Pinopode

Last updated

Pinopodes (also known as pinopods and uterodomes) are protrusions on the apical cellular membrane of uterine epithelial cells. [1] [2]

Contents

Pinopodes have a pinocytotic role (hence the name pinopode - Greek for "drinking foot"), as well as a secretory role. [3] Their secretory vacuoles reach towards the lumen; The contents within the vesicle may provide necessary nutrients to the embryo. This feature also assists in its ability to attach to the uterine endometrium. With the development of pinipodes, there is a decrease in epithelial cell contact, which prompts blastocyst attachment and penetration. [2]

The usefulness of pinopodes as a marker for endometrial receptivity has been debated in past literature, [4] but is now generally accepted. [1]

Structure and morphology

Pinopodes are usually measured to be 5–10 μm. Their structure is dependent upon the organism's current stage of the menstrual cycle, [1] as pinopodes are regulated by the sex hormones, estrogen and progesterone. [2] Studies in the rat have shown that progesterone stimulates the development of pinopodes, while estrogen is responsible for their regression. [5] [6]

Generally, the first developmental stage occurs during the early luteal phase, around days 17-18 of the menstrual cycle. During this time, cellular bulging appears. The second mid-luteal stage of development, around days 20-22, is when the pinopodes are most prominent. During this peak phase, their structures look spherical and smooth, without microvilli. [7] Towards the end of the secretory phase, around days 23-35, the regression period occurs. In this stage, the structure shrivels and appears wrinkly. [8] Not every pinopode on the endometrial surface develops at the same time, affecting the consistency of distribution along the membrane. [2]

F-actin is found within pinopodes. The cytoskeleton is mainly made up of actin microfilaments. The structure varies between species. In rodents, pinopodes contain many vacuoles; Human pinopodes do not contain large vacuoles but do have secretory vesicles, a rough endoplasmic reticulum, and a golgi apparatus. Mitochondria and glycogen have been found in both rodent and human pinopodes. [2]

Endometrial receptivity

Previous literature had questioned the validity of the pinopodes' role in endometrial receptivity and implantation. [4] However, more recent literature has found correlations between the presence of pinopodes and endometrial receptivity. Women undergoing in-vitro fertilization with a high presence of pinopodes are more likely to have higher embryo implantation and pregnancy rates when compared to women with low pinopode coverage. [9] The implantation window is known as the period of time in which the endometrium is receptive to blastocyst attachment. [10] Due to pinopode development overlapping with the implantation window, blastocyst attachment takes place, which provides adhesion molecules necessary for the implantation process. [11] Current trials and research have shown pinopodes to be a reliable endometrial receptivity marker. [12]

Related Research Articles

<span class="mw-page-title-main">Endometrium</span> Inner mucous membrane of the mammalian uterus

The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer thickens and then is shed during menstruation in humans and some other mammals, including apes, Old World monkeys, some species of bat, the elephant shrew and the Cairo spiny mouse. In most other mammals, the endometrium is reabsorbed in the estrous cycle. During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and fetus. The speculated presence of an endometrial microbiota has been argued against.

<span class="mw-page-title-main">Menstrual cycle</span> Natural changes in the human female reproductive system

The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone. The uterine cycle governs the preparation and maintenance of the lining of the uterus (womb) to receive an embryo. These cycles are concurrent and coordinated, normally last between 21 and 35 days, with a median length of 28 days, and continue for about 30–45 years.

<span class="mw-page-title-main">Blastocyst</span> Structure formed around day 5 of mammalian embryonic development

The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the embryoblast which subsequently forms the embryo, and an outer layer of trophoblast cells called the trophectoderm. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoel. In the late blastocyst the trophectoderm is known as the trophoblast. The trophoblast gives rise to the chorion and amnion, the two fetal membranes that surround the embryo. The placenta derives from the embryonic chorion and the underlying uterine tissue of the mother.

Abnormal uterine bleeding (AUB), also known as (AVB) or as atypical vaginal bleeding, is vaginal bleeding from the uterus that is abnormally frequent, lasts excessively long, is heavier than normal, or is irregular. The term dysfunctional uterine bleeding was used when no underlying cause was present. Vaginal bleeding during pregnancy is excluded. Iron deficiency anemia may occur and quality of life may be negatively affected.

<span class="mw-page-title-main">Embryo transfer</span> Method of assisted reproduction

Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy. This technique - which is often used in connection with in vitro fertilization (IVF) - may be used in humans or in other animals, in which situations and goals may vary.

<span class="mw-page-title-main">Adenomyosis</span> Extension of endometrial tissue into the myometrium

Adenomyosis is a medical condition characterized by the growth of cells that proliferate on the inside of the uterus (endometrium) atypically located among the cells of the uterine wall (myometrium), as a result, thickening of the uterus occurs. As well as being misplaced in patients with this condition, endometrial tissue is completely functional. The tissue thickens, sheds and bleeds during every menstrual cycle.

<span class="mw-page-title-main">Luteal phase</span> The latter part of the menstrual cycle associated with ovulation and an increase in progesterone

The menstrual cycle is on average 28 days in length. It begins with menses during the follicular phase, followed by ovulation and ending with the luteal phase. Unlike the follicular phase which can vary in length among individuals, the luteal phase is typically fixed at approximately 14 days and is characterized by changes to hormone levels, such as an increase in progesterone and estrogen levels, decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), changes to the endometrial lining to promote implantation of the fertilized egg, and development of the corpus luteum. In the absence of fertilization by sperm, the corpus luteum atrophies leading to a decrease in progesterone and estrogen, an increase in FSH and LH, and shedding of the endometrial lining (menses) to begin the menstrual cycle again.

<span class="mw-page-title-main">Decidua</span> Part of uterus modified in pregnancy

The decidua is the modified mucosal lining of the uterus that forms every month, in preparation for pregnancy. It is shed off each month when there is no fertilised egg to support. The decidua is under the influence of progesterone. Endometrial cells become highly characteristic. The decidua forms the maternal part of the placenta and remains for the duration of the pregnancy. After birth the decidua is shed together with the placenta.

<span class="mw-page-title-main">Cytotrophoblast</span>

"Cytotrophoblast" is the name given to both the inner layer of the trophoblast or the cells that live there. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo.

<span class="mw-page-title-main">Implantation (embryology)</span> First stage of pregnancy

Implantation, also known as nidation, is the stage in the embryonic development of mammals in which the blastocyst hatches, attaches, adheres, and invades into the wall of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow.

<span class="mw-page-title-main">Decidualization</span>

Decidualization is a process that results in significant changes to cells of the endometrium in preparation for, and during, pregnancy. This includes morphological and functional changes to endometrial stromal cells (ESCs), the presence of decidual white blood cells (leukocytes), and vascular changes to maternal arteries. The sum of these changes results in the endometrium changing into a structure called the decidua. In humans, the decidua is shed during childbirth.

<span class="mw-page-title-main">Uterine gland</span>

Uterine glands or endometrial glands are tubular glands, lined by a simple columnar epithelium, found in the functional layer of the endometrium that lines the uterus. Their appearance varies during the menstrual cycle. During the proliferative phase, uterine glands appear long due to estrogen secretion by the ovaries. During the secretory phase, the uterine glands become very coiled with wide lumens and produce a glycogen-rich secretion known as histotroph or uterine milk. This change corresponds with an increase in blood flow to spiral arteries due to increased progesterone secretion from the corpus luteum. During the pre-menstrual phase, progesterone secretion decreases as the corpus luteum degenerates, which results in decreased blood flow to the spiral arteries. The functional layer of the uterus containing the glands becomes necrotic, and eventually sloughs off during the menstrual phase of the cycle.

<span class="mw-page-title-main">Glycodelin</span> Mammalian protein found in Homo sapiens

Glycodelin(GD) also known as human placental protein-14 (PP-14)progestogen-associated endometrial protein (PAEP) or pregnancy-associated endometrial alpha-2 globulin is a glycoprotein that inhibits cell immune function and plays an essential role in the pregnancy process. In humans is encoded by the PAEP gene.

Embryo culture is a component of in vitro fertilisation where in resultant embryos are allowed to grow for some time in an artificial medium.

Hormonal regulation occurs at every stage of development. A milieu of hormones simultaneously affects development of the fetus during embryogenesis and the mother, including human chorionic gonadotropin (hCG) and progesterone (P4).

<span class="mw-page-title-main">Chorionic gonadotropin beta</span> Protein-coding gene in the species Homo sapiens

Choriogonadotropin subunit beta (CG-beta) also known as chorionic gonadotrophin chain beta is a protein that in humans is encoded by the CGB gene.

The plasma membrane transformation is a concept introduced by Christopher R. Murphy of The University of Sydney to encapsulate the idea that a series of changes in the plasma membrane of uterine epithelial cells is essential to the development of the receptivity of the uterus (womb) for attachment of the blastocyst and the beginning of a pregnancy.

Embryo quality is the ability of an embryo to perform successfully in terms of conferring a high pregnancy rate and/or resulting in a healthy person. Embryo profiling is the estimation of embryo quality by qualification and/or quantification of various parameters. Estimations of embryo quality guides the choice in embryo selection in in vitro fertilization.

The internal surface of the uterus is lined by uterine epithelial cells which undergo dramatic changes during pregnancy. The role of the uterine epithelial cells is to selectively allow the blastocyst to implant at a specific time. All other times of the cycle, these uterine epithelial cells are refractory to blastocyst implantation. Uterine epithelial cells have a similar structure in most species and the changes which occur in the uterine epithelial cells at the time of blastocyst implantation are also conserved among most species.

Repeated implantation failure (RIF) is the repeated failure of the embryo to implant onto the side of the uterus wall following IVF treatment. Implantation happens at 6–7 days after conception and involves the embedding of the growing embryo into the mothers uterus and a connection being formed. A successful implantation can be determined by using an ultrasound to view the sac which the baby grows in, inside the uterus.

References

  1. 1 2 3 Quinn, Kelsey E.; Matson, Brooke C.; Wetendorf, Margeaux; Caron, Kathleen M. (2020). "Pinopodes: Recent advancements, current perspectives, and future directions". Molecular and Cellular Endocrinology. 501: 110644. doi:10.1016/j.mce.2019.110644. PMC   6962535 . PMID   31738970.
  2. 1 2 3 4 5 Rarani, Fahimeh Zamani; Borhani, Fatemeh; Rashidi, Bahman (2018). "Endometrial pinopode biomarkers: Molecules and microRNAs". Journal of Cellular Physiology. 233 (12): 9145–9158. doi:10.1002/jcp.26852. ISSN   0021-9541. PMID   29968908. S2CID   49645098.
  3. ↑ Kabir-Salmani, M et al. Secretory role for human uterodomes (pinopods): secretion of LIF. Molecular Human Reproduction 2005 11(8):553-559 http://molehr.oxfordjournals.org/cgi/content/full/11/8/553
  4. 1 2 Quinn, CE and Casper, RF. Pinopodes: a questionable role in endometrial receptivity. Human Reproduction Update 2009 15(2):229-236 http://humupd.oxfordjournals.org/cgi/content/abstract/15/2/229
  5. ↑ Singh, M.M; Trivedi, R.N; Chauhan, S.C; Srivastava, V.M.L; Makker, A; Chowdhury, S.R; Kamboj, V.P (1996). "Uterine estradiol and progesterone receptor concentration, activities of certain antioxidant enzymes and dehydrogenases and histoarchitecture in relation to time of secretion of nidatory estrogen and high endometrial sensitivity in rat". The Journal of Steroid Biochemistry and Molecular Biology. 59 (2): 215–224. doi:10.1016/S0960-0760(96)00102-1. PMID   9010337. S2CID   22892429.
  6. ↑ Sarantis, Loukia; Roche, Daniele; Psychoyos, Alexandra (1988). "Displacement of receptivity for nidation in the rat by progesterone antagonist RU 486: a scanning electron microscopy study". Human Reproduction. 3 (2): 251–255. doi:10.1093/oxfordjournals.humrep.a136688. ISSN   1460-2350. PMID   3356782.
  7. ↑ Quinn, C.E.; Casper, R.F. (2008-11-05). "Pinopodes: a questionable role in endometrial receptivity". Human Reproduction Update. 15 (2): 229–236. doi: 10.1093/humupd/dmn052 . ISSN   1355-4786. PMID   18997181.
  8. ↑ Nikas, George (2000). "Endometrial Receptivity: Changes in Cell-Surface Morphology". Seminars in Reproductive Medicine. 18 (3): 229–236. doi:10.1055/s-2000-12561. PMID   11299962. S2CID   20279113.
  9. ↑ Qiong, Zhang; Jie, Hao; Yonggang, Wang; Bin, Xu; Jing, Zhao; Yanping, Li (2017). "Clinical validation of pinopode as a marker of endometrial receptivity: a randomized controlled trial". Fertility and Sterility. 108 (3): 513–517.e2. doi: 10.1016/j.fertnstert.2017.07.006 . PMID   28807395.
  10. ↑ Harper, Michael J.K. (1992). "10 The implantation window". Baillière's Clinical Obstetrics and Gynaecology. 6 (2): 351–371. doi:10.1016/S0950-3552(05)80092-6. PMID   1424330.
  11. ↑ Da Broi, Michele G.; Rocha, Carlos V.; Carvalho, Filomena M.; Martins, Wellington P.; Ferriani, Rui A.; Navarro, Paula A. (2017). "Ultrastructural Evaluation of Eutopic Endometrium of Infertile Women With and Without Endometriosis During the Window of Implantation: A Pilot Study". Reproductive Sciences. 24 (10): 1469–1475. doi:10.1177/1933719117691142. ISSN   1933-7191. PMID   28173742. S2CID   206807308.
  12. ↑ Jin, X Y; Zhao, L J; Luo, D H; Liu, L; Dai, Y D; Hu, X X; Wang, Y Y; Lin, X; Hong, F; Li, T C; Zhang, S Y (2017-12-01). "Pinopode score around the time of implantation is predictive of successful implantation following frozen embryo transfer in hormone replacement cycles". Human Reproduction. 32 (12): 2394–2403. doi: 10.1093/humrep/dex312 . ISSN   0268-1161. PMID   29040606.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.