Roles of the ovarian surface epithelium in ovulation and carcinogenesis

Abstract

The mammalian ovary is covered by a singular layer of epithelial cells. The rather unassuming character of the ovarian surface epithelium has generally inclined reproductive physiologists to question its functional significance. However, recent experimental evidence indicates that the ovarian epithelium is an obligate component of the ovulatory process. That most ovarian cancers arise by transformation of a surface epithelial cell affected by ovulation has been a point of theory for three decades. The objectives of this overview are to consider the morphology and developmental biology of the ovarian surface epithelium and to delineate its apparent roles in ovulation and pathogenesis. Anatomy and embryonic origin of the ovarian surface epitheliumOvarian surface epithelial cells vary in type from simple squamous to cuboidal to low pseudostratified columnar. The surface epithelium is supported over the ovarian cortical interstitium (tunica albuginea) by a basement membrane ( Fig. 1) and is held together laterally by desmosomes and gap or tight junctional complexes. Surface cells are continuous at the hilum with the mesothelium of the ovarian ligament (mesovarium) and peritoneum. Preferential outgrowth of a preovulatory follicle brings it into close apposition with the ovarian surface. In most mammals, the entire surface of the ovary, other than those regions disrupted by ovulation, is covered by epithelial cells. However, in equids, the ovarian epithelium (and ovulation) is restricted to a discrete area of depression known as the fossa, and the remainder of the ovary is encased by serosa-containing elastic bands of connective tissue (Walt et al., 1979). Ovarian surface epithelial cells have a mesodermal derivation shared with the epithelia of the urogenital system and adrenal cortex. Mesoderm segregates during embryonic development into pluripotent mesenchyme and coelomic epithelium (peritoneal mesothelium). Mullerian mesothelium is the precursor of oviductal, endometrial, and cervical epithelia. Ovarian surface epithelium differentiates after invagination of the coelomic mesothelium over the gonadal ridges (Byskov, 1986). In species with an ovulation fossa, the cortex (with modified epithelium) migrates into the medullary portion of the ovary during the postnatal period (Walt et al., 1979). Early investigators assumed that ova were derived from the ovarian surface; hence, the misnomer 'germinal' epithelium. Role of the ovarian surface epithelium in the mechanism of ovulatory follicular ruptureThe contention that ovarian surface epithelial cells participate actively in the biomechanics of gonadotrophin-induced Although ovarian mechanisms of ovulation have been a subject of investigation for more than a century, essential regulatory pathways remain uncertain. A role for the ovarian surface epithelium in ovulation has recently been demonstrated. Ovarian surface epithelial cells in close contact with the apical wall of preovulatory ovine follicles secrete a urokinasetype plasminogen activator in response to surge conc...

The emerging role of CXC chemokines in epithelial ovarian cancer

“…Regular cycling and release of ova from the ovary causes the ovarian epithelium to undergo regular cycles of wounding and repair throughout a female's reproductive life. This process is generally considered to induce an inflammatory response and triggers (Murdoch et al 2010) the secretion of a large number of chemokines, cytokines, enzymes and growth factors (Murdoch & McDonnel 2002).…”

Cyclooxygenases expression and distribution in the normal ovary and their role in ovarian cancer in the domestic hen (Gallus domesticus)

“…Common epithelial ovarian cancer is related to the successive rounds of ovulation and subsequent wound healing process characterized by OSE mitosis. The integrity of the DNA of these surface cells surrounding the ovarian rupture site is compromised during ovulation, and rapid growth of cells with mutated DNA may result in the initiation of carcinogenesis [36]. The role of inflammation and oxidative damage to the pathogenesis of cancer has gained much attention [37,38].…”

Interleukin‐13 receptor α2 chain

“…8 The literature is replete with references showing that inflammatory or immune reactions play a key role in the development and progression of cancer as a result of the natural host response to cancer, often along with normal tissue remodeling. 9 It has been suggested that damage in the ovarian epithelium resulting from repeated ovulations may play a role in the development of cancer. These processes are coordinated by a number of growth factors, cytokines, chemokines, and their receptors.…”