Establishment and characterization of a noradrenergic adrenal chromaffin cell line, tsAM5NE, immortalized with the temperature-sensitive SV40 T-antigen

We established a clonal adrenal medullary cell line, named tsAM5NE, from transgenic mice harbouring the temperature-sensitive Simian virus 40 large T-antigen gene, under the control of the tyrosine hydroxylase promoter. tsAM5NE cells conditionally grew at a permissive temperature of 33°C and exhibited the noradrenergic chromaffin cell phenotype. To understand the characteristics of tsAM5NE cells, we first examined the responsiveness of the cells to ligands of the GDNF (glial cell line-derived neurotrophic factor) family. tsAM5NE cells proliferated at the permissive temperature of 33°C in response to either GDNF or neurturin, but not artemin or persephin. At the non-permissive temperature of 39°C, GDNF or neurturin caused tsAM5NE cells to differentiate into neuron-like cells; however, the differentiated cells died in a time-dependent manner. Interestingly, LIF (leukaemia inhibitory factor) did not affect the GDNF-mediated cell proliferation at 33°C, but promoted the survival and differentiation of GDNF-treated cells at 39°C. In the presence of GDNF plus LIF, the morphological change induced by the temperature shift was associated with up-regulated expression of neuronal markers, indicating that the cells had indeed undergone neuronal differentiation. Thus, we demonstrated that tsAM5NE cells had the capacity to terminally differentiate into neuron-like cells in response to GDNF plus LIF when the oncogene was inactivated by the temperature shift. Thus, this cell line provides a useful model system for studying the mechanisms regulating neuronal differentiation.     

Functional characterization of a conditionally immortalized mouse epididymis caput epithelial cell line MEPC5 using temperature-sensitive simian virus 40 large T-antigen

A conditionally immortalized epididymis caput cell line, MEPC5, was established by infecting primary cultured mouse epididymis caput cells with a temperature-sensitive simian virus 40 large T-antigen. At a permissive temperature of 33 degrees C, the large T-antigen was expressed and the cells grew continuously. However, the downregulation of T-antigen at a nonpermissive temperature of 39 degrees C and the upregulation of cell density at 33 degrees C were associated with growth arrest and the increased protein expression of p21(waf1), a cell cycle inhibitor. The cells expressed epididymal caput-expressed genes such as phosphatidylethanolamine binding protein, polyoma enhancer activator 3, ME1, sulfated glycoprotein-2 (SGP-2), androgen receptor, and retinoic acid receptor alpha. Interestingly, the expression levels of ME1 and SGP-2 were significantly elevated under the cell growth-restricted conditions. The established mouse epididymis caput epithelial cell line MEPC5 retains some characteristics of differentiated epididymis epithelial cells, and should prove an excellent model for studies of gene expression and the physiological functions of epididymis caput epithelial cells.     

Genetic networks in nonpermissive temperature-induced cell differentiation of Sertoli TTE3 cells harboring temperature-sensitive SV40 large T-antigen

To identify the molecular basis by which nonpermissive temperature (NPT) induces cell differentiation in Sertoli TTE3 cells harboring temperature-sensitive SV40 large T-antigen, we performed global scale microarray and computational gene network analyses. In TTE3 cells, inactivation of the large T-antigen by a NPT at 39 degrees C led to cell differentiation accompanying elevation of transferrin, a marker for differentiation of Sertoli cells, and CDKN1A, a cyclin-dependent kinase inhibitor. Of the 22,690 probe sets analyzed, NPT down-regulated 498 probe sets and up-regulated 432 probe sets by >2.0-fold. Hierarchical clustering analysis showed six gene clusters. In the down-regulated cluster I, a significant genetic network including fibronectin 1 was associated with cellular growth and proliferation. In up-regulated cluster IV, a significant genetic network including CDKN1A was associated with cellular differentiation. The present results provide additional novel insights into the molecular basis of cell differentiation induced by NPT in cells.     

Endogenous butyrylcholinesterase in SV40 transformed cell lines: COS-1, COS-7, MRC-5 SV40, and WI-38 VA13

Summary Comparison of proteins expressed by SV40 transformed cell lines and untransformed cell lines is of interest because SV40 transformed cells are immortal, whereas untransformed cells senesce after about 50 doublings. In MRC-5 SV40 cells, only seven proteins have previously been reported to shift from undetectable to detectable after transformation by SV40 virus. We report that butyrylcholinesterase is an 8th protein in this category. Butyrylcholinesterase activity in transformed MRC-5 SV40 cells increased at least 150-fold over its undetectable level in MRC-5 parental cells. Other SV40 transformed cell lines, including COS-1, COS-7, and WI-38 VA13, also expressed endogenous butyrylcholinesterase, whereas the parental, untransformed cell lines, CV-1 and WI-38, had no detectable butyrylcholinesterase activity or mRNA. Infection of CV-1 cells by SV40 virus did not result in expression of butyrylcholinesterase, showing that the butyrylcholinesterase promoter was not activated by the large T antigen of SV40. We conclude that butyrylcholinesterase expression resulted from events related to cell immortalization and did not result from activation by the large T antigen.     

Immortalization of neuronal progenitors using SV40 large T antigen and differentiation towards dopaminergic neurons

Transplantation is common in clinical practice where there is availability of the tissue and organ. In the case of neurodegenerative disease such as Parkinson's disease (PD), transplantation is not possible as a result of the non‐availability of tissue or organ and therefore, cell therapy is an innovation in clinical practice. However, the availability of neuronal cells for transplantation is very limited. Alternatively, immortalized neuronal progenitors could be used in treating PD. The neuronal progenitor cells can be differentiated into dopaminergic phenotype. Here in this article, the current understanding of the molecular mechanisms involved in the differentiation of dopaminergic phenotype from the neuronal progenitors immortalized with SV40 LT antigen is discussed. In addition, the methods of generating dopaminergic neurons from progenitor cells and the factors that govern their differentiation are elaborated. Recent advances in cell‐therapy based transplantation in PD patients and future prospects are discussed.     

A virus-producing cell line developed by transformation of human parapharyngeal cells with SV40

Summary Normal cultures of epithelial appearance were initiated by trypsinization of a surgically resected, histologically normal branchial cyst. Cellular morphology was consistent with derivation from the stratified squamous epithelium of the cyst or from vascular endothelium, although electron micrographs of the cultured cells failed to show any junctional complexes. Infection with SV40 produced transformants which were also epithelioid in appearance. These grew vigorously for 22 to 50 population doublings (about 23 to 32 subcultures, depending upon regimen) and then became quiescent. During this evolution, virus was detectable at all stages by both direct isolation (cell extracts) and cocultivation with permissive cells. In two sublines in which selection for rapidly growing cell types occurred, virus was detected only by cocultivation. The work confirms that of others in the finding that normal human epithelial cells are susceptible to transformation by oncogenic viruses, but are apparently less responsive than are fibroblasts to such transforming agents. It also suggests that subcultivation techniques that maintain the populations of transformed cells at low density tend to select against cell strains that are continuous producers of infectious virus. This study was supported by Grant CA 13494 from the National Cancer Institute.     

Genes involved in nonpermissive temperature-induced cell differentiation in Sertoli TTE3 cells bearing temperature-sensitive simian virus 40 large T-antigen

Sertoli TTE3 cells, derived from transgenic mice bearing temperature-sensitive simian virus 40 large T (tsSV40LT)-antigen, proliferated continuously at a permissive temperature (33 degrees C) whereas inactivation of the large T-antigen by a nonpermissive temperature (39 degrees C) led to differentiation as judged by elevation of transferrin. To clarify the detailed mechanisms of differentiation, we investigated the time course of changes in gene expression using cDNA microarrays. Of the 865 genes analyzed, 14 genes showed increased levels of expression. Real-time quantitative PCR revealed that the mRNA levels of p21(waf1), milk fat globule membrane protein E8, heat-responsive protein 12, and selenoprotein P were markedly elevated. Moreover, the differentiated condition induced by the nonpermissive temperature significantly increased mRNA levels of these four genes in several cell lines from the transgenic mice bearing the oncogene. The present results regarding changes in gene expression will provide a basis for a further understanding of molecular mechanisms of differentiation in both Sertoli cells and cell lines transformed by tsSV40LT-antigen.     

Immortalized mesenchymal stem cells: an alternative to primary mesenchymal stem cells in neuronal differentiation and neuroregeneration associated studies

Background  

Mesenchymal stem cells (MSCs) can be induced to differentiate into neuronal cells under appropriate cellular conditions and transplanted in brain injury and neurodegenerative diseases animal models for neuroregeneration studies. In contrast to the embryonic stem cells (ESCs), MSCs are easily subject to aging and senescence because of their finite ability of self-renewal. MSCs senescence seriously affected theirs application prospects as a promising tool for cell-based regenerative medicine and tissue engineering. In the present study, we established a reversible immortalized mesenchymal stem cells (IMSCs) line by using SSR#69 retrovirus expressing simian virus 40 large T (SV40T) antigen as an alternative to primary MSCs.     

Lithium enhances the neuronal differentiation of neural progenitor cells in vitro and after transplantation into the avulsed ventral horn of adult rats through the secretion of brain-derived neurotrophic factor

This study was undertaken to elucidate the molecular mechanisms by which lithium regulates the development of spinal cord-derived neural progenitor cells (NPCs) in vitro and after transplanted in vivo . Our results show that lithium at the therapeutic concentration significantly increases the proliferation and neuronal differentiation of NPCs in vitro. Specific ELISAs, western blotting, and quantitative real-time RT-PCR assays demonstrate that lithium treatment significantly elevates the expression and production of brain-derived neurotrophic factor (BDNF) by NPCs in culture. Application of a BDNF neutralizing antibody in culture leads to a marked reduction in the neurogenesis of lithium-treated NPCs to the control level. However, it shows no effects on the proliferation of lithium-treated NPCs. These findings suggest that the BDNF pathway is possibly involved in the supportive role of lithium in inducing NPC neurogenesis but not proliferation. This study also provides evidence that lithium is able to elevate the neuronal generation and BDNF production of NPCs after transplantation into the adult rat ventral horn with motoneuron degeneration because of spinal root avulsion, which highlights the therapeutic potential of lithium in cell replacement strategies for spinal cord injury because of its ability to promote neuronal differentiation and BDNF production of grafted NPCs in the injured spinal cord.     

Identification of genes up-regulated by retinoic-acid-induced differentiation of the human neuronal precursor cell line NTERA-2 cl.D1

The human teratocarcinoma cell line NTERA-2 cl.D1 (NT2 cells) can be induced with retinoic acid and cell aggregation to yield postmitotic neurones. This seems to model the in vivo situation, as high concentrations of retinoic acid, retinoic acid binding proteins, and receptors have been detected in the embryonic CNS and the developing spinal cord suggesting a role for retinoic acid in neurogenesis. Suppression subtractive hybridization was used to detect genes up-regulated by this paradigm of neuronal differentiation. Microfibril-associated glycoprotein 2 was found to be drastically up-regulated and has not been implicated in neuronal differentiation before. Suppression subtractive hybridization also identified DYRK4, a homologue of the Drosophila gene minibrain. Minibrain mutations result in specific defects in the development of the fly central nervous system. In adult rats, DYRK4 is only expressed in testis, but our results suggest an additional role for DYRK4 in neuronal differentiation. We have shown that suppression subtractive hybridization in conjunction with an efficient screening procedure is a valuable tool to produce a repertoire of differentially expressed genes and propose a new physiological role for several identified genes and expressed sequence tags.     

Growth inhibition, morphological differentiation and stimulation of survival in neuronal cell type (Neuro-2a) treated with trophic molecules

Trophic molecules are key regulators of survival, growth and differentiation of neural cells. Neuronal cell type Neuro-2a is a good model to study development and molecules modulating this process, and retinoic acid (RA) and neurotrophins (NGF, BDNF, NT-3 and NT-4) have been shown to be active in this modulation. The purpose of the present study was the functional analysis of these trophic molecules in our short-term bioassay of Neuro-2a cells, an immortalised murine neuroblastoma cell line. Through cell counting, image process and arithmetic combination of digital parameters of treated and untreated cultures, we show that RA inhibits growth and induces morphological neuronal phenotype of treated cells. Through DNA labelling with BrdU we also show that NGF, BDNF, and NT-3 increase survival and proliferation of cells, grown in serum-deprived media. From these results we conclude that neurotrophins have manifest trophic effects on cells improving survival, growth and proliferation and we also confirm the growth arrest and differentiation properties of RA on Neuro-2a cells.     

Lipid changes in the aged brain: effect on synaptic function and neuronal survival

As the brain ages, cognitive and motor performance decline. This decline is thought to be largely due to the accumulation of damaging products from normal oxidative metabolism and to the perturbation of general body homeostasis and brain-circulation separation. Despite this abundance of insults, the aged brain contains few dead neurons, suggesting that aging must be paralleled by triggering or enhancing neuronal survival mechanisms. Recent evidence points to the contribution of changes in the lipid composition of membranes to both age-dependent cognitive decline and robust neuronal survival. In this review, we describe and discuss the current understanding of the roles of lipids in neuronal aging, with special attention to their influence on membrane fusion, neurotransmitter receptor dynamics and survival/death signaling pathways.