By: N. Shreya Mohan (MSIWM042)
Stem cells are a group of undifferentiated cells that will differentiate into various types cells and proliferate indefinitely. They originate from cell lineages. They exact opposite to the progenitor cells, which does not proliferate indefinitely. In mammal, typically about 50-150 cells combine to form the inner cell mass (ICM) during the blastocyst stage of the embryonic development. These cells are stem cells too, having the ability to differentiate into various cell of the body. But this process is characterized by differentiating into there germ layers (layers that differentiate and give rise to tissues, organs). The three germ layers are ectoderm, endoderm and mesoderm particularly clear in gastrulation stage. These can systematically be isolated and cultured invitro during the stem cell stage and they are known as embryonic stem cells (ESCs). Parallelly, adult stem cells are found in particular areas such as the bone marrow or gonads. Their purpose, unlike the ESCs is to replenish the lost cells of the body, most common stem cells are the hemopoietic stem cells, which replenish blood and immune cells. Mesenchymal stem cells maintain bone cartilage and fat cells. The term “stem cell” was given by Theodor Boveri and Valentin Hacker during the 19th century. The properties of the stem cell were given by Ernst McCulloh and James Till. We will ponder over the properties too-
- Self-renewal- The ability of the cell to undergo numerous cycles of division and cell growth is known as cell proliferation. This should be done while the undifferentiated state.
- Potency- The capability and power of the cell to differentiate into specialized cell types. Whether it be totipotent, pluripotent, multipotent or unipotent.
Potency refers to the potentiality to be able to differentiate into respective cell types. We will dive into a brief cognizance of each of the potent type:
- Totipotent- Also known as omnipotent, these stem cells into embryonic as well as cells which are not embryonic. These cells have the ability to make a complete, functional organism. Cells include the product between the fusion of sperm and egg and the cells made after the first few divisions.
- Pluripotent- They are the known “ancestors” of totipotent cells. They can differentiate into almost all cells, specifically, the cells derived from the three germ layers.
- Multipotent- These cells will differentiate those type of cells that are closely related to each other.
- Oligopotent- These cells will only differentiate into particular cells, such as the myeloid stem cells or the lymphoid cells.
- Unipotent- These cells do not differentiate into any cell, but they do have the property of self-renewal (unlike the progenitor cells).
Stem cell therapy- a boon or a bane?
A filed with high scope, stem cell therapy is being used to treat diseases. Bone marrow replacement is one of a stem cell research which has proven effective in clinical trials. One good advantage of getting treated under this is that they lower symptoms of the disease to some extent. This leads to reduced intake of drugs required to supress the disease. One con is that the patients may require immunosuppression because the patient undergoes radiation before the transplant to remove the existing cells. This can prove detrimental chronically. For ESCs, ethics come into play as few argue that killing a new lifeform is considered unethical.
Therefore, we should look into several parameters and be aware for it run without hurdles because stem cells have a lot of scope in the future.