Estrous Cycle-dependent Morphology in the Reproductive Organs of the Female Göttingen Minipig

Abstract

The present study describes the normal histology of female reproductive organs during the estrous cycle in the Göttingen minipig. For this purpose, sexually mature females were sacrificed at different phases of the cycle (follicular/proliferation, ovulation, and early-, mid-, and late-luteal/ secretory phase). Ovaries, uterus, cervix, vagina, and mammary gland tissues were processed for microscopic evaluation. Sexual maturity was assured by selecting females in which at least 1 progesterone peak was measured. Stage-distinguishing features in ovaries were the Graafian follicles (disrupted vs. nondisrupted) and corpora lutea of recent and preceding cycles (size, cell morphology, and structural composition). In the uterus, stagespecific markers were epithelial morphology, secretory activity (using periodic acid-Schiff/hematoxylin staining), and epithelial mitosis and/or apoptosis. The other reproductive organs were not suitable to discriminate between the different phases of the cycle due to a high morphologic variability (mammary gland, and vagina) or absence of clear morphologic differences between the phases (cervix). The increased use of young minipigs (frequently immature/peripubertal) in preclinical testing requires more knowledge on the histologic cyclic changes. With the present morphologic description of the morphologic characteristics of the reproductive tract in recently ovulating minipigs, a guidance for staging the estrous cycle and determination of sexual immaturity is provided.

Genital tract lesions in sexually mature Göttingen minipigs during the initial stages of experimental vaginal infection with Chlamydia trachomatis serovar D

“…For histopathological evaluation, the slides were stained with haematoxylin and eosin, and examined without prior knowledge of experimental treatment. The phase of the oestrous cycle was determined as “peri-oestrus” (ranging from pro-oestrus to early di-oestrus) or “dioestrus”, based on histological changes in the uterine horns; Peri-oestrus if the epithelium was pseudostratified, subbasilary bands of neutrophils were found, and apoptotic cells were detected in the endometrial and/or glandular epithelium, and dioestrus if no apoptotic cells and subbasilar neutrophils were found, the epithelium was columnar and the glandular layer hypertrophic [32, 33]. …”

Species Comparison of Postnatal Development of the Female Reproductive System

“…The minipigs go into clinically evident estrus as per vaginal smear cytology 5 days after suspension of treatment (Lorenzen et al, ). In pigs and minipigs, the term estrus is primarily used to indicate the period of sexual behavior of the sow (Holtz et al, ) and is not really correlated to specific histologic features within the female reproductive organs (De Rijk et al, ).…”

“…In the rodent, typical assessments are made on physical hallmarks of sexual maturity (VO in conjunction with body weight effects) and estrous cyclicity by daily vaginal lavage, mating behavior, and reproductive performance can be routinely measured; on occasion, hormone assessments are added. In the minipig, the age of attainment of sexual maturity is published, but there is limited information on specific endpoints for assessing sexual maturity (Svendsen, ; Barrow, ; Tortereau et al, ; De Rijk et al, ). In the dog, VO and first estrous can be assessed along with clinical signs of the first heat, but due to the length of time to reach sexual maturity (26 to 39 weeks) and as there are commonly 6‐ to 7‐month intervals of anestrus between cycles, the dog is not considered practical (Robinson et al, ) to measure sexual maturation.…”

Integrated transcriptomes throughout swine oestrous cycle reveal dynamic changes in reproductive tissues interacting networks

“…The cyclic and sequential secretion of hormones from each reproductive tissue regulates morphological and functional changes in reproductive tissues to mediate the progression of the oestrous cycle 3 , 4 . The changes in hormonal milieu control ovarian activity which leads to follicular development, ovulation, luteinisation and luteolysis 5 .…”