Tesco, G. | bioRxiv Science

bioRxiv2024

Adenosine deficiency facilitates CA1 synaptic hyperexcitability in the presymptomatic phase of a knock in mouse model of Alzheimer's disease.

The diseases trajectory of Alzheimers disease (AD) is associated with and worsened by hippocampal hyperexcitability. Here we show that during the asymptomatic stage in a knock in mouse model of Alzheimers disease (APPNL-G-F/NL-G-F; APPKI), hippocampal hyperactivity occurs at the synaptic compartment, propagates to the soma and is manifesting at low frequencies of stimulation. We show that this aberrant excitability is associated with a deficient adenosine tone, an inhibitory neuromodulator, driven by reduced levels of CD39/73 enzymes, responsible for the extracellular ATP-to-adenosine conversion. Both pharmacologic (adenosine kinase inhibitor) and non-pharmacologic (ketogenic diet) restorations of the adenosine tone successfully normalize hippocampal neuronal activity. Our results demonstrated that neuronal hyperexcitability during the asymptomatic stage of a KI model of Alzheimers disease originated at the synaptic compartment and is associated with adenosine deficient tone. These results extend our comprehension of the hippocampal vulnerability associated with the asymptomatic stage of Alzheimers disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/590882v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@cd128forg.highwire.dtl.DTLVardef@17d7701org.highwire.dtl.DTLVardef@100337org.highwire.dtl.DTLVardef@14333d0_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LISynaptic hyperexcitability spreads to the soma and manifests at low frequencies of stimulation C_LIO_LISynaptic hyperexcitability is associated with reduced adenosine tone in vitro and in vivo C_LIO_LIReduced adenosine tone is driven by reduced ATP-to-adenosine extracellular conversion C_LIO_LIRestoration of adenosine tone successfully normalizes neuronal excitability in the AD model C_LI

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bioRxiv2022

A 3D bioengineered neural tissue model generated from patient-derived iPSCs develops Alzheimer's disease-related phenotypes

BackgroundCurrent models to study Alzheimers disease (AD) include cell cultures and animal models. Human diseases, however, are often poorly reproduced in animal models. Developing techniques to differentiate human brain cells from induced pluripotent stem cells (iPSCs) provides a novel approach to studying AD. Three-dimensional (3D) cultures to model AD are represented by organoids, neurospheroids, and scaffold-based cultures. Some AD-related phenotypes have been identified across 3D models [1]. However, to our knowledge, none of these studies could recapitulate several AD-related hallmarks in one single model and establish a temporal relation among them. Furthermore, to date, the transcriptomic features of these 3D models have not been compared with those of human AD brains. These data are, in our opinion, key to understanding the pertinency of these models for studying AD-related pathomechanisms over time. MethodsWe developed a 3D bioengineered model of iPSC-derived neural tissue that combines a porous scaffold composed of silk fibroin protein with an intercalated collagen hydrogel to support the growth of neurons and glial cells into complex and functional networks. This biomaterial scaffold, designed to match the mechanical properties of brain tissue, can support 3D neural cultures for an extended time without necrosis, a fundamental requisite for aging studies. We have optimized our protocol by seeding neural precursor cells (NPCs) into these scaffolds. NPC-derived cultures were generated from iPSC lines obtained from two subjects carrying the familial AD (FAD) APP London mutation, two well-studied control lines, and an isogenic control. Cultures were analyzed at 2 and 4.5 months. ResultsAn elevated A{beta}42/40 ratio was detected in conditioned media from FAD cultures at both time points, as previously reported in 2D cultures derived from the same FAD lines. However, extracellular A{beta}42 deposition and enhanced neuronal excitability were observed in FAD culture only at 4.5 months. The increased excitability of FAD cultures correlated with extracellular A{beta}42 deposition but not with soluble A{beta}42/40 ratio levels, as they were similar at both time points. These data suggest that extracellular A{beta} deposition may trigger enhanced network activity. Notably, neuronal hyperexcitability has been described in AD patients early in the disease. Transcriptomic analysis revealed the deregulation of multiple gene sets in FAD samples. Notably, such alterations were similar to those observed in human AD brains in a large study that performed a co-expression meta-analysis of harmonized data from Accelerating Medicines Partnership for Alzheimers Disease (AMP-AD) across three independent cohorts. ConclusionsOur 3D tissue model supports the differentiation of healthy iPSC-derived cultures in a porous silk-collagen composite sponge with an optically clear central region. This design facilitates nutrient delivery to meet the metabolic demand of long-term cultures. These data provide evidence that our bioengineered model from patient-derived FAD iPSCs develops time-dependent AD-related phenotypes and establishes a temporal relation among them. Furthermore, FAD iPSC-derived neuronal tissue recapitulates transcriptomic features of AD patients. Thus, our bioengineered neural tissue represents a unique tool to model AD-related pathomechanisms over time, with several advantages compared to the existing models.

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