A new approach for noninvasive assessment of chronic cardiac allograft rejection in rat by cellular...
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BioMed Central Page 1 of 2 (page number not for citation purposes) Journal of Cardiovascular Magnetic Resonance Open Access Poster presentation A new approach for noninvasive assessment of chronic cardiac allograft rejection in rat by cellular cardiac MRI Qing Ye*, Yijen L Wu, lesley M Foley, T Kevin Hitchens, Danielle Eytan and Chien Ho Address: Pittsburgh NMR center for biomedical research, Pittsburgh, PA, USA * Corresponding author Introduction Long-term cardiac transplant survival rates can be improved only if patients undergo proper monitoring and treatment after transplantation. Repetitive endomyocar- dial biopsy, the gold standard for monitoring rejection status, is not only invasive but is also prone to sampling errors because of the limited size and location of graft tis- sue available. We have developed cellular and functional MRI techniques as a non-invasive method to detect and stage acute cardiac allograft rejection. Our recent studies indicate that macrophages can be detected by MRI in our rat model of CCAR. Therefore, we seek to develop CCMRI for non-invasive evaluation of CCAR. Purpose The aim of this study was to investigate the feasibility of using cellular cardiac MRI (CCMRI) for the non-invasive assessment of chronic cardiac allograft rejection (CCAR) in real time using a rat model. Methods An abdominal heterotopic working heart rat model was used in this study. Immune cells (mainly macrophages) were in-situ labeled by direct i.v. injection of micrometer- sized paramagnetic iron oxide (MPIO) particles one day prior to initial in-vivo MRI. EKG- and respiratory-gated CCMRI were used to longitudinally monitor the accumu- lation of MPIO-labeled macrophages in the graft at 4.7 Tesla for up to 120 days. Grafts were then harvested and fixed for high-resolution 3D magnetic resonance micros- copy (MRM) at 11.7 Tesla. Fluorescence microscopy for dragon-green co-labeled MPIO and pathology were used to verify the in-vivo CCMRI and MRM results. Results The status of CCAR can be assessed longitudinally by monitoring macrophage infiltration associated with CCAR by CCMRI with a single MPIO injection (Fig. 1A- C). Labeled macrophages appeared as dark spots on T 2 *- weighted images and the location and distribution of labeled macrophages can be easily mapped with high-res- olution 3D-MRM (Fig. 1D-F). Co-registered MRM and flu- orescence micrographs confirm that these dark spots are caused by the MPIO particles (Fig. 1G). The number of dark spots correlates with the severity of chronic rejection (Fig. 2A&2B and 2E&2F). Pathology of the corresponding tissue sections confirmed the result (mild rejection: Figs. 2C&2D, severe rejection: Figs. 2G&2H). Conclusion Macrophage infiltration to the heart graft experiencing CCAR can be serially monitored by MRI following a single i.v. injection of MPIO. Furthermore, the observed increase in MPIO-labeled macrophages correlates with the severity of CCAR and this method provides a non-invasive, real- time and whole-heart assessment of rejection. This study demonstrates the feasibility of non-invasive assessment of CCAR which has great potential in clinical applications. from 13th Annual SCMR Scientific Sessions Phoenix, AZ, USA. 21-24 January 2010 Published: 21 January 2010 Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):P255 doi:10.1186/1532-429X-12-S1-P255 <supplement> <title> <p>Abstracts of the 13<sup>th </sup>Annual SCMR Scientific Sessions - 2010</p> </title> <note>Meeting abstracts - A single PDF containing all abstracts in this Supplement is available <a href="http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-full.pdf">here</a>.</note> <url>http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-info</url> </supplement> This abstract is available from: http://jcmr-online.com/content/12/S1/P255 © 2010 Ye et al; licensee BioMed Central Ltd.
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Journal of Cardiovascular Magnetic Resonance
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Open AccePoster presentationA new approach for noninvasive assessment of chronic cardiac allograft rejection in rat by cellular cardiac MRIQing Ye*, Yijen L Wu, lesley M Foley, T Kevin Hitchens, Danielle Eytan and Chien HoAddress: Pittsburgh NMR center for biomedical research, Pittsburgh, PA, USA
* Corresponding author
IntroductionLong-term cardiac transplant survival rates can beimproved only if patients undergo proper monitoring andtreatment after transplantation. Repetitive endomyocar-dial biopsy, the gold standard for monitoring rejectionstatus, is not only invasive but is also prone to samplingerrors because of the limited size and location of graft tis-sue available. We have developed cellular and functionalMRI techniques as a non-invasive method to detect andstage acute cardiac allograft rejection. Our recent studiesindicate that macrophages can be detected by MRI in ourrat model of CCAR. Therefore, we seek to develop CCMRIfor non-invasive evaluation of CCAR.
PurposeThe aim of this study was to investigate the feasibility ofusing cellular cardiac MRI (CCMRI) for the non-invasiveassessment of chronic cardiac allograft rejection (CCAR)in real time using a rat model.
MethodsAn abdominal heterotopic working heart rat model wasused in this study. Immune cells (mainly macrophages)were in-situ labeled by direct i.v. injection of micrometer-sized paramagnetic iron oxide (MPIO) particles one dayprior to initial in-vivo MRI. EKG- and respiratory-gatedCCMRI were used to longitudinally monitor the accumu-lation of MPIO-labeled macrophages in the graft at 4.7Tesla for up to 120 days. Grafts were then harvested andfixed for high-resolution 3D magnetic resonance micros-
copy (MRM) at 11.7 Tesla. Fluorescence microscopy fordragon-green co-labeled MPIO and pathology were usedto verify the in-vivo CCMRI and MRM results.
ResultsThe status of CCAR can be assessed longitudinally bymonitoring macrophage infiltration associated withCCAR by CCMRI with a single MPIO injection (Fig. 1A-C). Labeled macrophages appeared as dark spots on T2*-weighted images and the location and distribution oflabeled macrophages can be easily mapped with high-res-olution 3D-MRM (Fig. 1D-F). Co-registered MRM and flu-orescence micrographs confirm that these dark spots arecaused by the MPIO particles (Fig. 1G). The number ofdark spots correlates with the severity of chronic rejection(Fig. 2A&2B and 2E&2F). Pathology of the correspondingtissue sections confirmed the result (mild rejection: Figs.2C&2D, severe rejection: Figs. 2G&2H).
ConclusionMacrophage infiltration to the heart graft experiencingCCAR can be serially monitored by MRI following a singlei.v. injection of MPIO. Furthermore, the observed increasein MPIO-labeled macrophages correlates with the severityof CCAR and this method provides a non-invasive, real-time and whole-heart assessment of rejection. This studydemonstrates the feasibility of non-invasive assessment ofCCAR which has great potential in clinical applications.
from 13th Annual SCMR Scientific SessionsPhoenix, AZ, USA. 21-24 January 2010
Published: 21 January 2010
Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):P255 doi:10.1186/1532-429X-12-S1-P255
<supplement> <title> <p>Abstracts of the 13<sup>th </sup>Annual SCMR Scientific Sessions - 2010</p> </title> <note>Meeting abstracts - A single PDF containing all abstracts in this Supplement is available <a href="http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-full.pdf">here</a>.</note> <url>http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-info</url> </supplement>
This abstract is available from: http://jcmr-online.com/content/12/S1/P255
© 2010 Ye et al; licensee BioMed Central Ltd.
Page 1 of 2(page number not for citation purposes)
Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):P255 http://jcmr-online.com/content/12/S1/P255
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T2* - weighted in vivo CCMR at 4.7 Tesla show monitored macrophages infiltration associated with CCAR progression on Post-operative days 14, 77, and 96 (A-C) respectively)Figure 1T2* - weighted in vivo CCMR at 4.7 Tesla show monitored macrophages infiltration associated with CCAR pro-gression on Post-operative days 14, 77, and 96 (A-C) respectively). The MPIO-labeled macrophage infiltration foci, appear as dark spots of hypointensity (arros) are confirmed with ex vivo high-resolution 3D MRM at 11.7 T (D, F), 3D render-ing provides a whole-heart perspective of rejection and reaveals that macrophage infiltration during CCAR is heterogeneous. Fluorescence in microscopy confirms that thes dark spots are caused by MPIO-labeled macrophages (G, dragon green fluores-cence).
Top row shows images from allograft with mild CCAR (A-D), the bottom row shows images of an allograft with severe CCAR (E-H)Figure 2Top row shows images from allograft with mild CCAR (A-D), the bottom row shows images of an allograft with severe CCAR (E-H). A few spots of hypointensity can be seen in T2* weighted in vivo CCMRI (A) resulting from labeled macrophage infiltration in different regions of the allograft experiecnin mild rejection. There are a larger number of dark spots detected in the severly reject-ing allograft (E). These dark spots were confirmed by MRM at 11.7 T (B and F). The corresponding tissue sections stating with anti-rat EDI antibody (C and G) were used to confirm macrophage infiltration. The H&£ staining indicated a mild rejecting allograft graft (D) has less CCAR dchanges. The more concentrated macrophage accumulated in the enc-docardium, adventitita, and severe intimal thickening in the severly rejecting allograft.
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