An investigation into the role of pericytes in regulation of vascular morphology and function using murine models of inflammation

PhDLeukocyte recruitment to sites of inflammation is a crucial event in host defense against pathogens and tissue injury. Although there is at present much interest in deciphering the mechanisms of leukocyte transendothelial cell migration, little attention has been paid to the subsequent steps, i.e. leukocyte migration through the pericyte layer and the venular basement membrane. In this context, results from this group previously demonstrated that neutrophils preferentially transmigrate through gaps between adjacent pericytes, regions associated with sites of low matrix protein expression within the vascular basement membrane. The aim of this thesis was to extend these findings by investigating the impact of inflammatory mediators on pericyte morphology and vascular basement membrane deposition using both in vitro and in vivo models. Flow cytometry analysis of pericyte-like C3H/10T1/2 cells and primary lung pericytes revealed the expression of key pro-inflammatory molecules on their surface (including cytokine receptors and adhesion molecules) and the regulation of these molecules upon cytokine stimulation. Using the murine cremaster muscle model it was further demonstrated that key neutrophil chemoattractants (i.e. LTB4, KC, C5a and fMLP) induced neutrophil transmigration that was associated with a change in pericyte morphology (as quantified through enlargement of gaps between adjacent pericytes). These changes in pericyte gap size were neutrophil-dependent and mediated by endogenously generated TNF as demonstrated in neutrophil-depleted mice and TNFR-/- mice, respectively. In addition, TNF appeared to mediate post-inflammatory BM deposition in response to LTB4 and was required for chemoattractant-induced vascular permeability. Hence, the results of the present work have demonstrated the ability of pericytes to respond to both cytokines and chemoattractants, suggesting an active role for pericytes in the regulation of inflammatory responses. In addition, findings provide the first evidence for chemoattractant-induced changes in vascular morphology and barrier functions of venular walls in vivo via the release of endogenous TNF as a secondary mediator, effects that may contribute to the pro-inflammatory properties of these stimuli.British Heart Foundatio

Novel whole blood assay for phenotyping platelet reactivity in mice identifies ICAM-1 as a mediator of platelet-monocyte interaction

British Heart Foundation (PG/12/68/29779 and PG/14/48/30916) and the Wellcome Trust (101604/Z/13/Z to SN and TW, and 098291/Z/12/Z to S.N)

Neutrophils recruited by chemoattractants in vivo induce microvascular plasma protein leakage through secretion of TNF

This work was supported by the British Heart Foundation (FS/09/022/27354 funded the PhD training of M. Finsterbusch), Arthritis Research-UK (19913 to M.-B. Voisin), and The Wellcome Trust (098291/Z/12/Z to S. Nourshargh)

Measuring and interpreting platelet-leukocyte aggregates

Platelets, besides their specialised role in haemostasis and atherothrombosis, actively modulate innate and adaptive immune responses with crucial roles in immune surveillance, inflammation and host defence during infection. An important prerequisite for platelet-mediated changes of immune functions involves direct engagement with different types of leukocytes. Indeed, increased platelet-leukocyte aggregates (PLAs) within the circulation and/or locally at the site of inflammation represent markers of many thrombo-inflammatory diseases, such as cardiovascular diseases, acute lung injury, renal and cerebral inflammation. Therefore, measurement of PLAs could provide an attractive and easily accessible prognostic and/or diagnostic tool for many diseases. To measure PLAs in different (patho-)physiological settings in human and animal models flow cytometric and microscopic approaches have been applied. These techniques represent complementary tools to study different aspects relating to the involvement of leukocyte subtypes and molecules, as well as location of PLAs within tissues, dynamics of their interactions and/or dynamic changes in leukocyte and platelet behaviour. This review summarises various approaches to measure and interpret PLAs and discusses potential experimental factors influencing platelet binding to leukocytes. Furthermore, we summarise insights gained from studies regarding the underlying mechanism of platelet-leukocyte interactions and discuss implications of these interactions in health and disease

Stabilization of Electrospun PAN/Gelatin Nanofiber Mats for Carbonization

Due to their electrical and mechanical properties, carbon nanofibers are of large interest for diverse applications, from batteries to solar cells to filters. They can be produced by electrospinning polyacrylonitrile (PAN), stabilizing the gained nanofiber mats, and afterwards, carbonizing them in inert gas. The electrospun base material and the stabilization process are crucial for the results of the carbonization process, defining the whole fiber morphology. While blending PAN with gelatin to gain highly porous nanofibers has been reported a few times in the literature, no attempts have been made yet to stabilize and carbonize these fibers. This paper reports on the first tests of stabilizing PAN/gelatin nanofibers, depicting the impact of different stabilization temperatures and heating rates on the chemical properties as well as the morphologies of the resulting nanofiber mats. Similar to stabilization of pure PAN, a stabilization temperature of 280°C seems suitable, while the heating rate does not significantly influence the chemical properties. Compared to stabilization of pure PAN nanofiber mats, approximately doubled heating rates can be used for PAN/gelatin blends without creating undesired conglutinations, making this base material more suitable for industrial processes

Effector CD4⁺ T cells recognize intravascular antigen presented by patrolling monocytes

Monocytes constitutively adhere and crawl along the glomerular endothelium and are thought to contribute to glomerulonephritis. Here the authors use multiphoton microscopy to show local antigen presentation by MHCII+ monocytes to T cells in glomerular capillaries of mice