Monday, 23 April 2012

Discovery of Ovarian Stem Cells


 By Shona Trang - 42923257

Figure 1: Microscopic View of Stem Cells (Hamzelou, J 2012)
Flash forward to the beginning of a new era and the world as we know it has undergone drastic changes: scientists and doctors alike are now armed with the power and knowledge to create, regenerate and regrow organs and tissues and thus essentially, have the ability to proficiently annul the damage of crippling diseases. And who do our future generations have to thank? The discovery of stem cells.
                                  
Stem cells are the basic fundamentals of life and have the potential to differentiate into a variety of specialised cells such as blood cells (MediLexicon International Ltd 2012). Due to this unique characteristic, many researchers induce stem cells to grow under specific conditions to assist in curing diseases. For example, stem cells can be cultivated with certain proteins, allowing them to develop into neurons and brain tissue to assist in the regeneration of brain cells in Alzheimer’s (MediLexicon International Ltd 2012). Primarily, stem cells are found in the blastocyst (an approximately 5 day old embryo), also known as embryonic stem cells, and are also present within the human body, called adult stem cells (U.S. Department of Health and Human Services 2009). 

However, with the most recent scientific breakthrough in genetics, stem cells can now be found in human ovaries, suggesting that women may not be born with a finite supply of eggs (Hamzelou, J 2012). Dr Jonathan Tilly discovered this phenomenon by initially observing the total number of cells that develop into fertile eggs (oocytes) in mice (Telfer, E.E. & Albertini, D.F. 2012). Conventionally, the number of oocytes was predicted to decline as they progressively die off with age (hence, why women were thought to have a finite supply of eggs). Instead, within the time it would take for oocyte numbers to theoretically drop by 500, Tilly found 1500 cells dying (Hamzelou, J 2012). Thus, it can be inferred that ovarian cells have the ability to create new oocyte cells.

In order to reinforce this discovery, Tilly began to focus on pinpointing a specific protein expressed only in oocytes, which enabled him to perform a closer analysis of the egg cell. He found that during the early stages of development, a protein (Ddx4) exists only on the outer membrane of a cell before it is transported inside the cell for the later stages of growth (Powell, K 2012). In order to effectively distinguish the cell amongst thousands of others, a method called fluorescence-activated cell sorting (FACs) was used (Powell, K 2012). The Ddx4 protein was extracted and isolated from the cell, where it was ‘tagged’ by a fluorescent antibody, allowing it to glow green. The protein was then placed into a grafted human ovarian tissue where a FACs instrument  (figure 2) “lines up cells in single file and sorts them one by one, separating the labelled [cells] from the rest” whilst also removing damaged or dead cells in the process (Powell, K 2012). It was shown that the fluorescently marked cells had produced multiple immature eggs, thus allowing Tilly to concur that stem cells do indeed exist in the ovaries (Hamzelou, J 2012). 

Figure 2: Fluorescence-activated Cell Sorting (Powell, K 2012)
In effect, the recent findings of ovarian stem cells can diminish infertility rates and also shed new light on in-vitro fertilisation (IVF), a process where an egg and sperm are cultivated in a petri dish to form an embryo.  In comparison to the repetitive rounds of egg extraction, IVF only provides approximately 7 eggs per round whereas Tilly hopes that ovarian stem cells could provide “all the eggs a person could ever need from just one small piece of ovary” (Hamzelou, J 2012).  

With their remarkable ability to develop into new eggs, it is apparent that the discovery of ovarian stem cells will inevitably pave the way to limitless possibilities in the world of genetics in regards to preventing infertility amongst women of all ages for future generations to come.

Bibliography
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Hamzelou, J 2012, ‘Ovarian Stem Cells Discovered in Humans’, New Scientist, no. 2854, viewed 18 March 20120, <http://www.newscientist.com/article/mg21328544.600-ovarian-stem-cells-discovered-in-humans.html>.

MediLexicon International Ltd 2012, What are Stem Cells?, viewed 18 March 2012, <http://www.medicalnewstoday.com/info/stem_cell/>.

OvaScience 2012, Nature Medicine Demonstrates Eggs Can Mature from a Woman’s Own Egg Precursor, viewed 18 March 2012, <http://ovascience.com/publications/article.aspx?id=17>.

Pickrell, J 2006, Introduction: Stem Cells, New Scientist, viewed 19 March 2012, <http://www.newscientist.com/article/dn9982-instant-expert-stem-cells.html>.

Powell, K 2012, ‘Egg-making Stem Cells Found in Adult Ovaries’, Nature Medicine, vol. 483, no. 7387, viewed 18 March 2012, <http://www.nature.com/news/egg-making-stem-cells-found-in-adult-ovaries-1.10121>.

Telfer, E.E & Albertini, D.F 2012, ‘The Quest for Human Ovarian Stem Cells’, Nature Medicine, issue 18, viewed 18 March 2012, <http://www.nature.com/nm/journal/v18/n3/full/nm.2699.html>.

Tilly, J 2012, The Vincent Center for Reproductive Biology, Massachusetts General Hospital, viewed 18 March 2012, <http://www.massgeneral.org/vcrb/staff/Tilly.aspx>.

U.S. Department of Health and Human Services 2009, Stem Cell Information, viewed 18 March 2012, <http://stemcells.nih.gov/info/basics/basics1.asp>.
 

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