Cryopreservation of Human Gametes
3
Osama Ghani Science 1 10 E Cryopreservation of Human Gametes and Its Usefulness Osama Ghani Loss of fertility is a growing problem around the world. This may be due to the natural menopause in women during the 50s, or especially due to the growing rates of cancer in both men and women. Chemotherapy and radiotherapy are some of the most effective treatments for cancer, but they can end up destroying female fertility temporarily or permanently (“Cancer and Fertility for Women”). Since cancer warning symptoms are rarely recognized, the average female does not think about her future reproductive life. In today’s world, it is a smart choice for a woman to ‘ensure’ that she will have eggs when she needs them. Similarly, chemotherapy and radiotherapy can destroy male fertility temporarily (most often) or sometimes even permanently (“Cancer and Fertility for Men”). So it follows that males should also have a system to ‘ensure’ that they will have sperm when they need it. One of the effective systems that Science provides, and is in place today is cryopreservation of human gametes. Cryopreservation is the preservation of cells and tissues by storing them at subzero temperatures or by vitrification. At these temperatures, activities that would cause cell death are inhibited. Successful cryopreservation has enhanced the conception rate for couples that have had temporary infertility problems and is an important assisted reproduction technology (AlHasani). There are two techniques practiced in cryopreservation. One is the subzero cooling method, and the other is vitrification (Ozmen). There are many benefits of cryopreservation. In this paragraph, one benefit for the male, and one in general will be discussed. A male has the capability to produce millions of sperms. Removing some semen from a male’s body is hence not a difficult process. The survival rate for sperm in the semen sample is typically 24.9 % for normozoospermics (normal sperm count) sample and is 11.9 % for oligozoospermics (low sperm count). This can be increased to 35.6% and 27.7% respectively using appropriate preparation techniques (“Cryopreservation”). Considering the fact that an average sample of semen will contain millions of sperms, a survival rate between 10%40% is sufficiently high. So cryopreservation proves to be an effective method so far as storage of male semen is concerned. The second benefit is that it allows for males and females to retain their fertility. For example, cryopreservation offers the option of conceiving using reproductive technologies in the future. It is offered as a fertility preservation technique for prepubescent and postpubescent individuals who might have problems that threaten their fertility. In such cases, their gametes may be preserved, offering them the ability to conceive even though de facto their fertility has been lost (“Cryopreservation”). Even though cryopreservation seems to be a viable solution to a number of fertility problems due to a high success rate, the fact remains that in practicality, it is much more difficult to implement for a woman’s oocytes (eggs) than a man’s sperm. A number of complications arise that could render the oocyte useless. For example, the delicate shell of the egg is easily ruptured during the process of cryopreservation, when osmotic pressure forces materials to move in and out of
-
Upload
osama-ghani -
Category
Documents
-
view
44 -
download
9
description
An essay outlining the science behind the cryopreservation of human gametes, its benefits, limitations and importance in global society.
Transcript of Cryopreservation of Human Gametes
Osama Ghani Science 1 10 E
Cryopreservation of Human Gametes and Its Usefulness -‐Osama Ghani
Loss of fertility is a growing problem around the world. This may be due to the natural menopause in women during the 50s, or especially due to the growing rates of cancer in both men and women. Chemotherapy and radiotherapy are some of the most effective treatments for cancer, but they can end up destroying female fertility temporarily or permanently (“Cancer and Fertility for Women”). Since cancer warning symptoms are rarely recognized, the average female does not think about her future reproductive life. In today’s world, it is a smart choice for a woman to ‘ensure’ that she will have eggs when she needs them. Similarly, chemotherapy and radiotherapy can destroy male fertility temporarily (most often) or sometimes even permanently (“Cancer and Fertility for Men”). So it follows that males should also have a system to ‘ensure’ that they will have sperm when they need it. One of the effective systems that Science provides, and is in place today is cryopreservation of human gametes. Cryopreservation is the preservation of cells and tissues by storing them at sub-‐zero temperatures or by vitrification. At these temperatures, activities that would cause cell death are inhibited. Successful cryopreservation has enhanced the conception rate for couples that have had temporary infertility problems and is an important assisted reproduction technology (Al-‐Hasani). There are two techniques practiced in cryopreservation. One is the sub-‐zero cooling method, and the other is vitrification (Ozmen). There are many benefits of cryopreservation. In this paragraph, one benefit for the male, and one in general will be discussed. A male has the capability to produce millions of sperms. Removing some semen from a male’s body is hence not a difficult process. The survival rate for sperm in the semen sample is typically 24.9 % for normozoospermics (normal sperm count) sample and is 11.9 % for oligozoospermics (low sperm count). This can be increased to 35.6% and 27.7% respectively using appropriate preparation techniques (“Cryopreservation”). Considering the fact that an average sample of semen will contain millions of sperms, a survival rate between 10%-‐40% is sufficiently high. So cryopreservation proves to be an effective method so far as storage of male semen is concerned. The second benefit is that it allows for males and females to retain their fertility. For example, cryopreservation offers the option of conceiving using reproductive technologies in the future. It is offered as a fertility preservation technique for prepubescent and postpubescent individuals who might have problems that threaten their fertility. In such cases, their gametes may be preserved, offering them the ability to conceive even though de facto their fertility has been lost (“Cryopreservation”). Even though cryopreservation seems to be a viable solution to a number of fertility problems due to a high success rate, the fact remains that in practicality, it is much more difficult to implement for a woman’s oocytes (eggs) than a man’s sperm. A number of complications arise that could render the oocyte useless. For example, the delicate shell of the egg is easily ruptured during the process of cryopreservation, when osmotic pressure forces materials to move in and out of
Osama Ghani Science 2 10 E
the egg. Further, oocytes are extremely vulnerable to damage by thawing, leading to damage of structures such as the zona pellicuda (the shell), the cortical granules, the meiotic spindles (which play an important role in cell division) and the cell organelles. Damage to cortical granules can be particularly problematic since they are responsible for letting only one sperm fertilize the egg. It has been observed that through the thawing process, the cortical granules sometimes harden, and hence this prevents fertilization (Fabbri). Besides the disadvantage of possible damage to the egg, there is also the second disadvantage of a low survival rate after thawing. In men, even an 11% survival rate is reasonable, because men produce millions of sperms. However, in females, the survival rate is just about 50-‐60%. This rate comes about by averaging extremely low rates (0-‐10%) with extremely high rates (90-‐100%). The fact that the chance of an egg’s survival is either extremely high, or extremely low is something for females considering oocyte cryopreservation to worry about, since females produce only one egg per menstrual cycle (lasting about a month), and the extraction of an egg is complicated itself (“The Freezing of Human Oocytes (Eggs)”). Hence, cryopreservation of gametes proves to be much more complicated and problematic in females than in males. Cryopreservation brings about a number of political and social questions to mind, with varying answers. The first one of them deals with social and political issues. The question is of the legal status of a baby produced as a result of the fertilization of a living being with his or her deceased spouse’s cryopreserved gametes. There is little legal documentation on the issue but a large number of divergent views. The immediate questions that are raised are what is the effect on the marital status of the individuals, and what the relation is of the deceased partner to the conceived child. The United States has no say in this issue, and nor does any other country confer any special legal status on those conceived in such a manner. Furthermore, it is also questionable whether the family of the deceased is responsible for the child, if the living partner conceived a child without the will of the deceased (Hans). Another issue of socio-‐cultural and political concern is a possible growing black market of cryopreserved sperm and eggs. Many of the LGBT community look to sperm and egg donors so that they can ‘conceive’ a child. However, countries such as Canada have passed legislations against paying donors, saying that it should be done out of free will and not to create a market. This has led to a significant decrease in reproductive material in Canada. (Fraser).
Bibliography
Al-‐Hasani, Safaa, and Khaled Zohni. "Future Aspects In Human Cryopreservation." Journal of
Family and Reproductive Health 2.1 (2008). Print.
Osama Ghani Science 3 10 E
"Cancer and Fertility for Men." MacMillan Cancer Support. Web. 08 Dec. 2012.
<http://www.macmillan.org.uk/Cancerinformation/Livingwithandaftercancer/Sympt
omssideeffects/Fertility/Fertilityinmen.aspx>.
"Cancer and Fertility for Women." MacMillan Cancer Support. Web. 08 Dec. 2012.
<http://www.macmillan.org.uk/Cancerinformation/Livingwithandaftercancer/Sympt
omssideeffects/Fertility/Fertilityinwomen.aspx>.
"Cryopreservation." Virtual Medical Centre. Web. 08 Dec. 2012.
<http://www.virtualmedicalcentre.com/treatment/cryopreservation/157>.
Fabbri, R., and E. Porcu. "Oocyte Cryopreservation." Human Reproduction 13.4: 98-‐
108. Oxford Journals. Web. 8 Dec. 2012.
<http://humrep.oxfordjournals.org/content/13/suppl_4/98.full.pdf>.
Fraser, Natalie. "The Black Market of Sperms and Eggs." The Lawyers Weekly. Web. 8 Dec.
2012.
"The Freezing of Human Oocytes (Eggs)." In Vitro Fertilization. Web. 08 Dec. 2012.
<http://www.ivf.com/freezing.html>.
Hans, Jason, Brigitte Dooley, and Laura Frey. Making Babies . . . with a Deceased Partner’s
Cryopreserved Gametes. Print.
Özmen, Batuhan, and Safaa Al-‐Hassani. "Techniques for Ovarian Tissue, Whole Ovary,
Oocyte and Embryo Cryopreservation." Journal of Reproduction and Infertility 42nd
ser. 11.1. Web.
