We thank Amanda Fair, the CMI, and Kathy Sweet and the ORL at UM for assistance with &#181;CT imaging and analysis. Funding: BL Funded by 1K08GM109105-01 and Plastic Surgery Foundation National Endowment Award.

Ethics statement: All animal procedures were carried out in strict accordance with good animal practice as defined in the guidelines provided in the Guide for the Use and Care of Laboratory Animals: Eighth Edition from the Institute for Laboratory Animal Research (ILAR, 2011) and were approved by the Institutional Animal Care and Use Committee of the University of Michigan (PRO0001553).
1. Mouse Surgical Procedures
NOTE: Use 8-10 week old C57BL/6 mice. Other ages, backgrounds, and strains of mice can also be used to test different conditions or genetic make-up. For the tenotomy portion of the procedure, maintain sterile conditions by using face mask, hair bonnet, and sterile gown, gloves, and instruments. Surgical sites should be sterilely prepared with povidone-iodine and sterile draping. Avoid hypothermia by using a veterinary heating pad and warming resuscitation solutions to 37 &#176;C prior to administration.
<ol>
	<li>Anesthetize the mouse using 2.5% inhaled isoflurane. Use a nose cone to leave the dorsum and hind-limbs easily accessible. Adjust the rate of isoflurane administration to maintain appropriate respiratory rate and coloration of mucous membranes and to ensure anesthesia by checking muscle tone, toe pinch, and corneal reflex. Apply bland ophthalmic ointment to the mouse&#8217;s eyes to prevent dry eye injury during the procedure. Maintain adequate body temperature using a veterinary heating pad or warm water circulator beneath the surgical field.</li>
	<li>Administer buprenorphine, 0.1 mg/kg, subcutaneously immediately prior to surgery for analgesia.</li>
	<li>Closely shave the surgical site on the left hind paw using clippers from the heel to the knee.</li>
	<li>Closely shave the dorsum of the mouse, beginning over the spine and extending the shaved area to the left of the dorsal midline, clearing an area at least 2 cm x 3 cm to accommodate the burn injury.</li>
	<li>Prepare the surgical site, including the hind paw to the knee using 3 alternating povidone-iodine scrubs.</li>
	<li>Perform a longitudinal incision along the medial aspect of the left Achilles tendon. Extend the incision so the Achilles tendon can be easily visualized; approximately 0.5 cm.</li>
	<li>Perform an Achilles tenotomy with sharp dissection of the tendon at the midpoint with sharp tissue scissors. Insert one blade of the tissue scissors in the tissue plane beneath the tendon and dissect along the plane until the blade is at the tendon midpoint. Close the scissor blades to sever the tendon sharply. 
	NOTE: Ensure inclusion of all posterior tendons including Gastrocnemius, Soleus, and Plantaris tendons.</li>
	<li>Achieve hemostasis by applying pressure with sterile gauze (there should be minimal bleeding) and close the skin incision with a 5-0 vicryl stitch.</li>
	<li>Perform the dorsal partial thickness burn with an aluminum block weighing 35 g with approximate measurements 2 cm x 2 cm x 3 cm heated to 60 &#176;C in a water bath applied to the shaved dorsum of the mouse for 17 sec. 
	NOTE: Achieve the appropriate burn depth by resting the block on top of the anesthetized mouse, ensuring that the entire surface area of the block is in contact with the mouse, however avoid applying any additional pressure to the block, i.e., allow gravity to be the only force holding the block in place. A thin plastic handle attached to one side of the block is convenient for manipulation, stabilization, and retrieval from the hot water bath. This will create an approximately 30% total body surface area burn in an 8-10 week old C57BL/6 mouse. This contact burn was chosen over other methods (flame or scald burn) due to the uniformity of burn depth over the wound and the reproducibility between animals.</li>
	<li>Dry the burn site with gauze and apply a tegaderm dressing.</li>
	<li>Administer warmed resuscitation fluids: Lactated Ringer&#8217;s solution 1 ml intraperitoneal injection and 0.5 ml subcutaneous injection. This one-time administration of resuscitation is adequate for recovery from the burn injury and tenotomy. 
	NOTE: Do not return anesthetized mice to housing cages with other mice, house individually in clean cages under monitoring until mice are fully recovered. Typical recovery occurs within 1-6 hr. Burn sites generally heal within 2-4 weeks and are rarely complicated by wound infection if kept in clean housing environments.</li>
	<li>Administer Buprenorphine 0.1 mg/kg subcutaneous injection every 12 hr for 3 days following the procedure. Monitor HO growth with serial &#181;CT scans at appropriate intervals. Ectopic bone growth is first evident around 3 weeks post-op by &#181;CT. 
	NOTE: The majority of HO development is complete by 9 weeks post-op. We have not observed a difference in HO volume or location with repeated &#181;CT scans bi-weekly for 15 weeks compared to a single end-point &#181;CT scan at 15 weeks. At the end of the experiments, euthanize all mice with CO2 inhalation according to institutional guidelines and verify death with cervical dislocation after 10 min.</li>
</ol>
2. &#181;CT Acquisition and Analysis
<ol>
	<li>Secure the anesthetized mouse on the scanner bed in the prone position. Tape the hind limbs securely to the bed to prevent breathing motion artifact. Include the air, water, and hydroxyapatite containing phantom beneath the mouse for image calibration.</li>
	<li>Open the Bone Analysis software and define a region of interest (ROI) that encompasses both hind limbs from the hip joint proximally to the tip of the hind paw distally. Obtain an image using the following parameters: 80 kV, 500 &#181;A and 1,300 msec exposure, 48 &#181;m voxel size.14,15</li>
	<li>Calibrate the image to Hounsfield units (HU) by drawing a ROI in each of the three phantom chambers and inputting the average density into the appropriate fields in the software.</li>
	<li>Using the &#8220;grabber&#8221; tool in the software, re-orient the image so the tibia of the left hind limb is parallel along the Z axis to allow the clearest anatomical view for the delineation of orthotopic cortical bone structures and HO.</li>
	<li>Beginning at the knee, scroll distally through the image slices until HO is encountered. Using the manual spline tool, make an ROI around the ectopic bone on every 5th slice continuing distally through the paw or until HO has been surpassed. Use the extrapolate tool to extend and stitch the ROIs together into one ROI that contains all the HO.</li>
	<li>Make a 3D ROI and choose the analysis menu. Calculate the bone volume by setting the lower and upper threshold values that best show the bone window. Use the same fixed threshold values for all scans.</li>
</ol>

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R., 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=Burn+injury+enhances+bone+formation+in+heterotopic+ossification+model.">Burn injury enhances bone formation in heterotopic ossification model.</a> Ann Surg. 259 (5), 993-998 (2014).</li><li>Scott, M. 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=Brief+review+of+models+of+ectopic+bone+formation.">Brief review of models of ectopic bone formation.</a> Stem Cells Dev. 21 (5), 655-667 (2012).</li><li>Tannous, O., Griffith, C., O'Toole, R. V., Pellegrini, V. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterotopic+ossification+after+extremity+blast+amputation+in+a+Sprague-Dawley+rat+animal+model.">Heterotopic ossification after extremity blast amputation in a Sprague-Dawley rat animal model.</a> J Orthop Trauma. 25 (8), 506-510 (2011).</li><li>Tannous, O., 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=Heterotopic+bone+formation+about+the+hip+undergoes+endochondral+ossification:+a+rabbit+model.">Heterotopic bone formation about the hip undergoes endochondral ossification: a rabbit model.</a> Clin Orthop Relat Res. 471 (5), 1584-1592 (2013).</li><li>Peterson, J. 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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Operative+release+of+ankylosis+of+the+elbow+due+to+heterotopic+ossification.+Surgical+technique.">Operative release of ankylosis of the elbow due to heterotopic ossification. Surgical technique.</a> J Bone Joint Surg Am. 86-A, 2-10 (2004).</li><li>Crane, N. J., Polfer, E., Elster, E. A., Potter, B. K., Forsberg, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raman+spectroscopic+analysis+of+combat-related+heterotopic+ossification.">Raman spectroscopic analysis of combat-related heterotopic ossification.</a> Bone. 57 (2), 335-342 (2013).</li></ol>

The authors have nothing to disclose

Heterotopic ossification represents a major functional impairment faced by patients that sustain trauma, burns, and invasive musculoskeletal procedures. The most at-risk population are soldiers in modern conflicts with major blast injuries from mechanisms such as improvised explosive devices (IED).18 Improved body armor and forward positioned medical units allows for improved survival of major extremity injury. After initial stabilization and repair of their extremity injury, these patients are at high risk...

Heterotopic ossification (HO) is the formation of ectopic bone in which osteo-potent cells are aberrantly induced to form endochondral bone outside of the skeleton. While the details of the HO formation pathway are still largely unknown, an accepted paradigm includes three key factors: an inflammatory inciting incident, a permissive niche, and mesenchymal stem cells capable of forming bone.1-3 HO is a common comorbidity complicating over 60% of major burn injuries, 65% of combat-related injuries, and 10% of invasive orthopaedic surgery cases.4,5 However, it is often difficult to predict where HO will form because it can occur at sites of local injury or at distant locations that may be otherwise uninjured. This variability in location makes it difficult to intervene prophylactically to prevent reactive bone formation in a locally targeted manner. There are also congenital forms of HO such as fibrodysplasia ossificans progressiva (FOP) in which patients are prone to the development of robust HO in response to minor trauma or inflammatory insult. Powerful animal models using transgenic mice have reproduced this phenotype and provided insight to the molecular pathways that may also be important in trauma induced HO.6-9 Translational research into the pathogenesis of non-congenital HO has used a wide variety of constructs ranging from injury alone to the implantation of exogenous osteo-inductive materials and/or cells.10-13
In our prior work we have validated a simple and reliable model of HO formation in mice which does not require the administration of any exogenous material.14-17 This model created two key conditions to initiate HO: local trauma and global inflammation. This was achieved through the use of an Achilles tenotomy (local trauma) combined with a distant burn injury (global inflammation). Mice received both treatments concurrently and were found to develop a robust amount of HO that could be analyzed by histologic, radiologic, and molecular means. Interestingly, concurrent burn injury significantly increased the amount of HO that formed and accelerated its developmental time-course.14-16 HO developed at predictable sites around the calcaneus, ankle joint, and tibia/fibula of the limb that received the tenotomy. The reliability of HO development at a known location allowed for focused examination of molecular and histologic features in the early stages of ectopic ossification.14,17 To date, 100% of mice (over 50 animals) with a tenotomy and concurrent burn injury have developed HO. Additionally, longitudinal 2D and 3D imaging and spectroscopic analysis were conducted to examine the growth pattern and biochemical make-up of HO.15,16

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>C57BL/6 mice</td>
			<td>Jackson Laboratory</td>
			<td align="right">664</td>
			<td>8-10 weeks old</td>
		</tr>
		<tr>
			<td>Isoflurane &#8211; Fluriso</td>
			<td>VET one, Boise, ID</td>
			<td>V1 501017</td>
			<td></td>
		</tr>
		<tr>
			<td>Buprenorphine &#8211; Buprenex</td>
			<td>Reckitt Benckiser Healthcare</td>
			<td>NDC 12496-0757-1</td>
			<td>0.3 mg/ml solution</td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Owens and Minor, Mechanicsville, VA</td>
			<td>2047PVP202</td>
			<td></td>
		</tr>
		<tr>
			<td>5-0 Vicryl sutures</td>
			<td>Ethicon, Summerville, NJ</td>
			<td>J493</td>
			<td></td>
		</tr>
		<tr>
			<td>Tegaderm Film, 6cm x 7cm</td>
			<td>3M</td>
			<td>1624W</td>
			<td>Cut in half to properly cover burn site</td>
		</tr>
		<tr>
			<td>&#181;CT - GE eXplore Locus SP</td>
			<td>GE Healthcare Pre-Clinical Imaging, London, ON, Canada</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microview 2.2 Advanced Bone Analysis Application</td>
			<td>GE Healthcare Pre-Clinical Imaging, London, ON, Canada</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

direct mouse trauma/burn model of heterotopic ossification

Heterotopic ossification (HO) is the formation of bone outside of the skeleton which forms following major trauma, burn injuries, and orthopaedic surgical procedures. The majority of animal models used to study HO rely on the application of exogenous substances, such as bone morphogenetic protein (BMP), exogenous cell constructs, or genetic mutations in BMP signaling. While these models are useful they do not accurately reproduce the inflammatory states that cause the majority of cases of HO. Here we describe a burn/tenotomy model in mice that reliably produces focused HO. This protocol involves creating a 30% total body surface area partial thickness contact burn on the dorsal skin as well as division of the Achilles tendon at its midpoint. Relying solely on traumatic injury to induce HO at a predictable location allows for time-course study of endochondral heterotopic bone formation from intrinsic physiologic processes and environment only. This method could prove instrumental in understanding the inflammatory and osteogenic pathways involved in trauma-induced HO. Furthermore, because HO develops in a predictable location and time-course in this model, it allows for research to improve early imaging strategies and treatment modalities to prevent HO formation.

In this present study, the protocol is described for the previously published mouse model of trauma/burn induced HO.14-17 This involves the creation of concurrent localized musculoskeletal injury with an Achilles tenotomy and global inflammatory insult with a partial thickness burn injury. This results in the reliable formation of reactive bone at the tenotomy site which can be followed with serial imaging. To date, all mice (more than 50) that have sustained both Achilles tenotomy and burn injury have develop...

Watch this Scientific Journal Video about Direct Mouse Trauma/Burn Model of Heterotopic Ossification at JoVE.com

Direct Mouse Trauma/Burn Model of Heterotopic Ossification

An Achilles tenotomy and burn injury model of heterotopic ossification allows for the reliable study of trauma induced ectopic bone formation without the application of exogenous factors.

Heterotopic ossification (HO) is the formation of bone outside of the skeleton which forms following major trauma, burn injuries, and orthopaedic surgical ...

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9.9K Views.  University of Michigan Medical School. An Achilles tenotomy and burn injury model of heterotopic ossification allows for the reliable study of trauma induced ectopic bone formation without the application of exogenous factors.

Video: Direct Mouse Trauma/Burn Model of Heterotopic Ossification

A Modified Method for Heterotopic Mouse Heart Transplantion

Mice are often used as heart transplant donors and recipients in studies of transplant immunology due to the wide range of transgenic mice and reagents available. A difficulty is presented due to the small size of the animal and the considerable technical challenges of the microsurgery involved in heart transplantation. In particular, a high rate of technical failure early after transplantation may result from recipient death and post-operative complications such as hind limb paralysis or a non-beating heart. Here, the complete technique for heterotopic mouse heart transplantation is demonstrated, involving harvesting the donor heart and its subsequent implantation into a recipient mouse. The donor heart is harvested immediately following in situ perfusion with cold heparinized saline and transection of the ascending aorta and pulmonary artery. The recipient operation involves preparation of the abdominal aorta and inferior vena cava (IVC), followed by end-to-side anastomosis of the donor aorta with the recipient aorta using a single running 10-0 microsuture and a similar anastomosis of the donor pulmonary artery with the recipient IVC. Following the operation the animal is injected with 0.6 ml normal saline subcutaneously and allowed to recover on a 37&#160;&#176;C heating pad. The results from 227 mouse heart transplants are summarized with a success rate at 48 hr of 86.8%. Of the 13.2% failures within 48 hr, 5 (2.2%) experienced hind limb paralysis, 10 (4.4%) had a non-beating heart due to graft ischemic injury and/or thrombosis, while 15 (6.6%) died within 48 hr.

A technique is demonstrated for the microsurgical procedure for heterotopic transplantation of hearts in mice, including simplified methods for donor harvesting and recipient vessel anastomosis.

Mice are often used as heart transplant donors and recipients in studies of transplant immunology due to the wide range of transgenic mice and reagents ...

Heterotopic Mucosal Engrafting Procedure for Direct Drug Delivery to the Brain in Mice

Delivery of therapeutics into the brain is impeded by the presence of the blood-brain barrier (BBB) which restricts the passage of polar and high molecular weight compounds from the bloodstream and into brain tissue. Some direct delivery success in humans has been achieved via implantation of transcranial catheters; however this method is highly invasive and associated with numerous complications. A less invasive alternative would be to dose the brain through a surgically implanted, semipermeable membrane such as the nasal mucosa that is used to repair skull base defects following endoscopic transnasal tumor removal surgery in humans. Drug transfer though this membrane would effectively bypass the BBB and diffuse directly into the brain and cerebrospinal fluid. Inspired by this approach, a surgical approach in mice was developed that uses a donor septal mucosal membrane engrafted over an extracranial surgical BBB defect. This model has been shown to effectively allow the passage of high molecular weight compounds into the brain. Since numerous drug candidates are incapable of crossing the BBB, this model is valuable for performing preclinical testing of novel therapies for neurological and psychiatric diseases.

A mouse model of human endoscopic skull base reconstruction has been developed that creates a semipermeable interface between the brain and nose using nasal mucosal grafts. This method allows researchers to study delivery to the central nervous system of high molecular weight therapeutics which are otherwise excluded by the blood-brain barrier when administered systemically.

Delivery of therapeutics into the brain is impeded by the presence of the blood-brain barrier (BBB) which restricts the passage of polar and high ...

Murine Heterotopic Heart Transplant Technique

It is now over forty years since this technique was first reported by Corry, Wynn and Russell. Although it took some years for other labs to become proficient in and utilize this technique, it is now widely used by many laboratories around the world. A significant refinement to the original technique was developed and reported in 2001 by Niimi. Described here are the techniques that have evolved over more than a decade in the hands of three surgeons (Plenter, Grazia, Pietra) in our center. These techniques are now being passed on to a younger generation of surgeons and researchers.
Based largely on the Niimi experience, the procedures used have evolved in the fine details - details which we will endeavor to relate here in such a way that others may be able to use this very useful model. Like Niimi, we have found that a video aid to learning is a priceless resource for the beginner.

The manuscript describes the steps required to perform the heterotopic heart transplant in the mouse.

It is now over forty years since this technique was first reported by Corry, Wynn and Russell. Although it took some years for other labs to become ...

Transplantation of Pulmonary Valve Using a Mouse Model of Heterotopic Heart Transplantation

Tissue engineered heart valves, especially decellularized valves, are starting to gain momentum in clinical use of reconstructive surgery with mixed results. However, the cellular and molecular mechanisms of the neotissue development, valve thickening, and stenosis development are not researched extensively. To answer the above questions, we developed a murine heterotopic heart valve transplantation model. A heart valve was harvested from a valve donor mouse and transplanted to a heart donor mouse. The heart with a new valve was transplanted heterotopically to a recipient mouse. The transplanted heart showed its own heartbeat, independent of the recipient&#8217;s heartbeat. The blood flow was quantified using a high frequency ultrasound system with a pulsed wave Doppler. The flow through the implanted pulmonary valve showed forward flow with minimal regurgitation and the peak flow was close to 100 mm/sec. This murine model of heart valve transplantation is highly versatile, so it can be modified and adapted to provide different hemodynamic environments and/or can be used with various transgenic mice to study neotissue development in a tissue engineered heart valve.

In order to understand the cellular and molecular mechanisms underlying neotissue formation and stenosis development in tissue engineered heart valves, a murine model of heterotopic heart valve transplantation was developed. A pulmonary heart valve was transplanted to recipient using the heterotopic heart transplantation technique.

Tissue engineered heart valves, especially decellularized valves, are starting to gain momentum in clinical use of reconstructive surgery with mixed ...

Heterotopic Renal Autotransplantation in a Porcine Model: A Step-by-Step Protocol

Kidney transplantation is the treatment of choice for patients suffering from end-stage renal disease. It offers better life expectancy and higher quality of life when compared to dialysis. Although the last few decades have seen major improvements in patient outcomes following kidney transplantation, the increasing shortage of available organs represents a severe problem worldwide. To expand the donor pool, marginal kidney grafts recovered from extended criteria donors (ECD) or donated after circulatory death (DCD) are now accepted for transplantation. To further improve the postoperative outcome of these marginal grafts, research must focus on new therapeutic approaches such as alternative preservation techniques, immunomodulation, gene transfer, and stem cell administration.
Experimental studies in animal models are the final step before newly developed techniques can be translated into clinical practice. Porcine kidney transplantation is an excellent model of human transplantation and allows investigation of novel approaches. The major advantage of the porcine model is its anatomical and physiological similarity to the human body, which facilitates the rapid translation of new findings to clinical trials. This article offers a surgical step-by-step protocol for an autotransplantation model and highlights key factors to ensure experimental success. Adequate pre- and postoperative housing, attentive anesthesia, and consistent surgical techniques result in favorable postoperative outcomes. Resection of the contralateral native kidney provides the opportunity to assess post-transplant graft function. The placement of venous and urinary catheters and the use of metabolic cages allow further detailed evaluation. For long-term follow-up studies and investigation of alternative graft preservation techniques, autotransplantation models are superior to allotransplantation models, as they avoid the confounding bias posed by rejection and immunosuppressive medication.

Porcine models of organ transplantation provide an important platform to study mechanisms of organ preservation. This article describes a heterotopic porcine renal autotransplantation model, which allows investigating new approaches to improve the outcome of transplantation using marginal kidney grafts.

Kidney transplantation is the treatment of choice for patients suffering from end-stage renal disease. It offers better life expectancy and higher quality ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Modified Heterotopic Hindlimb Osteomyocutaneous Flap Model in the Rat for Translational Vascularized Composite Allotransplantation Research

Vascularized composite allotransplantation (VCA) is a relatively new field in the reconstructive surgery. Clinical achievements in human VCA include hand and face transplants and, more recently, abdominal wall, uterus, and urogenital transplants. Functional outcomes have exceeded initial expectations, and most recipients enjoy an improved quality of life. However, as clinical experience accumulates, chronic rejection and complications from the immunosuppression must be addressed. In many cases where grafts have failed, the causative pathology has been ischemic vasculopathy. <span style="font-size: 11pt; line-height: 115%; font-family: Arial, sans-serif; color: rgb(41, 43, 49); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial;">The biological mechanisms of the acute and chronic rejection associated with VCA, especially ischemic vasculopathy, are important areas of research. However, due to the very small number of VCA patients, the evaluation of proposed mechanisms is better addressed in an experimental model. Multiple groups have used animal models to address some of the relevant unsolved questions in VCA rejection and vasculopathy. Several model designs involving a variety of species are described in the literature. Here we present a reproducible model of VCA heterotopic hindlimb osteomyocutaneous flap in the rat that can be utilized for translational VCA research. This model allows for the serial evaluation of the graft, including biopsies and different imaging modalities, while maintaining a low level of morbidity.

Vascularized composite allograft offers life-altering benefits to transplant recipients, but the biological causes of graft rejection and vasculopathy remain poorly understood. The rodent surgical model presented here offers a reproducible, clinically relevant model of transplantation, allowing researchers to evaluate rejection events and potential therapeutic strategies to prevent their occurrence.

Vascularized composite allotransplantation (VCA) is a relatively new field in the reconstructive surgery. Clinical achievements in human VCA include hand ...

A Mouse Model of Vascularized Heterotopic Spleen Transplantation for Studying Spleen Cell Biology and Transplant Immunity

The spleen is a unique lymphoid organ that plays a critical role in the homeostasis of the immune and hematopoietic systems. Patients that have undergone splenectomy regardless of precipitating causes are prone to develop an overwhelming post-splenectomy infection and experience increased risks of deep venous thrombosis and malignancies. Recently, epidemiological studies indicated that splenectomy might be associated with the occurrence of cardiovascular diseases, suggesting that physiological functions of the spleen have not yet been fully recognized. Here, we introduce a mouse model of vascularized heterotopic spleen transplantation, which not only can be utilized to study the function and behavioral activity of splenic immune cell subsets in different biologic processes, but also can be a powerful tool to test the therapeutic potential of spleen transplantation in certain diseases. The main surgical steps of this model include donor spleen harvest, the removal of recipient native spleen, and spleen graft revascularization. Using congenic mouse strains (e.g., mice with CD45.1/CD45.2 backgrounds), we observed that after syngeneic transplantation, both donor-derived splenic lymphocytes and myeloid cells migrated out of the graft as early as post-operative day 1, concomitant with the influx of multiple types of recipient cells, thus generating a unique chimera. &#160;Despite relatively challenging techniques, this procedure can be performed with &#62;90% success rate. This model allows tracking the fate, longevity, and function of splenocytes during steady state and in a disease setting following a spleen transplantation, thereby offering a great opportunity to discover the distinct role for spleen-derived immune cells in different disease processes.

This protocol details the surgical steps of a mouse model of vascularized heterotopic spleen transplantation, a technically challenging model that can serve as a powerful tool in studying the fate and longevity of spleen cells, the mechanisms of distinct spleen cell populations in disease progression, and transplant immunity.

The spleen is a unique lymphoid organ that plays a critical role in the homeostasis of the immune and hematopoietic systems. Patients that have undergone ...

A Simplified Model for Heterotopic Heart Valve Transplantation in Rodents

There is an urgent clinical need for heart valve replacements that can grow in children. Heart valve transplantation is proposed as a new type of transplant with the potential to deliver durable heart valves capable of somatic growth with no requirement for anticoagulation. However, the immunobiology of heart valve transplants remains unexplored, highlighting the need for animal models to study this new type of transplant. Previous rat models for heterotopic aortic valve transplantation into the abdominal aorta have been described, though they are technically challenging and costly. For addressing this challenge, a renal subcapsular transplant model was developed in rodents as a practical and more straightforward method for studying heart valve transplant immunobiology. In this model, a single aortic valve leaflet is harvested and inserted into the renal subcapsular space. The kidney is easily accessible, and the transplanted tissue is securely contained in a subcapsular space that is well vascularized and can accommodate a variety of tissue sizes. Furthermore, because a single rat can provide three donor aortic leaflets and a single kidney can provide multiple sites for transplanted tissue, fewer rats are required for a given study. Here, the transplantation technique is described, providing a significant step forward in studying the transplant immunology of heart valve transplantation.

This protocol describes a simple and efficient method for the transplantation of aortic valve leaflets under the renal capsule to allow for the study of alloreactivity of heart valves.

There is an urgent clinical need for heart valve replacements that can grow in children. Heart valve transplantation is proposed as a new type of ...

A Modified Cuff Technique for Mouse Cervical Heterotopic Heart Transplantation Model

Cardiac allograft rejection limits the long-term survival of patients after heart transplantation. A mouse heart transplantation model is ideal for investigating the mechanism of cardiac allograft rejection in preclinical studies because of their high homology with human genes. This understanding would help develop unique approaches to improving patients&#39; long-term survival treated with cardiac allografts. In a mouse model, abdominal donor heart implantation is commonly performed with an end-to-end&#160;anastomosis to the recipient&#39;s aorta and inferior vena cava using stitches. In this model, the donor&#39;s heart is implanted by end-to-end anastomosis to the recipient&#39;s carotid artery and jugular vein by the modified-Cuff technique. The transplantation surgery is performed without stitching and thus may increase the survival of the recipient since there is no interference with the blood supply and venous reflux of the lower body. This mouse model would help investigate the mechanisms underlying the immunological and pathological (acute/chronic) rejection of cardiac allografts.

In the present protocol, a mouse heart transplantation model is used for investigating the mechanism of cardiac allograft rejection. In this heterotopic heart transplantation model, operation efficiency is improved, and the survival of cardiac grafts is ensured by a cervical end-to-end anastomosis of heart implantation using a modified Cuff technique.

Cardiac allograft rejection limits the long-term survival of patients after heart transplantation. A mouse heart transplantation model is ideal for ...