{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T05:24:44Z","timestamp":1786944284688,"version":"build-2736575974"},"reference-count":42,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T00:00:00Z","timestamp":1786924800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Endocrinol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>The immune system in the upper reproductive tract (URT) protects against sexually transmitted pathogens, while at the same time providing immune tolerance responses against allogenic sperm and the developing fetus. Estrus is the time point at which the cervix is most receptive to breeding and when intrauterine immunization is typically administered.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>The aim of the present study was to use confocal immunofluorescence to assess the intensity and cellular localization of Tight Junction (TJ) proteins Claudin-3 and Claudin-4 and TJ scaffold protein Zonula occludens-1 (ZO-1) in the luminal epithelium (LE) and glandular epithelium (GE) in the distal and medial uterine horn and the cervix, during diestrus and during estrus.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Claudin-4 expression was significantly reduced during estrus relative to diestrus in the distal uterine horn, with the exception of the cervix, where expression was unchanged between stages. Claudin-3 exhibited a broader pattern of estrous stage-associated reduction, with significantly lower expression during estrus than diestrus in the glandular epithelium of the distal uterine horn, in both epithelial compartments of the medial uterine horn, and in the cervical luminal epithelium. ZO-1 localization and expression were largely unaffected by estrous stage across all regions examined.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Together, these data reveal estrous stage-dependent and region-specific regulation of Claudin-4 and Claudin-3 consistent with selective remodeling without scaffold disruption in the porcine reproductive tract. To our knowledge, this is the first multi-regional analysis of tight junction protein expression across the distal uterine horn, medial uterine horn, and cervix of the porcine reproductive tract during the estrous cycle. These changes indicate modulation of tight junction composition that may correspond to altered epithelial barrier properties at estrus.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fendo.2026.1865472","type":"journal-article","created":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T04:37:08Z","timestamp":1786941428000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Tight junction-related proteins in the upper reproductive tract luminal and glandular epithelial cells are regionally regulated across the estrous cycle"],"prefix":"10.3389","volume":"17","author":[{"given":"Donaldson A.","family":"Magloire","sequence":"first","affiliation":[{"name":"Vaccine and Infectious Disease Organization, University of Saskatchewan","place":["Saskatoon, SK, Canada"]},{"name":"Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan","place":["Saskatoon, SK, 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