Scintigraphic tracking of mesenchymal stem cells after portal, systemic intravenous and splenic administration in healthy beagle dogs.

Mesenchymal stem cells have been proposed to treat liver disease in the dog. The objective of this study was to compare portal, systemic intravenous and splenic injections for administration of mesenchymal stem cells to target the liver in healthy beagle dogs. Four healthy beagle dogs were included in the study. Each dog received mesenchymal stem cells via all three delivery methods in randomized order, 1 week apart. Ten million fat-derived allogeneic mesenchymal stem cells labeled with Technetium-99m (99mTc)-hexamethyl-propylene amine oxime(HMPAO) were used for each injection. Right lateral, left lateral, ventral, and dorsal scintigraphic images were obtained with a gamma camera equipped with a low-energy all-purpose collimator immediately after injection and 1, 6, and 24 h later. Mesenchymal stem cells distribution was assessed subjectively using all four views. Pulmonary, hepatic, and splenic uptake was quantified from the right lateral view, at each time point. Portal injection resulted in diffuse homogeneous high uptake through the liver, whereas the systemic intravenous injection led to mesenchymal stem cell trapping in the lungs. After splenic injection, mild splenic retention and high homogeneous diffuse hepatic uptake were observed. Systemic injection of mesenchymal stem cells may not be a desirable technique for liver therapy due to pulmonary trapping. Splenic injection represents a good alternative to portal injection. Scintigraphic tracking with 99mTc-HMPAO is a valuable technique for assessing mesenchymal stem cells distribution and quantification shortly after administration. Data obtained at 24 h should be interpreted cautiously due to suboptimal labeling persistence.