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Hofbauer cells (HBCs) are fetal macrophages located in the placenta that contribute to antimicrobial defense, angiogenesis, tissue remodeling, and metabolic processes within the chorionic villi. Although their roles in placental biology are increasingly recognized, the mechanisms that regulate HBC identity and function are not yet fully defined. This study aimed to define the core transcriptomic and epigenomic features of HBCs in term placentas and to examine their capacity for transcriptional responsiveness and phenotypic variation. Using chromatin accessibility profiling and bulk RNA-seq, we found that HBCs exhibit a unique gene expression and chromatin accessibility profile compared with other fetal and adult macrophages. We identified a coordinated transcriptional network involving nuclear receptors (NRs) NR4A1-3, the glucocorticoid receptor, and RFX family members (RFX1, RFX2, RFX5) that appears to shape HBC identity, particularly through pathways linked to lipid metabolism and angiogenesis. Although exploratory in nature, in vitro stimulation studies showed that HBCs exhibited increased transcriptional activity in response to combined IL-4 and rosiglitazone treatment, including induction of the lipid transporter CD36. Mass cytometry analysis revealed surface markers indicative of both immature and mature macrophage states. These results together indicate that HBCs are a distinct and diverse population of macrophages with a specialized, adaptable regulatory program in the human placenta.

Mucosal secretory IgA (sIgA) plays a central role in protecting against the invasion of respiratory pathogen via the upper respiratory tract. To understand how intranasal booster induces mucosal sIgA response in humans, we first used liquid chromatography-tandem mass spectrometry for peptide identification of immunoglobulin (MS Ig-seq) and single-cell B cell receptor sequencing (scBCR-seq) to identify 42 mucosal spike-specific sIgA monoclonal antibodies (mAbs) after intranasal booster. These mucosal sIgA mAbs exhibited enhanced neutralization up to 100-fold against SARS-CoV-2 variants compared with their monomeric IgG and IgA isotypes. Deep sequencing and longitudinal analysis of B cell receptor repertoires revealed that intranasal booster restimulates memory B cells primed by intramuscular vaccination to undergo IgA class switching, somatic hypermutation, and clonal expansion. Single-cell RNA-seq (scRNA-seq) revealed that intranasal booster upregulated the expression of mucosal homing receptors in spike-specific IgA-expressing B cells. This increase coincided with a transient increase of cytokines and chemokines that facilitate B cell recruitment in the nasal mucosa. Our findings demonstrate that intranasal booster can be an effective strategy for inducing upper respiratory mucosal sIgA and establishing mucosal immune protection.

Clonal hematopoiesis of indeterminate potential (CHIP) is the expansion of blood stem cells and progeny after somatic mutation. CHIP associates with increased cardiovascular disease (CVD), with inflammation from macrophages a proposed common effector. However, mouse CHIP studies are discordant for clonal expansion and inflammation. Similarly, directionality of association between CHIP and CVD remains debated. We investigated effects of 3 CHIP mutations on macrophage cytokines, clonal expansion, and atherosclerosis in parallel. We found that cytokine release and inflammasome activation are increased by Tet2 mutation but decreased by Dnmt3a. However, Jak2 mutant macrophages produced equivalent cytokine as WT. In mice, Tet2 mutants clonally expanded, but Dnmt3a and Jak2 mutants did not. Expansion was unaffected by systemic inflammation, while hyperlipidemia expanded Tet2-/- cells but not mono-allelic mutants. Similarly, human Mendelian randomization showed no effect of serum cytokines or CVD on CHIP risk. Experimental atherosclerosis was increased in females with Tet2 and males with Jak2, but it was unchanged with Dnmt3a mutations. Together, common CHIP mutations have disparate effects on macrophage cytokines and clonal expansion, and they have sex-dependent effects on atherogenesis, suggesting a common mechanism across CHIP is unlikely. Thus, CHIP mutations differ in pathophysiology and clinical sequelae across sexes and should be treated as different entities.

C-type natriuretic peptide (CNP) is known to promote chondrocyte proliferation and bone formation; however, CNP's extremely short half-life necessitates continuous intravascular administration to achieve bone-lengthening effects. Vosoritide, a CNP analog designed for resistance to neutral endopeptidase, allows for once-daily administration. Nonetheless, it distributes systemically rather than localizing to target tissues, which may result in adverse effects such as hypotension. To enhance local drug delivery and therapeutic efficacy, we developed a potentially novel synthetic protein by fusing a collagen-binding domain (CBD) to CNP, termed CBD-CNP. This fusion protein exhibited stability under heat conditions and retained the collagen-binding ability and bioactivity as CNP. CBD-CNP localized to articular cartilage in fetal murine tibiae and promoted bone elongation. Spatial transcriptomic analysis revealed that the upregulation of chondromodulin expression may contribute to its therapeutic effects. Treatment of CBD-CNP mixed with collagen powder to a fracture site of a mouse model increased bone mineral content and bone volume compared with CNP-22. Intraarticular injection of CBD-CNP to a mouse model of knee osteoarthritis suppressed subchondral bone thickening. By addressing the limitations of CNP's rapid degeneration, CBD-CNP leverages its collagen-binding capacity to achieve targeted, sustained delivery in collagen-rich tissues, offering a promising strategy for enhancing chondrogenesis and osteogenesis.

The transcription factor IKAROS, encoded by IKZF1, is crucial for lymphocyte development and differentiation. Germline heterozygous IKZF1 mutations cause B cell immunodeficiency, but also affect T cells. Patients with IKZF1 haploinsufficiency (HI) or dimerization-defective (DD) variants show reduced naive and increased memory T cells, while dominant-negative (DN) mutations result in the opposite phenotype. Gain-of-function patients display variable patterns. To investigate IKAROS's role in shaping the human naive/memory T cell phenotype, we performed IKAROS immunomodulation and knockdown experiments and analyzed early T cell development in an artificial thymic organoid (ATO) system using CD34+ cells from patients with representative IKZF1 variants. IKAROS inhibition by lenalidomide or silencing by small hairpin RNA directly altered expression of HNRNPLL, the master regulator of CD45 isoform splicing that defines CD45RA+/naive and CD45RO+/memory phenotypes. In the ATO system, IKAROS-DN precursor cells were blocked at the CD4-CD8-/double-negative stage and retained a CD45RA+ phenotype, whereas IKAROS-HI cells inefficiently reached the CD4+CD8+/double-positive stage and partially transitioned from CD45RA to CD45RO. Analysis of public gene expression data showed high HNRNPLL expression in double-positive thymic cells, beyond the stages affected by IKZF1 DN and HI mutations. Collectively, these findings indicate that IKAROS regulates early and late T cell development by mechanisms, including HNRNPLL modulation.

Cardiac arrhythmias increase during acute SARS-CoV-2 infection and in long COVID syndrome, by unknown mechanisms. This study explored the acute and long-term effects of COVID-19 on cardiac electrophysiology and the cardiac conduction system (CCS) in a hamster model. Electrocardiograms and subpleural pressures were recorded by telemetry for 4 weeks after SARS-CoV-2 infection, and interferon-stimulated gene expression and macrophage infiltration of the CCS were assessed at 4 days and 4 weeks postinfection. COVID-19 induced pronounced tachypnea and cardiac arrhythmias, including bradycardia and persistent atrioventricular block, though no viral protein expression was detected in the heart. Arrhythmias developed rapidly, partially reversed, and then redeveloped, indicating persistent CCS injury. COVID-19 induced cardiac cytokine expression, connexin mislocalization, and CCS macrophage remodeling. Interestingly, sterile innate immune activation by direct cardiac injection of polyinosinic:polycytidylic acid (PIC) induced arrhythmias similar to those of COVID-19. PIC strongly induced cytokine secretion and interferon signaling in hearts, human induced pluripotent stem cell-derived cardiomyocytes, and engineered heart tissues, accompanied by alterations in excitation-contraction coupling. Importantly, the pulmonary and cardiac effects of COVID-19 were blunted by JAK/STAT inhibition or a mitochondrially targeted antioxidant, indicating that SARS-CoV-2 infection indirectly leads to arrhythmias by innate immune activation and redox stress, which could have implications for long COVID syndrome.

The tumor microenvironment plays a key role in cancer progression and therapy resistance, with cancer-associated fibroblasts (CAFs) contributing to desmoplasia, extracellular matrix (ECM) remodeling, and elevated interstitial fluid pressure, all of which hinder drug delivery. We investigated fibroblast activation protein-targeted (FAP-targeted) near-infrared photoimmunotherapy (NIR-PIT) as a strategy to improve drug penetration in CAF-rich tumors. In clinical esophageal cancer samples, FAP expression strongly correlated with increased collagen I, hyaluronic acid, and microvascular collapse. CAF-rich 3D spheroids demonstrated elevated ECM deposition and significantly impaired drug uptake compared with CAF-poor models. FAP-targeted NIR-PIT selectively reduced CAFs, reduced ECM components, and restored drug permeability. In vivo, FAP-targeted NIR-PIT enhanced the accumulation of panitumumab and Abraxane in CAF-rich tumors and improved antitumor efficacy when combined with chemotherapy. These findings highlight FAP-targeted NIR-PIT as a promising therapeutic approach to remodel the tumor stroma and overcome drug resistance in desmoplastic solid tumors.

We recently showed that cell surface translocation of the endoplasmic reticulum-resident protein GRP78, when bound by activated α 2-macroglobulin (α2M*), induces pro-fibrotic responses in glomerular mesangial cells in response to high glucose and regulates activation of the pro-fibrotic cytokine transforming growth factor-β1 (TGF-β1), implicating a pathogenic role in glomerulosclerosis. Interstitial fibrosis, largely mediated by proximal tubular epithelial cells (PTEC) and renal fibroblasts, develops later in kidney disease and correlates with functional decline. Here we investigated whether interstitial fibrosis was mediated by cell surface GRP78 (csGRP78)/α2M*. High glucose and TGF-β1 increased csGRP78 and α2M* in PTEC and renal fibroblasts, and their inhibition prevented fibrotic protein production. Interestingly, for TGF-β1, this depended on inhibition of noncanonical signaling through YAP/TAZ, with Smad3 activation unaffected. In vivo, type 1 diabetic Akita mice overexpressing TGF-β1 were treated with either a neutralizing antibody for csGRP78 (C38) or α2M* (Fα2M) or an inhibitory peptide blocking csGRP78/α2M* interaction, and mice with unilateral ureteral obstruction were treated with Fα2M or inhibitory peptide. Consistently, inhibition by antibody or peptide attenuated fibrosis and pro-fibrotic signaling. These findings show an important role for csGRP78/α2M* in mediating tubulointerstitial fibrosis in both diabetic and nondiabetic kidney disease and support their inhibition as a potential antifibrotic therapeutic intervention.

BACKGROUNDIcotrokinra is the first and only targeted oral peptide that selectively binds the IL-23 receptor with high affinity to precisely inhibit IL-23 signaling. Icotrokinra demonstrated high rates of complete skin clearance and durable disease control in the phase IIb trial, FRONTIER-1, and its long-term extension, FRONTIER-2, in participants with moderate-to-severe plaque psoriasis. This study evaluated systemic and skin pharmacodynamic response of icotrokinra and its relationship to clinical response in FRONTIER participants.METHODSFRONTIER-1 participants received icotrokinra or placebo for 16 weeks. FRONTIER-2 followed participants for up to 1 year of treatment; placebo participants transitioned to icotrokinra after week 16. Systemic pharmacodynamic changes were assessed in serum through week 52. Skin pharmacodynamic changes were assessed using transcriptomic analysis of skin biopsies and protein quantification in tape-strip samples through week 16.RESULTSIcotrokinra dose-dependently reduced serum levels of the IL-23/IL-17 axis and psoriasis disease biomarkers through week 52, with maximal reductions observed with the highest 100 mg twice-daily dose. Proteomic analyses showed icotrokinra selectively blocked IL-23-driven inflammation without broader impacts on circulating proteins, including serum IL-23 levels. Sixteen weeks of icotrokinra, but not placebo, reduced expression of psoriasis-associated genes in lesional skin. Icotrokinra treatment also reduced psoriasis-relevant proteins in week 16 lesional skin tape-strips to levels comparable to nonlesional samples.CONCLUSIONIcotrokinra induced a dose-dependent pharmacodynamic response, with early (week 4) and sustained (week 52) reductions in biomarkers of IL-23 pathway activation and psoriasis disease severity, which correlated with clinical response.TRIAL REGISTRATIONClinicalTrials.gov: NCT05223868, NCT05364554.FUNDINGJohnson & Johnson.

CD4+ T cells predominate lymphocytic foci found in the salivary glands (SGs) of Sjögren's disease (SjD) cases. Yet little is known about T cell receptor (TCR) repertoire features that distinguish cases from healthy controls (HCs), the relationship between SG and peripheral blood (PB) repertoires of cases, and antigens recognized by pathogenic T cell clones. We performed deep sequencing of bulk-sorted CD4+CD45RA- PB T cells from SjD cases and matched HCs, and single-cell TCR sequencing of the same T cell population from labial SG biopsies of these cases. We found that clonally expanded SG CD4+ T cells expressed complementarity-determining region 3 (CDR3) sequences that were also detected in multiple copies in the blood of the same individuals with SjD. SjD cases displayed a "private" and restricted PB TCR repertoire with reduced clonotype diversity. We identified SjD-associated TCR motifs with the same putative antigen specificity shared between SGs and PB of cases. Their abundances in PB correlated with reduced salivary flow, linking these T cells with pathogenic disease features. Finally, we discovered 2 Ro60 epitopes eliciting an HLA-restricted immune response from expanded SG T cell clones. The comprehensive characterization of SjD TCR repertoires enables the discovery of target antigens and therapeutic strategies.