An immunologist's guide to CD31 function in T-cells

AI-driven histologic analysis of human Achilles tendinopathy provides a roadmap to unravel pathogenesis

OBJECTIVES

Achilles tendinopathy is a common source of pain and dysfunction, yet its pathogenesis remains poorly understood. Research on human tendons is hampered by lack of standardisation in tissue sample validation, making interpretation of results challenging. We sought to develop an automated and operator-independent approach to histologically score human tendons.

METHODS

We assembled a cohort of 15 tendinopathic and 10 normal control Achilles tendon samples. We stained longitudinal sections with haematoxylin and eosin and Alcian blue and developed a low temperature epitope-retrieval protocol for immunostaining of blood vessels. Histologic sections were scored by pathologists using the current gold standard Bonar score. Whole sections were then analysed with open-source software (QuPath). Histologic features were automatically quantified across the entire section and summarised in the BonAIr score. Tissue from the same patients was subsequently analysed by quantitative polymerase chain reaction and flow cytometry to validate elements of the BonAIr score.

RESULTS

We observed increased cell roundness, collagen disarrangement, ground substance, and vascularity in tendinopathy using both the Bonar and BonAIr scores. Increased cellularity was only detected by the BonAIr score. Cellular and transcriptomic analyses corroborated tendinopathic shifts in all elements of the BonAIr score and further identified elevated THY1/CD90 expression in tendinopathy. CD90+ cells were found to localise to areas of low collagen alignment. These results align with the concept of stromal cell dysregulation in tendinopathy.

CONCLUSIONS

Automated analysis of whole tendon sections refines conventional histopathologic scoring and predicts cellular and molecular changes found in tendinopathy. The BonAIr score should be further developed for standardised assessment of tendons samples across other anatomical locations and different research centres.

Unveiling the anti-neoplastic potential of Schistosoma mansoni-derived antigen against breast cancer: a pre-clinical study

BACKGROUND

Cancer is a global health concern, with millions of new cases and deaths annually. Recently, immunotherapy has strengthened cancer treatment by harnessing the body's immune system to fight cancer. The search for advanced cancer immunotherapies has expanded to explore pathogens like parasites for their potential anti-neoplastic effects. While some parasites have shown promising results, the role of Schistosoma mansoni in breast cancer remains unexplored.

METHODS

This pre-clinical study investigated the anti-neoplastic potential of autoclaved Schistosoma mansoni antigen against breast cancer. In vitro, autoclaved Schistosoma mansoni antigen was evaluated on the MCF-7 human breast cancer cell line, while in vivo experiments used a chemically induced breast cancer rat model to evaluate tumour growth, liver enzyme levels, and immune response. Histopathological and immunohistochemical analyses assessed changes in tumour tissue, cell proliferation (Ki-67), angiogenesis (CD31), immune cell infiltration (CD8+ T cells), regulatory T cells (FoxP3+), and programmed death ligand 1 (PD-L1) expression.

RESULTS

In vitro, autoclaved Schistosoma mansoni antigen significantly reduced MCF-7 cell viability in a dose- and time-dependent manner. In vivo, autoclaved Schistosoma mansoni antigen treatment significantly reduced tumour weight and volume, improved liver enzyme levels, increased tumour necrosis, and decreased fibrosis. Immunohistochemical analysis revealed decreased Ki-67 and CD31 expression, indicating reduced cell proliferation and angiogenesis, respectively. Autoclaved Schistosoma mansoni antigen also enhanced immune responses by increasing CD8+ T cells infiltration and decreasing FoxP3+ expression, resulting in a higher CD8+ T cells/FoxP3+ ratio within the tumour microenvironment. Notably, PD-L1 expression was also downregulated, suggesting potential immune checkpoint inhibition.

CONCLUSIONS

Autoclaved Schistosoma mansoni antigen demonstrated potent anti-neoplastic activity, significantly reducing tumour growth and modulating the immune response within the tumour microenvironment. These results highlight autoclaved Schistosoma mansoni antigen's potential as a novel immunotherapy for breast cancer.

Oxidized cellulose microneedle patch combined with vascular embolization and local delivery of timolol maleate for hemangiomas

Hemangiomas are superficial tumors characterized by dense vascular structures that often affect the patient's aesthetic appearance due to the obvious red appearance on the skin. Current treatments, especially timolol maleate in the form of eye drops and hydrogels, suffer from low transdermal drug delivery rates, resulting in prolonged treatment time. To address this challenge, our study introduced a soluble microneedle patch with dextran as the main material to form microcatheters for sustained delivery of timolol maleate. In addition, we proposed a vascular embolization strategy to disrupt the blood supply in hemangiomas. Oxidized cellulose (C-cellulose) was selected for its excellent hemostatic properties. We incorporated C-cellulose into dextran microneedles to facilitate thrombosis in the vascular-rich areas of hemangiomas. The innovative microneedle patch we developed can penetrate the skin to a depth of 430 μm and dissolve rapidly within 3 minutes, ensuring direct drug delivery to the subcutaneous layer. Notably, the treated skin area regained its original appearance within two hours after treatment. In addition to excellent skin permeability and rapid dissolution, these patches significantly promoted apoptosis and inhibited cell migration in mouse hemangioendothelioma EOMA cells. Our results demonstrate that this approach not only achieves significant tumor inhibition in a mouse hemangioma model, but also represents a more effective, convenient, and non-invasive treatment option. Therefore, dextran/C-cellulose/timolol maleate microneedle patch (MNs/Timolol) has broad clinical application prospects in the treatment of hemangiomas, minimizing the risk of additional damage and improving treatment efficacy.

CD151 identifies an NK cell subset that is enriched in COVID-19 patients and correlates with disease severity

Severe coronavirus disease 2019 (COVID-19) often leads to acute respiratory distress syndrome and multi-organ dysfunction, driven by a dysregulated immune response, including a cytokine storm with elevated proinflammatory cytokine levels. Natural killer (NK) cells are part of the innate immune system with a fundamental role in the defense against viral infections. However, during COVID-19 acute infection, they exhibit an altered phenotype and impaired functionality contributing to the immunopathogenesis of the disease. In this work, we have studied a cohort of patients with COVID-19 (ranging from mild to severe) by analyzing IL-15, TGF-β, PlGF and GDF-15 plasma levels and performing multiparametric flow cytometry studies. Our results revealed that severe COVID-19 patients exhibited high levels of IL-15, PlGF and GDF-15, along with an enrichment of an NK cell subset expressing the CD151 tetraspanin, which correlated with IL-15 plasma levels and disease severity. In patients, these CD151+ NK cells displayed a more activated phenotype characterized by an increased expression of HLA-DR, CD38 and granzyme B, a distinct receptor repertoire, with lower levels of CD160 and CD31 and higher levels of CD55 and, remarkably, a higher expression of tissue-resident markers CD103 and the NK cell decidual marker CD9. Last of all, in individuals with severe disease, we identified an expansion of a CD151brightCD9+ NK cell subset, suggesting that these cells play a specific role in COVID-19. Altogether, our findings suggest that CD151+ NK cells may have a relevant role in COVID-19 immunopathogenesis.

CEACAM1 increased the lymphangiogenesis through miR-423-5p and NF- kB in Non-Small Cell Lung Cancer

Background

Lung cancer causes significant mortality, with invasion and metastasis being the main features that cause most cancer deaths. Lymph node metastasis is the primary metastatic route in non-small cell carcinoma (NSCLC) and influences the staging and prognosis of NSCLC. Cumulative studies have reported that Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is involved in the progression of various cancers. However, few studies have discussed the function of CEACAM1 in lymphangiogenesis in NSCLC. Here, we examined how CEACAM1 influences lymphangiogenesis in NSCLC.

Methods

A total of 30 primary squamous cell carcinoma (LUSC) patients diagnosed with LN metastasis were prospectively selected. LUSC tumor tissues, para-cancerous tissues, and positive lymph node tissues were harvested. The expression and subcellular location of CEACAM1, CD31, and LVYE1 in clinical samples were detected by immunohistochemistry. Next, the CEACAM1 and hsa-miR-423-5p expressions were detected by qPCR. The protein expression of lymphangiogenesis-associated proteins and critical cytokines of the NF-κB pathway in HDLECs was detected by Western blot. A tube formation assay was performed to detect the lymphangiogenesis in different groups. The interaction between CEACAM1 and hsa-miR-423-5p was verified using a dual luciferase assay.

Results

CEACAM1 was found to be a potential gene associated with lung cancer prognosis. It was positively correlated with angiogenesis and lymphangiogenesis. Then, we detected the function of CEACAM1 in lymphangiogenesis and found that CEACAM1 promoted lymphangiogenesis. hsa-miR-423-5p overexpression inhibited lymphangiogenesis via targeting CEACAM1. Finally, we observed that CEACAM1 can activate the NF-κB pathway and, therefore, promote lymphangiogenesis.

Conclusion

We found that CEACAM1 enhanced lymphangiogenesis in NSCLC via NF-kB activation and was repressed by miR-423-5p. This suggests the value of CEACAM1 as a new therapeutic marker in NSCLC.

Enhancing the biological integration of massive bone allografts: A porcine preclinical in vivo pilot-study

Critical bone loss can have several origins: infections, tumors or trauma. Therefore, massive bone allograft can be a solution for limb salvage. Such a biological reconstruction should have the ideal biomechanical qualities. However, their complication rate remains too high. Perfusion-decellularization of massive allografts could promote the vitality of these grafts, thereby improving their integration and bone remodeling. Three perfusion-decellularized massive bone allografts were compared to 3 fresh frozen massive bone allografts in a preclinical in vivo porcine study using an orthopedic surgery model. Three pigs each underwent a critical diaphyseal femoral defects followed by an allogeneic intercalary femoral graft on their both femurs (one decellularized and one conventional fresh frozen as "native") to reconstruct the defect. Clinical imaging was performed over 3 months of follow-up. The grafts were then explanted and examined by non-decalcified histology, fluoroscopic microscopy and immunohistochemistry. Bone consolidation was achieved in both groups at the same time. However, the volume of bone callus appeared to be greater in the decellularized group. Histology demonstrated a superior bone remodeling in the decellularized group, with a higher number of osteoclasts (p < 0.001) and larger areas of osteoid matrix and newly formed bone as compared to the "native" group. Immunohistochemistry showed a superior vitality and remodeling in both the cortical and medullary cavities for osteocalcin (p < 0.001), Ki67 (p < 0.001), CD3 (p < 0.001) and α-SMA (p < 0.001) as compared the "native" group. Three months after implantation, the decellularized grafts were proven to be biologically more active compared to native grafts. Fluoroscopic microscopy revealed more ossification fronts in the depth of the decellularized grafts (p = 0.021). This pilot study provides the first in vivo demonstration on the enhanced biological capacities of massive bone allograft decellularized by perfusion as compared to conventional massive bone allografts.

Spatial correlation between in vivo imaging and immunohistochemical biomarkers: A methodological study

In this study, we present a method that enables voxel-by-voxel comparison of in vivo imaging to immunohistochemistry (IHC) biomarkers. As a proof of concept, we investigated the spatial correlation between dynamic contrast enhanced (DCE-)CT parameters and IHC biomarkers Ki-67 (proliferation), HIF-1α (hypoxia), and CD45 (immune cells). 54 whole-mount tumor slices of 15 laryngeal and hypopharyngeal carcinomas were immunohistochemically stained and digitized. Heatmaps of biomarker positivity were created and registered to DCE-CT parameter maps. The adiabatic approximation to the tissue homogeneity model was used to fit the following DCE parameters: Ktrans (transfer constant), Ve (extravascular and extracellular space), and Vi (intravascular space). Both IHC and DCE maps were downsampled to 4 × 4 × 3 mm[3] voxels. The mean values per tumor were used to calculate the between-subject correlations between parameters. For the within-subject (spatial) correlation, values of all voxels within a tumor were compared using the repeated measures correlation (rrm). No between-subject correlations were found between IHC biomarkers and DCE parameters, whereas we found multiple significant within-subject correlations: Ve and Ki-67 (rrm = -0.17, P < .001), Ve and HIF-1α (rrm = -0.12, P < .001), Ktrans and CD45 (rrm = 0.13, P < .001), Vi and CD45 (rrm = 0.16, P < .001), and Vi and Ki-67 (rrm = 0.08, P = .003). The strongest correlation was found between IHC biomarkers Ki-67 and HIF-1α (rrm = 0.35, P < .001). This study shows the technical feasibility of determining the 3 dimensional spatial correlation between histopathological biomarker heatmaps and in vivo imaging. It also shows that between-subject correlations do not reflect within-subject correlations of parameters.

Vascular study of decellularized porcine long bones: Characterization of a tissue engineering model

INTRODUCTION

Massive bone allografts enable the reconstruction of critical bone defects in numerous conditions (e.g. tumoral, infection or trauma). Unfortunately, their biological integration remains insufficient and the reconstruction may suffer from several postoperative complications. Perfusion-decellularization emerges as a tissue engineering potential solution to enhance osseointegration. Therefore, an intrinsic vascular study of this novel tissue engineering tool becomes essential to understand its efficacy and applicability.

MATERIAL AND METHODS

32 porcine long bones (humeri and femurs) were used to assess the quality of their vascular network prior and after undergoing a perfusion-decellularization protocol. 12 paired bones were used to assess the vascular matrix prior (N = 6) and after our protocol (N = 6) by immunohistochemistry. Collagen IV, Von Willebrand factor and CD31 were targeted then quantified. The medullary macroscopic vascular network was evaluated with 12 bones: 6 were decellularized and the other 6 were, as control, not treated. All 12 underwent a contrast-agent injection through the nutrient artery prior an angio CT-scan acquisition. The images were processed and the length of medullary vessels filled with contrast agent were measured on angiographic cT images obtained in control and decellularized bones by 4 independent observers to evaluate the vascular network preservation. The microscopic cortical vascular network was evaluated on 8 bones: 4 control and 4 decellularized. After injection of gelatinous fluorochrome mixture (calcein green), non-decalcified fluoroscopic microscopy was performed in order to assess the perfusion quality of cortical vascular lacunae.

RESULTS

The continuity of the microscopic vascular network was assessed with Collagen IV immunohistochemistry (p-value = 0.805) while the decellularization quality was observed through CD31 and Von Willebrand factor immunohistochemistry (p-values <0.001). The macroscopic vascular network was severely impaired after perfusion-decellularization; nutrient arteries were still patent but the amount of medullary vascular channels measured was significantly higher in the control group compared to the decellularized group (p-value <0.001). On average, the observers show good agreement on these results, except in the decellularized group where more inter-observer discrepancies were observed. The microscopic vascular network was observed with green fluoroscopic signal in almost every canals and lacunae of the bone cortices, in three different bone locations (proximal metaphysis, diaphysis and distal metaphysis).

CONCLUSION

Despite the aggressiveness of the decellularization protocol on medullary vessels, total porcine long bones decellularized by perfusion retain an acellular cortical microvascular network. By injection through the intact nutrient arteries, this latter vascular network can still be used as a total bone infusion access for bone tissue engineering in order to enhance massive bone allografts prior implantation.

Expression of angiogenic factors in the placenta of heme oxygenase-1 deficient mouse embryo

Heme oxygenase 1 (Hmox1), the inducible form of heme degrading enzymes Hmoxs, is important for establishment and maintenance of pregnancy. A growing body of evidence suggests an association between Hmox1 and angiogenesis, including placental angiogenesis. In this study, we examined the expression of two angiogenic factors in the placentas of Hmox1 deficient mouse embryos, whose expression was found to be related to that of Hmox1. Relative protein levels and localization of Hmoxs and two angiogenic factors [Vegf and Prolactin along with their receptors, and Cd31/Pecam1] were compared in the placentas of Hmox1 wildtype and knockout mouse embryos using western blotting and immunohistochemistry along with histological analysis. The results revealed tissue disorganisation, reduced area of labyrinth and smaller nuclear size of trophoblast giant cell in the placentas of knockout embryos. The levels of Hmox2, prolactin, and Cd31/Pecam1 were found to be altered in knockout placentas, whereas Vegf and its receptors seem to be unaltered in our samples. Overall, our findings imply that Hmox2 is unlikely to compensate for Hmox1 deficiency in knockout placentas, and altered levels of prolactin and Cd31/Pecam1 hint towards impaired angiogenesis in these placentas. Further investigation would be needed to understand the molecular mechanism of defective angiogenesis in the placentas of Hmox1 knockout mouse embryos.

CD31 signaling promotes the detachment at the uropod of extravasating neutrophils allowing their migration to sites of inflammation

Effective neutrophil migration to sites of inflammation is crucial for host immunity. A coordinated cascade of steps allows intravascular leukocytes to counteract the shear stress, transmigrate through the endothelial layer, and move toward the extravascular, static environment. Those events are tightly orchestrated by integrins, but, while the molecular mechanisms leading to their activation have been characterized, the regulatory pathways promoting their detachment remain elusive. In light of this, it has long been known that platelet-endothelial cell adhesion molecule (Pecam1, also known as CD31) deficiency blocks leukocyte transmigration at the level of the outer vessel wall, yet the associated cellular defects are controversial. In this study, we combined an unbiased proteomic study with in vitro and in vivo single-cell tracking in mice to study the dynamics and role of CD31 during neutrophil migration. We found that CD31 localizes to the uropod of migrating neutrophils along with closed β2-integrin and is required for essential neutrophil actin/integrin polarization. Accordingly, the uropod of Pecam1-/- neutrophils is unable to detach from the extracellular matrix, while antagonizing integrin binding to extracellular matrix components rescues this in vivo migratory defect. Conversely, we showed that sustaining CD31 co-signaling actively favors uropod detachment and effective migration of extravasated neutrophils to sites of inflammation in vivo. Altogether, our results suggest that CD31 acts as a molecular rheostat controlling integrin-mediated adhesion at the uropod of egressed neutrophils, thereby triggering their detachment from the outer vessel wall to reach the inflammatory sites.

Protective effect of Salvia hispanica (chia seeds) against obesity induced ovarian disorders in rat model

The main goal of the current report is to assess the protective impacts of chia seeds against obesity-induced ovarian dysfunctions with a trial to elucidate the mechanism of action. Forty rats were divided into 4 groups including lean untreated, lean consuming chia seeds, obese untreated, and rats consumed high-fat diet (HFD) mixed with ground chia seeds for 10 weeks. Anthropometric measures including visceral fat, peri-ovarian fat, ovarian weights, and duration of the estrous cycle were computed. Serum luteinizing (LH), follicular stimulating (FSH), progesterone, estradiol hormones, and tumor necrosis-α (TNF-α) were estimated. Ovarian histopathology and immunohistochemistry (CD31) were performed. Results showed that chia seeds clearly reduced obesity and induced alteration in anthropometric measures with a clear increase in LH and progesterone. Such seeds notably reversed histopathological alteration and reduced TNF-α, and CD31 induced by HFD. Conclusively, chia seeds have a potential protective role against obesity-induced ovarian dysfunction owing to their anti-inflammatory properties.

CD31 as a probable responding and gate-keeping protein of the blood-brain barrier and the risk of Alzheimer's disease

Several studies have shown that an abnormal vascular-immunity link could increase Alzheimer's disease (AD) risk; however, the mechanism is unclear. CD31, also named platelet endothelial cell adhesion molecule (PECAM), is a surface membrane protein of both endothelial and immune cells and plays important roles in the interaction between the vascular and immune systems. In this review, we focus on research regarding CD31 biological actions in the pathological process that may contribute to AD based on the following rationales. First, endothelial, leukocyte and soluble forms of CD31 play multi-roles in regulating transendothelial migration, increasing blood-brain barrier (BBB) permeability and resulting in neuroinflammation. Second, CD31 expressed by endothelial and immune cells dynamically modulates numbers of signaling pathways, including Src family kinases, selected G proteins, and β-catenin which in turn affect cell-matrix and cell-cell attachment, activation, permeability, survival, and ultimately neuronal cell injury. In endothelia and immune cells, these diverse CD31-mediated pathways act as a critical regulator in the immunity-endothelia-brain axis, thereby mediating AD pathogenesis in ApoE4 carriers, which is the major genetic risk factor for AD. This evidence suggests a novel mechanism and potential drug target for CD31 in the background of genetic vulnerabilities and peripheral inflammation for AD development and progression.

Lymphocyte Subsets and Pulmonary Nodules to Predict the Progression of Sarcoidosis

The search for biological markers, which allow a relatively accurate assessment of the individual course of pulmonary sarcoidosis at the time of diagnosis, remains one of the research priorities in this field of pulmonary medicine. The aim of our study was to investigate possible prognostic factors for pulmonary sarcoidosis with a special focus on cellular immune inflammation markers. A 2-year follow-up of the study population after the initial prospective and simultaneous analysis of lymphocyte activation markers expression in the blood, as well as bronchoalveolar lavage fluid (BALF) and lung biopsy tissue of patients with newly diagnosed pulmonary sarcoidosis, was performed. We found that some blood and BAL fluid immunological markers and lung computed tomography (CT) patterns have been associated with a different course of sarcoidosis. We revealed five markers that had a significant negative association with the course of sarcoidosis (worsening pulmonary function tests and/or the chest CT changes)-blood CD4+CD31+ and CD4+CD44+ T lymphocytes, BALF CD8+CD31+ and CD8+CD103+ T lymphocytes and a number of lung nodules on chest CT at the time of the diagnosis. Cut-off values, sensitivity, specificity and odds ratio for predictors of sarcoidosis progression were calculated. These markers may be reasonable predictors of sarcoidosis progression.

The molecular mechanism of Gorham syndrome: an update

Gorham syndrome, also known as "vanishing osteopathy" and "invasive hemangiomatosis," is a rare clinical syndrome whose etiology is unknown and can invade the whole-body skeleton. At present, more than 300 cases have been reported at home and abroad, usually manifesting as spontaneous chronic osteolysis with no periosteal reaction at the lysis site and occult onset, often with fractures, scoliosis, chylothorax, etc. When waiting for medical treatment, the condition is serious, and the prognosis is poor. At present, there is no effective treatment. The main pathological manifestations of Gorham syndrome are the non-neoplastic abnormal proliferation of lymphatic vessels or blood vessels and osteolysis caused by osteoclast proliferation or increased activity. At present, there is no unified conclusion regarding Gorham syndrome's pathogenesis. This paper starts with the two most studied osteolysis methods at present, osteoclast osteolysis and osteolysis caused by vascular and lymphatic proliferation and summarizes the corresponding most possible molecular mechanisms in recent years to provide more ideas for Gorham syndrome treatment.

Small extracellular vesicles are released ex vivo from platelets into serum and from residual blood cells into stored plasma

Small extracellular vesicles (sEV) purified from blood have great potential clinically as biomarkers for systemic disease; however interpretation is complicated by release of sEV ex vivo after blood taking. To quantify the problem and devise ways to minimise it, we characterised sEV in paired serum, plasma and platelet poor plasma (PPP) samples from healthy donors. Immunoblotting showed twofold greater abundance of CD9 in sEV fractions from fresh serum than from fresh plasma or PPP. MACSPlex confirmed this, and showed that proteins expressed on platelet sEV, either exclusively (CD41b, CD42a and CD62P) or more widely (HLA-ABC, CD24, CD29 and CD31) were also twofold more abundant; by contrast non-platelet proteins (including CD81) were no different. Storage of plasma (but not serum) increased abundance of platelet and selected leukocyte sEV proteins to at least that of serum, and this could be recapitulated by activating cells in fresh plasma by Ca2+, an effect abrogated in PPP. This suggests that a substantial proportion of sEV in serum and stored plasma were generated ex vivo, which is not the case for fresh plasma or PPP. Thus we provide strategies to minimise ex vivo sEV generation and criteria for identifying those that were present in vivo.

Tissue-specific abundance of interferon-gamma drives regulatory T cells to restrain DC1-mediated priming of cytotoxic T cells against lung cancer

Local environmental factors influence CD8+ T cell priming in lymph nodes (LNs). Here, we sought to understand how factors unique to the tumor-draining mediastinal LN (mLN) impact CD8+ T cell responses toward lung cancer. Type 1 conventional dendritic cells (DC1s) showed a mLN-specific failure to induce robust cytotoxic T cells responses. Using regulatory T (Treg) cell depletion strategies, we found that Treg cells suppressed DC1s in a spatially coordinated manner within tissue-specific microniches within the mLN. Treg cell suppression required MHC II-dependent contact between DC1s and Treg cells. Elevated levels of IFN-γ drove differentiation Treg cells into Th1-like effector Treg cells in the mLN. In patients with cancer, Treg cell Th1 polarization, but not CD8+/Treg cell ratios, correlated with poor responses to checkpoint blockade immunotherapy. Thus, IFN-γ in the mLN skews Treg cells to be Th1-like effector Treg cells, driving their close interaction with DC1s and subsequent suppression of cytotoxic T cell responses.

Personalized risk predictor for acute cellular rejection in lung transplant using soluble CD31

We evaluated the contribution of artificial intelligence in predicting the risk of acute cellular rejection (ACR) using early plasma levels of soluble CD31 (sCD31) in combination with recipient haematosis, which was measured by the ratio of arterial oxygen partial pressure to fractional oxygen inspired (PaO₂/FiO₂) and respiratory SOFA (Sequential Organ Failure Assessment) within 3 days of lung transplantation (LTx). CD31 is expressed on endothelial cells, leukocytes and platelets and acts as a "peace-maker" at the blood/vessel interface. Upon nonspecific activation, CD31 can be cleaved, released, and detected in the plasma (sCD31). The study included 40 lung transplant recipients, seven (17.5%) of whom experienced ACR. We modelled the plasma levels of sCD31 as a nonlinear dependent variable of the PaO₂/FiO₂ and respiratory SOFA over time using multivariate and multimodal models. A deep convolutional network classified the time series models of each individual associated with the risk of ACR to each individual in the cohort.

Full spectrum flow cytometry reveals mesenchymal heterogeneity in first trimester placentae and phenotypic convergence in culture, providing insight into the origins of placental mesenchymal stromal cells

Single-cell technologies (RNA-sequencing, flow cytometry) are critical tools to reveal how cell heterogeneity impacts developmental pathways. The placenta is a fetal exchange organ, containing a heterogeneous mix of mesenchymal cells (fibroblasts, myofibroblasts, perivascular, and progenitor cells). Placental mesenchymal stromal cells (pMSC) are also routinely isolated, for therapeutic and research purposes. However, our understanding of the diverse phenotypes of placental mesenchymal lineages, and their relationships remain unclear. We designed a 23-colour flow cytometry panel to assess mesenchymal heterogeneity in first-trimester human placentae. Four distinct mesenchymal subsets were identified; CD73⁺CD90⁺ mesenchymal cells, CD146⁺CD271⁺ perivascular cells, podoplanin⁺CD36⁺ stromal cells, and CD26⁺CD90⁺ myofibroblasts. CD73⁺CD90⁺ and podoplanin + CD36+ cells expressed markers consistent with cultured pMSCs, and were explored further. Despite their distinct ex-vivo phenotype, in culture CD73⁺CD90⁺ cells and podoplanin⁺CD36⁺ cells underwent phenotypic convergence, losing CD271 or CD36 expression respectively, and homogenously exhibiting a basic MSC phenotype (CD73⁺CD90⁺CD31^-CD144^-CD45^-). However, some markers (CD26, CD146) were not impacted, or differentially impacted by culture in different populations. Comparisons of cultured phenotypes to pMSCs further suggested cultured pMSCs originate from podoplanin⁺CD36⁺ cells. This highlights the importance of detailed cell phenotyping to optimise therapeutic capacity, and ensure use of relevant cells in functional assays.

PECAM-1 Is Down-Regulated in γδT Cells during Remission, but Up-Regulated in Relapse of Multiple Sclerosis

Introduction. PECAM-1 and NKRP1A are both involved in the vascular transmigration of T lymphocytes. Vascular transmigration is a crucial process in multiple sclerosis pathogenesis. Methods and aim. The current paper presents an analysis of PECAM-1 and NKRP1A expression on γδ T cells. Expression of PECAM-1 and NKRP1A on subsets of γδ T cells was performed with flow cytometry. Results. Based on the flow cytometry data, PECAM1 was slightly differentially modulated on γδ T cells-it was up-regulated during relapse, but down-regulated during remission. Moreover, a significant downregulation of CD3 expression was noted on γδ T cells from MS patients, most notably during relapse. Conclusions. This may be a sign of the overall activation of γδ T cells in the course of multiple sclerosis.

The Regulatory-T-Cell Memory Phenotype: What We Know

In immunology, the discovery of regulatory T (Treg) cells was a major breakthrough. Treg cells play a key role in pregnancy maintenance, in the prevention of autoimmune responses, and in the control of all immune responses, including responses to self cells, cancer, infection, and a transplant. It is currently unclear whether Treg cells are capable of long-term memory of an encounter with an antigen. Although the term “immunological memory” usually means an enhanced ability to protect the body from reinfection, the memory of the suppressive activity of Treg cells helps to avoid the state of generalized immunosuppression that may result from the second activation of the immune system. In this review, we would like to discuss the concept of regulatory memory and in which tissues memory Treg cells can perform their functions.

Treatment of high fat diet-induced obese pregnant mice with IL-6 receptor antibody does not ameliorate placental function and fetal growth restriction

PROBLEM

Pregnancy complications and adverse birth outcomes are in part fueled by the rise in obesity and its associated co-morbidities in western societies. Fetal healthy development and placental function are disturbed by an obese, inflammatory environment associated with cytokines, such as interleukin-6, causing inadequate supply of nutrients to the fetus and perinatal programming with severe health consequences.

METHOD OF STUDY

Mice received high fat diet (HFD) before and during gestation to induce obesity. We performed an IL-6 receptor antibody (MR16-1) treatment in pregnant obese mice at embryonic days E0.5, E7.5 and E14.5 to investigate whether this could ameliorate HFD-induced and obesity-associated placental dysfunction, evaluated by stereology and western blot, and improve offspring outcome at E15.5 in obese dams.

RESULTS

We observed fewer fetuses below the 10th percentile and placental vascularization was less aggravated following MR16-1 treatment of obese dams, showing slight improvements in labyrinth zone (Lz) vascularization. However, placental dysfunction and fetal growth restriction were still apparent in MR16-1 dams compared to lean control dams. Molecular analysis showed significantly elevated IL-6 level in placentas of MR16-1 treated dams.

CONCLUSION

Treatment with MR16-1 blocks IL-6 signaling in the placenta, but has only limited effects on preventing HFD-associated placental dysfunction and offspring outcomes in mice, suggesting further mechanisms in the deterioration of placental vascularization and fetal nutrient supply as a consequence of maternal obesity.

Neuroinflammation creates an immune regulatory niche at the meningeal lymphatic vasculature near the cribriform plate

Meningeal lymphatics near the cribriform plate undergo lymphangiogenesis during neuroinflammation to drain excess fluid. Here, we hypothesized that lymphangiogenic vessels may acquire an altered phenotype to regulate immunity. Using single-cell RNA sequencing of meningeal lymphatics near the cribriform plate from healthy and experimental autoimmune encephalomyelitis in the C57BL/6 model, we report that neuroinflammation induces the upregulation of genes involved in antigen presentation such as major histocompatibility complex class II, adhesion molecules including vascular cell adhesion protein 1 and immunoregulatory molecules such as programmed cell death 1 ligand 1, where many of these changes are mediated by interferon-γ. The inflamed lymphatics retain CD11c+ cells and CD4 T cells where they capture and present antigen, creating an immunoregulatory niche that represents an underappreciated interface in the regulation of neuroinflammation. We also found discontinuity of the arachnoid membrane near the cribriform plate, which provides unrestricted access to the cerebrospinal fluid. These findings highlight a previously unknown function of local meningeal lymphatics in regulating immunity that has only previously been characterized in draining lymph nodes.

Cigarette smoke-induced extracellular vesicles from dendritic cells alter T-cell activation and HIV replication

Despite decreased rates of tobacco smoking in many areas, cigarette smoking remains a major contributor to many health problems. Cigarette smoking can reduce immune system functioning while concurrently increasing inflammation. Dendritic cells in the lung exposed to cigarette smoke become stimulated and go on to activate T-cells. Extracellular vesicles (EVs) are nano-sized particles released by cells. They participate in intercellular communication by transferring functional proteins and nucleic acids to recipient cells and have been implicated in immune responses. For example, they can display MHC-peptide complexes to activate T-cells. In the current study, we sought to understand the role of cigarette smoke extract (CSE) on dendritic cell-derived EVs and their capacity to activate and differentiate T-cells. Primary human dendritic cells (iDCs) were exposed to CSE and EVs were separated and characterized. We exposed autologous primary CD4 + T-cells to iDC-EVs and observed T helper cell populations skewing towards Th1 and Th17 phenotypes. As HIV + individuals are disproportionately likely to be current smokers, we also examined the effects of iDC-EVs on acutely infected T-cells as well as on a cell model of HIV latency (ACH-2). We found that in most cases, iDC-CSE EVs tended to reduce p24 release from the acutely infected primary T-cells, albeit with great variability. We did not observe large effects of iDC-EVs or direct CSE exposure on p24 release from the ACH-2 cell line. Together, these data suggest that iDC-CSE EVs have the capacity to modulate the immune responses, in part by pushing T-cells towards Th1 and Th17 phenotypes.

Clinicopathological study of the polypoidal lesions of polypoidal choroidal vasculopathy

PURPOSE

To investigate the pathogenic features of the polypoidal lesions from the specimens of polypoidal choroidal vasculopathy extracted from human subjects.

METHODS

Seven specimens of polypoidal lesions extracted from five eyes of six patients (mean age, 60.16 ± 10.41 years) of polypoidal choroidal vasculopathy were examined. The polypoidal lesions were obtained by surgical excision. Thereafter, a histopathological analysis of the specimens was performed.

RESULTS

The polypoidal lesions were oval nodules located underneath the retinal pigment epithelium. A pathological study of the lesions revealed that Bruch's membrane schisis was observed in all specimens and they were all located in the Bruch's membrane. The Bruch's membrane schisis and serosanguineous materials constituted the main structure of the lesions in five of the seven specimens, with small vessels being observed in two specimens. One specimen was composed of two polypoidal lesions of different characteristics, and one specimen had a neovessel membrane complex with several polypoidal lesions. Inflammatory cells and blood vessels were observed in the polypoidal lesion of the specimen with neovessel membrane complex.

CONCLUSION

Polypoidal lesions of polypoidal choroidal vasculopathy are abnormalities of the Bruch's membrane. The lesions are characterized by the Bruch's membrane schisis, which is filled with serosanguineous materials. The lesions are progressive and may contain inflammatory cells and blood vessels.

Extracellular Vesicles as Biomarkers of Acute Graft-vs.-Host Disease After Haploidentical Stem Cell Transplantation and Post-Transplant Cyclophosphamide

Even with high-dose post-transplant cyclophosphamide (PT-Cy) which was initially introduced for graft-versus-host disease (GvHD) prevention in the setting of HLA-haploidentical transplantation, both acute and chronic GvHDs remain a major clinical challenge. Despite improvements in the understanding of the pathogenesis of both acute and chronic GvHDs, reliable biomarkers that predict their onset have yet to be identified. We recently studied the potential correlation between extracellular vesicles (EVs) and the onset of acute (a)GvHD in transplant recipients from related and unrelated donors. In the present study, we further investigated the role of the expression profile of membrane proteins and their microRNA (miRNA) cargo (miRNA100, miRNA155, and miRNA194) in predicting the onset of aGvHD in haploidentical transplant recipients with PT-Cy. Thirty-two consecutive patients were included. We evaluated the expression profile of EVs, by flow cytometry, and their miRNA cargo, by real-time PCR, at baseline, prior, and at different time points following transplant. Using logistic regression and Cox proportional hazard models, a significant association between expression profiles of antigens such as CD146, CD31, CD140a, CD120a, CD26, CD144, and CD30 on EVs, and their miRNA cargo with the onset of aGvHD was observed. Moreover, we also investigated a potential correlation between EV expression profile and cargo with plasma biomarkers (e.g., ST2, sTNFR1, and REG3a) that had been associated with aGVHD previously. This analysis showed that the combination of CD146, sTNFR1, and miR100 or miR194 strongly correlated with the onset of aGvHD (AUROC >0.975). A large prospective multicenter study is currently in progress to validate our findings.

Inhibition of hypoxia-inducible factor-1 by Salidroside in an in vitro model of choroidal neovascularization

PURPOSE

As a characteristic of age-related macular degeneration (AMD), choroidal neovascularization (CNV) causes severe vision loss. The current treatment has limited efficacy. This study was to investigate effects of Salidroside against CNV and explore its underlying mechanisms.

METHODS

RF/6A cells were treated with 200 mM cobalt chloride (CoCl₂) for 6 hr to mimic hypoxic condition. Cells were then treated with Salidroside at 10, 30 and 100 µM for 24 hr. Cells treated with DMSO were used as negative control. The cell proliferation was assessed using 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium-bromid assay. The tube formation was investigated on Matrigel. The cell migration was measured by a Transwell assay. RT-qPCR was used to detect the gene expression. Immuohistochemistry and western blot were used to detect the expression of proteins.

RESULTS

Salidroside significantly inhibited the cell migration and tube formation activity of RF/6A cells under hypoxia. Moreover, Salidroside reduced the expression levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 (HIF-1) in RF/6A cells.

CONCLUSIONS

Our data suggested that Salidroside could be a potential novel therapeutic agent against CNV.

Multifunctional 3D-Printed Wound Dressings

Personalized wound dressings provide enhanced healing for different wound types; however multicomponent wound dressings with discretely controllable delivery of different biologically active agents are yet to be developed. Here we report 3D-printed multicomponent biocomposite hydrogel wound dressings that have been selectively loaded with small molecules, metal nanoparticles, and proteins for independently controlled release at the wound site. Hydrogel wound dressings carrying antibacterial silver nanoparticles and vascular endothelial growth factor with predetermined release profiles were utilized to study the physiological response of the wound in a mouse model. Compared to controls, the application of dressings resulted in improvement in granulation tissue formation and differential levels of vascular density, dependent on the release profile of the growth factor. Our study demonstrates the versatility of the 3D-printed hydrogel dressings that can yield varied physiological responses in vivo and can further be adapted for personalized treatment of various wound types.

Proteomics and metabonomics analyses of Covid-19 complications in patients with pulmonary fibrosis

Pulmonary fibrosis is a devastating disease, and the pathogenesis of this disease is not completely clear. Here, the medical records of 85 Covid-19 cases were collected, among which fibrosis and progression of fibrosis were analyzed in detail. Next, data independent acquisition (DIA) quantification proteomics and untargeted metabolomics were used to screen disease-related signaling pathways through clustering and enrichment analysis of the differential expression of proteins and metabolites. The main imaging features were lesions located in the bilateral lower lobes and involvement in five lobes. The closed association pathways were FcγR-mediated phagocytosis, PPAR signaling, TRP-inflammatory pathways, and the urea cycle. Our results provide evidence for the detection of serum biomarkers and targeted therapy in patients with Covid-19.

Endothelial-to-Mesenchymal Transition in Pulmonary Arterial Hypertension

Endothelial-to-mesenchymal transition (EndMT) is a process that encompasses extensive transcriptional reprogramming of activated endothelial cells leading to a shift toward mesenchymal cellular phenotypes and functional responses. Initially observed in the context of embryonic development, in the last few decades EndMT is increasingly recognized as a process that contributes to a variety of pathologies in the adult organism. Within the settings of cardiovascular biology, EndMT plays a role in various diseases, including atherosclerosis, heart valvular disease, cardiac fibrosis, and myocardial infarction. EndMT is also being progressively implicated in development and progression of pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH). This review covers the current knowledge about EndMT in PH and PAH, and provides comprehensive overview of seminal discoveries. Topics covered include evidence linking EndMT to factors associated with PAH development, including hypoxia responses, inflammation, dysregulation of bone-morphogenetic protein receptor 2 (BMPR2), and redox signaling. This review amalgamates these discoveries into potential insights for the identification of underlying mechanisms driving EndMT in PH and PAH, and discusses future directions for EndMT-based therapeutic strategies in disease management.

Characterization of CD31 expression in CD4+ and CD8+T cell subpopulations in chronic untreated HIV infection

BACKGROUND

The platelet endothelial cell adhesion molecule-1 (PECAM-1) or CD31 has been involved in regulation of T-cell tolerance, activation, survival and homing in mice cells. However, there is limited knowledge about the expression pattern and role of this molecule in human T cells, particularly in conditions of chronic immune activation.

OBJECTIVES

We explored CD31 expression in T cell differentiation subsets of individuals with untreated HIV infection and in non-HIV-infected controls. We also assessed phenotypic differences between CD31+ and CD31- subsets in memory and terminally differentiated (TEMRA) CD4+ and CD8 + T cells.

METHODS

Forty-one individuals with untreated HIV infection and 34 non-HIV-infected controls were included in the study. We compared the expression of CD31 in CD4+ and CD8 + T cells across stages of differentiation in the two study groups by flow cytometry. We also analyzed the expression of CD57 (a marker of senescence), Ki67 (a marker of cycling cells), PD-1 (a marker of exhaustion), and CD38/HLA-DR (a marker of immune activation) on memory and TEMRA CD31+ and CD31- T cells.

RESULTS

CD31 expression was significantly higher in CD8 + T cells than in CD4 + T cells, measured as frequency, absolute numbers and median fluorescence intensity (MFI), in both study groups (p < 0.0001 in all cases). Intermediate differentiation subsets of CD4+ and CD8 + T cells expressed higher levels of CD31 in the context of HIV infection (p < 0.001 in all cases). CD31 expression frequency decreased with cellular differentiation of CD4+ and CD8 + T cells in both groups, but this decrease was steeper in individuals without HIV infection (CD4+: p < 0.001 and CD8+: p < 0.0001). As expected, memory and TEMRA CD4+ and CD8 + T cells expressed significantly higher levels of CD57, PD-1, Ki67 and CD38/HLA-DR in HIV-infected compared to non-HIV-infected individuals (p < 0.01 in all cases). CD31 expression was associated with lower activation of memory (but not TEMRA) CD4 + T cells in non-HIV-infected persons, an effect not observed in the HIV-infected group. CD31 expression on memory CD8 + T cells of HIV-infected individuals was associated higher levels of PD-1 (p = 0.0019) and CD38/HLADR (p = 0.0345), and higher PD-1 expression on CD8 + TEMRA (p = 0.0024), an effect not observed in non-HIV-infected individuals.

CONCLUSION

In the context of HIV-associated chronic immune activation, specifically on memory CD8 + T cells, CD31 expression was associated with higher PD-1 and CD38/HLA-DR co-expression, suggesting that CD31 expression may result from an insufficient attempt to contain T cell exhaustion and activation. CD31-targeted therapies may contribute to modulate these cellular responses.

CD31+, CD38+, CD44+, and CD103+ lymphocytes in peripheral blood, bronchoalveolar lavage fluid and lung biopsy tissue in sarcoid patients and controls

Background

The mechanisms driving the transition from inflammation to fibrosis in sarcoidosis patients are poorly understood; prognostic features are lacking. Immune cell profiling may provide insights into pathogenesis and prognostic factors of the disease. This study aimed to establish associations in simultaneous of lymphocyte subset profiles in the blood, bronchoalveolar lavage fluid (BALF), and lung biopsy tissue in the patients with newly diagnosed sarcoidosis.

Methods

A total of 71 sarcoid patients (SPs) and 20 healthy controls (HCs) were enrolled into the study. CD31, CD38, CD44, CD103 positive T lymphocytes in blood and BALF were analysed. Additionally, the densities of CD4, CD8, CD38, CD44, CD103 positive cells in lung tissue biopsies were estimated by digital image analysis.

Results

Main findings: (I) increase of percentage of CD3⁺CD4⁺CD38⁺ in BALF and blood, and increase of percentage of CD3⁺CD4⁺CD44⁺ in BALF in Löfgren syndrome patients comparing with patients without Löfgren syndrome, (II) increase of percentage of CD3⁺CD4⁺103⁺ in BALF and in blood in patients without Löfgren syndrome (comparing with Löfgren syndrome patients) and increase of percentage of CD3⁺CD4⁺103⁺ in BALF and in blood in more advanced sarcoidosis stage. (III) Increasing percentage of BALF CD3⁺CD4⁺CD31⁺ in sarcoidosis patients when comparing with controls independently of presence of Löfgren syndrome, smoking status or stage of sarcoidosis. Several significant correlations were found.

Conclusions

Lymphocyte subpopulations in blood, BALF, and lung tissue were substantially different in SPs at the time of diagnosis compared to HCs. CD3⁺CD4⁺CD31⁺ in BALF might be a potential supporting marker for the diagnosis of sarcoidosis. CD3⁺CD4⁺CD38⁺ in BALF and blood and CD3⁺CD4⁺CD44⁺ in BALF may be markers of the acute immune response in sarcoidosis patients. CD4⁺CD103⁺ T-cells in BALF and in blood are markers of the persistent immune response in sarcoidosis patients and are potential prognostic features of the chronic course of this disease.

Endothelial-Mesenchymal Transition in COVID-19 lung lesions

Sars-Cov-2 infection is still a healthcare emergency and acute respiratory distress failure with Diffuse Alveolar Damage (DAD) features is the main causes of patients’ death. Pathogenic mechanisms of the disease are not clear yet, but new insights are necessary to improve therapeutic management, to prevent fatal irreversible multi-organ damage and to adequately follow up those patients who survive. Here we investigated, by histochemistry and immunohistochemistry, a wide number of mapped lung specimens taken from whole body autopsies of 7 patients dead of COVID-19 disease. Our data confirm morphological data of other authors, and enlarge recent reports of the literature suggesting that Endothelial–Mesenchymal Transition might be central to COVID-19 lung fibrosing lesions. Furthermore, based upon recent acquisition of new roles in immunity and vascular pathology of the CD31 molecule, we hypothesize that this molecule might be important in the development and treatment of COVID-19 pulmonary lesions. These preliminary findings need further investigations to shed light on the complexity of Sars-Cov-2 disease.

Endothelial Barrier Function and Leukocyte Transmigration in Atherosclerosis

The vascular endothelium is a highly specialized barrier that controls passage of fluids and migration of cells from the lumen into the vessel wall. Endothelial cells assist leukocytes to extravasate and despite the variety in the specific mechanisms utilized by different leukocytes to cross different vascular beds, there is a general principle of capture, rolling, slow rolling, arrest, crawling, and ultimately diapedesis via a paracellular or transcellular route. In atherosclerosis, the barrier function of the endothelium is impaired leading to uncontrolled leukocyte extravasation and vascular leakage. This is also observed in the neovessels that grow into the atherosclerotic plaque leading to intraplaque hemorrhage and plaque destabilization. This review focuses on the vascular endothelial barrier function and the interaction between endothelial cells and leukocytes during transmigration. We will discuss the role of endothelial dysfunction, transendothelial migration of leukocytes and plaque angiogenesis in atherosclerosis.

Prognostic Implication of the Expression Level of PECAM-1 in Non-small Cell Lung Cancer

Background: Lung cancer is a malignant disease that threatens human health. Hence, it is crucial to identify effective prognostic factors and treatment targets. Single-cell RNA sequencing can quantify the expression profiles of transcripts in individual cells. Methods: GSE117570 profiles were downloaded from the Gene Expression Omnibus database. Key ligand-receptor genes in the tumor and the normal groups were screened to identify integrated differentially expressed genes (DEGs) from the GSE118370 and The Cancer Genome Atlas Lung Adenocarcinoma databases. DEGs associated with more ligand-receptor pairs were selected as candidate DEGs for Gene Ontology (GO) functional annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and survival analysis. In addition, we conducted validation immunohistochemical experiments on postoperative specimens of 30 patients with lung cancer. Results: A total of 18 candidate DEGs were identified from the tumor and the normal groups. The analysis of the GO biological process revealed that these DEGs were mainly enriched in wound healing, in response to wounding, cell migration, cell motility, and regulation of cell motility, while the KEGG pathway analysis found that these DEGs were mainly enriched in proteoglycans in cancer, bladder cancer, malaria, tyrosine kinase inhibitor resistance in Epidermal Growth Factor Receptor (EGFR), and the ERBB signaling pathway. Survival analysis showed that a high, rather than a low, expression of platelet endothelial cell adhesion molecule-1 (PECAM-1) was associated with improved survival. Similarly, in postoperative patients with lung cancer, we found that the overall survival of the PECAM-1 high-expression group shows a better trend than the PECAM-1 low-expression group (p = 0.172). Conclusions: The candidate DEGs identified in this study may play some important roles in the occurrence and development of lung cancer, especially PECAM-1, which may present potential prognostic biomarkers for the outcome.

Grading of Oral Leukoplakia: Can It be Improvised Using Immunohistochemical Markers p63 and CD31

Introduction

Oral squamous cell carcinoma is usually preceded by potentially malignant disorders (PMDs), the most common being oral leukoplakia. A conservative management protocol is followed for milder dysplastic cases, while severe dysplastic lesions are surgically excised. Several classification systems have been developed based mainly on histopathological features with a lot of inter-observer variations. The present study was done to assess the use of immunohistochemical (IHC) markers in grading leukoplakic lesions in addition to histopathological grading.

Aims and Objectives

To grade leukoplakia using different grading systems and assess if IHC markers can aid in categorizing leukoplakia.

Materials and Methods

Thirty-five cases of leukoplakia were graded using Ljubljana, 2005 World Health Organization (WHO), and Binary System followed by IHC staining with p63 and CD31.

Results and Statistics

Variation was noted in 12 cases while using WHO, 11 using Ljubljana, and 7 using Binary System and was significant on Cohen-Kappa statistics, with the least significant variation noted on Binary System. p63 staining assisted to group doubtful cases and even identify variation in cases graded positively on histopathology. In total, 17 cases stained one-third (mild/low), while 15 cases stained one-half or more (higher grade) epithelial thickness. A weak correlation was observed between all grading systems and p63 on Kendall's Tau-b analysis and the weak correlation was significant for the WHO and binary grading systems. Analyzing p63 and CD31 using Kruskal-Wallis test, an increase in mean vessel density (MVD) was noted for mild/moderate cases but decreased for severe cases.

Conclusion

Addressing histological categorization of PMDs assisted by IHC markers to understand the biological behavior of the tissues is currently essential with studies on more markers to assist in the management protocol.

Prolactin modifies the in vitro LPS-induced chemotactic capabilities in human fetal membranes at the term of gestation

Problem

Immune responses of fetal membranes involve the production of chemoattractant mediators causing infiltration of maternal and fetal leukocytes, intrauterine inflammation and potentially the disruption of maternal‐fetal tolerance. Prolactin (PRL) has deep immunoregulatory effects in the fetal‐maternal interface. We aimed to test the in vitro PRL effect upon chemotactic capacities of human fetal membranes.

Method of Study

Fetal membranes and umbilical cord blood were collected from healthy non‐laboring caesarean deliveries at term. Fetal membranes were cultured in Transwell® frames to mimic the barrier function between choriodecidual and amniotic sides. Tissues were treated with PRL, Lipopolysaccharide (LPS), or both simultaneously. Then, RANTES, MCP‐1, MIP‐1α, IP‐10, and PECAM‐1 were quantified in a conditioned medium by choriodecidual or amniotic sides. The chemotaxis of subsets of migrating mononuclear cells from umbilical cord blood was evaluated in a Boyden Chamber in response to the conditioned medium by both sides.

Results

Lipopolysaccharide stimulates the production of RANTES, MCP‐1, MIP‐1α, and PECAM‐1 in choriodecidua, while MIP‐1α and PECAM‐1 only increase in amnion. PRL decrease RANTES, MCP‐1, and MIP‐1 only in choriodecidua, but PECAM‐1 was decreased mainly in amnion. The leukocyte migration was regulated significantly in response to the conditioned medium by the amnion, increase in the conditioned medium after LPS treatment, contrary with, the leukocyte migration decreased in a significant manner in response to conditioned medium after PRL and LPS‐PRL co‐treatment. Finally, T cells were the most responsive subset of cells.

Conclusions

Prolactin modified in a tissue‐specific manner the chemotactic factor and the leukocyte migration differentially in fetal membranes.

Deep Learning Reveals Key Immunosuppression Genes and Distinct Immunotypes in Periodontitis

Background

Periodontitis is a chronic immuno-inflammatory disease characterized by inflammatory destruction of tooth-supporting tissues. Its pathogenesis involves a dysregulated local host immune response that is ineffective in combating microbial challenges. An integrated investigation of genes involved in mediating immune response suppression in periodontitis, based on multiple studies, can reveal genes pivotal to periodontitis pathogenesis. Here, we aimed to apply a deep learning (DL)-based autoencoder (AE) for predicting immunosuppression genes involved in periodontitis by integrating multiples omics datasets.

Methods

Two periodontitis-related GEO transcriptomic datasets (GSE16134 and GSE10334) and immunosuppression genes identified from DisGeNET and HisgAtlas were included. Immunosuppression genes related to periodontitis in GSE16134 were used as input to build an AE, to identify the top disease-representative immunosuppression gene features. Using K-means clustering and ANOVA, immune subtype labels were assigned to disease samples and a support vector machine (SVM) classifier was constructed. This classifier was applied to a validation set (Immunosuppression genes related to periodontitis in GSE10334) for predicting sample labels, evaluating the accuracy of the AE. In addition, differentially expressed genes (DEGs), signaling pathways, and transcription factors (TFs) involved in immunosuppression and periodontitis were determined with an array of bioinformatics analysis. Shared DEGs common to DEGs differentiating periodontitis from controls and those differentiating the immune subtypes were considered as the key immunosuppression genes in periodontitis.

Results

We produced representative molecular features and identified two immune subtypes in periodontitis using an AE. Two subtypes were also predicted in the validation set with the SVM classifier. Three “master” immunosuppression genes, PECAM1, FCGR3A, and FOS were identified as candidates pivotal to immunosuppressive mechanisms in periodontitis. Six transcription factors, NFKB1, FOS, JUN, HIF1A, STAT5B, and STAT4, were identified as central to the TFs-DEGs interaction network. The two immune subtypes were distinct in terms of their regulating pathways.

Conclusion

This study applied a DL-based AE for the first time to identify immune subtypes of periodontitis and pivotal immunosuppression genes that discriminated periodontitis from the healthy. Key signaling pathways and TF-target DEGs that putatively mediate immune suppression in periodontitis were identified. PECAM1, FCGR3A, and FOS emerged as high-value biomarkers and candidate therapeutic targets for periodontitis.

CD31 Mimetic Coating Enhances Flow Diverting Stent Integration into the Arterial Wall Promoting Aneurysm Healing

BACKGROUND AND PURPOSE

Beyond aneurysmal occlusion, metallic flow diverters (FDs) can induce an adverse endovascular reaction due to the foreignness of metal devices, hampering FD endothelialization across the aneurysm neck, and arterial healing of intracranial aneurysms. Here, we evaluated the potential benefits of an FD coating mimicking CD31, a coreceptor critically involved in endothelial function and endovascular homeostasis, on the endothelialization of FDs implanted in vivo.

METHODS

Nitinol FD (Silk Vista Baby) and flat disks were dip-coated with a CD31-mimetic peptide via an intermediate layer of polydopamine. Disks were used to assess the reaction of endothelial cells and blood elements in vitro. An aneurysm rabbit model was used to compare in vivo effects on the arterial wall of CD31-mimetic-coated (CD31-mimetic, n=6), polydopamine-coated (polydopamine, n=6), and uncoated FDs (bare, n=5) at 4 weeks post-FD implantation. In addition, long-term safety was assessed at 12 weeks.

RESULTS

In vitro, CD31-mimetic coated disks displayed reduced adhesion of blood elements while favoring endothelial cell attachment and confluence, compared to bare and polydopamine disks. Strikingly, in vivo, the neoarterial wall formed over the CD31-mimetic-FD struts at the aneurysm neck was characteristic of an arterial tunica media, with continuous differentiated endothelium covering a significantly thicker layer of collagen and smooth muscle cells as compared to the controls. The rates of angiographic complete occlusion and covered branch arterial patency were similar in all 3 groups.

CONCLUSIONS

CD31-mimetic coating favors the colonization of metallic endovascular devices with endothelial cells displaying a physiological phenotype while preventing the adhesion of platelets and leukocytes. These biological properties lead to a rapid and improved endothelialization of the neoarterial wall at the aneurysm neck. CD31-mimetic coating could therefore represent a valuable strategy for FD biocompatibility improvement and aneurysm healing.

A Method for Isolating and Culturing Skin Cells: Application to Endothelial Cells, Fibroblasts, Keratinocytes, and Melanocytes From Punch Biopsies in Systemic Sclerosis Skin

Systemic Sclerosis (SSc) is a complex auto-immune connective tissue disease combining inflammatory, vasculopathic and fibrotic manifestations. Skin effectively recapitulates the main pathogenic processes and therefore is a good organ to decipher the disease pathophysiology, which remains unclear. However, culturing primary skin cells is SSc can be a major issue due to small sample size combined to skin fibrosis. Here, we present a protocol allowing to isolate and culture the four main types of skin cells: dermal cells (microvascular dermal endothelial cells—HDMECs—and fibroblasts) and epidermal cells (keratinocytes and melanocytes), from a single 4 mm-punch biopsy, at a low cost. The present protocol has been optimized to fit SSc skin cells particularities. Such technique allows to culture primary cells, crucial to study the disease pathophysiology, as well as to isolate cells in order to perform immediate molecular biology experiments such as single-cell transcriptomic. Cells grown from biopsies are also suitable for various types of experiments such as immunocytochemistry, Western blot, RT-qPCR or functional in vitro assays (angiogenesis, migration, etc.). Ultimately, they can be used for experimental 3D cell culture models such as reconstructed skin.

PECAM-1 protects against DIC by dampening inflammatory responses via inhibiting macrophage pyroptosis and restoring vascular barrier integrity

Disseminated intravascular coagulation (DIC) is a frequent complication of sepsis that affects patient outcomes due to accompanying thrombo-inflammation and microvascular permeability changes. Platelet endothelial cell adhesion molecule-1 (PECAM-1), a cellular adhesion and signaling receptor that is expressed on both hematopoietic and endothelial cells, plays an important anti-inflammatory role in acute and chronic inflammatory disease models. Little is known, however, about role and mechanism of PECAM-1 in septic DIC. Here, we investigated whether PECAM-1 might play a protective role in hindering the development of septic DIC. Plasma levels of soluble PECAM-1 were markedly elevated in septic patients that developed DIC, with a correspondingly poorer outcome. PECAM-1 knockout exhibited more severe DIC and poorer outcome in the LPS induced- and cecal ligation and puncture-induced DIC model, which could be alleviated by tissue factor inhibitor. This phenomenon seemed to be equally linked to PECAM-1 expression by both endothelial and blood cells. Furthermore, PECAM-1 was found to exert its protective effect on developing septic DIC by the following 2 distinct mechanisms: the inhibition of macrophage pyroptosis and the acceleration of the restoration of the endothelial cell barrier. Taken together, these results implicate PECAM-1 as a potentially attractive target for the development of novel therapeutics to manage and treat septic DIC.

Mass cytometry reveals immune signatures associated with cytomegalovirus (CMV) control in recipients of allogeneic haemopoietic stem cell transplant and CMV-specific T cells

Objectives

Cytomegalovirus (CMV) is known to have a significant impact on immune recovery post‐allogeneic haemopoietic stem cell transplant (HSCT). Adoptive therapy with donor‐derived or third‐party virus‐specific T cells (VST) can restore CMV immunity leading to clinical benefit in prevention and treatment of post‐HSCT infection. We developed a mass cytometry approach to study natural immune recovery post‐HSCT and assess the mechanisms underlying the clinical benefits observed in recipients of VST.

Methods

A mass cytometry panel of 38 antibodies was utilised for global immune assessment (72 canonical innate and adaptive immune subsets) in HSCT recipients undergoing natural post‐HSCT recovery (n = 13) and HSCT recipients who received third‐party donor‐derived CMV‐VST as salvage for unresponsive CMV reactivation (n = 8).

Results

Mass cytometry identified distinct immune signatures associated with CMV characterised by a predominance of innate cells (monocytes and NK) seen early and an adaptive signature with activated CD8⁺ T cells seen later. All CMV‐VST recipients had failed standard antiviral pharmacotherapy as a criterion for trial involvement; 5/8 had failed to develop the adaptive immune signature by study enrolment despite significant CMV antigen exposure. Of these, VST administration resulted in development of the adaptive signature in association with CMV control in three patients. Failure to respond to CMV‐VST in one patient was associated with persistent absence of the adaptive immune signature.

Conclusion

The clinical benefit of CMV‐VST may be mediated by the recovery of an adaptive immune signature characterised by activated CD8⁺ T cells.

Global alterations to the choroid plexus blood-CSF barrier in amyotrophic lateral sclerosis

The choroid plexus (CP) is a highly vascularized structure located in the ventricles that forms the blood-CSF barrier (BCSFB) and separates the blood from the cerebrospinal fluid (CSF). In addition to its role as a physical barrier, the CP functions in CSF secretion, transport of nutrients into the central nervous system (CNS) and a gated point of entry of circulating immune cells into the CNS. Aging and neurodegeneration have been reported to affect CP morphology and function and increase protein leakage from blood to the CSF. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with both upper and lower motor neuron loss, as well as altered proteomic and metabolomic signatures in the CSF. The role of the BCSFB and the CP in ALS is unknown. Here we describe a transcriptomic and ultrastructural analysis of BCSFB and CP alterations in human postmortem tissues from ALS and non-neurologic disease controls. ALS-CP exhibited widespread disruptions in tight junctional components of the CP epithelial layer and vascular integrity. In addition, we detected loss of pericytes around ALS blood vessels, accompanied by activation of platelet aggregation markers vWF and Fibrinogen, reminiscent of vascular injury. To investigate the immune component of ALS-CP, we conducted a comprehensive analysis of cytokines and chemokine panels in CP lysates and found a significant down-regulation of M-CSF and V-CAM1 in ALS, as well as up-regulation of VEGF-A protein. This phenotype was accompanied by an infiltration of MERTK positive macrophages into the parenchyma of the ALS-CP when compared to controls. Taken together, we demonstrate widespread structural and functional disruptions of the BCSFB in human ALS increasing our understanding of the disease pathology and identifying potential new targets for ALS therapeutic development.

Comparative Analysis of Thymic and Blood Treg in Myasthenia Gravis: Thymic Epithelial Cells Contribute to Thymic Immunoregulatory Defects

The thymus is involved in autoimmune Myasthenia gravis (MG) associated with anti-acetylcholine (AChR) antibodies. In MG, thymic regulatory T cells (Treg) are not efficiently suppressive, and conventional T cells (Tconv) are resistant to suppression. To better understand the specific role of the thymus in MG, we compared the phenotype and function of peripheral and thymic Treg and Tconv from controls and MG patients. Suppression assays with thymic or peripheral CD4 + T cells showed that the functional impairment in MG was more pronounced in the thymus than in the periphery. Phenotypic analysis of Treg showed a significant reduction of resting and effector Treg in the thymus but not in the periphery of MG patients. CD31, a marker lost with excessive immunoreactivity, was significantly reduced in thymic but not blood resting Treg. These results suggest that an altered thymic environment may explain Treg differences between MG patients and controls. Since thymic epithelial cells (TECs) play a major role in the generation of Treg, we co-cultured healthy thymic CD4 + T cells with control or MG TECs and tested their suppressive function. Co-culture with MG TECs consistently hampers regulatory activity, as compared with control TECs, suggesting that MG TECs contribute to the immune regulation defects of MG CD4 + T cells. MG TECs produced significantly higher thymic stromal lymphopoietin (TSLP) than control TECs, and a neutralizing anti-TSLP antibody partially restored the suppressive capacity of Treg derived from co-cultures with MG TECs, suggesting that TSLP contributed to the defect of thymic Treg in MG patients. Finally, a co-culture of MG CD4 + T cells with control TECs restored numbers and function of MG Treg, demonstrating that a favorable environment could correct the immune regulation defects of T cells in MG. Altogether, our data suggest that the severe defect of thymic Treg is at least partially due to MG TECs that overproduce TSLP. The Treg defects could be corrected by replacing dysfunctional TECs by healthy TECs. These findings highlight the role of the tissue environment on the immune regulation.

CD31 as a Therapeutic Target in Atherosclerosis

The potential of CD31 as a therapeutic target in atherosclerosis has been considered ever since its cloning in the 1990s, but the exact role played by this molecule in the biologic events underlying atherosclerosis has remained controversial, resulting in the stalling of any therapeutic perspective. Due to the supposed cell adhesive properties of CD31, specific monoclonal antibodies and recombinant proteins were regarded as blocking agents because their use prevented the arrival of leukocytes at sites of acute inflammation. However, the observed effect of those compounds likely resulted from the engagement of the immunomodulatory function of CD31 signaling. This was acknowledged only later though, upon the discovery of CD31's 2 intracytoplasmic tyrosine residues called immunoreceptor tyrosine inhibitory motifs. A growing body of evidence currently points at a therapeutic potential for CD31 agonists in atherothrombosis. Clinical observations show that CD31 expression is altered at the surface of leukocytes infiltrating unhealed atherothrombotic lesions and that the physiological immunomodulatory functions of CD31 are lost at the surface of blood leukocytes in patients with acute coronary syndromes. On the contrary, translational studies using candidate therapeutic molecules in laboratory animals have provided encouraging results: synthetic peptides administered to atherosclerotic mice as systemic drugs in the acute phases of atherosclerotic complications favor the healing of wounded arteries, whereas the immobilization of CD31 agonist peptides onto coronary stents implanted in farm pigs favors their peaceful integration within the coronary arterial wall.

Loss of BAP1 expression is associated with an immunosuppressive microenvironment in uveal melanoma, with implications for immunotherapy development

Immunotherapy using immune checkpoint inhibitors (ICIs) induces durable responses in many metastatic cancers. Metastatic uveal melanoma (mUM), typically occurring in the liver, is one of the most refractory tumours to ICIs and has dismal outcomes. Monosomy 3 (M3), polysomy 8q, and BAP1 loss in primary uveal melanoma (pUM) are associated with poor prognoses. The presence of tumour-infiltrating lymphocytes (TILs) within pUM and surrounding mUM - and some evidence of clinical responses to adoptive TIL transfer - strongly suggests that UMs are indeed immunogenic despite their low mutational burden. The mechanisms that suppress TILs in pUM and mUM are unknown. We show that BAP1 loss is correlated with upregulation of several genes associated with suppressive immune responses, some of which build an immune suppressive axis, including HLA-DR, CD38, and CD74. Further, single-cell analysis of pUM by mass cytometry confirmed the expression of these and other markers revealing important functions of infiltrating immune cells in UM, most being regulatory CD8+ T lymphocytes and tumour-associated macrophages (TAMs). Transcriptomic analysis of hepatic mUM revealed similar immune profiles to pUM with BAP1 loss, including the expression of IDO1. At the protein level, we observed TAMs and TILs entrapped within peritumoural fibrotic areas surrounding mUM, with increased expression of IDO1, PD-L1, and β-catenin (CTNNB1), suggesting tumour-driven immune exclusion and hence the immunotherapy resistance. These findings aid the understanding of how the immune response is organised in BAP1 - mUM, which will further enable functional validation of detected biomarkers and the development of focused immunotherapeutic approaches. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Retinal endothelial cell phenotypic modifications during experimental autoimmune uveitis: a transcriptomic approach

BACKGROUND

Blood-retinal barrier cells are known to exhibit a massive phenotypic change during experimental autoimmune uveitis (EAU) development. In an attempt to investigate the mechanisms of blood-retinal barrier (BRB) breakdown at a global level, we studied the gene regulation of total retinal cells and retinal endothelial cells during non-infectious uveitis.

METHODS

Retinal endothelial cells were isolated by flow cytometry either in Tie2-GFP mice (CD31+ CD45- GFP+ cells), or in wild type C57BL/6 mice (CD31+ CD45- endoglin+ cells). EAU was induced in C57BL/6 mice by adoptive transfer of IRBP1-20-specific T cells. Total retinal cells and retinal endothelial cells from naïve and EAU mice were sorted and their gene expression compared by RNA-Seq. Protein expression of selected genes was validated by immunofluorescence on retinal wholemounts and cryosections and by flow cytometry.

RESULTS

Retinal endothelial cell sorting in wild type C57BL/6 mice was validated by comparative transcriptome analysis with retinal endothelial cells sorted from Tie2-GFP mice, which express GFP under the control of the endothelial-specific receptor tyrosine kinase promoter Tie2. RNA-Seq analysis of total retinal cells mainly brought to light upregulation of genes involved in antigen presentation and T cell activation during EAU. Specific transcriptome analysis of retinal endothelial cells allowed us to identify 82 genes modulated in retinal endothelial cells during EAU development. Protein expression of 5 of those genes (serpina3n, lcn2, ackr1, lrg1 and lamc3) was validated at the level of inner BRB cells.

CONCLUSION

Those data not only confirm the involvement of known pathogenic molecules but further provide a list of new candidate genes and pathways possibly implicated in inner BRB breakdown during non-infectious posterior uveitis.

Overexpression of B7-H3 in α-SMA-Positive Fibroblasts Is Associated With Cancer Progression and Survival in Gastric Adenocarcinomas

Background: B7-H3 promotes tumor immune escape and is highly expressed in tumor tissues. Stromal cells in tumors, including fibroblasts, play an important role in this process; however, the role of B7-H3 in tumor fibroblasts has not been fully clarified.

Methods: We examined B7-H3, CD31, and alpha-smooth muscle actin (α-SMA) protein expression in 268 gastric adenocarcinomas (GACs) by immunohistochemistry. The coexpression of B7-H3 with CD31 or α-SMA was examined using immunofluorescence double staining. Cytokine expression from fibroblasts treated with B7-H3 small interfering RNA (siRNA) was analyzed by a Quantitative reverse transcription-polymerase chain reaction (qPCR) and Enzyme-linked immunosorbent assay (ELISA). The transwell tests were conducted to assess the migration and invasion ability of fibroblasts. The overall survival was analyzed by a Kaplan-Meier analysis. Associations between categorical variables were assessed using the Pearson's Chi-square test or Fisher's exact test.

Results: GAC patients with B7-H3 expression showed significantly poorer survival (P = 0.012). The overall survival of the group with high B7-H3 expression was significantly worse than the group with low B7-H3 expression in both tumor cells and in stromal cells (P = 0.007 and P = 0.048, respectively). B7-H3 expression correlated with many clinicopathological data, including tumor stage, tumor depth, lymph node involvement, and survival. Immunofluorescence staining showed that B7-H3 was expressed in tumor cells and α-SMA-positive fibroblasts. Remarkably, high expression of α-SMA was associated with a poor prognosis (P = 0.007), and the prognoses of patients with high stromal expression of B7-H3 and α-SMA were significantly worse than that of other combination types (P = 0.001). Additionally, the absence of B7-H3 led to decreased secretion of cytokines, such as interleukin (IL)-6 and vascular endothelial growth factor (VEGF), as well as a decline in migration and invasion ability in cancer-associated fibroblasts (CAFs).

Conclusions: Patients with high B7-H3 expression either in tumor cells or in stromal cells had significantly poorer overall survival. Stromal B7-H3 expression was mostly detected in α-SMA-positive CAFs. GAC patients with both stromal B7-H3-high and α-SMA-high expression had significantly poorer overall survival, suggesting that stromal B7-H3 and α-SMA expression status can serve as an indicator of poor prognosis for GAC patients.

Immune cell extracellular vesicles and their mitochondrial content decline with ageing

Background

Although the mechanisms of action are not fully understood, extracellular vesicles (EVs) have emerged as key indicators and effectors of immune function. Characterizing circulating EVs associated with stem and immune cells across the lifespan of healthy individuals could aid an understanding of immunosenescence, a process of age-related decline of cells in both adaptive and innate immune systems.

Results

Using high resolution multicolor flow cytometry, we identified three major subsets of EVs of varying sizes in healthy control (HC) plasma. Multiple plasma EVs associated with immune cells declined with ageing in HCs. In addition, we observed age-associated declines of respiring mitochondria cargo in EVs of several types of immune cells, suggesting that these parent cells may experience a decline in mitophagy or a mitochondrial dysfunction-induced immunosenescence. By contrast, the number of CD34⁺ hematopoietic stem cell-associated EVs were high and carried respiring mitochondria, which did not decline with age.

Conclusion

As demonstrated here, multicolor flow cytometry simultaneously measures plasma EV size, surface markers and cargo that reflect biological processes of specific cell types. The distinct surface markers and cytokine cargo of plasma EVs suggest that they may carry different bio-messages and originate by different biogenesis pathways.

Cleaved CD31 as a target for in vivo molecular imaging of inflammation

There is a need for new targets to specifically localize inflammatory foci, usable in a wide range of organs. Here, we hypothesized that the cleaved molecular form of CD31 is a suitable target for molecular imaging of inflammation. We evaluated a bioconjugate of D-P8RI, a synthetic peptide that binds all cells with cleaved CD31, in an experimental rat model of sterile acute inflammation. Male Wistar rats were injected with turpentine oil into the gastrocnemius muscle two days before ^99mTc-HYNIC-D-P8RI (or its analogue with L-Proline) SPECT/CT or [¹⁸F]FDG PET/MRI. Biodistribution, stability study, histology, imaging and autoradiography of ^99mTc-HYNIC-D-P8RI were further performed. Biodistribution studies revealed rapid elimination of ^99mTc-HYNIC-D-P8RI through renal excretion with almost no uptake from most organs and excellent in vitro and in vivo stability were observed. SPECT/CT imaging showed a significant higher ^99mTc-HYNIC-D-P8RI uptake compared with its analogue with L-Proline (negative control) and no significant difference compared with [¹⁸F]FDG (positive control). Moreover, autoradiography and histology revealed a co-localization between ^99mTc-HYNIC-D-P8RI uptake and inflammatory cell infiltration. ^99mTc-HYNIC-D-P8RI constitutes a new tool for the detection and localization of inflammatory sites. Our work suggests that targeting cleaved CD31 is an attractive strategy for the specific in vivo imaging of inflammatory processes.