Publications by authors named "Anne Roivainen"

135 Publications

Association between [Ga]NODAGA-RGDyK uptake and dynamics of angiogenesis in a human cell-based 3D model.

Mol Biol Rep 2021 Jun 2;48(6):5347-5353. Epub 2021 Jul 2.

Turku PET Centre, University of Turku, Turku, Finland.

Radiolabeled RGD peptides targeting expression of αβ integrin have been applied to in vivo imaging of angiogenesis. However, there is a need for more information on the quantitative relationships between RGD peptide uptake and the dynamics of angiogenesis. In this study, we sought to measure the binding of [Ga]NODAGA-RGDyK to αβ integrin in a human cell-based three-dimensional (3D) in vitro model of angiogenesis, and to compare the level of binding with the amount of angiogenesis. Experiments were conducted using a human cell-based 3D model of angiogenesis consisting of co-culture of human adipose stem cells (hASCs) and of human umbilical vein endothelial cells (HUVECs). Angiogenesis was induced with four concentrations (25%, 50%, 75%, and 100%) of growth factor cocktail resulting in a gradual increase in the density of the tubule network. Cultures were incubated with [Ga]NODAGA-RGDyK for 90 min at 37 °C, and binding of radioactivity was measured by gamma counting and digital autoradiography. The results revealed that tracer binding increased gradually with neovasculature density. In comparison with vessels induced with a growth factor concentration of 25%, the uptake of [Ga]NODAGA-RGDyK was higher at concentrations of 75% and 100%, and correlated with the amount of neovasculature, as determined by visual evaluation of histological staining. Uptake of [Ga]NODAGA-RGDyK closely reflected the amount of angiogenesis in an in vitro 3D model of angiogenesis. These results support further evaluation of RGD-based approaches for targeted imaging of angiogenesis.
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http://dx.doi.org/10.1007/s11033-021-06513-8DOI Listing
June 2021

Statistical Evaluation of Different Mathematical Models for Diffusion Weighted Imaging of Prostate Cancer Xenografts in Mice.

Front Oncol 2021 26;11:583921. Epub 2021 May 26.

Department of Radiology, University of Turku, Turku, Finland.

Purpose: To evaluate fitting quality and repeatability of four mathematical models for diffusion weighted imaging (DWI) during tumor progression in mouse xenograft model of prostate cancer.

Methods: Human prostate cancer cells (PC-3) were implanted subcutaneously in right hind limbs of 11 immunodeficient mice. Tumor growth was followed by weekly DWI examinations using a 7T MR scanner. Additional DWI examination was performed after repositioning following the fourth DWI examination to evaluate short term repeatability. DWI was performed using 15 and 12 b-values in the ranges of 0-500 and 0-2000 s/mm, respectively. Corrected Akaike information criteria and F-ratio were used to evaluate fitting quality of each model (mono-exponential, stretched exponential, kurtosis, and bi-exponential).

Results: Significant changes were observed in DWI data during the tumor growth, indicated by ADC, ADC, and ADC. Similar results were obtained using low as well as high b-values. No marked changes in model preference were present between the weeks 1-4. The parameters of the mono-exponential, stretched exponential, and kurtosis models had smaller confidence interval and coefficient of repeatability values than the parameters of the bi-exponential model.

Conclusion: Stretched exponential and kurtosis models showed better fit to DWI data than the mono-exponential model and presented with good repeatability.
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http://dx.doi.org/10.3389/fonc.2021.583921DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188898PMC
May 2021

Controlled Monofunctionalization of Molecular Spherical Nucleic Acids on a Buckminster Fullerene Core.

Bioconjug Chem 2021 06 16;32(6):1130-1138. Epub 2021 May 16.

Department of Chemistry, University of Turku, FI-20014 Turku, Finland.

An azide-functionalized 12-armed Buckminster fullerene has been monosubstituted in organic media with a substoichiometric amount of cyclooctyne-modified oligonucleotides. Exposing the intermediate products then to the same reaction (i.e., strain-promoted alkyne-azide cycloaddition, SPAAC) with an excess of slightly different oligonucleotide constituents in an aqueous medium yields molecularly defined monofunctionalized spherical nucleic acids (SNAs). This procedure offers a controlled synthesis scheme in which one oligonucleotide arm can be functionalized with labels or other conjugate groups (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, DOTA, and Alexa-488 demonstrated), whereas the rest of the 11 arms can be left unmodified or modified by other conjugate groups in order to decorate the SNAs' outer sphere. Extra attention has been paid to the homogeneity and authenticity of the C-azide scaffold used for the assembly of full-armed SNAs.
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http://dx.doi.org/10.1021/acs.bioconjchem.1c00187DOI Listing
June 2021

Evaluation of glucagon-like peptide-1 receptor expression in nondiabetic and diabetic atherosclerotic mice using PET tracer Ga-NODAGA-exendin-4.

Am J Physiol Endocrinol Metab 2021 05 12;320(5):E989-E998. Epub 2021 Apr 12.

Turku PET Centre, University of Turku, Turku, Finland.

Cardiovascular effects of glucagon-like peptide-1 receptor (GLP-1R) agonist therapies are potentially mediated by anti-inflammatory effects on atherosclerosis. Our study demonstrates that Ga-NODAGA-exendin-4, a radioligand specifically targeting GLP-1R, detects GLP-1R expression in inflamed atherosclerotic lesions in nondiabetic and diabetic hypercholesterolemic mice. Immunofluorescence staining suggests that GLP-1R is primarily localized in M2 macrophages in lesions. This study describes a new potential tool that may have translational relevance for studies of pharmacological modification of GLP-1R signaling in atherosclerosis.
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http://dx.doi.org/10.1152/ajpendo.00465.2020DOI Listing
May 2021

Docetaxel chemotherapy response in PC3 prostate cancer mouse model detected by rotating frame relaxations and water diffusion.

NMR Biomed 2021 04 4;34(4):e4483. Epub 2021 Feb 4.

A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.

MRI is a common method of prostate cancer diagnosis. Several MRI-derived markers, including the apparent diffusion coefficient (ADC) based on diffusion-weighted imaging, have been shown to provide values for prostate cancer detection and characterization. The hypothesis of the study was that docetaxel chemotherapy response could be picked up earlier with rotating frame relaxation times T and T than with the continuous wave T , adiabatic T , adiabatic T , T , T or water ADC. Human PC3 prostate cancer cells expressing a red fluorescent protein were implanted in 21 male mice. Docetaxel chemotherapy was given once a week starting 1 week after cell implantation for 10 randomly selected mice, while the rest served as a control group (n = 11). The MRI consisted of relaxation along a fictitious field (RAFF) in the second (RAFF2) and fourth (RAFF4) rotating frames, T and T , continuous wave T , adiabatic T and adiabatic T relaxation time measurements and water ADC. MRI was conducted at 7 T, once a week up to 4 weeks from cell implantation. The tumor volume was monitored using T -weighted MRI and optical imaging. The histology was evaluated after the last imaging time point. Significantly reduced RAFFn, T T and conventional relaxation times 4 weeks after tumor implantation were observed in the treated tumors compared with the controls. The clearest short- and long-term responses were obtained with T , while no clear improvement in response to treatment was detected with novel methods compared with conventional methods or with RAFFn compared with all others. The tumor volume decreased after a two-week time point for the treated group and increased significantly in the control group, which was supported by increasing red fluorescent light emission in the control tumors. Decreased relaxation times were associated with successful chemotherapy outcomes. The results indicate altered relaxation mechanisms compared with higher dose chemotherapies previously published.
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http://dx.doi.org/10.1002/nbm.4483DOI Listing
April 2021

Efficacy and tolerability of folate-aminopterin therapy in a rat focal model of multiple sclerosis.

J Neuroinflammation 2021 Jan 20;18(1):30. Epub 2021 Jan 20.

Turku PET Centre, University of Turku, Turku, Finland.

Background: Activated macrophages in the experimental model of multiple sclerosis (MS) express folate receptor-β (FR-β), representing a promising target for the treatment of MS. Here, we both evaluated the efficacy of a novel folate-aminopterin construct (EC2319) in a rat focal model of multiple sclerosis (MS) and investigated the utility of Ga-labeled 1,4,7-triazacyclononane-1,4,7-triacetic acid-conjugated folate (Ga-FOL) for assessing inflammatory lesions. In addition, we investigated whether FR-β is expressed in the brain of patients with MS.

Methods: Focal delayed-type hypersensitivity experimental autoimmune encephalomyelitis (fDTH-EAE) was induced in 40 Lewis rats; 20 healthy Lewis rats were used as controls. Rats were divided into six groups according to the duration of disease (control, acute, or chronic) and intervention (vehicle versus EC2319). Ga-FOL analyses, histology, and immunofluorescence of the brain were performed to evaluate the efficacy of subcutaneously administered EC2319 on lesion development. Immunofluorescence was used to assess FR-β expression in postmortem brain samples from 5 patients with MS and 5 healthy controls.

Results: Immunofluorescence and histological analyses revealed significant reductions in FR-β expression (P < 0.05) and lesion size (P < 0.01), as well as improved inducible nitric oxide synthase/mannose receptor C type 1 ratios (P < 0.01) in macrophages and microglia during the chronic but not acute phase of fDTH-EAE in EC2319-treated rats. The uptake of IV-injected Ga-FOL in the brain was low and did not differ between the groups, but the in vitro binding of Ga-FOL was significantly lower in EC2319-treated rats (P < 0.01). FR-β positivity was observed in chronically active lesions and in normal-appearing white matter in MS brain samples.

Conclusions: EC2319 was well tolerated and attenuated inflammation and lesion development in a rat model of a chronic progressive form of MS. Human MS patients have FR-β-positive cells in chronically active plaques, which suggests that these results may have translational relevance.
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http://dx.doi.org/10.1186/s12974-021-02073-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7819223PMC
January 2021

Seasonal Variation in the Brain μ-Opioid Receptor Availability.

J Neurosci 2021 02 23;41(6):1265-1273. Epub 2020 Dec 23.

Turku PET Centre, University of Turku, FIN-20520 Turku, Finland.

Seasonal rhythms influence mood and sociability. The brain μ-opioid receptor (MOR) system modulates a multitude of seasonally varying socioemotional functions, but its seasonal variation remains elusive with no previously reported evidence. Here, we first conducted a cross-sectional study with previously acquired human [C]carfentanil PET imaging data (132 male and 72 female healthy subjects) to test whether there is seasonal variation in MOR availability. We then investigated experimentally whether seasonal variation in daylength causally influences brain MOR availability in rats. Rats (six male and three female rats) underwent daylength cycle simulating seasonal changes; control animals (two male and one female rats) were kept under constant daylength. Animals were scanned repeatedly with [C]carfentanil PET imaging. Seasonally varying daylength had an inverted U-shaped functional relationship with brain MOR availability in humans. Brain regions sensitive to daylength spanned the socioemotional brain circuits, where MOR availability peaked during spring. In rats, MOR availabilities in the brain neocortex, thalamus, and striatum peaked at intermediate daylength. Varying daylength also affected the weight gain and stress hormone levels. We conclude that cerebral MOR availability in humans and rats shows significant seasonal variation, which is predominately associated with seasonal photoperiodic variation. Given the intimate links between MOR signaling and socioemotional behavior, these results suggest that the MOR system might underlie seasonal variation in human mood and social behavior. Seasonal rhythms influence emotion and sociability. The central μ-opioid receptor (MOR) system modulates numerous seasonally varying socioemotional functions, but its seasonal variation remains elusive. Here we used positron emission tomography to show that MOR levels in both human and rat brains show daylength-dependent seasonal variation. The highest MOR availability was observed at intermediate daylengths. Given the intimate links between MOR signaling and socioemotional behavior, these results suggest that the MOR system might underlie seasonal variation in human mood and social behavior.
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http://dx.doi.org/10.1523/JNEUROSCI.2380-20.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7888218PMC
February 2021

Evaluation of image quality with four positron emitters and three preclinical PET/CT systems.

EJNMMI Res 2020 Dec 10;10(1):155. Epub 2020 Dec 10.

Turku PET Centre, University of Turku, Turku, Finland.

Background: We investigated the image quality of C, Ga, F and Zr, which have different positron fractions, physical half-lifes and positron ranges. Three small animal positron emission tomography/computed tomography (PET/CT) systems were used in the evaluation, including the Siemens Inveon, RAYCAN X5 and Molecubes β-cube. The evaluation was performed on a single scanner level using the national electrical manufacturers association (NEMA) image quality phantom and analysis protocol. Acquisitions were performed with the standard NEMA protocol for F and using a radionuclide-specific acquisition time for C, Ga and Zr. Images were assessed using percent recovery coefficient (%RC), percentage standard deviation (%STD), image uniformity (%SD), spill-over ratio (SOR) and evaluation of image quantification.

Results: Ga had the lowest %RC (< 62%) across all systems. F had the highest maximum %RC (> 85%) and lowest %STD for the 5 mm rod across all systems. For C and Zr, the maximum %RC was close (> 76%) to the %RC with F. A larger SOR were measured in water with C and Ga compared to F on all systems. SOR in air reflected image reconstruction and data correction performance. Large variation in image quantification was observed, with maximal errors of 22.73% (Zr, Inveon), 17.54% (Zr, RAYCAN) and - 14.87% (Ga, Molecubes).

Conclusions: The systems performed most optimal in terms of NEMA image quality parameters when using F, where C and Zr performed slightly worse than F. The performance was least optimal when using Ga, due to large positron range. The large quantification differences prompt optimization not only by terms of image quality but also quantification. Further investigation should be performed to find an appropriate calibration and harmonization protocol and the evaluation should be conducted on a multi-scanner and multi-center level.
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http://dx.doi.org/10.1186/s13550-020-00724-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7728905PMC
December 2020

The circadian gene Cryptochrome 2 influences stress-induced brain activity and depressive-like behavior in mice.

Genes Brain Behav 2021 Apr 26;20(4):e12708. Epub 2020 Oct 26.

Molecular and Integrative Biosciences Research Program, University of Helsinki, Helsinki, Finland.

Cryptochrome 2 (Cry2) is a core clock gene important for circadian regulation. It has also been associated with anxiety and depressive-like behaviors in mice, but the previous findings have been conflicting in terms of the direction of the effect. To begin to elucidate the molecular mechanisms of this association, we carried out behavioral testing, PET imaging, and gene expression analysis of Cry2 and Cry2 mice. Compared to Cry2 mice, we found that Cry2 mice spent less time immobile in the forced swim test, suggesting reduced despair-like behavior. Moreover, Cry2 mice had lower saccharin preference, indicative of increased anhedonia. In contrast, we observed no group differences in anxiety-like behavior. The behavioral changes were accompanied by lower metabolic activity of the ventro-medial hypothalamus, suprachiasmatic nuclei, ventral tegmental area, anterior and medial striatum, substantia nigra, and habenula after cold stress as measured by PET imaging with a glucose analog. Although the expression of many depression-associated and metabolic genes was upregulated or downregulated by cold stress, we observed no differences between Cry2 and Cry2 mice. These findings are consistent with other studies showing that Cry2 is required for normal emotional behavior. Our findings confirm previous roles of Cry2 in behavior and extend them by showing that the effects on behavior may be mediated by changes in brain metabolism.
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http://dx.doi.org/10.1111/gbb.12708DOI Listing
April 2021

First-in-Humans Study of Ga-DOTA-Siglec-9, a PET Ligand Targeting Vascular Adhesion Protein 1.

J Nucl Med 2021 04 17;62(4):577-583. Epub 2020 Aug 17.

Turku PET Centre, University of Turku, Turku, Finland

Sialic acid-binding immunoglubulinlike lectin 9 (Siglec-9) is a ligand of vascular adhesion protein 1. A Ga-labeled peptide of Siglec-9, Ga-DOTA-Siglec-9, holds promise as a novel PET tracer for imaging of inflammation. This first-in-humans study investigated the safety, tolerability, biodistribution, and radiation dosimetry of this radiopharmaceutical. Six healthy men underwent dynamic whole-body PET/CT. Serial venous blood samples were drawn from 1 to 240 min after intravenous injection of 162 ± 4 MBq of Ga-DOTA-Siglec-9. In addition to γ-counting, the plasma samples were analyzed by high-performance liquid chromatography to detect intact tracer and radioactive metabolites. Radiation doses were calculated using the OLINDA/EXM software, version 2.2. In addition, a patient with early rheumatoid arthritis was studied with both Ga-DOTA-Siglec-9 and F-FDG PET/CT to determine the ability of the new tracer to detect arthritis. Ga-DOTA-Siglec-9 was well tolerated by all subjects. Ga-DOTA-Siglec-9 was rapidly cleared from the blood circulation, and several radioactive metabolites were detected. The organs with the highest absorbed doses were the urinary bladder wall (0.38 mSv/MBq) and kidneys (0.054 mSv/MBq). The mean effective dose was 0.022 mSv/MBq (range, 0.020-0.024 mSv/MBq). Most importantly, however, Ga-DOTA-Siglec-9 was comparable to F-FDG in detecting arthritis. Intravenous injection of Ga-DOTA-Siglec-9 was safe and biodistribution was favorable for testing of the tracer in larger group of patients with rheumatoid arthritis, as is planned for the next phase of clinical trials. The effective radiation dose of Ga-DOTA-Siglec-9 was within the same range as the effective radiation doses of other Ga-labeled tracers. Injection of 150 MBq of Ga-DOTA-Siglec-9 would expose a subject to 3.3 mSv. These findings support the possible repeated clinical use of Ga-DOTA-Siglec-9, such as in trials to elucidate the treatment efficacy of novel drug candidates.
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http://dx.doi.org/10.2967/jnumed.120.250696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8049366PMC
April 2021

Radiosynthesis and preclinical evaluation of [Ga]Ga-NOTA-folate for PET imaging of folate receptor β-positive macrophages.

Sci Rep 2020 08 12;10(1):13593. Epub 2020 Aug 12.

Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland.

Folate receptor β (FR-β), a marker expressed on macrophages, is a promising target for imaging of inflammation. Here, we report the radiosynthesis and preclinical evaluation of [Ga]Ga-NOTA-folate (Ga-FOL). After determining the affinity of Ga-FOL using cells expressing FR-β, we studied atherosclerotic mice with Ga-FOL and F-FDG PET/CT. In addition, we studied tracer distribution and co-localization with macrophages in aorta cryosections using autoradiography, histology, and immunostaining. The specificity of Ga-FOL was assessed in a blocking study with folate glucosamine. As a final step, human radiation doses were extrapolated from rat PET data. We were able to produce Ga-FOL with high radiochemical purity and moderate molar activity. Cell binding studies revealed that Ga-FOL had 5.1 nM affinity for FR-β. Myocardial uptake of Ga-FOL was 20-fold lower than that of F-FDG. Autoradiography and immunohistochemistry of the aorta revealed that Ga-FOL radioactivity co-localized with Mac-3-positive macrophage-rich atherosclerotic plaques. The plaque-to-healthy vessel wall ratio of Ga-FOL was significantly higher than that of F-FDG. Blocking studies verified that Ga-FOL was specific for FR. Based on estimations from rat data, the human effective dose was 0.0105 mSv/MBq. Together, these findings show that Ga-FOL represents a promising new FR-β-targeted tracer for imaging macrophage-associated inflammation.
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http://dx.doi.org/10.1038/s41598-020-70394-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423886PMC
August 2020

F-FDG positron emission tomography/computed tomography of cardiac implantable electronic device infections.

J Nucl Cardiol 2020 Jul 31. Epub 2020 Jul 31.

Division of Medicine, Turku University Hospital, P.O. Box 52, 20521, Turku, Finland.

Background: The diagnosis of cardiac implantable electronic device (CIED) infection is challenging because of its variable presentations. We studied the value of 2-[F]fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography/computed tomography (PET/CT) in the detection of CIED infection.

Methods And Results: Thirty patients with suspected CIED infection underwent F-FDG-PET/CT. The control group was ten patients with asymptomatic CIED who underwent cancer-related F-FDG-PET/CT. F-FDG-PET/CT was evaluated visually, semiquantitatively as maximum standardized uptake value (SUV) and target-to-background ratio (TBR). Final diagnosis of CIED infection was based on clinical and bacteriological data. F-FDG-PET/CT was visually positive in all 9 patients with recent (≤ 8 weeks) implantation of CIED, but only 4 had confirmed CIED infection. F-FDG-PET/CT was true positive in 9 out of 21 cases with remote implantation of CIED and false positive in 3 (14.3%) cases. F-FDG-PET/CT was also false positive in 3 (30%) cases of control group. The SUV of the pocket area was significantly higher in patients with CIED infection than in the control group (4.8 ± 2.4 vs 2.0 ± .8, P < .001). By using the cut-off value of TBR ≥ 1.8, sensitivity of F-FDG-PET/CT for the diagnosis of CIED infection in patients with remote implantation was 90% and specificity 73%, PPV 75%, and NPV 89%.

Conclusions: F-FDG-PET/CT is a sensitive but nonspecific method in the diagnosis of CIED infection.
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http://dx.doi.org/10.1007/s12350-020-02256-4DOI Listing
July 2020

Hydroxysteroid (17β) dehydrogenase 12 is essential for metabolic homeostasis in adult mice.

Am J Physiol Endocrinol Metab 2020 09 21;319(3):E494-E508. Epub 2020 Jul 21.

Turku Center for Disease Modeling, Institute of Biomedicine, University of Turku, Turku, Finland.

Hydroxysteroid 17β dehydrogenase 12 (HSD17B12) is suggested to be involved in the elongation of very long chain fatty acids. Previously, we have shown a pivotal role for the enzyme during mouse development. In the present study we generated a conditional knockout (HSD17B12cKO) mouse model by breeding mice homozygous for a floxed allele with mice expressing the tamoxifen-inducible Cre recombinase at the ROSA26 locus. Gene inactivation was induced by administering tamoxifen to adult mice. The gene inactivation led to a 20% loss of body weight within 6 days, associated with drastic reduction in both white (83% males, 75% females) and brown (65% males, 60% females) fat, likely due to markedly reduced food and water intake. Furthermore, the knockout mice showed sickness behavior and signs of liver toxicity, specifically microvesicular hepatic steatosis and increased serum alanine aminotransferase (4.6-fold in males, 7.7-fold in females). The hepatic changes were more pronounced in females than males. Proinflammatory cytokines, such as interleukin-6 (IL-6), IL-17, and granulocyte colony-stimulating factor, were increased in the HSD17B12cKO mice indicating an inflammatory response. Serum lipidomics study showed an increase in the amount of dihydroceramides, despite the dramatic overall loss of lipids. In line with the proposed role for HSD17B12 in fatty acid elongation, we observed accumulation of ceramides, dihydroceramides, hexosylceramides, and lactosylceramides with shorter than 18-carbon fatty acid side chains in the serum. The results indicate that HSD17B12 is essential for proper lipid homeostasis and HSD17B12 deficiency rapidly results in fatal systemic inflammation and lipolysis in adult mice.
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http://dx.doi.org/10.1152/ajpendo.00042.2020DOI Listing
September 2020

Effects of dipeptidyl peptidase 4 inhibition on inflammation in atherosclerosis: A F-fluorodeoxyglucose study of a mouse model of atherosclerosis and type 2 diabetes.

Atherosclerosis 2020 07 10;305:64-72. Epub 2020 Apr 10.

Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, FI-20520, Turku, Finland; Turku PET Centre, Turku University Hospital, Kiinamyllynkatu 4-8, FI-20520, Turku, Finland; Heart Center, Turku University Hospital, Hämeentie 11, FI-20520, Turku, Finland. Electronic address:

Background And Aims: Dipeptidyl peptidase 4 (DPP-4) inhibitors have anti-inflammatory and atheroprotective effects. We evaluated the effects of the DPP-4 inhibitor linagliptin on atherosclerotic plaque and hepatic inflammation using histology and 2-deoxy-2-[F]-fluoro-d-glucose (F-FDG), a positron emission tomography tracer of inflammation, in a mouse model of hypercholesterolemia and type 2 diabetes.

Methods: Igf2/LdlrApob mice were fed a high-fat diet (HFD) for 8 weeks and then randomly allocated to receive HFD (n = 14), or HFD with added linagliptin (n = 15) for additional 12 weeks. Five mice fed a chow diet were studied as an additional control. At the end of the study, glucose tolerance, aortic and liver uptake of F-FDG, and histology were studied.

Results: Mice in linagliptin and HFD groups had similar fasting glucose concentrations, but linagliptin improved glucose tolerance. Aortas of linagliptin and HFD groups showed advanced atherosclerotic plaques with no difference in the mean intima-to-media ratio or number of macrophages in the plaques. Autoradiography showed similar F-FDG uptake by atherosclerotic plaques in linagliptin and HFD groups (plaque-to-wall ratio: 1.7 ± 0.25 vs. 1.6 ± 0.21; p = 0.24). In the liver, linagliptin reduced the histologic inflammation score but had no effect on F-FDG uptake. Compared with chow diet, uptake of F-FDG was similar in the aorta, but higher in the liver after HFD.

Conclusions: Linagliptin therapy improved glucose tolerance and reduced hepatic inflammation but had no effect on plaque burden or atherosclerotic inflammation, as determined by histology and F-FDG uptake, in atherosclerotic mice with type 2 diabetes.
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http://dx.doi.org/10.1016/j.atherosclerosis.2020.03.029DOI Listing
July 2020

Therapeutic Antibody Against Phosphorylcholine Preserves Coronary Function and Attenuates Vascular F-FDG Uptake in Atherosclerotic Mice.

JACC Basic Transl Sci 2020 Apr 25;5(4):360-373. Epub 2020 Mar 25.

Turku PET Centre, University of Turku, Turku, Finland.

This study showed that treatment with a therapeutic monoclonal immunoglobulin-G1 antibody against phosphorylcholine on oxidized phospholipids preserves coronary flow reserve and attenuates atherosclerotic inflammation as determined by the uptake of F-fluorodeoxyglucose in atherosclerotic mice. The noninvasive imaging techniques represent translational tools to assess the efficacy of phosphorylcholine-targeted therapy on coronary artery function and atherosclerosis in clinical studies.
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http://dx.doi.org/10.1016/j.jacbts.2020.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7188869PMC
April 2020

Folate Receptor β-Targeted PET Imaging of Macrophages in Autoimmune Myocarditis.

J Nucl Med 2020 11 13;61(11):1643-1649. Epub 2020 Apr 13.

Turku PET Centre, University of Turku, Turku, Finland

Currently available imaging techniques have limited specificity for the detection of active myocardial inflammation. Aluminum F-labeled 1,4,7-triazacyclononane--triacetic acid conjugated folate (F-FOL) is a PET tracer targeting folate receptor β (FR-β), which is expressed on activated macrophages at sites of inflammation. We evaluated F-FOL PET for the detection of myocardial inflammation in rats with autoimmune myocarditis and studied the expression of FR-β in human cardiac sarcoidosis specimens. Myocarditis was induced by immunizing rats ( = 18) with porcine cardiac myosin in complete Freund adjuvant. Control rats ( = 6) were injected with Freund adjuvant alone. F-FOL was intravenously injected, followed by imaging with a small-animal PET/CT scanner and autoradiography. Contrast-enhanced high-resolution CT or F-FDG PET images were used for coregistration. Rat tissue sections and myocardial autopsy samples from 6 patients with cardiac sarcoidosis were studied for macrophages and FR-β. The myocardium of 10 of 18 immunized rats showed focal macrophage-rich inflammatory lesions, with FR-β expression occurring mainly in M1-polarized macrophages. PET images showed focal myocardial F-FOL uptake colocalizing with inflammatory lesions (SUV, 2.1 ± 1.1), whereas uptake in the remote myocardium of immunized rats and controls was low (SUV, 0.4 ± 0.2 and 0.4 ± 0.1, respectively; < 0.01). Ex vivo autoradiography of tissue sections confirmed uptake of F-FOL in myocardial inflammatory lesions. Uptake of F-FOL in inflamed myocardium was efficiently blocked by a nonlabeled FR-β ligand folate glucosamine in vivo. The myocardium of patients with cardiac sarcoidosis showed many FR-β-positive macrophages in inflammatory lesions. In a rat model of autoimmune myocarditis, F-FOL shows specific uptake in inflamed myocardium containing macrophages expressing FR-β, which were also present in human cardiac sarcoid lesions. Imaging of FR-β expression is a potential approach for the detection of active myocardial inflammation.
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http://dx.doi.org/10.2967/jnumed.119.241356DOI Listing
November 2020

In Vivo Imaging of Inflammation and Infection 2019.

Contrast Media Mol Imaging 2020 11;2020:6824583. Epub 2020 Feb 11.

Department of Rheumatology, Amsterdam University Medical Center Location VU University Medical Center, Amsterdam, Netherlands.

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http://dx.doi.org/10.1155/2020/6824583DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7036125PMC
June 2021

(2S, 4R)-4-[F]Fluoroglutamine for In vivo PET Imaging of Glioma Xenografts in Mice: an Evaluation of Multiple Pharmacokinetic Models.

Mol Imaging Biol 2020 08;22(4):969-978

Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, FI-20520, Turku, Finland.

Purpose: The glutamine analogue (2S, 4R)-4-[F]fluoroglutamine ([F]FGln) was investigated to further characterize its pharmacokinetics and acquire in vivo positron emission tomography (PET) images of separate orthotopic and subcutaneous glioma xenografts in mice.

Procedures: [F]FGln was synthesized at a high radiochemical purity as analyzed by high-performance liquid chromatography. An orthotopic model was created by injecting luciferase-expressing patient-derived BT3 glioma cells into the right hemisphere of BALB/cOlaHsd-Foxn1 mouse brains (tumor growth monitored via in vivo bioluminescence), the subcutaneous model by injecting rat BT4C glioma cells into the flank and neck regions of Foxn1 mice. Dynamic PET images were acquired after injecting 10-12 MBq of the tracer into mouse tail veins. Animals were sacrificed 63 min after tracer injection, and ex vivo biodistributions were measured. Tumors and whole brains (with tumors) were cryosectioned, autoradiographed, and stained with hematoxylin-eosin. All images were analyzed with CARIMAS software. Blood sampling of 6 Foxn1 and 6 C57BL/6J mice was performed after 9-14 MBq of tracer was injected at time points between 5 and 60 min then assayed for erythrocyte uptake, plasma protein binding, and plasma parent-fraction of radioactivity to correct PET image-derived whole-blood radioactivity and apply the data to multiple pharmacokinetic models.

Results: Orthotopic human glioma xenografts displayed PET image tumor-to-healthy brain region ratio of 3.6 and 4.8 while subcutaneously xenografted BT4C gliomas displayed (n = 12) a tumor-to-muscle (flank) ratio of 1.9 ± 0.7 (range 1.3-3.4). Using PET image-derived blood radioactivity corrected by population-based stability analyses, tumor uptake pharmacokinetics fit Logan and Yokoi modeling for reversible uptake.

Conclusions: The results reinforce that [F]FGln has preferential uptake in glioma tissue versus that of corresponding healthy tissue and fits well with reversible uptake models.
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http://dx.doi.org/10.1007/s11307-020-01472-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7343746PMC
August 2020

Folate receptor-targeted positron emission tomography of experimental autoimmune encephalomyelitis in rats.

J Neuroinflammation 2019 Dec 3;16(1):252. Epub 2019 Dec 3.

Turku PET Centre, University of Turku, Turku, Finland.

Background: Folate receptor-β (FR-β) is a cell surface receptor that is significantly upregulated on activated macrophages during inflammation and provides a potential target for folate-based therapeutic and diagnostic agents. FR-β expression in central nervous system inflammation remains relatively unexplored. Therefore, we used focally induced acute and chronic phases of experimental autoimmune encephalomyelitis (EAE) to study patterns of FR-β expression and evaluated its potential as an in vivo imaging target.

Methods: Focal EAE was induced in rats using heat-killed Bacillus Calmette-Guérin followed by activation with complete Freund's adjuvant supplemented with Mycobacterium tuberculosis. The rats were assessed with magnetic resonance imaging and positron emission tomography/computed tomography (PET/CT) at acute (14 days) and chronic (90 days) phases of inflammation. The animals were finally sacrificed for ex vivo autoradiography of their brains. PET studies were performed using FR-β-targeting aluminum [F]fluoride-labeled 1,4,7-triazacyclononane-1,4,7-triacetic acid conjugated folate ([F]AlF-NOTA-folate, F-FOL) and 18 kDa translocator protein (TSPO)-targeting N-acetyl-N-(2-[C]methoxybenzyl)-2-phenoxy-5-pyridinamine (C-PBR28). Post-mortem immunohistochemistry was performed using anti-FR-β, anti-cluster of differentiation 68 (anti-CD68), anti-inducible nitric oxide synthase (anti-iNOS), and anti-mannose receptor C-type 1 (anti-MRC-1) antibodies. The specificity of F-FOL binding was verified using in vitro brain sections with folate glucosamine used as a blocking agent.

Results: Immunohistochemical evaluation of focal EAE lesions demonstrated anti-FR-β positive cells at the lesion border in both acute and chronic phases of inflammation. We found that anti-FR-β correlated with anti-CD68 and anti-MRC-1 immunohistochemistry; for MRC-1, the correlation was most prominent in the chronic phase of inflammation. Both F-FOL and C-PBR28 radiotracers bound to the EAE lesions. Autoradiography studies verified that this binding took place in areas of anti-FR-β positivity. A blocking assay using folate glucosamine further verified the tracer's specificity. In the chronic phase of EAE, the lesion-to-background ratio of F-FOL was significantly higher than that of C-PBR28 (P = 0.016).

Conclusion: Our EAE results imply that FR-β may be a useful target for in vivo imaging of multiple sclerosis-related immunopathology. FR-β-targeted PET imaging with F-FOL may facilitate the monitoring of lesion development and complement the information obtained from TSPO imaging by bringing more specificity to the PET imaging armamentarium for neuroinflammation.
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http://dx.doi.org/10.1186/s12974-019-1612-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6892159PMC
December 2019

Kinetic Modelling of [Ga]Ga-DOTA-Siglec-9 in Porcine Osteomyelitis and Soft Tissue Infections.

Molecules 2019 Nov 13;24(22). Epub 2019 Nov 13.

Department of Nuclear Medicine, Aalborg University Hospital, DK-9000 Aalborg, Denmark.

Background: [Ga]Ga-DOTA-Siglec-9 is a positron emission tomography (PET) radioligand for vascular adhesion protein 1 (VAP-1), a protein involved in leukocyte trafficking. The tracer facilitates the imaging of inflammation and infection. Here, we studied the pharmacokinetic modelling of [Ga]Ga-DOTA-Siglec-9 in osteomyelitis and soft tissue infections in pigs.

Methods: Eight pigs with osteomyelitis and soft tissue infections in the right hind limb were dynamically PET scanned for 60 min along with arterial blood sampling. The fraction of radioactivity in the blood accounted for by the parent tracer was evaluated with radio-high-performance liquid chromatography. One- and two-tissue compartment models were used for pharmacokinetic evaluation. Post-mortem soft tissue samples from one pig were analysed with anti-VAP-1 immunofluorescence. In each analysis, the animal's non-infected left hind limb was used as a control.

Results: Tracer uptake was elevated in soft tissue infections but remained low in osteomyelitis. The kinetics of [Ga]Ga-DOTA-Siglec-9 followed a reversible 2-tissue compartment model. The tracer metabolized quickly; however, taking this into account, produced more ambiguous results. Infected soft tissue samples showed endothelial cell surface expression of the Siglec-9 receptor VAP-1.

Conclusion: The kinetics of [Ga]Ga-DOTA-Siglec-9 uptake in porcine soft tissue infections are best described by the 2-tissue compartment model.
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http://dx.doi.org/10.3390/molecules24224094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6891593PMC
November 2019

The Clinical Impact of Using F-FDG-PET/CT in the Diagnosis of Suspected Vasculitis: The Effect of Dose and Timing of Glucocorticoid Treatment.

Contrast Media Mol Imaging 2019 29;2019:9157637. Epub 2019 Aug 29.

Department of Medicine, University of Turku, Turku, Finland.

F-Fluorodeoxyglucose positron-emission tomography (F-FDG-PET) with computed tomography (CT) is effective for diagnosing large vessel vasculitis, but its usefulness in accurately diagnosing suspected, unselected vasculitis remains unknown. We evaluated the feasibility of F-FDG-PET/CT in real-life cohort of patients with suspicion of vasculitis. The effect of the dose and the timing of glucocorticoid (GC) medication on imaging findings were in special interest. 82 patients with suspected vasculitis were evaluated by whole-body F-FDG-PET/CT. GC treatment as prednisolone equivalent doses at the scanning moment and before imaging was evaluated. 38/82 patients were diagnosed with vasculitis. Twenty-one out of 38 patients had increased F-FDG accumulation in blood vessel walls indicating vasculitis in various sized vessels. Vasculitis patients with a positive vasculitis finding in F-FDG-PET/CT had a significantly shorter duration of GC use (median = 4.0 vs 7.0 days, =0.034), and they used lower GC dose during the PET scan (median dose = 15.0 mg/day vs 40.0 mg/day, =0.004) compared to F-FDG-PET/CT-negative patients. Vasculitis patients with a positive F-FDG-PET/CT result had significantly higher C-reactive protein (CRP) than patients with a negative F-FDG-PET/CT finding (mean value = 154.5 vs 90.4 mg/L, =0.018). We found that F-FDG-PET/CT positivity was significantly associated with a lower dose and shorter duration of GC medication and higher CRP level in vasculitis patients. F-FDG-PET/CT revealed clinically significant information in over half of the patients and was effective in confirming the final diagnosis.
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http://dx.doi.org/10.1155/2019/9157637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6735179PMC
July 2020

Fibroblast Growth Factor 21 Drives Dynamics of Local and Systemic Stress Responses in Mitochondrial Myopathy with mtDNA Deletions.

Cell Metab 2019 12 12;30(6):1040-1054.e7. Epub 2019 Sep 12.

Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland; Department of Neurosciences, Helsinki University Central Hospital, 00290 Helsinki, Finland; Neuroscience Center, University of Helsinki, 00290 Helsinki, Finland. Electronic address:

Mitochondrial dysfunction elicits stress responses that safeguard cellular homeostasis against metabolic insults. Mitochondrial integrated stress response (ISR) is a major response to mitochondrial (mt)DNA expression stress (mtDNA maintenance, translation defects), but the knowledge of dynamics or interdependence of components is lacking. We report that in mitochondrial myopathy, ISR progresses in temporal stages and development from early to chronic and is regulated by autocrine and endocrine effects of FGF21, a metabolic hormone with pleiotropic effects. Initial disease signs induce transcriptional ISR (ATF5, mitochondrial one-carbon cycle, FGF21, and GDF15). The local progression to 2 metabolic ISR stage (ATF3, ATF4, glucose uptake, serine biosynthesis, and transsulfuration) is FGF21 dependent. Mitochondrial unfolded protein response marks the 3 ISR stage of failing tissue. Systemically, FGF21 drives weight loss and glucose preference, and modifies metabolism and respiratory chain deficiency in a specific hippocampal brain region. Our evidence indicates that FGF21 is a local and systemic messenger of mtDNA stress in mice and humans with mitochondrial disease.
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http://dx.doi.org/10.1016/j.cmet.2019.08.019DOI Listing
December 2019

Assessment of myocardial viability with [O]water PET: A validation study in experimental myocardial infarction.

J Nucl Cardiol 2019 Jul 17. Epub 2019 Jul 17.

Turku PET Centre, University of Turku, Turku, Finland.

Background: Assessment of myocardial viability is often needed in patients with chest pain and reduced ejection fraction. We evaluated the performance of reduced resting MBF, perfusable tissue fraction (PTF), and perfusable tissue index (PTI) in the assessment of myocardial viability in a pig model of myocardial infarction (MI).

Methods And Results: Pigs underwent resting [O]water PET perfusion study 12 weeks after surgical (n = 16) or 2 weeks after catheter-based (n = 4) occlusion of the proximal left anterior descending coronary artery. MBF, PTF, and PTI were compared with volume fraction of MI in matched segments as assessed by triphenyl tetrazolium chloride staining of LV slices. MBF and PTF were lower in infarcted than non-infarcted segments. Segmental analysis of MBF showed similar area under the curve (AUC) of 0.85, 0.86, and 0.90 with relative MBF, PTF, and PTI for the detection of viable myocardium defined as infarct volume fraction of < 75%. Cut-off values of relative MBF of ≥ 67% and PTF of ≥ 66% resulted in accuracies of 90% and 81%, respectively.

Conclusions: Our results indicate that resting MBF, PTF, and PTI based on [O]water PET perfusion imaging are useful for the assessment of myocardial viability.
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http://dx.doi.org/10.1007/s12350-019-01818-5DOI Listing
July 2019

Evaluation of cardiac function by nuclear imaging in preclinical studies.

J Nucl Cardiol 2020 08 18;27(4):1328-1330. Epub 2019 Jun 18.

Turku PET Centre, Turku University Hospital and University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland.

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http://dx.doi.org/10.1007/s12350-019-01784-yDOI Listing
August 2020

Ga-DOTA chelate, a novel imaging agent for assessment of myocardial perfusion and infarction detection in a rodent model.

J Nucl Cardiol 2020 06 29;27(3):891-898. Epub 2019 May 29.

Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20521, Turku, Finland.

Background: Magnetic resonance imaging (MRI) with Gadolinium 1,4,7,10-tetraazacyclododecane-N',N″,N''',N″″-tetraacetic acid (Gd-DOTA) enables assessment of myocardial perfusion during first-pass of the contrast agent, while increased retention can signify areas of myocardial infarction (MI). We studied whether Gallium-68-labeled analog, Ga-DOTA, can be used to assess myocardial perfusion on positron emission tomography/computed tomography (PET/CT) in rats, comparing it with C-acetate.

Methods: Rats were studied with C-acetate and Ga-DOTA at 24 hours after permanent ligation of the left coronary artery or sham operation. One-tissue compartmental models were used to estimate myocardial perfusion in normal and infarcted myocardium. After the PET scan, hearts were sectioned for autoradiographic detection of Ga-DOTA distribution.

Results: C-acetate PET showed perfusion defects and histology showed myocardial necrosis in all animals after coronary ligation. Kinetic modeling of Ga-DOTA showed significantly higher k values in normal myocardium than in infarcted areas. There was a significant correlation (r = 0.82, P = 0.001) between k values obtained with Ga-DOTA and C-acetate. After 10 minutes of tracer distribution, the Ga-DOTA concentration was significantly higher in the infarcted than normal myocardium on PET imaging and autoradiography.

Conclusions: Our results indicate that acute MI can be detected as reduced perfusion, as well as increased late retention of Ga-DOTA.
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http://dx.doi.org/10.1007/s12350-019-01752-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7326802PMC
June 2020

Amyloid-Targeting PET Tracer [F]Flutemetamol Accumulates in Atherosclerotic Plaques.

Molecules 2019 Mar 19;24(6). Epub 2019 Mar 19.

Turku PET Centre, University of Turku, FI-20520 Turku, Finland.

Atherosclerosis is characterized by the accumulation of oxidized lipids in the artery wall, which triggers an inflammatory response. Oxidized low-density lipoprotein (ox-LDL) presents amyloid-like structural properties, and different amyloid species have recently been recognized in atherosclerotic plaques. Therefore, we studied the uptake of the amyloid imaging agent [F]Flutemetamol in atherosclerotic plaques. The binding of [F]Flutemetamol to human carotid artery plaque was studied in vitro. In vivo uptake of the tracer was studied in hypercholesterolemic IGF-II/LDLRApoB mice and C57BL/6N controls. Tracer biodistribution was studied in vivo with PET/CT, and ex vivo by gamma counter and digital ex vivo autoradiography. The presence of amyloid, ox-LDL, and macrophages in the plaques was examined by immunohistochemistry. [F]Flutemetamol showed specific accumulation in human carotid plaque, especially in areas positive for amyloid beta. The aortas of IGF-II/LDLRApoB mice showed large thioflavin-S-positive atherosclerotic plaques containing ox-LDL and macrophages. Autoradiography revealed 1.7-fold higher uptake in the plaques than in a lesion-free vessel wall, but no difference in aortic tissue uptake between mouse strains were observed in the in vivo PET/CT. In conclusion, [F]Flutemetamol binds to amyloid-positive areas in human atherosclerotic plaques. Further studies are warranted to clarify the uptake mechanisms, and the potential of the tracer for in vivo imaging of atherosclerosis in patients.
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http://dx.doi.org/10.3390/molecules24061072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471324PMC
March 2019

Noninvasive and Quantitative Monitoring of the Distributions and Kinetics of MicroRNA-Targeting Molecules in Vivo by Positron Emission Tomography.

Mol Pharm 2019 04 22;16(4):1507-1515. Epub 2019 Mar 22.

Turku PET Centre , Turku University Hospital , Turku 20521 , Finland.

MicroRNAs (miRNAs) are endogenous, small, noncoding ribonucleic acids (RNAs) that bind to the 3' untranslated regions of messenger RNAs (mRNAs) and induce translational repression or mRNA degradation. Although numerous studies have reported that miRNAs are of potential use for disease diagnostics and gene therapy, little is known about their fates in vivo. This study elucidated the whole-body distributions and kinetics of intravenously administered miRNA-targeting molecules in vivo by positron emission tomography (PET) imaging. A 22-mer sequence targeting miR-15b was conjugated with three different chelators and labeled with gallium-68 (Ga). These tracers were compared with a scrambled 22-mer sequence; 22-mer with two single base substitutions; anti-miR-34 22-mer; hexathymidylate (T), a 6-mer sequence; and an unconjugated chelator. miR-15b was chosen as a target because it is important for bone remodeling. All three Ga-labeled anti-miR-15b molecules had similar biodistributions and kinetics, and they all accumulated in the bones, kidneys, and liver. The bone accumulation of these tracers was the highest in the epiphyses of long tubular bones, maxilla, and mandible. By contrast, the scrambled 22-mer sequence, the 6-mer, and the unconjugated chelator did not accumulate in bones. PET imaging successfully elucidated the distributions and kinetics of Ga-labeled chelated miRNA-targeting molecules in vivo. This approach is potentially useful to evaluate new miRNA-based drugs.
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http://dx.doi.org/10.1021/acs.molpharmaceut.8b01169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6727608PMC
April 2019

Ga-DOTA-E[c(RGDfK)] PET Imaging of SHARPIN-Regulated Integrin Activity in Mice.

J Nucl Med 2019 10 8;60(10):1380-1387. Epub 2019 Mar 8.

Turku PET Centre, University of Turku, Turku, Finland

Shank-associated RH domain-interacting protein (SHARPIN) is a cytosolic protein that plays a key role in activation of nuclear factor κ-light-chain enhancer of activated B cells and regulation of inflammation. Furthermore, SHARPIN controls integrin-dependent cell adhesion and migration in several normal and malignant cell types, and loss of SHARPIN correlates with increased integrin activity in mice. Arginyl-glycyl-aspartic acid (RGD), a cell adhesion tripeptide motif, is an integrin recognition sequence that facilitates PET imaging of integrin upregulation during tumor angiogenesis. We hypothesized that increased integrin activity due to loss of SHARPIN protein would affect the uptake of αβ-selective cyclic, dimeric peptide Ga-DOTA-E[c(RGDfK)], where E[c(RGDfk)] = glutamic acid-[cyclo(arginyl-glycyl-aspartic acid-D-phenylalanine-lysine)], both in several tissue types and in the tumor microenvironment. To test this hypothesis, we used RGD-based in vivo PET imaging to evaluate wild-type (wt) and SHARPIN-deficient mice ( , where cpdm = chronic proliferative dermatitis in mice) with and without melanoma tumor allografts. mice with spontaneous null mutation in the gene and their wt littermates with or without B16-F10-luc melanoma tumors were studied by in vivo imaging and ex vivo measurements with cyclic-RGD peptide Ga-DOTA-E[c(RGDfK)] After the last Ga-DOTA-E[c(RGDfK)] peptide PET/CT, tumors were cut into cryosections for autoradiography, histology, and immunohistochemistry. The ex vivo uptake of Ga-DOTA-E[c(RGDfK)] in the mouse skin and tumor was significantly higher in mice than in wt mice. B16-F10-luc tumors were detected 4 d after inoculation, without differences in volume or blood flow between the mouse strains. PET imaging with Ga-DOTA-E[c(RGDfK)] peptide at day 10 after inoculation revealed significantly higher uptake in the tumors transplanted into mice than in wt mice. Furthermore, tumor vascularization was increased in the mice. mice demonstrated increased integrin activity and vascularization in B16-F10-luc melanoma tumors, as demonstrated by RGD-based in vivo PET imaging. These data indicate that SHARPIN, a protein previously associated with increased cancer growth and metastasis, may also have important regulatory roles in controlling the tumor microenvironment.
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http://dx.doi.org/10.2967/jnumed.118.222026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6785786PMC
October 2019

Mesenchymal Cell-Derived Juxtacrine Wnt1 Signaling Regulates Osteoblast Activity and Osteoclast Differentiation.

J Bone Miner Res 2019 06 7;34(6):1129-1142. Epub 2019 Mar 7.

Institute of Biomedicine, University of Turku, Turku, Finland.

Human genetic evidence demonstrates that WNT1 mutations cause osteogenesis imperfecta (OI) and early-onset osteoporosis, implicating WNT1 as a major regulator of bone metabolism. However, its main cellular source and mechanisms of action in bone remain elusive. We generated global and limb bud mesenchymal cell-targeted deletion of Wnt1 in mice. Heterozygous deletion of Wnt1 resulted in mild trabecular osteopenia due to decreased osteoblast function. Targeted deletion of Wnt1 in mesenchymal progenitors led to spontaneous fractures due to impaired osteoblast function and increased bone resorption, mimicking the severe OI phenotype in humans with homozygous WNT1 mutations. Importantly, we showed for the first time that Wnt1 signals strictly in a juxtacrine manner to induce osteoblast differentiation and to suppress osteoclastogenesis, in part via canonical Wnt signaling. In conclusion, mesenchymal cell-derived Wnt1, acting in short range, is an essential regulator of bone homeostasis and an intriguing target for therapeutic interventions for bone diseases. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/jbmr.3680DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850336PMC
June 2019

Safety Study of Single-Dose Intravenously Administered DOTA-Siglec-9 Peptide in Sprague Dawley Rats.

Int J Toxicol 2019 Jan/Feb;38(1):4-11. Epub 2019 Jan 20.

2 Turku PET Centre, University of Turku, Turku, Finland.

The peptide-based radioactive compound [Ga]Ga-DOTA-Siglec-9 is a novel agent for imaging of inflammation with positron emission tomography. The drug target of [Ga]Ga-DOTA-Siglec-9 is vascular adhesion protein 1. Previous studies have obtained promising results with [Ga]Ga-DOTA-Siglec-9 in experimental animals. However, before taking this novel imaging agent into clinical trials, safety and toxicological studies need to be performed with the nonradioactive precursor compound DOTA-Siglec-9. This extended single-dose toxicity study was designed to provide information on the major toxic effects of DOTA-Siglec-9 and to indicate possible target organs after a single intravenous (iv) injection in rats. The study was performed using 60 adult Hsd: Sprague Dawley rats and included a control group and a treatment group to investigate the toxicity of DOTA-Siglec-9 solution at a final concentration of 0.2 mg/mL after a single iv injection of 582 µg/kg. The maximum dose tested was 1,000-fold the clinical dose on a mg/kg basis as indicated in European Medicines Agency International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guideline M3(R2). The planned human clinical dose is approximately 0.582 µg of DOTA-Siglec-9 per kg of body mass. This study demonstrates that iv administration of DOTA-Siglec-9 at a dose of 582 µg/kg was well tolerated in rats and did not produce toxicologically significant adverse effects.
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http://dx.doi.org/10.1177/1091581818821606DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357174PMC
December 2019
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