Development of a Vascularized Heterotopic Neonatal Rat Heart Transplantation Model

Abstract

Background/Purpose: Rodent adult-to-adult heterotopic heart transplantation is a well-established animal model, and the detailed surgical technique with several modifications has been previously described. In immature donor organ transplantation, however, the surgical technique needs to be revised given the smaller size and fragility of the donor graft. Here, we report our surgical technique for heterotopic abdominal (AHTx) and femoral (FHTx) neonatal rat heart transplantation based on an experience of over 300 cases. Methods: Heterotopic heart transplantation was conducted in syngeneic Lewis rats. Neonatal rats (postnatal day 2-4) served as donors. AHTx was performed by utilizing the conventional adult-to-adult transplant method with specific modifications for optimal aortotomy and venous anastomosis. In the FHTx, the donor heart was vascularized by connecting the donor's aorta and pulmonary artery to the recipient's right femoral artery and vein, respectively, in an end-to-end manner. A specifically fashioned butterfly-shaped rubber sheet was used to align the target vessels properly. The transplanted graft was visually assessed for its viability and was accepted as a technical success when the viability met specific criteria. Successfully transplanted grafts were subject to further postoperative evaluation. Forty cases (AHTx and FHTx; n = 20 each) were compared regarding perioperative parameters and outcomes. Results: Both models were technically feasible (success rate: AHTx 75% vs. FHTx 70%) by refining the conventional heterotopic transplant technique. Injury to the fragile donor aorta and congestion of the graft due to suboptimal venous connection were predominant causes of failure, leading to refractory bleeding and poor graft viability. Although the FHTx required significantly longer operation time and graft ischemic time, the in situ graft viabilities were comparable. The FHTx provided better postoperative monitoring as it enabled daily graft palpation and better echocardiographic visualization. Conclusions: We describe detailed surgical techniques for AHTx and FHTx while addressing neonatal donor-specific issues. Following our recommendations potentially reduces the learning curve to achieve reliable and reproducible results with these challenging animal models.

Abnormal Flow Conditions Promote Endocardial Fibroelastosis Via Endothelial-to-Mesenchymal Transition, Which Is Responsive to Losartan Treatment

“…Neonatal heterotopic heart transplantation has been developed as an animal model of EFE formation ( 20 , 21 ). These transplanted hearts undergo EndoMT and subsequent EFE development, presumably from the lack of normal blood flow through the LV.…”

“…Previous work has used neonatal heterotopic heart transplantation in rodents to study EFE development ( 20 , 21 ). Although flow dynamics in the LV, absence of flow, and LV distension have all been postulated as triggers for EFE development in this model, solid evidence has not been substantiated ( 12 ).…”

“…First, in the regurgitant flow group, the regurgitant flow tends to distend the LV. Distension of the LV has been described clinically and in research to contribute to cardiac dysfunction and fibrosis ( 21 ). However, although ventricular distension should be considered a factor, literature also suggests that flow promotes fibrosis in the cardiovascular system, similar to our results, and its influence should not be considered insignificant.…”

“…Heterotopic heart transplantation was performed in Lewis rats using techniques previously described ( 20 , 21 ). In brief, donor hearts were obtained from neonatal rats (2 to 4 days of age) and were transplanted in young adult male rats (weighing 100 to 120 g) (n = 5 per group).…”