Neural stem/progenitor cells damaged by reactive oxygen species evolved in photosensitizing reaction

Upregulation of Intracellular Zinc Ion Level after Differentiation of the Neural Stem/Progenitor Cells In Vitro with the Changes in Gene Expression of Zinc Transporters

We measured the intracellular zinc ion concentration of murine fetal neural stem/progenitor cells (NSPCs) and that in the differentiated cells. The NSPCs cultured with 1.5 μM Zn2+ proliferated slightly faster than that in the zinc-deficient medium and the intracellular zinc concentration of the NSPCs and that of their differentiated cells (DCs) cultured with 1.5 μM Zn2+ was 1.34-fold and 2.00-fold higher than those in the zinc-deficient medium, respectively. The zinc transporter genes upregulated over the 3.5-fold change were Zip1, Zip4, Zip12, Zip13, ZnT1, ZnT8, and ZnT10 whereas the only downregulated one was Zip8 during the differentiation of NSPCs to DCs. The cell morphologies of both NSPCs and DCs in the low oxygen culture condition consisting of 2%O2 and 5%CO2, the high carbon dioxide condition consisting of 21%O2 and 10%CO2, and the normal condition consisting of 21%O2 and 5%CO2 were essentially the same each other. The expression of Zip4, Zip8, Zip12, and Zip14 was not drastically changed depending on the O2 and CO2 concentrations.

Alteration of Mesenchymal Stem Cells Isolated from Glioblastoma Multiforme under the Influence of Photodynamic Treatment

The central hypothesis for the development of glioblastoma multiforme (GBM) postulates that the tumor begins its development by transforming neural stem cells into cancer stem cells (CSC). Recently, it has become clear that another kind of stem cell, the mesenchymal stem cell (MSC), plays a role in the tumor stroma. Mesenchymal stem cells, along with their typical markers, can express neural markers and are capable of neural transdifferentiation. From this perspective, it is hypothesized that MSCs can give rise to CSC. In addition, MSCs suppress the immune cells through direct contact and secretory factors. Photodynamic therapy aims to selectively accumulate a photosensitizer in neoplastic cells, forming reactive oxygen species (ROS) upon irradiation, initiating death pathways. In our experiments, MSCs from 15 glioblastomas (GB-MSC) were isolated and cultured. The cells were treated with 5-ALA and irradiated. Flow cytometry and ELISA were used to detect the marker expression and soluble-factor secretion. The MSCs' neural markers, Nestin, Sox2, and glial fibrillary acid protein (GFAP), were down-regulated, but the expression levels of the mesenchymal markers CD73, CD90, and CD105 were retained. The GB-MSCs also reduced their expression of PD-L1 and increased their secretion of PGE2. Our results give us grounds to speculate that the photodynamic impact on GB-MSCs reduces their capacity for neural transdifferentiation.

Nylon mesh-based 3D scaffolds for the adherent culture of neural stem/progenitor cells

We developed novel scaffolds for the adherent culture of neural stem/progenitor cells on the woven mesh. Nylon mesh (NM) is an inert material for cell adhesion. We prepared polyacrylic acid-grafted nylon mesh (PAA-NM) by graft polymerization method using gamma-irradiation. Matrigel was covalently immobilized to the carboxyl groups in PAA-NM by chemical conjugation using 1-ethyl-3-(3-dimethylamino propyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to prepare the Matrigel-immobilized PAA-grafted nylon mesh (M-PAA-NM). Cell adhesion property of mouse neural stem/progenitor cells (NSPCs) between the NM, PAA-NM, and M-PAA-NM was different from each other. The neurosphere-like clusters of NSPCs were weakly bound to NM and PAA-NM without spreading. The NSPCs were firmly adhered to, spread, and covered the surface of M-PAA-NM. We evaluated the state of differentiation by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immnocytochemistry. A neuronal marker β III tubulin, a glial marker glial fibrillary acidic protein (GFAP) and a mature glial marker S100β were expressed at a low level in the cultured cells while immature NSPCs marker Nestin and Sox2 were slightly lower without significant statistical difference. We concluded that the M-PAA-NM is a good substrate for adherent culture of NSPCs without triggering their cell differentiation, and also provides the maintenance of their growth with fewer passages in comparison with the conventional suspension culture of NSPCs in neurospheres.

Reduced zinc cytotoxicity following differentiation of neural stem/progenitor cells into neurons and glial cells is associated with upregulation of metallothioneins

We investigated zinc cytotoxicity in mouse neural stem/progenitor cells (NSPCs) and their differentiated progeny (neuronal/glial cells) in correlation with expression of metallothionein (MT) gene. Differentiated cells were less sensitive than NSPCs to ZnCl2 (IC50: 128μM vs. 76μM). Differentiation of immature NSPCs to the differentiated cells led to an increase in expression of MT family genes (Mt1, Mt2, Mt3, and Mt4). Zinc exposure induced a dose-dependent increase in expression level of Mt1 and that of Mt2 in both NSPCs and the differentiated cells. Our results showed that the reduced cytotoxicity of zinc associated with differentiation from NSPCs into their progeny was related to the upregulation of MTs.

Neurotrophic effects of leukemia inhibitory factor on neural cells derived from human embryonic stem cells

Various growth factor cocktails have been used to proliferate and then differentiate human neural progenitor (NP) cells derived from embryonic stem cells (ESC) for in vitro and in vivo studies. However, the cytokine leukemia inhibitory factor (LIF) has been largely overlooked. Here, we demonstrate that LIF significantly enhanced in vitro survival and promoted differentiation of human ESC-derived NP cells. In NP cells, as well as NP-derived neurons, LIF reduced caspase-mediated apoptosis and reduced both spontaneous and H2O2-induced reactive oxygen species in culture. In vitro, NP cell proliferation and the yield of differentiated neurons were significantly higher in the presence of LIF. In NP cells, LIF enhanced cMyc phosphorylation, commonly associated with self-renewal/proliferation. Also, in differentiating NP cells LIF activated the phosphoinositide 3-kinase and signal transducer and activator of transcription 3 pathways, associated with cell survival and reduced apoptosis. When differentiated in LIF+ media, neurite outgrowth and ERK1/2 phosphorylation were potentiated together with increased expression of gp130, a component of the LIF receptor complex. NP cells, pretreated in vitro with LIF, were effective in reducing infarct volume in a model of focal ischemic stroke but LIF did not lead to significantly improved initial NP cell survival over nontreated NP cells. Our results show that LIF signaling significantly promotes human NP cell proliferation, survival, and differentiation in vitro. Activated LIF signaling should be considered in cell culture expansion systems for future human NP cell-based therapeutic transplant studies.

Cell-type selective phototoxicity achieved with chlorophyll-a derived photosensitizers in a co-culture system of primary human tumor and normal lung cells

The ATP-dependent transporter ABCG2 exports certain photosensitizers (PS) from cells, implying that the enhanced expression of ABCG2 by cancer cells may confer resistance to photodynamic therapy (PDT) mediated by those PS. In 35 patient-derived primary cultures of lung epithelial and stromal cells, PS with different subcellular localization and affinity for ABCG2 displayed cell-type specific retention both independent and dependent on ABCG2. In the majority of cases, the ABCG2 substrate 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) was lost from fibroblastic cells more rapidly than from their epithelial counterparts, even in the absence of detectable ABCG2 expression, facilitating selective eradication by PDT of epithelial over fibroblastic cells in tumor/stroma co-cultures. Pairwise comparison of normal and transformed epithelial cells also identified tumor cells with elevated or reduced retention of HPPH, depending on ABCG2. Enhanced ABCG2 expression led to the selective PDT survival of tumor cells in tumor/stroma co-cultures. This survival pattern was reversible through HPPH derivatives that are not ABCG2 substrates or the ABCG2 inhibitor imatinib mesylate. PS retention, not differences in subcellular distribution or cell signaling responses, was determining cell type selective death by PDT. These data suggest that up-front knowledge of tumor characteristics, specifically ABCG2 status, could be helpful in individualized PDT treatment design.