ooycte originate from ovarian surface-a new concept
OOCYTE ORIGINATE FROM OVARIAN SURFACE EPITHELIUM –A NEW CONCEPT
Ghulam M ohyuddin.Wani DVM,PhD and Gazanfer Wani MB
ovarian surface epithelium
The ovarian germinal epithelium has not the special capacity to form new germ cells.The oocyte originates from the ovarian epithelium istead .Thus ovarian surface epithelium assumes an importance. The new oocyte with zona pellucida and granulosa cells all originate from the surface epithelium.
It means the human ovary could form primary follicles throughout the reproductive period. This opens a new window for reproductive medicine where the surface epithelium is regarded as the major source of ovarian cancers, and most of the neoplasms exhibit the histology resembling müllerian epithelia.
With the differentiating capability of the surface epithelium, the histologic range of the neoplasms in this category may extend to include both germ cell tumors and sex cord-stromal cell tumors. Since the oogenic capability of ovarian surface cells has been proven, it is now believed that the oocytes can originate from them. The term “germinal epithelium”, hence, might become reductant.
The Müllerian ducts differentiate after invagination of the coelomic mesothelium over the gonadal ridges during the 6th week of embryonic life.
On the basis of ovarian epithelium theory of follicle development endometriosis can be explained. A three-dimensional culture system demonstrated that human ovarian surface epithelial cells exhibited a glandular-stromal structure when they were co-cultured with endometrial stromal cells in an estrogen-rich environment.
Ovarian carcinomas in the epithelial-stromal category are thought to arise from the surface epithelium. The ovarian surface epithelium is physiologically involved in follicular rupture, oocyte release, and the subsequent repair of follicle wall during reproductive age. Simultaneously, ovulation may cause a loss of integrity of the surface epithelium, followed by accumulation of multiple mutations. The cortical invagination, surface stromal proliferation, and Müllerian differentiation of these cells are likely not to be an early step in the cancer development.
Most epithelial ovarian carcinomas have been suggested to arise from the ovarian surface epithelium, which covers an ovary as a layer of flat to cuboidal cells. The epithelium is physiologically involved in follicular rupture and the subsequent repair of the follicle wall during reproductive age. Invagination and inclusion cysts are formed in the cortical stroma after cyclic ovulation. Consequently, ovulation may cause a loss of integrity of the surface epithelium followed by stepwise sequence of genetic alteration. Inclusion cysts are actually more common in ovaries
Human ovarian surface epithelial cells exhibit a gland formation in co -culture with endometrial stromal cells in an estrogen-rich environment. The phenotypic plasticity of these cells shares a mesenchymal property when they are cultured on two layers of extracellular matrix and collagen gel. As in vitro study of ovarian carcinogensis, several neoplastic cell lines were recently established from the surface epithelial cells of the human ovary.
Recently in vitro culture of ovarian surface epithelium (OSE) and granulosa cells of humans, were investigated and a protocol developed for the immortalization of each cell. The immortalized cell lines may supply us advanced studies on ovarian disorders as well as its physiological functions.
Ovarian granulosa cells play a key role in the functional maturation of the entire follicle. The molecular pathways in granulosa cells responsible for the growth, differentiation, and nursing the oocyte are still largely unknown.
Stem cells, with their unlimited self-renewal feature and their ability to differentiate into almost every mature cell type in the body, have enormous potential for research and therapeutic application.
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