Background: Heterotopic heart transplantation (HHT) in rodent animal models represents an important technique enabling studies on organ transplantation immunology and pharmaceutical development. Recent investigations used nonworking HHT designs, with the left ventricle (LV) bypassed in the anastomosis system. In spite of their principal success, the lack of orthogonal ventricular filling leads to myocardial atrophy. However, when focusing on the cellular and molecular mechanisms involved in the in vivo remodeling of the myocardium or cell-based cardiovascular implants, a nonworking model is suboptimal as it lacks the native-analogous hemodynamic and metabolic situation. Here we present the hemodynamic and electrical assessment of a biventricularly loaded murine HHT method without the need for a combined heart-lung transplantation approach. Methods: Heterotopic transplantations (n = 13) were performed on C57BL/6J-(H-2b) inbred mice (n = 13 donors, n = 13 recipients) by creating end-to-side anastomoses between the donors' cranial vena cava (CrVC) and the recipients' abdominal caudal vena cava (CVC), between the donors' ascending aorta and the recipients' abdominal aorta (aAo), and between the grafts' pulmonary trunk and the left atrium. After transplantation, a hemodynamic assessment using echocardiography (including 2D speckle tracking analysis) and electrocardiography was performed. Results: The loaded HHT procedure in the mice was performed with an overall success rate of 61%. In 3 of the remaining 5 cases, only atrial function was restored. The median duration of the entire surgical procedure for the recipient animal was 190 (IQR 180-250) min. The mean heart rate in the loaded HHT group was 355 ± 6 bpm in comparison to the control group with an in situ heart rate of 418 ± 61 bpm. A native-like closing and opening pattern of the aortic and mitral valves (visible on both 2D and M-mode images) was observed, confirming a native-analogous loading of the LV. Pulsed-wave Doppler provided visualization of the flow across the region of anastomoses between the pulmonary trunk and the left atrium, reaching a mean maximum velocity of 382 ± 12 mm/s. Exemplary 2D speckle tracking analysis of the LV free wall and interventricular septum revealed some differences in vector directions in one animal when compared to the orthotopic native heart, indicating an asynchronous movement of the LV. Conclusions: These results demonstrate the technical (micro)surgical feasibility of a fully loaded HHT procedure in the murine model without using a combined heart-lung transplantation approach. The acute hemodynamic performance of the HHT grafts approximated the native orthotopic situation. This model may open up new options for the investigation of cellular and molecular questions in the murine cardiovascular in vivo system in the near future.

1.
Fulmer RI, Cramer AT, Liebelt RA, et al: Transplantation of cardiac tissue into the mouse ear. Am J Anat 1963;113:273-285.
2.
Judd KP, Trentin JJ: Cardiac transplantation in mice. I. Factors influencing the take and survival of heterotopic grafts. Transplantation 1971;11:298-302.
3.
Hasegawa T, Visovatti SH, Hyman MC, Hayasaki T, Pinsky DJ: Heterotopic vascularized murine cardiac transplantation to study graft arteriopathy. Nat Protoc 2007;2:471-480.
4.
Corry RJ, Winn HJ, Russell PS: Primarily vascularized allografts of hearts in mice. The role of H-2D, H-2K, and non-H-2 antigens in rejection. Transplantation 1973;16:343-350.
5.
Abbott CP, Lindsey ES, Creech O Jr, et al: A technique for heart transplantation in the rat. Arch Surg 1964;89:645-652.
6.
Wang K, Zhang N, Li H: Improved technique of mouse heterotopic heart graft retransplantation. Microsurgery 2006;26:200-202.
7.
Tomita Y, Zhang QW, Uchida T, et al: A technique of cervical aortic graft transplantation in mice. J Heart Lung Transplant 2001;20:699-702.
8.
Wu YJ, Sato K, Ye Q, et al: MRI investigations of graft rejection following organ transplantation using rodent models. Methods Enzymol 2004;386:73-105.
9.
Klein I, Hong C, Schreiber SS: Cardiac atrophy in the heterotopically transplanted rat heart: in vitro protein synthesis. J Mol Cell Cardiol 1990;22:461-468.
10.
Klein I, Ojamaa K, Samarel AM, et al: Hemodynamic regulation of myosin heavy chain gene expression. Studies in the transplanted rat heart. J Clin Invest 1992;89:68-73.
11.
Maruyama T, Swartz MT, McBride LR, et al: Working heart model of heterotopic heart-lung transplantation in rats. J Thorac Cardiovasc Surg 1994;107:210-215.
12.
Asfour B, Hare JM, Kohl T, et al: A simple new model of physiologically working heterotopic rat heart transplantation provides hemodynamic performance equivalent to that of an orthotopic heart. J Heart Lung Transplant 1999;18:927-936.
13.
Klima U, Guerrero JL, Levine RA, et al: A new, biventricular working heterotopic heart transplant model: anatomic and physiologic considerations. Transplantation 1997;64:215-222.
14.
Wen P, Wang X, Wang J, et al: A simple technique for a new working heterotopic heart transplantation model in rats. Transplant Proc 2013;45:2522-2526.
15.
James IA, Yi T, Tara S, et al: Hemodynamic characterization of a mouse model for investigating the cellular and molecular mechanisms of neotissue formation in tissue-engineered heart valves. Tissue Eng Part C Methods 2015;21:987-994.
16.
Figueiredo JL, Nahrendorf M, Sosnovik DE, et al: MRI of a novel murine working heart transplant model. Circ Heart Fail 2009;2:272-274.
17.
Klein I, Hong C, Zerbe TR: Myosin content and myosin isoenzyme distribution in the heterotopic rat heart allograft. J Mol Cell Cardiol 1987;19:917-921.
18.
Klein I, Hong C, Schreiber SS: Isovolumic loading prevents atrophy of the heterotopically transplanted rat heart. Circ Res 1991;69:1421-1425.
19.
Lee YU, Yi T, James I, et al: Transplantation of pulmonary valve using a mouse model of heterotopic heart transplantation. J Vis Exp DOI: 10.3791/51695.
20.
Niimi M: The technique for heterotopic cardiac transplantation in mice: experience of 3,000 operations by one surgeon. J Heart Lung Transplant 2001;20:1123.
21.
Bauer M, Cheng S, Jain M, et al: Echocardiographic speckle-tracking based strain imaging for rapid cardiovascular phenotyping in mice. Circ Res 2011;108:908-916.
22.
Ratschiller T, Deutsch MA, Calzada-Wack J, et al: Heterotopic cervical heart transplantation in mice. J Vis Exp 2015;102:e52907.
23.
Azam S, Desjardins CL, Schluchter M, et al: Comparison of velocity vector imaging echocardiography with magnetic resonance imaging in mouse models of cardiomyopathy. Circ Cardiovasc Imaging 2012;5:776-781.
24.
Weiss RG: Imaging the murine cardiovascular system with magnetic resonance. Circ Res 2001;88:550-551.
25.
Gardner BI, Bingham SE, Allen MR, et al: Cardiac magnetic resonance versus transthoracic echocardiography for the assessment of cardiac volumes and regional function after myocardial infarction: an intrasubject comparison using simultaneous intrasubject recordings. Cardiovasc Ultrasound 2009;7:38.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.