Atypical Roles of the Chemokine Receptor ACKR3/CXCR7 in Platelet Pathophysiology

The manifold actions of the pro-inflammatory and regenerative chemokine CXCL12/SDF-1α are executed through the canonical GProteinCoupledReceptor CXCR4, and the non-canonical ACKR3/CXCR7. Platelets express CXCR4, ACKR3/CXCR7, and are a vital source of CXCL12/SDF-1α themselves. In recent years, a regulatory impact of the CXCL12-CXCR4-CXCR7 axis on platelet biogenesis, i.e., megakaryopoiesis, thrombotic and thrombo-inflammatory actions have been revealed through experimental and clinical studies. Platelet surface expression of ACKR3/CXCR7 is significantly enhanced following myocardial infarction (MI) in acute coronary syndrome (ACS) patients, and is also associated with improved functional recovery and prognosis. The therapeutic implications of ACKR3/CXCR7 in myocardial regeneration and improved recovery following an ischemic episode, are well documented. Cardiomyocytes, cardiac-fibroblasts, endothelial lining of the blood vessels perfusing the heart, besides infiltrating platelets and monocytes, all express ACKR3/CXCR7. This review recapitulates ligand induced differential trafficking of platelet CXCR4-ACKR3/CXCR7 affecting their surface availability, and in regulating thrombo-inflammatory platelet functions and survival through CXCR4 or ACKR3/CXCR7. It emphasizes the pro-thrombotic influence of CXCL12/SDF-1α exerted through CXCR4, as opposed to the anti-thrombotic impact of ACKR3/CXCR7. Offering an innovative translational perspective, this review also discusses the advantages and challenges of utilizing ACKR3/CXCR7 as a potential anti-thrombotic strategy in platelet-associated cardiovascular disorders, particularly in coronary artery disease (CAD) patients post-MI.

Atypical Roles of the Chemokine Receptor ACKR3/CXCR7 in Platelet Pathophysiology

The manifold actions of the pro-inflammatory and regenerative chemokine CXCL12/SDF-1α are executed through the canonical GProteinCoupledReceptor CXCR4, and the non-canonical ACKR3/CXCR7. Platelets express CXCR4, ACKR3/CXCR7, and are a vital source of CXCL12/SDF-1α themselves. In recent years, a regulatory impact of the CXCL12-CXCR4-CXCR7 axis on platelet biogenesis i.e. megakaryopoiesis, thrombotic and thrombo-inflammatory ac-tions have been revealed through experimental and clinical studies. Platelet surface expression of ACKR3/CXCR7 is significantly enhanced following myocardial infarction (MI) in acute coro-nary syndrome (ACS) patients, also associated with improved functional recovery and progno-sis. The therapeutic implications of ACKR3/CXCR7 in myocardial regeneration and improved recovery following an ischemic episode, are well documented. Cardiomyocytes, cardi-ac-fibroblasts, endothelial lining of the blood vessels perfusing the heart, besides infiltrating platelets and monocytes, all express ACKR3/CXCR7. This review recapitulates ligand induced differential trafficking of platelet CXCR4-ACKR3/CXCR7 affecting their surface availability, and in regulating thrombo-inflammatory platelet functions and survival through CXCR4 or ACKR3/CXCR7. It emphasizes the pro-thrombotic influence of CXCL12/SDF-1α exerted through CXCR4, as opposed to the anti-thrombotic impact of ACKR3/CXCR7. Offering an innovative translational perspective, this review also discusses the advantages and challenges of utilizing ACKR3/CXCR7 as a potential anti-thrombotic strategy in platelet associated cardiovascular dis-orders, particularly in coronary artery disease (CAD) patients post-MI.

Modulation of cell signalling and sulfation in cardiovascular development and disease

Sulf1/Sulf2 genes are highly expressed during early fetal cardiovascular development but down-regulated during later stages correlating with a number of cell signalling pathways in a positive or a negative manner. Immunocytochemical analysis confirmed SULF1/SULF2 expression not only in endothelial cell lining of blood vessels but also in the developing cardiomyocytes but not in the adult cardiomyocytes despite persisting at reduced levels in the adult endothelial cells. The levels of both SULFs in adult ischemic human hearts and in murine hearts following coronary occlusion increased in endothelial lining of some regional blood vessels but with little or no detection in the cardiomyocytes. Unlike the normal adult heart, the levels of SULF1 and SULF2 were markedly increased in the adult canine right-atrial haemangiosarcoma correlating with increased TGFβ cell signalling. Cell signalling relationship to ischaemia was further confirmed by in vitro hypoxia of HMec1 endothelial cells demonstrating dynamic changes in not only vegf and its receptors but also sulfotransferases and Sulf1 & Sulf2 levels. In vitro hypoxia of HMec1 cells also confirmed earlier up-regulation of TGFβ cell signalling revealed by Smad2, Smad3, ALK5 and TGFβ1 changes and later down-regulation correlating with Sulf1 but not Sulf2 highlighting Sulf1/Sulf2 differences in endothelial cells under hypoxia.

In Situ Microscopy Studies of Infused Megakaryocytes: Implications in Thrombopoiesis

The questions of whether thrombopoiesis - the release of platelets from megakaryocytes - occurs both as megakaryocytes emerge from the intramedullar space or occurs as well in the pulmonary vascular bed remains unanswered. Studies by Lefrançais E, et al, (Nature, 2017) demonstrated by in situ microcopy that perhaps 50% of all platelet release in mice occurs from megakaryocytes released from the marrow and traveled to the lungs where they undergo thrombopoiesis over a 20- to 60-minute time-period. We examined whether CD34+-derived human megakaryocytes infused into immunocompromized NSG mice would also shed platelets in the lungs in a similar fashion. We differentiated CD34+-derived hematopoietic stem-progenitors for 12 days in culture using conditions previously described (Wang Y, et al., Blood 2015). We found that unlike platelet-like-particle (PLP) formation in in vitro cultures of CD34+ hematopoietic progenitor cell (HPC)-derived (CD34+) megakaryocytes, which undergo asynchronous shedding of the PLPs, that over 95% of infused CD34+ megakaryocytes shed their platelets within the first 40 minutes much as has been observed for endogenous murine megakaryocytes. The average number of cytoplasmic extensions per megakaryocytes was ~2.7, again very similar to what was seen with endogenous murine megakaryocytes. In contrast, CD34+ cells grown in culture into megakaryocytes for a shorter period of time of only 7 days, poorly shed any cytoplasmic fragments. We also studied human megakaryocytes grown from immortalized megakaryocyte progenitor cell lines (imMKCLs) from induced pluripotent stem cells (iPSCs) generated by the Eto laboratory and kindly provided by Dr. Koji Eto, Kyoto University). These cells were grown and differentiated into terminal megakaryocytes as described (Nakamura S, Cell Stem Cell, 2014) for 4 days in culture. These cells have been proposed to be useful for large-scale preparation of PLPs in vitro for clinical use in place of donor-derived platelets. The resultant infused human imMKCL-derived megakaryocytes also synchronously shed platelets, but only 50% of the infused cells shed their cytoplasm in contrast to >95% of CD34+ megakaryocytes. Moreover, cytoplasmic extensions were decreased to an average of ~1.1 per megakaryocyte. We had proposed that in vitro-generated megakaryocytes might be directly infused into patients in place of further manipulating the megakaryocytes to release functional platelets in vitro using a bioreactor. However, such megakaryocytes will likely be contaminated with a higher level of HPCs than anticipated from in vitro-prepared platelets, and concern exists that they may lead to unacceptable graft versus host complications. We, therefore, examined whether irradiating megakaryocytes as one strategy to eliminate this concern results in megakaryocytes that are still functional and found that megakaryocytes irradiated with up to 25 Gy retain platelet yield per infused megakaryocytes with the platelets having the same half-life. If irradiated and kept in culture, these megakaryocytes begin to shed platelets and undergo apoptosis notably by 24 hours. We also examined whether the pulmonary bed differs from other vascular beds, and infused CD34+ megakaryocytes both intravenously and intra-arterially in parallel studies and found that following intra-arterial infusion, megakaryocytes were mostly entrapped in various organs, but shed few platelets. Thus, our studies suggest that the pulmonary bed is unique for platelet shedding from entrapped megakaryocytes. Whether this is due to the structural organization of the pulmonary beds, its endothelial lining, its reverse exchange in oxygen, carbon dioxide and pH from other capillary beds or the mechanical forces of inhalation and exhalation that expand and contract the capillary cross-sectional area needs to be examined. Our studies show that infused human megakaryocytes synchronously release platelets over a 40-minute window and can do so even after being irradiated and that this occurs specifically in the lungs not only has potential clinical application, but also raises biological questions about what determines thrombopoiesis-readiness and what are the features of the pulmonary bed that allows this synchronous release. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

The Efficacy of Hydrodilatation for the Prevention of Vasospasm following Microsurgical Anastomosis

Introduction Vasospasm is a major problem following microsurgical reconstruction which can result in the partial or complete loss of the flap tissue. The aim of this study was to investigate the efficiency of hydrodilatation for the prevention of vasospasm. Material and Methods Thirty male Wistar rats were used for this experimental study. Femoral arteries of were exposed, photographed, and transected. In group 1, group 2, and group 3 papaverine solution, hydrodilatation, and minimal mechanical dilatation (control group) was performed, respectively. The anastomosis was completed and the arteries were photographed again 10 minutes after completion of the anastomosis. Following 7-day period samples for transmission electron microscopy (TEM) and light microscopy were obtained. Results The mean vessel diameters prior to transection were 0.43, 0.45, and 0.52 mm in the papaverine, hydrodilatation, and control groups, respectively. The mean vessel diameter 10 minutes following the completion of anastomosis was 0.76, 0.75, and 0.51 mm in the papaverine, hydrodilatation, and control groups, respectively. Median score for papaverine group regarding histological parameters of regular endothelial lining and lumen, neutrophil infiltration, vascular congestion, and edema in tunica adventitia was 2, 3, 2, and 3 positive, respectively. Median score for the papaverine group regarding histological parameters of regular endothelial lining and lumen, neutrophil infiltration, vascular congestion, and edema in tunica adventitia was 3, 3, 3, and 3 positive, respectively. All the histological scores were negative in the control group. The difference between the control group and the experiment groups 1 and 2 was significant regarding all four histological parameters (p < 0.05). Conclusion Hydrodilatation and papaverine application were both effective in preventing vasospasm following microsurgical intervention but papaverine caused slightly less damage to the endothelial lining and less edema in the tunica adventitia when compared with the hydrodilatation. Hydrodilatation group showed a vasodilatory effect that was statistically similar to that of papaverine, which has a proven efficacy.

Small-Diameter Vessels Reconstruction Using Cell Tissue-Engineering Graft Based on the Polycaprolactone

Polycaprolactone (PCL) is widely applied for the construction of small-diameter tissue-engineered vascular grafts (TEGs) due to its biomechanical properties, slow degradation, and good biocompatibility. In the present study the TEG based on a tubular scaffold seeded with smooth muscle aortic cells (SMCs) in a rat abdominal aorta replacement model was tested. Polyester tubular scaffolds were generated by thermally induced phase separation and seeded with rat SMCs. To track the implanted SMCs in vivo, cells were labeled with superparamagnetic iron oxide nanoparticles (SPIONs). Histological evaluation of the migration of autologous endothelial cells (ECs) and formation of the endothelial lining was performed 4, 8, and 12 weeks after graft interposition. TEG demonstrated a high patency rate without any complications at the end of the 12-week period. The migration of ECs into the lumen of the implanted TEG and formation of the cell monolayer were already present at 4 weeks, as confirmed by histological analysis. The architecture of both neointima and neoadventitia were similar to those of the native vessel. SPION-labeled SMCs were detected throughout the TEG, indicating the role of these cells in the endothelization of scaffolds. The SMC-seeded scaffolds demonstrated improved patency and biointegrative properties when compared to the acellular grafts.

Effects of Tamiflu and Adamine on histology and ultrastructure of the liver of albino mice

Background Tamiflu (Oseltamivir) and Adamine (Amantadine HCl) are antiviral drugs which are used for prevention and treatment for influenza. The present study was carried out to evaluate the effect of Tamiflu and Adamine on the liver of adult male albino mice from the histological and ultrastructural points of views. Results Histological examination of liver sections treated with Tamiflu and Adamine included enlargement and congestion of central and hepatic veins in addition to erosion of their endothelial lining cells, cytoplasmic vacuolation of hepatocytes, pyknosis of their nuclei, and dilatation of hepatic sinusoid. The electron microscopic investigation illustrated mitochondrial swelling, fragmented rough endoplasmic reticulum, cytoplasmic vacuolation, the nuclei with irregular envelope and condensed heterochromatin, dilated microvilli in sinusoid, in addition to active Kupffer cells have many lysosomes and filopodia in its membrane. Conclusion The study suggested that both drugs induced histopathological and ultrastructural alterations in hepatic tissue. In conclusion, Tamiflu and Adamine have pathological effects on liver of albino mice (Mus musculus).

A CASE OF INFECTIVE ENDOCARDITIS COMPLICATED BY ACUTE ISCHEMIC STROKE

Infective endocarditis is an infectious and inammatory process involving endothelial lining of heart structures and valves. Cerebrovascular complications (CVCs) frequently occur in patients who are in the active stage of infective endocarditis (IE), and result from cerebral septic embolization of an endocardial vegetation. Acute stroke due to septic emboli is a particularly dreaded complication , with a frequency of 25-35%. Here we present a case of 32 year old male patient, who comes to the ER with high grade fever and palpitations since 9 days. On examination we found hyperdynamic impulse with decrescendo type systolic murmur at mitral area and we decided to do a blood workup and also requested a 2D ECHO. Blood culture and 2D ECHO showed different species of streptococci and mitral regurgitation respectively. Based on the investigations we started the patient on antibiotics, However, on the day 7 of treatment, patient developed slurring of speech and hemiparesis followed by motor aphasia. We sent the patient for brain MRI that showed acute infarct in left central semioval, left corona radiata and left perisylvian region. Acute ischemic stroke is the complication of the infective endocarditis and we started tpAalong with intravenous antibiotics after which he experienced signicant clinical improvement in few days.

CORONARY ARTERY DISEASE (CAD): INTERPLAY OF NUTRITION, SERUM PARAMETERS AND GENETICS

Coronary artery disease (CAD) is a leading cause of death worldwide. The death rate is decreasing in developed countries due to awareness, but the disease burden is increasing in developing countries. Pakistan is a country with high prevalence of CAD. The serum lipids have long been implicated in the development of CAD by the deposition of mainly LDL on endothelial lining resulting in atherosclerosis. Progression to CAD involves environmental as well as genetic factors. The genetic component is due to the contribution from various low to modest effect size variants in many genes. Common variants have been used to construct a genetic risk score (GRS) to calculate the risk of future CAD. In conclusion, lifestyle interventions in concert with the knowledge of genetic predisposition based on family history and use of population data may one day lead to the development of personalized medicine for the treatment and prevention of CAD.

Complement C1s cleaves PfEMP1 at interdomain conserved sites inhibiting Plasmodium falciparum cytoadherence

Cytoadhesion of Plasmodium falciparum-infected erythrocytes (IEs) to the endothelial lining of blood vessels protects parasites from splenic destruction, but also leads to detrimental inflammation and vessel occlusion. Surface display of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesion ligands exposes them to host antibodies and serum proteins. PfEMP1 are important targets of acquired immunity to malaria, and through evolution, the protein family has expanded and diversified to bind a select set of host receptors through antigenically diversified receptor-binding domains. Here, we show that complement component 1s (C1s) in serum cleaves PfEMP1 at semiconserved arginine motifs located at interdomain regions between the receptor-binding domains, rendering the IE incapable of binding the two main PfEMP1 receptors, CD36 and endothelial protein C receptor (EPCR). Bioinformatic analyses of PfEMP1 protein sequences from 15 P. falciparum genomes found the C1s motif was present in most PfEMP1 variants. Prediction of C1s cleavage and loss of binding to endothelial receptors was further corroborated by testing of several different parasite lines. These observations suggest that the parasites have maintained susceptibility for cleavage by the serine protease, C1s, and provides evidence for a complex relationship between the complement system and the P. falciparum cytoadhesion virulence determinant.