What are Stem cells?

By | July 20, 2021
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Our body is made of trillions of cells and there are different cell types performing their unique function. Among the different cell types, stem cells are unique in their remarkable ability to renew themselves. Another aspect which makes them special and really useful in therapeutics is that they can develop into any other cell type.

Stem cell giving rise to more stem cells or specialized cells

Types of Stem cells :

Stems cell are of three types

  1. Embryonic stem cells
  2. Adult stem cells (somatic stem cells)
  3. Induced pluripotent stem cells

Embryonic stem cells have the capacity to divide and can become any cell of the body. These kind of cells are called Pluripotent or totipotent. These cells are undifferentiated, they don’t have any tissue specific characteristics such as the the morphology or gene expression pattern, but still retains the ability to be transformed into any cell type and perform related unique functions. The entire mechanism behind differentiation of these stem cells is very complex and not completely understood. This process involves intrinsic regulation of expression pattern of various genes involved in those specific cell types.

Adult Stem cells are found in different organs of our body and can differentiate to yield the specialized cell types of those tissue or organ to replenish damaged tissue and cannot be turned into any desired cell type like embryonic stem cells eg: Blood stem cells found in bone marrow can give rise to only different types of blood cells -RBCs, WBCs . They exhibit morphological features and gene expression pattern resembling that particular tissue.

Induced pluripotent stem cells are the stem cells produced by the scientists in the laboratory. They turn the normal adult cells from blood or skin into pluripotent cells by reprogramming their gene expression. The reprogramming events might involve turning off all the signaling cascades which are important for cells differentiation into a specialized cell and provide the signals that normally tell stem cells to stay as stem cells in the early embryo. Once reprogrammed these adult cells behave like the embryonic stem cells and can be transformed into any cell type.

How to culture Stem cells in lab conditions:

Stem cells can be grown in laboratory and this process is termed as “cell Culture”. To successfully grow different stem cells require standardized conditions and apt nutrient supplements (culture media). if everything goes well, stem cells continue to grow and divide well on culture dish.

After sometime as the culture dish becomes crowed, the cells needs to be re-plated on another dish with fresh culture media for cells to divide efficiently again. This process of re-plating is called as sub-culturing, which is repeated periodically many times over a span of many months. Each cycle of sub-culturing is referred to as a “passage.” The original cells can yield millions of stem cells.

A batch of cells of interest can be frozen and stored for many days, which can later be regrown when required for further experimentation.

Uses of stem cells in research and therapies:

Given the remarkable ability of human stem cells to divide innumerable times, these cells are of great importance in biomedical research and in development of therapeutics.

Stem cells provide an excellent medium to study how different cells in our body work. A better understanding of molecular mechanism controlling the process of cell division and specialization in stem cells will allow researchers to know how cells gets transformed to a specialized cell for performing specific functions in the body. This will also provide scientists with valuable insights into molecular events that might happen when he same normal process goes wrong in disease conditions and allows them to suggest new strategies for finding suitable therapy. Scientists can use adult stem cells from the patient and transform them into induced pluripotent cells to create new cells, tissues and “organoids” (small models of organs) required for studying diseased cells and testing drugs for a possible cure.

Stem cell therapy:

The cells in our body have limited ability to divide and replenish damaged tissues. However sometimes, the tissues or organs are damaged beyond the self repair capacity of our bodies. Stem cells can be an excellent resource for generating new cells that can then be transplanted into the body to replace those that are damaged or lost. Latest research in the filed of stem cells also allow us to correct disease genes, where a mutation in a particular gene prevents its normal function in the tissues. Using Crispr-Cas technology we can repair or stich, mutation in the gene to restore its normal function and then re-transplant those corrected cells with fully functional gene, back into our system. It is important to know that there is still a long way to go for this process to be applied on a large scale basis for many genetic disorders and for the benefit of everyone in the society.

However these things are not simple as they appear and involves many hurdles during the process and everything needs to fall in place for desired result.

To improve stem cell therapies, scientists must have a complete understanding about transforming adult stems cells, so that they exhibit all the characters required for proper differentiation, transplantation, and engraftment. One of the important hurdle which scientists face is in administration of stem cell populations into the body and they should also ensure to induce vascularization (supplying blood vessels), for the regeneration of tissues. The research in the field of stem cells is therefore crucial to study basic mechanisms to know how cells work in normal development and disease conditions.

To successfully use stem cells for therapies , the following steps should be reproduced without any aberrations:

  1. Stem cells should growly continuously to generate required number of cells for transplantation of damaged tissue.
  2. Differentiate into desired specialized cell.
  3. These cells should survive and integrate efficiently ( without immune rejection) into recipient’s tissue.
  4. Transformed cells should perform required function through out the life span of recipient host.

Even though stem cells offer exciting promise for future therapies, we should be careful with our expectations as many significant technical issues remain, that can be only solved by intensive research in the field.

Image credit : Smart servier and adult Stem Cells and Induced Pluripotent Stem Cells for Stroke Treatment – https://doi.org/10.3389/fneur.2019.00908 Authors : Fernández-Susavila Héctor, Bugallo-Casal Ana, Castillo José, Campos Francisco