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In vivo detection of acute rat renal allograft rejection by MRI with USPIO particles
Qing Ye1, Dewen Yang, Mangay Williams
1Department of Biological Sciences, Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213-2683, USA.
Background:
Magnetic resonance imaging (MRI) for non-invasively detecting renal rejection was developed by monitoring the accumulation of macrophages labeled with dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) particles at the rat renal allografts during acute rejection.
Methods:
Five groups of male rats with DA-->BN renal allografts and one group with BN-->BN renal isografts were investigated by MRI before, immediately after, and 24 hr after intravenous infusion with different doses of USPIO particles. All infusions were done on post-operative day 4. MRI experiments were carried out in a 4.7-Tesla instrument using a gradient echo sequence.
Results:
MR signal intensity (MRSI) of the cortex was found to decrease with higher dosages of USPIO particles. In the absence of USPIO infusion, a decrease in MRSI was seen in the medulla region, presumably due to hemorrhage associated with renal graft rejection, while no significant change was observed in the cortex. The optimal dose of USPIO particles for visualizing rejection-associated changes in our rat kidney model appears to be 6 mg Fe/kg body weight. Iron staining results correlated with the MRSI data, indicating that the signal reduction in the MR images was due to the presence of iron. Immunohistochemical results indicated that USPIO particles were mostly taken up by infiltrating macrophages in the rejecting grafts.
Conclusions:
Our results suggest that MRI with intravenous administration of dextran-coated USPIO particles appears to be a valuable and promising tool that can be used as a non-invasive and sensitive method to detect graft rejection in renal transplantation.
Insights
Magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxide (USPIO) particles can non-invasively detect renal transplant rejection by tracking macrophage accumulation. This method shows promise for sensitive graft monitoring.
Area of Science:
- Biomedical Imaging
- Transplantation Immunology
- Nanotechnology
Background:
- Renal transplant rejection detection is crucial for patient outcomes.
- Current methods for monitoring rejection can be invasive.
- Developing non-invasive imaging techniques is a key research area.
Purpose of the Study:
- To evaluate the efficacy of MRI with ultrasmall superparamagnetic iron oxide (USPIO) particles for non-invasively detecting acute renal allograft rejection in a rat model.
- To determine the optimal USPIO dosage for visualizing rejection-associated changes.
Main Methods:
- Male rats with renal allografts or isografts underwent MRI before and after intravenous USPIO particle infusion.
- MRI was performed using a 4.7-Tesla instrument with a gradient echo sequence.
- Iron staining and immunohistochemistry were used to correlate MR signal changes with USPIO particle uptake by macrophages.
Main Results:
- A dose-dependent decrease in MR signal intensity (MRSI) was observed in the renal cortex with increasing USPIO dosage.
- In the absence of USPIO, decreased MRSI in the medulla suggested hemorrhage associated with rejection.
- The optimal USPIO dose for visualizing rejection was determined to be 6 mg Fe/kg, with signal reduction correlating to iron presence in macrophages.
Conclusions:
- MRI utilizing dextran-coated USPIO particles is a promising non-invasive tool for detecting renal graft rejection.
- The technique offers a sensitive method for monitoring renal transplant recipients.
- USPIO-enhanced MRI can aid in early diagnosis and management of renal allograft rejection.