Biology subjects

Rauramaa, T.

Publications and source records attributed to Rauramaa, T..

9 recordsLinked to original sources

bioRxiv2025

Multimodal approach to characterize surgically removed epileptogenic zone from patients with focal drug-resistant epilepsy: from operating room to wet lab

ObjectiveWe have established a comprehensive sample handling protocol designed for the multiscale assessment of epileptogenic tissue. This protocol aims to identify novel therapeutic targets and enhance the diagnosis and stratification of patients with drug-resistant epilepsy, thereby optimizing their treatment with anti-seizure medications and surgical interventions. MethodsPatients with drug-resistant focal epilepsy, recommended for surgical treatment, are recruited after detailed multidisciplinary preoperative evaluation at the Epilepsy Center at Kuopio University Hospital in Finland. A day before the resective surgery, patients undergo magnetic resonance imaging (MRI) including advanced methodologies. During the surgery, each piece of resected tissue is placed under oxygenation on ice-cold artificial cerebral spinal fluid-solution. The pieces are then immediately transported to the laboratory, assessed by a neuropathologist, and sliced for both clinical diagnosis and research. Two adjacent slices are provided for research and are sent to the University of Eastern Finland. ResultsThe developed sample handling protocol provides the opportunity for detailed characterization of the tissue from the same patient using emerging imaging, electrophysiology, and molecular biology technologies. We have optimized the conditions for preserving the resected tissue alive for electrophysiological measurements and simultaneously making possible ex vivo studies including multi-omics acquisition, electron microscopy, histology, and MRI. Our protocol enables the mapping of functional readouts to structural and molecular alterations in human tissue. Our goal is to integrate multimodal data and co-register the resected tissues within the whole brains in vivo MRI space. This approach aims to enhance the characterization and localization of epileptogenic zones and refine surgical treatment targets by identifying abnormalities in global connectivity and structural patterns. SignificanceWe have successfully developed a systematic protocol for the collection and analysis of multimodal data. This protocol aims to elucidate the structural, functional, and molecular characteristics that render tissue epileptogenic, thereby enhancing the diagnosis and subsequent care of patients with epilepsy. Key pointsO_LIIntroducing a systematic sample handling protocol to assess tissue epileptogenicity at structural, functional and molecular levels. C_LIO_LIA multimodal approach integrating advanced technology with detailed characterization of epileptogenic tissue properties to obtain patient-specific data. C_LIO_LICorrelation of data from preoperative MRI and resected tissue to predict tissue pathology from clinical MRI. C_LI

neuroscience↗

bioRxiv2025

Microelectrode array scaled for recording human hippocampal slices

Temporal lobe epilepsy (TLE) is a prevalent neurological disorder characterized by recurrent seizures originating from the cortex, amygdala and especially hippocampus. While two-thirds of TLE patients achieve seizure control through medication, approximately one-third remain refractory to pharmacological interventions. For these individuals, surgical resection offers a potential curative option, with approximately 70% achieving seizure freedom. However, the pathogenesis of TLE remains incompletely understood, necessitating further investigation. Therefore, resected brain tissue obtained during the surgery provides a valuable resource for ex vivo study of pathological neuronal activity. Currently, microelectrode array (MEA) technology is widely used for electrophysiological studies. However, commercially available MEAs are limited in their ability to record from large tissue samples, such as an entire hippocampal section. To address this limitation, we have developed a custom MEA and sample chamber compatible with commercially available headstages. This system enables recording of extracellular action potentials (EAPs) and local field potentials (LFPs) across human hippocampal tissue, providing a valuable tool for investigating the neurophysiological mechanisms underlying TLE. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/640534v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@188e42corg.highwire.dtl.DTLVardef@3c10c6org.highwire.dtl.DTLVardef@17145a5org.highwire.dtl.DTLVardef@19369eb_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIA custom microelectrode array and chamber created for human hippocampal slices C_LIO_LIThe custom array recorded action potentials from human hippocampal slices C_LIO_LIThe custom array recorded local field potentials from human hippocampal slices C_LI

neuroscience↗

bioRxiv2025

Early amyloid spine response and impaired synaptic transmission of pyramidal neurons in human biopsies with Alzheimer's Disease-related pathology

Studies of neuronal functions during the pathological progression of Alzheimers disease (AD) in humans are limited due to the lack of live human brain tissue from patients with AD. To address this gap, we have established an exceptional approach to study the electrophysiological properties and cell morphologies of human neurons in acute slices obtained from cortical biopsies of patients with idiopathic normal pressure hydrocephalus (iNPH). Histological examination of Broadman area 8-9 cortical biopsies from these patients have revealed that approximately 40% of the patients show signs of early AD-related pathology in the form of low to moderate, often fleecy beta-amyloid (A{beta}) deposits and additional, occasional tau in 10% of the cases. Thus, the iNPH brain biopsies, obtained during the shunt surgery to treat the patients, offer a unique window to investigate how existing AD-related pathology alters the operational properties of human cortical neurons. Here we carried out integrative analysis of human neuronal electrophysiology at single neuron and network level followed by subsequent cellular morphological reconstructions to register the primary pathological changes in neuronal functions in correlation with existing AD-related pathology. The presence of A{beta} plaques induced a decrease in basal excitatory synaptic activity in pyramidal neurons residing on supragranular layers of the cortex. These neurons received less of L1-induced inhibition and appeared hyperexcitable in response to application to NMDA in multielectrode array (MEA) recordings. Interestingly, the global spine density of supraganular pyramidal neurons was increased in biopsies with AD-related pathology. The increase in spine density was coincidental with a partial recovery of excitatory transmission (frequency but not amplitude), of L1-induced inhibition in supragranular layers pyramidal neurons and of NMDA induced supragranular firing (but not of bursting hyperexcitability) indicating a potential differential effect of tau in the presence of A{beta} on the progression of neuronal functions. Despite the partial renormalization of deficits seen in cases with A{beta} pathology only, pyramidal neurons in cases with both A{beta} and tau exhibited more consistent deficits in the intrinsic neuronal properties with increase in sodium and potassium currents and a strong propensity to bursting under NMDA stimulation. We conclude that complex mechanisms operate in response to accumulation of A{beta} and tau including re-structuring of the apparatus of synaptic transmission and consolidation of a hyperexcitable supragranular cortical network phenotype. The observed changes in spine density and synaptic activity are reminiscent of parallels seen in homeostatic plasticity and synaptic scaling and may depend on strong interactions with the local microenvironment (astrocytes and microglia). This is the first study to report the impact of AD-related pathology on single-neuron operational properties and morphology in humans.

neuroscience↗

bioRxiv2024

Synapse protein signatures in cerebrospinal fluid and plasma predict cognitive maintenance versus decline in Alzheimers disease

Rates of cognitive decline in Alzheimers disease (AD) are extremely heterogeneous, with ages of symptom onset ranging from age 40-100 years and conversion from mild cognitive impairment to AD dementia taking 2-20 years. Development of biomarkers for amyloid-beta (A{beta}) and tau protein aggregates, the hallmark pathologies of AD, have improved patient monitoring/stratification and drug development, but they still only explain 20-40% of the variance in cognitive impairment (CI) in AD. To discover additional molecular drivers and biomarkers of AD dementia, we perform cerebrospinal fluid (CSF) proteomics on 3,416 individuals from six deeply phenotyped prospective AD case-control cohorts. We identify synapse proteins as the strongest correlates of CI, independent of A{beta} and tau. Using machine learning we derive the CSF YWHAG:NPTX2 synapse protein ratio, a robust correlate of CI, which explains 27% of the variance in CI beyond CSF PTau181:A{beta}42, 10% beyond tau PET, and 50% beyond CSF NfL in A{beta} positive individuals. We find YWHAG:NPTX2 also increases with normal aging as early as age 20 and increases at a faster rate in APOE4 carriers and autosomal dominant-AD mutation carriers. Most notably, YWHAG:NPTX2+ individuals (top 25th percentile) are 15-times (HR=15.4 [10.6-22.2]) more likely to experience cognitive decline over 15 years compared to YWHAG:NPTX2- individuals (bottom 25th percentile), and this rises to 19-times (HR=18.9 [10.83-32.9]) with additional stratification by A{beta} and phosphorylated tau status. Lastly, we perform plasma proteomics on 4,245 individuals to develop a plasma-based signature of CI which partly recapitulates CSF YWHAG:NPTX2. Overall, our findings underscore CSF YWHAG:NPTX2 and the corresponding plasma signature as robust prognostic biomarkers for AD onset and progression beyond gold-standard biomarkers of A{beta}, tau, and neurodegeneration and implicate synapse dysfunction as a core driver of AD dementia.

neuroscience↗

bioRxiv2024

Fibroblasts carrying intermediate C9orf72 hexanucleotide repeat expansions from iNPH patients show impaired energy metabolism but no cell pathologies

Long C9orf72 hexanucleotide repeat expansions (C9-HRE) are the most common genetic cause of frontotemporal dementia (FTD), a group of neurodegenerative syndromes leading to cognitive dysfunction and frontal and temporal atrophy. FTD is a potential comorbidity of idiopathic normal pressure hydrocephalus (iNPH) and carrying the C9-HRE can modify the age-of-onset in iNPH patients. While intermediate-length C9-HRE (<30 repeats) are often considered non-pathogenic, the exact pathological cutoff is unclear. In this study, we assessed whether fibroblasts from iNPH patients carrying intermediate C9-HRE display C9-HRE-associated pathological hallmarks and changes in cellular function. C9-HRE-associated RNA foci were not detected in the intermediate carriers. The number of p62-positive puncta was significantly increased only in long C9-HRE carrier fibroblasts, in line with p62-positive intracellular inclusions observed in a brain biopsy from the patient. Specific parameters of mitochondrial respiration were significantly reduced in both the long and intermediate C9-HRE carrier fibroblasts. Fibroblasts from the intermediate C9-HRE carriers showed upregulated glycolytic activity, possibly to counteract the reduced mitochondrial respiration, which could not be observed in the long C9-HRE carriers. In conclusion, these data suggest that while the long C9-HRE leads to more severe cellular pathologies than intermediate C9-HRE, the latter might predispose cells to pathological changes.

neuroscience↗

bioRxiv2024

Neuronal downregulation of PLCG2 impairs synaptic function and elicits Alzheimer disease hallmarks

We developed a high content screening to investigate how Alzheimer disease (AD) genetic risk factors may affect synaptic mechanisms in rat primary neuronal cultures. Out of the target genes identified, we found that Plcg2 downregulation in mouse dentate gyrus neurons consistently disrupted dendritic morphology and synaptic function. In human neuronal cultures (hNCs), PLCG2 downregulation also impaired synaptic function and increased A{beta} levels and Tau phosphorylation. Very rare PLCG2 loss-of-function (LoF) variants were associated with a 10-fold increased AD risk. PLCG2 LoF carriers exhibit low mRNA/protein PLCG2/PLC{gamma}2 levels and the R953* LoF mutation compromised synaptic function and increased AD hallmarks in hNCs. Single nuclei RNAseq analyses confirmed that the downregulation of PLCG2 impacted pathways related to synaptic and neuronal functions, potentially through neurexin in neurons. In conclusion, PLC{gamma}2 downregulation could increase AD risk by impairing synaptic functions and increasing the A{beta} levels and Tau phosphorylation in neurons.

neuroscience↗

bioRxiv2023

Early Alzheimer's disease pathology in human cortex is associated with a transient phase of distinct cell states

Cellular perturbations underlying Alzheimers disease are primarily studied in human postmortem samples and model organisms. Here we generated a single-nucleus atlas from a rare cohort of cortical biopsies from living individuals with varying degrees of Alzheimers disease pathology. We next performed a systematic cross-disease and cross-species integrative analysis to identify a set of cell states that are specific to early AD pathology. These changes-which we refer to as the Early Cortical Amyloid Response--were prominent in neurons, wherein we identified a transient state of hyperactivity preceding loss of excitatory neurons, which correlated with the selective loss of layer 1 inhibitory neurons. Microglia overexpressing neuroinflammatory-related processes also expanded as AD pathological burden increased. Lastly, both oligodendrocytes and pyramidal neurons upregulated genes associated with amyloid beta production and processing during this early hyperactive phase. Our integrative analysis provides an organizing framework for targeting circuit dysfunction, neuroinflammation, and amyloid production early in AD pathogenesis.

genomics↗

bioRxiv2021

Alzheimer's disease alters astrocytic functions related to neuronal support andtranscellular internalization of mitochondria

Under physiological conditions in vivo astrocytes internalize and degrade neuronal mitochondria in a process called transmitophagy. Mitophagy is widely reported to be impaired in neurodegeneration but it is unknown whether and how transmitophagy is altered in Alzheimers disease (AD). Here we report that the internalization and degradation of neuronal mitochondria are significantly increased in astrocytes isolated from aged AD mouse brains. We also demonstrate for the first time a similar phenomenon between human neurons and AD astrocytes, and in murine hippocampi in vivo. The results suggest the involvement of S100a4 in impaired mitochondrial transfer between neurons and aged AD astrocytes. Significant increases in the mitophagy regulator Ambra1 were observed in the aged AD astrocytes. These findings demonstrate altered neuron-supporting functions of aged AD astrocytes and provide a starting point for studying the molecular mechanisms of transmitophagy in AD.

neuroscience↗

bioRxiv2020

Diabetic phenotype in mouse and humans with β-amyloid pathology reduces the number of microglia around β-amyloid plaques

Type 2 diabetes (T2D) increases the risk of Alzheimers disease (AD). Even though these two diseases share common molecular pathways, the mechanisms remain elusive. To shed light into these mechanisms, mice with different AD- and/or tauopathy-linked genetic backgrounds were utilized; APPswe/PS1dE9 (A+Tw), Tau P301L (AwT+), and APPswe/PS1dE9/Tau P301L (A+T+). Feeding these mice with typical Western diet (TWD) led to obesity and diabetic phenotype as compared to respective mice with a standard diet. TWD also exacerbated memory and learning impairment in A+Tw and AwT+, but not in A+T+ mice. Furthermore, RNA sequencing of mouse hippocampal samples revealed altered responses to AD-related pathologies in A+Tw and A+T+ mice upon TWD, pointing specifically towards aberrant microglial functionality and PI3K-Akt signaling. Accordingly, fewer microglia alongside an increased number of dystrophic neurites around {beta}-amyloid plaques, and impaired PI3K-Akt signaling, were discovered in the hippocampus of TWD mice. Mechanistic elucidation revealed that disruption of the PI3K-Akt signaling pathway by pharmacological or genetic approaches significantly decreased the phagocytic uptake and proinflammatory response as well as increased the activity of Syk-kinase upon ligand-induced activation of Trem2/Dap12 signaling in mouse microglia. Finally, characterization of microglial pathology in cortical biopsies of idiopathic normal pressure hydrocephalus (iNPH) patients harboring {beta}-amyloid plaques revealed a significant decrease in the number of microglia per {beta}-amyloid plaque in obese iNPH patients with T2D as compared to both normal weight and obese iNPH patients without T2D. Collectively, these results suggest that the peripheral diabetic phenotype in mice and humans associates with reduced microglial response to {beta}-amyloid pathology.

neuroscience↗