Characterization of the cervical mucus plug in mares.

This research explores the proteins found in the cervical mucus plug (CMP) of horses during late stages of pregnancy. Discoveries indicate that the CMP, essential for keeping the pregnancy healthy by preventing microbial infections, consists of various proteins primarily sourced from the cervical mucosa.

Research Process

• The research involved collecting CMPs from four horses in their ninth month of gestation. The researchers characterized these samples’ protein composition using a technique known as nano-Liquid Chromatography tandem Mass Spectrometry (nano-LC-MS/MS).
• Results were then compared against the EquCab2.0, a reference of horse biological data. Ingenuity Pathway Analysis was employed to predict the proteomic pathways, helping the researchers understand the functional connections of these proteins.
• For more visual examination, the team performed Hematoxylin and Eosin (H&E) staining and Periodic Acid Schiff (PAS) staining on histologic sections of the CMP.

Key Findings

• From the CMP samples, a complex variety of proteins was discovered, many of which were linked to immune functions—a vital aspect to secure pregnancy by preventing infections.
• The research showed that proteins, usually assumed as originating from the endometrium (the lining of the uterus), were produced by the cervical mucosa. This discovery suggests that the CMP’s primary source is the cervical mucosa itself.

Further Investigation

• To trace the origin of abundant proteins in the CMP, the researchers conducted quantitative real-time polymerase chain reaction (qPCR) tests on endometrial and cervical mucosal mRNA obtained from horses during different stages: estrus, diestrus, and at four and ten months of gestation.
• They focused on transcripts for a series of important proteins implicated in immune responses and biological actions of the uterus, such as lactotransferrin, uterine serpin 14, uteroglobin, uteroferrin, and the proteins known as deleted in malignant brain tumors 1 and mucins 4, 5b, and 6.

Conclusion

In conclusion, the research illuminated that CMP composition in horses is regulated specifically not only in pregnancy but also throughout the estrous cycle. This unique composition manifests structural and functional barriers to protect the fetus and fetal membranes from possible infections during pregnancy, exemplifying the CMP’s vital role in a successful and healthy equine gestation.