Efficient Derivation of Excitatory and Inhibitory Neurons from Human Pluripotent Stem Cells Stably Expressing Direct Reprogramming Factors

Reduced SH3RF3 may protect against Alzheimer's disease by lowering microglial pro-inflammatory responses via modulation of JNK and NFkB signaling

Understanding how high-risk individuals are protected from Alzheimer's disease (AD) may illuminate potential therapeutic targets. A previously identified non-coding SNP in SH3RF3/POSH2 significantly delayed disease onset in a Caribbean Hispanic cohort carrying the PSEN1 G206A mutation sufficient to cause early-onset AD and microglial expression of SH3RF3 has been reported to be a key driver of late-onset AD. SH3RF3 acts as a JNK pathway scaffold and can activate NFκB signaling. While effects of SH3RF3 knockdown in human neurons were subtle, including decreased phospho-tau S422, knockdown in human microglia significantly reduced inflammatory cytokines in response to either a viral mimic or oligomeric Aβ42. This was associated with reduced activation of JNK and NFκB pathways in response to these stimuli. Pharmacological inhibition of JNK or NFκB signaling phenocopied SH3RF3 knockdown. We also found PSEN1 G206A microglia have reduced inflammatory responses to oAβ42. Thus, further reduction of microglial inflammatory responses in PSEN1 mutant carriers by protective SNPs in SH3RF3 might reduce the link between amyloid and neuroinflammation to subsequently delay the onset of AD.

Generation of hiPSC-derived brain microvascular endothelial cells using a combination of directed differentiation and transcriptional reprogramming strategies

The blood-brain barrier (BBB), formed by specialized brain microvascular endothelial cells (BMECs), regulates brain function in health and disease. In vitro modeling of the human BBB is limited by the lack of robust protocols to generate BMECs from human iPSCs (hiPSCs). Here, we report generation of reprogrammed BMECs (rBMECs) through combining hiPSC differentiation into BBB-primed endothelial cells (bpECs) and reprogramming with two BBB transcription factors, FOXF2 and ZIC3. rBMECs express a subset of the BBB gene repertoire including tight junctions and transporters, exhibit higher paracellular barrier properties, lower caveolar-mediated transcytosis, and equivalent p-glycoprotein activity compared to primary HBMECs, and can be activated by oligomeric Aβ42. We then generated an hiPSC-derived 3D neurovascular system that incorporates rBMECs, pericytes, and astrocytes using the MIMETAS platform. This novel 3D system closely resembles the in vivo BBB at structural and functional levels and can be used to study pathogenic mechanisms of neurological diseases.

A pharmacological toolkit for human microglia identifies Topoisomerase I inhibitors as immunomodulators for Alzheimer's disease

While efforts to identify microglial subtypes have recently accelerated, the relation of transcriptomically defined states to function has been largely limited to in silico annotations. Here, we characterize a set of pharmacological compounds that have been proposed to polarize human microglia towards two distinct states - one enriched for AD and MS genes and another characterized by increased expression of antigen presentation genes. Using different model systems including HMC3 cells, iPSC-derived microglia and cerebral organoids, we characterize the effect of these compounds in mimicking human microglial subtypes in vitro. We show that the Topoisomerase I inhibitor Camptothecin induces a CD74high/MHChigh microglial subtype which is specialized in amyloid beta phagocytosis. Camptothecin suppressed amyloid toxicity and restored microglia back to their homeostatic state in a zebrafish amyloid model. Our work provides avenues to recapitulate human microglial subtypes in vitro, enabling functional characterization and providing a foundation for modulating human microglia in vivo.

ZCCHC17 Modulates Neuronal RNA Splicing and Supports Cognitive Resilience in Alzheimer's Disease

ZCCHC17 is a putative master regulator of synaptic gene dysfunction in Alzheimer's disease (AD), and ZCCHC17 protein declines early in AD brain tissue, before significant gliosis or neuronal loss. Here, we investigate the function of ZCCHC17 and its role in AD pathogenesis using data from human autopsy tissue (consisting of males and females) and female human cell lines. Co-immunoprecipitation (co-IP) of ZCCHC17 followed by mass spectrometry analysis in human iPSC-derived neurons reveals that ZCCHC17's binding partners are enriched for RNA-splicing proteins. ZCCHC17 knockdown results in widespread RNA-splicing changes that significantly overlap with splicing changes found in AD brain tissue, with synaptic genes commonly affected. ZCCHC17 expression correlates with cognitive resilience in AD patients, and we uncover an APOE4-dependent negative correlation of ZCCHC17 expression with tangle burden. Furthermore, a majority of ZCCHC17 interactors also co-IP with known tau interactors, and we find a significant overlap between alternatively spliced genes in ZCCHC17 knockdown and tau overexpression neurons. These results demonstrate ZCCHC17's role in neuronal RNA processing and its interaction with pathology and cognitive resilience in AD, and suggest that the maintenance of ZCCHC17 function may be a therapeutic strategy for preserving cognitive function in the setting of AD pathology.

Reproducible Differentiation of Human Pluripotent Stem Cells into Two-Dimensional Cortical Neuron Cultures with Checkpoints for Success

The patterning of excitatory cortical neurons from human pluripotent stem cells (hPSCs) is a desired technique for the study of neurodevelopmental disorders, as neurons can be created and compared from control hPSC lines, hPSC lines generated from patients, and CRISPR-modified hPSC lines. Therefore, this technique allows for the examination of disease phenotypes and assists in the development of potential new therapeutics for neurodevelopmental disorders. Many protocols, however, are optimized for use with specific hPSC lines or within a single laboratory, and they often provide insufficient guidance on how to identify positive stages in the differentiation or how to troubleshoot. Here, we present an efficient and reproducible directed differentiation protocol to generate two-dimensional cultures of hPSC-derived excitatory cortical neurons without intermediary embryoid body formation. This novel protocol is supported by our data generated with five independent hPSC lines and in two independent laboratories. Importantly, as neuronal differentiations follow a long time course to reach maturity, we provide extensive guidance regarding morphological and flow cytometry checkpoints allowing for early indications of successful differentiation. We also include extensive troubleshooting tips and support protocols to assist the operator. The goal of this protocol is to assist others in the successful differentiation of excitatory cortical neurons from hPSCs. © 2023 Wiley Periodicals LLC. Basic Protocol: Directed differentiation of hPSCs into excitatory cortical neurons Support Protocol 1: Harvesting and fixing cells for flow cytometry analyses Support Protocol 2: Performing flow cytometry analyses Support Protocol 3: Thawing NPCs from a cryopreserved stock Alternate Protocol 1: Continuing Expansion of NPCs Alternate Protocol 2: Treatment of neurons with Ara-C to ablate radial glia Support Protocol 4: Experimental methods for validation of excitatory cortical neurons.

ZCCHC17 modulates neuronal RNA splicing and supports cognitive resilience in Alzheimer's disease

ZCCHC17 is a putative master regulator of synaptic gene dysfunction in Alzheimer's Disease (AD), and ZCCHC17 protein declines early in AD brain tissue, before significant gliosis or neuronal loss. Here, we investigate the function of ZCCHC17 and its role in AD pathogenesis. Co-immunoprecipitation of ZCCHC17 followed by mass spectrometry analysis in human iPSC-derived neurons reveals that ZCCHC17's binding partners are enriched for RNA splicing proteins. ZCCHC17 knockdown results in widespread RNA splicing changes that significantly overlap with splicing changes found in AD brain tissue, with synaptic genes commonly affected. ZCCHC17 expression correlates with cognitive resilience in AD patients, and we uncover an APOE4 dependent negative correlation of ZCCHC17 expression with tangle burden. Furthermore, a majority of ZCCHC17 interactors also co-IP with known tau interactors, and we find significant overlap between alternatively spliced genes in ZCCHC17 knockdown and tau overexpression neurons. These results demonstrate ZCCHC17's role in neuronal RNA processing and its interaction with pathology and cognitive resilience in AD, and suggest that maintenance of ZCCHC17 function may be a therapeutic strategy for preserving cognitive function in the setting of AD pathology.

A Robust Pipeline for the Multi-Stage Accelerated Differentiation of Functional 3D Cortical Organoids from Human Pluripotent Stem Cells

Disordered cellular development, abnormal neuroanatomical formations, and dysfunction of neuronal circuitry are among the pathological manifestations of cortical regions in the brain that are often implicated in complex neurodevelopmental disorders. With the advancement of stem cell methodologies such as cerebral organoid generation, it is possible to study these processes in vitro using 3D cellular platforms that mirror key developmental stages occurring throughout embryonic neurogenesis. Patterning-based stem cell models of directed neuronal development offer one approach to accomplish this, but these protocols often require protracted periods of cell culture to generate diverse cell types and current methods are plagued by a lack of specificity, reproducibility, and temporal control over cell derivation. Although ectopic expression of transcription factors offers another avenue to rapidly generate neurons, this process of direct lineage conversion bypasses critical junctures of neurodevelopment during which disease-relevant manifestations may occur. Here, we present a directed differentiation approach for generating human pluripotent stem cell (hPSC)-derived cortical organoids with accelerated lineage specification to generate functionally mature cortical neurons in a shorter timeline than previously established protocols. This novel protocol provides precise guidance for the specification of neuronal cell type identity as well as temporal control over the pace at which cortical lineage trajectories are established. Furthermore, we present assays that can be used as tools to interrogate stage-specific developmental signaling mechanisms. By recapitulating major components of embryonic neurogenesis, this protocol allows for improved in vitro modeling of cortical development while providing a platform that can be utilized to uncover disease-specific mechanisms of disordered development at various stages across the differentiation timeline. © 2023 Wiley Periodicals LLC. Basic Protocol 1: 3D hPSC neural induction Support Protocol 1: Neural rosette formation assay Support Protocol 2: Neurosphere generation Support Protocol 3: Enzymatic dissociation, NSC expansion, and cryopreservation Basic Protocol 2: 3D neural progenitor expansion Basic Protocol 3: 3D accelerated cortical lineage patterning and terminal differentiation.

Regrow or Repair: An Update on Potential Regenerative Therapies for the Kidney

Fifteen years ago, this journal published a review outlining future options for regenerating the kidney. At that time, stem cell populations were being identified in multiple tissues, the concept of stem cell recruitment to a site of injury was of great interest, and the possibility of postnatal renal stem cells was growing in momentum. Since that time, we have seen the advent of human induced pluripotent stem cells, substantial advances in our capacity to both sequence and edit the genome, global and spatial transcriptional analysis down to the single-cell level, and a pandemic that has challenged our delivery of health care to all. This article will look back over this period of time to see how our view of kidney development, disease, repair, and regeneration has changed and envision a future for kidney regeneration and repair over the next 15 years.

Cell Transdifferentiation and Reprogramming in Disease Modeling: Insights into the Neuronal and Cardiac Disease Models and Current Translational Strategies

Cell transdifferentiation and reprogramming approaches in recent times have enabled the manipulation of cell fate by enrolling exogenous/artificial controls. The chemical/small molecule and regulatory components of transcription machinery serve as potential tools to execute cell transdifferentiation and have thereby uncovered new avenues for disease modeling and drug discovery. At the advanced stage, one can believe these methods can pave the way to develop efficient and sensitive gene therapy and regenerative medicine approaches. As we are beginning to learn about the utility of cell transdifferentiation and reprogramming, speculations about its applications in translational therapeutics are being largely anticipated. Although clinicians and researchers are endeavoring to scale these processes, we lack a comprehensive understanding of their mechanism(s), and the promises these offer for targeted and personalized therapeutics are scarce. In the present report, we endeavored to provide a detailed review of the original concept, methods and modalities enrolled in the field of cellular transdifferentiation and reprogramming. A special focus is given to the neuronal and cardiac systems/diseases towards scaling their utility in disease modeling and drug discovery.