Effects of Active Chronic Cigarette-Smoke Exposure on Circulating Fibrocytes.

PURPOSE: This study aimed to evaluate the hypothesis that active smoking impacts upon mediators and abundance of circulating fibrocyte cells in smoking-related disease characterised by fibrosis. METHODS: Flow cytometry and enzyme-linked immunosorbent assays were used to investigate blood from five patient groups: healthy never-smokers, healthy current smokers, stable chronic obstructive pulmonary disease (COPD) active smokers, idiopathic pulmonary fibrosis (IPF) never-smokers, and IPF active smokers. RESULTS: A significant inverse dose-response relationship was observed in healthy smokers among cumulative smoking burden (pack-years) and fibrocyte abundance (p = 0.006, r = -0.86). Among serum profibrotic fibrocyte chemokines measured, CCL18 rose significantly alongside fibrocyte numbers in all five subject groups, while having an inverse dose-response relationship with pack-year burden in healthy smokers (p = 0.003, r = -0.89). In IPF, CCL2 rose in direct proportion to fibrocyte abundance irrespective of smoking status but had lower serum levels in those currently smoking (p = < 0.001). For the study population, CXCL12 was decreased in pooled current smokers versus never-smokers (p = 0.03). CONCLUSION: The suppressive effect of current, as distinct from former, chronic smoking on circulating fibrocyte abundance in healthy smokers, and modulation of regulatory chemokine levels by active smoking may have implications for future studies of fibrocytes in smoking-related lung diseases as a potential confounding variable.

Therapeutic IGF-I receptor inhibition alters fibrocyte immune phenotype in thyroid-associated ophthalmopathy.

Thyroid-associated ophthalmopathy (TAO) represents a disfiguring and potentially blinding autoimmune component of Graves' disease. It appears to be driven, at least in part, by autoantibodies targeting the thyrotropin receptor (TSHR)/insulin-like growth factor I receptor (IGF-IR) complex. Actions mediated through either TSHR or IGF-IR are dependent on IGF-IR activity. CD34+ fibrocytes, monocyte lineage cells, reside uniquely in the TAO orbit, where they masquerade as CD34+ orbital fibroblasts. Fibrocytes present antigens to T cells through their display of the major histocompatibility complex class II (MHC II) while providing costimulation through B7 proteins (CD80, CD86, and programmed death-ligand 1 [PD-L1]). Here, we demonstrate that teprotumumab, an anti-IGF-IR inhibitor, attenuates constitutive expression and induction by the thyroid-stimulating hormone of MHC II and these B7 members in CD34+ fibrocytes. These actions are mediated through reduction of respective gene transcriptional activity. Other IGF-IR inhibitors (1H7 and linsitinib) and knocking down IGF-IR gene expression had similar effects. Interrogation of circulating fibrocytes collected from patients with TAO, prior to and following teprotumumab treatment in vivo during a phase 2 clinical trial, demonstrated reductions in cell-surface MHC II and B7 proteins similar to those found following IGF-IR inhibitor treatment in vitro. Teprotumumab therapy reduces levels of interferon-γ and IL-17A expression in circulating CD4+ T cells, effects that may be indirect and mediated through actions of the drug on fibrocytes. Teprotumumab was approved by the US Food and Drug Administration for TAO. Our current findings identify potential mechanisms through which teprotumumab might be eliciting its clinical response systemically in patients with TAO, potentially by restoring immune tolerance.

Fibrocyte Phenotype of ENTPD1+CD55+ Cells and Its Association with Pain in Osteoarthritic Synovium.

Osteoarthritis (OA) is a prevalent degenerative joint disorder characterized by cartilage erosion, structural changes, and inflammation. Synovial fibroblasts play a crucial role in OA pathophysiology, with abnormal fibroblastic cells contributing significantly to joint pathology. Fibrocytes, expressing markers of both hematopoietic and stromal cells, are implicated in inflammation and fibrosis, yet their marker and role in OA remain unclear. ENTPD1, an ectonucleotidase involved in purinergic signaling and expressed in specific fibroblasts in fibrotic conditions, led us to speculate that ENTPD1 plays a role in OA pathology by being expressed in fibrocytes. This study aimed to investigate the phenotype of ENTPD1+CD55+ and ENTPD1-CD55+ synovial fibroblasts in OA patients. Proteomic analysis revealed a distinct molecular profile in ENTPD1+CD55+ cells, including the upregulation of fibrocyte markers and extracellular matrix-related proteins. Pathway analysis suggested shared mechanisms between OA and rheumatoid arthritis. Correlation analysis revealed an association between ENTPD1+CD55+ fibrocytes and resting pain in OA. These findings highlight the potential involvement of ENTPD1 in OA pain and suggest avenues for targeted therapeutic strategies. Further research is needed to elucidate the underlying molecular mechanisms and validate potential therapeutic targets.

Circulating and renal fibrocytes are associated with interstitial fibrosis in lupus nephritis.

OBJECTIVES: Fibrocytes, the extracellular matrix-producing cells derived from bone marrow progenitors, contribute to organ fibrosis. We investigated the presence and characteristics of fibrocytes in the peripheral blood and kidney of patients with lupus nephritis (LN), and the association of the abundance of fibrocytes with renal tubular epithelial cells (RTECs) in LN fibrogenesis. METHODS: Fibrocytes were identified with type I collagen (colI), α-smooth muscle actin (α-SMA), CD34 and CD45 using flow cytometry and confocal imaging. The associations between the levels of fibrocytes and pathological features of patients with LN were analysed. The contribution of RTECs to fibrocyte generation was determined using LN sera-treated HK-2 cells. RESULTS: Spindle-shaped fibrocytes (colI+α-SMA+CD34+CD45+ cells) were present in the peripheral blood and their abundance was especially high in LN patients with interstitial fibrosis compared with healthy control. Renal fibrocytes (colI+α-SMA+CD45+ cells) were found in the tubulointerstitium in patients with LN, and their numbers were significantly associated with the degrees of chronicity indices including interstitial fibrosis and renal dysfunction. Stimulation of peripheral blood mononuclear cells with supernatants from LN serum-treated HK-2 cells led to a significant generation of fibrocytes, which was abrogated by the addition of IL-6 neutralizing antibody. CONCLUSION: Fibrocytes were significantly increased in the blood and kidney tissue of patients with LN, especially those with interstitial fibrosis. Fibrocytes could be differentiated from blood cells, with an active contribution from RTECs. Our results show a possible link between fibrocytes and tubulointerstitial fibrosis, which may serve as a novel therapeutic target for LN fibrogenesis.

Health prevention intervention for chronic tissue fibrosis: Based on the specific expression of CCL19/21 + mast cell.

Chronic tissue fibrosis is a common pathological feature of connective tissue diseases and malignant tumors, and its prevention has been a major focus of relevant research.However, the details of the mechanism of action of tissue-colonizing immune cells in fibroblast migration are unclear. In this study, connective tissue disease tissue specimens and solid tumor specimens were selected to observe the relationship between mast cells and interstitial fibrosis and the expression characteristics of mast cells. Our findings suggest that the number of mast cells in the tissue correlates with the degree of pathological fibrosis and that mast cells specifically express the chemokines CCL19 and CCL21, especially CCL19. CCR7+ fibroblasts are highly expressed in mast cell clusters. The mast cell line HMC-1 regulates CD14+ monocyte-derived fibroblasts via CCL19. In disease tissue fibrosis, mast cell activation may increase the expression of chemokines, especially CCL19, in the tissue, thereby inducing a large number of CCR7-positive fibroblasts to migrate to specific tissues. This study lays a foundation for the mechanism of tissue fibrosis and provides evidence for the mechanism by which mast cells induce fibroblast migration.Through the experimental results of this paper, we can combine the induction factors of chronic tissue fibrosis and put forward targeted health prevention strategies.

Fibrocyte: A missing piece in the pathogenesis of fibrous epulis.

OBJECTIVES: To explore the role of fibrocytes in the recurrence and calcification of fibrous epulides. METHODS: Different subtypes of fibrous epulides and normal gingival tissue specimens were first collected for histological and immunofluorescence analyses to see if fibrocytes were present and whether they differentiated into myofibroblasts and osteoblasts upon stimulated by transforming growth factor-ß1 (TGF-ß1). Electron microscopy and elemental analysis were used to characterize the extracellular microenvironment in different subtypes of fibrous epulides. Human peripheral blood mononuclear cells (PBMCs) were subsequently isolated from in vitro models to mimic the microenvironment in fibrous epulides to identify whether TGF-ß1 as well as the calcium and phosphorus ion concentration in the extracellular matrix (ECM) of a fibrous epulis trigger fibrocyte differentiation. RESULTS: Fibrous epulides contain fibrocytes that accumulate in the local inflammatory environment and have the ability to differentiate into myofibroblasts or osteoblasts. TGF-ß1 promotes fibrocytes differentiation into myofibroblasts in a concentration-dependent manner, while TGF-ß1 stimulates the fibrocytes to differentiate into osteoblasts when combined with a high calcium and phosphorus environment. CONCLUSIONS: Our study revealed fibrocytes play an important role in the fibrogenesis and osteogenesis in fibrous epulis, and might serve as a therapeutic target for the inhibition of recurrence of fibrous epulides.

2021 update on thyroid-associated ophthalmopathy.

PURPOSE: Our understanding of thyroid-associated ophthalmopathy (TAO, A.K.A Graves' orbitopathy, thyroid eye disease) has advanced substantially, since one of us (TJS) wrote the 2010 update on TAO, appearing in this journal. METHODS: PubMed was searched for relevant articles. RESULTS: Recent insights have resulted from important studies conducted by many different laboratory groups around the World. A clearer understanding of autoimmune diseases in general and TAO specifically emerged from the use of improved research methodologies. Several key concepts have matured over the past decade. Among them, those arising from the refinement of mouse models of TAO, early stage investigation into restoring immune tolerance in Graves' disease, and a hard-won acknowledgement that the insulin-like growth factor-I receptor (IGF-IR) might play a critical role in the development of TAO, stand out as important. The therapeutic inhibition of IGF-IR has blossomed into an effective and safe medical treatment. Teprotumumab, a ß-arrestin biased agonist monoclonal antibody inhibitor of IGF-IR has been studied in two multicenter, double-masked, placebo-controlled clinical trials demonstrated both effectiveness and a promising safety profile in moderate-to-severe, active TAO. Those studies led to the approval by the US FDA of teprotumumab, currently marketed as Tepezza for TAO. We have also learned far more about the putative role that CD34+ fibrocytes and their derivatives, CD34+ orbital fibroblasts, play in TAO. CONCLUSION: The past decade has been filled with substantial scientific advances that should provide the necessary springboard for continually accelerating discovery over the next 10 years and beyond.

Circulating fibrocyte level in children with cystic fibrosis.

BACKGROUND: This study aimed to evaluate circulating fibrocyte levels in cystic fibrosis (CF) patients during stable and exacerbation periods of the condition. METHODS: The study group consisted of 39 patients diagnosed with CF and 20 healthy controls. Individuals included in the study were divided into three groups: CF, CF exacerbated, and a healthy control group. Their circulating fibrocyte levels were compared. Findings from a pulmonary function test and high-resolution computed tomography of the lung were evaluated and compared. RESULTS: The circulating fibrocyte count was found to be significantly higher in patients with CF compared with the exacerbated and control groups. No correlation was found between the forced expiratory volume in 1 s and forced vital capacity values in the pulmonary function test and the circulating fibrocyte count. The circulating fibrocyte count in patients (in the CF group) with positive findings in the high-resolution computed tomography was statistically significantly lower. CONCLUSIONS: The circulating fibrocyte level in the peripheral blood of the patients with CF was increased.

Blood fibrocytes are associated with severity and prognosis in COVID-19 pneumonia.

Increased blood fibrocytes are associated with a poor prognosis in fibrotic lung diseases. We aimed to determine whether the percentage of circulating fibrocytes could be predictive of severity and prognosis during coronavirus disease 2019 (COVID-19) pneumonia. Blood fibrocytes were quantified by flow cytometry as CD45+/CD15-/CD34+/collagen-1+ cells in patients hospitalized for COVID-19 pneumonia. In a subgroup of patients admitted in an intensive care unit (ICU), fibrocytes were quantified in blood and bronchoalveolar lavage (BAL). Serum amyloid P (SAP), transforming growth factor-ß1 (TGF-ß1), CXCL12, CCL2, and FGF2 concentrations were measured. We included 57 patients in the hospitalized group (median age = 59 yr [23-87]) and 16 individuals as healthy controls. The median percentage of circulating fibrocytes was higher in the patients compared with the controls (3.6% [0.2-9.2] vs. 2.1% [0.9-5.1], P = 0.04). Blood fibrocyte count was lower in the six patients who died compared with the survivors (1.6% [0.2-4.4] vs. 3.7% [0.6-9.2], P = 0.02). Initial fibrocyte count was higher in patients showing a complete lung computed tomography (CT) resolution at 3 mo. Circulating fibrocyte count was decreased in the ICU group (0.8% [0.1-2.0]), whereas BAL fibrocyte count was 6.7% (2.2-15.4). Serum SAP and TGF-ß1 concentrations were increased in hospitalized patients. SAP was also increased in ICU patients. CXCL12 and CCL2 were increased in ICU patients and negatively correlated with circulating fibrocyte count. We conclude that circulating fibrocytes were increased in patients hospitalized for COVID-19 pneumonia, and a lower fibrocyte count was associated with an increased risk of death and a slower resolution of lung CT opacities.

Anti-IgE therapy inhibits chemotaxis, proliferation and transformation of circulating fibrocytes in patients with severe allergic asthma.

BACKGROUND AND OBJECTIVE: Circulating fibrocytes act as precursors of myofibroblasts, contribute to airway remodelling in chronic asthma and migrate to injured tissues by expressing CXCR4 and CCR7. Anti-IgE therapy improves severe allergic asthma (SAA) control and airway remodelling in T2-high SAA. The effects of anti-IgE therapy on fibrocyte activities were investigated in this study. METHODS: The expression of CCR7, CXCR4, ST2 and α-SMA (α-smooth muscle actin) in both circulating and cultured fibrocytes from all patients with asthma was measured, and was repeated after omalizumab treatment in SAA. Fibrocytes recruitment, proliferation and transformation were also measured in response to anti-IgE therapy. RESULTS: Omalizumab effectively improved asthma control and pulmonary function in T2-high SAA, associated with a decline in serum levels of IL-33 and IL-13. Omalizumab down-regulates CXCR4 and CCR7 expression of fibrocytes, which could suppress fibrocyte recruitment into the lungs. Omalizumab also suppressed the increased number of fibrocytes and α-SMA+ fibrocytes within the cultured non-adherent non-T (NANT) cells after 3-7 days of culture. The decrease in serum levels of IL-33 by omalizumab contributed to the effectiveness in inhibiting fibrocyte recruitment, proliferation and myofibroblast transformation through IL-33/ST2 axis. The elevated IL-13 expression in SAA patients potentiated the effects of IL-33 by increasing ST2 expression. CONCLUSION: Omalizumab reduced the number of circulating fibrocytes, cell and number of fibrocytes as well as α-SMA+ fibrocytes after 3-7 days of culture in SAA patients. IL-33 and IL-13 may be implicated in the effectiveness of omalizumab in inhibiting fibrocyte activation contributing partly to the clinical benefits in reducing lamina propria and basement membrane thickening.

Fibrocytes in the Tumor Microenvironment.

Tumors have long been compared to chronic wounds that do not heal, since they share many of the same molecular and cellular processes. In normal wounds, healing processes lead to restoration of cellular architecture, while in malignant tumors, these healing processes become dysregulated and contribute to growth and invasion of neoplastic cells into the surrounding tissues. Fibrocytes are fibroblast-like cells that differentiate from bone marrow-derived CD14+ circulating monocytes and aid wound healing. Although most monocytes will differentiate into macrophages after extravasating into a tissue, signals present in a wound environment can cause some monocytes to differentiate into fibrocytes. The fibrocytes secrete matrix proteins and inflammatory cytokines, activate local fibroblasts to proliferate and increase extracellular matrix production, and promote angiogenesis, and because fibrocytes are contractile, they also help wound contraction. There is now emerging evidence that fibrocytes are present in the tumor microenvironment, attracted by the chronic tissue damage and cytokines from both cancer cells and other immune cells. Fibrocytes may aid in the survival and spread of neoplastic cells, so these wound-healing cells may be a promising target for anticancer research in future studies.

Tamibarotene inhibit the accumulation of fibrocyte and alleviate renal fibrosis by IL-17A.

Renal fibrosis is a common pathological process in the progression of chronic kidney disease. Accumulating evidence suggests that interleukin-17A (IL-17A) and fibrocytes play crucial roles in the pathogenesis of fibrosis. However, the role of IL-17A in the regulation of renal fibrocytes in renal fibrosis has rarely been reported. Here, we report that the plasma IL-17A level is increased in immunoglobulin A nephropathy (IgAN) patients and is correlated with clinical parameters. Using a mouse model of unilateral ureteral obstruction (UUO), we found that both IL-17A expression and fibrocyte infiltration were increased in the kidneys of UUO mice. Besides, IL-17A enhanced fibrosis and fibrocyte-associated chemokine and activator expression in vitro. Furthermore, inhibition of IL-17A using Am80 (Tamibarotene) decreased fibrocytes and fibrocyte-associated chemokine and activator expression and significantly attenuated renal fibrosis in the UUO mice. Our findings suggest that Am80, which inhibits the accumulation of fibrocytes and alleviates renal fibrosis mediated by IL-17A, maybe a novel therapeutic drug for renal fibrosis.

[The role of fibrocytes in myelofibrosis and fibrocyte regulation as a novel treatment approach].

Recently, monocyte-derived fibroblast-like cells, called fibrocytes, garnered attention as involved in the novel pathogenesis of various fibrotic diseases. They also play a role in the induction of myelofibrosis (MF). Neoplastic fibrocytes are overrepresented in the bone marrow of patients with primary MF, and the suppression of fibrocyte differentiation by serum amyloid P has been shown to remarkably improve MF. Further, thrombopoietin (TPO) or a TPO receptor agonist directly induces fibrocyte differentiation, and fibrocyte elimination reversed the MF phenotype in a murine model. Human fibrocytes highly express signaling lymphocytic activation molecule-F7 (SLAMF7) compared with macrophages. Myeloproliferative neoplasm (MPN) patients harboring JAK2V617F with MF had a significantly elevated SLAMF7high monocyte percentage, which correlated positively with the JAK2V617F allele burden. Furthermore, the JAK2V617F allele burden and the tendency to differentiate into fibrocytes of SLAMF7high monocytes was significantly higher than that of JAK2V617Flow monocytes and could be a potential target of elotuzumab (Elo), an anti-SLAMF7 antibody used to treat multiple myeloma. Elo independently inhibited the differentiation of fibrocytes derived not only from healthy controls but also from MF patients in vitro. Elo also ameliorated MF and splenomegaly induced by romiplostim administration in humanized NOG mice. Thus, Elo could be a therapeutic agent for MPN patients harboring JAK2V617F with MF.

Clinicopathological study of role of CD34 expressions in the stroma of premalignant and malignant lesions of uterine cervix.

CD34 is a transmembrane glycoprotein that is thought to be involved in the modulation of cell adhesion and signal transduction. The connective tissue stroma of virtually all human organs contain large amounts of resident CD34+ fibrocytes, which are involved in multiple functions such as wound healing, secretion of cytokines and also participate in stromal remodeling. It has been seen in various studies that absence of CD34+ fibrocytes within the stroma is associated with invasive carcinomas. In our study, we also investigated the presence and distribution of CD34+ fibrocytes in cervical intraepithelial neoplasia, invasive cervical carcinoma and adjacent normal cervical stroma. It was seen that normal cervical stroma and the stroma adjacent to cervical intra epithelial lesions harbours a dense meshwork of CD34+ fibrocytes, whereas the stroma of invasive carcinoma was nearly devoid of this cell population. Early stromal invasion by squamous carcinoma was characterized by a focal loss of CD34+ fibrocytes. This can be used as a sensitive tool in detecting tiny foci of stromal invasion in early cancer.

Fibrocytes in Asthma and Chronic Obstructive Pulmonary Disease: Variations on the Same Theme.

Fibrocytes are circulating cells that have fibroblast properties. They are produced by the bone marrow stroma, and they move from the blood to injured organs using multiple chemokine pathways. They exhibit marked functional and phenotypic plasticity in response to the local tissue microenvironment to ensure a proinflammatory or a more resolving phenotype. They can adopt immune cell properties and modulate conventional immune cell functions. Although their exact function is not always clear, they have emerged as key effector cells in several fibrotic diseases such as keloid, scleroderma, and idiopathic pulmonary fibrosis. Recent evidence suggests that fibrocytes could contribute to bronchial obstructive diseases such as asthma and chronic obstructive pulmonary disease. This review summarizes the reported roles of fibrocytes and their pathways into the lung in the context of asthma and chronic obstructive pulmonary disease, provides an overview of the different roles played by fibrocytes, and discusses their possible contributions to these obstructive diseases.

Thymic stromal lymphopoietin contribution to the recruitment of circulating fibrocytes to the lung in a mouse model of chronic allergic asthma.

Objective: Fibrocyte localization to the airways and thymic stromal lymphopoietin (TSLP) overexpression in the lung are features of severe asthma. The aim of this study was to determine whether TSLP contributes to fibrocyte trafficking and airway remodeling in a mouse model of allergic asthma. Methods: We established a chronic asthma animal model by administering house dust mite (HDM) extracts intranasally for up to 5 consecutive weeks. Mouse anti-TSLP monoclonal antibody (mAb) was given intraperitoneally starting the 4th week. Fluorescence-labeled CD34/collagen I (Col I)-dual-positive fibrocytes were examined by confocal microscopy. The level of TGF-ß1 in the bronchoalveolar lavage (BAL) fluid was determined by ELISA. Results: We found significantly increased levels of TSLP and TGF-ß1 in the lung of the mice subjected to repeated allergen exposure, which was accompanied by increased number of fibrocytes in the sub-epithelial zone and the BAL fluid. However, blocking TSLP markedly decreased the production of TGF-ß1, reduced the number of fibrocytes and subsequently prevented alterations of both airway and vascular structures. Conclusions: Our data suggested that TSLP might function in airway remodeling by promoting circulating fibrocyte recruitment to the lung in the mice subjected to chronic allergen exposure. These results provide a better rationale for targeting the interaction between TSLP and fibrocytes as a therapeutic approach for chronic allergic asthma.

TNF-α-stimulated fibroblasts secrete lumican to promote fibrocyte differentiation.

In healing wounds and fibrotic lesions, fibroblasts and monocyte-derived fibroblast-like cells called fibrocytes help to form scar tissue. Although fibrocytes promote collagen production by fibroblasts, little is known about signaling from fibroblasts to fibrocytes. In this report, we show that fibroblasts stimulated with the fibrocyte-secreted inflammatory signal tumor necrosis factor-α secrete the small leucine-rich proteoglycan lumican, and that lumican, but not the related proteoglycan decorin, promotes human fibrocyte differentiation. Lumican competes with the serum fibrocyte differentiation inhibitor serum amyloid P, but dominates over the fibroblast-secreted fibrocyte inhibitor Slit2. Lumican acts directly on monocytes, and unlike other factors that affect fibrocyte differentiation, lumican has no detectable effect on macrophage differentiation or polarization. α2ß1, αMß2, and αXß2 integrins are needed for lumican-induced fibrocyte differentiation. In lung tissue from pulmonary fibrosis patients with relatively normal lung function, lumican is present at low levels throughout the tissue, whereas patients with advanced disease have pronounced lumican expression in the fibrotic lesions. These data may explain why fibrocytes are increased in fibrotic tissues, suggest that the levels of lumican in tissues may have a significant effect on the decision of monocytes to differentiate into fibrocytes, and indicate that modulating lumican signaling may be useful as a therapeutic for fibrosis.

Circulating fibrocyte mobilization in negative pressure wound therapy.

Non-healing diabetic wounds are difficult to treat. They also create heavy financial burdens for both patients and society. Negative pressure wound therapy (NPWT) has been adopted to treat intractable wounds and has proved to be effective. However, the mechanisms that underlie the effects of this treatment are not entirely understood. Circulating fibrocytes are unique haematopoietic-derived stem cells that have been reported to play a pivotal role in wound healing. Here, we have investigated the effect of NPWT on fibrocyte mobilization and the role of fibrocyte mobilization in the healing of diabetic wounds during NPWT. We show that the NPWT group exhibited 2.6-fold to 12.1-fold greater numbers of tail vein-injected PKH-26-labelled fibrocytes in the diabetic wound sites compared with the control group. We also demonstrate that the full-thickness skin wounds treated with NPWT exhibit significantly reduced mRNA and protein expression, blood vessel density and proliferating cells when exogenous fibrocyte mobilization is inhibited. We speculate that systemic mobilization of fibrocytes during NPWT may be a mechanism for healing intractable wounds in a diabetic rat model experiment and that enhancement of cell mobilization may represent a potential treatment idea for intractable wound healing across all fields of surgery.

Immunohistochemical detection of intrathrombotic fibrocytes and its application to thrombus age estimation in murine deep vein thrombosis model.

Deep vein thrombi are dissolved after fibrosis process along with an increase of thrombus age. Fibrocytes are circulating bone marrow-derived cells with mesenchymal features that potentially have a unique and critical function in fibrosis. In this study, a double-color immunofluorescence analysis was carried out by using anti-CD45 and anti-collagen type I antibodies to examine the time-dependent appearance of fibrocytes in the murine model of stasis-induced deep vein thrombosis. The thrombus ages were 1, 3, 5, 7, 10, 14, and 21 days. In a thrombus age of less than 5 days, CD45+ and collagen type I+ fibrocytes were never detected. The intrathrombotic fibrocytes were initially observed in thrombi aged 7 days, and their number increased with advances in thrombus age. In a quantitative morphometrical analysis, the average number of intrathrombotic fibrocytes was highest in 14-day-old thrombi, and all of the five samples aged 14 days had the fibrocyte number of more than 25, and in three out of them, the number of intrathrombotic fibrocytes was over 30. On the contrary, in all of thrombus samples with the postligation intervals of 10 and 21 days, the number of intrathrombotic fibrocytes was less than 25. These observations imply that thrombi containing fibrocytes are at least 7 days old and that a fibrocyte number exceeding 30 would indicate the thrombus age of approximately 14 days. Our observations indicate that the detection of fibrocytes could be useful for thrombus age determination.

Fibroblasts secrete Slit2 to inhibit fibrocyte differentiation and fibrosis.

Monocytes leave the blood and enter tissues. In healing wounds and fibrotic lesions, some of the monocytes differentiate into fibroblast-like cells called fibrocytes. In healthy tissues, even though monocytes enter the tissue, for unknown reasons, very few monocytes differentiate into fibrocytes. In this report, we show that fibroblasts from healthy human tissues secrete the neuronal guidance protein Slit2 and that Slit2 inhibits human fibrocyte differentiation. In mice, injections of Slit2 inhibit bleomycin-induced lung fibrosis. In lung tissue from pulmonary fibrosis patients with relatively normal lung function, Slit2 has a widespread distribution whereas, in patients with advanced disease, there is less Slit2 in the fibrotic lesions. These data may explain why fibrocytes are rarely observed in healthy tissues, may suggest that the relative levels of Slit2 present in healthy tissue and at sites of fibrosis may have a significant effect on the decision of monocytes to differentiate into fibrocytes, and may indicate that modulating Slit2 signaling may be useful as a therapeutic for fibrosis.