Background: Mesenchymal stromal/stem cells (MSCs) are known for their immunomodulatory properties. This study was performed to analyse the effects of MSC transplantation on treatment-resistant lupus nephritis (LN). Methods: In this phase I trial, nine biopsy-proven LN patients refractory to standard treatments underwent systemic infusion of 2 £ 106 allogeneic adipose-derived (AD) MSCs/kg and were followed for 12 months post-intervention. Results: The treatment protocol resulted in no major adverse events. Urine protein levels significantly decreased during the first month post-intervention (baseline vs. month 1 (median): 1800 vs. 1020, P = 0.008), followed by a gradual increase but remained significantly lower than baseline only up to the 3rd month. During the first 3 months post-intervention, complete renal response (proteinuria < 0.5 g/24 h) and partial response (proteinuria > 0.5 g/24 h, but > 50% decrease in proteinuria) were observed in 33.3% and 44.4% of the patients, respectively, though these rates declined thereafter. Median score of Systemic Lupus Erythematosus Disease Activity Index decreased significantly from 16 at the baseline to 6 at sixth months post-treatment (P = 0.007), though it slightly increased at the 12th month follow-up. Conclusions: Allogenic AD-MSC transplantation was associated with favourable safety and efficient to reduce urine protein excretion and disease activity; however, the maximum effect (greatest improvement in outcomes) was observed at 1 month based on the proteinuria, and 6 months post-intervention based on disease activity scores. A single dose of AD-MSCs may not be adequate to maintain long-term remission of refractory LN, and so, additional doses may be required.

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