Experimental Advances Towards Neural Regeneration from Induced Stem Cells to Direct In Vivo Reprogramming.

Neuronal loss is a common substrate of many neurological diseases that still lack effective treatments and highly burden lives of affected individuals. The discovery of self-renewing stem cells within the central nervous system (CNS) has opened the doors to the possibility of using the plasticity of CNS as a potential strategy for the development of regenerative therapies after injuries. The role of neural progenitor cells appears to be crucial, but insufficient in reparative processes after damage. In addition, the mechanisms that regulate these events are still largely unknown. Stem cell-based therapeutic approaches have primarily focused on the use of either induced pluripotent stem cells or induced neural stem cells as sources for cell transplantation. More recently, in vivo direct reprogramming of endogenous CNS cells into multipotent neural stem/progenitor cells has been proposed as an alternative strategy that could overcome the limits connected with both the invasiveness of exogenous cell transplantation and the technical issues of in vitro reprogramming (i.e., the time requested and the limited available amount of directly induced neuronal cells). In this review, we aim to highlight the recent studies on in vivo direct reprogramming, focusing on astrocytes conversion to neurons or to neural stem/precursors cells, in the perspective of future therapeutic purposes for neurological disorders.

Gene therapy rescues disease phenotype in a spinal muscular atrophy with respiratory distress type 1 (SMARD1) mouse model.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive motor neuron disease affecting children. It is caused by mutations in the IGHMBP2 gene (11q13) and presently has no cure. Recently, adeno-associated virus serotype 9 (AAV9)-mediated gene therapy has been shown to rescue the phenotype of animal models of another lower motor neuron disorder, spinal muscular atrophy 5q, and a clinical trial with this strategy is ongoing. We report rescue of the disease phenotype in a SMARD1 mouse model after therapeutic delivery via systemic injection of an AAV9 construct encoding the wild-type IGHMBP2 to replace the defective gene. AAV9-IGHMBP2 administration restored protein levels and rescued motor function, neuromuscular physiology, and life span (450% increase), ameliorating pathological features in the central nervous system, muscles, and heart. To test this strategy in a human model, we transferred wild-type IGHMBP2 into human SMARD1-induced pluripotent stem cell-derived motor neurons; these cells exhibited increased survival and axonal length in long-term culture. Our data support the translational potential of AAV-mediated gene therapies for SMARD1, opening the door for AAV9-mediated therapy in human clinical trials.

Spinal muscular atrophy phenotype is ameliorated in human motor neurons by SMN increase via different novel RNA therapeutic approaches.

Spinal muscular atrophy (SMA) is a primary genetic cause of infant mortality due to mutations in the Survival Motor Neuron (SMN) 1 gene. No cure is available. Antisense oligonucleotides (ASOs) aimed at increasing SMN levels from the paralogous SMN2 gene represent a possible therapeutic strategy. Here, we tested in SMA human induced pluripotent stem cells (iPSCs) and iPSC-differentiated motor neurons, three different RNA approaches based on morpholino antisense targeting of the ISSN-1, exon-specific U1 small nuclear RNA (ExSpeU1), and Transcription Activator-Like Effector-Transcription Factor (TALE-TF). All strategies act modulating SMN2 RNA: ASO affects exon 7 splicing, TALE-TF increase SMN2 RNA acting on the promoter, while ExSpeU1 improves pre-mRNA processing. These approaches induced up-regulation of full-length SMN mRNA and differentially affected the Delta-7 isoform: ASO reduced this isoform, while ExSpeU1 and TALE-TF increased it. All approaches upregulate the SMN protein and significantly improve the in vitro SMA motor neurons survival. Thus, these findings demonstrate that therapeutic tools that act on SMN2 RNA are able to rescue the SMA disease phenotype. Our data confirm the feasibility of SMA iPSCs as in vitro disease models and we propose novel RNA approaches as potential therapeutic strategies for treating SMA and other genetic neurological disorders.

Therapeutic development in amyotrophic lateral sclerosis.

PURPOSE: Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease in adults. It is almost invariably lethal within a few years after the onset of symptoms. No effective treatment is currently available beyond supportive care and riluzole, a putative glutamate release blocker linked to modestly prolonged survival. This review provides a general overview of preclinical and clinical advances during recent years and summarizes the literature regarding emerging therapeutic approaches, focusing on their molecular targets. METHODS: A systematic literature review of PubMed was performed, identifying key clinical trials involving molecular therapies for ALS. In addition, the ALS Therapy Development Institute website was carefully analyzed, and a selection of ALS clinical trials registered at ClinicalTrials.gov has been included. FINDINGS: In the last several years, strategies have been developed to understand both the genetic and molecular mechanisms of ALS. Several therapeutic targets have been actively pursued, including kinases, inflammation inhibitors, silencing of key genes, and modulation or replacement of specific cell populations. The majority of ongoing clinical trials are investigating the safety profiles and tolerability of pharmacologic, gene, and cellular therapies, and have begun to assess their effects on ALS progression. IMPLICATIONS: Currently, no therapeutic effort seems to be efficient, but recent findings in ALS could help accelerate the discovery of an effective treatment for this disease.