In general, the process of cell differentiation is irreversible. However, under certain conditions, the differentiated cells are also unstable, and their gene expression patterns can also undergo reversible changes and return to their undifferentiated state.
This process is called dedifferentiation. Features of cell differentiation include: The potential of differentiation gradually appears with the development of the individual.
During embryonic development, the cells gradually change from "all-around" to "multi-energy", and finally to the "single-energy", which is the general rule of cell differentiation. In the process of individual development, multicellular biological cells have both temporal differentiation and spatial differentiation; cell differentiation is compatible with the state and speed of cell division, and differentiation must be based on division, that is, differentiation is inevitable with division, but the dividing cells do not necessarily need differentiate.
The higher the degree of differentiation, the worse the ability to divide; the cell differentiation is highly stable. Under normal physiological conditions, cells that have differentiated into a specific, stable type are generally impossible to reverse to undifferentiated state or become other types. Cell differentiation is plastic, and the differentiated cells re-enter the undifferentiated state or transdifferentiate into another type of cell under special conditions.
Embryonic stem cells ES cells have the potential to develop into different types of cells. Under suitable conditions in vitro , they can proliferate in an undifferentiated state, providing a source of cells for the research and application of ES cells.
The mouse embryonic stem cells treated with retinoic acid will differentiate into neural progenitor cells and then treat with Shh specific small molecule antagonist Hh-Ag 1. Takahashi et al found that ascorbic acid can effectively enhance the differentiation of embryonic stem cells into cardiomyocytes.
Wu et al. Hironori et al. Of course, due to the existence of immunocompatibility issues, the safety of embryonic stem cell transplantation needs to be a comprehensive, objective and in-depth evaluation.
Bone marrow stromal cells MSCs are derived from mesoderm and can differentiate into mesoderm cells such as osteoblasts, chondrocytes, myoblasts, tendon cells, adipocytes, and stromal cells under certain induction conditions; it can differentiate into neuroblast cells of the ectoderm and hepatic oval cells of the endoderm.
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How Do We See? How Do We Sense Smell? How Do We Sense Taste? How Do We Sense Touch? What is Evolutionary Medicine? What's a Biologist? What's a GMO? What's a Genome? Adult bone marrow has three distinct types of stem cells: hematopoietic stem cells which give rise to red blood cells, white blood cells, and platelets , endothelial stem cells which give rise to the endothelial cell types that line blood and lymph vessels , and mesenchymal stem cells which give rise to the different types of muscle cells.
The process of hematopoiesis involves the differentiation of multipotent cells into blood and immune cells. The multipotent hematopoietic stem cells give rise to many different cell types, including the cells of the immune system and red blood cells.
When a cell differentiates becomes more specialized , it may undertake major changes in its size, shape, metabolic activity, and overall function. Since all cells in the body, beginning with the fertilized egg, contain the same DNA, how do the different cell types come to be so different? The answer is analogous to a movie script. The different actors in a movie all read from the same script, however, they are each only reading their own part of the script.
In biology, this is referred to as the unique genetic expression of each cell. In order for a cell to differentiate into its specialized form and function, it need only manipulate those genes and thus those proteins that will be expressed, and not those that will remain silent.
Transcription factors are proteins that affect the binding of RNA polymerase to a particular gene on the DNA molecule. Stem cell research aims to find ways to use stem cells to regenerate and repair cellular damage. Over time, most adult cells undergo the wear and tear of aging and lose their ability to divide and repair themselves. Stem cells do not display a particular morphology or function.
Adult stem cells, which exist as a small subset of cells in most tissues, keep dividing and can differentiate into a number of specialized cells generally formed by that tissue. These cells enable the body to renew and repair body tissues. The mechanisms that induce a non-differentiated cell to become a specialized cell are poorly understood.
For example, the process of apoptosis, or programmed cell death, selectively removes damaged cells — including those with DNA damage or defective mitochondria. During apoptosis, cellular proteases and nucleases are activated, and cells self-destruct. Cells also monitor the survival factors and negative signals they receive from other cells before initiating programmed cell death. Once apoptosis begins, it proceeds quickly, leaving behind small fragments with recognizable bits of the nuclear material.
Specialized cells then rapidly ingest and degrade these fragments, making evidence of apoptosis difficult to detect. Figure 2 : Different cell types in the mammalian gut The gut contains a mixture of differentiated cells and stem cells. The a intestine, b esophagus, and c stomach are shown.
Through asymmetric division, quiescent stem cells d probably give rise to more rapidly dividing active stem cells, which then produce progenitor cells while losing their multipotency and ability to proliferate. All these progeny cells have defined positions in the different organs. To maintain its function and continue to produce new stem cells, a stem cell can also divide into and produce more stem cells at the same position symmetric division. Stem cells in gastroenterology and hepatology.
All rights reserved. Figure Detail Tissue function depends on more than cell type and proper rates of death and division: It is also a function of cellular arrangement. Both cell junctions and cytoskeletal networks help stabilize tissue architecture. For instance, the cells that make up human epithelial tissue attach to one another through several types of adhesive junctions. Characteristic transmembrane proteins provide the basis for each of the different types of junctions.
At these junctions, transmembrane proteins on one cell interact with similar transmembrane proteins on adjacent cells. Special adaptor proteins then connect the resulting assembly to the cytoskeleton of each cell. The many connections formed between junctions and cytoskeletal proteins effectively produces a network that extends over many cells, providing mechanical strength to the epithelium.
The gut endothelium — actually an epithelium that lines the inner surface of the digestive tract — is an excellent example of these structures at work. Here, tight junctions between cells form a seal that prevents even small molecules and ions from moving across the endothelium.
As a result, the endothelial cells themselves are responsible for determining which molecules pass from the gut lumen into the surrounding tissues.
Meanwhile, adherens junctions based on transmembrane cadherin proteins provide mechanical support to the endothelium. These junctions are reinforced by attachment to an extensive array of actin filaments that underlie the apical — or lumen-facing — membrane. These organized collections of actin filaments also extend into the microvilli , which are the tiny fingerlike projections that protrude from the apical membrane into the gut lumen and increase the surface area available for nutrient absorption.
Additional mechanical support comes from desmosomes , which appear as plaque-like structures under the cell membrane, attached to intermediate filaments. In fact, desmosome-intermediate filament networks extend across multiple cells, giving the endothelium sheetlike properties.
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