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Cellular communication is a concept that can be explained as the transfer of signals or material (such as cytokines, ions, small molecules) between cells from the same or different type, across either short or long distances. Once this signal or material is received, it will, as a rule, promote a functional effect. Several routes, involved in this transfer, are well described and are of global importance for organ/tissue communication in an organism.
The brain interacts dynamically with the immune system, and the main route known to mediate this communication, is via the release of cytokines (by peripheral blood cells), which can then activate certain brain cell types, such as microglia, directly, or activate the vagus nerve transferring signals to neuronal populations in the brain. The communication between these two systems plays a key role in the pathophysiology of neurodegenerative diseases, and the mechanisms involved in this interaction are of central importance for understanding disease initiation and progression and search for therapeutic models.
The Momma lab previously addressed the mechanisms of interaction between the peripheral immune system and the brain by investigating cellular fusion of haematopoietic cells with neurons after inflammation. They addressed the question of whether this phenomenon also occurs under non-invasive conditions. To approach this problem, a genetic tracing model that relies on the Cre-Lox recombination system was used. Transgenic mice expressing Cre recombinase specifically in the haematopoietic lineage were crossed into a Cre-reporter background, thus all haematopoietic cells irreversibly express the reporter marker-gene EYFP. Using this model, EYFP was detected in non-haematopoietic tissues, suggesting the existence of a communication mechanism never described before. As cells containing two nuclei were never detected, fusion as a mechanism was excluded, suggesting that Cre reaches non-haematopoietic cells via a different signalling pathway. The Momma lab investigated whether the transfer of material through extracellular vesicles (EVs) could be behind this periphery-to-brain communication. Using the genetic mouse model, they were able to trace the transfer of Cre RNA via EVs between cells in vivo, generating the first in vivo evidence of functional RNA transfer by EVs between blood and brain.
The last decade has witnessed a rapid expansion of the field of EVs. Initially considered as waste disposal material, recent evidence has challenged this view. EVs are currently considered as a widespread intercellular communication system that can transport and transfer all types of biomolecules, from nucleic acids to lipids and proteins. However, several important questions are still under investigation. One of them is whether EVs are involved in brain pathophysiology, as inflammation plays an important role in onset and progression of neurodegenerative diseases and is well described in Parkinson Disease (PD). Based on preliminary data in a mouse, peripherally injected with a low dose of Lipopolysaccharide (LPS, an endotoxin found in the outer-membrane of Gram-negative bacteria, which causes an immune response), neurons and other cell population in the brain take up EVs from the periphery. Particularly, dopaminergic neurons from Substantia Nigra and Ventral Tegmental Area have been shown to receive functional RNA, transported through EVs, which can lead up to 20% of recombination. Furthermore, different neuronal populations from Hippocampus, Cortex and Cerebellum exhibit recombination, indicating a widespread signalling from blood to the brain. Therefore, the goal of my PhD thesis was to investigate the mechanisms of this transfer and the triggers that lead to EV uptake by neural cells in vivo both in pathological and physiological conditions.
In this project, the extent and function of EV-mediated signalling from blood to brain is explored in the context of peripheral inflammation and neurodegenerative diseases. Firstly, EVs isolated from WT mice were further characterized using size-exclusion chromatography (SEC), Western Blot (WB) and electron microscopy in order to extend the knowledge from previous work done in the Momma lab. Secondly, to expand on the biological relevance of the fact that inflammation is correlated with an increase in EV uptake, different approaches using the genetic murine tracing model were used. Recombination events from haematopoietic cells to the brain have been followed after peripheral injection of LPS. Peripheral inflammation caused by LPS injection led to widespread recombination events in the brain, specifically in microglia and neurons, including dopaminergic (DA) neurons. In contrast, astrocytes, oligodendrocytes and endothelial cells were never or very rarely recombined. Additionally, peripheral LPS injection in a murine model, where Cre is expressed only in erythrocytes, led to recombination events only in microglia, suggesting that the type of EV-secreting cell plays a role in the targeting of EVs to a specific cell population.
Background: To study neoadjuvant chemoradiotherapy (nCRT) and potential predictive factors for response in locally advanced oral cavity cancer (LA-OCC).
Methods: The INVERT trial is an ongoing single-center, prospective phase 2, proof-of-principle trial. Operable patients with stage III-IVA squamous cell carcinomas of the oral cavity were eligible and received nCRT consisting of 60 Gy with concomitant cisplatin and 5-fluorouracil. Surgery was scheduled 6-8 weeks after completion of nCRT. Explorative, multiplex immunohistochemistry (IHC) was performed on pretreatment tumor specimen, and diffusion-weighted magnetic resonance imaging (DW-MRI) was conducted prior to, during nCRT (day 15), and before surgery to identify potential predictive biomarkers and imaging features. Primary endpoint was the pathological complete response (pCR) rate.
Results: Seventeen patients with stage IVA OCC were included in this interim analysis. All patients completed nCRT. One patient died from pneumonia 10 weeks after nCRT before surgery. Complete tumor resection (R0) was achieved in 16/17 patients, of whom 7 (41%, 95% CI: 18-67%) showed pCR. According to the Clavien-Dindo classification, grade 3a and 3b complications were found in 4 (25%) and 5 (31%) patients, respectively; grade 4-5 complications did not occur. Increased changes in the apparent diffusion coefficient signal intensities between MRI at day 15 of nCRT and before surgery were associated with better response (p=0.022). Higher abundances of programmed cell death protein 1 (PD1) positive cytotoxic T-cells (p=0.012), PD1+ macrophages (p=0.046), and cancer-associated fibroblasts (CAFs, p=0.036) were associated with incomplete response to nCRT.
Conclusion: nCRT for LA-OCC followed by radical surgery is feasible and shows high response rates. Larger patient cohorts from randomized trials are needed to further investigate nCRT and predictive biomarkers such as changes in DW-MRI signal intensities, tumor infiltrating immune cells, and CAFs.
Communication with the hematopoietic system is a vital component of regulating brain function in health and disease. Traditionally, the major routes considered for this neuroimmune communication are by individual molecules such as cytokines carried by blood, by neural transmission, or, in more severe pathologies, by the entry of peripheral immune cells into the brain. In addition, functional mRNA from peripheral blood can be directly transferred to neurons via extracellular vesicles (EVs), but the parameters that determine their uptake are unknown. Using varied animal models that stimulate neuronal activity by peripheral inflammation, optogenetics, and selective proteasome inhibition of dopaminergic (DA) neurons, we show that the transfer of EVs from blood is triggered by neuronal activity in vivo. Importantly, this transfer occurs not only in pathological stimulation but also by neuronal activation caused by the physiological stimulus of novel object placement. This discovery suggests a continuous role of EVs under pathological conditions as well as during routine cognitive tasks in the healthy brain.
Cancer is the second leading cause of mortality worldwide. Despite recent advances in cancer treatment including immunotherapy with immune checkpoint inhibitors, new unconventional biomarkers and targets for the detection, prognosis, and treatment of cancer are still in high demand. Tumor cells are characterized by mutations that allow their unlimited growth, program their local microenvironment to support tumor growth, and spread towards distant sites. While a major focus has been on altered tumor genomes and proteomes, crucial signaling molecules such as lipids have been underappreciated. One of these molecules is the membrane phospholipid phosphatidylserine (PS) that is usually found at cytosolic surfaces of cellular membranes but can be rapidly and massively shuttled to the extracellular leaflet of the plasma membrane during apoptosis to serve as a limiting factor for immune responses. These immunosuppressive interactions are exploited by tumor cells to evade the immune system. In this review, we describe mechanisms of immune regulation in tumors, discuss if PS may constitute an inhibitory immune checkpoint, and describe current and future strategies for targeting PS to reactivate the tumor-associated immune system.