Blockade of PD-1/PD-L1 Pathway Enhances the Antigen-Presenting Capacity of Fibrocytes

Fibrocytes in tumor microenvironment: Identification of their fraction and novel therapeutic strategy

Fibrocytes were identified as bone marrow-derived myeloid cells that also have fibroblast-like phenotypes, such as ECM production and differentiation to myofibroblasts. Although fibrocytes are known to contribute to various types of tissue fibrosis, their functions in the tumor microenvironment are unclear. We focused on fibrocytes as pivotal regulators of tumor progression. Our previous studies have indicated that fibrocytes induce angiogenesis and cancer stem cell-like phenotypes by secreting various growth factors. In contrast, immune checkpoint inhibitor (ICI)-treated fibrocytes demonstrated antigen-presenting capacity and enhanced antitumor T cell proliferation. Taken together, these findings indicate that fibrocytes have multiple effects on tumor progression. However, the detailed phenotypes of fibrocytes have not been fully elucidated because the isolation of distinct fibrocyte clusters has not been achieved without culturing in ECM-coated conditions or intracellular staining of ECM. The development of single-cell analyses partially resolves these problems. Single-cell RNA sequences in CD45+ immune cells from tumor tissue identified ECM-expressing myeloid-like cells as distinct fibrocyte clusters. In addition, these findings enabled the isolation of tumor-infiltrating fibrocytes as CD45+CD34+ cells. These tumor-infiltrating fibrocytes demonstrated both antigen-presenting ability and differentiation into myofibroblast-like cancer-associated fibroblasts. Considering these functions of fibrocytes in tumor progression, molecular-targeting agents for the migration, activity, and differentiation of fibrocytes are promising therapeutic strategies. Furthermore, identification of specific cell surface markers and master regulators of fibrocytes will advance novel fibrocyte-targeting therapies. In this review, we discuss the multiple roles of tumor-infiltrating fibrocytes and novel cancer therapeutic strategies.

The possible pathogenesis of liver fibrosis: therapeutic potential of natural polyphenols

Liver fibrosis is the formation of a fibrous scar resulting from chronic liver injury, independently from etiology. Although many of the mechanical details remain unknown, activation of hepatic stellate cells (HSCs) is a central driver of liver fibrosis. Extracellular mechanisms such as apoptotic bodies, paracrine stimuli, inflammation, and oxidative stress are critical in activating HSCs. The potential for liver fibrosis to reverse after removing the causative agent has heightened interest in developing antifibrotic therapies. Polyphenols, the secondary plant metabolites, have gained attention because of their health-beneficial properties, including well-recognized antioxidant and anti-inflammatory activities, in the setting of liver fibrosis. In this review, we present an overview of the mechanisms underlying liver fibrosis with a specific focus on the activation of resident HSCs. We highlight the therapeutic potential and promising role of natural polyphenols to mitigate liver fibrosis pathogenesis, focusing on HSCs activation. We also discuss the translational gap from preclinical findings to clinical treatments involved in natural polyphenols in liver fibrosis.

Recognition of HIV-1-infected fibrocytes lacking Nef-mediated HLA-B downregulation by HIV-1-specific T cells

Fibrocytes were reported to be host cells for HIV-1, but the immunological recognition of HIV-1-infected fibrocytes has not been studied. Here, we investigated the recognition of HIV-1-infected fibrocytes by HIV-1-specific CD8+ T cells. CD8+ T cells specific for five HIV-1 epitopes (HLA-A*24:02-restricted, HLA-B*52:01-restricted, and HLA-C*12:02-restricted epitopes) produced IFN-γ and expressed CD107a after coculture with HIV-1-infected fibrocytes. HIV-1-infected fibrocytes were effectively killed by HIV-1-specific CD8+ T cells. Although it is well known that HIV-1 Nef-mediated downregulation of HLA-A and HLA-B critically affects the T cell recognition of HIV-1-infected CD4+ T cells and HIV-1-infected macrophages, Nef downregulated HLA-A, but not HLA-B, in HIV-1-infected fibrocytes. These findings suggested that HIV-1-specific CD8+ T cells could recognize HIV-1-infected fibrocytes more strongly than HIV-1-infected CD4+ T cells or HIV-1-infected macrophages. HIV-1-infected fibrocytes were also recognized by HIV-1-specific HLA-DR-restricted T cells, indicating that HIV-1-infected fibrocytes can present HIV-1 epitopes to helper T cells. Collectively, these findings suggest that fibrocytes have an important role as antigen-presenting cells during HIV-1 infection. The present study demonstrates effective recognition of HIV-1-infected fibrocytes by HIV-1-specific T cells and suggests possible roles of fibrocytes in the induction and maintenance of HIV-1-specific T cells.

IMPORTANCE

Fibrocytes were identified as unique hematopoietic cells with the features of both macrophages and fibroblasts and were demonstrated to be host cells for HIV-1. However, T cell recognition of HIV-1-infected fibrocytes has not been studied. We investigated the recognition of HIV-1-infected fibrocytes by HIV-1-specific T cells. HIV-1-infected fibrocytes were effectively recognized and killed by CD8+ T cells specific for HIV-1 epitopes presented by HLA-A, HLA-B, or HLA-C and were recognized by HIV-1-specific HLA-DR-restricted CD4+ T cells. HIV-1 Nef-mediated downregulation of HLA-A and HLA-B was found in HIV-1-infected CD4+ T cells, whereas Nef did not downregulate HLA-B in HIV-1-infected fibrocytes. These results suggest that HIV-1-specific CD8+ T cells recognize HIV-1-infected fibrocytes more strongly than HIV-1-infected CD4+ T cells. The present study suggests the importance of fibrocytes in the induction and maintenance of HIV-1-specific T cells.

Cellular therapeutics and immunotherapies in wound healing - on the pulse of time?

Chronic, non-healing wounds represent a significant challenge for healthcare systems worldwide, often requiring significant human and financial resources. Chronic wounds arise from the complex interplay of underlying comorbidities, such as diabetes or vascular diseases, lifestyle factors, and genetic risk profiles which may predispose extremities to local ischemia. Injuries are further exacerbated by bacterial colonization and the formation of biofilms. Infection, consequently, perpetuates a chronic inflammatory microenvironment, preventing the progression and completion of normal wound healing. The current standard of care (SOC) for chronic wounds involves surgical debridement along with localized wound irrigation, which requires inpatient care under general anesthesia. This could be followed by, if necessary, defect coverage via a reconstructive ladder utilizing wound debridement along with skin graft, local, or free flap techniques once the wound conditions are stabilized and adequate blood supply is restored. To promote physiological wound healing, a variety of approaches have been subjected to translational research. Beyond conventional wound healing drugs and devices that currently supplement treatments, cellular and immunotherapies have emerged as promising therapeutics that can behave as tailored therapies with cell- or molecule-specific wound healing properties. However, in contrast to the clinical omnipresence of chronic wound healing disorders, there remains a shortage of studies condensing the current body of evidence on cellular therapies and immunotherapies for chronic wounds. This review provides a comprehensive exploration of current therapies, experimental approaches, and translational studies, offering insights into their efficacy and limitations. Ultimately, we hope this line of research may serve as an evidence-based foundation to guide further experimental and translational approaches and optimize patient care long-term.

Single-cell RNA sequencing reveals the effects of anti-PD-L1 therapy on 3LL lung cancer model and its tumor microenvironment

PD-L1 is expressed on antigen-presenting cells and tumor cells, thus allows tumor cells to escape immune surveillance. Moreover, targeting PD-L1 was also recommended and selected as important immune checkpoint inhibitors (ICIs) strategy in the treatment of advanced cancers due to the safety and activity. However, the detailed alteration of tumor microenvironment (TME) upon anti-PD-L1 therapy in lung cancer tumor model still needs to be resolved. In our present study, first, we characterized PD-L1 expression in human lung adenocarcinoma tissues by using public data, then we established the subcutaneous tumor-bearing model by using murine lung cancer cell line 3LL to perform the anti-PD-L1 therapy and the single-cell RNA sequencing (scRNA-seq) to reveal the remodeling of TME. We confirmed that PD-L1 blockade significantly inhibited tumor progression in 3LL mouse lung cancer model. The scRNA-seq depicted the detailed TME landscape of 3LL tumor model upon anti-PD-L1 treatment. Five major populations according to the marker genes were identified, including tumor cells, stromal cells, myeloid cells, T cells, and NK cells. In addition, we found that anti-PD-L1 treatment enhanced tumor immunogenicity and promoted inflammation in TME and promoted cancer-associated fibroblasts (CAFs)-mediated T-cell migration and infiltration. We also found that anti-PD-L1 treatment can increase dendritic cells (DCs) population and enhance the antigen-presenting ability to CD8+T cells and promote the transition of monocytes to macrophages and tumor-associated macrophages 2 (TAM2) to TAM1. We also revealed that Nfatc1 was up-regulated in the anti-PD-L1 treatment group, the frequencies of effector CD8+T cells, exhausted CD8+T cells, cycling T cells, and NKT were increased, and the frequencies of conventional CD4+T cells, Treg, IFN-induced T cells, and γδT cells were decreased. Therefore, our scRNA-seq data of the lung cancer tumor model upon anti-PD-L1 treatment made a comprehensive presentation and description about the remodeling of TME and will benefit us to understand the underlying mechanisms and to design combinational therapeutic strategies based on anti-PD-L1 therapy against lung cancer.

Short-range interactions between fibrocytes and CD8+ T cells in COPD bronchial inflammatory response

Bronchi of chronic obstructive pulmonary disease (COPD) are the site of extensive cell infiltration, allowing persistent contact between resident cells and immune cells. Tissue fibrocytes interaction with CD8⁺ T cells and its consequences were investigated using a combination of in situ, in vitro experiments and mathematical modeling. We show that fibrocytes and CD8⁺ T cells are found in the vicinity of distal airways and that potential interactions are more frequent in tissues from COPD patients compared to those of control subjects. Increased proximity and clusterization between CD8⁺ T cells and fibrocytes are associated with altered lung function. Tissular CD8⁺ T cells from COPD patients promote fibrocyte chemotaxis via the CXCL8-CXCR1/2 axis. Live imaging shows that CD8⁺ T cells establish short-term interactions with fibrocytes, that trigger CD8⁺ T cell proliferation in a CD54- and CD86-dependent manner, pro-inflammatory cytokines production, CD8⁺ T cell cytotoxic activity against bronchial epithelial cells and fibrocyte immunomodulatory properties. We defined a computational model describing these intercellular interactions and calibrated the parameters based on our experimental measurements. We show the model's ability to reproduce histological ex vivo characteristics, and observe an important contribution of fibrocyte-mediated CD8⁺ T cell proliferation in COPD development. Using the model to test therapeutic scenarios, we predict a recovery time of several years, and the failure of targeting chemotaxis or interacting processes. Altogether, our study reveals that local interactions between fibrocytes and CD8⁺ T cells could jeopardize the balance between protective immunity and chronic inflammation in the bronchi of COPD patients.

Probabilistic cellular automata modelling of intercellular interactions in airways: complex pattern formation in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a highly prevalent lung disease characterized by chronic inflammation and tissue remodeling possibly induced by unusual interactions between fibrocytes and CD8+ T lymphocytes in the peribronchial area. To investigate this phenomenon, we developed a probabilistic cellular automata type model where the two types of cells follow simple local interaction rules taking into account cell death, proliferation, migration and infiltration. We conducted a rigorous mathematical analysis using multiscale experimental data obtained in control and disease conditions to estimate the model's parameters accurately. The simulation of the model is straightforward to implement, and two distinct patterns emerged that we can analyse quantitatively. In particular, we show that the change in fibrocyte density in the COPD condition is mainly the consequence of their infiltration into the lung during exacerbations, suggesting possible explanations for experimental observations in normal and COPD tissue. Our integrated approach that combines a probabilistic cellular automata model and experimental findings will provide further insights into COPD in future studies.

Identification of fibrocyte cluster in tumors reveals the role in antitumor immunity by PD-L1 blockade

Recent clinical trials revealed that immune checkpoint inhibitors and antiangiogenic reagent combination therapy improved the prognosis of various cancers. We investigated the roles of fibrocytes, collagen-producing monocyte-derived cells, in combination immunotherapy. Anti-VEGF (vascular endothelial growth factor) antibody increases tumor-infiltrating fibrocytes and enhances the antitumor effects of anti-PD-L1 (programmed death ligand 1) antibody in vivo. Single-cell RNA sequencing of tumor-infiltrating CD45⁺ cells identifies a distinct "fibrocyte cluster" from "macrophage clusters" in vivo and in lung adenocarcinoma patients. A sub-clustering analysis reveals a fibrocyte sub-cluster that highly expresses co-stimulatory molecules. CD8⁺ T cell-costimulatory activity of tumor-infiltrating CD45⁺CD34⁺ fibrocytes is enhanced by anti-PD-L1 antibody. Peritumoral implantation of fibrocytes enhances the antitumor effect of PD-L1 blockade in vivo; CD86^-/- fibrocytes do not. Tumor-infiltrating fibrocytes acquire myofibroblast-like phenotypes through transforming growth factor β (TGF-β)/small mothers against decapentaplegic (SMAD) signaling. Thus, TGF-βR/SMAD inhibitor enhances the antitumor effects of dual VEGF and PD-L1 blockade by regulating fibrocyte differentiation. Fibrocytes are highlighted as regulators of the response to programmed death 1 (PD-1)/PD-L1 blockade.

Fibrocytes boost tumor-supportive phenotypic switches in the lung cancer niche via the endothelin system

Fibrocytes are bone marrow-derived monocytic cells implicated in wound healing. Here, we identify their role in lung cancer progression/ metastasis. Selective manipulation of fibrocytes in mouse lung tumor models documents the central role of fibrocytes in boosting niche features and enhancing metastasis. Importantly, lung cancer patients show increased number of circulating fibrocytes and marked fibrocyte accumulation in the cancer niche. Using double and triple co-culture systems with human lung cancer cells, fibrocytes, macrophages and endothelial cells, we substantiate the central features of cancer-supporting niche: enhanced cancer cell proliferation and migration, macrophage activation, augmented endothelial cell sprouting and fibrocyte maturation. Upregulation of endothelin and its receptors are noted, and dual endothelin receptor blockade suppresses all cancer-supportive phenotypic alterations via acting on fibrocyte interaction with the cancer niche. We thus provide evidence for a crucial role of fibrocytes in lung cancer progression and metastasis, suggesting targets for treatment strategies.

Muscarinic receptor M3 activation promotes fibrocytes contraction

Fibrocytes are monocyte-derived cells able to differentiate into myofibroblasts-like cells. We have previously shown that they are increased in the bronchi of Chronic Obstructive Pulmonary Disease (COPD) patients and associated to worse lung function. COPD is characterized by irreversible airflow obstruction, partly due to an increased cholinergic environment. Our goal was to investigate muscarinic signalling in COPD fibrocytes. Fibrocytes were isolated from 16 patients with COPD's blood and presence of muscarinic M3 receptor was assessed at the transcriptional and protein levels. Calcium signalling and collagen gels contraction experiments were performed in presence of carbachol (cholinergic agonist) ± tiotropium bromide (antimuscarinic). Expression of M3 receptor was confirmed by Western blot and flow cytometry in differentiated fibrocytes. Immunocytochemistry showed the presence of cytoplasmic and membrane-associated pools of M3. Stimulation with carbachol elicited an intracellular calcium response in 35.7% of fibrocytes. This response was significantly blunted by the presence of tiotropium bromide: 14.6% of responding cells (p < 0.0001). Carbachol induced a significant contraction of fibrocytes embedded in collagen gels (13.6 ± 0.3% versus 2.5 ± 4.1%; p < 0.0001), which was prevented by prior tiotropium bromide addition (4.1 ± 2.7% of gel contraction; p < 0.0001). Finally, M3-expressing fibrocytes were also identified in situ in the peri-bronchial area of COPD patients' lungs, and there was a tendency to an increased density compared to healthy patient's lungs. In conclusion, around 1/3 of COPD patients' fibrocytes express a functional muscarinic M3 receptor. Cholinergic-induced fibrocyte contraction might participate in airway diameter reduction and subsequent increase of airflow resistance in patients with COPD. The inhibition of these processes could participate to the beneficial effects of muscarinic antagonists for COPD treatment.

Interrelation Between Fibroblasts and T Cells in Fibrosing Interstitial Lung Diseases

Interstitial lung diseases (ILDs) are a heterogeneous group of diseases characterized by varying degrees of inflammation and fibrosis of the pulmonary interstitium. The interrelations between multiple immune cells and stromal cells participate in the pathogenesis of ILDs. While fibroblasts contribute to the development of ILDs through secreting extracellular matrix and proinflammatory cytokines upon activation, T cells are major mediators of adaptive immunity, as well as inflammation and autoimmune tissue destruction in the lung of ILDs patients. Fibroblasts play important roles in modulating T cell recruitment, differentiation and function and conversely, T cells can balance fibrotic sequelae with protective immunity in the lung. A more precise understanding of the interrelation between fibroblasts and T cells will enable a better future therapeutic design by targeting this interrelationship. Here we highlight recent work on the interactions between fibroblasts and T cells in ILDs, and consider the implications of these interactions in the future development of therapies for ILDs.

Circulating tumor cells counts are associated with CD8+ T cell levels in programmed death-ligand 1-negative non-small cell lung cancer patients after radiotherapy: A retrospective study

This study aimed to explore the dynamics of circulating tumor cells (CTCs) and CD8+ T cells in stage II-III non-small cell lung cancer patients with CTCs in different programmed death-ligand 1 (PD-L1) status treated with radiotherapy and evaluate the correlation between CTCs and CD8+ T cells.This study was a retrospective study which reviewed 69 stage II-III non-small cell lung cancer patients underwent postoperative radiotherapy and peripheral blood tests of CTCs and T lymphocyte were available before radiation, 1 week after radiation and 1 month after radiation.In this study, 25 patients had PD-L1 positive CTCs and 44 patients had PD-L1 negative CTCs. The CTCs count was significantly decreased compared with baseline in patients with different PD-L1 status CTCs at 1 week and 1 month after radiotherapy. The proportion of CD8+ T cells was significantly increased at 1 month after radiotherapy compared with baseline in the total population (mean change, 7.24 ± 2.12; P < .05) and patients with PD-L1 negative CTCs (mean change, 7.17 ± 2.65; P < .05). One month after radiotherapy, the proportion of CD8+ T cells was negatively correlated with the CTCs count in the total population (r = -0.255, P = .034) and PD-L1 negative patients (r = -0.330, P = .029). In patients with PD-L1 negative CTCs, the CTCs count 1 week after radiotherapy (hazard ratio, 0.150 [95% confidence intervals., 0.027-0.840], P = .031) and the proportion of CD8+ T cells 1 month after radiotherapy (hazard ratio, 7.961 [95% confidence intervals, 1.028-61.68], P = .047) were independent prognostic factors for disease recurrence.After radiotherapy, only PD-L1-negative patients had a significant increase in the CD8+ T cell levels, while it was negatively correlated with CTCs count and was an independent prognostic factors of disease recurrence.