In vivo imaging of molecular targets and their function in endocrinology

Dual effect of aucubin on promoting VEGFR2 mediated angiogenesis and reducing RANKL-induced bone resorption

BACKGROUND

Angiogenesis is regarded as a critical role in bone repair and regeneration, involving in pathological bone disorders such as osteoporosis. Aucubin, an iridoid glycoside primarily derived from Eucommia ulmoides, is reported to inhibit osteoclast activity, enhance bone formation and promote angiogenesis in osteoporosis models. Our study is to further investigate the anti-osteoporosis effect of aucubin in transgenic medaka, and the pro-angiogenic effect of aucubin and its mechanism of action both in vivo and in vitro.

METHODS

The anti-osteoporosis effect of aucubin was confirmed by using RANKL-stimulated bone resorption transgenic medaka. The pro-angiogenic effect of aucubin in vivo was investigated using vascular endothelial growth factor (VEGF) tyrosine kinase inhibitor II (VRI)-induced vascular insufficient transgenic zebrafish model. Furthermore, endothelial cell proliferation, migration, tube formation and the mechanisms were evaluated to identify the pro-angiogenic effect of aucubin in normal and su5416-injured human umbilical vein endothelial cells (HUVECs).

RESULTS

Aucubin decreased the resorption of the mineralized bone matrix and centra degradation in heat-shocked transgenic col10α1:nlGFP/rankl:HSE:CFP medaka. Moreover, aucubin reversed VRI-induced vascular insufficiency in zebrafish through regulating flt1, kdr, kdrl, vegfaa, ang-1, ang-2, tie1 and tie2 mRNA expressions in Tg(fli1a:EGFP)y1 or AB wild type zebrafish. Aucubin promoted cell proliferation by upregulating p-mTOR, p-Src, p-MEK, p-Erk1/2, p-Akt and p-FAK in HUVECs. Furthermore, aucubin exhibited a pro-angiogenic effect on su5416-injured HUVECs by promoting their proliferation, migration, and tube formation through regulating the phosphorylation of VEGFR2, MEK, ERK and the ratio of Bcl2-Bax.

CONCLUSION

Aucubin could reduce bone resorption in RANKL-induced osteoporosis medaka by live imaging. Meanwhile, aucubin exhibited a protective effect in VRI-induced vascular insufficient zebrafish by regulating VEGF-VEGFR and Ang-Tie signaling pathways. Additionally, aucubin promoted the proliferation, migration and tube formation of HUVECs probably by mediating VEGFR2/MEK/ERK, Akt/mTOR and Src/FAK signalling pathways. This study further indicated the dual effect of aucubin on angiogenesis and osteogenesis which may be beneficial to its treatment of osteoporosis.

Feasibility of MRI and selection of adequate region of interest for longitudinal studies of growth and fatness in swine models of obesity

PURPOSES

To determine the feasibility of MRI for imaging subcutaneous and visceral adiposity in longitudinal studies in obese swine models (Iberian pig). To establish the anatomical regions of interest (ROIs) and measurement points (MPs) adequate for their evaluation through analyses on the inter-individual variability and over-time reproducibility and through the assessment of their reliability and validity by comparison with in vivo and ex vivo zoometric data.

MATERIAL AND METHODS

Five male and five female pigs were used from four (live weight around 48 kg and back-fat depth around 18 mm) to eight months old (live weight 134 kg and back-fat depth around 48 mm). MRI was carried out with a Panorama 0.23T scanner (Philips Medical Systems, Best, Netherlands), using a body/spine XL coil.

RESULTS

The ROIs of election for visualization of subcutaneous data are located from the cranial margin of left diaphragmatic crura to the lumbar vertebrae L3. Visceral adiposity may be equally evaluated from the vertebrae L1 to L3.

CONCLUSIONS

MRI allows the evaluation of subcutaneous and visceral fatness in a single acquisition, which improves animal welfare and time- and cost-efficiency and provides an accurate, consistent and repeatable procedure for sequential studies of adiposity in obese swine.

Radiolabeled peptides: valuable tools for the detection and treatment of cancer

Human cancer cells overexpress many peptide receptors as molecular targets. Radiolabeled peptides that bind with high affinity and specificity to the receptors on tumor cells hold great potential for both diagnostic imaging and targeted radionuclide therapy. The advantage of solid-phase peptide synthesis, the availability of different chelating agents and prosthetic groups and bioconjugation techniques permit the facile preparation of a wide variety of peptide-based targeting molecules with diverse biological and tumor targeting properties. Some of these peptides, including somatostatin, bombesin, vasoactive intestinal peptide, gastrin, neurotensin, exendin and RGD are currently under investigation. It is anticipated that in the near future many of these peptides may find applications in nuclear oncology. This article presents recent developments in the field of small peptides, and their applications in the diagnosis and treatment of cancer.

Molecular Imaging Probe Development using Microfluidics

In this manuscript, we review the latest advancement of microfluidics in molecular imaging probe development. Due to increasing needs for medical imaging, high demand for many types of molecular imaging probes will have to be met by exploiting novel chemistry/radiochemistry and engineering technologies to improve the production and development of suitable probes. The microfluidic-based probe synthesis is currently attracting a great deal of interest because of their potential to deliver many advantages over conventional systems. Numerous chemical reactions have been successfully performed in micro-reactors and the results convincingly demonstrate with great benefits to aid synthetic procedures, such as purer products, higher yields, shorter reaction times compared to the corresponding batch/macroscale reactions, and more benign reaction conditions. Several 'proof-of-principle' examples of molecular imaging probe syntheses using microfluidics, along with basics of device architecture and operation, and their potential limitations are discussed here.

Evaluation of [¹²³I]-CLINDE as a potent SPECT radiotracer to assess the degree of astroglia activation in cuprizone-induced neuroinflammation

PURPOSE

The purpose of this study was to assess the feasibility and sensitivity of the high-affinity translocator protein (TSPO) ligand [(123)I]-CLINDE in imaging TSPO changes in vivo and characterise and compare astroglial and TSPO changes in the cuprizone model of demyelination and remyelination in C57BL/6 mice.

METHODS

C57BL/6 mice were fed with cuprizone for 4 weeks to induce demyelination followed by 2-4 weeks of standard diet (remyelination). Groups of mice were followed by in vivo single photon emission computed tomography (SPECT)/CT imaging using [(123)I]-CLINDE and uptake correlated with biodistribution, autoradiography, immunohistochemistry, immunofluorescence and real-time polymerase chain reaction (RT-PCR).

RESULTS

The uptake of [(123)I]-CLINDE in the brain as measured by SPECT imaging over the course of treatment reflects the extent of the physiological response, with significant increases observed during demyelination followed by a decrease in uptake during remyelination. This was confirmed by autoradiography and biodistribution studies. A positive correlation between TSPO expression and astrogliosis was found and both activated astrocytes and microglial cells expressed TSPO. [(123)I]-CLINDE uptake reflects astrogliosis in brain structures such as corpus callosum, caudate putamen, medium septum and olfactory tubercle as confirmed by both in vitro and in vivo results.

CONCLUSION

The dynamics in the cuprizone-induced astroglial and TSPO changes, observed by SPECT imaging, were confirmed by immunofluorescence, RT-PCR and autoradiography. The highly specific TSPO radioiodinated ligand CLINDE can be used as an in vivo marker for early detection and monitoring of a variety of neuropathological conditions using noninvasive brain imaging techniques.

Comparison of human optimized bacterial luciferase, firefly luciferase, and green fluorescent protein for continuous imaging of cell culture and animal models

Bioluminescent and fluorescent reporter systems have enabled the rapid and continued growth of the optical imaging field over the last two decades. Of particular interest has been noninvasive signal detection from mammalian tissues under both cell culture and whole animal settings. Here we report on the advantages and limitations of imaging using a recently introduced bacterial luciferase (lux) reporter system engineered for increased bioluminescent expression in the mammalian cellular environment. Comparison with the bioluminescent firefly luciferase (Luc) system and green fluorescent protein system under cell culture conditions demonstrated a reduced average radiance, but maintained a more constant level of bioluminescent output without the need for substrate addition or exogenous excitation to elicit the production of signal. Comparison with the Luc system following subcutaneous and intraperitoneal injection into nude mice hosts demonstrated the ability to obtain similar detection patterns with in vitro experiments at cell population sizes above 2.5 × 10(4) cells but at the cost of increasing overall image integration time.

Combined Cerenkov luminescence and nuclear imaging of radioiodine in the thyroid gland and thyroid cancer cells expressing sodium iodide symporter: initial feasibility study

Radioiodine (RI) such as (131)I or (124)I, can generate luminescent emission and be detected with an optical imaging (OI) device. To evaluate the possibility of a novel Cerenkov luminescence imaging (CLI) for application in thyroid research, we performed feasibility studies of CLI by RI in the thyroid gland and human anaplastic thyroid carcinoma cells expressing sodium iodide symporter gene (ARO-NIS). For in vitro study, FRTL-5 and ARO-NIS were incubated with RI, and the luminometric and CLI intensity was measured with luminometer and OI device. Luminescence intensity was compared with the radioactivity measured with γ-counter. In vivo CLI of the thyroid gland was performed in mice after intravenous injection of RI with and without thyroid blocking. Mice were implanted with ARO-NIS subcutaneously, and CLI was performed with injection of (124)I. Small animal PET or γ-camera imaging was also performed. CLI intensities of thyroid gland and ARO-NIS were quantified, and compared with the radioactivities measured from nuclear images (NI). Luminometric assay and OI confirmed RI uptake in the cells in a dose-dependent manner, and luminescence intensity was well correlated with radioactivity of the cells. CLI clearly demonstrated RI uptake in thyroid gland and xenografted ARO-NIS cells in mice, which was further confirmed by NI. A strong positive correlation was observed between CLI intensity and radioactivity assessed by NI. We successfully demonstrated dual molecular imaging of CLI and NI using RI both in vitro and in vivo. CLI can provide a new OI strategy in preclinical thyroid studies.

Detailed visualization of the functional regions of the rat pituitary gland by high-resolution T2-weighted MRI

This high-resolution MRI study focuses on the visualization of the detailed morphology of the rat's pituitary gland by means of post-mortem as well as in vivo MRI at 9.4 T. Determination of the local T1- and T2-relaxation decay times allows to explain the regional image intensities which reflects the degree of tissue organization at the molecular level. Detailed characterization of the molecular level of the pituitary gland, as provided by the relaxation decay times, can offer a rigid platform with respect to functional or pathological explorations. It is demonstrated that T1-weighted imaging, as is routinely used in the clinic, can differentiate between the posterior and anterior lobe but not between the posterior and intermediate lobe. T2-weighted images, however, clearly show the three distinct lobes of the rat pituitary gland without the use of contrast agents, i.e. the posterior, the intermediate and the anterior lobe. Histological analysis of the rat's pituitary gland confirms the morphological structures seen on the MR images. Although the intermediate lobe is less defined in humans and can neither be differentiated by T1-weighted MRI, its clinical visualization might be possible in T2-weighted images.