Grafted human pluripotent stem cell-derived cortical neurons integrate into adult human cortical neural circuitry

Abstract

Several neurodegenerative diseases cause loss of cortical neurons, leading to sensory, motor, and cognitive impairments. Studies in different animal models have raised the possibility that transplantation of human cortical neuronal progenitors, generated from pluripotent stem cells, might be developed into a novel therapeutic strategy for disorders affecting cerebral cortex. For example, we have shown that human longterm neuroepithelial-like stem (lt-NES) cell-derived cortical neurons, produced from induced pluripotent stem cells and transplanted into stroke-injured adult rat cortex, improve neurological deficits and establish both afferent and efferent morphological and functional connections with host cortical neurons. So far, all studies with human pluripotent stem cell-derived neurons have been carried out using xenotransplantation in animal models. Whether these neurons can integrate also into adult human brain circuitry is unknown. Here, we show that cortically fated lt-NES cells, which are able to form functional synaptic networks in cell culture, differentiate to mature, layer-specific cortical neurons when transplanted ex vivo onto organotypic cultures of adult human cortex. The grafted neurons are functional and establish both afferent and efferent synapses with adult human cortical neurons in the slices as evidenced by immuno-electron microscopy, rabies virus retrograde monosynaptic tracing, and whole-cell patch-clamp recordings. Our findings provide the first evidence that pluripotent stem cell-derived neurons can integrate into adult host neural networks also in a human-to-human grafting situation, thereby supporting their potential future clinical use to promote recovery by neuronal replacement in the patient's diseased brain.

Neuronal Replacement in Stem Cell Therapy for Stroke: Filling the Gap

“…In this respect, our group has recently demonstrated using rat stroke model and long-term neuroepithelial-like cells from human origin that neuronal activity from grafted cells participate in the maintenance of normal motor function, allegedly contributing to the improved recovery of the animals ( Palma-Tortosa et al, 2020 ). Moreover, our recent study using organotypic cultures of adult human cortex showed that similar integration occurs also in a human-to-human transplantation setting ( Gronning Hansen et al, 2020 ).…”

“…However, even giving the importance of these studies, they have all been conducted using xenotransplantation of human cells in animal models of neurological disorders. Addressing this issue, recent publication from our group has demonstrated that human iPSC-derived cortical progenitors transplanted into human adult cortical tissue, not only survive and give rise to mature cortical neurons, but also exhibit electrophysiological and ultrastructural properties of functional neurons and establish afferent and efferent synaptic connections with the host human cortical neurons, as evidenced by both, rabies virus monosynaptic tracing and electron microscopy ( Gronning Hansen et al, 2020 ). This is the first evidence that human PSCs can integrate into adult human neural network and supports the potential clinical use of PSCs to restore neuronal damaged network in patient with brain disorders.…”

Glutamatergic Neurons Differentiated from Embryonic Stem Cells: An Investigation of Differentiation and Associated Diseases

“…For example, there are studies on the migration of glutamatergic neurons and on cortical patterning during development; these have been reviewed in detail elsewhere [ 46 ]. Recently, it was shown that pluripotent stem cell-derived neurons can integrate adult host neural networks also in a human-to-human grafting situation [ 47 ]. To date, how progenitor cells and neurons that have been derived from the various other types of stem cells in vitro are able to eventually successfully integrate into existing tissue remains a major issue.…”

Induced Pluripotent Stem Cells for Ischemic Stroke Treatment

“…iPSCs promoted synapse formation between host neurons, as demonstrated by fluorogold and synaptophysin staining of the host brain, and regulated the activity of transplanted neurons ( Gomi et al, 2012 ; Tornero et al, 2017 ). In studies of human-to-human transplantation, neurons derived from PSCs were confirmed to have integrated into the adult host neural network ( Grønning Hansen et al, 2020 ). Positive co-staining of presynaptic vesicle markers in some transplanted cells indicated these cells to participate in synaptic transmission.…”