Protective Renalase Deficiency in β-Cells Shapes Immune Metabolism and Function in Autoimmune Diabetes

Abstract

Type 1 diabetes (T1D) is caused by the immune-mediated loss of pancreatic beta cells that produce insulin. The latest advances in stem cell (SC)-beta cell differentiation methods have made a cell replacement therapy for T1D feasible. However, recurring autoimmunity would rapidly destroy transplanted SC-beta cells. A promising strategy to overcome immune rejection is to genetically engineer SC-beta cells. We previously identified Renalase (Rnls) as a novel target for beta cell protection. Here we show that Rnls deletion endows beta cells with the capacity to modulate the metabolism and function of immune cells within the local graft microenvironment. We used flow cytometry and single-cell RNA sequencing to characterize beta cell graft-infiltrating immune cells in a mouse model for T1D. Loss of Rnls within transplanted beta cells affected both the composition and the transcriptional profile of infiltrating immune cells in favor of an anti-inflammatory profile with decreased antigen presenting capacity. We propose that changes in beta cell metabolism mediate local immune regulation and that this feature could be exploited for therapeutic goals.

Beta Cells Deficient forRenalaseCounteract Autoimmunity by Shaping Natural Killer Cell Activity

“…NK cells also upregulate gene expression of immune-regulatory Tgfβ1 when infiltrated in Rnls mut beta cell grafts (Supplemental Data Figure 1A and B). Interestingly, the frequency of NK cells in Rnls mut beta cell grafts was not only reduced in late stages 10 , but also at earlier time points preceding the detection of graft weight difference between control and Rnls mut (Supplemental Data Figure 1D and E; see Supplemental Data Figure 2 for gating strategy). Of note, the ILC1 frequency was not changed between the grafts and only represent a vast minority of infiltrating immune cells (≤ 1%) compared to NK cells (up to 14%) indicating that ILC1 likely does not play a major role in mediating the protective immune-regulation caused by Rnls mut beta cells 10 .…”

“…In addition to elevated numbers of CD4 + T cells and tolerogenic PD-L1 + APC, beta cell grafts deficient for Rnls showed markedly reduced frequency of NK cells. Because we previously demonstrated that PD-L1 blockade abrogates the advantage of Rnls mut beta cells to survive autoimmunity, and NK cells are known to modulate APC maturation and activation, we now investigated the role of NK cells in protection of Rnls mut beta cells in more detail 10 . The gene expression profile of both, graft-infiltrating NK cells and closely related type 1 innate lymphoid cells (ILC1), demonstrated markedly increased expression of genes involved in pathways of cellular activation and inflammation (interferon responses, allograft rejection, etc.)…”

“…The isogenic WT and Rnls mut beta cells were transplanted subcutaneously (s.c.) on opposite flanks of the same recipient mice following intravenous (i.v.) injection of diabetogenic splenocytes similar as described before (Supplemental Data Figure 1D and E) 9,10 . Strikingly, NKp46-depleted autoreactive splenocytes lost the ability to protect Rnls mut cells from autoimmunity in both immunodeficient recipients, NOD-Prkdc scid (NOD.scid) mice and NOD.scid gamma (NSG) mice completely deficient for functional T, B and NK cells (Figure 1C).…”

“…Beta cells lacking Rnls not only exhibit enhanced resilience to stress but also undergo comprehensive metabolic alterations favoring glycolysis 9,10 . Moreover, we have shown previously that Rnls-deficient beta cells orchestrate localized shifts in the overall immune cell composition within the graft, primarily characterized by enhanced infiltration of CD4 + T cells, reduced numbers of natural killer (NK) cells, and by the accumulation of tolerogenic antigen-presenting cells (APC) defined by diminished MHC class II expression coupled with elevated levels of Programmed Cell Death 1 Ligand 1 (PD-L1).…”

“…Beta cells deficient for Rnls promote a significant transcriptional change in CD45 + immune cells within the graft towards hallmark anti-inflammatory genes such as Transforming Growth Factor beta 1 (Tgfβ1). 10 However, the immune cell population responsible for initiating the immunoregulatory cross-talk to reduce autoimmunity against Rnls-deficient beta cell grafts remained elusive.…”