Synovial dendritic cell subsets in RA
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Events occurring close in time are often linked in memory, and recent studies suggest that such memories are encoded by overlapping neuronal ensembles. However, the role of dendritic plasticity mechanisms in linking memories is unknown. Here we show that memory linking is dependent not only on neuronal ensemble overlap in the mouse retrosplenial cortex, but also on branch-specific dendritic allocation mechanisms. The same dendritic segments are preferentially activated by two linked (but not independent) contextual memories, and spine clusters added after each of two linked (but not independent) contextual memories are allocated to the same dendritic segments. Importantly, we show that the reactivation of dendrites activated during the first context exploration is sufficient to link two contextual memories. Our results demonstrate a critical role for localized dendritic plasticity in memory integration and reveal rules governing how linked and independent memories are allocated to dendritic compartments.
Integrating single-cell RNA and T cell/B cell receptor sequencing with mass cytometry reveals dynamic trajectories of human peripheral immune cells from birth to old age
A comprehensive understanding of the evolution of the immune landscape in humans across the entire lifespan at single-cell transcriptional and protein levels, during development, maturation and senescence is currently lacking. We recruited a total of 220 healthy volunteers from the Shanghai Pudong Cohort (NCT05206643), spanning 13 age groups from 0 to over 90 years, and profiled their peripheral immune cells through single-cell RNA-sequencing coupled with single T cell and B cell receptor sequencing, high-throughput mass cytometry, bulk RNA-sequencing and flow cytometry validation experiments. We revealed that T cells were the most strongly affected by age and experienced the most intensive rewiring in cell–cell interactions during specific age. Different T cell subsets displayed different aging patterns in both transcriptomes and immune repertoires; examples included GNLY+CD8+ effector memory T cells, which exhibited the highest clonal expansion among all T cell subsets and displayed distinct functional signatures in children and the elderly; and CD8+ MAIT cells, which reached their peaks of relative abundance, clonal diversity and antibacterial capability in adolescents and then gradually tapered off. Interestingly, we identified and experimentally verified a previously unrecognized ‘cytotoxic’ B cell subset that was enriched in children. Finally, an immune age prediction model was developed based on lifecycle-wide single-cell data that can evaluate the immune status of healthy individuals and identify those with disturbed immune functions. Our work provides both valuable insights and resources for further understanding the aging of the immune system across the whole human lifespan.
CCN2 mediates fibroblast-macrophage interaction in knee arthrofibrosis based on single-cell RNA-seq analysis
Knee arthrofibrosis, characterized by excessive matrix protein production and deposition, substantially impairs basic daily functions, causing considerable distress and financial burden. However, the underlying pathomechanisms remain unclear. Here, we characterized the heterogeneous cell populations and cellular pathways by combination of flow cytometry and single-cell RNA-seq analysis of synovial tissues from six patients with or without knee arthrofibrosis. Increased macrophages and fibroblasts were observed with decreased numbers of fibroblast-like synoviocytes, endothelial cells, vascular smooth muscle cells, and T cells in the arthrofibrosis group compared with negative controls. Notably, fibroblasts were discovered to interact with macrophages, and lead to fibrosis through TGF-β pathway induced CCN2 expression in fibroblasts. CCN2 was demonstrated to be required for fibroblast pro-fibrotic functions (activation, proliferation, and migration) through TGFBR/SMAD pathway. The expression of CCN2 was positively correlated with the collagen volume and TGF-β expression and negatively associated with patient-reported outcome measures in another cohort of patients with knee arthrofibrosis. Our study reveals the role of CCN2 in the fibroblast-macrophage interaction through TGF-β pathway which might help to shed light on CCN2 as a potential biomarker.
Cross-talk of inflammation and cellular senescence: a new insight into the occurrence and progression of osteoarthritis
Osteoarthritis (OA) poses a significant challenge in orthopedics. Inflammatory pathways are regarded as central mechanisms in the onset and progression of OA. Growing evidence suggests that senescence acts as a mediator in inflammation-induced OA. Given the lack of effective treatments for OA, there is an urgent need for a clearer understanding of its pathogenesis. In this review, we systematically summarize the cross-talk between cellular senescence and inflammation in OA. We begin by focusing on the mechanisms and hallmarks of cellular senescence, summarizing evidence that supports the relationship between cellular senescence and inflammation. We then discuss the mechanisms of interaction between cellular senescence and inflammation, including senescence-associated secretory phenotypes (SASP) and the effects of pro- and anti-inflammatory interventions on cellular senescence. Additionally, we focus on various types of cellular senescence in OA, including senescence in cartilage, subchondral bone, synovium, infrapatellar fat pad, stem cells, and immune cells, elucidating their mechanisms and impacts on OA. Finally, we highlight the potential of therapies targeting senescent cells in OA as a strategy for promoting cartilage regeneration.
Targeting macrophage polarization by inhibiting Pim2 alleviates inflammatory arthritis via metabolic reprogramming
Macrophage polarization and energy metabolic reprogramming play pivotal roles in the onset and progression of inflammatory arthritis. Moreover, although previous studies have reported that the proviral integration of Moloney virus 2 (Pim2) kinase is involved in various cancers through the mediation of aerobic glycolysis in cancer cells, its role in inflammatory arthritis remains unclear. In this study, we demonstrated that multiple metabolic enzymes are activated upon Pim2 upregulation during M1 macrophage polarization. Specifically, Pim2 directly phosphorylates PGK1-S203, PDHA1-S300, and PFKFB2-S466, thereby promoting glycolytic reprogramming. Pim2 expression was elevated in macrophages from patients with inflammatory arthritis and collagen-induced arthritis (CIA) model mice. Conditional knockout of Pim2 in macrophages or administration of the Pim2 inhibitor HJ-PI01 attenuated arthritis development by inhibiting M1 macrophage polarization. Through molecular docking and dynamic simulation, bexarotene was identified as an inhibitor of Pim2 that inhibits glycolysis and downstream M1 macrophage polarization, thereby mitigating the progression of inflammatory arthritis. For targeted treatment, neutrophil membrane-coated bexarotene (Bex)-loaded PLGA-based nanoparticles (NM@NP-Bex) were developed to slow the progression of inflammatory arthritis by suppressing the polarization of M1 macrophages, and these nanoparticles (NPs) exhibited superior therapeutic effects with fewer side effects. Taken together, the results of our study demonstrated that targeting Pim2 inhibition could effectively alleviate inflammatory arthritis via glycolysis inhibition and reversal of the M1/M2 macrophage imbalance. NM@NPs loaded with bexarotene could represent a promising targeted strategy for the treatment of inflammatory arthritis.
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