Biology subjects

Kokaia, Z.

Publications and source records attributed to Kokaia, Z..

10 recordsLinked to original sources

bioRxiv2025

Intracortical transplantation of human induced pluripotent stem cell-derived progenitors ameliorates delayed thalamic degeneration following cortical stroke

Cortical ischemic stroke can trigger secondary neurodegeneration in remote brain regions connected to the primary lesion, particularly the thalamus. Although secondary thalamic degeneration is well established, the temporal relationship among early disruption of the thalamocortical pathway, neuronal degeneration, neuroinflammation, and delayed thalamic atrophy remains incompletely defined. Here, we investigated the longitudinal progression of secondary thalamic degeneration after cortical stroke, with particular emphasis on diffusion MRI tractography to monitor changes in anatomically defined thalamocortical pathways. We further determined whether early intracortical transplantation of human induced pluripotent stem cell (hiPSC)-derived neuronal progenitors could protect the remote thalamus and preserve thalamocortical connectivity.Cortical ischemic stroke was induced by distal middle cerebral artery occlusion in rats, and animals were assessed at multiple time points up to 6 months after stroke using longitudinal volumetric MRI and diffusion MRI tractography, combined with histological analyses of neuronal degeneration and microglial activation. The cortical infarct was established within 3-4 days, whereas alterations in diffusion metrics of thalamocortical pathways were detected within the first days after stroke. Neuronal degeneration in the ipsilateral ventral posterior nucleus (VPN) was evident at 2 weeks and preceded measurable VPN atrophy, which began at 3 months. Microglial activation also peaked at 2 weeks, coinciding with the onset of neuronal degeneration. Early intracortical transplantation of cortically primed hiPSC-derived neuronal progenitors 48 h after stroke did not alter cortical infarct volume but preserved VPN neurons, reduced subsequent thalamic atrophy, and maintained diffusion properties of affected thalamocortical pathways.These findings define secondary thalamic degeneration as a temporally ordered process in which early alterations in the thalamocortical pathway precede neuronal loss and delayed structural atrophy. Importantly, longitudinal tractography monitored both cortical stroke-induced thalamocortical degeneration and its modification by hiPSC-derived neuronal transplantation, establishing an in vivo approach to assess remote circuit degeneration and transplantation-dependent neuroprotection after cortical stroke.

neuroscience↗

bioRxiv2025

Rapid and efficient generation of human oligodendrocytes myelinating adult human cortical neurons

Intracerebral transplantation of stem cell-derived oligodendrocytes (OLs) is a promising strategy for repairing demyelinated human brain tissue, the main hallmark of white-matter disorders. However, several challenges hinder clinical translation, including slow or inefficient production of human OLs with current protocols, and difficulty in generating pure OL grafts capable of remyelinating injured neural circuits. Here, we present a robust, highly reproducible method for the rapid and efficient production of human OLs from human induced pluripotent stem cell derived long-term neuroepithelial-like stem (lt-NES) cells. Induced expression of the lineage-defining transcription factors SOX10 and OLIG2 in lt-NES cells is sufficient to generate a population of 80% OLs within 7 days. Importantly, these cells survive, differentiate and form functional OL-exclusive grafts when transplanted into adult human brain slices ex vivo, constituting the first demonstration that an OL-exclusive graft with robust myelination capacity can be generated in a clinically relevant allogeneic environment. This advance marks a significant step towards the clinical application of oligodendrocyte replacement therapy for human demyelinating disorders.

neuroscience↗

bioRxiv2024

Human cortical neurons rapidly generated by direct ES cell programming integrate into stroke-injured rat cortex

Stroke is a major cause of long-term disability in adult humans, the neuronal loss leading to motor, sensory, and cognitive impairments. Replacement of dead neurons by intracerebral transplantation of stem cell-derived neurons for reconstruction of injured neuronal networks has potential to become a novel therapeutic strategy to promote functional recovery after stroke. Here we describe a rapid and efficient protocol for the generation of cortical neurons via direct programming of human embryonic stem (hES) cells. Our results show that 7 days overexpression of the transcription factor neurogenin 2 (NGN2) in vitro was enough to generate hES-induced cells with cortical phenotype, as revealed by immunocytochemistry and RT-qPCR, and electrophysiological properties of neurons in an intermediate stage of maturity. At 3 months after translantation into the stroke-injured rat cortex, the hES-induced neurons (hES-iNs) showed immunocytochemical markers of mature layer-specific cortical neurons and sent widespread axonal projections to several areas in both hemispheres of the host brain. Their axons became myelinated and formed synaptic contacts with host neurons, as shown by immunoelectron microscopy. Our findings demonstrate for the first time that direct transcription factor programming of hES cells can efficiently and rapidly produce cortical neurons with capacity to integrate into the stroke-injured brain.

neuroscience↗

bioRxiv2024

Human monocyte subtype expression of neuroinflammation and -regeneration-related genes is linked to age and sex

Stroke is a leading cause of disability and the third cause of death. The immune system plays an essential role in post-stroke recovery. After an ischemic stroke, monocytes infiltrate the injured brain tissue and can exacerbate or mitigate the damage. Ischemic stroke is more prevalent in the aged population, and the aging brain exhibits an altered immune response. There are also sex disparities in ischemic stroke incidence, outcomes, and recovery, and these differences may be hormone-driven and determined by genetic and epigenetic factors. Here, we studied whether human peripheral blood monocyte subtype (classical, intermediate, and non-classical) expression of neuronal inflammation- and regeneration-related genes depends on age and sex. A FACS analysis of blood samples from 44 volunteers (male and female, aged 28 to 98) showed that in contrast to other immune cells, the proportion of natural killer cells increased in females. The proportion of B-cells decreased in both sexes with age, and subtypes of monocytes were not linked to age or sex. Gene expression analysis by qPCR identified several genes differentially correlating with age and sex within different monocyte subtypes. Interestingly, ANXA1 and CD36 showed a consistent increase with aging in all monocytes, specifically in intermediate (CD36) and intermediate and non-classical (ANXA1) subtypes. Other genes (IL-1{beta}, S100A8, TNF, CD64, CD33, TGF{beta}1, TLR8, CD91) were differentially changed in monocyte subtypes with increased aging. Most age-dependent gene changes were differentially expressed in female monocytes. Our data shed light on the nuanced interplay of age and sex in shaping the expression of inflammation- and regeneration-related genes within distinct monocyte subtypes. Understanding these dynamics could pave the way for targeted interventions and personalized approaches in post-stroke care, particularly for the aging population and individuals of different sexes.

neuroscience↗

bioRxiv2023

DNA methylation governs the sensitivity of repeats to restriction by the HUSH-MORC2 corepressor

The human silencing hub (HUSH) complex binds to transcripts of LINE-1 retrotransposons (L1s) and other genomic repeats, recruiting MORC2 and other effectors to remodel chromatin. However, how HUSH and MORC2 operate alongside DNA methylation, a central epigenetic regulator of repeat transcription, remains poorly understood. Here we interrogate this relationship in human neural progenitor cells (hNPCs), a somatic model of brain development that tolerates removal of DNA methyltransferase DNMT1. Upon loss of MORC2 or HUSH subunit TASOR in hNPCs, L1s remain silenced by robust promoter methylation. However, genome demethylation and activation of evolutionarily-young L1s attracts MORC2 binding. Simultaneous depletion of DNMT1 and MORC2 causes massive accumulation of L1 transcripts. We identify the same mechanistic hierarchy at pericentromeric -satellites and clustered protocadherin genes, repetitive elements important for chromosome structure and neurodevelopment respectively. Our data delineate the independent epigenetic control of repeats in somatic cells, with implications for understanding the vital functions of HUSH-MORC2 in hypomethylated contexts throughout human development.

molecular biology↗

bioRxiv2023

Oligodendrocytes in human iPS cell-derived cortical grafts remyelinate adult rat and human cortical neurons

Neuronal loss and axonal demyelination underlie long-term functional impairments in patients affected by brain disorders such as ischemic stroke. Stem cell-based approaches reconstructing and remyelinating brain neural circuitry, leading to recovery, are highly warranted. Here we demonstrate the in vitro and in vivo production of myelinating oligodendrocytes from a human induced pluripotent stem (iPS) cell-derived long-term neuroepithelial stem (lt-NES) cell line, which also gives rise to neurons with the capacity to integrate into stroke-injured, adult rat cortical networks. Most importantly, the generated oligodendrocytes survive and form myelin ensheathing human axons in the host tissue after grafting onto adult human cortical organotypic cultures. This lt-NES cell line is the first human stem cell source that after intracerebral delivery can repair both injured neural circuitries and demyelinated axons. Our findings provide supportive evidence for the potential future use of human iPS cell-derived cell lines to promote effective clinical recovery following brain injuries.

neuroscience↗

bioRxiv2023

L1 retrotransposons drive human neuronal transcriptome complexity and functional diversification

The genetic mechanisms underlying the expansion in size and complexity of the human brain remains poorly understood. L1 retrotransposons are a source of divergent genetic information in hominoid genomes, but their importance in physiological functions and their contribution to human brain evolution is largely unknown. Using multi-omic profiling we here demonstrate that L1-promoters are dynamically active in the developing and adult human brain. L1s generate hundreds of developmentally regulated and cell-type specific transcripts, many which are co-opted as chimeric transcripts or regulatory RNAs. One L1-derived lncRNA, LINC01876, is a human-specific transcript expressed exclusively during brain development. CRISPRi-silencing of LINC01876 results in reduced size of cerebral organoids and premature differentiation of neural progenitors, implicating L1s in human-specific developmental processes. In summary, our results demonstrate that L1-derived transcripts provide a previously undescribed layer of primate- and human-specific transcriptome complexity that contributes to the functional diversification of the human brain.

neuroscience↗

bioRxiv2020

Pericyte-derived fibrotic scarring is conserved across diverse central nervous system lesions

Fibrotic scar tissue limits central nervous system regeneration in adult mammals. The extent of fibrotic tissue generation and distribution of stromal cells across different lesions in the brain and spinal cord has not been systematically investigated in mice and humans. Furthermore, it is unknown whether scar-forming stromal cells have the same origin throughout the central nervous system and in different types of lesions. In the current study, we compared fibrotic scarring in human pathological tissue and corresponding mouse models of penetrating and non-penetrating spinal cord injury, traumatic brain injury, ischemic stroke, multiple sclerosis and glioblastoma. We show that the extent and distribution of stromal cells are specific to the type of lesion and, in most cases, similar between mice and humans. Employing in vivo lineage tracing, we report that in all mouse models developing fibrotic tissue, the primary source of scar-forming fibroblasts is a discrete subset of perivascular cells, termed type A pericytes. We uncover pericyte-derived fibrosis as a conserved mechanism that may be explored as a therapeutic target to improve recovery after central nervous system lesions.

neuroscience↗

bioRxiv2020

Cancer-associated HIF-2α impacts trunk neural crest stemness

The neural crest is a stem cell population that gives rise to sympathetic ganglia, the cell type of origin of neuroblastoma. Hypoxia Inducible Factor (HIF)-2 is associated with high risk neuroblastoma, however, little is known about its role in normal neural crest development. To address this important question, here we show that HIF-2 is expressed in trunk neural crest cells of human, murine and avian embryos. Modulating HIF-2 in vivo not only causes developmental delays but also induces proliferation and stemness of neural crest cells while altering the number of cells migrating ventrally to sympathoadrenal sites. Transcriptome changes after loss of HIF-2 reflect the in vivo phenotype. The results suggest that expression levels of HIF-2 must be strictly controlled and abnormal levels increase stemness and may promote metastasis. Our findings help elucidate the role of HIF-2 during normal development with implications also in tumor initiation at the onset of neuroblastoma.

developmental biology↗

bioRxiv2018

HSCs contribute actively to native multilineage hematopoiesis but with reduced differentiation capacity upon aging

A hallmark of adult hematopoiesis is the continuous replacement of blood cells with limited lifespans. It is well established that adult hematopoietic stem cells (HSCs) are active contributors to these processes after transplantation, yet their role in native hematopoiesis has recently been called into question. Here, we use inducible lineage tracing from genetically marked adult HSCs to explore their roles in the steady state. We show that adult HSCs contribute robustly to all lineages via intermediate progenitor cells, but with neglible production of hematopoietic cells with a known fetal origin. We further reveal that the timing for regeneration of distinct blood lineages varies substantially. Finally, HSC contribution to multilineage hematopoiesis in aged animals declines with increasing age. Therefore, while HSCs are active contributors to native adult hematopoiesis, it appears that the numerical increase of HSCs is a physiologically relevant compensatory mechanism to account for a reduced differentiation capacity with age.

developmental biology↗