NEMA NU 4-2008 and in vivo imaging performance of RAYCAN trans-PET/CT X5 small animal imaging system.

The RAYCAN Trans-PET/CT X5 is a preclinical positron emission tomography and computed tomography (PET/CT) system intended for in vivo imaging of rats and mice, featuring all-digital readout electronics for PET data acquisition. The National Electrical Manufacturers Association (NEMA) NU 4-2008 performance evaluation was conducted on the RAYCAN Trans-PET/CT X5 in addition to assessing in vivo imaging performance of the system on live animals. The performance characteristics of the system were evaluated, including system spatial resolution, count rate performance, sensitivity and image quality. The system imaging performance is assessed in dynamic in vivo PET imaging. The system resolution defined as full width half maximum (FWHM) was 2.07 mm, 2.11 mm and 1.31 mm for the tangential, radial and axial resolution, respectively, at the center of the field of view. The peak noise equivalent count rate (NECR) values measured were 61 kcps at 0.19 MBq ml-1 for the rat size phantom and 126 kcps at 1.53 MBq ml-1 for the mouse size phantom. Scatter fractions were 24% and 14% for the rat and mouse phantom. The measured peak sensitivity of the system was 1.70%. Image quality in static imaging was deemed sufficient based on the image quality phantom study, with average activity concentration of 155 ± 8.6 kBq ml-1 and image uniformity of 5.57% when using two-dimensional filtered backprojection algorithm (2D-FBP). Rods in the image quality phantom were visualized easily up to 2 mm in size. In dynamic in vivo PET imaging, time-activity-curves from several regions were successfully measured, characterizing the radioactivity distribution in myocardial blood pool, liver, left ventricle and the lung. In conclusion, the RAYCAN Trans-PET/CT X5 system can be considered a suitable option for basic imaging needs in preclinical imaging.

Rapid spread of mannan to the immune system, skin and joints within 6 hours after local exposure.

Psoriasis (Ps), psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are common diseases dependent on environmental factors that activate the immune system in unknown ways. Mannan is a group of polysaccharides common in the environment; they are potentially pathogenic, because at least some of them induce Ps-, PsA- and RA-like inflammation in mice. Here, we used positron emission tomography/computed tomography to examine in-vivo transport and spread of mannan labelled with fluorine-18 [18 F]. The results showed that mannan was transported to joints (knee) and bone marrow (tibia) of mice within 6 h after intraperitoneal injection. The time it took to transport mannan, and its presence in blood, indicated cellular transport of mannan within the circulatory system. In addition, mannan was filtered mainly through the spleen and liver. [18 F]fluoromannan was excreted via kidneys, small intestine and, to some extent, the mouth. In conclusion, mannan reaches joints rapidly after injection, which may explain why mannan-induced inflammatory disease is targeted to these tissues.

In vivo imaging of Lyme arthritis in mice by [18F]fluorodeoxyglucose positron emission tomography/computed tomography.

OBJECTIVE: Lyme borreliosis (LB) is a tick-borne infectious disease caused by Borrelia burgdorferi spirochaetes, which are able to disseminate from the tick-bite site to distant organs. Mouse models are widely used to study LB and especially Lyme arthritis (LA), but only a few whole-animal in vivo imaging studies on the pathogenesis of B. burgdorferi infection in mice have been published so far. The existing imaging techniques have their drawbacks and, therefore, novel tools to complement the array of available LB imaging methodologies are needed. METHOD: The applicability of positron emission tomography combined with computed tomography (PET/CT) imaging was evaluated as a method to monitor LB and especially LA in the C3H/HeN mouse model infected with wild-type B. burgdorferi N40 bacteria. The imaging results were compared with the traditional LA analysis methods, such as tibiotarsal joint swelling and histopathological assessment of joint inflammation. RESULTS: PET/CT imaging provided high-resolution images with quantitative information on the spatial and temporal distribution of the [18F]fluorodeoxyglucose ([18F]FDG) tracer in B. burgdorferi-infected mice. The [18F]FDG accumulated in the affected joints and activated lymph nodes of infected mice, while the tracer signal could not be visualized in these organs in uninfected control animals. Importantly, in vivo PET/CT imaging data were in agreement with the histopathological scoring of inflammation of mouse joints. CONCLUSION: PET/CT imaging with [18F]FDG is a reliable method to longitudinally monitor the development and progression of B. burgdorferi infection-induced inflammation in vivo in mouse joints.

Age-, sex- and glucose-dependent correlation of plasma soluble vascular adhesion protein-1 concentration with cardiovascular risk factors and subclinical atherosclerosis.

OBJECTIVE: Soluble vascular adhesion protein-1 (sVAP-1) may act as a biomarker for atherosclerosis and cardiovascular diseases. The associations of sVAP-1 concentration with cardiovascular risk factors and subclinical atherosclerosis at the population level have not been reported. PATIENTS AND METHODS: This cross-sectional study included 834 asymptomatic subjects (49.1 ± 9.3 years). sVAP-1 was measured by enzyme-linked immunosorbent assay. Subclinical atherosclerosis was assessed by brachial-ankle pulse wave velocity (baPWV) and carotid intima-media thickness (CIMT). RESULTS: sVAP-1 increased with age. Women had a higher concentration than men in age > 40 years. In women, sVAP-1 was negatively associated with estradiol (p < 0.01) and body mass index (BMI) (p < 0.05). In men, sVAP-1 was negatively associated with apolipoprotein A (ApoA) (p < 0.01), alcohol intake (p < 0.01) and uric acid (p < 0.05), but positively associated with ApoB/ApoA (p < 0.05). In hyperglycemia subjects, sVAP-1 positively correlated with fasting plasma glucose (p < 0.05) and hemoglobin A1c (p < 0.05), but in normoglycemic subjects, sVAP-1 negatively correlated with BMI (p < 0.01), triglyceride (p < 0.05), alcohol intake (p < 0.05). sVAP-1 independently influenced CIMT (ß = 0.001, p = 0.040) and carotid plaques [odds ratio 1.380 (95% confidence interval 1.051-1.813, p = 0.021)] in hyperglycemia, and baPWV (ß = 31.605, p = 0.014) in age > 55 years. CONCLUSIONS: sVAP-1 concentration correlates with cardiovascular risk factors and subclinical atherosclerosis in an age-, sex- and glucose-dependent manner.

Evaluation of brain tumor metabolism with [11C]choline PET and 1H-MRS.

BACKGROUND: The signal of choline containing compounds (Cho) in proton magnetic resonance spectroscopy (1H-MRS) is elevated in brain tumors. [11C]choline uptake as assessed using positron emission tomography (PET) has also been suggested to be higher in brain tumors than in the normal brain. We examined whether quantitative analysis of choline accumulation and content using these two novel techniques would be helpful in non-invasive, preoperative evaluation of suspected brain tumors and tumor malignancy grade. METHODS: 12 patients with suspected brain tumor were studied using [11C]choline PET, gadolinium enhanced 3-D magnetic resonance imaging and 1H-MRS prior to diagnostic biopsy or resection. Eleven normal subjects served as control subjects for 1H-MRS. RESULTS: The concentrations of Cho and myoinositol (mI) were higher and the concentration of N-acetyl signal/group (NA) lower in brain tumors than in the corresponding regions of the normal brain. There were no significant differences in metabolite concentrations between low- and high-grade gliomas. In non-tumorous lesions Cho concentrations were lower and NA concentrations higher than in any of the gliomas. Enormously increased lipid peak differentiated lymphomas from all other lesions. The uptake of [11C]choline at PET did not differ between low- and high-grade gliomas. The association between Cho concentration determined in 1H-MRS and [11C]choline uptake measured with PET was not significant. CONCLUSION: Both 1H-MRS and [11C]choline PET can be used to estimate proliferative activity of human brain tumors. These methods seem to be helpful in differential diagnosis between lymphomas, non-tumorous lesions and gliomas but are not superior to histopathological methods in estimation of tumor malignancy grade.

Brain acetylcholinesterase activity in mild cognitive impairment and early Alzheimer's disease.

OBJECTIVE: Brain acetylcholinesterase activity was determined in healthy controls and in patients with mild cognitive impairment and early Alzheimer's disease. METHODS: A specific acetylcholinesterase tracer, [methyl-(11)C]N-methyl-piperidyl-4-acetate ([(11)C]MP4A), and a three dimensional PET system with magnetic resonance coregistration were used for imaging. RESULTS: There was a significant difference in the acetylcholinesterase activity in the hippocampus between the groups (p = 0.03), the mean (SD) acetylcholinesterase activity (k(3) values, min(-1)) being 0.114 (0.036) in controls, 0.098 (0.023) in mild cognitive impairment, and 0.085 (0.022) in Alzheimer's disease. The mini-mental state examination score showed no significant relation with acetylcholinesterase activity in any brain area in the combined mild cognitive impairment/Alzheimer group. CONCLUSIONS: Hippocampal acetylcholinesterase activity is only slightly reduced in mild cognitive impairment and early Alzheimer's disease and so the value of in vivo acetylcholinesterase measurements in detecting the early Alzheimer process is limited.

Identification of alpha6beta1 integrin positive cells in synovial lining layer as type B synoviocytes.

OBJECTIVE: In rheumatoid arthritis (RA) the synovial lining is responsible for cartilage destruction. Laminin is one of the major matrix molecules surrounding the lining cells. We investigated the laminin adhesion mechanism of synovial lining cells by analyzing the presence of its receptor, alpha6beta1 integrin, on type A and type B synoviocytes. METHODS: The alpha6 integrin subunit and a macrophage marker were simultaneously localized by immunohistochemistry in 29 RA derived, 6 osteoarthritis derived, and 2 healthy synovial samples by light and electron microscopy. We also used enzyme treatments to release cells from synovial tissue samples and localized the same antigens on adherent cells. RESULTS: The alpha6beta1 integrin positive cells were localized in basal areas of the lining layer and many of them were negative for the macrophage markers. By immunolabeling electron microscopy the alpha6 integrin positive cells were confirmed to represent the fibroblast-like type B cells. Further, in freshly isolated synoviocyte cultures the type B cells were positive for alpha6 integrin, whereas all other cell types were negative for this laminin receptor. CONCLUSION: Integrin alpha6beta1 is known to be a laminin receptor of endothelial cells, adipocytes, and macrophages, not usually expressed on fibroblasts. However, in synovial lining layer it is expressed on fibroblastic type B cells, but the macrophage population is negative. The unique characteristics of synovial lining cells distinguish them from other connective tissue cells and must be taken into account in all considerations of the pathogenic mechanisms of rheumatoid disease.

Blood metabolism of [methyl-11C]choline; implications for in vivo imaging with positron emission tomography.

[methyl-11C]choline (11C-choline) is a radioligand potentially useful for oncological positron emission tomography (PET). As a first step towards the development of a kinetic model for quantification of 11C-choline uptake, blood metabolism of 11C-choline during PET imaging was studied in humans. High-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) were used for the analysis of 11C-choline and its radioactive metabolites. Prior to human PET imaging we studied ex vivo the biodistribution and metabolism of intravenously administered 11C-choline in rats. Our results revealed that the radioactivity accumulated particularly in kidney, lung, adrenal gland and liver. Chromatographic analysis showed that the level of unmetabolized 11C-choline in rat plasma decreased from 42% +/- 20% (mean +/- SD) at 5 min to 21% +/- 10% at 15 min after injection. In accordance with these findings, in humans the unmetabolized 11C-choline represents 62% +/- 19% of the total radioactivity in arterial plasma at 5 min after injection and 27% +/- 12% at 15 min. In human venous plasma the corresponding values were 85% +/- 12% and 48% +/- 12% at 5 and 10 min, respectively. The major metabolite observed in both human and rat plasma was identified as 11C-betaine. In human arterial plasma this maximally represented 82% +/- 9% of the total radioactivity at 25 min after radiotracer injection. By 20 min after injection, the 11C-choline and 11C-betaine in human arterial plasma reached a plateau, and their fractional activities remained nearly constant thereafter. Although most of the circulating 11C-choline in blood is transported to tissues, it does not disappear totally from blood within the first 40 min after tracer injection.

Expression of the myc-family proto-oncogenes and related genes max and mad in synovial tissue.

OBJECTIVE: To examine the expression of myc proto-oncogenes; c-myc, L-myc, and N-myc, and their related genes max and mad, in the arthritic synovium. METHODS: Using reverse transcription-polymerase chain reaction (RT-PCR), Northern and Southern hybridizations, the expression of these genes in the synovial tissue from rheumatoid arthritis (RA) and osteoarthritis (OA) was analyzed. Synovial specimens from cadavers without any joint disease and peripheral blood mononuclear cells (PBMC) from healthy individuals served as controls. RESULTS: As a novel finding, synovial cells were observed to express L-myc, N-myc as well as their related genes max and mad, in addition to the previously described presence of c-myc proto-oncogene in synovium. c-myc, L-myc, N-myc, and mad were expressed in all patient samples studied, including the controls. Instead, max was detected in only 10/12 of RA patients, in 11/13 of OA patients, and in all controls (4/4 cadavers, 5/5 blood donors). Six patients with RA revealed positive signals for max only after hybridization. The same was also true of two patients with OA and of one healthy individual donating blood. CONCLUSIONS: The L-myc, N-myc, max, and mad genes are expressed in synovial cells, in addition to c-myc proto-oncogene. However, expression of these genes is not disease-specific, since they were equally expressed in synovial samples from patients with RA or OA as well as from cadavers representing controls without any joint disease.

H-ras oncogene point mutations in arthritic synovium.

OBJECTIVE: To examine mutational activation of ras proto-oncogenes in synovial tissue from patients with rheumatoid arthritis (RA) compared with synovial specimens from patients with osteoarthritis (OA) or other arthropathies. Synovial samples from cadavers, without any signs of joint disease, were used as control material. METHODS: Using a combination of polymerase chain reaction (PCR) and automated sequencing of the amplified PCR product, regions around codons 12, 13, and 61 of the H-, K-, and N-ras proto-oncogenes were analyzed. Confirmation of mutations was based on restriction fragment length polymorphism analysis and/or oligonucleotide hybridization. RESULTS: Four (6%) of 72 patients with RA, 2 (13%) of 16 with OA, and 1 (8%) of 12 with other arthropathies harbored mutant H-ras proto-oncogenes, and were heterozygous at codon 13 for the GGT-->GAT (Gly-->Asp) change. An unexpected mutation was found in the H-ras gene, in which a heterozygous GTG-->ATG (Val-->Met) mutation was observed over codon 14. The incidence for this mutation was 39% (28 of 72) in RA patients, 94% (15 of 16) in OA patients, and 42% (5 of 12) in patients with other arthropathies. All samples carrying the codon 13 mutation of H-ras were also codon 14-mutated, i.e., double mutations existed. Identical point mutations were also detected in a few synovial specimens obtained from cadavers (n = 8), including a single case of double mutation. All specimens showed normal K- and N-ras loci. CONCLUSION: Activation of proto-oncogene H-ras by point mutation in codons 13 and 14 occurred in the synovial tissue of patients with RA, OA, or other arthropathies, as well as, to some extent, in the control synovia, indicating that the phenomenon is not specific for RA. In codon 14, incidence of the H-ras point mutation was highest in OA tissue. The possible significance of this codon 14-mutated H-ras gene needs to be clarified.

Oncoprotein expression in human synovial tissue: an immunohistochemical study of different types of arthritis.

Based on the fact that synovial lining cells have some properties of transformed-appearing cells, we have examined the expression of Myc, Myb, Fos, Jun and Ras oncoproteins in synovial tissues from patients with different types of arthritis. Formalin-fixed and paraffin-embedded sections of synovial tissue from 12 patients with rheumatoid arthritis (RA), 14 with reactive arthritis (ReA), nine with other seronegative arthritis (OSA), seven with bacterial arthritis (BA), eight with probable bacterial arthritis (PBA) and eight with osteoarthritis (OA) were studied using the immunoperoxidase staining technique. The oncoproteins studied were expressed both in the synovial lining layer and in the sublining layer, consisting of lymphocytes, other inflammatory cells and blood vessels. Among the six disease entities, RA and OA appeared to be the most distinct, whereas the results obtained for ReA and OSA, and on the other hand for BA and PBA, closely resembled each other. The expression of Myc, Myb, Fos and Jun was significantly correlated both to the degree of synovial hypercellularity and the synovial lymphocytic infiltration. For Ras, such a correlation could not be seen. We conclude that we find no evidence of a cell lineage-specific or a disease-specific abnormality of proto-oncogene products in RA, and the expression of these oncoproteins is consistent with inflammation rather than with any primary abnormality of cell growth.

Expression of bcl-2 in rheumatoid arthritis.

Since defective apoptosis has been suggested to play a role in the development of autoimmune diseases, we have investigated the expression of the proto-oncogene bcl-2 in patients with rheumatoid arthritis (RA). The expression of bcl-2 was studied in peripheral blood (PB) and synovial fluid (SF) lymphocytes and synovial tissues (ST) from patients with RA using immunohistochemistry, flow cytometry and nucleic acid hybridization. Patients with reactive arthritis (ReA) or osteoarthritis (OA) and healthy individuals were used as controls. The expression of bcl-2 protein in PB lymphocytes and the expression of bcl-2 mRNA in PB mononuclear cells (PBMC) was similar in healthy controls and patients with RA. However, bcl-2 protein expression was significantly reduced in SF lymphocytes when compared to PB lymphocytes. Similar results were observed with lymphocytes from patients with ReA, and irrespective of whether total lymphocytes, T cells or different T-cell subsets were studied. In the synovial sections, the expression of bcl-2 was restricted to lymphocytes, and bcl-2+ cells were observed in the majority of samples from patients with RA, OA and ReA. These data indicate that the expression of bcl-2 is not increased in the lymphocytes or ST derived from patients with RA. Instead, decreased expression of bcl-2 protein in SF lymphocytes compared to PB lymphocytes was demonstrated. We suggest that bcl-2 does not play a significant role in the pathogenesis of RA.

Oncogene expression in synovial fluid cells in reactive and early rheumatoid arthritis: a brief report.

Since it has been implied that cellular oncogenes might have a role in the pathogenesis of rheumatoid arthritis (RA), we have examined the expression of c-myc, c-myb, c-fos, c-jun and c-Ha-ras oncogenes in the cells from synovial fluid (SF) and peripheral blood (PB) of patients with reactive arthritis (ReA) and early RA. Oncogene expression was studied using RNA hybridizations with 32P-labelled probes. From the SF, mononuclear and granulocyte cell fractions were used separately. Significant differences between ReA and RA were observed only for c-myb in PB mononuclear cells and c-jun in SF granulocytes. Regarding the expression of c-myc, c-fos and c-Ha-ras oncogenes, no difference between ReA and RA was observed. Comparison to normal controls was made using PB mononuclear cells; only the expression of c-fos tended to be slightly increased in RA, without statistical significance, however. We conclude that oncogene activation in the synovial inflammation is not a phenomenon specific for RA.

Persistence of parvovirus B19 in synovial fluid and bone marrow.

OBJECTIVES: To determine whether parvovirus B19 (B19) persists in rheumatoid arthritis (RA). METHODS: Polymerase chain reaction (PCR) was used to detect parvovirus B19 genome in the synovial fluid cells or peripheral blood mononuclear cells from 61 patients with early RA; bone marrow from one patient was also studied. The synovium or synovial fluid cells from 28 patients with advanced RA, and synovial fluid cell samples from 18 patients with reactive arthritis (as controls) were studied. Two separate sets of primers and probe were used. RESULTS: Parvovirus B19 specific gene sequences were detected in two patients with early arthritis fulfilling the criteria for RA. CONCLUSION: Parvovirus B19 does not play a significant role in the aetiopathogenesis of RA. However, a few cases of a disease indistinguishable from RA may be triggered by parvovirus B19 infection.