and be monitored regularly. To ensure firm support and prev...

Parabiosis, the surgical joining of two organisms, was first described in 1864 by Paul Bert as a way to develop a model to study shared circulatory systems and consisted of the joining of the skin and muscular walls of two rats1. Parabiosis promotes formation of microvasculature at the site of inflammation3 and has had several applications in physiological studies, such as the hormonal communication between the pituitary gland and gonads as well as the role of the kidney in hypertension4. It has been further employed to investigate the recruitment and integration of progenitor cells in neovascularization5, migration of hematopoietic stem cells6, and lymphocyte trafficking7, as well as the role and kinetics of circulating inflammatory or stem cells in tumor metastasis8,9, and neurodegenerative disease10.
One significant advantage of parabiosis lies in that the partnered animals share common circulating antigens, allowing cell migration and neovascularization without triggering an immunological reaction. Importantly, Weissman et al. have shown that parabiosis between male and female mice does not lead to formation of anti H-Y antibodies11.
In the original protocol described by Paul Bert the two animals were joined together through connection of the skin and muscle walls1. This method however, caused significant strain to the animals and resulted in high mortality due to infection of the wound. Since then the parabiosis technique has been revised by several groups with the most predominant being the protocol proposed by Bunster and Meyer in 19332. Their method included joining of the scapula joints, body cavities, and skin, permitting better support and less pain for the animals. At the same time, the new method resulted in minimal post-operative care and significantly decreased mortality rates. The protocol described herein is a modification of the Bunster and Meyer technique that is less invasive and allows firmer joining. Namely, mice are connected through the elbow and knee joints as well as the skin. This joining prevents extension of the skin and therefore causes less pain and complications. Here we describe the joining of a wild type (WT) adult mouse to a constitutive GFP expressing mouse. We show that two weeks following surgery we can achieve 50% of blood chimerism demonstrating the efficacy of this surgical procedure to create a shared circulatory system.

<table><tbody><tr><td>Isoflurane-Phoenix</td><td>Clipper</td><td>NDC 57319-559-06</td><td></td></tr><tr><td>Posi-Seal Induction Chamber</td><td>Molecular Imaging Products</td><td>AS-01-0530-SM</td><td></td></tr><tr><td>Portable Anesthesia System</td><td>Molecular Imaging Products</td><td>AS-01-0007</td><td></td></tr><tr><td>Gaymer T Pump</td><td>Gaymar Industries, Inc</td><td>TP650</td><td></td></tr><tr><td>Warming Blanket (Heating pad)</td><td>Kent Scientific Corp</td><td>TP-22G</td><td></td></tr><tr><td>Curved forceps</td><td>Roboz</td><td>RS-5101</td><td></td></tr><tr><td>Scissors</td><td>Fine Science Tools (FST)</td><td>FST 14063-09</td><td></td></tr><tr><td>Needle holder</td><td>FST</td><td>FST 12501-13</td><td></td></tr><tr><td>Electrical shaver</td><td>Oster</td><td>Golden A5</td><td></td></tr></tbody></table>

parabiosis in mice: a detailed protocol

Parabiosis is a surgical union of two organisms allowing sharing of the blood circulation. Attaching the skin of two animals promotes formation of microvasculature at the site of inflammation. Parabiotic partners share their circulating antigens and thus are free of adverse immune reaction. First described by Paul Bert in 18641, the parabiosis surgery was refined by Bunster and Meyer in 1933 to improve animal survival2. In the current protocol, two mice are surgically joined following a modification of the Bunster and Meyer technique. Animals are connected through the elbow and knee joints followed by attachment of the skin allowing firm support that prevents strain on the sutured skin. Herein, we describe in detail the parabiotic joining of a ubiquitous GFP expressing mouse to a wild type (WT) mouse. Two weeks after the procedure, the pair is separated and GFP positive cells can be detected by flow cytometric analysis in the blood circulation of the WT mouse. The blood chimerism allows one to examine the contribution of the circulating cells from one animal in the other.

The anticipated outcome of parabiosis of two organisms is the equal contribution of each animal's circulatory system to a common blood circulation (Figure 2). One can easily verify the successful equilibration of the blood of the parabiosed WT and GFP positive mice by flow cytometric analysis. Here, venous blood was obtained from the tails of both parabionts at 2 weeks after the surgery and was fractionated for peripheral blood cells (to exclude erythrocytes). The fractionated hematopoietic-derived cell ...

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Parabiosis in Mice: A Detailed Protocol

Parabiotic joining of two organisms leads to the development of a shared circulatory system. In this protocol, we describe the surgical steps to form a parabiotic connection between a wild-type mouse and a constitutive GFP-expressing mouse.

Parabiosis is a surgical union of two organisms allowing sharing of the blood circulation. Attaching the skin of two animals promotes formation of ...

Research

JoVE Journal

Medicine

74.4K Views.  University of California, Los Angeles. Parabiotic joining of two organisms leads to the development of a shared circulatory system. In this protocol, we describe the surgical steps to form a parabiotic connection between a wild-type mouse and a constitutive GFP-expressing mouse.

Video: Parabiosis in Mice: A Detailed Protocol

Lentiviral Mediated Production of Transgenic Mice: A Simple and Highly Efficient Method for Direct Study of Founders

For almost 40 years, pronuclear DNA injection represents the standard method to generate transgenic mice with random integration of transgenes. Such a routine procedure is widely utilized throughout the world and its main limitation resides in the poor efficacy of transgene integration, resulting in a low yield of founder animals. Only few percent of animals born after implantation of injected fertilized oocytes have integrated the transgene. In contrast, lentiviral vectors are powerful tools for integrative gene transfer and their use to transduce fertilized oocytes allows highly efficient production of founder transgenic mice with an average yield above 70%. Furthermore, any mouse strain can be used to produce transgenic animal and the penetrance of transgene expression is extremely high, above 80% with lentiviral mediated transgenesis compared to DNA microinjection. The size of the DNA fragment that can be cargo by the lentiviral vector is restricted to 10 kb and represents the major limitation of this method. Using a simple and easy to perform injection procedure beneath the zona pellucida of fertilized oocytes, more than 50 founder animals can be produced in a single session of microinjection. Such a method is highly adapted to perform, directly in founder animals, rapid gain and loss of function studies or to screen genomic DNA regions for their ability to control and regulate gene expression in vivo.

Here, we present a protocol to promote transgene integration and production of founder transgenic mice with high efficacy by a simple injection of a lentiviral vector in the perivitelline space of a fertilized oocyte.

For almost 40 years, pronuclear DNA injection represents the standard method to generate transgenic mice with random integration of transgenes. Such a ...

Genetics

Generation of Parabiotic Zebrafish Embryos by Surgical Fusion of Developing Blastulae

Surgical parabiosis of two animals of different genetic backgrounds creates a unique scenario to study cell-intrinsic versus cell-extrinsic roles for candidate genes of interest, migratory behaviors of cells, and secreted signals in distinct genetic settings. Because parabiotic animals share a common circulation, any blood or blood-borne factor from one animal will be exchanged with its partner and vice versa. Thus, cells and molecular factors derived from one genetic background can be studied in the context of a second genetic background. Parabiosis of adult mice has been &#160;used extensively to research aging, cancer, diabetes, obesity, and brain development. More recently, parabiosis of zebrafish embryos has been used to study the developmental biology of hematopoiesis. In contrast to mice, the transparent nature of zebrafish embryos permits the direct visualization of cells in the parabiotic context, making it a uniquely powerful method for investigating fundamental cellular and molecular mechanisms. The utility of this technique, however, is limited by a steep learning curve for generating the parabiotic zebrafish embryos. This protocol provides a step-by-step method on how to surgically fuse the blastulae of two zebrafish embryos of different genetic backgrounds to investigate the role of candidate genes of interest. In addition, the parabiotic zebrafish embryos are tolerant to heat shock, making temporal control of gene expression possible. This method does not require a sophisticated set-up and has broad applications for studying cell migration, fate specification, and differentiation in vivo during embryonic development.

This protocol provides step-by-step instruction on how to generate parabiotic zebrafish embryos of different genetic backgrounds. When combined with the unparalleled imaging capabilities of the zebrafish embryo, this method provides a uniquely powerful means to investigate cell-autonomous versus non-cell-autonomous functions for candidate genes of interest.

Surgical parabiosis of two animals of different genetic backgrounds creates a unique scenario to study cell-intrinsic versus cell-extrinsic roles for ...

Developmental Biology

Collection of Post-mating Semen from the Female Reproductive Tract and Measurement of Semen Liquefaction in Mice

In mice, ejaculated semen is deposited in the uterus. After ejaculation, the semen changes consistency from gel-like to watery, a process called liquefaction. In this study, we show how to collect the post-ejaculated semen from the female reproductive tract in a mouse model. First, adult female mice in the estrus stage were housed in a male&#39;s cage overnight. The next morning, copulation was confirmed by the presence of copulatory plug at the vaginal opening. Female mice with copulatory plugs were euthanized, and each reproductive tract was collected as a whole (vagina, uterus, oviducts, ovaries), ensuring a closed system to contain the semen. The reproductive tract was placed in a 1.5 mL microcentrifuge tube, and the vagina was cut off to release the semen into the tube. To ensure maximum semen volume for analysis, toothless forceps were used to squeeze the uterine horns from ovarian end to vaginal end expelling remaining semen. The whole reproductive tract was then discarded. The semen-containing tube was briefly spun down. A 25 &#956;L capillary pipette was placed into the tube at a 180&#176; angle (parallel to the tube wall). The amount of time used to fill the capillary tube to the 25 &#956;L line was recorded. Semen from a proven male breeder usually takes approximately 60-180 s to fill a 25 &#956;L capillary tube. This semen collection technique can also be used in other downstream applications such as sperm imaging and motility analysis.

Semen liquefaction is required for sperm to be liberated from the seminal gel. This study provides the procedures for collecting semen from the female reproductive tract post-coitus, and measuring semen liquefaction time.

In mice, ejaculated semen is deposited in the uterus. After ejaculation, the semen changes consistency from gel-like to watery, a process called ...

Murine Round Spermatid Injection Procedure to Study Embryonic Development

Mouse Round Spermatid Injection

Round spermatids, characterized by their haploid genetic content, represent the precursor cells to mature spermatozoa. Through the innovative technique of round spermatid injection (ROSI), oocytes can be successfully fertilized and developed into viable fetuses. In a groundbreaking milestone achieved in 1995, the first mouse fetus was born through ROSI technology. ROSI has since emerged as a pivotal tool for unraveling the intricate mechanisms governing embryonic development and holds significant potential in various applications, including the acceleration of mouse generation and the production of genetically modified mice. In 1996, a milestone was reached when the first human fetus was born through ROSI technology. However, the clinical applications of this method have shown a fluctuating pattern of success and failure. To date, ROSI technology has not found widespread application in clinical practice, primarily due to its low birth efficiency and insufficient validation of fetal safety. This article provides a comprehensive account of the precise methods of performing ROSI in mice, aiming to shed new light on basic research and its potential clinical applications.

Here, we introduce a method for performing round spermatid injection (ROSI) in mice, a technique with promising clinical applications and utility for investigating the mechanisms underlying embryonic development.

Round spermatids, characterized by their haploid genetic content, represent the precursor cells to mature spermatozoa. Through the innovative technique of ...

Cardiopulmonary Bypass in a Mouse Model: A Novel Approach

As prolonged cardiopulmonary bypass becomes more essential during cardiac interventions, an increasing clinical demand arises for procedure optimization and for minimizing organ damage resulting from prolonged extracorporal circulation. The goal of this paper was to demonstrate a fully functional and clinically relevant model of cardiopulmonary bypass in a mouse. We report on the device design, perfusion circuit optimization, and microsurgical techniques. This model is an acute model, which is not compatible with survival due to the need for multiple blood drawings. Because of the range of tools available for mice (e.g., markers, knockouts, etc.), this model will facilitate investigation into the molecular mechanisms of organ damage and the effect of cardiopulmonary bypass in relation to other comorbidities.

This paper describes how to perform cardiopulmonary bypass in mice. This novel model will facilitate the investigation of the molecular mechanisms involved in organ damage.

As prolonged cardiopulmonary bypass becomes more essential during cardiac interventions, an increasing clinical demand arises for procedure optimization ...

A Mouse Model of Orthopedic Surgery to Study Postoperative Cognitive Dysfunction and Tissue Regeneration

Surgery is commonly used to improve and maintain quality of life. Unfortunately, in vulnerable patients such as the elderly, complications may occur and significantly diminish the outcome. Indeed, after routine orthopedic surgery to repair a fracture, as many as 50% of elderly patients suffer from neurologic complications like delirium. Also, the capacity to heal and regenerate tissue after surgery decreases with age, and can impact the quality of fracture repair and even osseous integration of implants. Thus, a better understanding of mechanisms that drive these age-dependent changes could provide strategic targets to minimize risk for such complications and optimize outcomes. Here, we introduce a clinically relevant mouse model of tibial fracture. The postoperative changes in these mice mimic some of the cognitive impairments commonly observed after routine orthopedic surgery in humans. Briefly, an incision is performed in the right hind limb under strictly aseptic conditions. Muscles are disassociated, and a 0.38-mm stainless steel pin is inserted into the upper crest of the tibia, inside the intramedullary canal. Osteotomy is then performed, and the wound is stapled. We have used this model to investigate the effects of surgical trauma on postoperative neuroinflammation and behavioral changes. By applying this fracture model in combination with parabiosis, a surgical model in which 2 mice are anastomosed, we have studied cells and secreted factors that systemically rejuvenate organ function and tissue regeneration after injury. By following our step-by-step protocol, these models can be reproduced with high fidelity, and can be adapted to interrogate many biologic pathways that are altered by surgical trauma.

This protocol describes a mouse model of orthopedic surgery that has been used to study mechanisms of postoperative neuroinflammation and behavioral changes, and when combined with parabiosis, to study tissue regeneration during aging.

Surgery is commonly used to improve and maintain quality of life. Unfortunately, in vulnerable patients such as the elderly, complications may occur and ...

A Modified Murine Heterotopic Heart Transplant Protocol Matching Contemporary Standards of Aseptic Technique, Anesthesia, and Analgesia

The development of experimental models of cardiac transplantation in animals has contributed to many advances in the fields of immunology and solid organ transplantation. While the heterotopic vascularized murine cardiac transplantation model was initially utilized in studies of graft rejection using combinations of mismatched inbred mouse strains, access to genetically modified strains and therapeutic modalities can provide powerful new preclinical insights. Fundamentally, the surgical methodology for this technique has not changed since its development, especially with respect to important factors such as aseptic technique, anesthesia, and analgesia, which make material impacts on postsurgical morbidity and mortality. Additionally, improvements in perioperative management are expected to provide improvements in both animal welfare and experimental outcomes. This paper reports upon a protocol developed in collaboration with a subject matter expert in veterinary anesthesia and describes the surgical technique with an emphasis on perioperative management. Additionally, we discuss the implications of these refinements and provide details on troubleshooting critical surgical steps for this procedure.

The present paper describes a modified technique for heterotopic vascularized cardiac transplantation with updated aseptic technique, analgesia, and anesthesia.

The development of experimental models of cardiac transplantation in animals has contributed to many advances in the fields of immunology and solid organ ...

Immunology and Infection

Operational Protocols for Handling Wildling Mice in Research Facilities

Operating and Biocontainment Procedures of a Facility for Laboratory Mice with a Natural Microbiome: Immunophenotyping Procedure

The use of laboratory mice with a natural microbiome, such as &#34;Wildling mice&#34;, offers a promising research tool for both basic and applied science due to their close resemblance to the human superorganism. However, the breeding and maintenance of these mice, which harbor a diverse microbiome&#160;including bacteria, viruses, and parasites, pose significant challenges for animal husbandry facilities at research institutions. To address these challenges, a specialized facility concept was developed for housing &#34;Wildling mice&#34; at Charit&#233; - Universit&#228;tsmedizin Berlin. This approach involved designing a facility with specific structural features and operational protocols to effectively contain the natural microbiome, thereby protecting areas with higher hygiene standards.
A methodology for blood sampling from both specified pathogen-free (SPF) and &#34;Wildling mice&#34; for immunophenotyping is demonstrated, highlighting the workflow and biocontainment measures implemented in the facility. Remarkable results reveal that &#34;Wildling mice&#34; exposed to a natural microbiome develop distinct immune cell populations, which are significantly reduced in mice bred and maintained under stringent hygiene conditions.
The significance of this study lies in its potential to provide researchers with access to mice that possess a natural microbiome and a mature immune system similar to that of human adults. This approach could enhance the translatability of preclinical findings into clinical practice, thereby advancing the field of biomedical research.

Here, we describe the structure and operating procedures, including microbial containment measures of a facility for "Wilding mice" using blood sampling for immunophenotyping as an example.

The use of laboratory mice with a natural microbiome, such as &#34;Wildling mice&#34;, offers a promising research tool for both basic and applied science ...

Preparation and Maintenance of Bioexclusion IsoPositive Cage Experiment for Human Fecal Transplantation into Germ-Free Mice

Germ-free mice are an important investigation tool for understanding the contribution of microorganisms in host health and disease, enabling assessment of the specific role of individuals, defined or complex groups of microorganisms in host response. Traditionally bred and reared in flexible-film or semi-rigid isolators, germ-free mouse husbandry and experimental manipulation are costly and require numerous trained staff and a large space footprint in animal housing facilities. The IsoPositive caging system allows for experimental manipulation of germ-free mice in individual, hermetically-sealed, positive-pressure isolator cages (isocages), reducing cost and enabling greater flexibility in experimental manipulations. 
Here, a protocol is described for transferring germ-free mice from breeding isolators to isocages and subsequent fecal transfer from human donor stool into mice to create stable long-term gut "humanized" mice for future studies. The materials and preparation needed for the utilization of the isocage system are described, including the use of chlorine-dioxide sterilant chemical sterilant to clean cages, supplies, equipment, and personal protective equipment. The methods for confirming the germ-free status of transferred mice and how to determine contamination in the caging system are discussed. The procedure for husbandry, including bedding, food, and water supply, is further discussed. The protocol for human fecal slurry preparation and gavage into germ-free mice to create gut "humanized" mice, along with stool collection to monitor the microbial community composition of these mice, are described. An experiment illustrates that two weeks post-human fecal transplant allows for stable colonization of donor microbiota in the murine hosts, enabling subsequent experimental usage. Furthermore, the collection of humanized mouse feces in viability preservation media, enabling use in further functional experiments, is described. Overall, these methods allow for the safe and effective establishment of humanized mouse communities in experimental gnotobiotic cages for further manipulation.

This protocol describes the best practices for germ-free mouse transfer to and housing in experimental single-cage isolators (isocages) while maintaining sterile conditions. Methods for fecal transplant into germ-free mice and the collection of viable bacteria from these gut "humanized" mice for further applications are discussed.

Germ-free mice are an important investigation tool for understanding the contribution of microorganisms in host health and disease, enabling assessment of ...

Hormonal, Metabolic, and Electrical Regulation of Isolated Hypothalamic Neurons

Isolation of Targeted Hypothalamic Neurons for Studies of Hormonal, Metabolic, and Electrical Regulation

The hypothalamus regulates fundamental metabolic processes by controlling functions as varied as food intake, body temperature, and hormone release. As the functions of the hypothalamus are controlled by specific subsets of neuronal populations, the ability to isolate them provides a major tool for studying metabolic mechanisms. In this regard, the neuronal complexity of the hypothalamus poses exceptional challenges. 
For these reasons, new techniques, such as Magnetic-Activated Cell Sorting (MACS), have been explored. This paper describes a new application of magnetic-activated cell sorting (MACS) using microbead technology to isolate a targeted neuronal population from prenatal mice brains. The technique is simple and guarantees a highly pure and viable primary hypothalamic neuron culture with high reproducibility. The hypothalamus is gently dissociated, neurons are selectively isolated and separated from glial cells, and finally, using a specific antibody for a cell surface marker, the population of interest is selected. 
Once isolated, targeted neurons can be used to investigate their morphological, electrical, and endocrine characteristics and their responses in normal or pathological conditions. Furthermore, given the variegated roles of the hypothalamus in regulating feeding, metabolism, stress, sleep, and motivation, a closer look at targeted and region-specific neurons may provide insight into their tasks in this complex environment.

Author Spotlight: Hypothalamic Neural Mechanism Insights 

Here we present a protocol to grow specific hypothalamic cell subtypes in culture. The cells can be selected based on opportune/unique membrane markers and used in many applications, including immunofluorescence, electrophysiological, and biochemical assays.

The hypothalamus regulates fundamental metabolic processes by controlling functions as varied as food intake, body temperature, and hormone release. As ...