Reinstatement of "germinal epithelium" of the ovary

Two years ago, a research group of the University of Tennessee led by Antonin Bukovsky successfully demonstrated the oogenic process from the human ovarian covering epithelium now commonly called the ovarian surface epithelium. They showed the new oocyte with zona pellucida and granulosa cells, both originated from the surface epithelium arising from mesenchymal cells in the tunica albuginea, and stressed that the human ovary could form primary follicles throughout the reproductive period. This gives a big impact not only to the field of reproductive medicine, but also to the oncologic area. The surface epithelium is regarded as the major source of ovarian cancers, and most of the neoplasms exhibit the histology resembling müllerian epithelia. Since the differentiating capability of the surface epithelium has now expanded, 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 reasonably be reinstated.Unlike the avian ovary, where the follicles containing a large yolky egg look like a cluster of yellowish grapes, the human ovary is solid in structure, amygdaloid in shape, grayish white in color, and the follicles are usually invisible through the surface. Since the intraovarian follicle was firstly identified by Reinier De Graaf in 1672 [1], the origin of human oocyte has been disputed. Two opposing views have been known regarding the source of oocytes: (1) that they arise in the yolk sac [2-5], or (2) that they arise in the gonadal tissue itself [6-11]. The former view had gotten public consensus until the astonishing works by Bukovsky et al. on the capability of ovarian covering tissue to produce new oocytes in adult human females were published [12-15].A study of the histogenesis of ovarian components is essential