Teresa Kennedy-Lydon

An Intact Kidney Slice Model to Investigate Vasa Recta Properties and Function in situ

Background: Medullary blood flow is via vasa recta capillaries, which possess contractile pericytes. In vitro studies using isolated descending vasa recta show that pericytes can constrict/dilate descending vasa recta when vasoactive substances are present. We describe a live kidney slice model in which pericyte-mediated vasa recta constriction/dilation can be visualized in situ. Methods: Confocal microscopy was used to image calcein, propidium iodide and Hoechst labelling in ‘live’ kidney slices, to determine tubular and vascular cell viability and morphology. DIC video-imaging of live kidney slices was employed to investigate pericyte-mediated real-time changes in vasa recta diameter. Results: Pericytes were identified on vasa recta and their morphology and density were characterized in the medulla. Pericyte-mediated changes in vasa recta diameter (10–30%) were evoked in response to bath application of vasoactive agents (norepinephrine, endothelin-1, angiotensin-II and prostaglandin E2) or by manipulating endogenous vasoactive signalling pathways (using tyramine, L-NAME, a cyclo-oxygenase (COX-1) inhibitor indomethacin, and ATP release). Conclusions: The live kidney slice model is a valid complementary technique for investigating vasa recta function in situ and the role of pericytes as regulators of vasa recta diameter. This technique may also be useful in exploring the role of tubulovascular crosstalk in regulation of medullary blood flow.

Sympathetic nerve-derived ATP regulates renal medullary vasa recta diameter via pericyte cells: a role for regulating medullary blood flow?

Pericyte cells are now known to be a novel locus of blood flow control, being able to regulate capillary diameter via their unique morphology and expression of contractile proteins. We have previously shown that exogenous ATP causes constriction of vasa recta via renal pericytes, acting at a variety of membrane bound P2 receptors on descending vasa recta (DVR), and therefore may be able to regulate medullary blood flow (MBF). Regulation of MBF is essential for appropriate urine concentration and providing essential oxygen and nutrients to this region of high, and variable, metabolic demand. Various sources of endogenous ATP have been proposed, including from epithelial, endothelial, and red blood cells in response to stimuli such as mechanical stimulation, local acidosis, hypoxia, and exposure to various hormones. Extensive sympathetic innervation of the nephron has previously been shown, however the innervation reported has focused around the proximal and distal tubules, and ascending loop of Henle. We hypothesize that sympathetic nerves are an additional source of ATP acting at renal pericytes and therefore regulate MBF. Using a rat live kidney slice model in combination with video imaging and confocal microscopy techniques we firstly show sympathetic nerves in close proximity to vasa recta pericytes in both the outer and inner medulla. Secondly, we demonstrate pharmacological stimulation of sympathetic nerves in situ (by tyramine) evokes pericyte-mediated vasoconstriction of vasa recta capillaries; inhibited by the application of the P2 receptor antagonist suramin. Lastly, tyramine-evoked vasoconstriction of vasa recta by pericytes is significantly less than ATP-evoked vasoconstriction. Sympathetic innervation may provide an additional level of functional regulation in the renal medulla that is highly localized. It now needs to be determined under which physiological/pathophysiological circumstances that sympathetic innervation of renal pericytes is important.

Cardiac regeneration: epicardial mediated repair

The hearts of lower vertebrates such as fish and salamanders display scarless regeneration following injury, although this feature is lost in adult mammals. The remarkable capacity of the neonatal mammalian heart to regenerate suggests that the underlying machinery required for the regenerative process is evolutionarily retained. Recent studies highlight the epicardial covering of the heart as an important source of the signalling factors required for the repair process. The developing epicardium is also a major source of cardiac fibroblasts, smooth muscle, endothelial cells and stem cells. Here, we examine animal models that are capable of scarless regeneration, the role of the epicardium as a source of cells, signalling mechanisms implicated in the regenerative process and how these mechanisms influence cardiomyocyte proliferation. We also discuss recent advances in cardiac stem cell research and potential therapeutic targets arising from these studies.

Insulin-like growth factor-1 induces regulatory T cell-mediated suppression of allergic contact dermatitis in mice

Allergic contact dermatitis (ACD) is triggered by an aberrant hyperinflammatory immune response to innocuous chemical compounds and ranks as the world’s most prevalent occupational skin condition. Although a variety of immune effector cells are activated during ACD, regulatory T (Treg) cells are crucial in controlling the resulting inflammation. Insulin-like growth factor-1 (IGF-1) regulates cell proliferation and differentiation and accelerates wound healing and regeneration in several organs including the skin. Recently IGF-1 has also been implicated in protection from autoimmune inflammation by expansion of Treg cells. Here, we demonstrate that ectopic expression of IGF-1 in mouse skin suppresses ACD in a Treg cell-specific manner, increasing the number of Foxp3+ Treg cells in the affected area and stimulating lymphocyte production of the anti-inflammatory cytokine interleukin 10. Similar therapeutic effects can be achieved with systemic or topical delivery of IGF-1, implicating this growth factor as a promising new therapeutic option for the treatment of ACD.

Cardiac regeneration: All work and no repair?

Cardiac development may contribute to loss of regenerative capacity in the adult mammalian heart. Structural changes in the developing heart may influence the limited regenerative capacity of the adult heart. We examine how the workload exerted on the adult mammalian heart may limit regenerative capability and discuss recent therapies that demonstrate beneficial effects through unloading the heart.

Nonsteroidal anti-inflammatory drugs alter vasa recta diameter via pericytes

We have previously shown that vasa recta pericytes are known to dilate vasa recta capillaries in the presence of PGE2 and contract vasa recta capillaries when endogenous production of PGE2 is inhibited by the nonselective nonsteroidal anti-inflammatory drug (NSAID) indomethacin. In the present study, we used a live rat kidney slice model to build on these initial observations and provide novel data that demonstrate that nonselective, cyclooxygenase-1-selective, and cyclooxygenase -2-selective NSAIDs act via medullary pericytes to elicit a reduction of vasa recta diameter. Real-time images of in situ vasa recta were recorded, and vasa recta diameters at pericyte and nonpericyte sites were measured offline. PGE2 and epoprostenol (a prostacyclin analog) evoked dilation of vasa recta specifically at pericyte sites, and PGE2 significantly attenuated pericyte-mediated constriction of vasa recta evoked by both endothelin-1 and ANG II. NSAIDs (indomethacin > SC-560 > celecoxib > meloxicam) evoked significantly greater constriction of vasa recta capillaries at pericyte sites than at nonpericyte sites, and indomethacin significantly attenuated the pericyte-mediated vasodilation of vasa recta evoked by PGE2, epoprostenol, bradykinin, and S-nitroso-N-acetyl-l-penicillamine. Moreover, a reduction in PGE2 was measured using an enzyme immune assay after superfusion of kidney slices with indomethacin. In addition, immunohistochemical techniques were used to demonstrate the population of EP receptors in the medulla. Collectively, these data demonstrate that pericytes are sensitive to changes in PGE2 concentration and may serve as the primary mechanism underlying NSAID-associated renal injury and/or further compound-associated tubular damage.

Immune Functions and Properties of Resident Cells in the Heart and Cardiovascular System: Pericytes

This chapter provides an introduction to pericyte physiology. Pericytes are smooth muscle-like cells that wrap around vessels and arterioles. Here, we discuss their structure, function, contractility and interaction with other cells including immune cells and finally their role in pathological processes. Additionally, we discuss recent studies describing pericyte populations in the heart and their potential as targets for future cardiac therapeutic interventions.

The Immunology of Cardiovascular Homeostasis and Pathology

The first € price and the £ and

Inhibition of medullary prostaglandin E2 (PGE2) by non-steroidal anti-inflammatory drugs (NSAIDs) adversely affects medullary blood flow

price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for Germany, the €(A) includes 10% for Austria. Prices indicated with ** include VAT for electronic products; 19% for Germany, 20% for Austria. All prices exclusive of carriage charges. Prices and other details are subject to change without notice. All errors and omissions excepted. S. Sattler, T. Kennedy-Lydon (Eds.) The Immunology of Cardiovascular Homeostasis and Pathology