Background. Due to organ shortage, many patients do not receive donor organs. The present novel thrombolytic technique utilizes organs from donors with uncontrolled donation after circulatory deaths (uDCD), with up to 4–5 h warm ischemia, without advanced cardiopulmonary resuscitation (aCPR) or extracorporeal circulation (EC) after death. Methods. The study group of pigs (n = 21) underwent simulated circulatory death. After 2 h, an ice slush was inserted into the abdomen. Kidneys were retrieved 4.5 h after death. Lys-plasminogen, antithrombin-III (ATIII), and alteplase (tPA) were injected through the renal arteries on the back table. Subsequent ex vivo perfusion at 15 °C was continued for 3 h, followed by 3 h with red blood cells (RBCs) at 32 °C. Perfusion outcome and histology were compared between uDCD kidneys, receiving no thrombolytic treatment (n = 8), and live donor kidneys (n = 7). The study kidneys were then transplanted into pigs as autologous grafts with a single functioning autologous kidney as the only renal support. uDCD control pigs (n = 8), receiving no ex vivo perfusion, served as controls. Results. Vascular resistance decreased to <200 mmHg/mL/min (P < 0.0023) and arterial flow increased to >100 mL/100 g/min (P < 0.00019) compared to controls. In total 13/21 study pigs survived for >10 days, while all uDCD control pigs died. Histology was preserved after reconditioning, and the creatinine level after 10 days was next to normal. Conclusions. Kidneys from extended uDCD, not receiving aCPR/EC, can be salvaged using thrombolytic treatment to remove fibrin thrombi while preserving histology and enabling transplantation with a clinically acceptable early function.

Large animal studies of long-term ischemia reperfusion are hampered by the use of immunosuppressive drugs to inhibit the influence of the allogeneic response. In small animals, this can be controlled by using inbred strains of the animal. For obvious reasons, this is not possible in large animals such as pigs. Since studies in pigs usually are the last step before first-in-man studies, this remains a problem trying to resemble a clinical situation. In the following short paper, we describe a novel auto kidney transplantation model that can be used for long term ischemia reperfusion studies. We also suggest a control setting to balance out the possible influence of an increased surgical trauma.

Biological scaffold or implant is a popular choice for the preparation of tissue-engineered organs and has the potential to address donor shortage in the clinics. However, biological scaffolds prepared by physical or chemical agents cause damage to the extracellular matrix by potentially inducing immune responses after implantation. The current study explores an alternative route for the preparation of acellular scaffolds and explores the fate of the prepared scaffolds in a milieu of immune cells following implantation without using immunosuppressant. Using the syngeneic (Lewis male-Lewis female) and allogeneic (Brown Norway male-Lewis female) models and different tissue routes (subcutaneous vs omentum) for transplantation, normal blood vascular scaffolds were implanted which was converted to acellular vascular scaffolds by in vivo natural decellularization at the end of 2 months of observation. We also prepared chemically decellularized acellular scaffolds from normal untreated blood vascular scaffolds using a cocktail of chemicals which was also similarly placed in subcutaneous and omentum sites. Here, we applied in-depth quantitative proteomics along with histology and image analysis to comprehensively describe and compare the proteome of the natural and chemically decellularized scaffold. Our data confirm that site-specific advantages exist in modulating the ECM and regulating the immune responses (macrophage and T cells) following implantation, which possibly led to the production of an acellular scaffold (natural decellularization) under in vivo conditions. The current approach opens up the possibility to create tailor-made acellular scaffolds to build functional blood vessels. In addition, the identification of different tissue sites facilitates differential immune response against the scaffolds. This study provides a rich resource aimed toward an enhanced mechanistic understanding to study immune responses under similar settings in the field of transplantation and regenerative medicine.

M.O. participated in the research design, wrote the article, performed the research, contributed new reagents and analytical tools, and collected and analyzed the data. D.A. participated in cowriting the article, performing the research, and collecting and analyzing the data. N.B.N. participated in the performance of the research. D.B. participated in the performance of the research, collection, and analysis of the data, G.T. participated in the performance of the research, and analyzed the data. G.U.P. performed the research and collected data. M.J. participated in data analysis. D.O., M.A.B., and O.H. participated in writing the article and data analysis. J.M.S. wrote the article and analyzed the data. All the authors provided critical feedback and helped shape the research.

The development of a suitable biological scaffold or implant is a pre-requisite for the functional development of organs including blood vessels. Biological scaffold prepared by physical or chemical agents cause damage to the extracellular matrix architecture and induce immune response after scaffold implantation/engraftment. During the current study, taking advantage of different host tissue environments (subcutaneous vs omentum), acellular scaffolds/implants were prepared based on syngeneic vs allogeneic model of scaffold implantation (in vivo decellularization) and compared with chemically decellularized scaffolds. Employing molecular, proteomics, and histologic techniques, we confirmed that site-specific advantages exist in modulating the ECM as well as regulating the immune responses (macrophage and T-cells) to produce an acellular scaffold without the need for immunosuppressants. The current approach opens up the possibility to create tailor-made scaffolds for further use in the clinics with a potential for long term acceptability without eliciting adverse reactions in the host. The scaffolds prepared thus would open up a further possibility to build functional organs following cell engraftment.Impact statementDuring the current study an alternative strategy of preparing a scaffold by natural means was investigated which would also give an option to avoid the detrimental effect of chemicals used while preparing a biological scaffold. Understanding the cellular milieu of an implanted scaffold would help to modify the immunological trigger upon scaffold implantation, an aspect also studied during the current research. The infiltrating cells and their putative relationship with the biological scaffold could help the researcher to target immune cells to avoid scaffold/implant rejection. In a nutshell, the study carried out without any immunosuppressive agents could help further exploration of (a) alternative strategies for preparing biological scaffolds and (b) implantable sites as potential bioreactors with the aim to avoid any adverse immune reactions for further acceptance of the scaffold/implant post implantation.