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Monitoring Dendritic Cell Migration using 19F / 1H Magnetic Resonance Imaging
Published on: March 20, 2013
In-Vivo Detection and Tracking of T Cells in Various Organs in a Melanoma Tumor Model by 19F-Fluorine MRS/MRI
Christine Gonzales1, Hikari A I Yoshihara1,2, Nahzli Dilek3,4
1Division of Cardiology, Lausanne University Hospital (CHUV), Lausanne, Switzerland.
Background:
19F-MRI and 19F-MRS can identify specific cell types after in-vitro or in-vivo 19F-labeling. Knowledge on the potential to track in-vitro 19F-labeled immune cells in tumor models by 19F-MRI/MRS is scarce.
Aim:
To study 19F-based MR techniques for in-vivo tracking of adoptively transferred immune cells after in-vitro 19F-labeling, i.e. to detect and monitor their migration non-invasively in melanoma-bearing mice.
Methods:
Splenocytes (SP) were labeled in-vitro with a perfluorocarbon (PFC) and IV-injected into non-tumor bearing mice. In-vitro PFC-labeled ovalbumin (OVA)-specific T cells from the T cell receptor-transgenic line OT-1, activated with anti-CD3 and anti-CD28 antibodies (Tact) or OVA-peptide pulsed antigen presenting cells (TOVA-act), were injected into B16 OVA melanoma-bearing mice. The distribution of the 19F-labelled donor cells was determined in-vivo by 19F-MRI/MRS. In-vivo 19F-MRI/MRS results were confirmed by ex-vivo 19F-NMR and flow cytometry.
Results:
SP, Tact, and TOVA-act were successfully PFC-labeled in-vitro yielding 3x1011-1.4x1012 19F-atoms/cell in the 3 groups. Adoptively transferred 19F-labeled SP, TOVA-act, and Tact were detected by coil-localized 19F-MRS in the chest, abdomen, and left flank in most animals (corresponding to lungs, livers, and spleens, respectively, with highest signal-to-noise for SP vs TOVA-act and Tact, p<0.009 for both). SP and Tact were successfully imaged by 19F-MRI (n = 3; liver). These in-vivo data were confirmed by ex-vivo high-resolution 19F-NMR-spectroscopy. By flow cytometric analysis, however, TOVA-act tended to be more abundant versus SP and Tact (liver: p = 0.1313; lungs: p = 0.1073; spleen: p = 0.109). Unlike 19F-MRI/MRS, flow cytometry also identified transferred immune cells (SP, Tact, and TOVA-act) in the tumors.
Conclusion:
SP, Tact, and TOVA-act were successfully PFC-labeled in-vitro and detected in-vivo by non-invasive 19F-MRS/MRI in liver, lung, and spleen. The portion of 19F-labeled T cells in the adoptively transferred cell populations was insufficient for 19F-MRS/MRI detection in the tumor. While OVA-peptide-activated T cells (TOVA-act) showed highest infiltration into all organs, SP were detected more reliably by 19F-MRS/MRI, most likely explained by cell division of TOVA-act after injection, which dilutes the 19F content in the T cell-infiltrated organs. Non-dividing 19F-labeled cell species appear most promising to be tracked by 19F-MRS/MRI.
Insights
Non-dividing 19F-labeled immune cells, like splenocytes (SP), are reliably tracked in vivo using 19F-MRI/MRS in melanoma models. This technique shows promise for monitoring cell migration, but T cells require further optimization for tumor detection.
Area of Science:
- Medical Imaging
- Immunology
- Biotechnology
Background:
- 19F-MRI and 19F-MRS enable cell-type identification post-labeling.
- Limited knowledge exists on tracking in vitro 19F-labeled immune cells in tumor models using 19F-MRI/MRS.
Purpose of the Study:
- To investigate 19F-based MR techniques for in vivo tracking of adoptively transferred immune cells after in vitro 19F-labeling.
- To detect and monitor immune cell migration non-invasively in melanoma-bearing mice.
Main Methods:
- Splenocytes (SP) and T cells (Tact, TOVA-act) were labeled in vitro with perfluorocarbon (PFC).
- Labeled cells were adoptively transferred into B16 OVA melanoma-bearing mice.
- In vivo 19F-MRI/MRS tracked cell distribution, confirmed by ex vivo 19F-NMR and flow cytometry.
Main Results:
- Successful in vitro PFC labeling of SP, Tact, and TOVA-act achieved.
- In vivo 19F-MRS detected labeled SP, TOVA-act, and Tact in liver, lung, and spleen.
- 19F-MRI visualized SP and Tact in the liver; ex vivo methods confirmed in vivo findings.
- Flow cytometry indicated higher TOVA-act abundance but also detected cells within tumors, unlike 19F-MRI/MRS.
Conclusions:
- In vitro PFC-labeled SP, Tact, and TOVA-act were detected in vivo by 19F-MRS/MRI in major organs.
- Insufficient 19F labeling in T cells hindered tumor detection.
- Non-dividing 19F-labeled cells, like SP, are more suitable for 19F-MRS/MRI tracking due to consistent signal intensity.
