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.
OBJECTIVE: 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.

BACKGROUND: Proptosis in Thyroid Eye Disease (TED) can result in facial disfigurement and visual dysfunction. Treatment with Insulin-like growth factor I receptor (IGF-IR) inhibitors has been shown to be effective in reducing proptosis but with side effects.
OBJECTIVE: To test the hypothesis that inhibition of IGF-IR indirectly and more selectively with PAPP-A inhibitors attenuates IGF-IR signaling in TED.
METHODS: Informed consent was obtained from TED patients undergoing surgery, and retro-orbital tissue collected for fibroblast isolation and culture.
METHODS: Surgeries were performed in Mayo Clinic operating suites. Cell culture was performed in a sterile tissue culture facility.
METHODS: Retro-orbital tissue was collected from 19 TED patients.
METHODS: Treatment of TED fibroblasts with pro-inflammatory cytokines. Flow separation of CD34- and CD34+ orbital fibroblasts, the latter representing infiltrating fibrocytes into the orbit in TED.
METHODS: PAPP-A expression and proteolytic activity, IGF-I stimulation of phosphatidylinositol 3 kinase/Akt pathway and inhibition by immuno-neutralizing antibodies against PAPP-A, CD34+ status and associated PAPP-A and IGF-IR expression.
RESULTS: Pro-inflammatory cytokines markedly increased PAPP-A expression in TED fibroblasts. IGF-IR expression was not affected by cytokine treatment. Inhibition of PAPP-A\'s proteolytic activity suppressed IGF-IR activation in orbital fibroblasts from TED patients. TED fibroblasts that were CD34+ represented ∼80% of the cells in culture and accounted for ∼70% of PAPP-A and IGF-IR expressing cells.
CONCLUSIONS: These results support a role for PAPP-A in TED pathogenesis and indicate the potential for novel therapeutic targeting of the IGF axis.

BACKGROUND: Obesity is a risk factor for breast cancer, and women with obesity that develop breast cancer have a worsened prognosis. Within the mammary gland, obesity causes chronic, macrophage-driven inflammation and adipose tissue fibrosis. Weight loss is a recommended intervention to resolve obesity, but the impact of weight loss on the mammary gland microenvironment and in tumors has not been well identified.
METHODS: To examine the effects of weight loss following obesity, mice were fed a high-fat diet for 16 weeks to induce obesity, then switched to a low-fat diet for 6 weeks. We examined changes in immune cells, including fibrocytes, which are myeloid lineage cells that have attributes of both macrophages and myofibroblasts, and collagen deposition within the mammary glands of non-tumor-bearing mice and within the tumors of mice that were transplanted with estrogen receptor alpha positive TC2 tumor cells.
RESULTS: In formerly obese mice, we observed reduced numbers of crown-like structures and fibrocytes in mammary glands, while collagen deposition was not resolved with weight loss. Following transplant of TC2 tumor cells into the mammary glands of lean, obese, and formerly obese mice, diminished collagen deposition and cancer-associated fibroblasts were observed in tumors from formerly obese mice compared to obese mice. Within tumors of obese mice, increased myeloid-derived suppressor cells and diminished CD8+ T cells were identified, while the microenvironment of tumors of formerly obese mice were more similar to tumors from lean mice. When TC2 tumor cells were mixed with CD11b+CD34+ myeloid progenitor cells, which are the cells of origin for fibrocytes, and transplanted into mammary glands of lean and obese mice, collagen deposition within the tumors of both lean and obese was significantly greater than when tumor cells were mixed with CD11b+CD34- monocytes or total CD45+ immune cells.
CONCLUSIONS: Overall, these studies demonstrate that weight loss resolved some of the microenvironmental conditions within the mammary gland that may contribute to tumor progression. Additionally, fibrocytes may contribute to early collagen deposition in mammary tumors of obese mice leading to the growth of desmoplastic tumors.

BACKGROUND: Previous studies have shown that IL-25 levels are increased in patients with asthma with fixed airflow limitation (FAL). However, the mechanism by which IL-25 contributes to airway remodeling and FAL remains unclear. Here, we hypothesized that IL-25 facilitates pro-fibrotic phenotypic changes in bronchial epithelial cells (BECs) and circulating fibrocytes (CFs), orchestrates pathological crosstalk from BECs to CFs, and thereby contributes to airway remodeling and FAL.
METHODS: Fibrocytes from asthmatic patients with FAL and chronic asthma murine models were detected using flow cytometry, multiplex staining and multispectral imaging analysis. The effect of IL-25 on BECs and CFs and on the crosstalk between BECs and CFs was determined using cell culture and co-culture systems.
RESULTS: We found that asthmatic patients with FAL had higher numbers of IL-25 receptor (i.e., IL-17RB)+-CFs, which were negatively correlated with forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC). The number of airway IL-17RB+-fibrocytes was significantly increased in ovalbumin (OVA)- and IL-25-induced asthmatic mice versus the control subjects. BECs stimulated with IL-25 exhibited an epithelial-mesenchymal transition (EMT)-like phenotypic changes. CFs stimulated with IL-25 produced high levels of extracellular matrix (ECM) proteins and connective tissue growth factors (CTGF). These profibrotic effects of IL-25 were partially blocked by the PI3K-AKT inhibitor LY294002. In the cell co-culture system, OVA-challenged BECs facilitated the migration and expression of ECM proteins and CTGF in CFs, which were markedly blocked using an anti-IL-17RB antibody.
CONCLUSIONS: These results suggest that IL-25 may serve as a potential therapeutic target for asthmatic patients with FAL.

Obesity is a risk factor for breast cancer, and women with obesity that develop breast cancer have a worsened prognosis. Within the mammary gland, obesity causes chronic, macrophage-driven inflammation and adipose tissue fibrosis. To examine the impact of weight loss on the mammary microenvironment, mice were fed high-fat diet to induce obesity, then switched to a low-fat diet. In formerly obese mice, we observed reduced numbers of crown-like structures and fibrocytes in mammary glands, while collagen deposition was not resolved with weight loss. Following transplant of TC2 tumor cells into the mammary glands of lean, obese, and formerly obese mice, diminished collagen deposition and cancer-associated fibroblasts were observed in tumors from formerly obese mice compared to obese mice. When TC2 tumor cells were mixed with CD11b+CD34+ myeloid progenitor cells, collagen deposition within the tumors was significantly greater compared to when tumor cells were mixed with CD11b+CD34- monocytes, suggesting that fibrocytes contribute to early collagen deposition in mammary tumors of obese mice. Overall, these studies show that weight loss resolved some of the microenvironmental conditions within the mammary gland that may contribute to tumor progression.

Obesity rates continue to rise, and obese individuals are at higher risk for multiple types of cancer, including breast cancer. Obese mammary fat is a site of chronic, macrophage-driven inflammation, which enhances fibrosis within adipose tissue. Elevated fibrosis within the mammary gland may contribute to risk for obesity-associated breast cancer. To understand how inflammation due to obesity enhanced fibrosis within mammary tissue, we utilized a high-fat diet model of obesity and elimination of CCR2 signaling in mice to identify changes in immune cell populations and their impact on fibrosis. We observed that obesity increased a population of CD11b+ cells with the ability to form myofibroblast-like colonies in vitro. This population of CD11b+ cells is consistent with fibrocytes, which have been identified in wound healing and chronic inflammatory diseases but have not been examined in obesity. In CCR2-null mice, which have limited ability to recruit myeloid lineage cells into obese adipose tissue, we observed reduced mammary fibrosis and diminished fibrocyte colony formation in vitro. Transplantation of myeloid progenitor cells, which are the cells of origin for fibrocytes, into the mammary glands of obese CCR2-null mice resulted in significantly increased myofibroblast formation. Gene expression analyses of the myeloid progenitor cell population from obese mice demonstrated enrichment for genes associated with collagen biosynthesis and extracellular matrix remodeling. Together these results show that obesity enhances recruitment of fibrocytes to promote obesity-induced fibrosis in the mammary gland.

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.

Skeletal muscle wasting, whether related to physiological ageing, muscle disuse or to an underlying chronic disease, is a key determinant to quality of life and mortality. However, cellular basis responsible for increased catabolism in myocytes often remains unclear. Although myocytes represent the vast majority of skeletal muscle cellular population, they are surrounded by numerous cells with various functions. Animal models, mostly rodents, can help to decipher the mechanisms behind this highly dynamic process, by allowing access to every muscle as well as time-course studies. Satellite cells (SCs) play a crucial role in muscle regeneration, within a niche also composed of fibroblasts and vascular and immune cells. Their proliferation and differentiation is altered in several models of muscle wasting such as cancer, chronic kidney disease or chronic obstructive pulmonary disease (COPD). Fibro-adipogenic progenitor cells are also responsible for functional muscle growth and repair and are associated in disease to muscle fibrosis such as in chronic kidney disease. Other cells have recently proven to have direct myogenic potential, such as pericytes. Outside their role in angiogenesis, endothelial cells and pericytes also participate to healthy muscle homoeostasis by promoting SC pool maintenance (so-called myogenesis-angiogenesis coupling). Their role in chronic diseases muscle wasting has been less studied. Immune cells are pivotal for muscle repair after injury: Macrophages undergo a transition from the M1 to the M2 state along with the transition between the inflammatory and resolutive phase of muscle repair. T regulatory lymphocytes promote and regulate this transition and are also able to activate SC proliferation and differentiation. Neural cells such as terminal Schwann cells, motor neurons and kranocytes are notably implicated in age-related sarcopenia. Last, newly identified cells in skeletal muscle, such as telocytes or interstitial tenocytes could play a role in tissular homoeostasis. We also put a special focus on cellular alterations occurring in COPD, a chronic and highly prevalent respiratory disease mainly linked to tobacco smoke exposure, where muscle wasting is strongly associated with increased mortality, and discuss the pros and cons of animal models versus human studies in this context. Finally, we discuss resident cells metabolism and present future promising leads for research, including the use of muscle organoids.

Mesenchymal cells (keratocytes, corneal fibroblasts, and myofibroblasts), as well as mesenchymal progenitor bone marrow-derived fibrocytes, are the major cellular contributors to stromal fibrosis after injury to the cornea. Corneal fibroblasts, in addition to being major progenitors to myofibroblasts, also have anti-fibrotic functions in (1) the production of non-basement membrane collagen type IV that binds activated transforming growth factor (TGF) beta-1 and TGF beta-2 to downregulate TGF beta effects on cells in the injured stroma, (2) the production of chemokines that modulate the entry of bone marrow-derived cells into the stroma, (3) the production of hepatocyte growth factor and keratinocyte growth factor to regulate corneal epithelial healing, (4) the cooperation with the epithelium or corneal endothelium in the regeneration of the epithelial basement membrane and Descemet\'s membrane, and other functions. Fibrocytes also serve as major progenitors to myofibroblasts in the corneal stroma. Thus, mesenchymal cells and mesenchymal cell progenitors serve Yin and Yang functions to inhibit and promote tissue fibrosis depending on the overall regulatory milieu within the injured stroma.

UNASSIGNED: The circulating progenitor cells of fibroblasts (fibrocytes) have been shown to infiltrate the airway smooth muscle compartment of asthma patients; however, the pathological significance of this discovery has yet to be elucidated. This study established a co-culture model of airway smooth muscle cells (ASMCs) and fibrocytes from asthmatic or normal subjects to evaluate innate cytokine production, corticosteroid responses, and signaling in ASMCs.
UNASSIGNED: CD34+ fibrocytes were purified from peripheral blood of asthmatic (Global Initiative for Asthma treatment step 4-5) and normal subjects and cultured for 5∼7 days. In a transwell plate, ASMCs were co-cultured with fibrocytes at a ratio of 2:1, ASMCs were cultured alone (control condition), and fibrocytes were cultured alone for 48 h. Measurements were obtained of interleukin-8 (IL-8), IL-6, IL-17, thymic stromal lymphopoietin, and IL-33 levels in the supernatant and IL-33 levels in the cell lysate of the co-culture. Screening for intracellular signaling in the ASMCs after stimulation was performed using condition medium from the patients\' co-culture (PtCM) or IL-8. mRNA and western blot analysis were used to analyze AKT/mTOR signaling in ASMCs stimulated via treatment with PtCM or IL-8.
UNASSIGNED: Compared with ASMCs cultured alone, IL-8 levels in the supernatant and IL-33 levels in the ASMCs lysate were significantly higher in samples co-cultured from asthmatics, but not in those co-cultured from normal subjects. Corticosteroid-induced suppression of IL-8 production was less pronounced in ASMCs co-cultured with fibrocytes from asthma patients than in ASMCs co-cultured from normal subjects. ASMCs stimulated using PtCM and IL-8 presented elevating activated AKT substrate PRAS40. Treatment with IL-8 and PtCM increased mRNA expression of mTOR and P70S6 kinases in ASMCs. Treatment with IL-8 and PtCM also significantly increased phosphorylation of AKT and mTOR subtract S6 ribosomal protein in ASMCs.
UNASSIGNED: The interaction between ASMCs and fibrocytes from asthmatic patients was shown to increase IL-8 and IL-33 production and promote AKT/mTOR signaling in ASMCs. IL-8 production in the co-culture from asthmatic patients was less affected by corticosteroid than was that in the co-culture from normal subjects. Our results elucidate the novel role of fibrocytes and ASMCs in the pathogenesis of asthma.