Genetic approach to track neural cell fate decisions using human embryonic stem cells

Microvesicles from Schwann-Like Cells as a New Biomaterial Promote Axonal Growth

Schwann cells promote axonal regeneration following peripheral nerve injury. However, in terms of clinical treatment, the therapeutic effects of Schwann cells are limited by their source. The transmission of microvesicles from neuroglia cells to axons is a novel communication mechanism in axon regeneration.To evaluate the effect of microvesicles released from Schwann-like cells on axonal regeneration, neural stem cells derived from human embryonic stem cells differentiated into Schwann-like cells, which presented a typical morphology and characteristics similar to those of schwann cells. The glial markers like MBP, P0, P75^NTR, PMP-22, GFAP, HNK-1 and S100 were upregulated, whereas the neural stem markers like NESTIN, SOX1 and SOX2 were significantly downregulated in schwann-like cells. Microvesicles enhanced axonal growth in dorsal root ganglia neurons and regulated GAP43 expression in neuron-like cells (N2A and PC12) through the PTEN/PI3 K/Akt signaling pathway. A 5 mm section of sciatic nerve was transected in Sprague-Dawley rats. With microvesicles transplantation, regenerative nerves were evaluated after 6 weeks. Microvesicles increased sciatic function index scores, delayed gastrocnemius muscle atrophy and elevated βIII-tubulin-labeled axons in vivo. Schwann-like cells serve as a convenient source and promote axonal growth by secreting microvesicles, which may potentially be used as bioengineering materials for nerve tissue repair.

Acquisition of chromosome 1q duplication in parental and genome-edited human-induced pluripotent stem cell-derived neural stem cells results in their higher proliferation rate in vitro and in vivo

Objectives

Genetic engineering of human‐induced pluripotent stem cell‐derived neural stem cells (hiPSC‐NSC) may increase the risk of genomic aberrations. Therefore, we asked whether genetic modification of hiPSC‐NSCs exacerbates chromosomal abnormalities that may occur during passaging and whether they may cause any functional perturbations in NSCs in vitro and in vivo.

Materials and Methods

The transgenic cassette was inserted into the AAVS1 locus, and the genetic integrity of zinc‐finger nuclease (ZFN)‐modified hiPSC‐NSCs was assessed by the SNP‐based karyotyping. The hiPSC‐NSC proliferation was assessed in vitro by the EdU incorporation assay and in vivo by staining of brain slices with Ki‐67 antibody at 2 and 8 weeks after transplantation of ZFN‐NSCs with and without chromosomal aberration into the striatum of immunodeficient rats.

Results

During early passages, no chromosomal abnormalities were detected in unmodified or ZFN‐modified hiPSC‐NSCs. However, at higher passages both cell populations acquired duplication of the entire long arm of chromosome 1, dup(1)q. ZNF‐NSCs carrying dup(1)q exhibited higher proliferation rate than karyotypically intact cells, which was partly mediated by increased expression of AKT3 located on Chr1q. Compared to karyotypically normal ZNF‐NSCs, cells with dup(1)q also exhibited increased proliferation in vivo 2 weeks, but not 2 months, after transplantation.

Conclusions

These results demonstrate that, independently of ZFN‐editing, hiPSC‐NSCs have a propensity for acquiring dup(1)q and this aberration results in increased proliferation which might compromise downstream hiPSC‐NSC applications.

Regeneration of sciatic nerves by transplanted microvesicles of human neural stem cells derived from embryonic stem cells

Injured nerves cannot regenerate on their own, and a lack of engraftable human nerves has been a major obstacle in cell-based therapies for regenerating damaged nerves. A monolayer culture approach to obtain adherent neural stem cells from human embryonic stem cells (hESC-NSCs) was established, and the greatest number of stemness characteristics were achieved by the eighth generation of hESC-NSCs (P8 hESC-NSCs). To overcome deficits in cell therapy, we used microvesicles secreted from P8 hESC-NSCs (hESC-NSC-MVs) instead of entire hESC-NSCs. To investigate the therapeutic efficacy of hESC-NSC-MVs in vitro, hESC-NSC-MVs were cocultured with dorsal root ganglia to determine the length of axons. In vivo, we transected the sciatic nerve in SD rats and created a 5-mm gap. A sciatic nerve defect was bridged using a silicone tube filled with hESC-NSC-MVs (45 μg) in the MVs group, P8 hESC-NSCs (1 × 106 single cells) in the cell group and PBS in the control group. The hESC-NSC-MVs group showed better morphological recovery and a significantly greater number of regenerated axons than the hESC-NSCs group 12 weeks after nerve injury. These results indicated that the hESC-NSC-MVs group had the greatest ability to repair and reconstruct nerve structure and function. As a result, hESC-NSC-MVs may have potential for applications in the field of nerve regenerative repair.

Quantification of dopaminergic neuron differentiation and neurotoxicity via a genetic reporter

Human pluripotent stem cells provide a powerful human-genome based system for modeling human diseases in vitro and for potentially identifying novel treatments. Directed differentiation of pluripotent stem cells produces many specific cell types including dopaminergic neurons. Here, we generated a genetic reporter assay in pluripotent stem cells using newly-developed genome editing technologies in order to monitor differentiation efficiency and compare dopaminergic neuron survival under different conditions. We show that insertion of a luciferase reporter gene into the endogenous tyrosine hydroxylase (TH) locus enables rapid and easy quantification of dopaminergic neurons in cell culture throughout the entire differentiation process. Moreover, we demonstrate that the cellular assay is effective in assessing neuron response to different cytotoxic chemicals and is able to be scaled for high throughput applications. These results suggest that stem cell-derived terminal cell types can provide an alternative to traditional immortal cell lines or primary cells as a quantitative cellular model for toxin evaluation and drug discovery.