Striking similarity in the gene expression levels of individual Myc module members among ESCs, EpiSCs, and partial iPSCs

L-myc Gene Expression in Canine Fetal Fibroblasts Promotes Self-Renewal Capacity but Not Tumor Formation

Canines are useful in mammalian preclinical studies because they are larger than rodents and share many diseases with humans. Canine fetal fibroblast cells (CFFs) are an easily accessible source of somatic cells. However, they are easily driven to senescence and become unusable with continuous in vitro culture. Therefore, to overcome these deficiencies, we investigated whether tetracycline-inducible L-myc gene expression promotes self-renewal activity and tumorigenicity in the production of induced conditional self-renewing fibroblast cells (iCSFCs). Here, we describe the characterization of a new iCSFC line immortalized by transduction with L-myc that displays in vitro self-renewal ability without tumorigenic capacity. We established conditionally inducible self-renewing fibroblast cells by transducing CFF-3 cells with L-myc under the tetracycline-inducible gene expression system. In the absence of doxycycline, the cells did not express L-myc or undergo self-renewal. The iCSFCs had a fibroblast-like morphology, normal chromosome pattern, and expressed fibroblast-specific genes and markers. However, the iCSFCs did not form tumors in a soft agar colony-forming assay. We observed higher expression of three ES modules (core pluripotency genes, polycomb repressive complex genes (PRC), and MYC-related genes) in the iCSFCs than in the CFF-3 cells; in particular, the core pluripotency genes (OCT4, SOX2, and NANOG) were markedly up-regulated compared with the PRC and MYC module genes. These results demonstrated that, in canine fetal fibroblasts, L-myc tetracycline-inducible promoter-driven gene expression induces self-renewal capacity but not tumor formation. This study suggests that L-myc gene-induced conditional self-renewing fibroblast cells can be used as an in vitro tool in a variety of biomedical studies related to drug screening.

Stem Cell Transplantation: A Promising Therapy for Spinal Cord Injury

Spinal Cord Injury (SCI) causes irreversible functional loss of the affected population. The incidence of SCI keeps increasing, resulting in huge burden on the society. The pathogenesis of SCI involves neuron death and exotic reaction, which could impede neuron regeneration. In clinic, the limited regenerative capacity of endogenous cells after SCI is a major problem. Recent studies have demonstrated that a variety of stem cells such as induced Pluripotent Stem Cells (iPSCs), Embryonic Stem Cells (ESCs), Mesenchymal Stem Cells (MSCs) and Neural Progenitor Cells (NPCs) /Neural Stem Cells (NSCs) have therapeutic potential for SCI. However, the efficacy and safety of these stem cellbased therapy for SCI remain controversial. In this review, we introduce the pathogenesis of SCI, summarize the current status of the application of these stem cells in SCI repair, and discuss possible mechanisms responsible for functional recovery of SCI after stem cell transplantation. Finally, we highlight several areas for further exploitation of stem cells as a promising regenerative therapy of SCI.

Induced Pluripotent Stem Cell Therapies for Cervical Spinal Cord Injury

Cervical-level injuries account for the majority of presented spinal cord injuries (SCIs) to date. Despite the increase in survival rates due to emergency medicine improvements, overall quality of life remains poor, with patients facing variable deficits in respiratory and motor function. Therapies aiming to ameliorate symptoms and restore function, even partially, are urgently needed. Current therapeutic avenues in SCI seek to increase regenerative capacities through trophic and immunomodulatory factors, provide scaffolding to bridge the lesion site and promote regeneration of native axons, and to replace SCI-lost neurons and glia via intraspinal transplantation. Induced pluripotent stem cells (iPSCs) are a clinically viable means to accomplish this; they have no major ethical barriers, sources can be patient-matched and collected using non-invasive methods. In addition, the patient’s own cells can be used to establish a starter population capable of producing multiple cell types. To date, there is only a limited pool of research examining iPSC-derived transplants in SCI—even less research that is specific to cervical injury. The purpose of the review herein is to explore both preclinical and clinical recent advances in iPSC therapies with a detailed focus on cervical spinal cord injury.

V-myc immortalizes human neural stem cells in the absence of pluripotency-associated traits

A better understanding of the molecular mechanisms governing stem cell self-renewal will foster the use of different types of stem cells in disease modeling and cell therapy strategies. Immortalization, understood as the capacity for indefinite expansion, is needed for the generation of any cell line. In the case of v-myc immortalized multipotent human Neural Stem Cells (hNSCs), we hypothesized that v-myc immortalization could induce a more de-differentiated state in v-myc hNSC lines. To test this, we investigated the expression of surface, biochemical and genetic markers of stemness and pluripotency in v-myc immortalized and control hNSCs (primary precursors, that is, neurospheres) and compared these two cell types to human Embryonic Stem Cells (hESCs) and fibroblasts. Using a Hierarchical Clustering method and a Principal Component Analysis (PCA), the v-myc hNSCs associated with their counterparts hNSCs (in the absence of v-myc) and displayed a differential expression pattern when compared to hESCs. Moreover, the expression analysis of pluripotency markers suggested no evidence supporting a reprogramming-like process despite the increment in telomerase expression. In conclusion, v-myc expression in hNSC lines ensures self-renewal through the activation of some genes involved in the maintenance of stem cell properties in multipotent cells but does not alter the expression of key pluripotency-associated genes.