A novel homologous model for noninvasive monitoring of endometriosis progression†

Abstract

To date, several groups have generated homologous models of endometriosis through the implantation of endometrial tissue fluorescently labeled by green fluorescent protein (GFP) or tissue from luciferase-expressing transgenic mice into recipient animals, enabling noninvasive monitoring of lesion signal. These models present an advantage over endpoint models, but some limitations persist; use of transgenic mice is laborious and expensive, and GFP presents poor tissue penetration due to the relatively short emission wavelength. For this reason, a homologous mouse model of endometriosis that allows in vivo monitoring of generated lesions over time and mimics human lesions in recipient mice would be most desirable. In this regard, using C57BL/6 and B6N-Tyrc-Brd/BrdCrCrl mice, we optimized a decidualization protocol to obtain large volumes of decidual endometrium and mimic human lesions. Subsequently, to obtain a more robust and reliable noninvasive monitoring of lesions, we used the fluorescent reporter mCherry, which presents deeper tissue penetration and higher photostability, showing that endometrial tissue was properly labeled with 1 × 108 PFU/mL mCherry adenoviral vectors. mCherry-labeled endometriotic tissue was implanted in recipient mice, generating lesions that displayed characteristics typical of human endometriotic lesions, such as epithelial cells forming glands, local inflammation, collagen deposits, and new vessel formation. In vivo monitoring demonstrated that subcutaneous implantation on ventral abdomen of recipient mice provided the most intense and reliable signal for noninvasive lesion monitoring over a period of at least 20 days. This homologous model improves upon previously reported models of endometriosis and provides opportunities to study mechanism underlying endometriotic lesion growth and progression. We created a cost-effective but accurate homologous mouse model of endometriosis that allows the study of growth and progression of endometriotic lesions over early time points in lesion development through noninvasive monitoring.

Optimization of Endometrial Decidualization in the Menstruating Mouse Model for Preclinical Endometriosis Research

“…37 In addition, this is the first study in mice comparing different methods of intrauterine oil injection aimed at inducing decidualization in a randomized way, since earlier studies only compared endometrial scratching methods or intrauterine bead placement versus uterine oil injection methods. [38][39][40] Our macroscopic decidualization results are comparable to other studies describing a decidualization stimulus and showing signs of decidualization in 70% to 100% of animals. 15,[20][21][22]24,29 Nevertheless, exact comparison of our results to the literature is difficult due to the differences in the volume of injected oil, unicornuate versus bicornuate stimulation, and the use of the vaginal or laparotomic route to stimulate decidualization.…”

“…37 In addition, this is the first study in mice comparing different methods of intrauterine oil injection aimed at inducing decidualization in a randomized way, since earlier studies only compared endometrial scratching methods or intrauterine bead placement versus uterine oil injection methods. 38 –40…”

Endometriosis in the Mouse: Challenges and Progress Toward a ‘Best Fit’ Murine Model

“…The use of donor endometrium expressing red fluorescent protein (RFP) in disease induction facilitated non-invasive monitoring of lesion growth and regression for up to 33 days post transplantation in wild-type recipient mice (Wang et al, 2014). Ferrero et al (2017) developed a homologous murine model utilizing the fluorescent reporter mCherry, which resulted in deeper penetration and a more robust signal-to-noise ratio to longitudinally monitor lesions in vivo. In addition to luminescence, other methods of non-invasive in vivo analysis are described for visualization of the development of endometriotic lesions in mice.…”

“…For intraperitoneal injection models using decidualized endometrium, decidualization is often induced by injecting oil (Greaves et al, 2014;Forster et al, 2019;Horne et al, 2019;Kim et al, 2020) into, or by scratching (Ferrero et al, 2017), the uterine horn and harvesting the decidualized tissue with forceps. A variety of hormonal paradigms in ovariectomized or intact female mice are described to induce endometrial decidualization prior to harvest (Greaves et al, 2014;Ferrero et al, 2017;Forster et al, 2019;Horne et al, 2019;Kim et al, 2020). The uterine horn is opened longitudinally and the decidualized endometrium is dissected or scraped from the underlying myometrium (Kim et al, 2020).…”

Animal models of endometriosis: Replicating the aetiology and symptoms of the human disorder

“…introduced into a different mouse (recipient): a number of variations of this method have been reported(42,44,45,50). Standard methods include removal of uterine horns at diestrus, longitudinal opening of the horn to expose the endometrial lining which was cut into small fragments e.g.…”