Exploring macrophage mannose receptor expression after myocardial infarction by Al[18F]F-NOTA-DCM positron emission tomography

Introduction

Mannose receptor (CD206) is primarily expressed on the surface of alternatively activated macrophages that are involved in resolution of inflammation after myocardial injury [1]. The purpose of this study was to evaluate mannose receptor targeting positron emission tomography (PET) tracer Al[18F]F-NOTA-DCM consisting of dextran backbone with cysteine-mannose moieties for imaging of experimental acute myocardial infarction (MI) [2].

Methods

First, ALEXA-488 fluorophore-labelled DCM was used for specificity studies using flow cytometry of M1 and M2 polarized macrophages derived from human blood monocytes. Secondly, Sprague-Dawley rats were studied on day 3 and day 7 after permanent ligation of left coronary artery or after sham-operation. [18F]FDG PET (35 MBq, 10 min static scan) was performed to visualize myocardium and on the next day, 60 min dynamic PET was performed after injection of 50 MBq of Al[18F]F-NOTA-DCM. Then, rats were euthanized for biodistribution study by gamma counting followed by digital autoradiography and histology (H&E, CD206 staining) of left ventricle cryosections. In vitro Al[18F]F-NOTA-DCM blocking study was performed on left ventricle cryosection with molar excess of unlabelled DCM.

Results

Flow cytometry confirmed that ALEXA-488-DCM bound specifically to M2 macrophages. In rats, the infarcted area was clearly detected in vivo with Al[18F]F-NOTA-DCM PET and its SUV was significantly higher than that of remote area or myocardium of sham-operated rats both on day 3 (SUV 0.78±0.18 vs. 0.47±0.13 vs. 0.43±0.07, p<0.005) and day 7 post-MI (SUV 0.64±0.10 vs. 0.47±0.12 vs. 0.51±0.07, p<0.05). Autoradiography confirmed increased uptake in the infarcted area compared to the remote area or to the myocardium of sham-operated rats on day 3 (PSL/mm2 141.21±46.06 vs. 49.76±20.37 vs. 57.97±6.77, p<0.005) and day 7 (PSL/mm2 139.22±19.44 vs. 55.38±28.83 vs. 60.83±7.63, p<0.0001). In vitro blocking study indicated that the tracer binding in infarcted area was specific. The area-% of CD206-positive staining in the infarcted area was significantly higher on day 3 post-MI than on day 7 (p<0.05), and higher at both time points than in remote area or myocardium of sham-operated rats (p<0.0001). Area-% of CD206 staining in the MI area positively correlated with Al[18F]F-NOTA-DCM uptake and MI size (p<0.05 and p<0.01, respectively).

Conclusions

Al[18F]F-NOTA-DCM PET detects overexpression of mannose receptor after ischemic myocardial injury and may be a suitable biomarker for early detection of the inflammation resolution process after MI.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Jane and Aatos Erkko FoundationSigrid Juselius FoundationFInnish Foundation for Cardiovascular Research

Cholinergic dysfunction after traumatic brain injury: preliminary findings from a PET study

OBJECTIVE

There is evidence that the cholinergic system is frequently involved in the cognitive consequences of traumatic brain injury (TBI). We studied whether the brain cholinergic function is altered after TBI in vivo using PET.

METHODS

Cholinergic function was assessed with [methyl-(11)C]N-methylpiperidyl-4-acetate, which reflects the acetylcholinesterase (AChE) activity, in 17 subjects more than 1 year after a TBI and in 12 healthy controls. All subjects had been without any centrally acting drugs for at least 4 weeks.

RESULTS

The AChE activity was significantly lower in subjects with TBI compared to controls in several areas of the neocortex (-5.9% to -10.8%, p=0.053 to 0.004).

CONCLUSIONS

Patients with chronic cognitive symptoms after TBI show widely lowered AChE activity across the neocortex.

306 EMBRYO ANALYSIS IN FIELD MOET: HIGH SUCCESS RATE AFTER OVERNIGHT CULTURE OF MICROBLADE-BIOPSIED CATTLE EMBRYOS

Embryo storage before embryo transfer is a necessity in field MOET to enable complex embryo analysis. Cryopreservation of biopsied embryos may reduce pregnancy rates to unacceptable levels, below 40% (Shea BF 1999 Theriogenology 51, 841–854). Our primary objective was to investigate the effect of short-term storage in overnight culture on the pregnancy rate of microblade-biopsied and sexed cattle embryos. A specific aim was to apply embryo storage in culture to marker-assisted selection of MOET embryos. Day 6.5 embryos were produced using standard superovulatory, AI, and embryo flushing procedures. Embryo donors were lactating cows of top genetic merit. Embryos were transported in straws in Holding medium (ICPbio, Auckland, New Zealand) to the laboratory and individually biopsied by a microblade. Biopsied embryos were cultured overnight in individual oil-overlaid 20-μL drops of Medium 199 with glutamax-1 (GIBCOTM, Baisley, UK) containing 0.25 mM sodium pyruvate, antibiotics, and 4 mg mL−1 fatty acid-free albumin. The biopsies were lysed in proteinase K and analyzed for sex with the BOV-Y/kappa-casein PCR method (Peura et al. 1991 Theriogenology 35, 547–555). Overnight-cultured grade I–II female embryos were transferred into the uteri of heat-synchronized recipients (Day 7.5). Pregnancy was confirmed by rectal palpation at 2–3 months after ET. Grade I-II male embryos as well as embryos of unknown sex were frozen in ethylene glycol, stored in liquid nitrogen, thawed, and cultured overnight for estimation of re-expansion rate and cell counts. In total, 74 embryos of eight donors were overnight-cultured and sexed. The success rate of the sexing method was 95%. Of the successfully analyzed embryos, 41% (29 of 70) were females and 59% (59 of 70) males. The survival rate of microblade-biopsied overnight-cultured embryos was 99% (73 of 74); 73% of the surviving embryos were of grade I, 23% of grade II, and 4% of grade III. Sixteen of the 27 (59%) grade I–II female embryos transferred resulted in pregnancy. Forty-two grade I–II embryos were frozen and 36 (86%) re-expanded after thawing and overnight culture. Twenty-four of the re-expanded embryos (67%) were of grade I. The re-expanded embryos had on average 73 cells (range 43–114). In conclusion, overnight culture of microblade-biopsied cattle embryos does not compromise embryo viability, resulting in high pregnancy rate and post-thaw re-expansion rate. The method can be utilized as a short-term embryo storage in the field MOET scheme and it will be applied in marker-assisted selection of MOET embryos for genotypes associated with milk production. The study was supported by the HAKA-Top breeding animals from North-Savo-project.

Quantitative Trait Loci for Health Traits in Finnish Ayrshire Cattle

A whole-genome scan was conducted to search for quantitative trait loci (QTL) affecting health traits in Finnish Ayrshire dairy cattle. The mapping population consisted of 12 bulls and their 491 sons in a granddaughter design. A total of 150 markers were typed covering all 29 autosomes. The traits under study were somatic cell score, mastitis, and a group of other veterinary treatments. Effects of the QTL and positions were estimated with the regression method. When carrying out interval mapping on each chromosome, cofactors were used to adjust for QTL identified at other chromosomes. Empirical P-values were obtained by permutation. Altogether 17 QTL were detected with genomewise significant P-values in the across family analysis. Quantitative trait loci affecting SCS were identified on chromosomes 1, 3, 11, 18, 21, 24, 27, 29, and QTL for mastitis on chromosomes 14, 18. Quantitative trait loci for other veterinary treatments were found on chromosomes 1, 2, 5, 8, 15, 22, and 23. The allele substitution effects were from 0.5 to 1.7 genetic standard deviations. The positions of these health QTL did not overlap with milk QTL detected in previous studies of the same population.

Quantitative trait loci affecting milk production traits in Finnish Ayrshire dairy cattle

A whole genome scan of Finnish Ayrshire was conducted to map quantitative trait loci (QTL) affecting milk production. The analysis included 12 half-sib families containing a total of 494 bulls in a granddaughter design. The families were genotyped with 150 markers to construct a 2764 cM (Haldane) male linkage map. In this study interval mapping with multiple-marker regression approach was extended to analyse multiple chromosomes simultaneously. The method uses identified QTL on other chromosomes as cofactors to increase mapping power. The existence of multiple QTL on the same linkage group was also analyzed by fitting a two-QTL model to the analysis. Empirical values for chromosome-wise significance thresholds were determined using a permutation test. Two genome-wise significant QTL were identified when chromosomes were analyzed individually, one affecting fat percentage on chromosome (BTA) 14 and another affecting fat yield on BTA12. The cofactor analysis revealed in total 31 genome-wise significant QTL. The result of two-QTL analysis suggests the existence of two QTL for fat percentage on BTA3. In general, most of the identified QTL confirm results from previous studies of Holstein-Friesian cattle. A new QTL for all yield components was identified on BTA12 in Finnish Ayrshire.

Sex determination of bovine embryo blastomeres by fluorogenic probes

One of the major challenges of using genetic information in marker assisted selection (MAS) is the detection of multiple marker loci from a small biopsy sample of a preimplantation stage embryo. The objective of this study was to develop a fast, nested, multiplex preamplification, polymerase chain reaction (PCR) method for the determination of sex in bovine embryo blastomeres. For this aim, ZFX/ZFY sequences were preamplified simultaneously with other genomic regions. The preamplification product was used as a template in an allelic discrimination assay, with nested primers and sex specific fluorogenic probes for ZFX and ZFY. Fluorogenic probes were used to eliminate the need for time consuming electrophoresis. Compared to sexing with Bovy/kappa-casein co-amplification method and other replicates from the same embryo, the accuracy of sexing with the use of fluorogenic probes after preamplification was 99% (112/113 blastomeres). The amplification efficiency was 96% (113/117 blastomeres).