Gene Correction Recovers Phagocytosis in Retinal Pigment Epithelium Derived from Retinitis Pigmentosa-Human-Induced Pluripotent Stem Cells.

Hereditary retinal dystrophies (HRD) represent a significant cause of blindness, affecting mostly retinal pigment epithelium (RPE) and photoreceptors (PRs), and currently suffer from a lack of effective treatments. Highly specialized RPE and PR cells interact mutually in the functional retina, therefore primary HRD affecting one cell type leading to a secondary HRD in the other cells. Phagocytosis is one of the primary functions of the RPE and studies have discovered that mutations in the phagocytosis-associated gene Mer tyrosine kinase receptor (MERTK) lead to primary RPE dystrophy. Treatment strategies for this rare disease include the replacement of diseased RPE with healthy autologous RPE to prevent PR degeneration. The generation and directed differentiation of patient-derived human-induced pluripotent stem cells (hiPSCs) may provide a means to generate autologous therapeutically-relevant adult cells, including RPE and PR. However, the continued presence of the MERTK gene mutation in patient-derived hiPSCs represents a significant drawback. Recently, we reported the generation of a hiPSC model of MERTK-associated Retinitis Pigmentosa (RP) that recapitulates disease phenotype and the subsequent creation of gene-corrected RP-hiPSCs using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9. In this study, we differentiated gene-corrected RP-hiPSCs into RPE and found that these cells had recovered both wild-type MERTK protein expression and the lost phagocytosis of fluorescently-labeled photoreceptor outer segments observed in uncorrected RP-hiPSC-RPE. These findings provide proof-of-principle for the utility of gene-corrected hiPSCs as an unlimited cell source for personalized cell therapy of rare vision disorders.

Activation of Neurogenesis in Multipotent Stem Cells Cultured In Vitro and in the Spinal Cord Tissue After Severe Injury by Inhibition of Glycogen Synthase Kinase-3.

The inhibition of glycogen synthase kinase-3 (GSK-3) can induce neurogenesis, and the associated activation of Wnt/ß-catenin signaling via GSK-3 inhibition may represent a means to promote motor function recovery following spinal cord injury (SCI) via increased astrocyte migration, reduced astrocyte apoptosis, and enhanced axonal growth. Herein, we assessed the effects of GSK-3 inhibition in vitro on the neurogenesis of ependymal stem/progenitor cells (epSPCs) resident in the mouse spinal cord and of human embryonic stem cell-derived neural progenitors (hESC-NPs) and human-induced pluripotent stem cell-derived neural progenitors (hiPSC-NPs) and in vivo on spinal cord tissue regeneration and motor activity after SCI. We report that the treatment of epSPCs and human pluripotent stem cell-derived neural progenitors (hPSC-NPs) with the GSK-3 inhibitor Ro3303544 activates ß-catenin signaling and increases the expression of the bIII-tubulin neuronal marker; furthermore, the differentiation of Ro3303544-treated cells prompted an increase in the number of terminally differentiated neurons. Administration of a water-soluble, bioavailable form of this GSK-3 inhibitor (Ro3303544-Cl) in a severe SCI mouse model revealed the increased expression of bIII-tubulin in the injury epicenter. Treatment with Ro3303544-Cl increased survival of mature neuron types from the propriospinal tract (vGlut1, Parv) and raphe tract (5-HT), protein kinase C gamma-positive neurons, and GABAergic interneurons (GAD65/67) above the injury epicenter. Moreover, we observed higher numbers of newly born BrdU/DCX-positive neurons in Ro3303544-Cl-treated animal tissues, a reduced area delimited by astrocyte scar borders, and improved motor function. Based on this study, we believe that treating animals with epSPCs or hPSC-NPs in combination with Ro3303544-Cl deserves further investigation towards the development of a possible therapeutic strategy for SCI.

Organized Neurogenic-Niche-Like Pinwheel Structures Discovered in Spinal Cord Tissue-Derived Neurospheres.

The neurogenic niche of the subventricular zone (SVZ) in adult brain tissue takes the form of a pinwheel-like cytoarchitectural structure, with mono-ciliated astrocytes displaying neural stem cell (NSC) characteristics present in the core surrounded by ciliated ependymal cells. For the first time, we have demonstrated the formation of similar pinwheel structures in spinal cord and SVZ tissue-derived neurospheres cultured in vitro. To investigate whether the organization and integrity of these pinwheel structures depends on the appropriate organization of ciliated astrocytes and ependymal cells, we modified neurosphere cell arrangements via the application of the methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dc) or the antiviral drug ganciclovir (GCV) in transgenic mice expressing herpes simplex virus thymidine kinase from the GFAP promoter (GFAP-TK). Treatment of neurospheres with 5-aza-dc increased FoxJ1 expression, a crucial factor for ciliogenesis, by reducing methylation of the FoxJ1 CpG island. 5-aza-dc also increased the expression of the astrocyte marker GFAP and caused aberrant accumulation of ciliated astrocytes. However, the ablation of dividing astrocytes within neurospheres by GCV treatment led to an increase in the accumulation of ciliated ependymal cells, as evidenced by the increased expression of the ependymal cell markers Vimentin or CD24. While 5-aza-dc and GCV treatment differentially affected cell arrangement, both compounds significantly diminished the number of pinwheel structures present in neurospheres. Thus, we suggest that the ratio of ciliated astrocytes to ependymal cells plays a crucial role in the correct formation of the pinwheel structures in spinal cord tissue-derived neurospheres in vitro.

Generation of human induced pluripotent stem cell (iPSC) line from an unaffected female carrier of mutation in SACSIN gene.

The human iPSC cell line, CARS-FiPS4F1 (ESi064-A), derived from dermal fibroblast from the apparently healthy carrier of the mutation of the gene SACSIN, was generated by non-integrative reprogramming technology using OCT3/4, SOX2, CMYC and KLF4 reprogramming factors. The pluripotency was assessed by immunocytochemistry and RT-PCR. This iPSC line can be used as control for Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) disease.

Generation of a human iPSC line from a patient with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) caused by mutation in SACSIN gene.

The human iPSC cell line, ARS-FiPS4F1 (ESi063-A), derived from dermal fibroblast from the patient autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) caused by mutations on the gene SACSIN, was generated by non-integrative reprogramming technology using OCT3/4, SOX2, CMYC and KLF4 reprogramming factors. The pluripotency was assessed by immunocytochemistry and RT-PCR. Differentiation capacity was verified in vitro. This iPSC line can be further differentiated toward affected cells to better understand molecular mechanisms of disease and pathophysiology.