- Table of Contents
Moments after conception, a fertilized egg (zygote) initiates embryogenesis, a highly controlled process of proliferation and directed differentiation. The developmental events that occur during embryogenesis are guided by intricate genetic and epigenetic signaling cascades and constitute the initial stages of a highly complex process that culminates in the generation of a new, fully formed multicellular organism.
Embryonic stem cells (ESCs) are a defined cell population derived from the cleavage-stage embryo's inner cell mass (blastocyst). The inherent pluripotency of ESCs, which enables them to differentiate into any cell lineage in the body, and their capacity for indefinite self-renewal are their defining characteristics. These characteristics, which are tightly controlled by a complex array of cell signaling networks, combine to make ESCs an extremely useful tool for developmental biology research, with significant potential for personalized regenerative medicine.
Biologists use stem cell markers to isolate and identify stem cells. Additionally, stem cells can be identified using functional assays, which are considered the gold standard for identifying and treating stem cells. While functional assays are the optimal method for defining stem cells, their molecular markers enable a systematic assessment of a healthy and robust stem cell population. Our understanding of stem cell identification in relation to therapeutic applications is rather limited, owing to their extraordinary complexity, specificity, and validity, as well as the absence of specific molecular markers.
A diverse array of growth factors, receptors, intracellular signaling molecules, and transcription factors influence the mechanisms governing ES/iPS self-renewal and differentiation. Cell fate determination frequently requires a precisely timed presentation of growth factors and transcription factor expression. The following factors are known to affect the pluripotency, proliferation, and lineage commitment of ES/iPS cells. The expression of a unique combination of cell surface markers and transcription factors can be used to identify ES/iPS cells and their differentiated progeny. By clicking on a particular cell type within the lineage pathway, you can view the unique identifiers for that cell.
Despite our limited understanding of marker functions, their distinct expression pattern and timing make them an effective tool for identifying and isolating stem cells. This review discusses a variety of marker systems for identifying, isolating, and characterizing adult and embryonic stem cells in relation to their critical applications.
Numerous stem cell subtypes, including embryonic, induced pluripotent, and adult stem cells, have been identified. Embryonic stem cells are pluripotent, meaning they can differentiate into any type of cell found in an adult organism. Adult (somatic) stem cells, on the other hand, such as hematopoietic, muscle, cardiac, neural, and mesenchymal stem cells, have a lower potency and their differentiated derivatives are thought to predominantly populate the tissue of residence.
MSCs are multipotent, self-renewing progenitors that can differentiate into adipocytes, chondrocytes, and osteocytes. MSCs were initially discovered in mouse bone marrow but have since been isolated from a variety of tissues including adipose, placental, dental pulp, and umbilical cord. Despite the classical trilineage differentiation that functionally defines MSCs, these cells have been shown to differentiate into non-traditional lineages such as cardiomyocytes, endothelial cells, hepatocytes, and neural cells. Until now, the biological properties of MSC identification, differentiation, and function have not been confirmed in vivo, raising concerns about extrapolating data generated in vitro. A diverse array of growth factors, receptors, intracellular signaling molecules, and transcription factors are thought to influence the mechanisms governing MSC self-renewal and differentiation.
The following factors are known to have an effect on MSC multipotency, proliferation, and lineage commitment. The expression of a unique combination of cell surface markers and transcription factors enables the identification of MSCs and their differentiated progeny. By clicking on a particular cell type within the lineage pathway, you can view the unique identifiers for that cell.
NSCs are undifferentiated precursor cells that are characterized by their capacity for self-renewal and pluripotency. NSCs proliferate and divide during central nervous system development, generating clonally related progeny that differentiate into neurons, astrocytes, oligodendrocytes, and ventricular ependymal cells. The symmetric division of NSCs underpins their capacity for self-renewal and contributes to the population's maintenance. By contrast, asymmetric mitosis generates one neural stem cell (NSC) and one neural progenitor cell (NPC), daughter cells capable of differentiation into neuronal or glial lineages. Asymmetric division results in the production of two NPCs but does not contribute to the maintenance of the NSC pool. The self-renewal and differentiation of neural stem cells are controlled by a precise temporal sequence of growth factor presentation, intracellular signaling, and transcription factor expression.
The expression of a unique combination of cell surface markers and transcription factors can be used to identify NSCs and their differentiated progeny. Navigate the pathway above to identify differentiation factors and cell-specific markers for NSCs, their terminally differentiated progeny, and transitional intermediates. By clicking on a particular cell type within the lineage pathway, you can view the unique identifiers for that cell.