Neurosphere

About: Neurosphere is a research topic. Over the lifetime, 5145 publications have been published within this topic receiving 321088 citations.

A nucleolar mechanism controlling cell proliferation in stem cells and cancer cells

Abstract: The unique property of stem cells to self-renew suggests specific mechanisms that regulate their cell-cycle progression. In the present study, we identify a novel protein, nucleostemin, found in the nucleoli of CNS stem cells, embryonic stem cells, and several cancer cell lines and preferentially expressed by other stem cell-enriched populations. It contains an N-terminal basic domain and two GTP-binding motifs. When stem cells differentiate, nucleostemin expression decreases rapidly prior to cell-cycle exit both in vitro and in vivo. Depletion or overexpression of nucleostemin reduces cell proliferation in CNS stem cells and transformed cells. Mutation analysis indicates that excessive nucleostemin, particularly mutants that lack the GTP-regulatory domain, prevents cells from entering mitosis and causes apoptosis in a p53-dependent manner. The N-terminal basic domain specifies nucleolar localization, the p53 interaction, and is required for the cell death caused by overexpression. This work describes a novel nucleolar mechanism that controls the cell-cycle progression in CNS stem cells and cancer cells.

Differentiation of Human Embryonic Stem Cells into Insulin-Producing Clusters

Abstract: Type I diabetes mellitus is caused by an autoimmune destruction of the insulin-producing beta cells. The major obstacle in using transplantation for curing the disease is the limited source of insulin-producing cells. The isolation of human embryonic stem (hES) cells introduced a new prospect for obtaining a sufficient number of beta cells for transplantation. We present here a method for forming immature islet-like clusters of insulin-producing cells derived from hES cells. The protocol consisted of several steps. Embryoid bodies were first cultured and plated in insulin-transferrin-selenium-fibronectin medium, followed by medium supplemented with N2, B27, and basic fibroblast growth factor (bFGF). Next, the glucose concentration in the medium was lowered, bFGF was withdrawn, and nicotinamide was added. Dissociating the cells and growing them in suspension resulted in the formation of clusters which exhibited higher insulin secretion and had longer durability than cells grown as monolayers. Reverse transcription-polymerase chain reaction detected an enhanced expression of pancreatic genes in the differentiated cells. Immunofluorescence and in situ hybridization analyses revealed a high percentage of insulin-expressing cells in the clusters. In addition to insulin, most cells also coexpressed glucagon or somatostatin, indicating a similarity to immature pancreatic cells. Further improvement of this insulin-producing cell protocol may lead to the formation of an unlimited source of cells suitable for transplantation.

Hematopoietic competence is a rare property of neural stem cells that may depend on genetic and epigenetic alterations

Abstract: The concept of stem-cell plasticity received strong support from a recent observation that extensively passaged, clonally derived neural stem cells could contribute to hematopoiesis. We investigated whether hematopoietic potential was a consistent or unusual feature of neural stem cells, and whether it depended on the extent of in vitro passaging before transplantation. Here we transplanted over 128 × 106 neurosphere cells into 128 host animals; however, we never observed contribution to hematopoiesis, irrespective of the number of passages and despite the use of an assay that could detect the contribution of a single blood stem cell to hematopoietic repopulation. Although extensively cultured neurosphere cells continued to generate neural progeny, marked changes in their growth properties occurred, including changes in growth-factor dependence, cell-cycle kinetics, cell adhesion and gene expression. Our results exclude hematopoietic competence as a consistent property of intravenously infused neural stem cells. However, the consistent changes that occurred during extended passaging are compatible with genetic or epigenetic alterations and suggest that rare transformation events may account for the neural-to-blood fate switch originally reported.