Attenuation of Chronic Renal Allograft Rejection in Rats by Exosomes from Human induced Pluripotent Stem Cell derived Nephron Progenitor Cells

Introduction: Chronic rejection (CR) is a pressing unmet need in kidney transplantation, leading to irreversible graft dysfunction. To overcome the limitations of current therapies, this study focuses on a novel strategy using exosomes from human induced pluripotent stem cell derived nephron progenitor cells (hiPSC-NPCs-Exos), aiming to validate their efficacy in mitigating CR and providing direct evidence for the development of innovative therapeutic approaches.
Methods: Exosomes were isolated from human induced pluripotent stem cell-derived nephron progenitor cells (hiPSC-NPCs) and characterized in accordance with the Minimal Information for Studies of Extracellular Vesicles (MISEV) guidelines. A rat model of CR was established by performing an orthotopic kidney transplantation from F344 donor rats to Lewis recipient rats. Starting from post-operative day 0 until day 18, recipient rats (n=3 per group) received intravenous injections via the tail vein every three days (a total of 7 administrations) of either vehicle control (saline), or hiPSC-NPCs-Exos at low- (1×10^9 particles), medium- (1×10^10 particles), or high-dose (1×10^11 particles) in a 500 µL volume. Survival was monitored for 12 weeks with weekly assessment of urine output and 24-h urinary protein, renal function was assessed by measuring serum creatinine (Scr) and blood urea nitrogen (Bun). At 12 weeks post-transplantation, renal allografts were harvested for histological examination and scored according to the Banff 2021 classification criteria.
Results: Except for one rat in the model group that died in 8th week post-transplantation due to chronic fibrotic kidney injury, no statistically significant differences were found in renal function (24-hour urine volume, Scr, and Bun) among the groups (p>0.05). Compared to the model and low-dose (1×10^9 particles) groups, the middle-dose (1×10^10 particles) group significantly reduced urinary protein excretion, renal fibrosis score, and the expression levels of TGF-β1, FN, and α-SMA (all p<0.05). The high-dose (1×10^11particles) group exhibited efficacy comparable to the middle-dose group across all measured parameters, with no significant intergroup differences (p> 0.05).
Conclusion: Our findings demonstrate that hiPSC-NPCs-Exos ameliorate renal fibrosis and functional impairment in chronic rejection after kidney transplantation, highlighting their potential as a novel therapeutic strategy for this condition.