PROJECT SUMMARY
Lupus nephritis (LN) is a common manifestation of systemic lupus erythematosus that can lead to
irreversible renal impairment. Current immunosuppressive therapies fail to reverse disease in more than half of
treated patients and only 2 new drugs have been approved treatment, both of which confer only modest
improvement. Renal myeloid cells are involved in renal injury in LN, both in humans and animal models.
Macrophages are highly plastic and can mediate both pro-inflammatory and reparative functions. Because
there are so many subsets of myeloid cells and some of them change their function over time, analysis of
single cells is crucial to the study of these cells. Initial studies in Phase 1 and early Phase 2 of the
Accelerating Medicines Partnerships-SLE (AMP-SLE), of which we are all members, have shown that there are
multiple subsets of macrophages in LN kidneys that are analogous to myeloid subsets in mice but the function
of these subsets and whether they are pathogenic, or protective is still not known. Study of kidney tissues in
LN patients is hampered by the small size of the kidney biopsy and the infrequency of these biopsies in
individual patients over the course of their disease. Therefore, animal models, when carefully and rigorously
employed, are especially useful for addressing hypotheses generated by examining human data.
Our overall hypothesis is that we will identify human-relevant myeloid cell subsets in LN models that
reflect differences in disease pathophysiology, disease stage and responsiveness to treatments and that this
information will help identify new pathways for therapeutic intervention and direct personalized treatment. Our
approach is focused on identifying and testing the function of human-relevant cell subsets and pathways in
vitro and under physiologic conditions in vivo. In Aim 1 we will complete the integration of single cell RNASeq
analysis of myeloid cells from 5 different models of LN with that from AMP-SLE Phase 2 to map both shared
and unique macrophage sub-populations. We will follow the fate of peripheral myeloid cells as they transition
from the blood into the kidneys to define how the nephritis-specific profile of each subset and how they are
related to each other. We will then determine whether there is a particular myeloid cell profile that is associated
with response or non-response of LN patients to standard of care therapy. In Aim 2 we will determine how
renal myeloid cells interact with renal stromal cells both in vitro and in vivo. We will analyze the fate of renal
myeloid cells (in responder and non-responder mice) in human-relevant mouse models treated with remission
induction therapies to identify reparative subsets and pathways. Our focus here will be on both standard of
care therapy and on belimumab (anti-BAFF) since this is the only biologic drug so far approved for treatment of
LN and for prevention of further renal flares. In Aim 3 we will use CRISPR libraries for in vivo targeting of 13
transcription factors we have identified in preliminary studies to screen for new therapeutic approaches to
protect LN kidneys from disease progression, fibrosis, and end stage renal disease.