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SARS-CoV-2 induces Alzheimer's disease-related amyloid-β pathology in ex vivo human retinal explants and retinal organoids.
While the etiology of Alzheimer's disease remains unknown, there is growing support for the amyloid-β antimicrobial hypothesis. Amyloid-β, the main component of amyloid plaques in Alzheimer's disease, has been shown to be generated in the presence of microbes. Entrapment of microbes by aggregated amyloid-β may serve as an innate immune response to pathogenic infections. To understand the association of amyloid-β plaques and pathogenic infections in the central nervous system, we obtained viable short-interval postmortem human retinal tissue and generated human retinal organoids that contain electrophysiologically active neurons. Here, we demonstrate that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces amyloid-β extracellular protein aggregates in human retinal explants and retinal organoids. Last, pharmacological inhibition of neuropilin-1 resulted in reduced amyloid-β deposition in human retinal explants treated with SARS-CoV-2 Spike 1 protein. These results suggest that Spike 1 protein, during infection with SARS-CoV-2, can induce amyloid-β aggregation, which may be associated with the neurological symptoms experienced in COVID-19.
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Disease models of Leigh syndrome: From yeast to organoids.
Leigh syndrome (LS) is a severe mitochondrial disease that results from mutations in the nuclear or mitochondrial DNA that impairs cellular respiration and ATP production. Mutations in more than 100 genes have been demonstrated to cause LS. The disease most commonly affects brain development and function, resulting in cognitive and motor impairment. The underlying pathogenesis is challenging to ascertain due to the diverse range of symptoms exhibited by affected individuals and the variability in prognosis. To understand the disease mechanisms of different LS-causing mutations and to find a suitable treatment, several different model systems have been developed over the last 30 years. This review summarizes the established disease models of LS and their key findings. Smaller organisms such as yeast have been used to study the biochemical properties of causative mutations. Drosophila melanogaster, Danio rerio, and Caenorhabditis elegans have been used to dissect the pathophysiology of the neurological and motor symptoms of LS. Mammalian models, including the widely used Ndufs4 knockout mouse model of complex I deficiency, have been used to study the developmental, cognitive, and motor functions associated with the disease. Finally, cellular models of LS range from immortalized cell lines and trans-mitochondrial cybrids to more recent model systems such as patient-derived induced pluripotent stem cells (iPSCs). In particular, iPSCs now allow studying the effects of LS mutations in specialized human cells, including neurons, cardiomyocytes, and even three-dimensional organoids. These latter models open the possibility of developing high-throughput drug screens and personalized treatments based on defined disease characteristics captured in the context of a defined cell type. By analyzing all these different model systems, this review aims to provide an overview of past and present means to elucidate the complex pathology of LS. We conclude that each approach is valid for answering specific research questions regarding LS, and that their complementary use could be instrumental in finding treatment solutions for this severe and currently untreatable disease.
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Long-term patient-derived ovarian cancer organoids closely recapitulate tumor of origin and clinical response.
BACKGROUND: Ovarian cancers are the second cause of death from gynecological cancers worldwide, due to a late diagnosis combined with the development of resistance to chemotherapy. However, half of these cancers present alterations in Homologous Recombination (HR), making them sensitive to inhibitors of the PARP protein (PARPi), involved in DNA repair. Nevertheless, identifying patients who respond to chemotherapy and selecting those eligible for PARPi remains a challenge for clinicians. In this context, the use of Patient-Derived Tumor Organoids (PDTO) for predictive functional testing represents an interesting prospect for clinical decision making. METHODS: Here we established a panel of 37 long-term PDTO models of various histological subtypes from 31 ovarian cancer patients. Histological and molecular profiles of PDTO were compared to tumor sample of origin using immunohistochemical analyses and global approaches (copy number variation and transcriptomic profiling). PDTO models were exposed to standard drugs for ovarian cancer patients, including PARPi, and response was assessed using viability assay. To further define the HR status of PDTO, we performed a functional assay evaluating the ability of PDTO to initiate HR (RECAP test) using automated histo-imaging quantitative analysis of RAD51 foci, as well as an NGS analysis based on the sequencing of an HR-related genes panel to obtain a Genome Instability Score (GIS). RESULTS: We demonstrated that PDTO mimicked histological and expression of tumor markers of paired tumors. Moreover, non-negative matrix factorization approach revealed that PDTO recapitulated the transcriptomic profile of the cancer component from their sample of origin. Screening of chemotherapeutic drugs showed that PDTO exhibit heterogeneous responses, and that response of PDTO from high-grade serous ovarian carcinoma to carboplatin recapitulated patient response to first-line treatment. Additionally, the detection of HRD phenotype of PDTO using functional assay was associated with the results of the HRD test Genomic Instability Scar (GIScar). CONCLUSION: Although larger-scale investigations are needed to confirm the predictive potential of PDTO, these results provide further evidence of the potential interest of ovarian PDTO for functional precision medicine.
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Cell cycle-dependent, in vitro assembly of microtubules onto pericentriolar material of HeLa cells.
A centriolar complex comprising a pair of centrioles and a cloud of pericentriolar materials is located at the point of covergence of the microtubules of the mitotic apparatus. The in vitro assembly of microtubules was observed onto these complexes in the 1,400 g supernatant fraction of colcemid-blocked, mitotic HeLa cells lysed into solutions containing tubulin and Triton X-100. Dark-field microscopy provided a convenient means by which this process could be visualized directly. When this 1,400 g supernate was incubated at 30 degrees C and centrifuged into a discontinuous sucrose gradient, a band containing centriolar complexes and assembled microtubles was obtained at 50-60% sucrose interface. Ultrastructual analysis indicated that the majority of the microtubules assembled predominantly from the pericentriolar material but also onto the centrioles. When cells were synchronized by a double thymide block, the assembly of microtubules onto centriolar complexes was observed only in lysates of mitotic cells; no assembly was seen in lysed material of interphase cells. Microtubule assembly occured onto centriolar complexes in solutions of either 100,000 g brain supernate, 2 X cycled tubulin, or purified tubulin dimers. This study demonstrates that the pericentriolar material becomes competent as a microtubule-organizing center (MTOC) at the time of mitosis. With use of the techniques described, a method for the isolation of centriolar complexes may be developed.
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High-throughput compound evaluation on 3D networks of neurons and glia in a microfluidic platform.
With great advances in the field of in vitro brain modelling, the challenge is now to implement these technologies for development and evaluation of new drug candidates. Here we demonstrate a method for culturing three-dimensional networks of spontaneously active neurons and supporting glial cells in a microfluidic platform. The high-throughput nature of the platform in combination with its compatibility with all standard laboratory equipment allows for parallel evaluation of compound effects.
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Cell-type-specific profiling of human cellular models of fragile X syndrome reveal PI3K-dependent defects in translation and neurogenesis.
Transcriptional silencing of the FMR1 gene in fragile X syndrome (FXS) leads to the loss of the RNA-binding protein FMRP. In addition to regulating mRNA translation and protein synthesis, emerging evidence suggests that FMRP acts to coordinate proliferation and differentiation during early neural development. However, whether loss of FMRP-mediated translational control is related to impaired cell fate specification in the developing human brain remains unknown. Here, we use human patient induced pluripotent stem cell (iPSC)-derived neural progenitor cells and organoids to model neurogenesis in FXS. We developed a high-throughput, in vitro assay that allows for the simultaneous quantification of protein synthesis and proliferation within defined neural subpopulations. We demonstrate that abnormal protein synthesis in FXS is coupled to altered cellular decisions to favor proliferative over neurogenic cell fates during early development. Furthermore, pharmacologic inhibition of elevated phosphoinositide 3-kinase (PI3K) signaling corrects both excess protein synthesis and cell proliferation in a subset of patient neural cells.
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Isolation of native Mauthner cell axoplasm and an analysis of organelle movement in non-aqueous and aqueous media.
A method for isolating Mauthner cell (M-cell) axoplasm from goldfish is described. The axon may be isolated in a fluorocarbon oil (e.g., Fluorinert), or in an aqueous bathing medium (ABM). An analysis of motile organelles in axoplasm isolated in Fluorinert or in ABM indicated that the range of particle velocities extended over an order of magnitude, and that there was a significant selective slowing of retrograde particle movement in axons isolated in ABM. No apparent correlation between particle size and velocity was noted. In addition to confirming that calcium was not required for particle transport, it was observed that adenylylimidodiphosphate produced an irreversible blockade of organelle movements, suggesting that force generating mechanisms involved in translocation are probably similar to those proposed for invertebrate axons.
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Patient-Derived Tumor Organoids for Guidance of Personalized Drug Therapies in Recurrent Glioblastoma.
An obstacle to effective uniform treatment of glioblastoma, especially at recurrence, is genetic and cellular intertumoral heterogeneity. Hence, personalized strategies are necessary, as are means to stratify potential targeted therapies in a clinically relevant timeframe. Functional profiling of drug candidates against patient-derived glioblastoma organoids (PD-GBO) holds promise as an empirical method to preclinically discover potentially effective treatments of individual tumors. Here, we describe our establishment of a PD-GBO-based functional profiling platform and the results of its application to four patient tumors. We show that our PD-GBO model system preserves key features of individual patient glioblastomas in vivo. As proof of concept, we tested a panel of 41 FDA-approved drugs and were able to identify potential treatment options for three out of four patients; the turnaround from tumor resection to discovery of treatment option was 13, 14, and 15 days, respectively. These results demonstrate that this approach is a complement and, potentially, an alternative to current molecular profiling efforts in the pursuit of effective personalized treatment discovery in a clinically relevant time period. Furthermore, these results warrant the use of PD-GBO platforms for preclinical identification of new drugs against defined morphological glioblastoma features.
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Emerging biomaterials and technologies to control stem cell fate and patterning in engineered 3D tissues and organoids.
The ability to create complex three-dimensional cellular models that can effectively replicate the structure and function of human organs and tissues in vitro has the potential to revolutionize medicine. Such models could facilitate the interrogation of developmental and disease processes underpinning fundamental discovery science, vastly accelerate drug development and screening, or even be used to create tissues for implantation into the body. Realization of this potential, however, requires the recreation of complex biochemical, biophysical, and cellular patterns of 3D tissues and remains a key challenge in the field. Recent advances are being driven by improved knowledge of tissue morphogenesis and architecture and technological developments in bioengineering and materials science that can create the multidimensional and dynamic systems required to produce complex tissue microenvironments. In this article, we discuss challenges for in vitro models of tissues and organs and summarize the current state-of-the art in biomaterials and bioengineered systems that aim to address these challenges. This includes both top-down technologies, such as 3D photopatterning, magnetism, acoustic forces, and cell origami, as well as bottom-up patterning using 3D bioprinting, microfluidics, cell sheet technology, or composite scaffolds. We illustrate the varying ways that these can be applied to suit the needs of different tissues and applications by focussing on specific examples of patterning the bone-tendon interface, kidney organoids, and brain cancer models. Finally, we discuss the challenges and future prospects in applying materials science and bioengineering to develop high-quality 3D tissue structures for in vitro studies.
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Defective EV-mediated transport of SHH alters neural fate specification in EPM1 epilepsy.
The extracellular milieu, including extracellular vesicles (EVs), plays a pivotal role in brain development. In this study, we sought to elucidate the pathogenesis of progressive myoclonus epilepsy type 1 (EPM1), a disease caused by mutations in the CSTB gene, using cerebral organoids (COs) derived from patient cells. The results demonstrate that EPM1 COs display increased electrophysiological activity and disrupted excitatory/inhibitory (E/I) balance. Single-cell RNA sequencing analysis of ventral EPM1-COs revealed an abnormal specification of progenitor fate, with a shift toward dorsal neuron identities. We demonstrated that this misspecification is driven by a functional alteration of the ventral signaling niche, resulting from impaired EV dynamics and altered protein cargo. Mechanistically, we identified Sonic Hedgehog (SHH) as a direct physical interactor of CSTB and demonstrated that CSTB deficiency leads to reduced SHH content and secretion. Our findings establish CSTB as a safeguard of ventral patterning and identify the CSTB-SHH-EV axis as a potential therapeutic target for mitigating the E/I imbalance associated with EPM1.