Downregulation of PMP22 ameliorates myelin defects in iPSC-derived human organoid cultures of CMT1A

hESC- and hiPSC-derived Schwann cells are molecularly comparable and functionally equivalent

Establishing robust models of human myelinating Schwann cells is critical for studying peripheral nerve injury and disease. Stem cell differentiation has emerged as a key human cell model and disease motivating development of Schwann cell differentiation protocols. Human embryonic stem cells (hESCs) are considered the ideal pluripotent cell but ethical concerns regarding their use have propelled the popularity of human induced pluripotent stem cells (hiPSCs). Given that the equivalence of hESCs and hiPSCs remains controversial, we sought to compare the molecular and functional equivalence of hESC- and hiPSC-derived Schwann cells generated with our previously reported protocol. We identified only modest transcriptome differences by RNA sequencing and insignificant proteome differences by antibody array. Additionally, both cell types comparably improved nerve regeneration and function in a chronic denervation and regeneration animal model. Our findings demonstrate that Schwann cells derived from hESCs and hiPSCs with our protocol are molecularly comparable and functionally equivalent.

Advances and challenges in modeling inherited peripheral neuropathies using iPSCs

Inherited peripheral neuropathies (IPNs) are a group of diseases associated with mutations in various genes with fundamental roles in the development and function of peripheral nerves. Over the past 10 years, significant advances in identifying molecular disease mechanisms underlying axonal and myelin degeneration, acquired from cellular biology studies and transgenic fly and rodent models, have facilitated the development of promising treatment strategies. However, no clinical treatment has emerged to date. This lack of treatment highlights the urgent need for more biologically and clinically relevant models recapitulating IPNs. For both neurodevelopmental and neurodegenerative diseases, patient-specific induced pluripotent stem cells (iPSCs) are a particularly powerful platform for disease modeling and preclinical studies. In this review, we provide an update on different in vitro human cellular IPN models, including traditional two-dimensional monoculture iPSC derivatives, and recent advances in more complex human iPSC-based systems using microfluidic chips, organoids, and assembloids.

Brain organoids engineered to give rise to glia and neural networks after 90 days in culture exhibit human-specific proteoforms

Human brain organoids are emerging as translationally relevant models for the study of human brain health and disease. However, it remains to be shown whether human-specific protein processing is conserved in human brain organoids. Herein, we demonstrate that cell fate and composition of unguided brain organoids are dictated by culture conditions during embryoid body formation, and that culture conditions at this stage can be optimized to result in the presence of glia-associated proteins and neural network activity as early as three-months in vitro. Under these optimized conditions, unguided brain organoids generated from induced pluripotent stem cells (iPSCs) derived from male-female siblings are similar in growth rate, size, and total protein content, and exhibit minimal batch-to-batch variability in cell composition and metabolism. A comparison of neuronal, microglial, and macroglial (astrocyte and oligodendrocyte) markers reveals that profiles in these brain organoids are more similar to autopsied human cortical and cerebellar profiles than to those in mouse cortical samples, providing the first demonstration that human-specific protein processing is largely conserved in unguided brain organoids. Thus, our organoid protocol provides four major cell types that appear to process proteins in a manner very similar to the human brain, and they do so in half the time required by other protocols. This unique copy of the human brain and basic characteristics lay the foundation for future studies aiming to investigate human brain-specific protein patterning (e.g., isoforms, splice variants) as well as modulate glial and neuronal processes in an in situ-like environment.

Advanced Cellular Models for Rare Disease Study: Exploring Neural, Muscle and Skeletal Organoids

Organoids are self-organized, three-dimensional structures derived from stem cells that can mimic the structure and physiology of human organs. Patient-specific induced pluripotent stem cells (iPSCs) and 3D organoid model systems allow cells to be analyzed in a controlled environment to simulate the characteristics of a given disease by modeling the underlying pathophysiology. The recent development of 3D cell models has offered the scientific community an exceptionally valuable tool in the study of rare diseases, overcoming the limited availability of biological samples and the limitations of animal models. This review provides an overview of iPSC models and genetic engineering techniques used to develop organoids. In particular, some of the models applied to the study of rare neuronal, muscular and skeletal diseases are described. Furthermore, the limitations and potential of developing new therapeutic approaches are discussed.

Schwann cells are axo-protective after injury irrespective of myelination status in mouse Schwann cell-neuron cocultures

Myelinating Schwann cell (SC)-dorsal root ganglion (DRG) neuron cocultures are an important technique for understanding cell-cell signalling and interactions during peripheral nervous system (PNS) myelination, injury, and regeneration. Although methods using rat SCs and neurons or mouse DRG explants are commonplace, there are no established protocols for compartmentalised myelinating cocultures with dissociated mouse cells. There consequently is a need for a coculture protocol that allows separate genetic manipulation of mouse SCs or neurons, or use of cells from different transgenic animals to complement in vivo mouse experiments. However, inducing myelination of dissociated mouse SCs in culture is challenging. Here, we describe a new method to coculture dissociated mouse SCs and DRG neurons in microfluidic chambers and induce robust myelination. Cocultures can be axotomised to study injury and used for drug treatments, and cells can be lentivirally transduced for live imaging. We used this model to investigate axon degeneration after traumatic axotomy and find that SCs, irrespective of myelination status, are axo-protective. At later timepoints after injury, live imaging of cocultures shows that SCs break up, ingest and clear axonal debris.

Using Human iPSC-Derived Peripheral Nervous System Disease Models for Drug Discovery

Induced pluripotent stem cells (IPSCs), with their remarkable ability to differentiate into various cell types, including peripheral nervous system cells such as neurons and glial cells, offer an excellent platform for in vitro disease modeling. These iPSC-derived disease models have proven valuable in drug discovery, as they provide more precise simulations of a patient's disease state and allow for the assessment of potential therapeutic effectiveness and safety.