Stem cell technology Flashcards
What are stem cells
Cells that have the capacity to develop into a variety of cell and tissue types in response to specific environments.
Hallmarks of stem cells
Self-renewal
Potency
Two types of stem cells gotten from embryos
Embryonic stem cells [ES cells])
Primordial germ cells (embryonic germ cells)
Embryonic stem cells
Found in the inner cell mass of blastocyst. Can give rise to any tissue type in the body depending on its microenvironment
Primordial germ cells
Stem cells that are only capable of giving rise to the male and female gametes (germline stem cells)
Sources of adult stem cells
bone marrow, skeletal muscle, brain tissue, skin and fat.
Molecular mechanism of stem cell differentiation
The stem cell gene codes for an mRNA which creates a transcription factor which is capable of turning on multiple genes, depending on the cell’s microenvironment
What are the 3 main types of stem cells
embryonic stem cells
adult stem cells
induced pluripotent stem cells
Embryonic stem cells
Pluripotent cells of the inner mass of the blastocyst of an embryo. These cells supply new cells for an embryo, as it grows and develops into a baby.
Pluripotency
The ability to change into any cell in the body
Adult stem cells
Adult stem cells supply new cells as an organism grows and to replace cells that get damaged.
They are said to be multipotent. e.g Haematopoietic stem cells can only replacr the various types of cells in the blood
Multipotency
The ability to be able to change into just some cells of the body’s tissues
Induced pluripotent stem cells
Has properties similar to embryonic stem cells. They are engineered by manipulating the expression of certain genes, thereby ‘reprogramming‘ somatic cells back to a pluripotent state using protein transcription factors, Oct4, Sox2, Klf4 and c-Myc.
One function of the four transcription factors used in generating iPSCs
Oct4, and Sox2 are pluripotency master genes.
c-Myc, gene is known to increase proliferation rate.
Klf4 leads to increase in p21 levels resulting in proliferation suppression, on one hand and then reduces the cellular levels of p53, which has appositive effect on the reduction of the apoptosis risk.
Method of creating iPSCs
adult cells are grown in cell culture.
specific combinations of regulatory genes are inserted into retroviruses (viruses that convert RNA [ribonucleic acid] into DNA), which are then introduced to the culture medium.
The retroviruses transport the RNA of the regulatory genes into the nuclei of the adult cells, where the genes are then incorporated into the DNA of the cells.
7 Applications of stem cells
In psychiatric medicine for diagnosis
Drug testing: testing on specialized cells from stem cells, reducing animal testing.
In regenerative medicine: generating new cells that can then be transplanted int o the body to replace those that are damaged or lost. e.g developing new skin for burn victims
In Age related disease e.g in age related macular degeneration. Scientists are producing new retinal pigment epithelia cells to replace damaged cells
Organ transplant
Cell therapy: The concept of cell-based therapy (or simply cell therapy) is to repair, replace or supplement damaged or diseased cells with healthy cells. Stem Cell therapy is effective treatment for diabetes mellitus because scientists have already proved that mesenchymal stem cells can be differentiates into pancreatic beta-islet cells after in-vitro culturing.
Disease modelling: dieased stem cells /Stem cells that are engineered to carry disease genes are used to study diseases in detail
4 main ethical issues in stem cell research
Germ-line manipulation would result in the genetic modification of the offspring which would have a permanent impact on the human species.
Moral status of using human embryos for stem cell experiments and usecases
Religious views: most religions such as Catholism, Christianity, amongst others opposes the use of embroyonic stem cell in that they promotes acts such as abortions, however, it supports use of adult stem cell as it does not require the destruction of embryos.
Humans are playing god, this concern is particularly relevant when discussing the cloning of human embryos for research purposes.
What constitutes the micro environments of stem cells?
The stem cell microenvironment refers to all the environmental factors surrounding stem cells in tissues as they proliferate, self-renew, and differentiate into tissue cells at their residency sites.
These include:
Soluble biomolecules, solid ECM with supporting cells, and the mechanical and physicochemical environment surrounding the stem cells
The ECM is a complex network of proteins and carbohydrates that provides structural support to cells and regulates their behavior 1. It also plays a critical role in stem cell differentiation and proliferation by providing mechanical cues and biochemical signals that influence cell fate
The microenvironment of stem cells is also influenced by the presence of other cells, such as fibroblasts, macrophages, and immune cells, which secrete cytokines and growth factors that regulate stem cell behavior
In addition, hormones and other signaling molecules in the blood vessel can enter the microenvironment and affect stem cells
Where can stem cells be found in the human body?
In a variety of tissues, including:
brain, blood vessels, bone marrow, fat, skeletal muscle
Explain asymmetric cell division of stem cells
Asymmetric cell division is a process in which a stem cell divides into two daughter cells with different cellular fates. One copy of the original stem cell is retained, while the other daughter cell is programmed to differentiate into a non-stem cell fate. This process is in contrast to symmetric cell divisions, which give rise to daughter cells of equivalent fates. Asymmetric cell division is a critical process in stem cell biology, as it allows for the generation of diverse cell types from a single stem cell population 4.
Differentiate between asymmetric and symmetric cell division
Symmetric cell division is a process in which a stem cell divides into two daughter cells with equivalent fates. This process is in contrast to asymmetric cell divisions, which give rise to daughter cells of different fates. Symmetric cell division is important for the expansion of stem cell populations
Give 4 genes responsible for stem cell production, proliferation and growth.
OCT4
SOX2
c-Myc
NANOG
Preliminary stem cell studies using algae, Drosophila etc as models.
Stem cell research has been conducted using a variety of model organisms, including algae, Drosophila, and mice, to better understand the mechanisms of stem cell differentiation and proliferation ¹²³.
For example, Drosophila neuroblasts, the stem cells of the developing fly brain, have emerged as a key model system for neural stem cell biology and have provided key insights into the mechanisms underlying asymmetric cell division and tumor formation. They have also been used to understand how neural progenitors can generate different neuronal subtypes over time,
Algae have also been used as a model organism for stem cell research. The red alga C. merolae, for instance, has been used to study organelle division, organelle inheritance, and the mechanisms that co-ordinate organelle and nuclear DNA replication
In addition, mice have been used extensively as a model organism for stem cell research. For example, embryonic stem cells (ESCs) derived from mice have been used to study the molecular mechanisms of pluripotency and differentiation
