Difference Between IPS Cells and Embryonic Stem Cells

Key Difference – IPS Cells vs Embryonic Stem Cells
 

There are several types of stem cells which can be used for tissue regeneration in tissue engineering and wound healing. Among them, embryonic stem cells serve as a major and the most suitable stem cell types since they are naturally pluripotent. Pluripotency is the ability of a cell to differentiate into many or all cell types in an adult body. Human embryonic stem cells are able to differentiate into more than 200 specialized cell types found in human. They are isolated from inner cell mass of in vitro fertilized embryo which is a few days old and is used for tissue engineering and disease therapeutics. However, due to ethical issues related to embryonic stem cells, scientists attempt to create artificial pluripotent stem cells in vitro by inducing the gene expression of adult somatic cells. They are known as induced pluripotent stem cells (IPS cells). The key difference between IPS cells and embryonic stem cells is that induced pluripotent stem cells are adult somatic cells which are generated and genetically reprogrammed to functions as embryonic stem cells and become pluripotent while embryonic stem cells are naturally pluripotent.

CONTENTS
1. Overview and Key Difference
2. What are IPS Cells
3. What are Embryonic Stem Cells
4. Side by Side Comparison – IPS Cells vs Embryonic Stem Cells
5. Summary

What are IPS Cells?

Induced pluripotent stem cells (IPS cells) are the cells that are developed by scientists to mimic natural pluripotent stem cells called embryonic stem cells. These cells are constructed under in vitro conditions in the labs. Gene expression of the adult cell is reprogrammed to induce differentiation in induced pluripotent stem cells. Hence, IPS cells show the same properties as embryonic stem cells such as self-renewal, differentiation, etc. But IPS cells are not identical to ES cells according to the literature and medical experts.

IPS cells were first constructed at Kyoto University, Japan by Shinya Yamanaka and team in 2006. They used mouse fibroblasts to generate IPS cells and the genes are delivered using retroviruses as vectors. Secondly, IPS cells were developed in 2007 using human cells. Many scientists generate IPS cells which are nearly identical to ES cells. However, further researches are needed to use these IPS cells safely and effectively for cell therapy.

During the reprogramming process of fibroblast to develop IPS cells, the induction of ES cell genes and suppression of fibroblast genes should be carefully and correctly done. Otherwise, the resultant cells will not work as ES cells.

ES cells have ethical considerations. It can be avoided by IPS cells. IPS cells are easy to use compared to ES cells. However, development of IPS has a lot of challenges such as low efficiency, genomic insertion, incomplete reprogramming, etc. There is a chance of introducing mutations as a part of creation. DNA methylation is an important event in cells to on and off genes and regulates gene expression. It is important for the construction of IPS cells as well during the genetic reprogramming. Hence, it is necessary to look at the methylation patterns of ES cells and develop same patterns in IPS cells to create perfectly identical IPS cells with ES cells. Only IPS cells can confidently and safely replace ES cells for research and therapy.

These cells are not yet applied in human disease therapeutics. They are still used in animal testing. However, one major goal of constructing IPS cells is to use them for Parkinson’s patients and later for tissue formation and many complex disease therapies.

What are Embryonic Stem Cells?

Embryonic stem cells (ES cells) are the undifferentiated cells found in inner cell mass of the developing embryo. They have the inherent ability of self-renewal and differentiation into all cell types of an adult person. Hence, they are known as pluripotent stem cells as well. Rapid cell division potential makes them suitable for use in tissue regeneration and wound healing. Embryonic stem cells grow primarily into three primary germ layers such as ectoderm, endoderm, and mesoderm which are later differentiated into different human body cell types. Therefore, ES cells serve as a valuable tool in regenerative medicine.

ES cells are isolated from the in vitro fertilized egg cell which is developed into several days old embryo. It is important to know that this term ‘embryonic stem cells’ are not used to refer to stem cells derived from the embryo developed in a woman’s body. Stem cells taken from a several days old embryo are maintained in laboratories as embryonic stem cell lines. If proper conditions are provided, it is possible to maintain undifferentiated stem cells in the labs.

Embryonic stem cells are the progenitors of all cell types of the body including muscle, nerve, liver and many other cells. If scientists are able to direct the cell differentiation of in vitro maintained ES cells correctly, they can use the cells to treat certain diseases such as diabetes, traumatic spinal cord injury, Duchenne’s muscular dystrophy, heart disease, and vision and hearing loss etc.

What is the difference between IPS Cells and Embryonic Stem Cells?

Summary – IPS Cells vs Embryonic Stem Cells

IPS cells mimic ES cells. But they are not perfectly identical to ES cells. Both cell types show pluripotency. Both cell types have a great potential to use in tissue engineering and disease therapeutics. However, the use of these cells in human disease therapy is still not practiced due to ethical and safe issues. IPS are generated by genetically reprogramming adult cells. They are not isolated from the embryo. ES cells are isolated from in vitro fertilized egg cell which is several days old. This is the difference between IPS cells and embryonic stem cells.

Reference:
1.Chin et al. “Induced Pluripotent Stem Cells and Embryonic Stem Cells Are Distinguished by Gene Expression Signatures.” Cell stem cell. U.S. National Library of Medicine, 02 July 2009. Web. 07 May 2017.
2.Fikes, Bradley J. “Study: Embryonic, artificial stem cells equal.” Sandiegouniontribune.com. N.p., 23 Aug. 2016. Web. 08 May 2017. <http://www.sandiegouniontribune.com/business/biotech/sdut-embryonic-induced-pluripotent-equal-2015oct26-story.html>.
3.Huang, Audrey. “Induced Pluripotent Stem Cells: Not Yet the Perfect Alternative.” Johns Hopkins Medicine, based in Baltimore, Maryland. N.p., 15 Feb. 2013. Web. 08 May 2017. <http://www.hopkinsmedicine.org/institute_basic_biomedical_sciences/news_events/articles_and_stories/stem_cells/2010_07_pluripotent_stem_cells>.
4.Goldthwaite, Charles A. “The Promise of Induced Pluripotent Stem Cells (iPSCs).” National Institutes of Health. U.S. Department of Health and Human Services, n.d. Web. 08 May 2017. <https://stemcells.nih.gov/info/Regenerative_Medicine/2006Chapter10.htm>

Image Courtesy:
1.”IPS process” By GcG (wpja user) (CC BY-SA 3.0) via Commons Wikimedia
2. “Human embryonic stem cells only A”  (CC BY 2.5) via Commons Wikimedia