Preclinical quality, safety, and efficacy of a human embryonic stem cell-derived product for the treatment of Parkinson’s disease, STEM-PD

Cell replacement therapies for Parkinson’s disease (PD) based on transplantation of pluripotent stem cell-derived dopaminergic neurons are now entering clinical trials. Here, we present quality, safety, and efficacy data supporting the first-in-human STEM-PD phase I/IIa clinical trial along with the trial design. The STEM-PD product was manufactured under GMP and quality tested in vitro and in vivo to meet regulatory requirements. Importantly, no adverse effects were observed upon testing of the product in a 39-week rat GLP safety study for toxicity, tumorigenicity, and biodistribution, and a non-GLP efficacy study confirmed that the transplanted cells mediated full functional recovery in a pre-clinical rat model of PD. We further observed highly comparable efficacy results between two different GMP batches, verifying that the product can be serially manufactured. A fully in vivo-tested batch of STEM-PD is now being used in a clinical trial of 8 patients with moderate PD, initiated in 2022

Progenitor cells in the postnatal central nervous system, characterization and genetic manipulation

New neurons are only generated in two places of the postnatal brain; the subventricular zone (SVZ) and hippocampus. The SVZ-derived cells specifically migrate to the olfactory bulb where they give rise to new interneurons. We have genetically manipulated the postnatal SVZ progenitor cells with the aim to direct them to a neuronal fate in the striatum. Our result showed that ectopic expression of the transcription factors Islet1 and Neurogenin2 directed the SVZ cells progeny to a new fate in the striatum and external capsule. Once removed to the culture dish they expressed the neuronal marker ?-III-tubulin. Thus, showing that ectopic expression of Islet1 and Neurogenin2 in the postnatal SVZ progenitor cells promote striatal recruitment for their progeny, which have potential to differentiate into neurons

Retrovirally delivered Islet-1 increases recruitment of Ng2 expressing cells from the postnatal SVZ into the striatum.

Neural stem and progenitor cells hold the promise to be used in cell-based therapies to treat both acute and degenerative neurological diseases. To date, most research has been focused on the use of in vitro propagated stem cells used as a source of cells in cell replacement therapies. However, mobilization of endogenous neural stem cells to generate a specific differentiated cell type offers an attractive alternative. In this study, we investigate the possibility to direct the formation of specific cells from the endogenous stem and progenitor cells residing in the subventricular region of the postnatal brain. With the aim to induce postnatal generation of striatal neurons, we ectopically expressed Islet-1, a LIM homeodomain transcription factor expressed by striatal progenitors during development, in cells of the subventricular zone (SVZ) of neonatal and adult rats. Ectopic expression of Islet-1 in the neonatal, but not adult, SVZ resulted in the appearance of a population of cells in the striatum. These cells were primarily located in the ventrolateral area of the striatum where they differentiate into Ng2 expressing cells. However, no neurogenesis was observed in the striatum, nor was ectopic striatal differentiation observed in any other area of the brain after retroviral expression of Islet-1 in the SVZ. Thus, although ectopic expression of Islet-1 is sufficient to direct the migration of cells into the striatum in neonatal animals, it does not specify a striatal projection neuron phenotype in cells generated from the SVZ after birth. (c) 2006 Elsevier Inc. All rights reserved

Activity-dependent long-term plasticity of afferent synapses on grafted stem/progenitor cell-derived neurons.

Stem cell-based cell replacement therapies aiming at restoring injured or diseased brain function ultimately rely on the capability of transplanted cells to promote functional recovery. The mechanisms by which stem cell-based therapies for neurological conditions can lead to functional recovery are uncertain, but structural and functional repair appears to depend on integration of transplanted cell-derived neurons into neuronal circuitries. The nature by which stem/progenitor cell-derived neurons synaptically integrate into neuronal circuitries is largely unexplored. Here we show that transplanted GFP-labeled neuronal progenitor cells into the rat hippocampus exhibit mature neuronal morphology following 4-10 weeks. GFP-positive cells were preferentially integrated into the principal cell layers of hippocampus, particularly CA3. Patch-clamp recordings from GFP-expressing cells revealed that they generated fast action potentials, and their intrinsic membrane properties were overall similar to endogenous host neurons recorded in same areas. As judged by occurrence of spontaneous excitatory postsynaptic currents (EPSCs), transplanted GFP-positive cells were synaptically integrated into the host circuitry. Comparable to host neurons, both paired-pulse depression and facilitation of afferent fiber stimulation-evoked EPSCs were observed in GFP-positive cells. Upon high-frequency stimulation, GFP-positive cells displayed post-tetanic potentiation of EPSCs, in some cases followed by long-term potentiation (LTP) lasting for more than 30 min. Our data show for the first time that transplanted neuronal progenitor cells can become functional neurons and their afferent synapses are capable of expressing activity-dependent short and long-term plasticity. These synaptic properties may facilitate host-to-graft interactions and regulate activity of the grafted cells promoting functional recovery of the diseased brain

Reprogramming of neonatal SVZ progenitors by Islet-1 and Neurogenin-2.

The subventricular zone (SVZ) lining the lateral walls of the lateral ventricles is one of the major neurogenic areas in the postnatal brain. Precursor cells in the SVZ migrate via the rostral migratory stream to the olfactory bulb where they differentiate into neurons. Cell replacement strategies utilizing the recruitment of these endogenous progenitors and their progeny to different areas of the brain hold great promise for the future, but much research is needed in order to understand the sequence of molecular signals necessary to induce proliferation, migration and site-specific differentiation of these cells. In this study we show that the SVZ cells can be redirected from their normal migration route and directed towards other brain regions when they are infected with retroviruses encoding the developmentally important transcription factors Islet-1 and Neurogenin-2. After co-transduction with these transcription factors, transduced cells could be detected in several areas of the brain. When located in the striatum, the reprogrammed cells displayed neuroblast-like morphology. Once removed from the striatal parenchyma and allowed to further differentiation in vitro they developed into beta-III-tubulin positive neurons