Detection of zona pellucida proteins during human folliculogenesis

Abstract

BACKGROUND: The stage of folliculogenesis at which the human zona pellucida (ZP) is initiated and the cells responsible for the origin of the ZP continue to be controversial. This study characterizes the development of the ZP during human folliculogenesis using ovarian samples donated from patients requesting ovarian storage. METHODS: Follicles (from n 5 18 patients, 14-40 years old) within fresh tissue and following development in a xenograft system were stained, using immunohistochemical techniques, for the presence of the three human ZP proteins, ZP1, ZP2 and ZP3. Over 500 primordial follicles and >20 follicles at each developmental stage were examined. RESULTS: All three ZP proteins were detected within the oocyte of the primordial follicle. Presence of ZP1 and ZP3 was observed in the majority of primordial oocytes (93% and 95%, respectively), whereas ZP2 was detected in only 32% of these follicles. The three ZP proteins were detected in the cytoplasm of cuboidal granulosa cells and their distribution correlates with developmental stages throughout folliculogenesis. CONCLUSIONS: ZP proteins were detected in both the oocyte and the granulosa cells as early as the primordial follicle stage in the human. The detection of ZP proteins in the quiescent primordial follicle suggests that these proteins have been present since oogenesis.

Gene Expression Analysis of Human Fetal Ovarian Primordial Follicle Formation

“…In women, ZP1 and ZP3 are expressed in oocytes of most primordial follicles, whereas ZP2 is only detected in one third of primordial follicle oocytes although all three proteins are detected in cuboidal granulosa cells (50). Only ZP1 and ZP3 have been previously reported (51) in human fetal ovaries, and whereas expression of ZP1 was low, ZP3 was present at 11 wk and strongly present in oocytes from 17 wk onward.…”

Is the zona pellucida thickness of human embryos influenced by women's age and hormonal levels?

“…The human ZP is formed during early folliculogenesis, and consists of four glycoproteins (ZP1-ZP4) which are actively secreted by oocytes and granulosa cells that support the growth of ova (5,6). The ability of embryos to hatch from their ZP is recognized as one of the critical embryonic processes affecting the implantation rates in human assisted reproduction (7)(8)(9)(10).…”

Evaluation of zona pellucida birefringence intensity during in vitro maturation of oocytes from stimulated cycles

“…Gook et al [13] have demonstrated that ZP protein levels increase in the cytoplasmic granulosa cells during follicular development. The presence of these ZP proteins has been also detected in primordial follicles during oogenesis.…”