Microvascular homeostasis is strictly regulated, requiring close interaction between endothelial cells and pericytes. Here, we aimed to improve our understanding of how microvascular crosstalk affects pericytes. Human-derived pericytes, cultured in absence, or presence of human endothelial cells, were studied by RNA sequencing. Compared with mono-cultured pericytes, a total of 6704 genes were differentially expressed in co-cultured pericytes. Direct endothelial contact induced transcriptome profiles associated with pericyte maturation, suppression of extracellular matrix production, proliferation, and morphological adaptation. In vitro studies confirmed enhanced pericyte proliferation mediated by endothelial-derived PDGFB and pericyte-derived HB-EGF and FGF2. Endothelial-induced PLXNA2 and ACTR3 upregulation also triggered pericyte morphological adaptation. Pathway analysis predicted a key role for TGFβ signaling in endothelial-induced pericyte differentiation, whereas the effect of signaling via gap- and adherens junctions was limited. We demonstrate that endothelial cells have a major impact on the transcriptional profile of pericytes, regulating endothelial-induced maturation, proliferation, and suppression of ECM production.

are combined, there are concerns regarding delays to institution of liver cold preservation. The aim of this study was to develop a combined DCD heart and liver retrieval protocol in a pig model with subsequent normothermic machine perfusion (NMP) of both organs to mitigate warm ischemic damage. Methods: Pigs (n= 12; 60-70 kg) were anesthetised. Baseline observations were recorded. After sternotomy, and laparotomy, ventilatory support was withdrawn to mimic DCD conditions. Death was defined as equalisation of central venous and mean arterial pressures. After a 5-minute standoff period, 1.5-2 L blood was collected from a right atrial cannula then a cardiac preservation flush (4°C) commenced via the proximal ascending aorta. The inferior vena cava was cut to vent the organs. The thoracic cavity was kept cold with saline ice slush. The heart was explanted and prepared on back-table for NMP. Liver preservation was begun immediately after blood collection by cold preservation solution flush via the infra-renal aorta and portal vein. The hepatic artery, portal vein and common bile duct were transected, and the liver explanted for back-table NMP preparation. Results: Warm ischaemic time (WIT) and back-table time (BTT) was 21 + 5 and 29 + 6 min for the heart; 20 + 6 (commencement of flush) and 33 + 19 min for the liver. The average blood volume collected was 1.6 L: 1:1 dilution with Krebs resulted in significant hemodilution (from 23 + 5% to 15 + 6%) and hypocalcemia (1.30 + 0.15 to 0.64 + 0.32 mM). This resulted in sub-optimal cardiac contractile recovery despite a favourable lactate profile. Liver enzyme release, bile production, and lactate and pH profiles were favourable during the first 4-6 hours of NMP but deteriorated thereafter. Conclusion: Heart and liver retrieval under standard DCD protocol is possible without excessively extending the WIT for either organ. However, there is insufficient donor blood to support NMP of both organs.

Background: Recent studies emphasize a correlation of increased FGF23 with the pathogenesis of heart diseases. Although it is widely assumed that the bone and not the heart is the major source of FGF23 we previously demonstrated that oncostatin M (OSM) activated cardiomyocytes strongly secrete FGF23. This phosphatonin can be released as intact molecule (iFGF23) as well as C-terminal (cFGF23) and N-terminal (nFGF23) fragments. Since cleavage does not only inactivate iFGF23 but might also exert antagonizing activity we wanted to determine which form is secreted by cardiomyocytes. Methods: Adult cultured cardiomyocytes were stimulated with OSM or albumin as control. Supernatant and cell lysate were analyzed by Western blot (WB) and specific ELISAs against cFGF23 as well as iFGF23. Expression of FGF23 in cardiomyocytes of 6 patients with coronary heart diseases (CHD) was analyzed by confocal microscopy because OSM signaling cascades are activated after myocardial infarction. Results: WB analysis identified cFGF23 as well as nFGF23 while iFGF23 was hardly detectable in the supernatant of OSM-stimulated cardiomyocytes. Analysis of the supernatant by ELISAs revealed that less than 3% of this secreted phosphatonin was intact. In patients with CHD the number of FGF23 positive cardiomyocytes increased from 0.2% in the remote zone to 4.4% in the border zone. Conclusions: The expression and release of FGF23 by cardiomyocytes indicate local as well as systemic functions. The determination of the ratio of iFGF23/cFGF23 will be essential to understand the functional role of this growth factor in patients with cardiac diseases.

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Background: Atherosclerosis is a complex inflammatory vascular disease characterized by lipid and immune cells accumulation in the vessel wall, leading to lumen narrowing. Although several 3D in vitro microfluidic systems were previously described, a realistic reconstruction of the in vivo human atherosclerotic environment requires co-culture of different cell types arranged in atherosclerotic vessel-like structures with exposure to flow and circulating cells, creating challenges for disease modelling. In this study we developed a 3D tubular microfluidic model with quadruple coculture of human aortic smooth muscle cells (hAoSMCs), human umbilical cord vein endothelial cells (HUVECs) and foam cells to re-create a complex human atherosclerotic vessel in vitro to study the effect of flow and circulating immune cells. Methods & Results: Our new co-culture protocol with BFP-labelled hAoSMCs, GFP-labelled HUVECs and THP-1 macrophages-derived, Dil-labelled Oxidized Low-Density Lipoprotein (Dil-Ox-LDL) foam cells in a fibrinogen-collagen-I based 3D extracellular matrix (ECM) resulted in vessels with an early lesion morphology, showing a layered vessel-like composition with an endothelium and media, with foam cells accumulating in the sub-endothelial space. Perfusion for 24 hours of atherosclerotic and "healthy" vessels (BFP hAoSMCs and GFP HUVECs without foam cells) showed that the layered wall composition remained stable. Perfusion with circulating THP-1 monocytes demonstrated cell extravasation into the atherosclerotic vessel wall and recruitment of THP-1 cells to the foam cell core. QPCR analysis revealed increased expression of atherosclerosis markers in the atherosclerotic vessels and adaptation in VSMCs migration to flow and the plaque microenvironment, compared to control vessels. Conclusion: We present a 3D tubular microfluidic model of a complex early atherosclerotic human vessel that can be exposed to flow and circulating THP-1 monocytes to study hemodynamic changes and immune cell recruitment under live confocal imaging. This novel atherosclerosis-on-a-chip model offers a humanized platform for in-depth mechanistic in vitro studies and drug testing.