A flexible open-source processing workflow for multiplexed fluorescence imaging based on cycles

International audienceBackground Multiplexing tissue imaging is developing as a complement for single cell analysis, bringing the spatial information of cells in tissue in addition to multiple parameters measurements. More and more commercial or home-made systems are available. These techniques allow the imaging of tens of fluorescent reporters, where the spectral overlap is solved by imaging by cycles the fluorophores using microfluidics to change the reporters between each cycle. Methods For several systems, the acquisition system coupled to the microfluidic system is a wide field microscope, and the acquisition process is done by mosaicking to cover a large field of view, relying on image processing to obtain the data set to be analysed in intensity. The processed data set allows the identification of different populations, quite similarly to cytometry analysis, but with spatial information in addition. To obtain the final image for analysis from the raw acquisitions, several preprocessing steps are needed for inter-cycle registration, tissue autofluorescence correction or mosaicking. We propose a workflow for this preprocessing, implemented as an open source software (as a library, command line tool and standalone). Results We exemplify the workflow on the commercial system PhenoCycler® (formerly named CODEX®) and provide a reduced size data set for testing. Conclusions We compare our processor with the commercially provided processor and show that we solve some problems also reported by other users

Expression of Phenotypic Astrocyte Marker Is Increased in a Transgenic Mouse Model of Alzheimer's Disease versus Age-Matched Controls: A Presymptomatic Stage Study.

Recent mouse studies of the presymptomatic stage of Alzheimer's disease (AD) have suggested that proinflammatory changes, such as glial activation and cytokine induction, may occur already at this early stage through unknown mechanisms. Because TNFα contributes to increased Aβ production from the Aβ precursor protein (APP), we assessed a putative correlation between APP/Aβ and TNFα during the presymptomatic stage as well as early astrocyte activation in the hippocampus of 3-month-old APPswe/PS1dE9 mice. While Western blots revealed significant APP expression, Aβ was not detectable by Western blot or ELISA attesting that 3-month-old, APPswe/PS1dE9 mice are at a presymptomatic stage of AD-like pathology. Western blots were also used to show increased GFAP expression in transgenic mice that positively correlated with both TNFα and APP, which were also mutually correlated. Subregional immunohistochemical quantification of phenotypic (GFAP) and functional (TSPO) markers of astrocyte activation indicated a selective and significant increase in GFAP-immunoreactive (IR) cells in the dentate gyrus of APPswe/PS1dE9 mice. Our data suggest that subtle morphological and phenotypic alterations, compatible with the engagement of astrocyte along the activation pathway, occur in the hippocampus already at the presymptomatic stage of AD

Neuroprotective effect of the alpha 7 nicotinic receptor agonist PHA 543613 in an in vivo excitotoxic adult rat model

International audienceNeuroinflammation is a key component of the pathophysiology of neurodegenerative diseases. The link between nicotine intake and positive outcome has been established, suggesting a role played by nicotinic receptors (nAChRs), especially α7nAChRs. The objective of this study was to evaluate the potential dose effects of PHA 543613 on neuron survival and striatal microglial activation in a rat model of brain excitotoxicity. A preliminary study was performed in vitro to confirm PHA 543613 agonist properties on α7nAChRs. Rats were lesioned in the right striatum with quinolinic acid (QA) and received either vehicle or PHA 543613 at 6 or 12 mg/kg twice a day until sacrifice at Day 4 post-lesion. We first compared the translocator protein quantitative autoradiography in QA-lesioned brains with [3H]DPA-714 and [3H]PK-11195. The effects of PHA 543613 on microglial activation and neuronal survival were then evaluated through [3H]DPA-714 binding and immunofluorescence staining (Ox-42, NeuN) on adjacent brain sections. We demonstrated that [3H]DPA-714 provides a better signal-to-noise ratio than [3H]PK-11195. Furthermore, we showed that repeated PHA 543613 administration at a dose of 12 mg/kg to QA-lesioned rats significantly protected neurons and reduced the intensity of microglial activation. This study reinforces the hypothesis that α7nAChR agonists can provide beneficial effects in the treatment of neurodegenerative diseases through potential modulation of microglial activation

Detection of Neuroinflammation in a Rat Model of Subarachnoid Hemorrhage Using [F]DPA-714 PET Imaging

Subarachnoid hemorrhage (SAH) can lead to delayed cerebral ischemia, which increases the rate of morbidity and mortality. The detection of microglial activation may serve as a biomarker for the identification of patients at risk of this deleterious consequence. We assessed this hypothesis in a rat model of SAH in which the exploration of neuroinflammation related to microglial activation was correlated with the degree of bleeding. We used the rat filament model and evaluated (at 48 hours postsurgery) the intensity of neuroinflammation using positron emission tomography (PET) imaging with the 18-kDa translocator protein (TSPO) tracer [ 18 F]DPA-714, quantitative autoradiography with [ 3 H]PK-11195, and SAH grade by postmortem brain picture. High SAH grades were strongly and positively correlated with in vivo PET imaging of TSPO in the cortex and striatum. In addition, a positive correlation was found in the cortex in TSPO, with densities determined by imaging and autoradiographic approaches. Qualitative immunofluorescence studies indicated that overexpression of TSPO was linked to astrocytic/microglial activation. In this model, PET imaging of TSPO using [ 18 F]DPA-714 appeared to be a relevant index of the degree of bleeding, indicating that this imaging method could be used in human patients to improve the management of patients with SAH

Identification of the allosteric P2X₇ receptor antagonist [¹¹C]SMW139 as a PET tracer of microglial activation

The P2X7 receptor plays a significant role in microglial activation, and as a potential drug target, the P2X7 receptor is also an interesting target in positron emission tomography. The current study aimed at the development and evaluation of a potent tracer targeting the P2X7 receptor, to which end four adamantanyl benzamide analogues with high affinity for the human P2X7 receptor were labelled with carbon-11. All four analogues could be obtained in excellent radiochemical yield and high radiochemical purity and molar activity, and all analogues entered the rat brain. [11C]SMW139 showed the highest metabolic stability in rat plasma, and showed high binding to the hP2X7 receptor in vivo in a hP2X7 receptor overexpressing rat model. Although no significant difference in binding of [11C]SMW139 was observed between post mortem brain tissue of Alzheimer's disease patients and that of healthy controls in in vitro autoradiography experiments, [11C]SMW139 could be a promising tracer for P2X7 receptor imaging using positron emission tomography, due to high receptor binding in vivo in the hP2X7 receptor overexpressing rat model. However, further investigation of both P2X7 receptor expression and binding of [11C]SMW139 in other neurological diseases involving microglial activation is warranted