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340 Cell-Penetrating Peptides: Processes and Applications
Donor
Recipient
IV injection
Spleen isolation
Cell isolation and
magnetic sorting
CLIO-Tat
labeling
FIGURE 15.8 Cell recovery of CLIO–Tat-labeled cells. The FACS analysis of unseparated
recipient splenocytes is shown on the right (top). In vivo recovered and magnetically separated
cells are shown at the bottom right. The arrow points to the fluorescent CLIO–Tat cell
population recovered from the spleen during the first round of magnetic separation.
CLIO–Tat as described above and injected them into recipient mice (Figure 15.8).
Approximately 2 × 10 7 purified cells were injected into a recipient mouse through
the tail vein and no adverse effects were observed. The recipient mouse was sacrificed
after 24 h and the spleen excised. Splenic lymphocytes were isolated as described
above and the obtained cell suspension subjected to FACS analysis before and after
magnetic separation. Our data show that 44.9% of the lymphocytes adhering to the
magnetic separator were fluorescently labeled and thus contained CLIO–Tat. Higher
yields (>90% of cells) were observed after repeated runs through the magnetic
separator. These results clearly attest to the feasibility of recovering i.v. injected
CLIO–Tat-labeled cells.
15.3.1.6 High Resolution In Vivo MR Imaging of CLIO–Tat Labeled Cells
We then determined whether CLIO–Tat-labeled lymphocytes would be detectable
in tumor environments. In earlier research we had quantitated the tumoral recruitment
of different lymphocyte populations using isotope labeling techniques. 48 Briefly, a
total of 3 × 10 7 labeled cells were administered i.v. into a nude mouse bearing a 9L
glioblastoma implanted intracerebrally. At 0.3% of cells accumulating per g tumor
(tumor weight 80 mg), one can expect approximately 7.5 × 10 3 cells within the tumor
or 1.5 × 10 3 cells per image slice (Figure 15.9). MR imaging at high spatial resolution
Counts
0 40 80 120 160 200
Counts
0 40 80 120 160 200
10 0
10 0
Donor cells before
labelling
10 2
10 1
FL1-Height
10 2
10 1
FL1-Height
10 3
Recovered cells
10 3
10 4
10 4