Remodeling Articular Immune Homeostasis with an Efferocytosis-inspired Nanoimitator Mitigates Rheumatoid Arthritis

Massive intra-articular infiltration of the pro-inflammatory macrophages is a prominent feature of rheumatoid arthritis (RA) lesions, which are thought to underlie articular immune dysfunction, severe synovitis and ultimate joint erosion. Here we report an efferocytosis-inspired nanoimitator (EINI) for in situ targeted reprogramming of the synovial inflammatory macrophages (SIMs) and thus thwarting their autoimmune attack and reinstating articular immune homeostasis, which mitigates RA. The EINI consisted of a drug-based core with an oxidative stress-responsive phosphatidylserine (PtdSer) corona and a shell of P-selectin-blocking motif, low molecular weight heparin (LMWH). When systemically administrated, the LMWH on the EINI first bound to P-selectin overexpressed on endothelium in subsynovial capillaries, which functioned as an antagonist disrupting neutrophils synovial trafficking. Due to the high dysregulation of the synovial microvasculature, the EINI subsequently enriched in joint synovium where the shell was exfoliated upon the reactive oxygen species stimulation, and PtdSer corona was then exposed. In an efferocytosis-like manner, the PtdSer-coroneted core was in turn phagocytosed by SIMs, which synergistically terminated the SIMs-initiated pathological cascades and serially reconstructed the intra-articular immune homeostasis, conferring a chondroprotection effect. These findings demonstrate that SIMs can be precisely remodeled via the efferocytosis-mimetic strategy, which holds great potential for RA treatment.