Biodistribution of mesenchymal stromal cells labeled with [89Zr]Zr-oxine in local radiation injuries in laboratory animals
Tracking the migration pathways of living cells after their introduction into the patient's body is a topical issue in the field of cell therapy. The question of studying the possibility of intravital long-term biodistribution of mesenchymal stromal cells in the body remains open today. The study used 49 laboratory animals. Modeling of local radiation injuries was carried out and the distribution dynamics of mesenchymal stromal cells labeled with [89Zr]Zr-oxin in the body of rats was studied. The use of intravenous administration of mesenchymal stromal cells of human mucosal tissue labeled with [89Zr]Zr-oxin makes it possible to visualize the focus of local radiation injury using positron emission tomography, and for effective cell therapy, local injection of mesenchymal stromal cells into the area of the visualized focus of local radiation injury is recommended. Biodistribution of human mesenchymal stromal cells labeled with [89Zr]Zr-oxin is completely safe, since intravenous administration leads to an initial accumulation of cells in the lungs with subsequent redistribution to the liver, spleen and kidneys; with intracardiac administration, the distribution of cells is similar to intravenous administration; when locally injected into tissues, cells of mesenchymal stromal cells are not distributed systemically in significant quantities.
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Modeling of relatively “soft” X-ray radiation of local radiation injuries (LII) was carried out on the X-ray unit LNK-268 (RAP100-10) (Diagnostics-M, Russia) with an irradiation mode at a dose of 110 Gy with an aluminum filter of 0.1 mm, voltage 30 kV, beam current 6.1 mA, dose rate 21.1 Gy/min for 312 s (dose accuracy ±5%, dose measurement uncertainty ±6%) according to the previously proposed method (Dominici, M. et al. 2006), leading to a short latent period and chronic skin ulcers in laboratory animals. After irradiation, the animals were seated in individual sterile boxes with an autonomous Smart Flow ventilation system (Tecniplast Group, Italy), providing free access to water and food. The experiment used non-personalized human mesenchymal stromal cells (MSCs) were cultivated in xenogenic components-xeno-free medium (Stem Cell, Canada) supplemented with 100 U/ml penicillin and 100 U/ml streptomycin; 2 mm glutamine from the 3rd to the 5th passage. The resulting MSCs were administered to laboratory animals at a calculated dose of 2 million cells per 1 kg. The immunophenotype of MSCs in human mucosal tissue was determined using flow cytometry. The expression of surface markers was assessed using fluorochrome-labeled antibodies against CD34, CD45, CD90, CD105, CD73, HLA-DR (BD Biosciences and Becman Coulter, USA) on a FACSCanto II flow cytometer (Becton Dickinson CA, USA) according to the manufacturer's instructions. Cell viability was assessed using the 7-ADD dye, which penetrates the cytoplasmic cell membrane and binds to its DNA. The number of CD45-negative 7-ADD-positive cells was determined on a FACS Canto II flow cytometer (Becton Dickinson CA, USA) according to the manufacturer's instructions. To label stem cells, a radiopharmaceutical precursor [89Zr]Zr-oxin was synthesized, which is a complex compound of 8-hydroxyquinoline with the zirconium-89 radionuclide. Zirconium-89 in the form of zirconium oxalate was obtained from CJSC «Cyclotron» (Obninsk, Russia). The radiopharmaceutical precursor ([89Zr]Zr-oxine) used in this work was obtained from solutions of 8-hydroxyquinoline and zirconium-89 oxalate by a direct labeling reaction, as a result of which a complex of zirconium-89 with 8-hydroxyquinoline was obtained with a volume activity of at least 1 MBq/ ml. Cells were labeled in vitro with [89Zr]Zr-oxin with a radiochemical purity of at least 87.0±3.0%. 100 µl of [89Zr]Zr-oxine with the specified volumetric activity and pH value of the solution was added to the prepared cell suspension in 1 ml of physiological solution. Cells were incubated for 30 minutes at 37°C. At the end of the incubation procedure, labeled cells were pelleted by centrifugation (150g, 5 min). The supernatant containing unbound [89Zr]Zr-oxine was quantitatively removed and transferred to a specially marked tube for radiometry. The remaining cells were carefully resuspended in 1 ml of salane.