This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs through the Congressionally Directed Medical Research Program under Award No. W81XWH-17-1-0680. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the Department of Defense.

All animals received humane care in accordance with the NIH Guide for the Care and Use of Laboratory Animals. The Institutional Animal Care and Use Committee (IACUC-protocol 2017N000184) and Animal Care and Use Review Office (ACURO) approved all animal protocols. Inbred male Lewis rats (250-400 g) were used for all experiments.
1. Surgery
<ol>
	<li>Anesthetize the Lewis rats using isoflurane inhalation. Induce anesthesia with 5% isoflurane in the induction chamber, and maintain anesthesia with 1.5-3% isoflurane inhalation through a breathing cone.</li>
	<li>Apply eye lubricant before surgery in survival procedures. Shave the surgical site, treat with depilatory cream, scrub, and drape with sterile drapes.</li>
	<li>Confirm total anesthesia with a toe pinch test before incision and regularly during the procedure. Monitor heart and respiratory rates throughout the entire procedure. For all surgeries, maintain sterile conditions by using sterile instruments, supplies, drapes, and gloves. See the Table of Materials for the list of instruments used for the procedures.</li>
</ol>
2. Donor right partial hindlimb procurement
<ol>
	<li>Make a circumferential incision of the skin above the ankle at the distal third of the leg.</li>
	<li>Skeletonize and cauterize the saphenous artery and the terminal branch of the popliteal artery using bipolar forceps. Cauterize and cut off the gastrocnemius, soleus, tibialis anterior, and biceps femoris muscles until the tibial bone is exposed.</li>
	<li>Make a 2.5 cm incision at the right inguinal crease. Dissect out the inguinal fat pad and retract it distally to expose the femoral vessels. Use a fishhook retractor to grasp the inguinal ligament and clamping forceps to hold the inguinal fat pad distally. 
	NOTE: The inguinal fat pad is included in the harvest of the partial limb.</li>
	<li>Dissect the femoral vessels, individualize Murphy branches (deep muscular collateral branches usually located halfway between the inguinal ligament and the epigastric branch), and ligate with 8-0 nylon ties.</li>
	<li>Heparinize the donor rat with 100 IU/kg heparin, injected in the penile dorsal vein using a 27.5 G needle.</li>
	<li>Complete the skin incision around the hip.</li>
	<li>Cauterize the biceps femoris and gluteus superficialis muscles using bipolar forceps. Cauterize and cut the sciatic nerve at mid femur length. Expose the femur proximally at the level of the posterior femoral crest. 
	NOTE: Adductor and quadriceps muscles are left out of the procurement. The innominate pedicle is preserved.</li>
	<li>Ligate femoral vessels with 8/0 nylon ties at the level of the inguinal ligament. Perform an arteriotomy on the femoral artery just below the ligature and dilate to allow for the insertion of a 24 G angio-catheter.</li>
	<li>Cauterize and cut remaining muscle underneath the pedicle, exposing the anterior side of the femur.</li>
	<li>Cut the tibia and femur using a bone cutter as proximally and distally as possible, respectively (mid-length).</li>
	<li>Flush the partial hindlimb with 2 mL of heparin saline (100 IU/mL) to obtain a clear venous outflow. Store on ice in a sterile gauze until microvascular transfer (Figure 1).</li>
	<li>While the animal is under general anesthesia, perform euthanasia by exsanguination.&#160;Confirm death by absence of respiratory movement and heartbeat.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62586/62586fig01.jpg" /> 
Figure 1: Rat partial hindlimb harvested. A 24 G angiocath is inserted in the femoral artery, ready for heterotopic microvascular transfer. <a href="https://www.jove.com/files/ftp_upload/62586/62586fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Recipient surgery
<ol>
	<li>Before the incision, shave the back of the neck, and administer buprenorphine 0.01-0.05 mg/kg subcutaneously. Place the rat in a supine position on a heating pad.</li>
	<li>Make a 2.5 cm incision in the right inguinal crease. Dissect the inguinal fat pad and recline it distally to expose the femoral vessels. Use a hook to retract the inguinal ligament and clamping forceps to hold the inguinal fat pad distally.</li>
	<li>Dissect the femoral vessels, individualize the Murphy branches, and ligate with 8/0 nylon ties.</li>
	<li>Ligate both vessels above the epigastric vessels using 8/0 nylon ties. Place approximator clamps proximally and dilate vessel ends; rinse with heparin saline.</li>
	<li>Make an incision on the left flank above the hip, and create a subcutaneous pocket with a subcutaneous tunnel to the inguinal crease. 
	NOTE: The inset incision is made above the range of motion of the hip to ensure that the animal maintains a normal hindlimb motion. Additionally, keeping a cutaneous bridge between the graft inset and the microvascular transfer site allows for better fixation of the graft (Figure 2).</li>
	<li>Place the proximal part of the partial limb and the inguinal fat pad through the subcutaneous tunnel for microvascular transfer. Perform venous and arterial anastomoses using 10/0 nylon sutures. Remove both approximator clamps, and observe revascularization of the limb. Perform a &#34;milking test&#34; on both vessels to assess the patency of each anastomosis. 
	NOTE: Eight to nine sutures are usually necessary for venous anastomosis, 6 sutures on average for arterial anastomosis.</li>
	<li>Make a longitudinal skin incision on the medial side of the transplanted limb, and insert the graft. Remove excess skin of the graft, and close the wound with separate sutures and a running suture using absorbable 4/0 sutures.</li>
	<li>Suture together the inguinal fat pads of the transplanted limb and the recipient using two separate absorbable sutures, and close the inguinal crease at the very end after a last checkup of the microvascular anastomoses. 
	&#8203;NOTE: Inguinal fat pads are sutured tightly to add a protective layer of fat above the anastomoses and ensure a secured position of the graft and its pedicle. A meticulous closure is better for wound healing; it also prevents residual bleeding from the wound and decreases the risk of self-mutilation.</li>
	<li>Compensate fluid loss subcutaneously with 1-3 mL of saline according to the amount of perioperative bleeding.</li>
	<li>Place an Elizabethan collar around the neck of the animal, and apply 2 loose sutures to the skin to maintain it in the correct position.</li>
	<li>Stop isoflurane inhalation, and monitor the animal continuously on a warming pad until fully conscious and ambulatory.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62586/62586fig02.jpg" /> 
Figure 2:&#160;Perioperative image before inset of the osteomyocutaneous limb. A cutaneous bridge of approximately 1 cm is preserved between the inguinal crease incision and the inset of the graft above the hip. The graft is placed under the bridge, maintaining it steady for microvascular transfer. <a href="https://www.jove.com/files/ftp_upload/62586/62586fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Postoperative care
<ol>
	<li>Monitor the animal twice daily for 72 hours, then once daily until postoperative day (POD) 7, and then twice per week. 
	NOTE: Monitoring must be adjusted to the animal and graft condition (pale eyes might require supplementary fluids, porphyrin staining as an indicator of animal pain, abnormal graft color/temperature), and further care should be discussed with the veterinarian. Single housing is required for the recipient rats during the entire study period to avoid any damage to the graft.</li>
	<li>Perform analgesia with subcutaneous injection of buprenorphine and/or non-steroid anti-inflammatory drug according to IACUC guidelines.</li>
	<li>Evaluate the graft, and perform physical examination daily with pictures using the same device. 
	NOTE: Using hair removal cream on the graft&#39;s skin is helpful to better assess the skin color of the transplant.</li>
</ol>

<ol>
	<li>Lanteiri, L., 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=Feasibility,+reproducibility,+risks+and+benefits+of+face+transplantation:+a+prospective+study+of+outcomes.">Feasibility, reproducibility, risks and benefits of face transplantation: a prospective study of outcomes.</a> American Journal of Transplantation. 11 (2), 367-378 (2011).</li><li>Park, S. H., Eun, S. C., Kwon, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand+transplantation:+current+status+and+immunologic+obstacles.">Hand transplantation: current status and immunologic obstacles.</a> Experimental and Clinical Transplantation. 17 (1), 97-104 (2019).</li><li>Cetrulo, C. L., 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=Penis+transplantation:+first+US+experience.">Penis transplantation: first US experience.</a> Annals of Surgery. 267 (5), 983-988 (2018).</li><li>Grajek, M., 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=First+complex+allotransplantation+of+neck+organs:+larynx,+trachea,+pharynx,+esophagus,+thyroid,+parathyroid+glands,+and+anterior+cervical+wall:+a+case+report.">First complex allotransplantation of neck organs: larynx, trachea, pharynx, esophagus, thyroid, parathyroid glands, and anterior cervical wall: a case report.</a> Annals of Surgery. 266 (2), 19-24 (2017).</li><li>Pribaz, J. J., Caterson, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+and+limitations+of+conventional+autologous+reconstruction+of+the+head+and+neck.">Evolution and limitations of conventional autologous reconstruction of the head and neck.</a> Journal of Craniofacial Surgery. 24 (1), 99-107 (2013).</li><li>Lipson, R. 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=Vascularized+limb+transplantation+in+the+rat.+I.+Results+with+syngeneic+grafts.">Vascularized limb transplantation in the rat. I. Results with syngeneic grafts.</a> Transplantation. 35 (4), 293-299 (1983).</li><li>Lipson, R. 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=Vascularized+limb+transplantation+in+the+rat.+II.+Results+with+allogeneic+grafts.">Vascularized limb transplantation in the rat. II. Results with allogeneic grafts.</a> Transplantation. 35 (4), 300-304 (1983).</li><li>Adamson, L. 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=A+modified+model+of+hindlimb+osteomyocutaneous+flap+for+the+study+of+tolerance+to+composite+tissue+allografts.">A modified model of hindlimb osteomyocutaneous flap for the study of tolerance to composite tissue allografts.</a> Microsurgery. 27 (7), 630-636 (2007).</li><li>Arav, A., Friedman, O., Natan, Y., Gur, E., Shani, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+hindlimb+cryopreservation+and+transplantation:+a+step+toward+"organ+banking".">Rat hindlimb cryopreservation and transplantation: a step toward "organ banking".</a> American Journal of Transplantation. 17 (11), 2820-2828 (2017).</li><li>Gok, E., 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=Development+of+an+ex-situ+limb+perfusion+system+for+a+rodent+model.">Development of an ex-situ limb perfusion system for a rodent model.</a> ASAIO Journal. 65 (2), 167-172 (2019).</li><li>Gok, E., Rojas-Pena, A., Bartlett, R. H., Ozer, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rodent+skeletal+muscle+metabolomic+changes+associated+with+static+cold+storage.">Rodent skeletal muscle metabolomic changes associated with static cold storage.</a> Transplantation Proceedings. 51 (3), 979-986 (2019).</li><li>Brandacher, G., Grahammer, J., Sucher, R., Lee, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+basic+and+translational+research+in+reconstructive+transplantation.">Animal models for basic and translational research in reconstructive transplantation.</a> Birth Defects Research. 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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterotopic+hindlimb+allotransplantation+in+rats:+an+alternative+model+for+immunological+research+in+composite-tissue+allotransplantation.">Heterotopic hindlimb allotransplantation in rats: an alternative model for immunological research in composite-tissue allotransplantation.</a> Microsurgery. 25 (5), 410-414 (2005).</li><li>Jang, Y., Park, Y. E., Yun, C. W., Kim, D. H., Chung, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+vest-collar+as+a+rodent+collar+to+prevent+licking+and+scratching+during+experiments.">The vest-collar as a rodent collar to prevent licking and scratching during experiments.</a> Lab Anim. 50 (4), 296-304 (2016).</li><li>Kern, 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+novel+rodent+orthotopic+forelimb+transplantation+model+that+allows+for+reliable+assessment+of+functional+recovery+resulting+from+nerve+regeneration.">A novel rodent orthotopic forelimb transplantation model that allows for reliable assessment of functional recovery resulting from nerve regeneration.</a> American Journal of Transplantation. 17 (3), 622-634 (2017).</li><li>Perez-Abadia, G., 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=Low-dose+immunosuppression+in+a+rat+hind-limb+transplantation+model.">Low-dose immunosuppression in a rat hind-limb transplantation model.</a> Transplant International. 16 (12), 835-842 (2003).</li><li>Sucher, 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=Orthotopic+hind-limb+transplantation+in+rats.">Orthotopic hind-limb transplantation in rats.</a> Journal of Visualized Experiments. (41), e2022 (2010).</li><li>Fleissig, Y. Y., Beare, J. E., LeBlanc, A. J., Kaufman, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+rat+hind+limb+transplant+as+an+experimental+model+of+vascularized+composite+allotransplantation:+Approaches+and+advantages.">Evolution of the rat hind limb transplant as an experimental model of vascularized composite allotransplantation: Approaches and advantages.</a> SAGE Open Medicine. 8, 2050312120968721 (2020).</li><li>Lindboe, C. F., Presthus, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+denervation,+immobilization+and+cachexia+on+fibre+size+in+the+anterior+tibial+muscle+of+the+rat.">Effects of denervation, immobilization and cachexia on fibre size in the anterior tibial muscle of the rat.</a> Acta Neuropathologica. 66 (1), 42-51 (1985).</li><li>Nazzal, J. A., Johnson, T. S., Gordon, C. R., Randolph, M. A., Lee, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterotopic+limb+allotransplantation+model+to+study+skin+rejection+in+the+rat.">Heterotopic limb allotransplantation model to study skin rejection in the rat.</a> Microsurgery. 24 (6), 448-453 (2004).</li></ol>

The authors have no disclosures.

Orthotopic limb transplantation models in rodents have been described in the literature16,17,18; however, they require a nerve repair, muscle reattachment, and a perfect osteosynthesis of the femur, which can be a very difficult step. These models are also associated with a higher morbidity and mortality rate in rodents14, especially in the short-term follow-up as the recovery of a normal function of a tr...

Over the past two decades, VCA has evolved as a revolutionary treatment for patients who suffer severe disfigurement including face1, upper limb amputations2, penile3, and other complex tissue defects4,5. However, the consequences of life-long immunosuppression still hinder a broader application of these complex reconstructive surgeries. Basic research is crucial to improve anti-rejection strategies. Increasing VCA preservation time is also essential to improve transplantation logistics and increase the donor pool (as VCA donors must fulfill more criteria than solid organ donors, including skin tone, anatomic size, gender). In this context, rat limb transplantations are widely used in studies on the immune rejection of allografts6,7, novel tolerance induction protocols8, and preservation studies9,10,11. Hence, these VCA models are a key element to master for VCA translational research.
Osteomyocutaneous flaps have been described in the literature as reliable models to study VCA in rats8,12,13,14. Although orthotopic whole-limb transplantations allow for long-term evaluation of graft function, it is a time-consuming procedure associated with higher postoperative morbidity and mortality rates14. In contrast, heterotopic limb transplantation models are non-functional, but enable reproducible studies on VCA. Postoperative outcomes can be reliably anticipated before the start of a rat VCA transplantation study. This study reports a partial heterotopic osteomyocutaneous flap transplantation model in the rat that includes frequent possible outcomes and complications that can arise intra-operatively and postoperatively during a follow-up period of three weeks.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>24 GA angiocatheter</td>
			<td>BD Insyte Autoguard</td>
			<td>381412</td>
			<td></td>
		</tr>
		<tr>
			<td>4-0 suture Black monofilament non absorbable suture</td>
			<td>Ethicon</td>
			<td>1667</td>
			<td>Used to suture the E-collar to the back of the neck</td>
		</tr>
		<tr>
			<td>4-0 suture Coated Vicryl Plus Antibacterial</td>
			<td>Ethicon</td>
			<td>VCP496</td>
			<td></td>
		</tr>
		<tr>
			<td>Adson Tissue Forceps, 11 cm, 1 x 2 Teeth with Tying Platform</td>
			<td>ASSI</td>
			<td>ASSI.ATK26426</td>
			<td></td>
		</tr>
		<tr>
			<td>Bipolar cords</td>
			<td>ASSI</td>
			<td>228000C</td>
			<td></td>
		</tr>
		<tr>
			<td>Black Polyamide Monofilament USP 10-0, 4 mm 3/8c</td>
			<td>AROSurgical</td>
			<td>T04A10N07-13</td>
			<td>Used to perform the microvascular anastomoses</td>
		</tr>
		<tr>
			<td>Buprenorphine HCl</td>
			<td>Pharmaceutical, Inc</td>
			<td>42023-179-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Dilating Forceps</td>
			<td>Fine science tools (FST)</td>
			<td>18131-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting Scissors 15 cm, Round Handle 8 mm diameter, Straight Slender Tapered Blade 7 mm, Lipshultz Pattern</td>
			<td>ASSI</td>
			<td>ASSI.SAS15RVL</td>
			<td></td>
		</tr>
		<tr>
			<td>Double Micro Clamps 5.5 x 1.5 mm</td>
			<td>Fine science tools (FST)</td>
			<td>18040-22</td>
			<td></td>
		</tr>
		<tr>
			<td>Elizabethan collar</td>
			<td>Braintree Scientific</td>
			<td>EC-R1</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps 13.5 cm long, Flat Handle, 9 mm wide Straight Tips 0.1 mm diameter (x2)</td>
			<td>ASSI</td>
			<td>ASSI.JFL31</td>
			<td></td>
		</tr>
		<tr>
			<td>Halsey Micro Needle Holder</td>
			<td>Fine science tools (FST)</td>
			<td>12500-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin Lock Flush Solution, USP, 100 units/mL</td>
			<td>BD PosiFlush</td>
			<td>306424</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Patterson Veterinary</td>
			<td>14043-704-06</td>
			<td></td>
		</tr>
		<tr>
			<td>Jewelers Bipolar Forceps Non Stick 11 cm, straight pointed tip, 0.25 mm tip diameter</td>
			<td>ASSI</td>
			<td>ASSI.BPNS11223</td>
			<td></td>
		</tr>
		<tr>
			<td>Lone Star Elastic Stays</td>
			<td>CooperSurgical</td>
			<td>3314-8G</td>
			<td>Used to retract the inguinal ligament for femoral vessels dissection</td>
		</tr>
		<tr>
			<td>Lone Star Self-Retaining Retractors</td>
			<td>CooperSurgical</td>
			<td>3301G</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-Mosquito Hemostats</td>
			<td>Fine science tools (FST)</td>
			<td>13010-12</td>
			<td>Used to retract the inguinal fat pad distally</td>
		</tr>
		<tr>
			<td>Needle Holder, 15 cm Round Handle, 8 mm diameter, Superfine Curved Jaw 0.2 mm tip diameter, without lock</td>
			<td>ASSI</td>
			<td>ASSI.B1582</td>
			<td></td>
		</tr>
		<tr>
			<td>Nylon Suture Black Monolfilament 8-0, 6.5 mm 3/8c</td>
			<td>Ethilon</td>
			<td>2808G</td>
			<td>Used to ligate collateral branches on the femoral vessels</td>
		</tr>
		<tr>
			<td>Offset Bone Nippers</td>
			<td>Fine science tools (FST)</td>
			<td>16101-10</td>
			<td></td>
		</tr>
		<tr>
			<td>S&#38;T Vascular Clamps 5.5 x 1.5 mm</td>
			<td>Fine science tools (FST)</td>
			<td>00398-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Walton scissors</td>
			<td>Fine science tools (FST)</td>
			<td>14077-09</td>
			<td></td>
		</tr>
	</tbody>
</table>

partial heterotopic hindlimb transplantation model in rats

Vascularized composite allotransplantations (VCA) represent the most advanced reconstruction option for patients without autologous surgical possibilities after a complex tissue defect. Face and hand transplantations have changed disfigured patients' lives, giving them a new aesthetic and functional social organ. Despite promising outcomes, VCA is still underperformed due to life-long immunosuppression comorbidities and infectious complications. The rat is an ideal animal model for in vivo studies investigating immunological pathways and graft rejection mechanisms. Rats are also widely used in novel composite tissue graft preservation techniques, including perfusion and cryopreservation studies. Models used for VCA in rats must be reproducible, reliable, and efficient with low postoperative morbidity and mortality. Heterotopic limb transplantation procedures fulfill these criteria and are easier to perform than orthotopic limb transplants. Mastering rodent microsurgical models requires solid experience in microsurgery and animal care. Herein is reported a reliable and reproducible model of partial heterotopic osteomyocutaneous flap transplantation in rats, the postoperative outcomes, and the means of prevention of potential complications.

In this single-operator study, 30 syngeneic heterotopic partial limb transplants were performed. Success was defined at postoperative day 21 as the absence of VCA failure or complications requiring euthanasia. The normal evolution of the graft is represented in Figure 3. The mean duration for partial limb procurement and graft inset in the recipient were 35 and 105 min, respectively; the mean ischemia time was 105 min. During follow-up, two types of complications occurred (Table 1</s...

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Partial Heterotopic Hindlimb Transplantation Model in Rats

This paper presents a partial heterotopic osteomyocutaneous flap transplantation protocol in rats and its potential outcomes in the mid-term follow-up.

Vascularized composite allotransplantations (VCA) represent the most advanced reconstruction option for patients without autologous surgical possibilities ...

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2.7K Views.  Massachusetts General Hospital, Harvard Medical School. This paper presents a partial heterotopic osteomyocutaneous flap transplantation protocol in rats and its potential outcomes in the mid-term follow-up.

Video: Partial Heterotopic Hindlimb Transplantation Model in Rats

Murine Model of CD40-activation of B cells

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand (CD40L), human B cells can be expanded without difficulties from small amounts of peripheral blood within 14 days to very large amounts of highly-pure CD40-B cells (&gt;109 cells per patient) from healthy donors as well as cancer patients1-4. CD40-B cells express important lymph node homing molecules and can attract T cells in vitro5. Furthermore they efficiently take up, process and present antigens to T cells6,7. CD40-B cells were shown to not only prime na&iacute;ve, but also expand memory T cells8,9. Therefore CD40-activated B cells (CD40-B cells) have been studied as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cell-based immunotherapy1,5,10. In order to further study whether CD40-B cells induce effective T cell responses in vivo and to study the underlying mechanism we established a cell culture system for the generation of murine CD40-activated B cells. Using splenocytes or purified B cells from C57BL/6 mice for CD40-activation, optimal conditions were identified as follows: Starting from splenocytes of C57BL/6 mice (haplotype H-2b) lymphocytes are purified by density gradient centrifugation and co-cultured with HeLa cells expressing recombinant murine CD40 ligand (tmuCD40L HeLa)11. Cells are recultured every 3-4 days and key components such as CD40L, interleukin-4, -Mercaptoethanol and cyclosporin A are replenished. In this protocol we demonstrate how to obtain fully activated murine CD40-B cells (mCD40B) with similar APC-phenotype to human CD40-B cells (Fig 1a,b). CD40-stimulation leads to a rapid outgrowth and expansion of highly pure (&gt;90%) CD19+ B cells within 14 days of cell culture (Fig 1c,d). To avoid contamination with non-transfected cells, expression of the murine CD40 ligand on the transfectants has to be controlled regularly (Fig 2). Murine CD40-activated B cells can be used to study B-cell activation and differentiation as well as to investigate their potential to function as APC in vitro and in vivo. Moreover, they represent a promising tool for establishing therapeutic or preventive vaccination against tumors and will help to answer questions regarding safety and immunogenicity of this approach12.

In this video, we demonstrate the procedure of CD40-activation and expansion of murine B cells from splenocytes of C57BL/6 mice, which can be used as a model antigen-presenting cell (APC) to study induction of immunity.

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand ...

Orthotopic Hind-Limb Transplantation in Rats

Composite tissue allotransplantation (CTA) now represents a valid therapeutic option after the loss of a hand, forearm or digits and has become a novel therapeutic entity in reconstructive surgery. However, long term high-dose multi-drug immunosuppressive therapy is required to ensure graft survival, bearing the risk of serious side effects which halters broader application. Further progression in this field may depend on better understanding of basic immunology and ischemia reperfusion injury in composite tissue grafts.
To date, orthotopic hind limb transplantation in rats has been the preferred rodent model for reconstructive transplantation (RT), however, it is an extremely demanding procedure that requires extraordinary microsurgical skills for reattachment of vasculature, bones, muscles and nerves.
We have introduced the vascular cuff anastomosis technique to this model, providing a rapid and reliable approach to rat hind limb transplantation. This technique simplifies and shortens the surgical procedure and enables surgeons with basic microsurgical experience to successfully perform the operation with high survival and low complication rates. The technique seems to be well suited for immunological as well as ischemia reperfusion injury (IRI) studies.

Here we describe the orthotopic rat hind-limb transplantation procedure, which seems to be the gold standard in vivo model for composite tissue allotransplantation research.

Composite tissue allotransplantation (CTA) now represents a valid therapeutic option after the loss of a hand, forearm or digits and has become a novel ...

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that distinguish acute and chronic inflammation in mouse models. With tissue damage or pathogen invasion, neutrophils are the first line of defense, playing a major role in mediating the acute inflammatory response. As the inflammatory reaction progresses, circulating monocytes gradually migrate into the site of injury and differentiate into mature macrophages, which mediate chronic inflammation and promote tissue repair by removing tissue debris and producing anti-inflammatory cytokines. Intraperitoneal injection of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione, sodium salt) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils. Luminol specifically reacts with the superoxide generated within the phagosomes of neutrophils since bioluminescence results from a myeloperoxidase (MPO) mediated reaction. Lucigenin (bis-N-methylacridinium nitrate) also reacts with superoxide in order to generate bioluminescence. However, lucigenin bioluminescence is independent of MPO and it solely relies on phagocyte NADPH oxidase (Phox) in macrophages during chronic inflammation. Together, luminol and lucigenin allow non-invasive visualization and longitudinal assessment of different phagocyte populations across both acute and chronic inflammatory phases. Given the important role of inflammation in a variety of human diseases, we believe this non-invasive imaging method can help investigate the differential roles of neutrophils and macrophages in a variety of pathological conditions.

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

We describe a non-invasive imaging method for distinguishing inflammatory stages. Systemic delivery of luminol reveals areas of acute inflammation dependent upon MPO activity in neutrophils. In contrast, injection of lucigenin allows for visualization of chronic inflammation dependent upon Phox activity in macrophages.

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that ...

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

A mouse model of chronic airway infection is a key asset in cystic fibrosis (CF) research, although there are a number of concerns regarding the model itself. Early phases of inflammation and infection have been widely studied by using the Pseudomonas aeruginosa agar-beads mouse model, while only few reports have focused on the long-term chronic infection in vivo. The main challenge for long term chronic infection remains the low bacterial burden by P. aeruginosa and the low percentage of infected mice weeks after challenge, indicating that bacterial cells are progressively cleared by the host.
This paper presents a method for obtaining efficient long-term chronic infection in mice. This method is based on the embedding of the P. aeruginosa clinical strains in the agar-beads in vitro, followed by intratracheal instillation in C57Bl/6NCrl mice. Bilateral lung infection is associated with several measurable read-outs including weight loss, mortality, chronic infection, and inflammatory response. The P. aeruginosa RP73 clinical strain was preferred over the PAO1 reference laboratory strain since it resulted in a comparatively lower mortality, more severe lesions, and higher chronic infection. P. aeruginosa colonization may persist in the lung for over three months. Murine lung pathology resembles that of CF patients with advanced chronic pulmonary disease.
This murine model most closely mimics the course of the human disease and can be used both for studies on the pathogenesis and for the evaluation of novel therapies.

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

We describe the agar-beads method to establish persistent long-term chronic Pseudomonas aeruginosa airway infection in the mouse model.

A mouse model of chronic airway infection is a key asset in cystic fibrosis (CF) research, although there are a number of concerns regarding the model ...

In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients

The main concern in transplantation is to achieve specific tolerance through induction of regulatory cells. The understanding of tolerance mechanisms requires reliable models. Here, we describe models of tolerance to cardiac allograft in rat, induced by blockade of costimulation signals or by upregulation of immunoregulatory molecules through gene transfer. Each of these models allowed in vivo generation of regulatory cells such as regulatory T cells (Tregs), regulatory B cells (Bregs) or regulatory myeloid cells (RegMCs). In this manuscript, we describe two complementary protocols that have been used to identify and define in vitro and in vivo regulatory cell activity to determine their responsibility in tolerance induction and maintenance. First, an in vitro suppressive assay allowed rapid identification of cells with suppressive capacity on effector immune responses in a dose dependent manner, and can be used for further analysis such as cytokine measurement or cytotoxicity. Second, the adoptive transfer of cells from a tolerant treated recipient to a newly irradiated grafted recipient, highlighted the tolerogenic properties of these cells in controlling graft directed immune responses and/or converting new regulatory cells (termed infectious tolerance). These methods are not restricted to cells with known phenotypic markers and can be extended to any cell population. Furthermore, donor directed allospecificity of regulatory cells (an important goal in the field) can be assessed by using third party donor cells or graft either in vitro or in vivo. Finally, to determine the specific tolerogenic capacity of these regulatory cells, we provide protocols to assess the humoral anti-donor antibody responses and the capacity of the recipient to develop humoral responses against new or former known antigens. The models of tolerance described can be used to further characterize regulatory cells, to identify new biomarkers, and immunoregulatory molecules, and are adaptable to other transplantation models or autoimmune diseases in rodent or human.

In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients

Here, we present a protocol to induce tolerance in transplantation, and assess in vitro and in vivo the suppressive capacity of distinct cell subsets from the recipient and the immune status of the recipient toward donor or exogenous antigens.

The main concern in transplantation is to achieve specific tolerance through induction of regulatory cells. The understanding of tolerance mechanisms ...

A Recovery Cardiopulmonary Bypass Model Without Transfusion or Inotropic Agents in Rats

Cardiopulmonary bypass (CPB) is indispensable in cardiovascular surgery. Despite the dramatic refinement of CPB technique and devices, multi-organ complications related to prolonged CPB still compromise the outcome of cardiovascular surgeries, and may worsen postoperative morbidity and mortality. Animal models recapitulating the clinical usage of CPB enable the clarification of the pathophysiological processes that occur during CPB, and facilitate pre-clinical studies to develop strategies protecting against these complications. Rat CPB models are advantageous because of their greater cost-effectiveness, convenient experimental processes, abundant testing methods at the genetic or protein levels, and genetic consistency. They can be used for investigating the immune system activation and synthesis of proinflammatory cytokines, compliment activation, and production of oxygen free radicals. The rat models have been refined and have gradually taken the place of large-animal models. Here, we describe a simple CPB model without transfusion and/or inotropic agents in a rat. This recovery model allows the study of the long-term multiple organ sequelae of CPB.

Here, we present a protocol to describe a simple recovery cardiopulmonary bypass model without transfusion or inotropic agents in a rat. This model allows the study of the long-term multiple organ sequelae of cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) is indispensable in cardiovascular surgery. Despite the dramatic refinement of CPB technique and devices, multi-organ ...

An Immunological Model for Heterotopic Heart and Cardiac Muscle Cell Transplantation in Rats

Heterotopic heart transplantation in rats has been a commonly used model for diverse immunological studies for more than 50 years. Several modifications have been reported since the first description in 1964. After 30 years of performing heterotopic heart transplantation in rats, we have developed a simplified surgical approach, which can be easily taught and performed without further surgical training or background.
After dissection of the ascending aorta and the pulmonary artery and ligation of superior and inferior caval and pulmonary veins, the donor heart is harvested and subsequently perfused with ice-cold saline solution supplemented with heparin. After clamping and incising the recipient abdominal vessels, the donor ascending aorta and pulmonary artery are anastomosed to the recipient abdominal aorta and inferior vena cava, respectively, using continuous running sutures.
Depending on different donor-recipient combinations, this model allows analyses of either acute or chronic rejection of allografts. The immunological significance of this model is further enhanced by a novel approach of in-ear injection of vital cardiac muscle cells and subsequent analysis of draining cervical lymphatic tissue.

We describe a model of heterotopic abdominal heart transplantation in rats, implying modifications of current strategies, which lead to a simplified surgical approach. Additionally, we describe a novel rejection model by in-ear injection of vital cardiac muscle cells, allowing further transplant immunological analyses in rats.

Heterotopic heart transplantation in rats has been a commonly used model for diverse immunological studies for more than 50 years. Several modifications ...

Optimization of the Cuff Technique for Murine Heart Transplantation

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to improve surgical efficiency. In our lab, we have optimized the cuff technique with two major steps. First, we used the inner tube technique to insert a temporary inner tube into the external jugular vein and carotid artery blood vessel to facilitate eversion of the vessel over the cuff. Second, we performed complete heterotopic cardiac transplantation through the collaboration of two experienced surgeons. These modifications effectively reduced the operation time to 25 minutes, with a success rate of 95%. In this report, we describe these procedures in detail and provide a supplemental video. We believe that this report on the improved cuff technique will offer practical guidance for murine heterotopic heart transplantation and will enhance the utility of this mouse model for basic research.

We introduce an inner tube approach to the cuff technique for mouse cervical heterotopic heart transplantation to help evert the vessel over the cuff. We found that cooperation between two experienced surgeons markedly shortens the operation time.

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to ...

Bone Marrow Transplantation Procedures in Mice to Study Clonal Hematopoiesis

Clonal hematopoiesis is a prevalent age-associated condition that results from the accumulation of somatic mutations in hematopoietic stem and progenitor cells (HSPCs). Mutations in driver genes, that confer cellular fitness, can lead to the development of expanding HSPC clones that increasingly give rise to progeny leukocytes harboring the somatic mutation. Because clonal hematopoiesis has been associated with heart disease, stroke, and mortality, the development of experimental systems that model these processes is key to understanding the mechanisms that underly this new risk factor. Bone marrow transplantation procedures involving myeloablative conditioning in mice, such as total-body irradiation (TBI), are commonly employed to study the role of immune cells in cardiovascular diseases. However, simultaneous damage to the bone marrow niche and other sites of interest, such as the heart and brain, is unavoidable with these procedures. Thus, our lab has developed two alternative methods to minimize or avoid possible side effects caused by TBI: 1) bone marrow transplantation with irradiation shielding and 2) adoptive BMT to non-conditioned mice. In shielded organs, the local environment is preserved allowing for the analysis of clonal hematopoiesis while the function of resident immune cells is unperturbed. In contrast, the adoptive BMT to non-conditioned mice has the additional advantage that both the local environments of the organs and the hematopoietic niche are preserved. Here, we compare three different hematopoietic cell reconstitution approaches and discuss their strengths and limitations for studies of clonal hematopoiesis in cardiovascular disease.

We describe three methods of bone marrow transplantation (BMT): BMT with total-body irradiation, BMT with shielded irradiation, and BMT method with no pre-conditioning (adoptive BMT) for the study of clonal hematopoiesis in mouse models.

Clonal hematopoiesis is a prevalent age-associated condition that results from the accumulation of somatic mutations in hematopoietic stem and progenitor ...

Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies

Invariant Natural Killer T (iNKT) cells are innate-like T Lymphocytes expressing a conserved semi-invariant T cell receptor (TCR) specific for self or microbial lipid antigens presented by the non-polymorphic MHC class I-related molecule CD1d. Preclinical and clinical studies support a role for iNKT cells in cancer, autoimmunity and infectious diseases. iNKT cells are very conserved throughout species and their investigation has been facilitated by mouse models, including CD1d-deficient or iNKT-deficient mice, and the possibility to unequivocally detect them in mice and men with CD1d tetramers or mAbs specific for the semi-invariant TCR. However, iNKT cells are rare and they need to be expanded to reach manageable numbers for any study. Because the generation of primary mouse iNKT cell line in vitro has proven difficult, we have set up a robust protocol to purify and expand splenic iNKT cells from the iV&#945;14-J&#945;18 transgenic mice (iV&#945;14Tg), in which iNKT cells are 30 times more frequent. We show here that primary splenic iV&#945;14Tg iNKT cells can be enriched through an immunomagnetic separation process, yielding about 95-98% pure iNKT cells. The purified iNKT cells are stimulated by anti-CD3/CD28 beads plus IL-2 and IL-7, resulting in 30-fold expansion by day +14 of the culture with 85-99% purity. The expanded iNKT cells can be easily genetically manipulated, providing an invaluable tool to dissect mechanisms of activation and function in vitro and, more importantly, also upon adoptive transfer in vivo.

We describe a rapid and robust protocol to enrich invariant natural killer T (iNKT) cells from mouse spleen and expand them in vitro to suitable numbers for in vitro and in vivo studies.

Invariant Natural Killer T (iNKT) cells are innate-like T Lymphocytes expressing a conserved semi-invariant T cell receptor (TCR) specific for self or ...

Partial Heterotopic Hindlimb Transplantation Model in Rats

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Murine Model of CD40-activation of B cells

Orthotopic Hind-Limb Transplantation in Rats

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients

A Recovery Cardiopulmonary Bypass Model Without Transfusion or Inotropic Agents in Rats

An Immunological Model for Heterotopic Heart and Cardiac Muscle Cell Transplantation in Rats

Optimization of the Cuff Technique for Murine Heart Transplantation

Bone Marrow Transplantation Procedures in Mice to Study Clonal Hematopoiesis

Purification and Expansion of Mouse Invariant Natural Killer T Cells for in vitro and in vivo Studies