In vitro maturation
Encyclopedia
In vitro maturation is the technique of letting ovarian follicle
s mature in vitro
.
, starting with a primordial follicle, which then becomes a primary, secondary, early tertiary (antral), late tertiary and eventually a preovulatory follicle.
If a follicle has reached the early tertiary or antral stage, IVM can be carried out. A few live births have already been made by taking small early tertiary follicles, letting them mature in vitro and subsequently fertilizing them.
However, for follicles that haven't reached the early tertiary stage, IVM is still under development. There are a lot of cellular changes in the oocyte
and the rest of the cells in the follicle, which makes it very susceptible. Nevertheless, it is possible to let a primordial follicle mature to a secondary follicle outside the body by growing it in a slice of ovarian tissue. The subsequent maturity from secondary to early tertiary stage can then be supported in test-tubes.
IVM can be expanded with hCG-priming, which is exposing the ovarian tissue to human chorionic gonadotropin
(hCG). This results in an expanding or dispersed pattern of the cumulus oophorus
around the egg cell, facilitating its identification within follicular fluid. However, the evidence of a clinical effect of hCG priming is still lacking. IVM can also be expanded with intracytoplasmic sperm injection
(ICSI), which should be performed at least 1 h after the first polar body
extrusion.
Ovarian follicle
Ovarian follicles are the basic units of female reproductive biology, each of which is composed of roughly spherical aggregations of cells found in the ovary. They contain a single oocyte . These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single...
s mature in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
.
Techniques available
The ability of in IVM depends on how mature the follicle already is. There are several stages in folliculogenesisFolliculogenesis
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely-packed shell of somatic cells that contains an immature oocyte...
, starting with a primordial follicle, which then becomes a primary, secondary, early tertiary (antral), late tertiary and eventually a preovulatory follicle.
If a follicle has reached the early tertiary or antral stage, IVM can be carried out. A few live births have already been made by taking small early tertiary follicles, letting them mature in vitro and subsequently fertilizing them.
However, for follicles that haven't reached the early tertiary stage, IVM is still under development. There are a lot of cellular changes in the oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
and the rest of the cells in the follicle, which makes it very susceptible. Nevertheless, it is possible to let a primordial follicle mature to a secondary follicle outside the body by growing it in a slice of ovarian tissue. The subsequent maturity from secondary to early tertiary stage can then be supported in test-tubes.
IVM can be expanded with hCG-priming, which is exposing the ovarian tissue to human chorionic gonadotropin
Human chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
(hCG). This results in an expanding or dispersed pattern of the cumulus oophorus
Cumulus oophorus
The cumulus oophorus , also called discus proligerus, is a cluster of cells that surround the oocyte both in the ovarian follicle and after ovulation...
around the egg cell, facilitating its identification within follicular fluid. However, the evidence of a clinical effect of hCG priming is still lacking. IVM can also be expanded with intracytoplasmic sperm injection
Intracytoplasmic sperm injection
Intracytoplasmic sperm injection is an in vitro fertilization procedure in which a single sperm is injected directly into an egg.-Indications:...
(ICSI), which should be performed at least 1 h after the first polar body
Polar body
A polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. It is also known as a polar cell.Asymmetrical cell division leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated into the secondary...
extrusion.
Applications
- Facilitate IVF, and provide an alternative to ovulation inductionOvulation inductionOvulation induction is the stimulation of ovulation by medication. It is usually used in the sense of stimulation of the development of ovarian follicles to reverse anovulation or oligoovulation, but can also be used in the sense of triggering oocyte release from relatively mature ovarian follicles...
. Before an IVF, an ovarian hyperstimulation is usually performed. By injecting gonadotropins, multiple oocytes will mature. Similar methods are applied in ovulation induction for other purposes. However, with IVM, injection of gonadotropins into the body isn't essential. Rather, oocytes can mature outside the body, such as prior to IVF. However, there still isn't enough evidence to prove the effectiveness and security of the technique.
- For research. There are a million of oocytes in the ovary at birth, but only about 400 of these will be ovulated. The rest will die by Ovarian follicle atresiaOvarian follicle atresiaOvarian follicle atresia is the periodic process in which immature ovarian follicles degenerate and are subsequently re-absorbed during the follicular phase of the menstrual cycle. Typically around 20 follicles mature each month and only a single follicle is ovulated. The rest undergo atresia...
. When oocytes destined to die are extracted, IVM enables the maturation of these follicles. Thus, they can be studied to gather more information on folliculogenesis and oocyte maturation.