Neuronal Lineage Research Articles

Renewal of oligodendrocyte lineage reverses dysmyelination and CNS neurodegeneration through corrected N-acetylaspartate metabolism.

Myelinating oligodendrocytes are essential for neuronal communication and homeostasis of the central nervous system (CNS). One of the most abundant molecules in the mammalian CNS is N-acetylaspartate (NAA), which is catabolized into L-aspartate and acetate by the enzyme aspartoacylase (ASPA) in oligodendrocytes. The resulting acetate moiety is thought to contribute to myelin lipid synthesis. In addition, affected NAA metabolism has been implicated in several neurological disorders, including leukodystrophies and demyelinating diseases such as multiple sclerosis. Genetic disruption of ASPA function causes Canavan disease, which is hallmarked by increased NAA levels, myelin and neuronal loss, large vacuole formation in the CNS, and early death in childhood. Although NAA's direct role in the CNS is inconclusive, in peripheral adipose tissue, NAA-derived acetate has been found to modify histones, a mechanism known to be involved in epigenetic regulation of cell differentiation. We hypothesize that a lack of cellular differentiation in the brain contributes to the disruption of myelination and neurodegeneration in diseases with altered NAA metabolism, such as Canavan disease. Our study demonstrates that loss of functional Aspa in mice disrupts myelination and shifts the transcriptional expression of neuronal and oligodendrocyte markers towards less differentiated stages in a spatiotemporal manner. Upon re-expression of ASPA, these oligodendrocyte and neuronal lineage markers are either improved or normalized, suggesting that NAA breakdown by Aspa plays an essential role in the maturation of neurons and oligodendrocytes. Also, this effect of ASPA re-expression is blunted in old mice, potentially due to limited ability of neuronal, rather than oligodendrocyte, recovery.

H4K16ac activates the transcription of transposable elements and contributes to their cis-regulatory function

Mammalian genomes harbor abundant transposable elements (TEs) and their remnants, with numerous epigenetic repression mechanisms enacted to silence TE transcription. However, TEs are upregulated during early development, neuronal lineage, and cancers, although the epigenetic factors contributing to the transcription of TEs have yet to be fully elucidated. Here, we demonstrate that the male-specific lethal (MSL)-complex-mediated histone H4 acetylation at lysine 16 (H4K16ac) is enriched at TEs in human embryonic stem cells (hESCs) and cancer cells. This in turn activates transcription of subsets of full-length long interspersed nuclear elements (LINE1s, L1s) and endogenous retrovirus (ERV) long terminal repeats (LTRs). Furthermore, we show that the H4K16ac-marked L1 and LTR subfamilies display enhancer-like functions and are enriched in genomic locations with chromatin features associated with active enhancers. Importantly, such regions often reside at boundaries of topologically associated domains and loop with genes. CRISPR-based epigenetic perturbation and genetic deletion of L1s reveal that H4K16ac-marked L1s and LTRs regulate the expression of genes in cis. Overall, TEs enriched with H4K16ac contribute to the cis-regulatory landscape at specific genomic locations by maintaining an active chromatin landscape at TEs.

ATRT-04. TARGETING THE COREST COMPLEX HELPS REPROGRAM AT/RT’S ABNORMAL EPIGENETIC LANDSCAPE TOWARD A DIFFERENTIATION PHENOTYPE

Abstract Atypical teratoid/rhabdoid tumors (AT/RT) are deadly infantile brain tumors. Their aggressive phenotype results from a single recurring biallelic loss-of-function mutation in genes encoding components of the SWI/SNF chromatin-remodeling complex - mainly SMARCB1 and SMARCA4 in remaining tumors. Residual SWI/SNF activity continues to inhibit EZH2 methyltransferase except at promoter regions colocalized to REST, which associates with neuronal differentiation and tumor suppressor genes. At these sites, EZH2 increases repressive H3K27me3 marks, helping maintain AT/RT in a stem cell-like state, and driving its aggressive growth and therapy resistance. We study the consequences of disrupting SWI/SNF inhibition at sites of EZH2/REST co-localization to target AT/RT precisely. The repressive action of REST is carried out mainly by the CoREST complex, consisting of LSD1, HDAC1/2 and RCOR. Lentiviral knockdown of RCOR2 reversed AT/RT’s stem cell-like state and induced differentiation along the glial and neuronal lineage. A decrease in the H3K27Me3 further confirmed the absence of COREST complex assembly at these sites. We used a bifunctional LSD1 and HDAC1/2 inhibitor, Corin, to pharmacologically target the CoREST complex in AT/RT cells. Corin also induced neuronal differentiation in AT/RT with increased expression of neuronal differentiation markers and decreased expression of stem cell markers. Further, Corin reduced AT/RT cell viability and proliferation (p<0.05) and increased apoptosis (p<0.05). In mice bearing orthotopic CHLA06 tumors, convection-enhanced delivery of a single dose of Corin increased H3K27ac, demonstrating that Corin engaged its target in vivo and induced apoptosis (western blot, cPARP). These studies demonstrate that targeting the CoREST complex disrupts AT/RT epigenetic abnormalities, reversing their stem cell-like state, slowing tumor cell growth, and inducing apoptosis. Targeting the CoREST complex with Corin is a promising new strategy that may translate into the clinical setting to help improve AT/RT’s dismal survival.

HGG-17. SINGLE-CELL AND SPATIAL ANALYSES DECIPHER THE UNIQUE INVASIVE GROWTH PATTERN OF GLIOMATOSIS CEREBRI

Abstract Gliomatosis cerebri (GC) is a rare, lethal glioma that is radiologically diagnosed and characterised by its diffuse infiltration throughout the cerebral lobes of the brain. It is no longer recognised as a separate entity by the WHO classification, but its growth pattern and invasive phenotype differ from other types of glioma. In order to understand what underlies this unique presentation, we sought to unravel these complex tumours in children through single cell and spatial approaches. 26 paediatric cases (1.3-19 years, median=11.3) were collected for DNA methylation, whole exome sequencing and single cell RNA-sequencing. Of these, 16 cases were used for Imaging Mass Cytometry (IMC). 5 patient-derived cell lines were used to model migration and invasion in vitro, whereby we have also been able to explore gene expression differences associated with the invading cells by RNAseq. We analyzed the transcriptional landscape of all 26 GC patients at single-cell resolution, and identified shared tumor cellular programs of glial and neuronal lineage. We observed notable heterogeneity of neuronal lineage tumor cells that were composed of different states, such as metabolic active and synaptogenic states. We described tumor cell states associated with higher invasivity, as corroborated from integrated analysis with our in vitro invasion-associated gene expression profiles. Next, we stratified all tumors by their DNA methylation profiles, and defined 16 archetypal GC cases, for which we show specific transcriptional features. Furthermore, we analyzed multiple regions of interest within FFPE patient tissue sections by IMC and demonstrate spatial patterns in the interaction between the tumour and normal brain tissue interface, and inter-regional heterogeneity for stem, invasive and proliferative markers. Together, we dissect the characteristic invasive phenotype of GC at multiple molecular, spatial and functional layers, thereby providing the basis for modelling and therapeutic avenues much needed for this lethal disease.

BIOL-10. MOUSE MODELING OF PEDIATRIC MYCN GLIOMA REVEALS INTRATUMORAL HETEROGENEITY INCLUDING NEURONAL AND OLIGODENDROGLIAL LINEAGE SIGNATURES

Abstract Pediatric glioma of the subclass MYCN are highly aggressive tumors with a median age at diagnosis of 8 years and a median survival of only 14 months. Molecularly, they frequently carry MYCN amplifications, TP53 mutations or both of these alterations. Due to their rarity, such tumors have only recently been identified as a distinct entity, and both biological as well as clinical details have not been fully addressed. In order to further investigate the biology and treatment options of these tumors, preclinical models are urgently needed. Therefore, we generated a genetically engineered model by breeding hGFAP-cre::Trp53Fl/Fl::lsl-MYCN mice, which carry a loss of Trp53 and show aberrant MYCN expression in neural precursors of the central nervous system. All such mice developed aggressive forebrain tumors early in lifetime that mimic their human counterparts regarding histology, DNA methylation, and gene expression. Single cell RNA sequencing revealed a high intratumoral heterogeneity with neuronal and oligodendroglial lineage signatures. To find new treatment options, we performed in vitro high-throughput drug screening on both, mouse and human tumor cells. Among 640 investigated anticancer compounds, Doxorubicin, Irinotecan, and Etoposide effectively suppressed the growth of tumor cells. As FDA-approved chemotherapeutics, these compounds are used for the treatment of other pediatric brain tumors. Repurposing them for the treatment of MYCN-driven high grade glioma could achieve a rapid transition to glioma treatment. We believe that our model will pave the way to improved treatment strategies for patients with these highly aggressive tumors.

MDB-05. HUMAN FETAL CEREBELLAR CELL ATLAS INFORMS MEDULLOBLASTOMA ORIGIN AND ONCOGENESIS

Abstract Medulloblastoma (MB) is the most common malignant childhood brain tumor, yet the origin of the most aggressive subgroup-3 form remains elusive, impeding development of effective targeted treatments. Previous analyses of mouse cerebella or human counterparts from frozen tissue nuclei5 have not fully defined the compositional heterogeneity of MBs. Here, we undertook an unprecedented single-cell profiling of freshly-isolated human fetal cerebella to establish a reference map delineating hierarchical cellular states in MBs. We identified a unique transitional cerebellar progenitor connecting neural stem cells to neuronal lineages in developing fetal cerebella. Intersectional analysis revealed that the transitional progenitors were enriched in aggressive MB subgroups, including group-3 and metastatic tumors. Single-cell multi-omics revealed underlying regulatory networks in the transitional progenitor populations, including transcriptional determinants HNRNPH1 and SOX11, which are correlated with clinical prognosis in group-3 MBs. Genomic and Hi-C profiling identified de novo long-range chromatin-loops juxtaposing HNRNPH1/SOX11-targeted super-enhancers to cis-regulatory elements of MYC, an oncogenic driver for group-3 MBs. Targeting the transitional progenitor regulators inhibited MYC expression and MYC-driven group-3 MB growth. Our integrated single-cell atlases of human fetal cerebella and MBs reveal potential cell populations predisposed to transformation and regulatory circuitries underlying tumor cell states and oncogenesis, highlighting hitherto unrecognized transitional progenitor intermediates predictive of disease prognosis and potential therapeutic vulnerabilities.

Transplanting Human Neural Stem Cells with ≈50% Reduction of SOX9 Gene Dosage Promotes Tissue Repair and Functional Recovery from Severe Spinal Cord Injury.

Neural stem cells (NSCs) derived from human pluripotent stem cells (hPSCs) are considered a major cell source for reconstructing damaged neural circuitry and enabling axonal regeneration. However, the microenvironment at the site of spinal cord injury (SCI) and inadequate intrinsic factors limit the therapeutic potential of transplanted NSCs. Here, it is shown that half dose of SOX9 in hPSCs-derived NSCs (hNSCs) results in robust neuronal differentiation bias toward motor neuron lineage. The enhanced neurogenic potency is partly attributed to the reduction of glycolysis. These neurogenic and metabolic properties retain after transplantation of hNSCs with reduced SOX9 expression in a contusive SCI rat model without the need for growth factor-enriched matrices. Importantly, the grafts exhibit excellent integration properties, predominantly differentiate into motor neurons, reduce glial scar matrix accumulation to facilitate long-distance axon growth and neuronal connectivity with the host as well as dramatically improve locomotor and somatosensory function in recipient animals. These results demonstrate that hNSCs with half SOX9 gene dosage can overcome extrinsic and intrinsic barriers, representing a powerful therapeutic potential for transplantation treatments for SCI.

Protein O-GlcNAcylation homeostasis regulates facultative heterochromatin to fine-tune sog-Dpp signaling during Drosophila early embryogenesis

Protein O-GlcNAcylation is a monosaccharide post-translational modification maintained by two evolutionarily conserved enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Mutations in human OGT have recently been associated with neurodevelopmental disorders, although the mechanisms linking O-GlcNAc homeostasis to neurodevelopment are not understood. Here, we investigate the effects of perturbing protein O-GlcNAcylation using transgenic Drosophila lines that overexpress a highly active OGA. We reveal that temporal reduction of protein O-GlcNAcylation in early embryos leads to reduced brain size and olfactory learning in adult Drosophila. Downregulation of O-GlcNAcylation induced by the exogenous OGA activity promotes nuclear foci formation of Polycomb-group protein Polyhomeotic and the accumulation of excess K27 trimethylation of histone H3 (H3K27me3) at the mid-blastula transition. These changes interfere with the zygotic expression of several neurodevelopmental genes, particularly shortgastrulation (sog), a component of an evolutionarily conserved sog-Decapentaplegic (Dpp) signaling system required for neuroectoderm specification. Our findings highlight the importance of early embryonic O-GlcNAcylation homeostasis for the fidelity of facultative heterochromatin redeployment and initial cell fate commitment of neuronal lineages, suggesting a possible mechanism underpinning OGT-associated intellectual disability.

Abstract PR004: Exploring the role of ASCL1 in neuroendocrine prostate cancer

Abstract Most patients with prostate adenocarcinoma (PAd), an androgen receptor (AR) driven cancer, develop resistance to therapies targeting AR. Consequently, a portion of these patients develop neuroendocrine prostate cancer (NEPC), a rapidly progressing cancer with limited therapies and poor survival outcomes. Current research to understand the transition of PAd to NEPC suggests a model of lineage plasticity, where AR-dependent luminal tumors progress towards an AR-independent neuroendocrine lineage. Several groups have shown human NEPC tumors have lost RB1 and TP53, and in experimental models, loss of both genes mediates the transition to a neuroendocrine lineage. Notably, NEPC histology and gene expression resemble another neuroendocrine cancer, small cell lung carcinoma (SCLC), also characterized by loss of RB1 and TP53. In SCLC, transcription factor ASCL1 is required for tumor cell growth in vitro and for SCLC formation in vivo. ASCL1 is also present in NEPC tumors and in NEPC cell line models. In fact, ASCL1 was shown to regulate neuronal stem cell-like lineage programming in NEPC in vitro. We aimed to determine if ASCL1 is required in the transition of PAd to NEPC in vivo and to define its function in NEPC. To model the PAd to NEPC transition, we established genetically engineered mouse models (GEMMs) harboring loss of RB1 and TP53 with MYC overexpression (RPM) by administering adenovirus expressing Cre recombinase directly to the prostate of these GEMMs. These animals display prostate tumors with small cell histology and are heterogeneous for neuroendocrine markers such as ASCL1, NEUROD1, and INSM1. We recently determined that the concomitant loss of ASCL1 in this model (RPMA) does not stop the formation of tumors with small cell histology. Notably, a subset of the cells with small cell histology are NEUROD1+, with a higher proportion of NEUROD1+ cells present compared to the RPM model with intact ASCL1, suggesting the possibility that NEUROD1 in the same or distinct cells is compensating for the absence of ASCL1. In a separate paradigm using these same GEMMs to establish prostate organoids, we show their capacity to generate subcutaneous allograft tumors displaying mixed histology including neuroendocrine small cell features expressing ASCL1, NEUROD1, and INSM1. Strikingly, subcutaneous allografts from prostate organoids lacking ASCL1 exhibit a dramatic reduction in tumor formation efficiency, lack small cell histology including NEUROD1 and INSM1 and other neuroendocrine markers, and often result in the development of cysts rather than tumors. These results demonstrate complex functions for ASCL1 in neuroendocrine lineage programming while suggesting additional functions in supporting prostate tumor formation. Citation Format: Kathia E. Rodarte, Lydia Flores, Vishal Kandagatla, Juan Villarreal, Trisha K. Savage, Su Deng, Ping Mu, Rajal B. Shah, Trudy G. Oliver, Jane E. Johnson. Exploring the role of ASCL1 in neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr PR004.

Abstract B017: Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer

Abstract Lineage plasticity is an emerging mechanism of treatment-resistance in prostate cancer, which can manifest clinically as histologic transformation from prostate adenocarcinoma to small-cell neuroendocrine prostate cancer (NEPC). NEPC is associated with poor prognosis, and new treatment strategies are urgently needed. Epigenetic dysregulation has been implicated as a key driver of prostate cancer lineage plasticity, mediated in part by EZH2. EZH2 is a component of the polycomb repressive complex (PRC2) regulating the transcriptional repressive mark H3K27me3. EZH2 also controls cell-fate determination during normal development via bivalent promoters bearing both repressive H3K27me3 and active H3K4me3 marks. EZH2 is targetable, and several EZH2 inhibitors are in clinical development; these trials are currently in biomarker-unselected prostate cancer populations. A thorough understanding of the mechanism of action of EZH2 is imperative for predicting optimal response to EZH2i and for the development of robust combination treatment strategies. Cell viability studies across a diverse panel of prostate cancer models representing adenocarcinoma and NEPC indicated variable responses to tazemetostat (EZH2i) treatment. The castration-resistant prostate adenocarcinoma (CRPC) cell line LNCaP-abl showed a greater than 50% reduction in cell viability upon EZH2i (5uM) while LNCaP and 22Rv1 showed moderate response with 15-25% reduction in cell viability. However, none of our 5 NEPC patient-derived models showed significant response to EZH2i which was also validated in vivo. Hierarchical clustering of RNA-seq profiles of responder and non-responder models revealed distinct cell-type specific EZH2 targets and clusters of genes that may be associated with response to EZH2i. Approximately 15% of the EZH2 targets in the NEPC organoid WCM154 carried bivalency in their promoters including neuronal lineage determining genes such as ASCL1 and LHX2. Gene set enrichment analysis of EZH2 targets bearing bivalency in NEPC revealed association with neurogenesis and cell proliferation pathways. Further upregulation of neuronal-lineage PRC2 targets in NEPC models upon EZH2i may provide justification for lack of lineage reversal and maintenance of terminal differentiation. While there is evidence that EZH2i leads to lineage reversion in adeno-to-NEPC transitioning preclinical models, our data shows that EZH2i was associated with modest response in NEPC models and did not revert lineage plasticity. Our results provide insights into a potential role for bivalent promoters in EZH2-mediated lineage reprogramming and sustenance of terminal differentiation upon EZH2i in NEPC. Understanding lineage-specific action of EZH2i may inform biomarkers in ongoing clinical trials. Genes and pathways dysregulated because of their bivalency might also be exploited as potential candidates to be co-targeted with EZH2i. Citation Format: Varadha Balaji Venkadakrishnan, Richa Singh, Yasutaka Yamada, Kei Mizuno, Adam G. Presser, Sheng-Yu Ku, Henry Long, David Rickman, Himisha Beltran. Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B017.

Establishment of Cerebral Organoid‐like Structures from Dental Pulp Stem Cells (DPSCs) to Model Neurodegenerative Diseases.

AbstractBackground3D‐cell cultures are closer to in vivo conditions than the monolayers. There are different 3D‐cell culture models, the most relevant is the Cerebral Organoids (CO) model (Lancaster et al. 2014), it can show complex processes and proved to show molecular and structural changes when modeling Alzheimer´s disease (AD), and other diseases. One of the main limitations of using this model is the requirement for Induced Pluripotent Stem Cells (iPSC) or Human Embryonic Stem Cells (hESC) for the CO generation; because iPSC could undergo epigenetic changes during the process of reprogramming; moreover, hESC are controversial because of their ethical implications. We proposed to use DPSCs instead of iPSC or hESC to generate organoid‐like structures due to their capability to differentiate into the neuronal lineage, lack of pluripotency, and its easy access.MethodThe DPSCs were obtained by dissociating the dental pulp of a healthy 46 years old female with a colagenase‐dispase mix at 37°C, isolated and cultured. The cells phenotype was characterized by Western‐Blot, RT‐PCR and immunofluorescence. We cultured the DPSC into low‐adherence wells for 6 days in a DMEM/F12 medium + thiazovivin 50 mM, bFGF 4ng/mL, BFS 20%, Glutamax® 200x, MEM‐NEAA 1:100, 2‐mercaptoethanol 100 µm and murine LIF 10 µg/mL until cell aggregation into embryoid‐like structures. After that, neural induction was carried out.ResultWe successfully characterized DPSC phenotype by detecting pluripotential markers OCT4, Actin, NanoG, mesenchymal markers CD105, CD73, and the neuronal marker β‐III Tubulin which is always present in the DPSCs lineage, as well as the lack of hematopoietic markers CD14, CD34, and CD45. We obtained Cerebral Organoids‐like structures from de DPSCs after 35 days of the differentiation protocol and detected NeuN, MAP2, β‐III Tubulin, and tau, all neural markers that claim a neuronal phenotype.ConclusionOur results suggest a potential use of this approach to the CO generation using DPSCs instead of iPSC or hESC with the benefits of a shorter time and a less expensive protocol likewise, DPSCs could resemble the molecular aging changes. Further studies are needed to validate the use of this CO to model neurodegenerative diseases such as AD.

Effects of acute low-moderate dose ionizing radiation to human brain organoids.

Human exposure to low-to-moderate dose ionizing radiation (LMD-IR) is increasing via environmental, medical, occupational sources. Acute exposure to LMD-IR can cause subclinical damage to cells, resulting in altered gene expression and cellular function within the human brain. It has been difficult to identify diagnostic and predictive biomarkers of exposure using traditional research models due to factors including lack of 3D structure in monolayer cell cultures, limited ability of animal models to accurately predict human responses, and technical limitations of studying functional human brain tissue. To address this gap, we generated brain/cerebral organoids from human induced pluripotent stem cells to study the radiosensitivity of human brain cells, including neurons, astrocytes, and oligodendrocytes. While organoids have become popular models for studying brain physiology and pathology, there is little evidence to confirm that exposing brain organoids to LMD-IR will recapitulate previous in vitro and in vivo observations. We hypothesized that exposing brain organoids to proton radiation would (1) cause a time- and dose-dependent increase in DNA damage, (2) induce cell type-specific differences in radiosensitivity, and (3) increase expression of oxidative stress and DNA damage response genes. Organoids were exposed to 0.5 or 2 Gy of 250 MeV protons and samples were collected at 30 minute, 24 hour, and 48 hour timepoints. Using immunofluorescence and RNA sequencing, we found time- and dose-dependent increases in DNA damage in irradiated organoids; no changes in cell populations for neurons, oligodendrocytes, and astrocytes by 24 hours; decreased expression of genes related to oligodendrocyte lineage, astrocyte lineage, mitochondrial function, and cell cycle progression by 48 hours; increased expression of genes related to neuron lineage, oxidative stress, and DNA damage checkpoint regulation by 48 hours. Our findings demonstrate the possibility of using organoids to characterize cell-specific radiosensitivity and early radiation-induced gene expression changes within the human brain, providing new avenues for further study of the mechanisms underlying acute neural cell responses to IR exposure at low-to-moderate doses.

Inorganic nanorods direct neuronal differentiation of bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells and are considered a potential source for tissue and organ repair due to their self-renewal, proliferation, and differentiation abilities. However, in most cases, MSCs are needed to be stimulated with external growth factors to promote their proliferation and differentiation. Over the past decade, it has been demonstrated that nanomaterials could facilitate MSC proliferation and differentiation, and excellent efforts are carried out to investigate their possible modulating pattern and mechanisms for MSC differentiation. Europium hydroxide (EuIII(OH)3) nanorods (EHN) are well-researched for their biomimicking properties and act as a substitute for growth factors that induce cell proliferation, migration, and differentiation. In the current study, the human MSCs were chosen as an in vitro model for evaluating the role of EHN in modulating the differentiation process of MSCs into neuronal and glial lineages. The characterization of MSCs and differentiated neuronal cells observed by flow cytometry, confocal, and gene marker expression studies supported our hypothesis that the EHNs are pro-angiogenic and pro-neurogenic. Finally, altogether our results suggest that EHNs have the potential to play an essential part in developing novel treatment strategies for neurodegenerative diseases and spinal cord injuries based on the nanomedicine approach.

Progenitor-derived glia are required for spinal cord regeneration in zebrafish.

Unlike mammals, adult zebrafish undergo spontaneous recovery after major spinal cord injury. Whereas reactive gliosis presents a roadblock for mammalian spinal cord repair, glial cells in zebrafish elicit pro-regenerative bridging functions after injury. Here, we perform genetic lineage tracing, assessment of regulatory sequences and inducible cell ablation to define mechanisms that direct the molecular and cellular responses of glial cells after spinal cord injury in adult zebrafish. Using a newly generated CreERT2 transgenic line, we show that the cells directing expression of the bridging glial marker ctgfa give rise to regenerating glia after injury, with negligible contribution to either neuronal or oligodendrocyte lineages. A 1 kb sequence upstream of the ctgfa gene was sufficient to direct expression in early bridging glia after injury. Finally, ablation of ctgfa-expressing cells using a transgenic nitroreductase strategy impaired glial bridging and recovery of swim behavior after injury. This study identifies key regulatory features, cellular progeny, and requirements of glial cells during innate spinal cord regeneration.

Neurogenic Stem Cell Niche in the Auditory Thalamus: In Vitro Evidence of Neural Stem Cells in the Rat Medial Geniculate Body.

The medial geniculate body (MGB) is a nucleus of the diencephalon representing a relevant segment of the auditory pathway and is part of the metathalamus. It receives afferent information via the inferior brachium of the inferior colliculus and transmits efferent fibers via acoustic radiations to the auditory cortex. Neural stem cells (NSCs) have been detected in certain areas along the auditory pathway. They are of great importance as the induction of an adult stem cell niche might open a regenerative approach to a causal treatment of hearing disorders. Up to now, the existence of NSCs in the MGB has not been determined. Therefore, this study investigated whether the MGB has a neural stem cell potential. For this purpose, cells were extracted from the MGB of PND 8 Sprague-Dawley rats and cultured in a free-floating cell culture assay, which showed mitotic activity and positive staining for stem cell and progenitor markers. In differentiation assays, the markers β-III-tubulin, GFAP, and MBP demonstrated the capacity of single cells to differentiate into neuronal and glial cells. In conclusion, cells from the MGB exhibited the cardinal features of NSCs: self-renewal, the formation of progenitor cells, and differentiation into all neuronal lineage cells. These findings may contribute to a better understanding of the development of the auditory pathway.

Co-administration of extracellular matrix-based biomaterials with neural stem cell transplantation for treatment of central nervous system injury.

Injuries and disorders of the central nervous system (CNS) present a particularly difficult challenge for modern medicine to address, given the complex nature of the tissues, obstacles in researching and implementing therapies, and barriers to translating efficacious treatments into human patients. Recent advancements in neural stem cell (NSC) transplantation, endogenous neurogenesis, and in vivo reprogramming of non-neural cells into the neuronal lineage represent multiple approaches to resolving CNS injury. However, we propose that one practice that must be incorporated universally in neuroregeneration studies is the use of extracellular matrix (ECM)-mimicking biomaterials to supply the architectural support and cellular microenvironment necessary for partial or complete restoration of function. Through consideration of developmental processes including neurogenesis, cellular migration, and establishment of functional connectivity, as well as evaluation of process-specific interactions between cells and ECM components, insights can be gained to harness and modulate native and induced neurobiological processes to promote CNS tissue repair. Further, evaluation of the current landscape of regenerative medicine and tissue engineering techniques external to the neurosciences provides key perspectives into the role of the ECM in the use of stem cell-based therapies, and the potential directions future neuroregenerative approaches may take. If the most successful of these approaches achieve wide-spread adoption, innovative paired NSC-ECM strategies for neuroregeneration may become prominent in the near future, and with the rapid advances these techniques are poised to herald, a new era of treatment for CNS injury may dawn.

Intra-individual variability in the neuroprotective and promyelinating properties of conditioned culture medium obtained from human adipose mesenchymal stromal cells

BackgroundGreater knowledge of mesenchymal stromal cell (MSC)-based therapies is driving the research into their secretome, identified as the main element responsible for their therapeutic effects. The aim of this study is to characterize the individual variability of the secretome of adipose tissue-derived MSCs (adMSCs) with regard to potential therapeutical applications in neurology.MethodsadMSCs were isolated from the intact adipose tissue of ten subjects undergoing abdominal plastic surgery or reduction mammoplasty. Two commercial lines were also included. We analyzed the expansion rate, production, and secretion of growth factors of interest for neurological applications (VEGF-A, BDNF, PDGF-AA and AA/BB, HGF, NGF, FGF-21, GDNF, IGF-I, IGF-II, EGF and FGF-2). To correlate these characteristics with the biological effects on the cellular targets, we used individual media conditioned with adMSCs from the various donors on primary cultures of neurons/astrocytes and oligodendrocyte precursor cells (OPCs) exposed to noxious stimuli (oxygen–glucose deprivation, OGD) to evaluate their protective and promyelinating properties, using MSC medium as a control group.ResultsThe MSC secretome showed significant individual variability within the considered population with regard to PDGF-AA, PDGF-AB/BB, VEGF-A and BDNF. None of the MSC-derived supernatants affected neuron viability in normoxia, while substantial protection by high BDNF-containing conditioned MSC medium was observed in neuronal cultures exposed to OGD conditions. In OPC cultures, the MSC-derived supernatants protected cells from OGD-induced cell death, also increasing the differentiation in mature oligodendrocytes. Neuroprotection showed a positive correlation with VEGF-A, BDNF and PDGF-AA concentrations in the culture supernatants, and an inverse correlation with HGF, while OPC differentiation following OGD was positively correlated to PDGF-AA concentration.ConclusionsDespite the limited number of adMSC donors, this study showed significant individual variability in the biological properties of interest for neurological applications for adMSC secretome, an under-researched aspect which may represent an important step in the translation of MSC-derived acellular products to clinical practice. We also showed the potential protection capability of MSC conditioned medium on neuronal and oligodendroglial lineages exposed to oxygen–glucose deprivation. These effects are directly correlated to the concentration of specific growth factors, and indicate that the remyelination should be included as a primary target in MSC-based therapies.

Diversity within olfactory sensory derivatives revealed by the contribution of Dbx1 lineages.

In vertebrates, the embryonic olfactory epithelium contains progenitors that will give rise to distinct classes of neurons, including olfactory sensory neurons (OSNs; involved in odor detection), vomeronasal sensory neurons (VSNs; responsible for pheromone sensing), and gonadotropin-releasing hormone (GnRH) neurons that control the hypothalamic-pituitary-gonadal axis. Currently, these three neuronal lineages are usually believed to emerge from uniform pools of progenitors. Here, we found that the homeodomain transcription factor Dbx1 is expressed by neurogenic progenitors in the developing and adult mouse olfactory epithelium. We demonstrate that Dbx1 itself is dispensable for neuronal fate specification and global organization of the olfactory sensory system. Using lineage tracing, we characterize the contribution of Dbx1 lineages to OSN, VSN, and GnRH neuron populations and reveal an unexpected degree of diversity. Furthermore, we demonstrate that Dbx1-expressing progenitors remain neurogenic in the absence of the proneural gene Ascl1. Our work therefore points to the existence of distinct neurogenic programs in Dbx1-derived and other olfactory lineages.

β-catenin engages IKZF factors to control lymphopoiesis

Abstract β-catenin-signaling promotes proliferation and survival in epithelial, neuronal, and mesenchymal lineages, but is dispensable for B- and T-cell development. β-catenin activation is a common oncogenic driver throughout all types of cancer with the exception of B- and T-lymphoid malignancies. Unlike epithelial tissues, we found that B- and T-cells consistently lack β-catenin expression. Instead, both B- and T-cells were highly sensitive to β-catenin-activation and critically depend on its negative regulation by GSK3β-dependent phosphorylation and degradation. Inhibition of GSK3β induced dramatic nuclear accumulation of β-catenin, anergy and cell death. In contrast, genetic deletion of β-catenin enabled clonal expansion of premalignant B- and T-cells. In epithelial cells, β-catenin and TCF-family factors form complexes for transcriptional activation of MYC. Instead of TCF-factors, our interactome studies in B- and T-cells revealed that, β-catenin formed complexes with lymphoid-specific Ikaros zinc finger (IKZF) transcription factors for transcriptional repressionof MYC at a recently discovered MYC ‘blood enhancer cluster’ (BENC). Hence, activation of β-catenin engages repressive complexes with Ikaros factors to regulate lymphopoiesis through transcriptional control of MYC. We propose that β-catenin-accumulation functions as sensing mechanism of pathological B- and T-cell signaling and that this mechanism can be leveraged for targeted eradication of pathological (autoreactive or malignant) clones. To engage this mechanism, targeted accumulation of β-catenin can be achieved by GSK3β-inhibition and represents a selective vulnerability of pathological B- and T-cell clones.

A mini-review to delineate the different roles of stem cells and Wnt signalling pathways in governing transdifferentiation towards neuronal lineage.

Mesenchymal stem cells are found to have the potential to differentiate into many lineages, thus regulating diverse signalling cascades. This unique property of stem cells, called trans differentiation/linear reprogramming, aided in regenerative medicine and tissue repair. The mechanism of such regeneration is still unclear and requires further analysis. Due to the use of external or oncogenic factors, one of the approaches for mending cardiac, renal, and neurological disorders after an injury by induced pluripotent stem cells in the form of reprogramming does not show much benefit in the clinical setting. Consequently, cellular reprogramming may enable the application of clinical research to cell therapy, disease modelling, drug screening, and the fabrication of artificial organs. Studies related to this distinctive phenomenon of stem cells, where the cells could reprogramme themselves into completely different cell lineages, showed a promising future in therapeutic applications. However, unrelenting development in cellular reprogramming has prepared the ways for novel strategies in which signalling pathway manipulation may decide cellular destiny. This cellular reprogramming has got bright prospects in the field of regenerative medicine. Therefore, understanding the relationship between stochasticity and defining cell fate can help decipher molecular regulatory mechanisms of cellular reprogramming.