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Ovum quality

September 01, 2023

Ovum quality is the measure of the ability of an oocyte (the female gamete) to achieve successful fertilisation. The quality is determined by the maturity of the oocyte and the cells that it comprises, which are susceptible to various factors which impact quality and thus reproductive success.[1] This is of significance as an embryo's development is more heavily reliant on the oocyte in comparison to the sperm.[1]

Factors Edit

Age Edit

Advanced maternal age represents a significant consideration for ovum health, and is currently regarded as the largest risk factor underlying instances of aneuploidy in human populations.[2] The mechanisms by which ovum health degenerates with age are incompletely understood. Extended meiotic arrest, a decline in mitochondrial function, and oxidative stress are key factors associated with ageing that are damaging to oocyte quality, identified in studies utilising both human and animal oocytes.[3]

Meiotic arrest and loss of cohesion Edit

The formation of human gametes involves two separation events, known distinctly as Meiosis I, in which paired homologous chromosomes are separated, and Meiosis II, in which sister chromatids are divided. Meiosis I is a slightly elongated process, during which homologous chromosomes align, pair, and recombine.[3]

While male gametes (sperm) are continuously produced throughout life, the female ovarian reserve is fully formed during early development. Oocytes (but not spermatocytes) then undergo a prolonged arrest at the end of diplotene, until meiosis resumes at the beginning of the menstrual cycle. It is during this prolonged arrest that age-dependent changes or deterioration may occur.[4]

During the oocyte's prolonged arrest, chromosomes exist as bivalents. This means that homologous chromosomes have paired, and are being held together by chiasmata (the physical crossovers between chromosome arms). The cohesin complex, a ring like structure associated with sister chromatids, helps to hold them in close proximity, therefore generating sister chromatid cohesion. This cohesion is later broken by the enzyme separase, allowing the chiasmata to be broken and homologous chromosomes to segregate in a normal way.[5]  Age-related degeneration of the inhibitors and regulators of separase, may lead to inappropriate and premature cohesin degradation before anaphase. As a result, homologous chromosomes may align independently on the meiotic spindle, risking aneuploidy that represents a key mechanism of reduced reproductive success.[5]

Mitochondrial changes Edit

As the most mitochondria-dense cells in the body, ova depend upon these organelles for early embryonic development, proliferation and their competence for fertilisation. Therefore, age-related changes to mitochondrial function naturally represent a significant influence on ovum quality and female fertility.[6]

Specific changes that occur with age include a reduction in quantity of mitochondrial DNA, as well as an increase in mitochondrial DNA mutations.[7] Animal studies have demonstrated these genetic abnormalities, in addition to physical changes in the mitochondria themselves and reduced ATP production.[8] Further investigation is required to establish definitive evidence for decreasing developmental potential as a result of aging mitochondria,[7] however the accumulation of mitochondrial abnormalities over time in the female ovum has been established, and appears linked in some way to declining ova health.[9]

Obesity Edit

Studies show that obesity affects the quality of the ovum. It is a disease which decreases the fertility of the female.[10] This is mainly due to causing a disturbance to maternal hormonal levels.[10] It is also possible for the uterus to have different levels of receptivity with regards to oocyte attachment, as a result of a disturbance to the function of the endometrium.[10] Furthermore, ingesting higher levels of carbohydrates and increased levels of glucose in the diet has been related to a higher chance of infertility because of the ovary failing to release oocytes at ovulation.[10] Obesity also has been linked to early miscarriages, deaths of the foetus, new-born or deaths where the baby is born dead and there is an increased chance of the babies having birth defects.[10]

In the IVF procedure a hormone called gonadotropin (GnRH) is given to the female to stimulate the ovaries to release oocytes.[10] In obese patients, their obesity negatively affects the ovaries responsiveness to this hormonal stimulant leading to doctors having to administrate an increased dose of the hormone and the duration of stimulation is increased.[10] Less mature oocytes are harvested. Moreover, obesity leads to decreased pregnancy rates after IVF and a smaller chance of the oocyte implanting to the uterine wall. They also have an increased chance of the cycle being cancelled.[10]

Damage from lipotoxicity Edit

An overload of fatty acids in the body due to increased ingestion can lead to lipotoxicity.[11] These extra fatty acids are not stored by the body and instead they circulate and damage the surrounding tissue. Levels of excess Fatty acids are higher in obese women.[11] The fatty acid will damage other cells, except for the adipocytes, by producing more reactive oxygen species. This causes the cell to self-destruct (apoptosis).[11]

Stress Edit

Psychological stress Edit

Psychological stress can contribute both directly and indirectly to decreased oocyte quality. Increased stress leads to an increased production and release of cortisol, a stress hormone, which directly inhibits the biosynthesis of estradiol in the ovary.[12] A decrease in estradiol as well as oxidative stress leads to apoptosis of the granulosa cells off the oocyte which deteriorates oocyte quality.[12]

References Edit

  1. ^ a b Coticchio, Giovanni; Sereni, Elena; Serrao, Lucia; Mazzone, Silvia; Iadarola, Immacolata; Borini, Andrea (December 2004). "What criteria for the definition of oocyte quality?". Annals of the New York Academy of Sciences. 1034 (1): 132–144. Bibcode:2004NYASA1034..132C. doi:10.1196/annals.1335.016. ISSN 0077-8923. PMID 15731306. S2CID 10691804.
  2. ^ Herbert, Mary; Kalleas, Dimitrios; Cooney, Daniel; Lamb, Mahdi; Lister, Lisa (2015-04-01). "Meiosis and maternal aging: insights from aneuploid oocytes and trisomy births". Cold Spring Harbor Perspectives in Biology. 7 (4): a017970. doi:10.1101/cshperspect.a017970. ISSN 1943-0264. PMC 4382745. PMID 25833844.
  3. ^ a b MacLennan, Marie; Crichton, James H.; Playfoot, Christopher J.; Adams, Ian R. (September 2015). "Oocyte development, meiosis and aneuploidy". Seminars in Cell & Developmental Biology. 45: 68–76. doi:10.1016/j.semcdb.2015.10.005. ISSN 1096-3634. PMC 4828587. PMID 26454098.
  4. ^ Jones, Keith T.; Lane, Simon I. R. (September 2013). "Molecular causes of aneuploidy in mammalian eggs". Development. 140 (18): 3719–3730. doi:10.1242/dev.090589. ISSN 1477-9129. PMID 23981655.
  5. ^ a b Cheng, Jin-Mei; Liu, Yi-Xun (2017-07-22). "Age-Related Loss of Cohesion: Causes and Effects". International Journal of Molecular Sciences. 18 (7): 1578. doi:10.3390/ijms18071578. ISSN 1422-0067. PMC 5536066. PMID 28737671.
  6. ^ May-Panloup, Pascale; Boucret, Lisa; Chao de la Barca, Juan-Manuel; Desquiret-Dumas, Valérie; Ferré-L'Hotellier, Véronique; Morinière, Catherine; Descamps, Philippe; Procaccio, Vincent; Reynier, Pascal (November 2016). "Ovarian ageing: the role of mitochondria in oocytes and follicles". Human Reproduction Update. 22 (6): 725–743. doi:10.1093/humupd/dmw028. ISSN 1460-2369. PMID 27562289.
  7. ^ a b Babayev, Elnur; Seli, Emre (June 2015). "Oocyte mitochondrial function and reproduction". Current Opinion in Obstetrics & Gynecology. 27 (3): 175–181. doi:10.1097/GCO.0000000000000164. ISSN 1473-656X. PMC 4590773. PMID 25719756.
  8. ^ Simsek-Duran, Fatma; Li, Fang; Ford, Wentia; Swanson, R. James; Jones, Howard W.; Castora, Frank J. (2013). "Age-associated metabolic and morphologic changes in mitochondria of individual mouse and hamster oocytes". PLOS ONE. 8 (5): e64955. Bibcode:2013PLoSO...864955S. doi:10.1371/journal.pone.0064955. ISSN 1932-6203. PMC 3669215. PMID 23741435.
  9. ^ Rebolledo-Jaramillo, Boris; Su, Marcia Shu-Wei; Stoler, Nicholas; McElhoe, Jennifer A.; Dickins, Benjamin; Blankenberg, Daniel; Korneliussen, Thorfinn S.; Chiaromonte, Francesca; Nielsen, Rasmus; Holland, Mitchell M.; Paul, Ian M. (2014-10-28). "Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA". Proceedings of the National Academy of Sciences of the United States of America. 111 (43): 15474–15479. Bibcode:2014PNAS..11115474R. doi:10.1073/pnas.1409328111. ISSN 1091-6490. PMC 4217420. PMID 25313049.
  10. ^ a b c d e f g h Luke, Barbara (April 2017). "Adverse effects of female obesity and interaction with race on reproductive potential". Fertility and Sterility. 107 (4): 868–877. doi:10.1016/j.fertnstert.2017.02.114. ISSN 1556-5653. PMID 28366413.
  11. ^ a b c Broughton, Darcy E.; Moley, Kelle H. (April 2017). "Obesity and female infertility: potential mediators of obesity's impact". Fertility and Sterility. 107 (4): 840–847. doi:10.1016/j.fertnstert.2017.01.017. ISSN 1556-5653. PMID 28292619.
  12. ^ a b Prasad, Shilpa; Tiwari, Meenakshi; Pandey, Ashutosh N.; Shrivastav, Tulsidas G.; Chaube, Shail K. (2016-03-29). "Impact of stress on oocyte quality and reproductive outcome". Journal of Biomedical Science. 23: 36. doi:10.1186/s12929-016-0253-4. ISSN 1423-0127. PMC 4812655. PMID 27026099.

September 01, 2023
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Ovum quality is the measure of the ability of an oocyte the female gamete to achieve successful fertilisation The quality is determined by the maturity of the oocyte and the cells that it comprises which are susceptible to various factors which impact quality and thus reproductive success 1 This is of significance as an embryo s development is more heavily reliant on the oocyte in comparison to the sperm 1 Contents 1 Factors 1 1 Age 1 1 1 Meiotic arrest and loss of cohesion 1 1 2 Mitochondrial changes 1 2 Obesity 1 2 1 Damage from lipotoxicity 1 3 Stress 1 3 1 Psychological stress 2 ReferencesFactors EditAge Edit Advanced maternal age represents a significant consideration for ovum health and is currently regarded as the largest risk factor underlying instances of aneuploidy in human populations 2 The mechanisms by which ovum health degenerates with age are incompletely understood Extended meiotic arrest a decline in mitochondrial function and oxidative stress are key factors associated with ageing that are damaging to oocyte quality identified in studies utilising both human and animal oocytes 3 Meiotic arrest and loss of cohesion Edit The formation of human gametes involves two separation events known distinctly as Meiosis I in which paired homologous chromosomes are separated and Meiosis II in which sister chromatids are divided Meiosis I is a slightly elongated process during which homologous chromosomes align pair and recombine 3 While male gametes sperm are continuously produced throughout life the female ovarian reserve is fully formed during early development Oocytes but not spermatocytes then undergo a prolonged arrest at the end of diplotene until meiosis resumes at the beginning of the menstrual cycle It is during this prolonged arrest that age dependent changes or deterioration may occur 4 During the oocyte s prolonged arrest chromosomes exist as bivalents This means that homologous chromosomes have paired and are being held together by chiasmata the physical crossovers between chromosome arms The cohesin complex a ring like structure associated with sister chromatids helps to hold them in close proximity therefore generating sister chromatid cohesion This cohesion is later broken by the enzyme separase allowing the chiasmata to be broken and homologous chromosomes to segregate in a normal way 5 Age related degeneration of the inhibitors and regulators of separase may lead to inappropriate and premature cohesin degradation before anaphase As a result homologous chromosomes may align independently on the meiotic spindle risking aneuploidy that represents a key mechanism of reduced reproductive success 5 Mitochondrial changes Edit As the most mitochondria dense cells in the body ova depend upon these organelles for early embryonic development proliferation and their competence for fertilisation Therefore age related changes to mitochondrial function naturally represent a significant influence on ovum quality and female fertility 6 Specific changes that occur with age include a reduction in quantity of mitochondrial DNA as well as an increase in mitochondrial DNA mutations 7 Animal studies have demonstrated these genetic abnormalities in addition to physical changes in the mitochondria themselves and reduced ATP production 8 Further investigation is required to establish definitive evidence for decreasing developmental potential as a result of aging mitochondria 7 however the accumulation of mitochondrial abnormalities over time in the female ovum has been established and appears linked in some way to declining ova health 9 Obesity Edit Studies show that obesity affects the quality of the ovum It is a disease which decreases the fertility of the female 10 This is mainly due to causing a disturbance to maternal hormonal levels 10 It is also possible for the uterus to have different levels of receptivity with regards to oocyte attachment as a result of a disturbance to the function of the endometrium 10 Furthermore ingesting higher levels of carbohydrates and increased levels of glucose in the diet has been related to a higher chance of infertility because of the ovary failing to release oocytes at ovulation 10 Obesity also has been linked to early miscarriages deaths of the foetus new born or deaths where the baby is born dead and there is an increased chance of the babies having birth defects 10 In the IVF procedure a hormone called gonadotropin GnRH is given to the female to stimulate the ovaries to release oocytes 10 In obese patients their obesity negatively affects the ovaries responsiveness to this hormonal stimulant leading to doctors having to administrate an increased dose of the hormone and the duration of stimulation is increased 10 Less mature oocytes are harvested Moreover obesity leads to decreased pregnancy rates after IVF and a smaller chance of the oocyte implanting to the uterine wall They also have an increased chance of the cycle being cancelled 10 Damage from lipotoxicity Edit An overload of fatty acids in the body due to increased ingestion can lead to lipotoxicity 11 These extra fatty acids are not stored by the body and instead they circulate and damage the surrounding tissue Levels of excess Fatty acids are higher in obese women 11 The fatty acid will damage other cells except for the adipocytes by producing more reactive oxygen species This causes the cell to self destruct apoptosis 11 Stress Edit Psychological stress Edit Psychological stress can contribute both directly and indirectly to decreased oocyte quality Increased stress leads to an increased production and release of cortisol a stress hormone which directly inhibits the biosynthesis of estradiol in the ovary 12 A decrease in estradiol as well as oxidative stress leads to apoptosis of the granulosa cells off the oocyte which deteriorates oocyte quality 12 References Edit a b Coticchio Giovanni Sereni Elena Serrao Lucia Mazzone Silvia Iadarola Immacolata Borini Andrea December 2004 What criteria for the definition of oocyte quality Annals of the New York Academy of Sciences 1034 1 132 144 Bibcode 2004NYASA1034 132C doi 10 1196 annals 1335 016 ISSN 0077 8923 PMID 15731306 S2CID 10691804 Herbert Mary Kalleas Dimitrios Cooney Daniel Lamb Mahdi Lister Lisa 2015 04 01 Meiosis and maternal aging insights from aneuploid oocytes and trisomy births Cold Spring Harbor Perspectives in Biology 7 4 a017970 doi 10 1101 cshperspect a017970 ISSN 1943 0264 PMC 4382745 PMID 25833844 a b MacLennan Marie Crichton James H Playfoot Christopher J Adams Ian R September 2015 Oocyte development meiosis and aneuploidy Seminars in Cell amp Developmental Biology 45 68 76 doi 10 1016 j semcdb 2015 10 005 ISSN 1096 3634 PMC 4828587 PMID 26454098 Jones Keith T Lane Simon I R September 2013 Molecular causes of aneuploidy in mammalian eggs Development 140 18 3719 3730 doi 10 1242 dev 090589 ISSN 1477 9129 PMID 23981655 a b Cheng Jin Mei Liu Yi Xun 2017 07 22 Age Related Loss of Cohesion Causes and Effects International Journal of Molecular Sciences 18 7 1578 doi 10 3390 ijms18071578 ISSN 1422 0067 PMC 5536066 PMID 28737671 May Panloup Pascale Boucret Lisa Chao de la Barca Juan Manuel Desquiret Dumas Valerie Ferre L Hotellier Veronique Moriniere Catherine Descamps Philippe Procaccio Vincent Reynier Pascal November 2016 Ovarian ageing the role of mitochondria in oocytes and follicles Human Reproduction Update 22 6 725 743 doi 10 1093 humupd dmw028 ISSN 1460 2369 PMID 27562289 a b Babayev Elnur Seli Emre June 2015 Oocyte mitochondrial function and reproduction Current Opinion in Obstetrics amp Gynecology 27 3 175 181 doi 10 1097 GCO 0000000000000164 ISSN 1473 656X PMC 4590773 PMID 25719756 Simsek Duran Fatma Li Fang Ford Wentia Swanson R James Jones Howard W Castora Frank J 2013 Age associated metabolic and morphologic changes in mitochondria of individual mouse and hamster oocytes PLOS ONE 8 5 e64955 Bibcode 2013PLoSO 864955S doi 10 1371 journal pone 0064955 ISSN 1932 6203 PMC 3669215 PMID 23741435 Rebolledo Jaramillo Boris Su Marcia Shu Wei Stoler Nicholas McElhoe Jennifer A Dickins Benjamin Blankenberg Daniel Korneliussen Thorfinn S Chiaromonte Francesca Nielsen Rasmus Holland Mitchell M Paul Ian M 2014 10 28 Maternal age effect and severe germ line bottleneck in the inheritance of human mitochondrial DNA Proceedings of the National Academy of Sciences of the United States of America 111 43 15474 15479 Bibcode 2014PNAS 11115474R doi 10 1073 pnas 1409328111 ISSN 1091 6490 PMC 4217420 PMID 25313049 a b c d e f g h Luke Barbara April 2017 Adverse effects of female obesity and interaction with race on reproductive potential Fertility and Sterility 107 4 868 877 doi 10 1016 j fertnstert 2017 02 114 ISSN 1556 5653 PMID 28366413 a b c Broughton Darcy E Moley Kelle H April 2017 Obesity and female infertility potential mediators of obesity s impact Fertility and Sterility 107 4 840 847 doi 10 1016 j fertnstert 2017 01 017 ISSN 1556 5653 PMID 28292619 a b Prasad Shilpa Tiwari Meenakshi Pandey Ashutosh N Shrivastav Tulsidas G Chaube Shail K 2016 03 29 Impact of stress on oocyte quality and reproductive outcome Journal of Biomedical Science 23 36 doi 10 1186 s12929 016 0253 4 ISSN 1423 0127 PMC 4812655 PMID 27026099 Retrieved from https en wikipedia org w index php title Ovum quality amp oldid 1093172841, wikipedia, wiki, book, books, library,

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