We thank Dr. Naojiro Minami (Kyoto University) for providing the Oog1pro3.9 mice. This research was supported by the JSPS (KAKENHI # JP15H06275) and the Nitto Foundation.

Mice were housed in an environmentally controlled room at 23 &#177;1 &#176;C with a 12 h light/12 h dark cycle. Animal care protocols and experiments were conducted in accordance with the Guidelines for Animal Experimentation at Aichi Medical University and were approved by the incumbent Animal Care and Use Committee.
1. Preparation of Culture Medium and Dishes
<ol>
	<li>To prepare basic culture medium, add fetal bovine serum (FBS, 5% v/v), FSH (100 mIU/mL), LH (10 mU/mL), and penicillin-streptomycin (penicillin, 100 U/mL; streptomycin, 100 mg/mL) to minimum essential medium alpha (MEM-alpha) and mix in 50 mL tubes. 
	NOTE: Total volumes of required culture media vary between experiments, but 1 mL of culture medium is generally sufficient for 3.5 cm glass-bottom culture dishes.</li>
	<li>Pour 1 mL aliquots of mixed culture medium into 3.5 cm glass-bottom culture dishes and set place 30 mm cell culture inserts into dishes. Pre-warm media and dishes in an incubator (5% CO2 and 37 &#176;C).</li>
</ol>
2. Preparation of Ovarian Tissue
<ol>
	<li>Pre-warm phosphate buffered saline (PBS) (&#8722;) and MEM-alpha containing 5% FBS, 100 U/mL penicillin, and 100 mg/mL streptomycin in an incubator (5% CO2 and 37 &#176;C). 
	&#8203;NOTE: About 3 mL aliquots of PBS (&#8722;) per ovary are sufficient for use during ovary dissections, and 1 mL aliquots of MEM-alpha are sufficient for transient storage of single ovaries in 3.5 cm dishes.</li>
	<li>Excise ovaries from 4-week old female ICR (named after Institute of Cancer Research) mice and trim the tissues surrounding the ovary using scissors and tweezers under a stereoscopic microscope. Reserve the removed ovaries in culture medium (see step 2.1) until use.
	<ol>
		<li>Place single ovaries onto filter paper moistened with pre-warmed PBS (&#8722;) (see step 2.1) and slice into 4 pieces using a microtome blade under a stereoscopic microscope. 
		NOTE: Ovaries of 4-week old ICR mice are about 2 mm in diameter. The number of pieces depends on the ovary size; however, about 500 &#181;m thick pieces allow for proper follicle observations (in pieces thicker than 500 mm, tissue transparency is decreased; in pieces thinner than 500 mm, many antral follicles are broken and lost).</li>
		<li>After dissection, place the sliced ovary specimens into pre-warmed culture medium in 3.5 cm dishes (see step 2.1).</li>
	</ol>
	</li>
</ol>
3. Ovarian Tissue Culture
<ol>
	<li>Drop approximately 0.5 &#181;L of culture medium per sliced ovarian tissue on the cell culture insert where the ovarian tissue will be set using a micropipette.</li>
	<li>Place each sliced specimen into a drop of culture medium on the cell culture inserts using tweezers.</li>
	<li>Culture the ovary tissues in 5% CO2 at 37 &#176;C.</li>
	<li>Replace the culture medium with fresh pre-warmed medium every 2 days. 
	&#8203;NOTE: The schedule for medium changes for the culture of ovary sections from 4-week old ICR mice is presented in Figure 1.
	<ol>
		<li>To reproduce the LH surge, treat cultured 4-week old ICR mice ovaries with the medium containing 100 mU/mL FSH and LH for 12 h every 4 days (Figure 1).</li>
	</ol>
	</li>
</ol>
4. Microscope Images of Cultured Ovaries
<ol>
	<li>Start imaging the cultured ovaries after day 1 when the tissues have adhered onto the cell culture inserts, and perform confocal or inverted microscope analyses at 24 h intervals to allow sufficient follicle growth between time points. 
	NOTE: Confocal microscopy is superior to inverted microscopy for observing follicles in whole cultured ovaries.</li>
</ol>
5. Time-lapse Imaging of Cultured Ovaries
<ol>
	<li>Optimize the time-lapse imaging conditions, including laser intensities and exposure times, for the imaging system (Table 1).
	<ol>
		<li>Select paired ovary specimens from single mice for use as treatment and control groups. Vary laser intensities and exposure time to achieve the best images (Table 1).</li>
		<li>Compare follicle growth under each culture condition by measuring follicle areas in images of control samples at 24 h intervals and in time-lapse imaging samples (see step 6). Concurrently, count the number of ovulated oocytes in each ovary set and choose the optimal time-lapse imaging conditions.</li>
	</ol>
	</li>
	<li>Capture images at 30 min intervals using the time-lapse imaging system under the determined conditions (Table 1).</li>
</ol>
6. Follicle Growth Analysis
<ol>
	<li>To analyze the follicle development, measure the follicle areas in the captured images using ImageJ software (http://resbweb.nih.gov/ij/).
	<ol>
		<li>Initially, set the scale of the image by clicking &#34;Set Scale&#34; under &#34;Analyze&#34; in the tool bar. Enter the side lengths of the captured image and the corresponding numbers of pixels in the blank fields of &#34;Known distance&#34; and &#34;Distance in pixels&#34;, respectively.</li>
		<li>Click &#34;Free hand&#34; in the tool bar and outline the follicles in the captured bright field images.</li>
		<li>Click &#34;Measure&#34; under &#34;Analyze&#34; in the tool bar. 
		NOTE: If other measurement data are desired, click &#34;Set measurement&#34; under &#34;Analyze&#34; in the tool bar, and check the appropriate boxes in the list.</li>
	</ol>
	</li>
</ol>
7. Analysis of Follicle Development Using Transgenic Mice
<ol>
	<li>Collect ovaries from postnatal days 0 and 4 (P0 and P4) female transgenic mice containing the transgenes Oog1pro3.9 and R26-H2B-mCherr, and culture on inserts as described in steps 1.1&#8211;3.2, except do not slice the P0 and P4 ovaries.</li>
	<li>Replace the culture medium with fresh, pre-warmed medium in 3.5 cm dishes in an incubator containing 5% CO2 at 37 &#176;C every 2 days. 
	NOTE: The concentration of LH in the culture medium of P0 and P4 ovaries can remain constant because LH surges do not occur in P0 and P4 mice.</li>
	<li>Set the microscope to visualize only AcGFP1-positive primary follicles in cultured P4 ovaries (Table 1). 
	NOTE: Only primordial and primary follicles are present in P4 female mouse ovaries.</li>
	<li>Capture images of cultured P0 Oog1pro3.9/R26-H2B-mCherry transgenic mice ovaries at 30 min intervals using the settings used for P4 ovaries (see step 5.2).</li>
	<li>Trace and analyze follicle development using AcGFP1 and H2B-mCHerry signals.</li>
</ol>

<ol><li>Myers, M., Britt, K. L., Wreford, N. G., Ebling, F. J., Kerr, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Methods+for+quantifying+follicular+numbers+within+the+mouse+ovary%5BTitle%5D)+AND+%22Reproduction%22%5BJournal%5D)">Methods for quantifying follicular numbers within the mouse ovary.</a> Reproduction. 127 (5), 569-580 (2004).</li>
<li>Adams, G. P., Jaiswal, R., Singh, J., Malhi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Progress+in+understanding+ovarian+follicular+dynamics+in+cattle%5BTitle%5D)+AND+%22Theriogenology%22%5BJournal%5D)">Progress in understanding ovarian follicular dynamics in cattle.</a> Theriogenology. 69 (1), 72-80 (2008).</li>
<li>Palma, G. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biology+and+biotechnology+of+follicle+development%5BTitle%5D)+AND+%22Sci+World+J%22%5BJournal%5D)">Biology and biotechnology of follicle development.</a> Sci World J. , (2012).</li>
<li>Knight, P. G., Glister, C. <a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16885529">TGF-beta superfamily members and ovarian follicle development.</a> Reproduction. 132 (2), 191-206 (2006).</li>
<li>Picton, H. M., Harris, S. E., Muruvi, W., Chambers, E. L. <a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19074213">The in vitro growth and maturation of follicles.</a> Reproduction. 136 (6), 703-715 (2008).</li>
<li>Spears, N., de Bruin, J. P., Gosden, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+establishment+of+follicular+dominance+in+co-cultured+mouse+ovarian+follicles%5BTitle%5D)+AND+%22J+Reprod+Fertil%22%5BJournal%5D)">The establishment of follicular dominance in co-cultured mouse ovarian follicles.</a> J Reprod Fertil. 106 (1), 1-6 (1996).</li>
<li>Baker, S. J., Srsen, V., Lapping, R., Spears, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Combined+effect+of+follicle-follicle+interactions+and+declining+follicle-stimulating+hormone+on+murine+follicle+health+in+vitro%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Combined effect of follicle-follicle interactions and declining follicle-stimulating hormone on murine follicle health in vitro.</a> Biol Reprod. 65 (4), 1304-1310 (2001).</li>
<li>Komatsu, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Analysis+of+the+Effect+of+Leukemia+Inhibitory+Factor+on+Follicular+Growth+in+Cultured+Murine+Ovarian+Tissue%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Analysis of the Effect of Leukemia Inhibitory Factor on Follicular Growth in Cultured Murine Ovarian Tissue.</a> Biol Reprod. 93 (1), 18(2015).</li>
<li>Komatsu, K., Masubuchi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+concentration-dependent+effect+of+progesterone+on+follicle+growth+in+the+mouse+ovary%5BTitle%5D)+AND+%22J+Reprod+Dev%22%5BJournal%5D)">The concentration-dependent effect of progesterone on follicle growth in the mouse ovary.</a> J Reprod Dev. 63 (3), 271-277 (2017).</li>
<li>Murase, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Follicle+dynamics%3A+visualization+and+analysis+of+follicle+growth+and+maturation+using+murine+ovarian+tissue+culture%5BTitle%5D)+AND+%22J+Assist+Reprod+Genet%22%5BJournal%5D)">Follicle dynamics: visualization and analysis of follicle growth and maturation using murine ovarian tissue culture.</a> J Assist Reprod Genet. , 1-5 (2017).</li>
<li>Ishida, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+promoter+of+the+oocyte-specific+gene%2C+Oog1%2C+functions+in+both+male+and+female+meiotic+germ+cells+in+transgenic+mice%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">The promoter of the oocyte-specific gene, Oog1, functions in both male and female meiotic germ cells in transgenic mice.</a> PLoS One. 8 (7), 68686(2013).</li>
<li>Minami, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Oogenesin+is+a+novel+mouse+protein+expressed+in+oocytes+and+early+cleavage-stage+embryos%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Oogenesin is a novel mouse protein expressed in oocytes and early cleavage-stage embryos.</a> Biol Reprod. 69 (5), 1736-1742 (2003).</li>
<li>Nilsson, E. E., Skinner, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Growth+and+differentiation+factor-9+stimulates+progression+of+early+primary+but+not+primordial+rat+ovarian+follicle+development%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Growth and differentiation factor-9 stimulates progression of early primary but not primordial rat ovarian follicle development.</a> Biol Reprod. 67 (3), 1018-1024 (2002).</li>
<li>Nilsson, E. E., Kezele, P., Skinner, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Leukemia+inhibitory+factor+%28LIF%29+promotes+the+primordial+to+primary+follicle+transition+in+rat+ovaries%5BTitle%5D)+AND+%22Mol+Cell+Endocrinol%22%5BJournal%5D)">Leukemia inhibitory factor (LIF) promotes the primordial to primary follicle transition in rat ovaries.</a> Mol Cell Endocrinol. 188 (1-2), 65-73 (2002).</li>
<li>Nilsson, E. E., Skinner, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bone+morphogenetic+protein-4+acts+as+an+ovarian+follicle+survival+factor+and+promotes+primordial+follicle+development%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Bone morphogenetic protein-4 acts as an ovarian follicle survival factor and promotes primordial follicle development.</a> Biol Reprod. 69 (4), 1265-1272 (2003).</li>
<li>Nilsson, E. E., Skinner, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Kit+ligand+and+basic+fibroblast+growth+factor+interactions+in+the+induction+of+ovarian+primordial+to+primary+follicle+transition%5BTitle%5D)+AND+%22Mol+Cell+Endocrinol%22%5BJournal%5D)">Kit ligand and basic fibroblast growth factor interactions in the induction of ovarian primordial to primary follicle transition.</a> Mol Cell Endocrinol. 214 (1-2), 19-25 (2004).</li>
<li>Abe, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Establishment+of+conditional+reporter+mouse+lines+at+ROSA26+locus+for+live+cell+imaging%5BTitle%5D)+AND+%22Genesis%22%5BJournal%5D)">Establishment of conditional reporter mouse lines at ROSA26 locus for live cell imaging.</a> Genesis. 49 (7), 579-590 (2011).</li>
<li>Lan, Z. J., Xu, X., Cooney, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Differential+oocyte-specific+expression+of+Cre+recombinase+activity+in+GDF-9-iCre%2C+Zp3cre%2C+and+Msx2Cre+transgenic+mice%5BTitle%5D)+AND+%22Biol+Reprod%22%5BJournal%5D)">Differential oocyte-specific expression of Cre recombinase activity in GDF-9-iCre, Zp3cre, and Msx2Cre transgenic mice.</a> Biol Reprod. 71 (5), 1469-1474 (2004).</li>
<li>Payer, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Generation+of+stella-GFP+transgenic+mice%3A+a+novel+tool+to+study+germ+cell+development%5BTitle%5D)+AND+%22Genesis%22%5BJournal%5D)">Generation of stella-GFP transgenic mice: a novel tool to study germ cell development.</a> Genesis. 44 (2), 75-83 (2006).</li>
<li>Ohinata, Y., Sano, M., Shigeta, M., Yamanaka, K., Saitou, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+comprehensive%2C+non-invasive+visualization+of+primordial+germ+cell+development+in+mice+by+the+Prdm1-mVenus+and+Dppa3-ECFP+double+transgenic+reporter%5BTitle%5D)+AND+%22Reproduction%22%5BJournal%5D)">A comprehensive, non-invasive visualization of primordial germ cell development in mice by the Prdm1-mVenus and Dppa3-ECFP double transgenic reporter.</a> Reproduction. 136 (4), 503-514 (2008).</li>
</ol>

The authors have nothing to disclose.

In this study, we developed two new methods for studying follicle development in mouse ovaries. The first method involves culture of sliced ovarian adult mice tissues followed by analyses of follicle development, and the second involves the use of time-lapse imaging to visualize early follicle development during the gonadotropin-independent stage. Previously, we used the present ovary tissue culture method to assess the effect of leukemia inhibitory factor and progesterone on follicle development8...

Female mouse ovaries contain several thousand follicles1, and periodic ovulation matures approximately ten oocytes at each estrus cycle. Follicles are classified into several developmental stages: primordial, primary, secondary, antral, and Graafian follicles, depending on the form of the granulosa cellular layer surrounding each oocyte. Most primordial follicles are dormant, and some of them are activated and grow into primary follicles at each estrus cycle2. After the secondary follicular stage, follicle development is mainly regulated by gonadotropins, follicular stimulating hormone (FSH), and luteinizing hormone (LH). However, primordial and primary follicle development is independent of gonadotropin, and the regulatory mechanisms that govern these stages remain poorly inderstood3,4,5. In addition to growth factors and hormones, the primordial and primary follicle is regulated by the interactions among follicles6,7. Therefore, we performed analyses of follicle dynamics in mouse ovary tissues, and investigated the associated regulatory mechanisms using ovarian tissue cultures8,9,10.
Herein, we introduce two ovarian tissue culture model methods. The first is used to analyze follicle development by measurement of follicular areas, and the second is used to study the regulatory mechanism during early follicle development from primordial to secondary follicle stage with transgenic mice. For follicle development analysis, we mainly used ovaries of 4-week old female mice because they allow for easy visualization of follicles. To induce periodical ovulation and model in vivo follicle development, we reproduced LH surge and observed ovulation, follicle atresia, and secretion of estradiol under tissue culture conditions. Images of the cultured ovaries were captured, and the follicle development processes were analyzed by tracing changes in the follicular area. However, in bright field microscopy analyses, the distinction between primordial and early primary follicles was unclear. Thus, we developed a method to detect small follicles, and distinguish between the primordial, primary, and secondary follicle in cultured ovarian tissues using Oogenesin1 (Oog1) pro3.9 and R26-H2B-mCherry transgenic mice ovaries at days 0 and 4 after birth11. Oog1 expression is detectable in oocytes after entry into meiosis, and gradually increases with follicle development, allowing observation of the transition from primordial to primary follicles using time-lapse images of cultured ovary tissue11,12. Although morphological methods have been used to study factors that activate dormant primordial follicles13,14,15,16, physiological follicle development in ovaries is difficult to observe, and the effects of various factors remain uncharacterized. The present culture methods were designed to address this paucity in real time analyses of target factors.
In the present study, we tracked follicular development using a time-lapse imaging method and characterized the process of follicle development. Our novel methods offer an unprecedented tool for investigating the physiology of ovaries.

<table><tbody><tr><td>Follicle stimulating hormone from human pituitary</td><td>SIGMA</td><td>F4021</td><td></td></tr><tr><td>Lutenizing hormone from equine pituitary</td><td>SIGMA</td><td>L9773</td><td></td></tr><tr><td>Penicillin-streptomycin solution</td><td>Wako Pure Chemical Industries</td><td>168-23191</td><td></td></tr><tr><td>MEM a, GlutaMax, no nucleotides</td><td>Thermo Fisher</td><td>32561037</td><td></td></tr><tr><td>Glass bottom dish</td><td>MatTek</td><td>P35G-0-10-C</td><td>35mm dish, No. 0 coverslip, 10mm glass diameter</td></tr><tr><td>Millicell cell culture insert</td><td>Merck Millipore</td><td>PICM0RG50</td><td>Diameter: 315 mm, pore size: 0.4 mm, material: hydrophilic PTTE</td></tr><tr><td>3.5cm cell culture dishes</td><td>greiner bio-one</td><td>627160</td><td></td></tr><tr><td>50ml / centrifuge tube with triple seal cap</td><td>IWAKI</td><td>2345-050</td><td></td></tr><tr><td>Low-profile disposable blades 819</td><td>Leica</td><td>14035838925</td><td></td></tr><tr><td>LSM 710</td><td>Carl Zeiss</td><td></td><td>Confocal microscope</td></tr><tr><td>CellVoyager, CV1000</td><td>Yokogawa Electric Corporation</td><td></td><td>Time-lapse imaging</td></tr><tr><td>BZ-X700</td><td>KEYENCE</td><td></td><td>Time-lapse imaging</td></tr></tbody></table>

ovarian tissue culture to visualize phenomena in mouse ovary

Mammalian females periodically ovulate an almost constant number of oocytes during each estrus cycle. To sustain such regularity and periodicity, regulation occurs at the hypothalamic-pituitary-gonadal axis level and on developing follicles in the ovary. Despite active studies, follicle development mechanisms are not clear because of the several steps involved from the dormant primordial follicle activation to ovulation, and because of the regulation complexity that differs at each follicular stage. To investigate the mechanisms of follicle development, and the dynamics of follicles throughout the estrus cycle, we developed a mouse ovarian tissue culture model that can be used to observe follicle development using a microscope. Systematic follicle development, periodical ovulation, and follicle atresia can all be reproduced in the cultured ovary model, and the culture conditions can be experimentally modulated. Here, we demonstrate the usefulness of this method in the study of the regulatory mechanisms of follicle development and other ovarian phenomena.

Figure 1&#160;shows the protocol for changes in media during ovarian tissue culture. Following this program, 4-week-old ICR mice ovaries were cultured and imaged at 24-h intervals using confocal microscopy (Figure 2). During culture of ovary tissues for 3 weeks, most antral and secondary follicles were degenerated by follicle atresia and some were ovulated (Figure 2D and Tabl...

Watch this Scientific Journal Video about Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary at JoVE.com

Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary

Ovarian tissue cultures can be used as models of follicle development, ovulation, and follicle atresia and indicate regulatory mechanisms of dynamic ovarian processes.

Mammalian females periodically ovulate an almost constant number of oocytes during each estrus cycle. To sustain such regularity and periodicity, ...

ovarian-tissue-culture-to-visualize-phenomena-in-mouse-ovary

Research

JoVE Journal

Developmental Biology

13.7K Views.  Aichi Medical University. Ovarian tissue cultures can be used as models of follicle development, ovulation, and follicle atresia and indicate regulatory mechanisms of dynamic ovarian processes.

Video: Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary

Culture and Co-Culture of Mouse Ovaries and Ovarian Follicles

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together within a basement membrane. A finite pool of follicles is laid down during embryonic development, when oocytes in meiotic arrest form a close association with flattened granulosa cells, forming primordial follicles. By or shortly after birth, mammalian ovaries contain their lifetime&#8217;s supply of primordial follicles, from which point onwards there is a steady release of follicles into the growing follicular pool.
The ovary is particularly amenable to development in vitro, with follicles growing in a highly physiological manner in culture. This work describes the culture of whole neonatal ovaries containing primordial follicles, and the culture of individual ovarian follicles, a method which can support the development of follicles from an immature through to the preovulatory stage, after which their oocytes are able to undergo fertilization in vitro. The work outlined here uses culture systems to determine how the ovary is affected by exposure to external compounds. We also describe a co-culture system, which allows investigation of the interactions that occur between growing follicles and the non-growing pool of primordial follicles.

This protocol describes the primary culture/co-culture of mouse ovarian tissue, using ovaries from neonatal mice and individual ovarian follicles from prepubertal mice. The culture techniques support development in a highly physiological manner, allowing investigation of the effect of extrinsic agents on the ovary, and of interactions between ovarian follicles.

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together ...

An Orthotopic Model of Serous Ovarian Cancer in Immunocompetent Mice for in vivo Tumor Imaging and Monitoring of Tumor Immune Responses

Background: Ovarian cancer is generally diagnosed at an advanced stage where the case/fatality ratio is high and thus remains the most lethal of all gynecologic malignancies among US women 1,2,3. Serous tumors are the most widespread forms of ovarian cancer and 4,5 the Tg-MISIIR-TAg transgenic represents the only mouse model that spontaneously develops this type of tumors. Tg-MISIIR-TAg mice express SV40 transforming region under control of the Mullerian Inhibitory Substance type II Receptor (MISIIR) gene promoter 6. Additional transgenic lines have been identified that express the SV40 TAg transgene, but do not develop ovarian tumors. Non-tumor prone mice exhibit typical lifespan for C57Bl/6 mice and are fertile. These mice can be used as syngeneic allograft recipients for tumor cells isolated from Tg-MISIIR-TAg-DR26 mice.
Objective: Although tumor imaging is possible 7, early detection of deep tumors is challenging in small living animals. To enable preclinical studies in an immunologically intact animal model for serous ovarian cancer, we describe a syngeneic mouse model for this type of ovarian cancer that permits in vivo imaging, studies of the tumor microenvironment and tumor immune responses.
Methods: We first derived a TAg+ mouse cancer cell line (MOV1) from a spontaneous ovarian tumor harvested in a 26 week-old DR26 Tg-MISIIR-TAg female. Then, we stably transduced MOV1 cells with TurboFP635 Lentivirus mammalian vector that encodes Katushka, a far-red mutant of the red fluorescent protein from sea anemone Entacmaea quadricolor with excitation/emission maxima at 588/635 nm 8,9,10. We orthotopically implanted MOV1Kat in the ovary 11,12,13,14 of non-tumor prone Tg-MISIIR-TAg female mice. Tumor progression was followed by in vivo optical imaging and tumor microenvironment was analyzed by immunohistochemistry.
Results: Orthotopically implanted MOV1Kat cells developed serous ovarian tumors. MOV1Kat tumors could be visualized by in vivo imaging up to three weeks after implantation (fig. 1) and were infiltrated with leukocytes, as observed in human ovarian cancers 15 (fig. 2).
Conclusions: We describe an orthotopic model of ovarian cancer suitable for in vivo imaging of early tumors due to the high pH-stability and photostability of Katushka in deep tissues. We propose the use of this novel syngeneic model of serous ovarian cancer for in vivo imaging studies and monitoring of tumor immune responses and immunotherapies.

An Orthotopic Model of Serous Ovarian Cancer in Immunocompetent Mice for in vivo Tumor Imaging and Monitoring of Tumor Immune Responses

To study in vivo tumor growth and tumor microenvironment, we used a syngeneic and orthotopic mouse model of ovarian cancer in immunocompetent animals. We transduced a mouse tumor cell line (MOV1) with Katushka fluorescent protein (MOV1KAT) and here we show its orthotopic implantation in ovary and in vivo imaging.

Background: Ovarian cancer is generally diagnosed at an advanced stage where the case/fatality ratio is high and thus remains the most lethal of all ...

Immunology and Infection

Alginate Hydrogels for Three-Dimensional Organ Culture of Ovaries and Oviducts

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ovarian cancers is still in question and might be either the ovarian surface epithelium (OSE) or the distal epithelium of the fallopian tube fimbriae2,3. Culturing the normal cells as a primary culture in vitro will enable scientists to model specific changes that might lead to ovarian cancer in the distinct epithelium, thereby definitively determining the cell type of origin. This will allow development of more accurate biomarkers, animal models with tissue-specific gene changes, and better prevention strategies targeted to this disease.
Maintaining normal cells in alginate hydrogels promotes short term in vitro culture of cells in their three-dimensional context and permits introduction of plasmid DNA, siRNA, and small molecules. By culturing organs in pieces that are derived from strategic cuts using a scalpel, several cultures from a single organ can be generated, increasing the number of experiments from a single animal. These cuts model aspects of ovulation leading to proliferation of the OSE, which is associated with ovarian cancer formation. Cell types such as the OSE that do not grow well on plastic surfaces can be cultured using this method and facilitate investigation into normal cellular processes or the earliest events in cancer formation4.
Alginate hydrogels can be used to support the growth of many types of tissues5. Alginate is a linear polysaccharide composed of repeating units of &beta;-D-mannuronic acid and &alpha;-L-guluronic acid that can be crosslinked with calcium ions, resulting in a gentle gelling action that does not damage tissues6,7. Like other three-dimensional cell culture matrices such as Matrigel, alginate provides mechanical support for tissues; however, proteins are not reactive with the alginate matrix, and therefore alginate functions as a synthetic extracellular matrix that does not initiate cell signaling5. The alginate hydrogel floats in standard cell culture medium and supports the architecture of the tissue growth in vitro.
A method is presented for the preparation, separation, and embedding of ovarian and oviductal organ pieces into alginate hydrogels, which can be maintained in culture for up to two weeks. The enzymatic release of cells for analysis of proteins and RNA samples from the organ culture is also described. Finally, the growth of primary cell types is possible without genetic immortalization from mice and permits investigators to use knockout and transgenic mice.

Culture of normal cells in their three-dimensional context represents an alternative method to study early events required for cellular transformation and tumorigenesis. This method is used to grow normal ovarian and oviductal cells to study early events in ovarian cancer formation.

Ovarian cancer is the fifth leading cause of cancer deaths in women and has a 63% mortality rate in the United States1. The cell type of origin for ...

Bioengineering

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical and molecular methods provides information of potential target genes and signaling pathways. To further elucidate specific regulatory mechanisms requires a system allowing the manipulation of only a small number of cells of a specific tissue by either overexpression, ablation or re-introduction of specific genes and follow their fate during development. To achieve this ex utero electroporation of hippocampal structures, especially the dentate gyrus, followed by organotypic slice culture provides such a tool. Using this system to generate mosaic deletions allows determining whether the gene of interest regulates cell-autonomously developmental processes like progenitor cell proliferation or neuronal differentiation. Furthermore it facilitates the rescue of phenotypes by re-introducing the deleted gene or its target genes. In contrast to in utero electroporation the ex utero approach improves the rate of successfully targeting deeper layers of the brain like the dentate gyrus. Overall ex utero electroporation and organotypic slice culture provide a potent tool to study regulatory mechanisms in a semi-native environment mirroring endogenous conditions.

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Here we present a protocol providing a tool to examine regulatory mechanisms of specific genes during hippocampal development. Employing ex utero electroporation and organotypic slice culture allows the up- and down-regulation of the expression of genes of interest in single cells and follow their fate during development.

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical ...

A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes

Infertility clinics would benefit from the ability to select developmentally competent vs. incompetent oocytes using non-invasive procedures, thus improving the overall pregnancy outcome. We recently developed a classification method based on microscopic live observations of mouse oocytes during their in vitro maturation from the germinal vesicle (GV) to the metaphase II stage, followed by the analysis of the cytoplasmic movements occurring during this time-lapse period. Here, we present detailed protocols of this procedure. Oocytes are isolated from fully-grown antral follicles and cultured for 15 h inside a microscope equipped for time-lapse analysis at 37 &#176;C and 5% CO2. Pictures are taken at 8 min intervals. The images are analyzed using the Particle Image Velocimetry (PIV) method that calculates, for each oocyte, the profile of Cytoplasmic Movement Velocities (CMVs) occurring throughout the culture period. Finally, the CMVs of each single oocyte are fed through a mathematical classification tool (Feed-forward Artificial Neural Network, FANN), which predicts the probability of a gamete to be developmentally competent or incompetent with an accuracy of 91.03%. This protocol, set up for the mouse, could now be tested on oocytes of other species, including humans.

Here, we present a protocol for non-invasive assessment of oocyte developmental competence performed during their in vitro maturation from the germinal vesicle to the metaphase II stage. This method combines time-lapse imaging with particle image velocimetry (PIV) and neural network analyses.

Infertility clinics would benefit from the ability to select developmentally competent vs. incompetent oocytes using non-invasive procedures, thus ...

Whole Mount Immunofluorescence and Follicle Quantification of Cultured Mouse Ovaries

Research in the field of mammalian reproductive biology often involves evaluating the overall health of ovaries and testes. Specifically, in females, ovarian fitness is often assessed by visualizing and quantifying follicles and oocytes. Because the ovary is an opaque three-dimensional tissue, traditional approaches require laboriously slicing the tissue into numerous serial sections in order to visualize cells throughout the entire organ. Furthermore, because quantification by this method typically entails scoring only a subset of the sections separated by the approximate diameter of an oocyte, it is prone to inaccuracy. Here, a protocol is described that instead utilizes whole organ tissue clearing and immunofluorescence staining of mouse ovaries to visualize follicles and oocytes. Compared to more traditional approaches, this protocol is advantageous for visualizing cells within the ovary for numerous reasons: 1) the ovary remains intact throughout sample preparation and processing; 2) small ovaries, which are difficult to section, can be examined with ease; 3) cellular quantification is more readily and accurately achieved; and 4) the whole organ imaged.

Here, we present a protocol to quantify follicles in cultured ovaries of young mice without serial sectioning. Using whole organ immunofluorescence and tissue clearing, physical sectioning is replaced with optical sectioning. This method of sample preparation and visualization maintains organ integrity and facilitates automated quantification of specific cells.

Research in the field of mammalian reproductive biology often involves evaluating the overall health of ovaries and testes. Specifically, in females, ...

Accurate Follicle Enumeration in Adult Mouse Ovaries

Sexually reproducing female mammals are born with their entire lifetime supply of oocytes. Immature, quiescent oocytes are found within primordial follicles, the storage unit of the female germline. They are non-renewable, thus their number at birth and subsequent rate of loss largely dictates the female fertile lifespan. Accurate quantification of primordial follicle numbers in women and animals is essential for determining the impact of medicines and toxicants on the ovarian reserve. It is also necessary for evaluating the need for, and success of, existing and emerging fertility preservation techniques. Currently, no methods exist to accurately measure the number of primordial follicles comprising the ovarian reserve in women. Furthermore, obtaining ovarian tissue from large animals or endangered species for experimentation is often not feasible. Thus, mice have become an essential model for such studies, and the ability to evaluate primordial follicle numbers in whole mouse ovaries is a critical tool. However, reports of absolute follicle numbers in mouse ovaries in the literature are highly variable, making it difficult to compare and/or replicate data. This is due to a number of factors including strain, age, treatment groups, as well as technical differences in the methods of counting employed. In this article, we provide a step-by-step instructional guide for preparing histological sections and counting primordial follicles in mouse ovaries using two different methods: [1] stereology, which relies on the fractionator/optical dissector technique; and [2] the direct count technique. Some of the key advantages and drawbacks of each method will be highlighted so that reproducibility can be improved in the field and to enable researchers to select the most appropriate method for their studies.

Here, we describe, compare, and contrast two different techniques for accurate follicle counting of fixed mouse ovarian tissues.

Sexually reproducing female mammals are born with their entire lifetime supply of oocytes. Immature, quiescent oocytes are found within primordial ...

Whole Ovary Immunofluorescence, Clearing, and Multiphoton Microscopy for Quantitative 3D Analysis of the Developing Ovarian Reserve in Mouse

Female fertility and reproductive lifespan depend on the quality and quantity of the ovarian oocyte reserve. An estimated 80% of female germ cells entering meiotic prophase I are eliminated during Fetal Oocyte Attrition (FOA) and the first week of postnatal life. Three major mechanisms regulate the number of oocytes that survive during development and establish the ovarian reserve in females entering puberty. In the first wave of oocyte loss, 30-50% of the oocytes are eliminated during early FOA, a phenomenon that is attributed to high Long interspersed nuclear element-1 (LINE-1) expression. The second wave of oocyte loss is the elimination of oocytes with meiotic defects by a meiotic quality checkpoint. The third wave of oocyte loss occurs perinatally during primordial follicle formation when some oocytes fail to form follicles. It remains unclear what regulates each of these three waves of oocyte loss and how they shape the ovarian reserve in either mice or humans.
Immunofluorescence and 3D visualization have opened a new avenue to image and analyze oocyte development in the context of the whole ovary rather than in less informative 2D sections. This article provides a comprehensive protocol for whole ovary immunostaining and optical clearing, yielding preparations for imaging using multiphoton microscopy and 3D modeling using commercially available software. It shows how this method can be used to show the dynamics of oocyte attrition during ovarian development in C57BL/6J mice and quantify oocyte loss during the three waves of oocyte elimination. This protocol can be applied to prenatal and early postnatal ovaries for oocyte visualization and quantification, as well as other quantitative approaches. Importantly, the protocol was strategically developed to accommodate high-throughput, reliable, and repeatable processing that can meet the needs in toxicology, clinical diagnostics, and genomic assays of ovarian function.

Here, we present an optimized protocol for imaging entire ovaries for quantitative and qualitative analyses using whole-mount immunostaining, multiphoton microscopy, and 3D visualization and analysis. This protocol accommodates high-throughput, reliable, and repeatable processing that is applicable for toxicology, clinical diagnostics, and genomic assays of ovarian function.

Female fertility and reproductive lifespan depend on the quality and quantity of the ovarian oocyte reserve. An estimated 80% of female germ cells ...

Three-dimensional Reconstruction of the Vascular Architecture of the Passive CLARITY-cleared Mouse Ovary

The ovary is the main organ of the female reproductive system and is essential for the production of female gametes and for controlling the endocrine system, but the complex structural relationships and three-dimensional (3D) vasculature architectures of the ovary are not well described. In order to visualize the 3D connections and architecture of blood vessels in the intact ovary, the first important step is to make the ovary optically clear. In order to avoid tissue shrinkage, we used the hydrogel fixation-based passive CLARITY (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging/ Immunostaining/In situ-hybridization-compatible Tissue Hydrogel) protocol method to clear an intact ovary. Immunostaining, advanced multiphoton confocal microscopy, and 3D image-reconstructions were then used for the visualization of ovarian vessels and follicular capillaries. Using this approach, we showed a significant positive correlation (P &#60;0.01) between the length of the follicular capillaries and volume of the follicular wall.

Here we present an adaptation of the passive CLARITY and 3D reconstruction method for visualization of the ovarian vasculature and follicular capillaries in intact mouse ovaries.

The ovary is the main organ of the female reproductive system and is essential for the production of female gametes and for controlling the endocrine ...

Biology

Orthotopic Inoculation of Ovarian Cancer Cells into Murine Ovary: A Procedure to Establish an Ovarian Cancer Mouse Model to Study Peritoneal Dissemination of Cells

To carry out orthotopic inoculation, after anesthetizing an eight-week-old female nude mouse according to the text protocol, perform a toe pinch to verify depth of the anesthesia. Place the anesthetized mouse on an operating stage, belly side down. Then, disinfect the surgical area with several washes using a chlorhexidine-based scrub and alcohol.
Next, make an approximately 2-centimeter vertical incision near the spine, between the right costal arch and the femur. Place a sterile surgical drape around the incision site. Then, fix the incised skin surfaces with clamps to maintain the opening.
Now, make a second 1-centimeter incision at the parietal peritoneum under the first incision to open the abdominal cavity. Then, clamp the incised abdominal surfaces. With a clamp, clip the fat tissue that surrounds the ipsilateral ovary and fallopian tube to remove the ovary from the abdominal cavity.
Then, carefully place the ovary and fallopian tube on gauze before placing the mouse, belly side down, under the dissecting microscope. Transfer the cell suspension to an insulin syringe. Then, immediately and carefully inject 1 to 2 microliters of the prepared cell suspension into the ovary.
For several seconds, keep the needle in the ovary to ensure that the hydrogel sets. After gelation, the injected tumor cells will remain in the ovary. Carefully, return the ovary into the body. With sterile medical silk, suture the second incision before using wound clips to seal the skin.

Ortotopowa inokulacja komórek raka jajnika do mysiego jajnika: procedura mająca na celu stworzenie mysiego modelu raka jajnika do badania rozsiewu komórek w otrzewnie

Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary

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Culture and Co-Culture of Mouse Ovaries and Ovarian Follicles

An Orthotopic Model of Serous Ovarian Cancer in Immunocompetent Mice for in vivo Tumor Imaging and Monitoring of Tumor Immune Responses

Alginate Hydrogels for Three-Dimensional Organ Culture of Ovaries and Oviducts

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes

Whole Mount Immunofluorescence and Follicle Quantification of Cultured Mouse Ovaries

Accurate Follicle Enumeration in Adult Mouse Ovaries

Whole Ovary Immunofluorescence, Clearing, and Multiphoton Microscopy for Quantitative 3D Analysis of the Developing Ovarian Reserve in Mouse

Three-dimensional Reconstruction of the Vascular Architecture of the Passive CLARITY-cleared Mouse Ovary

Ortotopowa inokulacja komórek raka jajnika do mysiego jajnika: procedura mająca na celu stworzenie mysiego modelu raka jajnika do badania rozsiewu komórek w otrzewnie