A Model Of Simultaneous Heart And Composite Tissue Allotransplant In Small Animal

Background Solid organ transplantation(SOT)has been relatively conventional lifesaving set of procedures in the case of organ failure.But it's difficult to achieve wounds closure in some of SOT patients because of trauma,multiple surgery procedure,infection,tumor,tissue edema,and size mismatch.Composite tissue allotransplantation(CTA)aiming at replacing tissue defects in patients for whom no other satisfactory reconstructive options are available has achieved wonderful results in recent decades.But widespread application of clinical CTA is hampered because there are still arguments that the risk of long term adverse effects of immunosuppression does not outweigh the benefits of nonlife-saving CTA.Most SOT patients are already receiving therapeutic immunosuppression,so the combination of CTA and SOT may be a novel,effective and acceptable way to solve the aforementioned tough problems,which has been demonstrated clinically in small intestine and other solid organ transplantation.However,the question still remains unsolved whether CTA and SOT will affect each other in immune rejection if they are performed simultaneously.In CTA,skin seems to be the most susceptible to rejection,and it's possible that skin will accelerate rejection of other tissue by activating host's immune system or by generating local inflammation.Conversely,solid organ allografts are more easily accepted and some grafts like liver or kidney even are able to induce acceptance of and in some cases tolerance to other coexistent allografts.Besides,early diagnosis of immune rejection of SCT is difficult because,which may lead to graft loss or chronic immune rejection.In contrast,most composite tissue is located outside body,which makes it convenient to observe and take sample,so there's a need to find out whether composite tissue could act as �sentinel flap� to diagnose early rejection of solid organ.Therefore,there's necessity to build an animal model of co-transplant of solid organ and composite tissue.Many SOT animal models have been created,such as heart,liver,pancreas,and small intestine and so on,which have greatly improved our understanding of organ transplantation immunity.In recent decades,as the clinical application of composite tissue transplantation rises,many kinds of animal model of composite tissue transplant emerge,most of which are in rats.However,there's seldom to unite both CTA and SOT perhaps because of difficult techniques.Here,we succeed to create a novel model of simultaneous heart and composite tissue transplant in mice making use of the special anatomy of heart and nonsuture cuff technique.We believe that this model would promote relevant research of how composite tissue and solid organ transplant influence each other,and split rejection between them.Objective:We aimed to develop a model of concomitant heart and composite tissue transplant in mice,which could be used to evaluate the possible effects between simultaneous CTA and SOT.Methods: 1.Heart transplantation model was built.The donor heart was transplanted to the recipient neck,the donor heart�s' aorta and the pulmonary artery are connected to the recipient's right common carotid artery and right external jugular vein The flap graft model was to transplant the donor inguinal flap into the recipient neck,which was anastomosed with the right common carotid artery and the external jugular vein.Using the same dose of immunosuppressive agents,the transplanted heart and flap was observed.2.Animals were divided into 4 groups: group A was the anatomic study group,in which anatomic dissections were performed to clarify vascular anatomy of heart and abdominal skin graft.In group B,sham-surgery were conducted the same operation as recipients in the transplant group without receiving any grafts to assess the influence of the surgery.In group C,the donor's heart and flap were both transplanted to recipient neck.Donor's heart was harvested with right common carotid artery,then the aorta and pulmonary artery were anastomosed to the recipient's common carotid artery and right external jugular vein,and abdominal flap vessels was connected to the donor's right common carotid artery and recipient's left external jugular vein respectively.In group D,the donor's heart was transplanted to recipient neck,and the donor's flap graft was transplanted to the donor's inguinal region simultaneously.Isograft transplants were performed between C57BL/6 mouse.The surgical procedures were performed by the same surgeon with a microscope and microsurgical instruments.The heart viability was assessed by daily palpation,and the skin flap was observed every day,the vessel patency was checked and the grafts were assessed histologically at last.Graft death before day 3 after transplantation was considered as a technical failure.Results: 1.Flaps and hearts have different patterns of rejection.2.Ligating both sides of external jugular vein and one side of common carotid artery has no harm to C57BL/6(H-2b)mouse.The observation for one month showed that the animals were in good condition,walked around freely,reacted well.Their hair was bright and head didn't develop edema.Their weight dropped in the first week up to about 10%,then gradually rise to the level before the surgery.We didn't find any obvious change after ligating both sides of external jugular vein and one side of common carotid artery.3.Operation time of simultaneous heart and composite tissue allotransplant model in neck was decreased according to the number of operations and the mean total operative time was 193.6�7.8min per operation with recipient operation 87.6�6.3 min.Indefinite allograft survival(>100days)was achieved in isograft transplant group.When the animals were euthanized at day 100 posttransplantation,the cervical region of the recipient was explored and the vascular anastomoses were patent with much angiogenesis.Histologic examination displayed viable grafts without necrosis or fibrosis.Conclusions: We succeed to develop a technically feasible and reliable model of simultaneous heart and composite tissue transplant in mice.This model may be used in research of possible mutual immunologic influence and split rejection between composite tissue and solid organ.