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Tracking the fate of stem cell implants with fluorine-19 MRI.

Gaudet JM, Ribot EJ, Chen Y, Gilbert KM, Foster PJ - PLoS ONE (2015)

Bottom Line: The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model.In the xenograft model, all mice had detectable signal at endpoint.However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.

View Article: PubMed Central - PubMed

Affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.

ABSTRACT

Background: In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (19F) agent. 19F-MRI offers unambiguous detection and in vivo quantification of labeled cells.

Methods: We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. 19F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using 19F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty.

Results: Immediately following transplantation, 19F-MRI quantification correlated very well with the expected cell number in both models. The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model. By endpoint, only 2/7 syngeneic mice had any detectable 19F signal. In the xenograft model, all mice had detectable signal at endpoint. Fluorescence microscopy and immunohistochemistry were used to show that the 19F signal was related to the presence of bystander labeled macrophages, and not original MSC.

Conclusions: Our results show that 19F-MRI is an excellent tool for verifying the delivery of therapeutic cells early after transplantation. However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.

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Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.(A, E) Representative MRI from mice receiving either 2x106 mMSC or 1.5x106 hMSC respectively. The day 0 in vivo19F-MRI quantification correlates very well with the number of implanted cells. The reference tube is marked by “R”. (B) The red fluorescent fluorine agent is clearly visible in the tissue of the immune competent model, (F) as well as in the immune-compromised model. (C) Furthermore, the GFP+ mMSC are observable within the tissue section. (D) Overlaying the two fluorescent images, reveals the 19F agent colocalized with the GFP+ mMSC, as expected. (G, H) H&E stained tissue sections corresponding to the fluorescence microscopy clearly show the implant site of the mMSC and hMSC respectively. Scale bars in all images represent 250μm.
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pone.0118544.g004: Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.(A, E) Representative MRI from mice receiving either 2x106 mMSC or 1.5x106 hMSC respectively. The day 0 in vivo19F-MRI quantification correlates very well with the number of implanted cells. The reference tube is marked by “R”. (B) The red fluorescent fluorine agent is clearly visible in the tissue of the immune competent model, (F) as well as in the immune-compromised model. (C) Furthermore, the GFP+ mMSC are observable within the tissue section. (D) Overlaying the two fluorescent images, reveals the 19F agent colocalized with the GFP+ mMSC, as expected. (G, H) H&E stained tissue sections corresponding to the fluorescence microscopy clearly show the implant site of the mMSC and hMSC respectively. Scale bars in all images represent 250μm.

Mentions: Representative MR image data, fluorescence microscopy, and H&E obtained on day 0 is shown in Fig. 4. Overlays of the 19F MRI onto the proton image at day 0 are show in 4A and E for the immune competent and immune compromised mice respectively. Fig. 4B and F show that the red fluorescence signal from the 19F labeling agent can be detected on day 0 in both models. The green fluorescence associated with the GFP+ mMSC was also clearly visible at the site of their implantation on day 0 (Fig. 4C). Overlaying the two fluorescent images revealed strong co-localization, with a Pearson’s correlation coefficient of 0.80, between the red fluorescent 19F agent and the GFP+ mMSC in Fig. 4D. The corresponding H&E stained tissue sections reveal the location of the implant within the muscle (Fig. 4G,H).


Tracking the fate of stem cell implants with fluorine-19 MRI.

Gaudet JM, Ribot EJ, Chen Y, Gilbert KM, Foster PJ - PLoS ONE (2015)

Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.(A, E) Representative MRI from mice receiving either 2x106 mMSC or 1.5x106 hMSC respectively. The day 0 in vivo19F-MRI quantification correlates very well with the number of implanted cells. The reference tube is marked by “R”. (B) The red fluorescent fluorine agent is clearly visible in the tissue of the immune competent model, (F) as well as in the immune-compromised model. (C) Furthermore, the GFP+ mMSC are observable within the tissue section. (D) Overlaying the two fluorescent images, reveals the 19F agent colocalized with the GFP+ mMSC, as expected. (G, H) H&E stained tissue sections corresponding to the fluorescence microscopy clearly show the implant site of the mMSC and hMSC respectively. Scale bars in all images represent 250μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4358825&req=5

pone.0118544.g004: Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.(A, E) Representative MRI from mice receiving either 2x106 mMSC or 1.5x106 hMSC respectively. The day 0 in vivo19F-MRI quantification correlates very well with the number of implanted cells. The reference tube is marked by “R”. (B) The red fluorescent fluorine agent is clearly visible in the tissue of the immune competent model, (F) as well as in the immune-compromised model. (C) Furthermore, the GFP+ mMSC are observable within the tissue section. (D) Overlaying the two fluorescent images, reveals the 19F agent colocalized with the GFP+ mMSC, as expected. (G, H) H&E stained tissue sections corresponding to the fluorescence microscopy clearly show the implant site of the mMSC and hMSC respectively. Scale bars in all images represent 250μm.
Mentions: Representative MR image data, fluorescence microscopy, and H&E obtained on day 0 is shown in Fig. 4. Overlays of the 19F MRI onto the proton image at day 0 are show in 4A and E for the immune competent and immune compromised mice respectively. Fig. 4B and F show that the red fluorescence signal from the 19F labeling agent can be detected on day 0 in both models. The green fluorescence associated with the GFP+ mMSC was also clearly visible at the site of their implantation on day 0 (Fig. 4C). Overlaying the two fluorescent images revealed strong co-localization, with a Pearson’s correlation coefficient of 0.80, between the red fluorescent 19F agent and the GFP+ mMSC in Fig. 4D. The corresponding H&E stained tissue sections reveal the location of the implant within the muscle (Fig. 4G,H).

Bottom Line: The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model.In the xenograft model, all mice had detectable signal at endpoint.However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.

View Article: PubMed Central - PubMed

Affiliation: Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, University of Western Ontario, London, ON, Canada.

ABSTRACT

Background: In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (19F) agent. 19F-MRI offers unambiguous detection and in vivo quantification of labeled cells.

Methods: We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. 19F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using 19F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty.

Results: Immediately following transplantation, 19F-MRI quantification correlated very well with the expected cell number in both models. The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model. By endpoint, only 2/7 syngeneic mice had any detectable 19F signal. In the xenograft model, all mice had detectable signal at endpoint. Fluorescence microscopy and immunohistochemistry were used to show that the 19F signal was related to the presence of bystander labeled macrophages, and not original MSC.

Conclusions: Our results show that 19F-MRI is an excellent tool for verifying the delivery of therapeutic cells early after transplantation. However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.

Show MeSH
Related in: MedlinePlus