Authors

Sample Characteristics

Journal

Main Findings

Limitations

Conclusions

Camp, et al. (2015)

They use single-cell RNA sequencing (scRNA-seq) to dissect and compare cell composition and progenitor-to-neuron lineage relationships in human cerebral organoids and fetal neocortex.

PNAS

They find that, with some exceptions, the same genes used to build cortical tissue in vivo characterize corticogenesis in vitro. Their data thus show that genetic features underlying human cortical development can be accurately studied in organoid culture systems.

The extent to which in vitro organoid systems recapitulate neural progenitor cell proliferation and neuronal differentiation programs observed in vivo remains unclear.

They concluded that these organoid cortical cells use gene expression programs remarkably similar to those of the fetal tissue to organize into cerebral cortex-like regions.

Kelava and Lancaster (2016b)

They describe advances in the development of these methods, focusing on neural rosette and organoid approaches, and compare their relative capabilities and limitations. They also discuss current technical hurdles for recreating the cell-type complexity and spatial architecture of the brain in culture and offer potential solutions.

Cell stem cell

They find that the combination of higher throughput with dual-SMAD inhibition leads to reproducible forebrain organoids that hold great promise for future therapeutic avenues.

While all three approaches methods are feasible in most tissue culture laboratories, some require more specialized equipment or complicated culture conditions.

They concluded that extraordinary progress has been made in recent years in the development of in vitro models of human brain development.

Muotri (2010)

He presents a critical view on the recent advances obtained from disease modeling using human pluripotent stem cells. The focus on cellular reprogramming as tool to generate patient-specific induced pluripotent stem cells is justified by the great experimental potential, not only for disease modeling, but also as a biotecnological tool for future drug-screening platforms and personalized medicine.

Estudos avançados

They find that the focus on cellular reprogramming as tool to generate patient-specific induced pluripotent stem cells is justified by the great experimental potential, not only for disease modeling, but also as a biotecnological tool for future drug-screening platforms and personalized medicine.

The article analyzes future perspectives of the application of the iPSC and, therefore, it is difficult to predict and to determine its uses and utilities of forceful form.

They concluded that the potential for cellular reprogramming seems to be even limited by human creative ability and ethical principles defined by society.

Lancaster, et al. (2013)

They have developed a human pluripotent stem cell-derived three-dimensional organoid culture system, termed cerebral organoids, that develop various discrete, although interdependent, brain regions. These include a cerebral cortex containing progenitor populations that organize and produce mature cortical neuron subtypes.

Nature

 They demonstrate premature neuronal differentiation in patient organoids, a defect that could help to explain the disease phenotype.

Although considerable progress has been made forin vitro models of whole-organ developmentfor other systems, such as intestine, pituitary and retina, a three-dimensional culture model of the developing brain as a whole has not been established.

They concluded that, together, these data show that three-dimensional organoids can recapitulate development and disease even in this most complex human tissue.

Kelava and Lancaster (2016b)

They focus on the similarities of current organoid methods to in vivo brain development, discuss their limitations and potential improvements, and explore the future venues of brain organoid research.

Elsevier

They find that the development of protocols for different mammalian species will deepen our insight into evolutionary aspects of neurogenesis.

Understandably, in vitro organoid culture takes place without the normally present embryonic surrounding.

They concluded that although tremendous advances have been made in improving the in vitro culture of developing neural tissues, these methods are not without their faults and limitations.

Luo, et al. (2016)

They compared epigenomic and regulatory features in cerebral organoids and human fetal brain, using genome-wide, base resolution DNA methylome and transcriptome sequencing.

Cell reports

They find that molecular markers can be designed from hypo-DMR block regions and facilitate the screening of CO culture conditions that eliminate or reduce the pericentromeric demethylation, which may contribute to greater long-term genomic stability of CO culture.

Organoids derived from human pluripotent stem cells recapitulate the early three-dimensional organization of the human brain, but whether they establish the epigenomic and transcriptional programs essential for brain development is unknown.

They concluded that early non-CG methylation accumulation at superenhancers in both fetal brain and organoids marks forthcoming transcriptional repression in the fully developed brain.

Quadrato, et al. (2017)

They analyse gene expression in over 80,000 individual cells isolated from 31 human brain organoids. We find that organoids can generate a broad diversity of cells, which are related to endogenous classes, including cells from the cerebral cortex and the retina

Nature

They find that 3D brain organoids have the potential to model higher-order functions of the human brain, such as cellular interactions and neural circuit dysfunctions related to neurodevelopmental and neuropsychiatric pathologies.

The cells generated within organoids and the extent to which they recapitulate the regional complexity, cellular diversity and circuit functionality of the brain remain undefined.

They concluded that neuronal activity within organoids could be controlled using light stimulation of photosensitive cells, which may offer a way to probe the functionality of human neuronal circuits using physiological sensory stimuli.

Huch, et al. (2017)

In this Spotlight article, Meritxell Huch and Juergen Knoblich begin by discussing the exciting promise of organoid technology and give concrete examples of how this promise is starting to be realised. In the second part, Matthias Lutolf and Alfonso Martinez-Arias offer a careful and considered view of the state of the organoid field and its current limitations, and lay out the approach they feel is necessary to maximise the potential of organoid technology.

The company of biologists

They find that bioreactor technology or engineered blood vessel systems may be employed to address the major problem of nutrient availability in growing organoids and thereby allow proper longterm growth of complex systems.

There is no doubt that this technology opens up a world of possibilities for scientific discovery in developmental biology as well as in translational research, but whether organoids can truly live up to this challenge is, for some, still an open question.

They concluded that organoids have revealed what developmental biologists have suspected for years: that cells have amazing self-organising abilities, the regulation of which is only just beginning to emerge.

Watanabe, et al. (2017)

They describe optimized organoid culture methods that efficiently and reliably produce cortical and basal ganglia structures similar to those in the human fetal brain in vivo.

Cell reports

They find that even though infants exposed to ZIKV might escape structural brain defects, their risk for neurodevelopmental and neuropsychiatric disorders may be significantly elevated.

However, many organoid differentiation protocols are inefficient and display marked variability in their ability to recapitulate the three-dimensional architecture and course of neurogenesis in the developing human brain.

They concluded that although the predictive value of the organoid system requires further validation, their studies demonstrate its power in singling out therapeutic candidates meriting future investigations.

Bredenoord, et al. (2017)

They describe the current state of research and discuss the ethical implications of organoid technology

Science

They find that only by engaging in constructive interdisciplinary dialog around these issues, involving not only scientists but also patients, policy-makers, clinicians, ethicists, and the public, can we ensure responsible innovation and long-term acceptance of this exciting technology.

Organoid research also raises additional ethical questions that require reexamination and potential recalibration of ethical and legal policies.

They concluded that organoids face several layers of complexity, not only technologically but also with regard to their ethical introduction in research, clinical care, and society.

Lancaster and Knoblich (2014)

They describe a recently established protocol for generating 3D brain tissue, so-called cerebral organoids, which closely mimics the endogenous developmental program. This method can easily be implemented in a standard tissue culture room and can give rise to developing cerebral cortex, ventral telencephalon, choroid plexus and retinal identities, among others, within 1–2 months.

Nature

They find that this system is perhaps most suited to examining neurodevelopmental disorders, as it best recapitulates the early developing brain (first trimester, on the basis of histological comparisons).

As in all in vitro systems, the method lacks surrounding embryonic tissues that are important for the interplay of neural and non-neural tissue cross-talk.

 They concluded that as organoids can be maintained for more than 1 year in long-term culture, they also have the potential to model later events such as neuronal maturation and survival.

Sloan, et al. (2017)

They present an approach for generating astrocyte lineage cells in a three-dimensional (3D) cytoarchitecture using human cerebral cortical spheroids (hCSs) derived from pluripotent stem cells.

Neuron

They find that because many of the genes involved in synaptogenic and synapse pruning pathways are tightly correlated with astrocyte maturation state, it is possible that the development of abnormal neural circuits in various neurodevelopmental disorders may be related to the inappropriate timing and/or degree of astrocyte maturation

.

Because of technical limitations, human astrocytes have received particularly little study

They concluded that hCS-derived glia closely resemble primary human fetal astrocytes and that, over time in vitro, they transition from a predominantly fetal to an increasingly mature astrocyte state.

Clevers (2016)

They present that organoid technology can therefore be used to model human organ development and various human pathologies ‘in a dish.’’ Additionally, patient-derived organoids hold promise to predict drug response in a personalized fashion.

Cell

They find that from a basic science perspective, PSC-based organoids will by their very nature play a key role in understanding the developmental biology of organs and will thus complement the long tradition of in vivo studies in this field.

The current versions of organoids have clear limitations,e.g., innervation, blood vessels, and immune cells are absent, and as a consequence, disease processes are only partially recapitulated.

They concluded that organoids open up new avenues for regenerative medicine and, in combination with editing technology, for gene therapy. The many potential applications of this technology are only beginning to be explored.

Zhu, et al. (2017)

They propose a human induced pluripotent stem cell (hiPSC)-based 3D brain organoid model, and explore the mechanisms underlying neural dysfunctions in prenatal alcohol exposure (PAE) in vitro.

Integrative biology

They find that lthough the molecular mechanism underlying the modulation of the excitatory–inhibitory balance is not yet known, their results indicate that ethanol may disturb neuronal subtypes by altering the neuronal response to signals involved in neural terminal differentiation.

A comprehensive understanding of fetal brain development under ethanol exposure is challenging due to the limitations of animal models.

They concluded that with ethanol exposure, the brain organoids displayed attenuated neurite outgrowth and skewed neural maturation.

Jo, et al. (2016)

They developed a method to differentiate human pluripotent stem cells into a large multicellular organoid-like structure that contains distinct layers of neuronal cells expressing characteristic markers of human midbrain. Importantly, we detected electrically active and functionally mature mDA neurons and dopamine production in our 3D midbrain-like organoids (MLOs).

Cell stem cell

They find that mDA neurons within the hMLOs produced DA, exhibited mature neuronal properties, and were able to form synapses with other neurons within the hMLOs.

A 3D organoid model of the midbrain containing functional midbrain dopaminergic (mDA) neurons has not been reported.

They concluded that MLOs bearing features of the human midbrain may provide a tractable in vitro system to study the human midbrain and its related diseases.