Organoid scale - How big is a microBrain?
StemoniX specializes in growing human iPSC-derived co-cultures of neurons and astrocytes in both 2D and 3D formats. The “micro” part of microBrain refers to the length scale (micrometers, abbreviated µm) at which the cultures form higher-order structures. In 3D, cells cluster together and form spheroids that are ~600 µm (0.6mm) in diameter. These are easily visible to the human eye and can be manipulated with pipettes and using high-throughput liquid handling systems. One of the biggest advantages of these cultures is that they fit into multi-well plates containing up to 384 individual microBrain spheroids (Figure 1a). The consistent formation of spheroids enables true high-throughput screening for neurotoxicity, functional modulation, or other phenotypic studies, providing reproducible data for accelerated drug discovery and disease model development.
microBrain 2D cultures also form higher-order structures on the length scale of 10s to 100s of microns (Figure 1b). The clusters of cells tend to be enriched for neurons and connect to one another via “highways” of neuronal projections. This network organization facilitates communication across entire wells in 96-well and 384-well format plates. These 2D networks of neurons and astrocytes lend themselves perfectly to image-based phenotypic screening, which provides rich multi-dimensional datasets for a variety of applications.
Cellular scale - How big is a neuron?
An individual microBrain 3D spheroid consists of thousands of individual cells. The two primary cell types in StemoniX human cortical spheroids are neurons and astrocytes. Each of these cell types is relatively small (<20µm in diameter), but they can form long projections that stretch to >200µm in length. Neurons are primarily responsible for intercellular
communication and coordinated network activity. Astrocytes play an important regulatory role, providing structural and metabolic support for neurons and modulating neurotransmitter uptake and release. The distinct morphologies of neurons and astrocytes are seen in both 3D spheroids and 2D cultures. Morphological changes in either cell type can be indicative of a particular disease state or toxic response. For example, astrocyte activation (Figure 2a) is a hallmark of numerous neuroinflammatory conditions (e.g., multiple sclerosis, Parkinson’s disease). Neuronal-specific cell death has been observed in Alzheimer’s disease and is recapitulated in microBrain 2D cultures following an amyloid-β insult (Figure 2b). These clear morphological changes can be quantitatively analyzed using in-house imaging systems like the Operetta CLS confocal microscope and Harmony software platforms from Perkin Elmer.
Molecular scale - How big is a synapse?
Synapses facilitate communication between distant neurons, much like two ends of a telephone line. A pre-synaptic neuron will send signals in the form of neurotransmitters (e.g., glutamate, GABA) while a post-synaptic neuron will receive that signal when those neurotransmitters binding to cell surface receptors. Delayed formation of synapses is characteristic of certain neurodevelopmental diseases (e.g., Rett syndrome), while loss of functional synapses is a hallmark of many neurodegenerative ailments (e.g., Alzheimer’s disease).
Imaging these tiny structures is one of the most difficult tasks to any neuroscientist and requires careful sample preparation, precise instrumentation, and sophisticated analysis tools to be done properly. Strong co-localization of pre- and post-synaptic markers is seen in StemoniX microBrain 2D platform verifies the presence of a mature neuronal network and the technical ability of our scientists to image and assess these crucial neuronal elements (Figure 3).
With both microBrain 2D and microBrain 3D, StemoniX brings human biology to the bench – to de-risk and accelerate the drug discovery process.