Page 66 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis
P. 66

                                Chapter 3
 Figure 7 R2' relaxation rate plotted against iron concentration. The linear fit on all data points excluding the day 0 data points is displayed. Data points belonging to one cell division series are connected. Data points are labeled, referring to data series (high, H; low, L) and the day of harvesting after labeling (days 0, 1, 2 and 3). After one day (approximately one cell cycle), all data points converged to the same relaxation curve (linear fit). Deviation from this relaxation curve on day 0 was apparent and proved to be systematic.
The different labeling protocols (High and Low) resulted in different estimated values of average iron content per cell (based on optical emission spectrometry). The High labeling protocol resulted in 1.4 pg per cell iron content; the Low yielded 1.0 pg per cell. The cell dilution series of these batches resulted in different r2' relaxivities (Fig. 6a). The relaxivity was more than double (r2' = 642 mM-1 s-1) in the case of the Low labeling protocol compared with the one of the High protocol (r2' = 314 mM-1 s-1). Figure 6b exhibits R2' relaxation rates as a function of labeled cell density. Despite the large difference in the average iron content per cell (High and Low labeling protocols), relaxation values at the same cell densities were very close, the cellular relaxivities being r2' = 10.9 x 10-3 ul s-1 for the Low series and r2' = 10.3 x 10-3 ul s-1 for the high series.
A comparison between labeled cell division series, where the labeling protocol was different, is depicted in Fig. 7. The series exhibit very close R2' relaxation rates in a wide range of iron concentrations after one division cycle. In the case of the cell division series, R2' showed no sensitivity to the differences in initial cell labeling. Both division series converged to the same linear curve established by linear fit to the data points. The deviation from the relaxation vs iron concentration curve at day 0 appeared in both batches.
64






























































































   64   65   66   67   68