Flow-controlled fluoroscopic angiography for the assessment of vascular integrity in bioengineered kidneys.

Perfusion decellularization has been proposed as a promising method for generating nonimmunogenic organs from allogeneic or xenogeneic donors. Several imaging modalities have been used to assess vascular integrity in bioengineered organs with no consistency in the methodology used. Here, we studied the use of fluoroscopic angiography performed under controlled flow conditions for vascular integrity assessment in bioengineered kidneys. Porcine kidneys underwent ex vivo angiography before and after perfusion decellularization. Arterial and venous patencies were defined as visualization of contrast medium (CM) in distal capillaries and renal vein, respectively. Changes in vascular permeability were visualized and quantified. No differences in patency were detected in decellularized kidneys compared with native kidneys. However, focal parenchymal opacities and significant delay in CM clearance were detected in decellularized kidneys, indicating increased permeability. Biopsy-induced leakage was visualized in both groups, with digital subtraction angiography revealing minimal CM leakage earlier than nonsubtracted fluoroscopy. In summary, quantitative assessment of vascular permeability should be coupled with patency when studying the effect of perfusion decellularization on kidney vasculature. Flow-controlled angiography should be considered as the method of choice for vascular assessment in bioengineered kidneys. Adopting this methodology for organs premodified ex vivo under normothermic machine perfusion settings is also suggested.

The Role of Early Sequential Biopsies in Delayed Renal Graft Function of Transplanted Kidney Is Reduced in Modern Immunosuppression Era.

BACKGROUND: Delayed graft function (DGF) immediately after kidney transplantation is considered a risk factor for acute rejection. According to clinical guidelines, a weekly allograft biopsy should be performed until DGF resolves. Based on clinical evidence, the first biopsy is considered appropriate. However, the recommendation for further biopsies is based on sparse evidence from era of earlier immunosuppression protocols, and the benefit of the second and further biopsies remains uncertain. The aim of this study was to reevaluate this policy. METHODS: The database of a transplant medical center was retrospectively reviewed for all patients who underwent kidney transplantation in 2011-2020. Those with DGF who performed two or more graft biopsies within the first 60 days after transplantation were identified. Clinical data were collected from the medical files. The rates of diagnosis of acute rejection at the second and subsequent biopsies were analyzed relative to the previous ones. RESULTS: Kidney transplantation was performed in 1,722 patients during the study period, of whom 225 (13.07%) underwent a total of 351 graft biopsies within 60 days after transplantation, mostly due to DGF. A second biopsy was performed in 32 patients (14.2%), and a third biopsy in 8, at weekly intervals. In 2 patients (6.25%), the diagnosis changed from the first biopsy (acute tubular necrosis or toxic damage) to acute rejection in the second biopsy. In both, the rejection was borderline. Third and fourth biopsies did not add information to the previous diagnosis. CONCLUSIONS: The common practice of performing sequential biopsies during a postoperative course of DGF seems to be of low benefit and should be considered on a case-by-case basis.

Generation of vascular chimerism within donor organs.

Whole organ perfusion decellularization has been proposed as a promising method to generate non-immunogenic organs from allogeneic and xenogeneic donors. However, the ability to recellularize organ scaffolds with multiple patient-specific cells in a spatially controlled manner remains challenging. Here, we propose that replacing donor endothelial cells alone, while keeping the rest of the organ viable and functional, is more technically feasible, and may offer a significant shortcut in the efforts to engineer transplantable organs. Vascular decellularization was achieved ex vivo, under controlled machine perfusion conditions, in various rat and porcine organs, including the kidneys, liver, lungs, heart, aorta, hind limbs, and pancreas. In addition, vascular decellularization of selected organs was performed in situ, within the donor body, achieving better control over the perfusion process. Human placenta-derived endothelial progenitor cells (EPCs) were used as immunologically-acceptable human cells to repopulate the luminal surface of de-endothelialized aorta (in vitro), kidneys, lungs and hind limbs (ex vivo). This study provides evidence that artificially generating vascular chimerism is feasible and could potentially pave the way for crossing the immunological barrier to xenotransplantation, as well as reducing the immunological burden of allogeneic grafts.