Murine Studies Research Articles

Anti-PD-1 immunotherapy with adjuvant ablative fractional laser displays increased tumour clearance of squamous cell carcinoma, a murine study.

PD-1 checkpoint inhibitors are used as systemic immunotherapy for locally advanced and metastatic cutaneous squamous cell carcinoma (SCC); however, improved treatment efficacy is urgently needed. In this study, we aimed to investigate the effect of combining systemic anti-PD-1 treatment with adjuvant ablative fractional laser (AFL) in a spontaneous SCC mouse model. Tumours induced by ultraviolet radiation in the strain C3.Cg-Hrhr /TifBomTac were divided into four groups: anti-PD-1-antibody+AFL (n = 33), AFL alone (n = 22) anti-PD-1-antibody alone (n = 31) and untreated controls (n = 46). AFL was given at Day 0 (100 mJ/mb, 5% density), while anti-PD-1-antibody (ip, 200 μg) at Days 0, 2, 4, 6 and 8. Response to treatment was evaluated by tumour growth, survival time and by dividing response to treatment into complete responders (clinically cleared tumours), partial responders (reduced tumour growth rate compared to untreated controls) and non-responders (no decrease in tumour growth rate compared to untreated controls). The strongest tumour response was observed following the combination of systemic anti-PD-1 treatment combined with laser exposure, resulting in the highest percentage of complete responders (24%) compared with untreated controls (0%, p < 0.01), AFL monotherapy (13%, p > 0.05) and anti-PD-1-antibody monotherapy (3%, p > 0.05). Moreover, all three treatment interventions demonstrated significantly reduced tumour growth rates compared with untreated controls (p < 0.01), and the mice had significantly longer survival times (p < 0.01). In conclusion, the combination treatment revealed an improved treatment effect that significantly enhanced the complete tumour clearance not observed with the monotherapies, indicating a possible additive effect of anti-PD-1 with adjuvant AFL in treatment of SCC.

DP1, a multifaceted synthetic peptide: Mechanism of action, activity and clinical potential

AimsMicrobial infections remain a leading cause of mortality worldwide, with Staphylococcus aureus (S. aureus) being a prominent etiological agent, responsible for causing persistent bacterial infections in humans. It is a nosocomial, opportunistic pathogen, capable to propagate within the bloodstream and withstand therapeutic interventions. In the current study, a novel, indigenously designed synthetic antimicrobial peptide (sAMP) has been evaluated for its antimicrobial potential to inhibit the growth and proliferation of S. aureus. Main methodsThe sAMP, designed peptide (DP1) was evaluated for its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against a panel of pathogenic bacterial strains. Membrane mechanistic studies were performed by measuring membrane conductivity via dielectric spectroscopy and visualizing changes in bacterial membrane structure through field emission scanning electron microscopy (FE-SEM). Further, DP1 was tested for its in vivo antimicrobial potential in an S. aureus-induced systemic infection model. Key findingsThe results indicated that DP1 has the potential to inhibit the growth and proliferation of a broad spectrum of Gram-positive, Gram-negative and multidrug-resistant (MDR) bacterial strains. Strong bactericidal effect attributed to change in electrical conductivity of the bacterial cells leading to membrane disruption was observed through dielectric spectroscopy and FE-SEM micrographs. Further, in the in vivo murine systemic infection study, 50 % reduction in S. aureus bioburden was observed within 1 day of the administration of DP1. SignificanceThe results indicate that DP1 is a multifaceted peptide with potent bactericidal, antioxidant and therapeutic properties. It holds significance as a novel drug candidate to effectively combat S. aureus-mediated systemic infections.

Abstract A061: A novel genetically engineered mouse model of Myc-driven pancreatic cancer recapitulates phenotypic heterogeneity, metastasis, and therapy resistance seen in clinical populations

Abstract One of the most aggressive cancers in the US is pancreatic ductal adenocarcinoma (PDAc), whose incidence is expected to rise in the coming years. The standard-of-care treatments have improved over the past few decades, but they still primarily involve harsh chemotherapy cocktails and have only marginally increased overall survival, to a 5-year survival rate of 12 percent. c-MYC (MYC), a potent transcription factor, is frequently dysregulated in PDAc. In PDAc and other cancers, MYC plays a significant role in tumor progression, and its dysregulation has been linked to tumor aggressiveness and therapeutic resistance. In various mouse models of cancer, it has been demonstrated that oncogenic MYC expression controls components of the tumor microenvironment (TME). MYC expression in PDAc has been associated with a desmoplastic immune suppressive TME, though the precise mechanism is still unknown. In this study, we introduce a novel genetically modified mouse model (GEMM) of PDAc that can be used to simulate the disease's heterogeneity and investigate how MYC controls the tumor’s immune and stromal microenvironments. In the pancreas of our KMCERT2 model, both mutant Kras and lowly deregulated Myc are expressed through inducible Cre-driven mechanisms. Our research demonstrates how deregulated MYC cooperates with oncogenic KRASG12D in the adult pancreas to promote PDAc, faithfully reproducing the inter- and intra-tumoral heterogeneity observed in clinical PDAc populations. Currently, an embryonic KrasG12D- and p53 loss/mutant-driven PDAc model (KPC) is used for the majority of murine studies of PDAc. To learn more about the mechanisms underlying observed phenotypes in our KMCERT2 model, RNA- and DNA sequencing were performed on microdissected autochthonous tumor specimens as well as KMCERT2 tumor-derived cell lines. In contrast to the KPC model, our inducible KMCERT2 model of PDAc exhibits genetic alterations, such as CDKN2A loss, comparable to human disease. A distinct loss of nuclear p53 expression is also observed. Intriguingly, multiplexed immunohistochemistry analysis of immune cell composition showed that MYC-driven tumors have a higher density of antigen-presenting cells (APCs) when compared to spontaneous KPC tumors. Standard-of-care medications like gemcitabine and FOLFIRINOX are frequently ineffective against human PDAc. Orthotopic therapeutic studies using our KMCERT2 tumor-derived cell lines show a variety of responses to these therapies, with both resistant and sensitive tumor models, allowing us to use this model to better understand the mechanisms causing therapeutic resistance and to test new therapies. Additionally, we observe consistent liver metastasis in both spontaneous and orthotopic transplant settings. Together, these studies investigate the function of dysregulated MYC expression in murine PDAc metastatic behavior, immune phenotypes, and therapeutic response. It also offers mouse models of PDAc that are both spontaneous and orthotopic, recapitulating the complex and highly metastatic nature of the human disease. Citation Format: Isabel A. English, Patrick J. Worth, Kevin A. MacPherson, Michael B. Heskett, Vidhi Shah, Jackie L. Phipps, Courtney Betts, Shamilene Sivagnanam, Carl Pelz, Amy S. Farrell, Brittany L. Allen-Petersen, Meghan M. Joly, Motoyuki Tsuda, Colin J. Daniel, Jenny Eng, Xiaoyan Wang, Ashley L. Kiemen, Laura D. Wood, Terry K. Morgan, Mary C. Thoma, Jennifer M. Chu, Paul T. Spellman, Lisa M. Coussens, Ellen M. Langer, Rosalie C. Sears. A novel genetically engineered mouse model of Myc-driven pancreatic cancer recapitulates phenotypic heterogeneity, metastasis, and therapy resistance seen in clinical populations [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A061.

Abstract B063: Tertiary lymphoid organogenesis and lymphocyte activation in human organ chips

Abstract The rates of tertiary lymphoid organ (TLO) formation in pancreatic cancer are very low but patients with TLO have dramatically better survival rates. Our goal is to understand how pancreatic cancer suppresses TLO so that we can improve patient survival and reduce recurrence. We integrated human cell lines from pancreatic and lung cancer with either high or low PDL1/L2 expression into our previously described lymphoid follicle (LF) chip (Goyal et al., Adv. Sci, 2022), where peripheral blood mononuclear cells are induced to form 3D TLO-like structures. The hot lung cancer cell line, which expressed high levels of PDL1/L2 and a “hot” phenotype in published murine studies, produced a high levels of cytokines and stimulated increased TLO formation in the LF chip. In contrast, the cold lung and pancreatic cell lines did not induce the cytokine signature or TLOs. Importantly, TLO formation correlated with increased B cell activation, anti-tumor CD8 activity and tumor cell death. We have coupled this in vitro study with analysis of the pancreatic cancer transcriptome from the Cancer Genome Atlas to identify therapeutic targets to promote TLO formation in pancreatic cancer. In ongoing studies, we are assessing the functionality of the lung cancer TLO in vitro and in vivo and identifying therapeutics that may improve TLO formation in pancreatic cancer. Citation Format: Yunhao Zhai, Pranav Prabhala, Lucas Barck, Min Wen Ku, Aditya Patil, Viktor Horvath, Russell A. Gould, Donald E. Ingber, Girija Goyal. Tertiary lymphoid organogenesis and lymphocyte activation in human organ chips [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B063.

Co-Delivery of a Novel Lipidated TLR7/8 Agonist and Hemagglutinin-Based Influenza Antigen Using Silica Nanoparticles Promotes Enhanced Immune Responses.

Co-delivery of antigens and adjuvants to the same antigen-presenting cells (APCs) can significantly improve the efficacy and safety profiles of vaccines. Here, we report amine-grafted silica nanoparticles (A-SNP) as a tunable vaccine co-delivery platform for TLR7/8 agonists along with the recombinant influenza antigen hemagglutinin H7 (H7) to APCs. A-SNP of two different sizes (50 and 200 nm) were prepared and coated with INI-4001 at different coating densities, followed by co-adsorption of H7. Both INI-4001 and H7 showed >90% adsorption to the tested A-SNP formulations. TNF-α and IFN-α cytokine release by human peripheral blood mononuclear cells as well as TNF-α, IL-6, and IL-12 release by mouse bone marrow-derived dendritic cells revealed that the potency of the INI-4001-adsorbed A-SNP (INI-4001/A-SNP) formulations was improved relative to aqueous formulation control. This improved potency was dependent on particle size and ligand coating density. In addition, slow-release profiles of INI-4001 were measured from INI-4001/A-SNP formulations in plasma with 30-50% INI-4001 released after 7 days. In vivo murine immunization studies demonstrated significantly improved H7-specific humoral and Th1/Th17-polarized T cell immune responses with no observed adverse reactions. Low-density 50 nm INI-4001/A-SNP elicited significantly higher IFN-γ and IL-17 induction over that of the H7 antigen-only group and INI-4001 aqueous formulation controls. In summary, this work introduces an effective and biocompatible SNP-based co-delivery platform that enhances the immunogenicity of TLR7/8 agonist-adjuvanted subunit influenza vaccines.

Diverse array of neutralizing antibodies elicited upon Spike Ferritin Nanoparticle vaccination in rhesus macaques

The repeat emergence of SARS-CoV-2 variants of concern (VoC) with decreased susceptibility to vaccine-elicited antibodies highlights the need to develop next-generation vaccine candidates that confer broad protection. Here we describe the antibody response induced by the SARS-CoV-2 Spike Ferritin Nanoparticle (SpFN) vaccine candidate adjuvanted with the Army Liposomal Formulation including QS21 (ALFQ) in non-human primates. By isolating and characterizing several monoclonal antibodies directed against the Spike Receptor Binding Domain (RBD), N-Terminal Domain (NTD), or the S2 Domain, we define the molecular recognition of vaccine-elicited cross-reactive monoclonal antibodies (mAbs) elicited by SpFN. We identify six neutralizing antibodies with broad sarbecovirus cross-reactivity that recapitulate serum polyclonal antibody responses. In particular, RBD mAb WRAIR-5001 binds to the conserved cryptic region with high affinity to sarbecovirus clades 1 and 2, including Omicron variants, while mAb WRAIR-5021 offers complete protection from B.1.617.2 (Delta) in a murine challenge study. Our data further highlight the ability of SpFN vaccination to stimulate cross-reactive B cells targeting conserved regions of the Spike with activity against SARS CoV-1 and SARS-CoV-2 variants.

A NOVEL BIOMIMETIC BONE ADHESIVE: TRANSLATION FROM SMALL TO LARGE ANIMAL PRECLINICAL MODEL ON THE PATH TO FIRST IN-HUMAN USE

Surgeons treating fractures with many small osteochondral fragments have often expressed the clinical need for an adhesive to join such fragments, as an adjunct to standard implants. If an adhesive would maintain alignment of the articular surfaces and subsequently heal it could result in improved clinical outcomes. However, there are no bone adhesives available for clinical indications and few pre-clinical models to assess safety and efficacy of adhesive biomaterial candidates. A bone adhesive candidate based on water, α-TCP and an amino acid phosphoserine was evaluated in-vivo in a novel murine bone core model (preliminary results presented EORS 2019) in which excised bone cores were glued back in place and harvested @ 0, 3, 7, 14, 28 and 42days. Adhesive pull-out strength was demonstrated 0–28 days, with a dip at 14 days increasing to 11.3N maximum. Histology 0–42 days showed the adhesive progressively remodelling to bone in both cancellous and cortical compartments with no signs of either undesirable inflammation or peripheral ectopic bone formation. These favourable results suggested translation to a large animal model.A porcine dental extraction socket model was subsequently developed where dental implants were affixed only with the adhesive. Biomechanical data was collected @ 1, 14, 28 and 56 days, and histology at 1,14,28 and 56 days. Adhesive strength assessed by implant pull-out force increased out to 28 days and maintained out to 56 days (282N maximum) with failure only occurring at the adhesive bone interface. Histology confirmed the adhesive's biocompatibility and osteoconductive behavior. Additionally, remodelling was demonstrated at the adhesive-bone interface with resorption by osteoclast-like cells and followed by new bone apposition and substitution by bone. Whilst the in-vivo dental implant data is encouraging, a large animal preclinical model is needed (under development) to confirm the adhesive is capable of healing, for example, loaded osteochondral bone fragments.Acknowledgements: The murine study was supported, in part, by the Swedish Foundation for Strategic Research (#RMA15-0110).

Preclinical evaluation of an 18F-labeled Nε-acryloyllysine piperazide for covalent targeting of transglutaminase 2.

Transglutaminase 2 (TGase2) is a multifunctional protein and has a prominent role in various (patho)physiological processes. In particular, its transamidase activity, which is rather latent under physiological conditions, gains importance in malignant cells. Thus, there is a great need of theranostic probes for targeting tumor-associated TGase 2, and targeted covalent inhibitors appear to be particularly attractive as vector molecules. Such an inhibitor, equipped with a radionuclide suitable for noninvasive imaging, would be supportive for answering the general question on the possibility for functional characterization of tumor-associated TGase 2. For this purpose, the recently developed 18F-labeled Nε-acryloyllysine piperazide [18F]7b, which is a potent and selective irreversible inhibitor of TGase2, was subject to a detailed radiopharmacological characterization herein. An alternative radiosynthesis of [18F]7b is presented, which demands less than 300µg of the respective trimethylammonio precursor per synthesis and provides [18F]7b in good radiochemical yields (17 ± 7%) and high (radio)chemical purities (≥ 99%). Ex vivo biodistribution studies in healthy mice at 5 and 60min p.i. revealed no permanent enrichment of 18F-activity in tissues with the exception of the bone tissue. In vivo pretreatment with ketoconazole and in vitro murine liver microsome studies complemented by mass spectrometric analysis demonstrated that bone uptake originates from metabolically released [18F]fluoride. Further metabolic transformations of [18F]7b include mono-hydroxylation and glucuronidation. Based on blood sampling data and liver microsome experiments, pharmacokinetic parameters such as plasma and intrinsic clearance were derived, which substantiated the apparently rapid distribution of [18F]7b in and elimination from the organisms. A TGase2-mediated uptake of [18F]7b in different tumor cell lines could not be proven. Moreover, evaluation of [18F]7b in melanoma tumor xenograft models based on A375-hS100A4 (TGase2 +) and MeWo (TGase 2 -) cells by ex vivo biodistribution and PET imaging studies were not indicative for a specific targeting. [18F]7b is a valuable radiometric tool to study TGase2 in vitro under various conditions. However, its suitability for targeting tumor-associated TGase2 is strongly limited due its unfavorable pharmacokinetic properties as demonstrated in rodents. Consequently, from a radiochemical perspective [18F]7b requires appropriate structural modifications to overcome these limitations.

Perioperative Immune Checkpoint Blockade for Muscle-Invasive and Metastatic Bladder Cancer.

Checkpoint inhibitors offer promise in treating muscle-invasive and metastatic bladder cancer, but the optimal timing of their administration-neoadjuvant or adjuvant-remains unclear. To determine the efficacy of combining checkpoint inhibition with standard cisplatin-based chemotherapy, we conducted a phase II trial of neoadjuvant anti-PD-1 (αPD-1) and anti-CTLA-4 (αCTLA-4), in combination with cisplatin-gemcitabine, for patients with muscle-invasive bladder cancer prior to radical cystectomy. In addition, a novel murine model of spontaneous metastatic bladder cancer was used to compare the efficacy of neoadjuvant versus adjuvant anti-PD-L1 (αPD-L1) treatment. The clinical trial was closed prematurely due to the industry's withdrawal of drug provision. Adverse events were observed in all patients; however, serious adverse events were not observed in any patient. A complete pathologic response was observed in 50% of the 4 patients enrolled. Response to treatment was significantly associated with elevated urinary T cells including CD8+ and IFNγ+ CD4+ T cells, suggesting potential reinforcement of immune responses by neoadjuvant αPD-1 and αCTLA-4 against bladder tumor cells. These findings suggest that combining chemotherapy and immunotherapy in the neoadjuvant setting could be safe. However, the complete response rate of this four-drug regimen was modest and emphasizes the need for randomized controlled trials to properly assess immunotherapy efficacy in the neoadjuvant setting. In corresponding murine studies, the MB49-met model consistently displayed widespread metastasis, including tumor growth in the lungs, liver, and bowel mesentery, within 20 days of subcutaneous transplantation. Mice receiving surgery plus neoadjuvant αPD-L1 or adjuvant αPD-L1 exhibited improved survival compared to those receiving only αPD-L1. However, no significant difference in survival was observed between the neoadjuvant and adjuvant αPD-L1 cohorts. Furthermore, the timing of neoadjuvant therapy administration (early vs. late) did not significantly impact survival. This study highlights the potential of perioperative immunotherapy in the treatment of locally advanced and metastatic bladder cancer.

Estrogen deficiency influences SEC23A gene expression in the odontogenic region of incisors – a murine model study

Estrogen deficiency influences SEC23A gene expression in the odontogenic region of incisors – a murine model study

Therapeutic potential of ghrelin/GOAT/GHSR system in gastrointestinal disorders.

Ghrelin, a peptide primarily secreted in the stomach, acts via the growth hormone secretagogue receptor (GHSR). It regulates several physiological processes, such as feeding behavior, energy homeostasis, glucose and lipid metabolism, cardiovascular function, bone formation, stress response, and learning. GHSR exhibits significant expression within the central nervous system. However, numerous murine studies indicate that ghrelin is limited in its ability to enter the brain from the bloodstream and is primarily confined to specific regions, such as arcuate nucleus (ARC) and median eminence (ME). Nevertheless, the central ghrelin system plays an essential role in regulating feeding behavior. Furthermore, the role of vagal afferent fibers in regulating the functions of ghrelin remains a major topic of discussion among researchers. In recent times, numerous studies have elucidated the substantial therapeutic potential of ghrelin in most gastrointestinal (GI) diseases. This has led to the development of numerous pharmaceutical agents that target the ghrelin system, some of which are currently under examination in clinical trials. Furthermore, ghrelin is speculated to serve as a promising biomarker for GI tumors, which indicates its potential use in tumor grade and stage evaluation. This review presents a summary of recent findings in research conducted on both animals and humans, highlighting the therapeutic properties of ghrelin system in GI disorders.

Pregnancy-related factors induce immune tolerance through regulation of sCD83 release.

A well-balanced maternal immune system is crucial to maintain fetal tolerance in case of infections during pregnancy. Immune adaptations include an increased secretion of soluble mediators to protect the semi-allogeneic fetus from excessive pro-inflammatory response. B lymphocytes acquire a higher capacity to express CD83 and secrete soluble CD83 (sCD83) upon exposure to bacteria-derived components such as LPS. CD83 possesses immune modulatory functions and shows a promising therapeutic potential against inflammatory conditions. The administration of sCD83 to pregnant mice reduces LPS-induced abortion rates. The increased CD83 expression by endometrial B cells as compared to peripheral blood B cells suggests its modulatory role in the fetal tolerance, especially in the context of infection. We postulate that in pregnancy, CD83 expression and release is controlled by pregnancy-related hormones. The intra- and extracellular expression of CD83 in leukocytes from peripheral blood or decidua basalis and parietalis at term were analyzed by flow cytometry. After treatment with pregnancy-related hormones and LPS, ELISA and qPCR were performed to study sCD83 release and CD83 gene expression, respectively. Cleavage prediction analysis was used to find potential proteases targeting CD83. Expression of selected proteases was analyzed by ELISA. Higher levels of CD83 were found in CD11c+ dendritic cells, CD3+ T cells and CD19+ B cells from decidua basalis and decidua parietalis after LPS-stimulation in vitro. An increase of intracellular expression of CD83 was also detected in CD19+ B cells from both compartments. Stimulated B cells displayed significantly higher percentages of CD83+ cells than dendritic cells and T cells from decidua basalis and peripheral blood. Treatment of B lymphocytes with pregnancy-related molecules (E2, P4, TGF-β1 and hCG) enhanced the LPS-mediated increase of CD83 expression, while dexamethasone led to a reduction. Similarly, the release of sCD83 was increased under TGF-β1 treatment but decreased upon dexamethasone stimulation. Finally, we found that the hormonal regulation of CD83 expression is likely a result from a balance between gene transcription from CD83 and the modulation of the metalloproteinase MMP-7. Thus, data supports and complements our previous murine studies on hormonal regulation of CD83 expression, reinforcing its immunomodulatory relevance in anti-bacterial responses during pregnancy.

The involvement of oral bacteria in inflammatory bowel disease.

Microorganisms play an important role in the pathogenesis of inflammatory bowel disease (IBD). The oral cavity, the second-largest microbial niche, is connected to the gastro-intestinal tract. Ectopic gut colonization by oral microbes is a signature of IBD. Current studies suggest that patients with IBD often report more oral manifestations and these oral issues are closely linked with disease activity. Murine studies have indicated that several oral microbes exacerbate intestinal inflammation. Moreover, intestinal inflammation can promote oral microbial dysbiosis and the migration of oral microbes to the gastro-intestinal tract. The reciprocal consequences of oral microbial dysbiosis and IBD, specifically through metabolic alterations, have not yet been elucidated. In this review, we summarize the relationship between oral bacteria and IBD from multiple perspectives, including clinical manifestations, microbial dysbiosis, and metabolic alterations, and find that oral pathogens increase anti-inflammatory metabolites and decrease inflammation-related metabolites.

Human IgM-expressing memory B cells.

A hallmark of T cell dependent (TD) humoral immune responses is the generation of long-lived memory B cells. The generation of these cells occurs primarily in the germinal center (GC) reaction, where antigen-activated B cells undergo affinity maturation as a major consequence of the combined processes of proliferation, somatic hypermutation of their immunoglobulin V (IgV) region genes, and selection for improved affinity of their B-cell antigen receptors. As many B cells also undergo class-switching to IgG or IgA in these TD responses, there was traditionally a focus on class-switched memory B cells in both murine and human studies on memory B cells. However, it has become clear that there is also a large subset of IgM-expressing memory B cells, which have important phenotypic and functional similarities but also differences to class-switched memory B cells. There is an ongoing discussion about the origin of distinct subsets of human IgM+ B cells with somatically mutated IgV genes. We argue here that the vast majority of human IgM-expressing B cells with somatically mutated IgV genes in adults is indeed derived from GC reactions, even though a generation of some mostly lowly mutated IgM+ B cells from other differentiation pathways, mainly in early life, may exist.

Soluble PD-L1 reprograms blood monocytes to prevent cerebral edema and facilitate recovery after ischemic stroke

Acute cerebral ischemia triggers a profound inflammatory response. While macrophages polarized to an M2-like phenotype clear debris and facilitate tissue repair, aberrant or prolonged macrophage activation is counterproductive to recovery. The inhibitory immune checkpoint Programmed Cell Death Protein 1 (PD-1) is upregulated on macrophage precursors (monocytes) in the blood after acute cerebrovascular injury. To investigate the therapeutic potential of PD-1 activation, we immunophenotyped circulating monocytes from patients and found that PD-1 expression was upregulated in the acute period after stroke. Murine studies using a temporary middle cerebral artery (MCA) occlusion (MCAO) model showed that intraperitoneal administration of soluble Programmed Death Ligand-1 (sPD-L1) significantly decreased brain edema and improved overall survival. Mice receiving sPD-L1 also had higher performance scores short-term, and more closely resembled sham animals on assessments of long-term functional recovery. These clinical and radiographic benefits were abrogated in global and myeloid-specific PD-1 knockout animals, confirming PD-1+ monocytes as the therapeutic target of sPD-L1. Single-cell RNA sequencing revealed that treatment skewed monocyte maturation to a non-classical Ly6Clo, CD43hi, PD-L1+ phenotype. These data support peripheral activation of PD-1 on inflammatory monocytes as a therapeutic strategy to treat neuroinflammation after acute ischemic stroke.

Ongoing production of tissue-resident macrophages from hematopoietic stem cells in healthy adult macaques

AbstractMacrophages orchestrate tissue immunity from the initiation and resolution of antimicrobial immune responses to the repair of damaged tissue. Murine studies demonstrate that tissue-resident macrophages are a heterogenous mixture of yolk sac–derived cells that populate the tissue before birth, and bone marrow–derived replacements recruited in adult tissues at steady-state and in increased numbers in response to tissue damage or infection. How this translates to species that are constantly under immunologic challenge, such as humans, is unknown. To understand the ontogeny and longevity of tissue-resident macrophages in nonhuman primates (NHPs), we use a model of autologous hematopoietic stem progenitor cell (HSPC) transplantation with HSPCs genetically modified to be marked with clonal barcodes, allowing for subsequent analysis of clonal ontogeny. We study the contribution of HSPCs to tissue macrophages, their clonotypic profiles relative to leukocyte subsets in the peripheral blood, and their transcriptomic and epigenetic landscapes. We find that HSPCs contribute to tissue-resident macrophage populations in all anatomic sites studied. Macrophage clonotypic profiles are dynamic and overlap significantly with the clonal hierarchy of contemporaneous peripheral blood monocytes. Epigenetic and transcriptomic landscapes of HSPC-derived macrophages are similar to tissue macrophages isolated from NHPs that did not undergo transplantation. We also use in vivo bromodeoxyuridine infusions to monitor tissue macrophage turnover in NHPs that did not undergo transplantation and find evidence for macrophage turnover at steady state. These data demonstrate that the life span of most tissue-resident macrophages is limited and can be replenished continuously from HSPCs.

Xenografted human microglia in response to Alzheimer’s disease Aβ pathology

AbstractBackgroundNeuroinflammation is a pathological hallmark of Alzheimer’s disease (AD). Murine studies have revealed that mouse microglia can adopt several cell states in response to disease insults. However, single‐nuclei RNA sequencing studies have found divergent results when recalling those cell states in human post‐mortem tissue.MethodTo overcome this limitation, we have sequenced 127,000 single cell human microglia isolated from an AD xenotransplantation model.ResultIn response to plaques, human microglia can adopt several cell states including a disease‐associated microglia (DAM) and an antigen‐presenting response (HLA). When reacting to Aβ soluble aggregates, human microglia produces a pro‐inflammatory response cytokine response (CRM). TREM2 and APOE polymorphisms affect the development of the DAM‐HLA response, suggesting an important role of this response in AD.ConclusionOverall, this multi‐faceted response to amyloid pathologies highlights a complex scenario where these distinct phenotypes might influence the outcome on the disease.

Pharmacodynamic differences between racemic ibuprofen and dexibuprofen in murine preclinical study

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the best therapeutic options to treat pain, but their use is restricted by their adverse effects. In this study, the pharmacological profile of ibuprofen and dexibuprofen was evaluated using the murine acetic acid writhing test, and the participation of naltrexone, naltrindole, nor-binaltorphimine, L-NAME, risperidone, and tropisetron in the antinociceptive efficacy. Antinociception was assessed by dose–response curves to ibuprofen and dexibuprofen before and after the i.p. administration of 1,0 mg/kg of naltrexone, or naltrindole, or norbinaltorphimine, or 5 mg/kg of L-NAME, 0,5 mg/kg of risperidone, or tropisetron in the murine assay. Results are presented as means ± SEM and differences calculated by one-way ANOVA followed by Tukey's post-test. Ibuprofen and dexibuprofen produced a dose-dependent antinociceptive effect with different potency. After pretreatment of mice with naltrexone, naltrindole, nor-binaltorphimine, L-NAME, risperidone, or tropisetron, a significant increase in ibuprofen efficacy was obtained, however, no effect on dexibuprofen activity was obtained. Data demonstrate that ibuprofen and dexibuprofen induce effective antinociception in the acetic acid writhing test, either directly, through COX inhibition, or indirectly, through the modulatory effects of opioid or serotonin, or nitric oxide receptors. These actions are complex since the effects depending on the chemical structure of the NSAID. Thus, a racemic compound (ibuprofen) induces a significant increase in nociceptive efficacy. However, they have no effect on the dextrorotatory enantiomer (dexibuprofen).

Heterogeneity of Human Invariant Natural Killer T Cells, Including Novel Naïve-like CD8 + and Temra-like CD4 -CD8 - Populations, Revealed through Single Cell RNA-Sequencing

Introduction: Invariant natural killer T (iNKT) cells, with their inherent lack of allorecognition, are a promising platform for universal donor cellular therapies. Murine studies have shown that the iNKT cell population is comprised of subsets, similar to T helper cell subsets, with distinct patterns of cytokine expression and functional capacities. The adoptive transfer of iNKT2 or iNKT17 cells suppresses graft-versus-host disease in murine models, while iNKT1 cells have cytotoxic capacity towards malignant cells, suggesting that the composition of iNKT-based cellular therapies could be optimized by using different subsets in different disease settings. However, the heterogeneity of human iNKT cells remains poorly understood, and the phenotypic identity of functionally distinct subsets remains elusive. Herein, we performed single cell RNA-sequencing (scRNA-seq) of purified human iNKT cells from peripheral blood (PB), cord blood (CB), thymus, and bone marrow (BM) to reveal distinct subsets. Methods: Human iNKT cells were enriched by magnetic bead-based positive selection (Stem Cell Technologies) utilizing anti-Vβ11 antibody (Beckman Coulter), followed by fluorescence activated cell sorting including anti-Vα24 antibody. scRNA-seq libraries were generated using the Rhapsody platform (Becton Dickinson) employing a targeted panel (PB only) or whole transcriptome analysis (all tissues). Data was processed using the BD Rhapsody pipeline (Seven Bridges) followed by analysis in R (Seurat v4.1.0). Results: ScRNA-seq of iNKT cells from PB, CB, thymus, and BM revealed 9 transcriptionally distinct clusters derived from cells from each tissue (Fig 1A). While iNKT cells from some tissue sources dominated certain clusters, PB-derived iNKT cells were relatively equally distributed among all clusters. We found that clusters of human iNKT cells expressing TBX21 co-express RORC (Clusters 2 &amp; 6, Fig 1A-B), in contrast to murine iNKT cells in which TBX21 and RORC expression isolates to distinct clusters. iNKT cells in Clusters 2 &amp; 6 also upregulated genes suggesting cytotoxic function as well as receptors important for natural killer cell function, therefore we characterized cells in these two clusters as a Th1/17/NK-like population. Interestingly, the incorporation of oligomer-conjugated antibodies into our analyses allowed the detection that Cluster 6 was CD45RA + with absent CCR7 transcript, similar to that of T effector memory CD45RA + (TEMRA) cells. Other clusters which downregulated both TBX21 and RORC displayed relative upregulation of ZBTB16 and may represent Th2-like iNKT cells (Clusters 1, 4, &amp; 7). iNKT cells from these clusters also expressed IL4R and other genes important for T cell function. Surprisingly, despite excluding CD24 + iNKT precursor cells, we found several clusters with relatively minimal expression of any of these canonical transcription factors (Clusters 0, 3, 5, &amp; 8). These four clusters were also characterized by upregulation of SELL, CCR7, and CD45RA, suggesting a naïve or undifferentiated phenotype, and were especially abundant in the thymus, though found in the periphery as well. We further found that CD4 + iNKT cells were comprised of Th2-like clusters as well as a Th1/17/NK-like cluster (Cluster 2), a population previously described in mice. These results suggest that CD4 expression may not clearly distinguish functionally distinct subsets. Importantly, our results include the first transcriptional analysis of CD8 + human iNKT cells, which (in our PB-only analysis) revealed two distinct CD8 + clusters, one similar to the iNKT1/17/NK-like population and one similar to the naïve/undifferentiated population. Conclusions: Collectively, these data reveal novel insights into the heterogeneity of human iNKT cells from multiple immunologic tissues. Our transcriptomic data predict that 1) human iNKT cells include a novel TBX21 +/RORC + population not found in mice; 2) naïve/undifferentiated iNKT cells are present not only in the thymus, but also in bone marrow and peripheral blood; and 3) human CD8 + iNKT cells include both Th1/17/NK-like and naïve/undifferentiated populations. These insights provide a critical foundation for optimal use of human iNKT cells in the development of cellular therapies. Studies to correlate transcriptome and function in these novel human iNKT cell populations are underway.

Murine Infusion Studies of Infused Human Megakaryocytes Support a “Catch-and-Release” Model of Thrombopoiesis

Introduction: Thrombopoiesis, the process by which megakaryocytes (Mks) release platelets, is still not well understood, including where it occurs and how a Mk releases its platelet content. The present study, based on infused human Mks (hMks) into immunocompromised mice, and measurements of the subsequent presence of nucleated Mks and anucleated cytoplasmic fragments in the lungs and in the peripheral blood were carried out to provide new insights into this process. Method: To gain a deeper understanding of the role of the lung in thrombopoiesis, we performed quantitative, temporal measurements of the size of human CD41 +CD42 + nucleated Mks and anucleated cytoplasmic fragments after tail-vein infusion of either mature (Day 12 of culture from CD34 + hematopoietic stem/progenitor cells (HSPCs)) hMks or immature (Day 7 of culture from CD34 + HSPCs) in NOD-scid gamma (NSG) mice. Data was collected from both the pulmonary bed by in situ microscopy ( Figure 1) and in the peripheral blood by flow cytometry ( Figure 2). To distinguish in the peripheral blood large cytoplasmic fragments from recirculating hMks, Hoechst-nuclear staining was done prior to flow cytometric analysis For size references, isolated donor platelets and input Hoechst-stained hMks, containing platelet-like particles (PLPs), were concurrently analyzed ( Figure 2, bottom left). Results: By pulmonary in situ microscopy, we found that infused mature hMks were entrapped on their first passage through the lungs. Over the subsequent hour, anucleate cytoplasmic fragments ( Figure 1, left) recycle to the lungs becoming increasingly smaller in size over the hour-long study. Infused immature hMks also shed cytoplasmic fragments, but these began much smaller in size though these, too, reduced in size over time ( Figure 1, right). In the peripheral blood, mature CD41 +CD42 + hMks made up &amp;lt;2% of all the circulating fragments ( Figure 2, top left). These hMks initially were comparable in size to the input hMks ( Figure 2, bottom), but decreased in size over time, presumably due to shedding of their cytoplasm. Already by 10 mins post-infusion, a dominant group of large-sized (L), anucleated CD41 +CD42 + cytoplasmic fragments were observed, slightly smaller than the input Hoechst-stained hMks. Their presence decreased, reaching near-zero in &amp;lt;20 hrs. In contrast, mid-sized (M), cytoplasmic fragments, comparable in size to donor platelets, increased in abundance over time. Small-sized (S), cytoplasmic fragments were only present at 10 mins and were largely the input PLPs. In contrast, up to 34% of the circulating CD41 +CD42 + fragments after infusing immature hMks were nucleated ( Figure 2, right), suggesting that unlike mature hMks that are efficiently entrapped by the murine lungs, many immature hMks were small enough to pass through the murine vascular beds and recycle multiple times without completely releasing their cytoplasm. Conclusions: In the murine lungs, mature hMks are efficiently entrapped and within minutes shed large cytoplasmic fragments. These cytoplasmic fragments then recycle back to the lung for further processing, resulting in a near complete release of platelet-size fragments by 90 mins. These findings are consistent with the recent observations of Zhao X, et al., using a distinct in vivo murine lung/heart system (PMC10329040) except that infused murine Mks recycled nucleated. Whether this difference is a true species-difference or related to hMks traversing the murine vasculature needs to be explored, but in aggregate, these two studies demonstrate that thrombopoiesis is a complex process that begins when whole Mks and/or large cytoplasmic fragments are released intravascular from the marrow, spleen and/or lung. Subsequently, the Mks and large cytoplasmic fragments are then converted into smaller fragments and finally platelets by repetitive cycles of “catch-and-release” in the pulmonary bed. The mechanistic basis controlling this process needs better elucidation, but at the same time, offers insights of potential clinical application.