Endometriosis origin from primordial germ cells

Abstract

Endometriosis is defined by the presence of endometrial ectopia. Multiple hypotheses have been postulated to explain the etiology of endometriosis to understand various clinical evidences. The etiology of endometriosis is still unclear.The primary question to understanding the etiology of endometrial ectopia (endometriosis) is determining the origin of eutopic (normally cited) endometrium.According to the new theory, primordial germ cells migrate from hypoblast (yolk sac close to the allantois) to the gonadal ridges. The gonadal ridges which composed of primordial germ cells derive to the: eutopic endometrium, ovary, ovarian ligament and ligamentum teres uteri.There are 2 principal processes in uterine organogenesis: the intersection of gonadal ridges with mesonephral ducts to form the uterine folds with an endometrial cavity and the fusion of the both uterine folds together to form the unicavital (normal) uterus. In the uterine folds there are closer cell-to-cell communications, polypotential germ cells differentiate and grow into myometrium and endometrial layers.Some of the polypotential germ cells fail to reach the ridges and stay in the peritoneal cavity, where they may be transforming into external endometrial heterotopies.The main insight in the etiology of endometriosis is polypotential germ cells origin, which may explain its potency, pathogenesis and expansion.

Keywords: adenomyosis; congenital anomaly; ectopic endometrium; endometriosis; endometriosis aetiology; eutopic endometrium; genital ridge; germ cells; stem cells; uterovaginal embryogenesis.

FIGURE 1.

Primordial germ cells migration pathway. Zygote is totipotent. The blastomeres are pluripotent. Due to asynchronous division the initial population of blastomeres in the vegetative pole preserves their potency. Primordial germ cells are located first at the vegetative pole of blastocyst, then in the hypoblast (yolk sac) to avoid of differentiation signals and maintain the polypotency. After gastrulation the primordial germ cells migrate by amoeboid movement back to the embryo through the peritoneum to the dorsolateral gonadal ridges.

FIGURE 2.

The luteinization of unovulated follicle (LUF syndrome) in the left ovary: a corpus luteum with endometriotic lesions on the upper pole without ovulatory stigma.

FIGURE 3.

Patient with uterovaginal aplasia (Mayer-Rokitansky-Kuster-Hauser syndrome) and non-functioning uterine rudiments had extra-genital endometriosis on the peritoneal surface.