Evaluation of transporter-mediated hepatobiliary transport of newly developed ¹⁸F-labeled pitavastatin derivative, PTV-F1, in rats by PET imaging

Quantitative evaluations of the functions of uptake and efflux transporters directly in vivo is desired to understand an efficient hepatobiliary transport of substrate drugs. Pitavastatin is a substrate of organic anion transporting polypeptides (OATPs) and canalicular efflux transporters; thus, it can be a suitable probe for positron-emission tomography (PET) imaging of hepatic transporter functions. To characterize the performance of [¹⁸F]PTV-F1, an analogue of pitavastatin, we investigated the impact of rifampicin (a typical OATP inhibitor) coadministration or Bcrp (breast cancer resistance protein) knockout on [¹⁸F]PTV-F1 hepatic uptake and efflux in rats by PET imaging. After intravenous administration, [¹⁸F]PTV-F1 selectively accumulated in the liver, and the radioactivity detected in plasma, liver, and bile mainly derived from the parent PTV-F1 during the PET study (∼40 min). Coadministration of rifampicin largely decreased the hepatic uptake of [¹⁸F]PTV-F1 by 73%. Because of its lower clearance in rats, [¹⁸F]PTV-F1 is more sensitive for monitoring changes in hepatic OATP1B function that other previously reported OATP1B PET probes. Rifampicin coadministration also significantly decreased the biliary excretion of radioactivity by 65%. Bcrp knockout did not show a significant impact on its biliary excretion.[¹⁸F]PTV-F1 enables quantitative analysis of the hepatobiliary transport system for organic anions

The synthesis of [18F]pitavastatin as a tracer for hOATP using the Suzuki coupling.

Fluorine-18 labeled radiotracers, such as [(18)F]fluorodeoxyglucose, can be used as practical diagnostic agents in positron emission tomography (PET). Furthermore, the properties of pharmaceuticals can be enhanced significantly by the introduction of fluorine groups into their original structures, and significant progress has been made during the last three decades towards the development of practical procedures for the introduction of fluorine. The replacement of the fluorine atoms present in pharmaceuticals with radioactive (18)F atoms is a rational approach for designing novel PET tracers. As a fluorine-containing pharmaceutical agent, pitavastatin has attracted considerable interest from researchers working in the life sciences because it can act as an antihyperlipidemic agent as well as a substrate for hepatic organic anion transporting polypeptides (hOATP). With this in mind, it was envisaged that [(18)F]pitavastatin would be used as an excellent imaging agent for hOATP, which prompted us to investigate the synthesis of this agent. Herein, we report a practical method for the synthesis of [(18)F]pitavastatin by the Suzuki coupling reaction of p-iodofluorobenzene and a quinoline boronate derivative, with the desired product being formed in a radiochemical yield of 12 ± 3% (decay corrected from [(18)F]fluoride ions, n = 3)

Sutureless microvascular anastomosis assisted by an expandable shape-memory alloy stent.

Vascular anastomosis is the highlight of cardiovascular, transplant, and reconstructive surgery, which has long been performed by hand using a needle and suture. However, anastomotic thrombosis occurs in approximately 0.5-10% of cases, which can cause serious complications. To improve the surgical outcomes, attempts to develop devices for vascular anastomosis have been made, but they have had limitations in handling, cost, patency rate, and strength at the anastomotic site. Recently, indwelling metal stents have been greatly improved with precise laser metalwork through programming technology. In the present study, we designed a bare metal stent, Microstent, that was constructed by laser machining of a shape-memory alloy, NiTi. An end-to-end microvascular anastomosis was performed in SD rats by placing the Microstent at the anastomotic site and gluing the junction. The operation time for the anastomosis was significantly shortened using Microstent. Thrombus formation, patency rate, and blood vessel strength in the Microstent anastomosis were superior or comparable to hand-sewn anastomosis. The results demonstrated the safety and effectiveness, as well as the operability, of the new method, suggesting its great benefit for surgeons by simplifying the technique for microvascular anastomosis

Evaluation of transporter-mediated hepatobiliary transport of newly developed 18F-labeled pitavastatin derivative, PTV-F1, in rats by PET imaging

Quantitative evaluations of the functions of uptake and efflux transporters directly in vivo is desired to understand an efficient hepatobiliary transport of substrate drugs. Pitavastatin is a substrate of organic anion transporting polypeptides (OATPs) and canalicular efflux transporters; thus, it can be a suitable probe for positron-emission tomography (PET) imaging of hepatic transporter functions. To characterize the performance of [18F]PTV-F1, an analogue of pitavastatin, we investigated the impact of rifampicin (a typical OATP inhibitor) coadministration or Bcrp (breast cancer resistance protein) knockout on [18F]PTV-F1 hepatic uptake and efflux in rats by PET imaging. After intravenous administration, [18F]PTV-F1 selectively accumulated in the liver, and the radioactivity detected in plasma, liver, and bile mainly derived from the parent PTV-F1 during the PET study (∼40 min). Coadministration of rifampicin largely decreased the hepatic uptake of [18F]PTV-F1 by 73%. Because of its lower clearance in rats, [18F]PTV-F1 is more sensitive for monitoring changes in hepatic OATP1B function that other previously reported OATP1B PET probes. Rifampicin coadministration also significantly decreased the biliary excretion of radioactivity by 65%. Bcrp knockout did not show a significant impact on its biliary excretion.[18F]PTV-F1 enables quantitative analysis of the hepatobiliary transport system for organic anions

Histological examination of anastomosed vessels.

<p>(<b>A</b>) A cross-section of a hand-sewn rat infrarenal aorta at 26 weeks. Low-magnification view (H&E stain). High-magnification view (elastic Van Gieson stain) shows hyperplasia of the tunica media. Black bar, 1 mm; yellow bar, 250 μm. (<b>B</b>) A cross-section of a Microstent-anastomosed rat infrarenal aorta at 26 weeks. High-magnification view shows neointimal proliferation limited to the region around the stent branches. (<b>C</b>) A SEM view of the lumen of a hand-sewn vessel at 26 weeks showing thread exposure into the lumen. Bar, 200 μm. (<b>D</b>) A SEM view of the lumen of a Microstent-anastomosed vessel at 26 weeks. The vessel is half-cut. All branches of the Microstent are covered with endothelium. Left bar, 500 μm; right bars, 100 μm.</p

Stent-assisted sutureless microvascular anastomoses.

<p>(<b>A</b>) Showing the traditional microvascular anastomosis using a needle and thread. Multiple interrupted sutures, usually 6–10, are required for anastomosis. The key to success is to maximize the vessel lumen (asterisk) by coaptation of both ends of the intima (arrowhead) without a gap and placing sutures at even intervals. (<b>B</b>) The Microstent system to perform sutureless microvascular anastomosis. The Microstent compressed by a 7–0 nylon thread squeezed in the holder is inserted into each side of the vessel ends (top). After both ends are coapted (center), the 7–0 nylon thread is cut to loosen the Microstent, and the holder is removed. The Microstent automatically expands to maintain the lumen without a gap (bottom). Finally, cyanoacrylate glue (green) is applied around the junction of the vessels (See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181520#pone.0181520.s002" target="_blank">S1 Movie</a>). (<b>C</b>) The approximate diameter (<i>R</i>) of the compressed Microstent is determined by the number of branches (<i>n</i>), tube thickness (<i>d</i>), and branch width (<b><i>w</i></b>). When the Microstent is compressed to the maximum extent, the branches touch each other. (<b>D</b>) NiTi stent (Microstent) fully expanded (2 x 4 mm) (left) and a stent compressed by a 7–0 nylon thread (right). Note the continuously arranged branches in a Z-shape at the center in order to be compressed uniformly end to end. Bar: 1 mm. (<b>E</b>) Scanning electron microscope image of the Microstent before and after electrolytic polishing (ELP), Bars: 100 μm. (<b>F</b>) Intraoperative view of anastomosis of rat aorta using Microstent. The anastomotic site was sealed by cyanoacrylate (arrow). Bar: 1 mm.</p

Ex vivo analyses of wall compliance and mechanical strength of Microstent anastomosed vessels.

<p>(<b>A</b>) The anastomosed vessels are connected to an ex vivo cardiac pump system. The lines demonstrate the average change in blood pressure with the blood flow change of the vessel specimen at 2 weeks, 7 weeks, and 26 weeks in each group (n = 6). (<b>B</b>) The representative data of the pressure changes of the Microstent-anastomosed vessel under cardiac pump pulsation. Both groups could withstand the highest arterial pressure of over 400 mmHg (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181520#pone.0181520.s004" target="_blank">S3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181520#pone.0181520.s005" target="_blank">S4</a> Movies). (<b>C</b>) Photograph of Microstent-anastomosed vessels under different arterial pressures: 150, 200, 300, and 400 mmHg. (<b>D</b>) The representative tensile curve of the anastomosed vessel. The vessels are pulled under physiological pulsation and blood pressure (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181520#pone.0181520.s006" target="_blank">S5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181520#pone.0181520.s007" target="_blank">S6</a> Movies). (<b>E</b>) The average tensile strength of hand-sewn and Microstent-anastomosed vessels at 2, 7, and 26 weeks. There is a significant difference between the two groups at 26 weeks. <i>p</i> values were determined by Student’s <i>t</i>-test. *<i>p < 0</i>.<i>05</i>.</p