Globular structure of human ovulatory cervical mucus

Abstract

Human cervical mucus is a heterogeneous mixture of mucin glycoproteins whose relative concentration changes during the ovulatory phases, thereby producing different mucus aggregation structures that can periodically permit the transit of spermatozoa for fertilization. In preovulatory phase, mucus is arranged in compact fiber-like structures where sperm transit is hindered. Previously, through observations made of fixed and dehydrated samples, a permissive structure in the ovulatory phase was attributed to the larger diameters of pores in the mucus network. Instead, by means of atomic force microscopy, we can show, for the first time, that unfixed ovulatory mucus is composed by floating globules of mucin aggregates. This finding sheds new light on the mechanism that governs spermatozoa transit toward the uterine cavity. In addition, we demonstrate that the switch from globular ovulatory to fibrous preovulatory mucus largely depends on a pH-driven mechanism. Analysis of mucin 5B primary sequence, the main mucin in ovulatory mucus, highlights pH-sensitive domains that are associated to flexible regions prone to drive aggregation. We suggest an involvement of these domains in the fiber-to-globule switch in cervical mucus.

Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses

“…Mucins have short hydrophobic domains (lipid-coated, nonglycosylated, cysteine-rich domains) interspersed between long glycosylated regions (5,32). The negatively charged glycosylated domains likely repel each other, but the hydrophobic domains may cause mucins to self-condense and/ or bundle together (33)(34)(35). To test this, we added 1% vol/vol of a nonionic detergent, (nonylphenoxy)polyethylene oxide, to the same mucus samples and again characterized the pore size.…”

Prospective Randomized Trial Comparing Embryo Transfers of Cases with and without Catheter Rotation during Its Withdrawal

“…Mucins are the main constituents of cervical mucus, while the concentration of other proteins starts to increase with progesterone secretion following ovulation. The pre-ovulatory fibrous structure of mucin becomes globular after ovulation, making it is less fibroelastic than its fibrous counterpart [14]. Mucus protein has been shown to have a non-Newtonian viscosity that is nonlinear with shear rate, such that it has strong resistance to deformation at low shear rates and weak resistance at high shear rates [15].…”

Ultrastructural and physico-chemical characterization of saliva during menstrual cycle in perspective of ovulation in human

“…Additionally, findings from the present study suggest that the sexual hormones may influence the changes in salivary flow rate and pH during ovulation phase. Electrolyte level, pH, buffer capacity, flow rate and ultra structure have been studied in saliva in reference to several diseases and physiological conditions (26)(27)(28)(29)(30)33,(36)(37)(38)(39)(40)(41)(42). The present study revealed the difference in the electrolytes, pH, buffer capacity and flow rate of saliva during the ovulation phase.…”