Organ transplantation relies upon nonspecific immunosuppressive (IS) agents to prevent graft rejection. However, IS drugs have significant toxicities and chronic rejection occurs despite their usage. We recently demonstrated that high levels of donor chimerism and total IS withdrawal can be established in highly-mismatched kidney transplant recipients (KTR). This was achieved through the use of a bioengineered stem cell product containing donor HSC and a unique population of CD8⁺/TCR^–cells, termed Facilitating Cells (FCRx), accompanied by reduced intensity conditioning. Herein,we evaluated differential molecular signatures within the allograft in tolerant kidney recipients. Methods: formalin-fixed paraffin-embedded allograft kidney biopsy samples (n = 24) from KT recipients diagnosed with (R; n = 5) and without acute rejection under standard immunosuppression (SIS; n = 5), FCRx induced tolerant protocol biopsies (SC; n = 7), and paired pre-implantation donor allograft biopsy samples from FCRx (D; n = 7) were used. Total RNA was isolated from samples and used for Affymetrix^TM GeneChip^® HG-U133 2.0 microarray hybridization. Pair-wise ANOVAs were performed among study groups (including SC vs. R, SC vs. SIS, and SC vs. D) to identify differentially expressed genes (DEGs) (P ≤ 0.001, FDR < 5%, fold change ≥ 1.5). Results: from the comparison of the two sample sets (FCRx vs. R) a total of 540 differentially expressed probesets were observed. The top canonical pathways down-regulated in FCRx were associated with immune response. From the comparison of the two sample sets (FCRx vs. SIS), 916 DEGs, represented by 1020 probe sets (268 up-regulated and 752 down-regulated), were identified in FCRx. The top network functions associated with these genes included cellular assembly and organization, cellular function, cell morphology, and cell signaling. The specific analysis of genes associated with immunological response showed only 7 significant signaling and B-cell receptor signaling pathway was identified as top significant canonical pathway.

Conclusions: These observations suggest that induction of tolerance in FCRx-treated KTR is associated with intragraft modulation of molecular mechanisms involved in activation and survival of B cells.

CITATION INFORMATION: Gallon L, Leventhal J, Dumur C, Mathew J, Nadimpalli L, Shetty A, Ildstad S, Mas V. Intragraft Molecular Pathways Associated with Tolerance Induction in Renal Transplantation. Am J Transplant. 2016;16 (suppl 3).

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