Third-party mesenchymal stem cell infusion in kidney transplant recipient: 6-month safety interim analysis

Background: Mesenchymal stromal cell (MSC) have immunomodulating properties and could be used as immunosuppressive agents. We report the 6- month safety results for the 5 first patients treated with MSC after kidney transplantation (KTx). Here, we address 3 specific safety issues: immunization against MSC and engraftment syndrome defined as acute graft dysfunction not related to rejection and over-immunosuppression.
Patients and method: MSC production was carried out locally. MSC were not matched with kidney recipients’ HLA. Included patients were non-immunized, first transplant recipients from deceased donors. MSC (1.5–3.0 9 106/kg) infusion was planned 3 to 5 days post KTx. Patients with cardiovascular instability post KTx were excluded. All patients were treated with Basiliximab induction, Tacrolimus, Mycophenolate Mofetil and Steroid. We prospectively screened for anti-HLA antibodies at month 1, 3 and 6. Informed consent was obtained from all participants. The local ethical committee approved the protocol.
Results: Collectively there were 23/50 and 29/50 HLA mismatches (MM) with kidney and MSC donor respectively, out of which 5 were shared MM. One patient developed de novo DSA, 2 patients anti-HLA antibodies against shared kidney/MSC MM and 1 patient developed 2 specific antibodies against MSC (MSCSA) at month 6. All antibodies were anti HLA class I except for 1. We did not observe any “engraftment” syndrome. Three patients experienced non- severe opportunistic infections: 1 CMV reactivation and 2 polyoma-BK virus viremia.Conclusion: We did not observe any strong safety signal. We did however observe some degree of immunization in 3 patients: 2 developed antibodies against shared kidney/MSC donor HLA MM and 1 MSCSA.