An optical coherence microscope for 3-dimensional imaging in developmental biology

An optical coherence microscope (OCM) has been designed and constructed to acquire 3-dimensional images of highly scattering biological tissue. Volume-rendering software is used to enhance 3-D visualization of the data sets. Lateral resolution of the OCM is 5 mm (FWHM), and the depth resolution is 10 mm (FWHM) in tissue. The design trade-offs for a 3-D OCM are discussed, and the fundamental photon noise limitation is measured and compared with theory. A rotating 3-D image of a frog embryo is presented to illustrate the capabilities of the instrument

A multi-center preclinical study of gadoxetate DCE-MRI in rats as a biomarker of drug induced inhibition of liver transporter function.

UNLABELLED: Drug-induced liver injury (DILI) is a leading cause of acute liver failure and transplantation. DILI can be the result of impaired hepatobiliary transporters, with altered bile formation, flow, and subsequent cholestasis. We used gadoxetate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), combined with pharmacokinetic modelling, to measure hepatobiliary transporter function in vivo in rats. The sensitivity and robustness of the method was tested by evaluating the effect of a clinical dose of the antibiotic rifampicin in four different preclinical imaging centers. The mean gadoxetate uptake rate constant for the vehicle groups at all centers was 39.3 +/- 3.4 s-1 (n = 23) and 11.7 +/- 1.3 s-1 (n = 20) for the rifampicin groups. The mean gadoxetate efflux rate constant for the vehicle groups was 1.53 +/- 0.08 s-1 (n = 23) and for the rifampicin treated groups was 0.94 +/- 0.08 s-1 (n = 20). Both the uptake and excretion transporters of gadoxetate were statistically significantly inhibited by the clinical dose of rifampicin at all centers and the size of this treatment group effect was consistent across the centers. Gadoxetate is a clinically approved MRI contrast agent, so this method is readily transferable to the clinic. CONCLUSION: Rate constants of gadoxetate uptake and excretion are sensitive and robust biomarkers to detect early changes in hepatobiliary transporter function in vivo in rats prior to established biomarkers of liver toxicity

Multimodal Microvascular Imaging Reveals that Selective Inhibition of Class I PI3K Is Sufficient to Induce an Antivascular Response

The phosphatidylinositol 3-kinase (PI3K) pathway is a central mediator of vascular endothelial growth factor (VEGF)-driven angiogenesis. The discovery of small molecule inhibitors that selectively target PI3K or PI3K and mammalian target of rapamycin (mTOR) provides an opportunity to pharmacologically determine the contribution of these key signaling nodes in VEGF-A-driven tumor angiogenesis in vivo. This study used an array of microvascular imaging techniques to monitor the antivascular effects of selective class I PI3K, mTOR, or dual PI3K/ mTOR inhibitors in colorectal and prostate cancer xenograft models. Micro-computed tomography (micro-CT) angiography, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), vessel size index (VSI) MRI, and DCE ultrasound (DCE-U/S) were employed to quantitatively evaluate the vascular (structural and physiological) response to these inhibitors. GDC-0980, a dual PI3K/mTOR inhibitor, was found to reduce micro-CT angiography vascular density, while VSI MRI demonstrated a significant reduction in vessel density and an increase in mean vessel size, consistent with a loss of small functional vessels and a substantial antivascular response. DCE-MRI showed that GDC-0980 produces a strong functional response by decreasing the vascular permeability/perfusion-related parameter, Ktrans. Interestingly, comparable antivascular effects were observed for both GDC-980 and GNE-490 (a selective class I PI3K inhibitor). In addition, mTOR-selective inhibitors did not affect vascular density, suggesting that PI3K inhibition is sufficient to generate structural changes, characteristic of a robust antivascular response. This study supports the use of noninvasive microvascular imaging techniques (DCE-MRI, VSI MRI, DCE-U/S) as pharmacodynamic assays to quantitatively measure the activity of PI3K and dual PI3K/mTOR inhibitors in vivo

Mixed model results on <i>k</i>_<i>1</i>, <i>k</i>_<i>2</i>, AUC and maximum RE parameters from multicenter <i>in vivo</i> Study 3.

<p>Mixed model results on <i>k</i>_<i>1</i>, <i>k</i>_<i>2</i>, AUC and maximum RE parameters from multicenter <i>in vivo</i> Study 3.</p

RE time curves from the 4 centers in the multicenter study.

<p>Gadoxetate (25 μmol/kg) DCE-MRI RE curves 60 minutes after IV dosing with vehicle (<i>n</i> = 6 per center) or 10 mg/kg rifampicin (<i>n</i> = 6 per center). Images were acquired at four independent research centers i, ii, iii, and iv. Results are presented as mean +/- SEM.</p

Estimated values for relaxation time and relaxivity at the employed field strengths.

<p>Estimated values for relaxation time and relaxivity at the employed field strengths.</p

Plasma biomarkers of liver injury.

<p>Plasma biomarkers of liver injury 2 hours after treatment with either vehicle (n = 5, dark bars) or 10 mg/kg rifampicin (n = 6, light bars). Routine hepatic enzyme biomarkers aspartate aminotransferase (AST) (A), alanine aminotransferase (ALT) (B) and alkaline phosphatase (ALP) (C) were measured as well as the early biomarker of liver injury miR-122 (D). Total (E) and direct (F) bilirubin were measured as a biomarker of Mrp2 inhibition. Direct bilirubin was measured in plasma samples collected two hours after treatment with rifampicin. Results are presented as mean +/- SEM. Differences between groups were evaluated using Student’s <i>t</i>-test with p<0.5 (*), p<0.01 (**), p<0.001 (***) and p<0.0001 (****).</p

MR images and RE time curves from studies 1 and 2.

<p>Typical vehicle treated and 10 mg/kg rifampicin treated rats pre- and post- injection of gadoxetate (25 μmol/kg) (A); DCE-MRI RE curves after 1 mg/kg (n = 3), 3 mg/kg (n = 3), 6 mg/kg (n = 4) or 20 mg/kg (n = 3) of rifampicin or vehicle (n = 8) dosed IV (B); DCE-MRI RE curves in vehicle treated rats (n = 3) or 15 minutes (n = 2), 30 minutes (n = 2) or 60 minutes (n = 2) after dosing with 10 mg/kg rifampicin (C). Values are presented as mean +/- SEM.</p

Gadoxetate influx parameters in the multicenter study.

<p>Pharmacokinetic parameters describing the impact of rifampicin on gadoxetate uptake (<i>k</i>_<i>1</i>) at each of the four research centers: i, ii, iii, and iv. In each center, 6 animals are vehicle treated (dark circles) while 6 animals are rifampicin treated (open circles). Results are presented as mean +/- SEM.</p