Study design
The experimental grouping of mice was shown in Table S1. Thirty-six R848-induced B6 mice were randomly divided into 4 groups (n= 9 in each group): normal saline treatment group, SBI treatment group, MSCs treatment group, and SBI plus MSCs treatment group. Umbilical cord derived MSCs were kindly provided by the Stem Cell Bank of Jiangsu Province (Beike Biotechnology) and cultured as previously described [11[] Yuan, Xinran et al. “Mesenchymal stem cell therapy induces FLT3L and CD1c+ dendritic cells in systemic lupus erythematosus patients.” Nature communications vol. 10,1 2498. 7 Jun. 2019, doi:10.1038/s41467-019-10491-8]. Both SBI and MSCs were suspended in normal saline. SBI was administered by gastric gavage at 200mg/kg daily from week 5, and MSCs (1×106 cells) were injected via the caudal vein at week 9. Meanwhile, acetone-induced B6 mice (n=6) were applied as normal controls and received normal saline treatment. All mice were sacrificed by cervical dislocation at week 12. Prior to this urine was collected by massaging the bladder for urinary protein and creatinine, and later serum was collected for antibody levels and kidneys were collected to assess histologic changes. In addition, mouse spleens were ground to cell suspensions, resuspended in red blood cell lysis buffer for 5 min, passed through a 70μm cell filter, and centrifuged to obtain splenocytes.