Allogeneic Umbilical Cord Mesenchymal Stromal Cells for the Treatment of Chronic Antibody-Mediated Rejection in Kidney Transplantation

Patients in this arm will receive 4 injections of allogeneic mesenchymal stromal cells (CSM) derived from human umbilical cord. The doses will be 1.106 cells/kg administered intravenously at days 0, 7, 14, and 21. The injections are given after thawing, washing, resuspension, and adjusting the dose. The CSM treatment aims to control chronic active antibody-mediated rejection (cABMR), improve renal function, reduce proteinuria, and increase graft survival without changing the immunosuppressive regimen.

Patients in this arm will receive placebo treatments, which will consist of 150 mL of saline (NaCl 0.9%) administered intravenously at the same intervals as the CSM group (days 0, 7, 14, and 21). The placebo will be administered under the same conditions as the treatment, and the participants and investigators will remain blinded to the group allocation. Like the CSM group, no changes will be made to the patients' immunosuppressive regimen.