Non-invasive magnetic resonance imaging in rats for prediction of the fate of grafted kidneys from cardiac death donors

Organ preservation solution containing dissolved hydrogen gas from a hydrogen-absorbing alloy canister improves function of transplanted ischemic kidneys in miniature pigs

Various methods have been devised to dissolve hydrogen gas in organ preservation solutions, including use of a hydrogen gas cylinder, electrolysis, or a hydrogen-generating agent. However, these methods require considerable time and effort for preparation. We investigated a practical technique for rapidly dissolving hydrogen gas in organ preservation solutions by using a canister containing hydrogen-absorbing alloy. The efficacy of hydrogen-containing organ preservation solution created by this method was tested in a miniature pig model of kidney transplantation from donors with circulatory arrest. The time required for dissolution of hydrogen gas was only 2–3 minutes. When hydrogen gas was infused into a bag containing cold ETK organ preservation solution at a pressure of 0.06 MPa and the bag was subsequently opened to the air, the dissolved hydrogen concentration remained at 1.0 mg/L or more for 4 hours. After warm ischemic injury was induced by circulatory arrest for 30 minutes, donor kidneys were harvested and perfused for 5 minutes with hydrogen-containing cold ETK solution or hydrogen-free cold ETK solution. The perfusion rate was faster from the initial stage with hydrogen-containing cold ETK solution than with hydrogen-free ETK solution. After storage of the kidney in hydrogen-free preservation solution for 1 hour before transplantation, no urine production was observed and blood flow was not detected in the transplanted kidney at sacrifice on postoperative day 6. In contrast, after storage in hydrogen-containing preservation solution for either 1 or 4 hours, urine was detected in the bladder and blood flow was confirmed in the transplanted kidney. This method of dissolving hydrogen gas in organ preservation solution is a practical technique for potentially converting damaged organs to transplantable organs that can be used safely in any clinical setting where organs are removed from donors.

Micro-vesicles derived from human Wharton's Jelly mesenchymal stromal cells mitigate renal ischemia-reperfusion injury in rats after cardiac death renal transplantation

The purpose of the present study was to investigate the possible therapeutic effects of the human Wharton-Jelly mesenchymal stromal cells derived micro-vesicles (hWJMSCs-MVs) on renal ischemia-reperfusion injury (IRI) after cardiac death (CD) renal transplantation in rats. MVs were injected intravenously in rats immediately after renal transplantation. The animals were sacrificed at 24 h, 48 h, 1 and 2 weeks post-transplantation. ELISA was used to determine the von Willebrand Factor (vWF), tumor necrosis factor (TNF)-α, and interleukin (IL)-10 levels in the serum. Tubular cell proliferation and apoptosis were identified by Ki67 immunostaining and TUNEL assay. Renal fibrosis was assessed by Masson's tri-chrome straining and alpha-smooth muscle actin (α-SMA) staining. The infiltration of inflammatory cells was detected by CD68⁺ staining. The transforming growth factor (TGF)-β, hepatocyte growth factor (HGF), and α-SMA expression in the kidney was measured by Western blot. After renal transplantation, the rats treated with hWJMSCs-MVs improved survival rate and renal function. Moreover, MVs mitigated renal cell apoptosis, enhanced proliferation, and alleviated inflammation at the first 48 h. In the late period, abrogation of renal fibrosis was observed in the MVs group. MVs also could decrease the number of CD68⁺ macrophages in the kidney. Furthermore, MVs decreased the protein expression levels of α-SMA and TGF-β1 and increased the protein expression level of HGF at any point (24 h, 48 h, 1 or 2 weeks). The administration of MVs immediately after renal transplantation could ameliorate IRI in both the acute and chronic stage.

Visualization of kidney fibrosis in diabetic nephropathy by long diffusion tensor imaging MRI with spin-echo sequence

Renal fibrosis (RF) is an indicator for progression of chronic kidney disease (CKD). Although diabetic nephropathy (DN) is the leading cause of CKD and end-stage renal disease in Western populations, the ability of MRI to evaluate RF in DN patients has not been determined. As a first step to identify possible MRI methods for RF evaluation, we examined the use of diffusion tensor imaging (DTI) MRI to evaluate RF in a rat model of DN (SHR/NDmcr-cp(cp/cp): SHR/ND). The signal-to-noise ratio in DTI MRI was enhanced using a spin-echo sequence, and a special kidney attachment was developed for long-term stabilization. The changes in renal temperature and blood flow during measurement were minimal, suggesting the feasibility of this method. At 38 weeks of age, RF had aggressively accumulated in the outer stripe (OS) of the outer medulla. FA maps showed that this method was successful in visualizing and evaluating fibrosis in the OS of the SHR/ND rat kidney (r = 0.7697, P = 0.0126). Interestingly, in the FA color maps, the directions of water molecule diffusion in RF were random, but distinct from conventional water diffusion in brain neuron fibers. These findings indicate that DTI MRI may be able to evaluate RF in CKD by DN.

Application of BOLD MRI and DTI for the evaluation of renal effect related to viscosity of iodinated contrast agent in a rat model

PURPOSE

To evaluate the effects of viscosity of contrast agent (CA) on intrarenal oxygenation and diffusion as measured by blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in a rat model.

MATERIALS AND METHODS

Radiocontrast iodixanol formulated in three viscosities were designated 270, 320, and 350 (mg iodine/mL). Sixty-three male Wistar rats were divided into four groups. Saline and iodixanol (4 g iodine/kg) were administered. MR images were acquired on a 3.0T scanner at baseline and at 1 hour, 24 hours, 48 hours, and 72 hours postinjection of solutions. BOLD-MRI was performed with a multiple gradient-recalled-echo sequence. The changes in R2*, apparent diffusion coefficient (ADC), fractional anisotropy (FA), histology, and hypoxia-inducible factor-1α (HIF-1α) immunoexpression were evaluated. The R2*, ADC, and FA values were normalized to baseline to calculate ΔR2*, ΔADC, and ΔFA.

RESULTS

Compared with baseline levels, distinct elevation of ΔR2* (P < 0.05) and obvious decrease in ΔADC (P < 0.01) and ΔFA (P < 0.05) were observed in all the anatomical compartments at 1 hour after administration of CA. The absolute values in ΔR2*, ΔADC, and ΔFA increased with increases in CA viscosity, and differed significantly between the CA groups in renal cortex (CO), outer stripe of outer medulla (OSOM), and inner stripe of outer medulla (ISOM) (all P < 0.05). A significant positive correlation was observed between ΔR2* and HIF-1α expression (P < 0.001, r = 0.75). Significant negative correlations were observed between ΔADC, ΔFA, and pathologies in CO, OSOM, ISOM (all P < 0.001, r = -0.68-0.87; all P < 0.001, r = -0.60-0.66).

CONCLUSION

The effect of CA viscosity on intrarenal oxygenation and diffusion was viscosity-dependent, and was identified using BOLD-MRI and DTI.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1320-1331.

Challenges for Production of Human Transplantable Organ Grafts

The described research methods explain how you could generate a three-dimensional kidney, based on recent research results. The first method is to fabricate human organs in a pig body. The second is to transplant the so-called "organ bud" into a patient's body for further development. The third method is to regenerate organs by filling cells into the cytoskeleton as a scaffold. Research for the in vitro fabrication of organ buds has been elaborately accelerated. The organ bud transplantation has been confronted with issues of continuity with the original organs, so the development of technology for achieving continuity between a transplanted organ bud and the existing organs is progressing well. The "organ fabrication" methodology, whereby cells are placed into completely decellularized organs, is supported by recent research results using pig organs taking the size of humans into consideration.

Impact of ex vivo administration of mesenchymal stem cells on the function of kidney grafts from cardiac death donors in rat

BACKGROUND

Mesenchymal stem cells (MSCs) have been applied to the treatment of various diseases, and MSC administration in marginal donor grafts may help avoid the ischemia-reperfusion injury associated with solid organ transplants. Given the reports of side effects after intravenous MSC administration, local MSC administration to the target organ might be a better approach. We administered adipose tissue-derived MSCs (AT-MSCs) ex vivo to donor rat kidneys obtained after cardiac death (CD).

METHODS

Using male Lewis rats (8-10 weeks), and a marginal transplant model of 1hr CD plus 1hr sub-normothermic ET-Kyoto solution preservation were conducted. AT-MSCs obtained from double-reporter (luciferase-LacZ) transgenic Lewis rats were injected either systemically (1.0 × 10(6) cells/0.5 mL) to bilaterally nephrectomized recipient rats that had received a marginal kidney graft (n = 6), or locally via the renal artery (500 μL ET-Kyoto solution containing the same number of AT-MSCs) to marginal kidney grafts, which were then preserved (1 hour; 22°C) before being transplanted into bilaterally nephrectomized recipient rats (n = 8). Serum was collected to assess the therapeutic effects of AT-MSC administration, and the recipients of rats surviving to Day 14 were separately evaluated histopathologically. Follow-up was by in vivo imaging and histological LacZ staining, and tumor formation was evaluated in MSC-injected rats at 3 months.

RESULTS

Systemic injection of MSC did not improve recipient survival. In vivo imaging showed MSCs trapped in the lung that later became undetectable. Ex vivo injection of MSCs did show a benefit without adverse effects. At Day 14 after RTx, 75% of the rats in the AT-MSC-injected group (MSC[+]) had survived, whereas 50% of the rats in the AT-MSC-non-injected group (MSC[-]) had died. Renal function in the MSC(+) group was improved compared with that in the MSC(-) group at Day 4. LacZ staining revealed AT-MSCs attached to the renal tubules at 24 hours after RTx that later became undetectable. Histopathologic examination showed little difference in fibrosis between the groups at Day 14. No teratomas or other abnormalities were seen at 3 months.