Granulosa cell
Encyclopedia
A granulosa cell or follicular cell is a somatic cell
of the sex cord
that is closely associated with the developing female gamete
(called an oocyte
or egg) in the ovary
of mammal
s.
, and later in follicle development (folliculogenesis
), granulosa cells advance to form a multilayered cumulus oophorus
surrounding the oocyte
in the preovulatory or Graafian follicle.
The major functions of granulosa cells include the production of sex steroid
s, as well as myriad growth factors thought to interact with the oocyte
during its development. The sex steroid production consists of follicle-stimulating hormone
(FSH) stimulating granulosa cells to convert androgens (coming from the thecal cells) to estradiol
by aromatase
during the follicular phase
of the menstrual cycle
. However, after ovulation the granulosa cells turn into granulosa lutein cells that produce progesterone
. The progesterone may maintain a potential pregnancy and causes production of a thick cervical mucus that inhibits sperm entry into the uterus.
, the oogonia become invaginated in the gonadal ridge
.
In the 1970’s, evidence emerged that the first cells to make contact with the oogonia were of mesonephric origin. It was suggested that mesonephric cells already closely associated with the oogonia proliferated throughout development to form the granulosa cell layer.
Recently this hypothesis has been challenged with some thorough histology. Sawyer et al. hypothesised that in sheep most of the granulosa cells develop from cells of the mesothelium
(i.e., epithelial cells from the presumptive surface epithelium of the ovary).
The embryological origin of granulosa cells remains controversial.
of granulosa cells can be performed in vitro
. Plating density (number of cells per volume of culture medium) plays a critical role for the differentiation. A lower plating density makes granulosa cells exhibit estrogen production, while a higher plating density makes them appear as progesterone
producing theca lutein cells.
Somatic cell
A somatic cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell...
of the sex cord
Sex cord
In animal embryology, the gonadal cords or sex cords are structures that develop from the gonadal ridge. After sexual differentiation, in males the sex cords become the testis cords, which help develop and nourish the Sertoli cells, while in females they become the cortical cords.-External...
that is closely associated with the developing female gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
(called an 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...
or egg) in the ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s.
Anatomy and function
In the primary ovarian follicleOvarian 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...
, and later in follicle development (folliculogenesis
Folliculogenesis
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely-packed shell of somatic cells that contains an immature oocyte...
), granulosa cells advance to form a multilayered 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...
surrounding 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...
in the preovulatory or Graafian follicle.
The major functions of granulosa cells include the production of sex steroid
Sex steroid
Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptors. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and...
s, as well as myriad growth factors thought to interact with 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...
during its development. The sex steroid production consists of follicle-stimulating hormone
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...
(FSH) stimulating granulosa cells to convert androgens (coming from the thecal cells) to estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...
by aromatase
Aromatase
Aromatase is an enzyme responsible for a key step in the biosynthesis of estrogens. It is a member of the cytochrome P450 superfamily , which are monooxygenases that catalyze many reactions involved in steroidogenesis. In particular, aromatase is responsible for the aromatization of androgens into...
during the follicular phase
Follicular phase
The follicular phase is the phase of the estrous cycle, during which follicles in the ovary mature. It ends with ovulation. The main hormone controlling this stage is estradiol....
of the menstrual cycle
Menstrual cycle
The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
. However, after ovulation the granulosa cells turn into granulosa lutein cells that produce progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
. The progesterone may maintain a potential pregnancy and causes production of a thick cervical mucus that inhibits sperm entry into the uterus.
Embryology of ovarian granulosa cells
In the development of the urinary and reproductive organsDevelopment of the urinary and reproductive organs
The development of the urinary and reproductive organs as a part of the prenatal development, concerns the urinary system and sex organs. The latter is a part of the stages of sexual differentiation....
, the oogonia become invaginated in the gonadal ridge
Gonadal ridge
In embryology, the gonadal ridge is the precursor to the gonads. The gonadal ridge initially consists mainly of mesenchyme and cells of underlying mesonephric origin. Once oogonia enter this area they attempt to associate with these somatic cells...
.
In the 1970’s, evidence emerged that the first cells to make contact with the oogonia were of mesonephric origin. It was suggested that mesonephric cells already closely associated with the oogonia proliferated throughout development to form the granulosa cell layer.
Recently this hypothesis has been challenged with some thorough histology. Sawyer et al. hypothesised that in sheep most of the granulosa cells develop from cells of the mesothelium
Mesothelium
The mesothelium is a membrane that forms the lining of several body cavities: the pleura , peritoneum and pericardium . Mesothelial tissue also surrounds the male internal reproductive organs and covers the internal reproductive organs of women...
(i.e., epithelial cells from the presumptive surface epithelium of the ovary).
The embryological origin of granulosa cells remains controversial.
Cell culture
Cell cultureCell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
of granulosa cells can be performed 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...
. Plating density (number of cells per volume of culture medium) plays a critical role for the differentiation. A lower plating density makes granulosa cells exhibit estrogen production, while a higher plating density makes them appear as progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...
producing theca lutein cells.