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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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Comparison of 19F-labeled cell detection in two transplantation models over time.(A) Following implantation of 2x106 mMSC, 19F-MRI was used to quantify the number of cells remaining over 16 days. By day 16, only 2/7 mice had any detectable signal remaining. A significant difference from day 0 is denoted by +, from day 3 by ◆, and from day 9 by ■. (B) The number of detectable cells over a similar time period following a transplant of 1.5x106 hMSC. 19F signal was found to decrease at a slower rate, with observable signal in all mice at endpoint. Statistical significance is denoted in the same way as A.
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pone.0118544.g003: Comparison of 19F-labeled cell detection in two transplantation models over time.(A) Following implantation of 2x106 mMSC, 19F-MRI was used to quantify the number of cells remaining over 16 days. By day 16, only 2/7 mice had any detectable signal remaining. A significant difference from day 0 is denoted by +, from day 3 by ◆, and from day 9 by ■. (B) The number of detectable cells over a similar time period following a transplant of 1.5x106 hMSC. 19F signal was found to decrease at a slower rate, with observable signal in all mice at endpoint. Statistical significance is denoted in the same way as A.

Mentions: 19F-MRI signal was initially detectable in all mice following intramuscular injection of 2.0x106 mMSC or 1.5x106 hMSC. On day 0 quantification of the in vivo signal agreed very well with the number of implanted cells (Fig. 3). Over time the signal decreased in both models. In the immune competent model (Fig. 3A), a significant effect was observed in the decrease in 19F MRI signal over time [F(1.703,6.812) = 39.85, p<0.001]. Post hoc Tukey tests showed there was a significant difference in 19F signal between day 3 and day 9 (p<0.01), and day 9 and 16 (p<0.05). At 16 days post implantation only two mice had any detectable signal remaining. Signal in the immune-compromised mice (Fig. 3B) decreased more slowly [F(1.378,5.511) = 30.97, p<0.01], with significance from day 0 only detectable on day 17 (p<0.01). Furthermore, at this endpoint all immune-compromised mice still had detectable signal.


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

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

Comparison of 19F-labeled cell detection in two transplantation models over time.(A) Following implantation of 2x106 mMSC, 19F-MRI was used to quantify the number of cells remaining over 16 days. By day 16, only 2/7 mice had any detectable signal remaining. A significant difference from day 0 is denoted by +, from day 3 by ◆, and from day 9 by ■. (B) The number of detectable cells over a similar time period following a transplant of 1.5x106 hMSC. 19F signal was found to decrease at a slower rate, with observable signal in all mice at endpoint. Statistical significance is denoted in the same way as A.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4358825&req=5

pone.0118544.g003: Comparison of 19F-labeled cell detection in two transplantation models over time.(A) Following implantation of 2x106 mMSC, 19F-MRI was used to quantify the number of cells remaining over 16 days. By day 16, only 2/7 mice had any detectable signal remaining. A significant difference from day 0 is denoted by +, from day 3 by ◆, and from day 9 by ■. (B) The number of detectable cells over a similar time period following a transplant of 1.5x106 hMSC. 19F signal was found to decrease at a slower rate, with observable signal in all mice at endpoint. Statistical significance is denoted in the same way as A.
Mentions: 19F-MRI signal was initially detectable in all mice following intramuscular injection of 2.0x106 mMSC or 1.5x106 hMSC. On day 0 quantification of the in vivo signal agreed very well with the number of implanted cells (Fig. 3). Over time the signal decreased in both models. In the immune competent model (Fig. 3A), a significant effect was observed in the decrease in 19F MRI signal over time [F(1.703,6.812) = 39.85, p<0.001]. Post hoc Tukey tests showed there was a significant difference in 19F signal between day 3 and day 9 (p<0.01), and day 9 and 16 (p<0.05). At 16 days post implantation only two mice had any detectable signal remaining. Signal in the immune-compromised mice (Fig. 3B) decreased more slowly [F(1.378,5.511) = 30.97, p<0.01], with significance from day 0 only detectable on day 17 (p<0.01). Furthermore, at this endpoint all immune-compromised mice still had detectable signal.

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