Animal models of adenomyosis as a basis for the development of new treatment methods. Part I. Creation of a highly reproducible model of adenomyosis in female Wistar rats

BACKGROUND: The creation of an experimental model of adenomyosis is of scientific and practical interest, which allows for the evaluation of the effectiveness and pathogenetically substantiated therapy of adenomyosis in the future on the created highly reproducible model of the disease. AIM: The aim of this study was to create a highly reproducible model of adenomyosis in neonatal Wistar rats. MATERIALS AND METHODS: This article presents the first stage of the experiment on newborn Wistar rats, including the creation of a highly reproducible model of adenomyosis with different schemes and frequency of tamoxifen administration, as well as different periods of animal withdrawal. To achieve the set goal, 26 newborn female rats were orally administered an estrogen receptor blocker (tamoxifen 20 mg) at a rate of 1 mg of the drug per 1 kg of animal body weight once a day. To determine the most optimal regimen for administering tamoxifen, the animals were divided into four groups. Group 1 (n = 6) received the drug from day 2 to day 5 of postembryonic development. Group 2 (n = 8) received the drug from day 3 to day 8. Group 3 (n = 7) received the drug twice: from day 3 to day 8 and from day 25 to day 29. Group 4 (control, n = 5) only received water without the drug. The animals were withdrawn from the experiment on days 16, 30, and 90. Adenomyosis was confirmed by morphological examination. RESULTS: Tamoxifen should be administered once to create an adequate rat model of adenomyosis, from day 2 to day 5 of postembryonic development, and the animals should be withdrawn from the experiment on day 30 of life, when the severity of the disease is sufficient and is confirmed by morphological examination. Such the scheme is reproducible and economically advantageous. CONCLUSIONS: The creation of the described model of adenomyosis is important for conducting further studies on the treatment of the disease using various schemes, methods, and dosages in alternative methods of therapy to be described in the second part of the experiment.