Biology subjects

Pelkonen, A.

Publications and source records attributed to Pelkonen, A..

4 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↗

bioRxiv2023

Air-liquid interface culture of midbrain organoids improves neuronal functionality and integration of microglia

Midbrain organoids derived from human induced pluripotent stem cells have emerged as a promising in vitro model for studying the molecular and cellular mechanisms in Parkinsons disease. However, the absence of microglia and the development of a necrotic core in mature organoids have remained key limitations on their utility as functional models of the human midbrain. Here we propose a novel methodology for extended cultivation of midbrain organoid slices, which involves the incorporation of microglia and utilizes an air-liquid culture system. Compared to conventional whole organoids, we found that our model increased the efficacy and consistency of the integration of microglia progenitors. Using single-cell RNA sequencing, we showed that organoid slices maturated in ALI give rise to astrocytes and oligodendrocyte progenitors. Furthermore, the cultivation in air-liquid interface greatly improved neuronal functionality in response to stimulation by NMDA. This stimulation consistently induced robust and stable network activity evaluated by microelectrode array recording. Our newly developed midbrain organoid model with its improved cell type composition and neuronal functionality has potential applications in basic research of Parkinsons disease and in the development of therapeutics. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/561672v1_ufig1.gif" ALT="Figure 1"> View larger version (99K): org.highwire.dtl.DTLVardef@4c8672org.highwire.dtl.DTLVardef@ed3a8org.highwire.dtl.DTLVardef@169bebaorg.highwire.dtl.DTLVardef@168a81c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗