Anders Munk

The immunomodulatory and regenerative properties of mesenchymal stromal cells (MSCs) make MSC therapy a promising therapeutic strategy in kidney disease. A targeted MSC administration via the renal artery offers an efficient delivery method with limited spillover to other organs. Although local administration alleviates safety issues with MSCs in systemic circulation, it introduces new safety concerns in the kidneys. In a porcine model, we employed intra-renal arterial infusion of ten million allogenic adipose tissue-derived MSCs. In order to trigger any potential adverse events, a higher dose (hundred million MSCs) was also included. The kidney function was studied by magnetic resonance imaging after the MSC infusion and again at two weeks post-treatment. The kidneys were assessed by single kidney glomerular filtration rate (skGFR) measurements, histology and inflammation, and fibrosis-related gene expression. None of the measured parameters were affected immediately after the administration of ten million MSCs, but the administration of one hundred million MSCs induced severe adverse events. Renal perfusion was reduced immediately after MSC administration which coincided with the presence of microthrombi in the glomeruli and signs of an instant blood-mediated inflammatory reaction. At two weeks post-treatment, the kidneys that were treated with one hundred million MSCs showed reduced skGFR, signs of tissue inflammation, and glomerular and tubular damage. In conclusions, the intra-renal administration of ten million MSCs is well-tolerated by the porcine kidney. However, higher concentrations (one hundred million MSCs) caused severe kidney damage, implying that very high doses of intra-renally administered MSCs should be undertaken with caution.

The regenerative capacities of mesenchymal stromal cells (MSC) make them suitable for renal regenerative therapy. The most common delivery route of MSC is via intravenous infusion, which is associated with off-target distribution. Renal intra-arterial delivery offers a targeted therapy but limited knowledge is available regarding the fate of MSC delivered via this route. Therefore, we studied the efficiency and tissue distribution of MSC after renal intra-arterial delivery to a porcine renal ischemia reperfusion model. MSC were isolated from adipose tissue of healthy male pigs, fluorescently labelled and infused into the renal artery of female pigs. Flow cytometry allowed MSC detection and quantification in tissue and blood. In addition, qPCR was used to trace MSC by their Y-chromosome. During infusion, a minor number of MSC left the kidney via the renal vein and no MSC were identified in arterial blood. Ischemic and healthy renal tissue were analyzed 30 minutes and 8 hours after infusion and 1-4 x 104 MSC per gram of tissue were detected, predominantly, in the renal cortex, with a viability greater than 70%. Confocal microscopy demonstrated mainly glomerular localization of MSC, but they were also observed in the capillary network around tubuli. The infusion of heat inactivated (HI)-MSC, which are metabolically inactive, through the renal artery showed that HI-MSC were distributed in the kidney in a similar manner as regular MSC, suggesting a passive retention mechanism. Long term MSC survival was analyzed by Y-chromosome tracing and demonstrated that a low percentage of the infused MSC were present in the kidney 14 days after administration, while HI-MSC were completely undetectable. In conclusion, renal intra-arterial MSC infusion limited off-target engraftment, leading to efficient MSC delivery to the kidney, most of them being cleared within 14 days. MSC retention was independent of the metabolic state of MSC, indicating a passive mechanism.