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Stem Cells

Stem cells are defined as undifferentiated biological cells that can further differentiate into specialized cells. There are two types of stem cells: embryonic stem cells isolated from the inner cell mass of blastocysts and adult stem cells found in various tissues. In adult organisms, stem cells and progenitor cells serve as a repair system for the body. There are a number of sources for adult stem cells in humans: bone marrow, adipose tissue and blood. In a developing embryo, stem cells can differentiate into various specialized cells derived from the ectoderm, endoderm and mesoderm (1).

Stem cells possess two main properties: self-renewal (the ability to go through numerous cycles of cell division while maintaining the undifferentiated state) and potency (the capacity to differentiate into specialized cell types) (2).

Embryonic stem cell lines are cultured from the inner cell mass of a blastocyst, an early stage embryo. Human ES cells have to be cultured on a feeder layer of mouse embryonic fibroblasts and require the presence of basic fibroblast growth factor (bFGF or FGF-2) (3). Human ES cells are also defined by the expression of several transcription factors and cell surface proteins. The transcription factors Oct-4, Nanog, and Sox2 form the main regulatory network that ensures the suppression of genes that lead to differentiation and the maintenance of pluripotency (4). The cell surface antigens most commonly used to identify hES cells are the glycolipids stage specific embryonic antigen 3 and 4 and the keratin sulfate antigens Tra-1-60 and Tra-1-81.

Bone marrow is known to be one of the sources of adult stem cells and has been used to treat several conditions such as leukemia and related bone/blood cancers (5). In addition, recent scientific advancements have shown that adult stem cells can be reprogrammed to give rise to pluripotent capabilities using protein transcription factors. Scientists applied a set of transcription factors Oct3/4, Sox2, c-Myc, Nanog, Lin28 and Klf4 in their experiments on human adult cells (6,7).

Pluripotency and self-renewal are regulated by a number of cell signaling pathways such as TGF-β, which signals through Smad2/3/4 and FGFR, activating MAPK and Akt pathways. The Wnt pathway promotes pluripotency through a non-canonical mechanism involving the transcriptional activator TCF1 and the repressor TCF3. Signaling through these pathways results in the activation of three key transcription factors: Oct-4, Sox2, and Nanog.

Abcepta offers high-quality, in-house developed antibodies for the elucidation of signaling pathways in stem cell research. In addition, Abcepta developed antibodies for the study of mechanisms important for stem cell therapy in human diseases including cancer, neurodegenerative disorders and other pathologies.