<i>In vitro</i> validation of ¹⁹F-MRI quantification accuracy.

<p>Quantification was validated in a phantom study using cell pellets ranging from 2x10⁵ to 2x10⁶ MSC. Pellets were imaged three times, with the error bars representing the standard deviation between scans. The ¹⁹F-MRI quantification is in very strong agreement with the true number of cells, and has a Pearson correlation coefficient of 0.99. The red line represents the ideal result of a 1:1 correlation.</p

Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.

<p>(A, E) Representative MRI from mice receiving either 2x10⁶ mMSC or 1.5x10⁶ hMSC respectively. The day 0 <i>in vivo</i>¹⁹F-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.</p

Comparison of ¹⁹F-labeled cell detection in two transplantation models over time.

<p>(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 <b>+</b>, 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.</p

Cellular viability and loading with the ¹⁹F-agent.

<p>(A) Cellular viability was investigated before and after labeling with the ¹⁹F-agent, Cell Sense. Although a statistically significant difference was observed in hMSC after labeling, the viability remained high (>80%) in all experiments. There was no significant difference in mMSC viability. (B) Cellular loading was determined by performing NMR on a known number of cells alongside a reference peak with a known number of ¹⁹F atoms. We observed variation in cellular loading of both hMSC and mMSC between experiments. However, this variation does not affect in vivo ¹⁹F quantification since each transplant was only compared to its specific cellular loading.</p