This work was made possible thanks to support by: University of Pavia FRG 2016; University of Parma FIL 2014, 2016; and Kinesis for supplying the plasticware necessary to carry out this study. We thank Dr. Shane Windsor (Faculty of Engineering, University of Bristol, UK) for providing the Cell_PIV software.

All procedures involving animals were approved by the Institutional Animal Care and Use and Ethical Committees at University of Pavia. Animals were maintained under conditions of 22 &#176;C, 60% air humidity and a light/dark cycle of 12:12 h.
1.Ovary Isolation
<ol>
	<li>Inject intraperitoneally 2 four-to-eleven week-old CD1 female mice with 10 U of follicle stimulating hormone with a sterile 1 mL insulin syringe.</li>
	<li>Wait 46-48 h.</li>
	<li>Weigh the mouse and anesthetize with an intramuscular injection of 50 mg/kg of Zoletil (Tiletamina and Zolazepan cloridrate). Euthanize by cervical dislocation.</li>
	<li>Grasp the skin covering the abdominal wall using a pair of dissection forceps. Cut the skin and body wall with a pair of scissors and pull open the incision with forceps.</li>
	<li>Using a pair of tweezers, move the guts aside, pinpoint the uterine horns and localize the ovaries at their extremity.</li>
	<li>Gently hold the ovary using watchmaker forceps and use scissors to cut its ligament to the uterus. Repeat with the other ovary.</li>
	<li>Transfer the collected ovaries into a 35-mm cell culture Petri dish containing 1 mL of M2 isolation medium pre-warmed at 37 &#176;C, 5% CO2 in air.</li>
	<li>Remove the fat and the oviduct using fine scissors under a stereomicroscope.</li>
</ol>
2. Isolation of Cumulus Oocyte Complexes
<ol>
	<li>Puncture the ovarian surface using sterile tweezers and a 1G sterile insulin needle until antral cumulus oocyte complexes (COCs) are passively released.</li>
	<li>Collect COCs with more than three layers of cumulus cells using a mouth-controlled hand-pulled Pasteur micropipette (200 &#181;m in diameter) and transfer them into a 300 &#181;L drop of fresh M2 medium.</li>
	<li>Remove the cumulus cells surrounding the oocytes using a hand-pulled Pasteur micropipette (80 &#181;m in diameter) by gently pipetting in and out for few seconds,</li>
	<li>Repeatedly transfer oocytes from a 20 &#181;L drop of M2 medium to another one, until cumulus cells are completely eliminated.</li>
</ol>
3. Chromatin Organization-Based Oocyte Classification
<ol>
	<li>Prepare Hoechst 33342 staining solution at a final concentration of 0.05 &#181;g/mL in M2 medium starting from a mother solution of 5 mg/mL diluted in 1x PBS.</li>
	<li>Place 3.5 &#181;L micro droplets of Hoechst staining solution at the bottom of a 35 mm Petri dish lid.</li>
	<li>Transfer each single oocyte into a Hoechst staining drop, place the dish onto a pre-warmed (37 &#176;C) heating plate and cover it with a dark lid to avoid light exposition.</li>
	<li>After 10 min of incubation at room temperature, observe the oocytes with a fluorescence microscope at 10X magnification under UV light (330-385 nm), for no more than 1-2 s.</li>
	<li>Classify oocytes as a surrounded nucleolus (SN) (Figure 1A), if they present a ring of Hoechst-positive chromatin surrounding the nucleolus.</li>
	<li>Classify oocytes as a not surrounded nucleolus (NSN), if their nucleolus is not surrounded by Hoechst-positive chromatin and shows disperse heterochromatic spots within the nucleus (Figure 1B).</li>
</ol>
4. Neural Network-Based Oocyte Classification
<ol>
	<li>Prepare four 2 &#181;L droplets of &#945;-MEM medium supplemented with 5% heat-inactivated fetal bovine serum, 2 mM L-glutamine, 5 mM taurine, 100 U/mL penicillin, 75 &#181;g/mL streptomycin and 23.5 &#181;g/&#181;L sodium pyruvate into a 35-mm glass bottom Petri dish and cover them with pre-warmed (37 &#176;C) and pre-equilibrated mineral oil to avoid medium evaporation. 
	NOTE: If using a live cell-screening system, keep the drops at a specific distance by using a drawn grid of 7 mm x 7 mm as a guideline.</li>
	<li>Transfer 3- 4 oocytes to each drop.</li>
	<li>Place the glass bottom Petri dish into a live cell-screening system, equipped with time-lapse recording software (see Table of Materials), which allows the observation of oocyte maturation in an environment with stable temperature (37 &#176;C) and CO2 concentration (5%).</li>
	<li>Open the time-lapse recording software. On the screen a window appears with a live shot of the oocyte on the left-hand side and all the setting buttons on the right-hand side.</li>
	<li>Select the center of the oocyte to position it at the screen center. Adjust focus if necessary.</li>
	<li>Select the Ph button and set the DIA Lamp to 192; the Exposure time to 1/125 s; the Gain to 1.99; and the Resolution to 1600 x 1200.</li>
	<li>Select FL2 and set the DIA Lamp to 5; the Exposure time to 3 s; the Gain to 2.37; and the Resolution to 1600 x 1200.</li>
	<li>Select the New point button in order to record the oocyte position within the culture drop. Repeat the same routine for each oocyte within the culture drop.</li>
	<li>Select Time and set the Acquisition cycle to 8 min and the Total time to 15 h.</li>
	<li>Select Start time-lapse to start the recording cycle.</li>
	<li>Open the MATLAB software and write &#62;&#62;cell_piv; and then select the PIV Tool.</li>
	<li>Choose the folder containing the recorded movie and select any of the .jpeg files to load the whole image sequence. For each oocyte, select the region of interest (ROI) by clicking the Select area tool.</li>
	<li>Select Process PIV in the File menu. Select the Viewer Tool button. 
	NOTE: The program will calculate the velocity vectors within the ROI and automatically produces a data file, saved as a .mat file.</li>
	<li>Select the .mat file to open. Select the button Select ROI tool and draw a circle around the outline of the oocyte. Click Save under the File menu. 
	NOTE: The vectors in this region are now displayed and the mean magnitude data in the graph window updated for this new ROI.</li>
	<li>Open the collected mean magnitude data of the whole time-lapse frames recorded into a spreadsheet, with, on the rows, the frame sequence and, on the columns, each single oocyte analyzed.</li>
	<li>Organize the data of both NSN and SN oocytes into 10 subgroups.</li>
	<li>Use 9 subgroups to train the feed-forward artificial neural network iteratively (FANN) and 1 subgroup for blind testing.
	<ol>
		<li>Repeat another 9 times, changing the blind testing sample (10-fold cross-validation).</li>
	</ol>
	</li>
	<li>Open MATLAB, run the custom-made script main and, upon request, insert the name of the file with the training data (train.txt), the number of NSN and SN oocytes used for training and the time-lapse interval to be analyzed (typically, from frame # 1-2 to frame # 112-113).</li>
	<li>Press enter to perform the training.</li>
	<li>Insert the name of the file with the testing data (test.txt).</li>
	<li>Open the vector test_outputs_cyt in MATLAB workspace. 
	NOTE: A window appears on the screen showing, in the first row, the probability to obtain True Positives (TP or True NSN) and False Positives (FP or False NSN) for NSN and SN oocytes, respectively; instead, in the second row, the probability to obtain False Negatives (FN or False SN) and True Negatives (TN or True SN) for NSN and SN oocytes, respectively.</li>
	<li>Use the formula: (TP+TN)/(TP+FP+FN+TN), to calculate the FANN accuracy, expressed as a percentage.</li>
</ol>

<ol>
	<li>Patrizio, P., Fragouli, E., Bianchi, V., Borini, A., Wells, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+methods+for+selection+of+the+ideal+oocyte.">Molecular methods for selection of the ideal oocyte.</a> Reprod. Biomed. Online. 15 (3), 346-353 (2007).</li><li>Rienzi, L., Vajta, G., Ubaldi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predictive+value+of+oocyte+morphology+in+human+IVF:+a+systematic+review+of+the+literature.">Predictive value of oocyte morphology in human IVF: a systematic review of the literature.</a> Human. Reprod. Update. 17 (1), 34-35 (2011).</li><li>Tan, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+configurations+in+the+germinal+vesicle+of+mammalian+oocytes.">Chromatin configurations in the germinal vesicle of mammalian oocytes.</a> Mol. Hum. Reprod. 15 (1), 1-9 (2009).</li><li>Vigone, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptome+based+identification+of+mouse+cumulus+cell+markers+that+predict+the+developmental+competence+of+their+enclosed+antral+oocytes.">Transcriptome based identification of mouse cumulus cell markers that predict the developmental competence of their enclosed antral oocytes.</a> BMC Genomics. 14, 380 (2013).</li><li>Bui, T. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytoplasmic+movement+profiles+of+mouse+surrounding+nucleolus+and+not-surrounding+nucleolus+antral+oocytes+during+meiotic+resumption.">Cytoplasmic movement profiles of mouse surrounding nucleolus and not-surrounding nucleolus antral oocytes during meiotic resumption.</a> Mol. Reprod. Dev. 84 (5), 356-362 (2017).</li><li>Zuccotti, M., Piccinelli, A., Giorgi Rossi, P., Garagna, S., Redi, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+organization+during+mouse+oocyte+growth.">Chromatin organization during mouse oocyte growth.</a> Mol. Reprod. Dev. 41 (4), 479-485 (1995).</li><li>Zuccotti, M., Garagna, S., Merico, V., Monti, M., Redi, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatin+organisation+and+nuclear+architecture+in+growing+mouse+oocytes.">Chromatin organisation and nuclear architecture in growing mouse oocytes.</a> Mol. Cell. Endocrinol. 234 (1-2), 11-17 (2005).</li><li>Zuccotti, M., Merico, V., Cecconi, S., Redi, C. A., Garagna, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+does+it+take+to+make+a+developmentally+competent+mammalian+egg?.">What does it take to make a developmentally competent mammalian egg?.</a> Hum. Reprod. Update. 17 (4), 525-540 (2011).</li><li>Inoue, A., Nakajima, R., Nagata, M., Aoki, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contribution+of+the+oocyte+nucleus+and+cytoplasm+to+the+determination+of+meiotic+and+developmental+competence+in+mice.">Contribution of the oocyte nucleus and cytoplasm to the determination of meiotic and developmental competence in mice.</a> Hum. Reprod. 23 (6), 1377-1384 (2008).</li><li>Ajduk, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rhythmic+actomyosin-driven+contractions+induced+by+sperm+entry+predict+mammalian+embryo+viability.">Rhythmic actomyosin-driven contractions induced by sperm entry predict mammalian embryo viability.</a> Nat. Commun. 2, 417 (2011).</li><li>Swann, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phospholipase+C-&#950;-induced+Ca2++oscillations+cause+coincident+cytoplasmic+movements+in+human+oocytes+that+failed+to+fertilize+after+intracytoplasmic+sperm+injection.">Phospholipase C-&#950;-induced Ca2+ oscillations cause coincident cytoplasmic movements in human oocytes that failed to fertilize after intracytoplasmic sperm injection.</a> Fertil. Steril. 97 (3), 742-747 (2012).</li><li>Thakur, A., Mishra, V., Jain, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feed+forward+artificial+neural+network:+tool+for+early+detection+of+ovarian+cancer.">Feed forward artificial neural network: tool for early detection of ovarian cancer.</a> Sci. Pharm. 79 (3), 493-505 (2011).</li><li>Laudani, A., Lozito, G. 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The authors have nothing to disclose.

There are several critical steps one should take care of while performing this protocol with mouse oocytes as well as with those of other species. Once isolated from their follicles, oocytes should be immediately transferred into the recording drops, as the separation from the companion cumulus cells triggers the beginning of the GV-to-MII transition. A possible modification to the present protocol could be the addition of 3-isobutyl-1-methylxanthine (IBMX) to the M2 medium used for COCs isolation. IBMX prevents the imme...

Female infertility is a pathology that affects an increasing number of women. According to the World Health Organization, around 20% of couples are infertile, with a 40% due to female infertility. In addition, one third of women undergoing cancer treatments (300,000/year and 30,000/year in the USA or Italy, respectively) develop premature ovarian failure.
A strategy to prevent infertility in cancer patients is the isolation and cryopreservation of ovarian follicles before the oncological treatment, followed by in vitro maturation (IVM) of GV oocytes to the MII stage (GV-to-MII transition). The availability of non-invasive markers of oocyte developmental competence would improve the fertilization and developmental processes and the overall pregnancy success1,2.
Based on their chromatin configuration observed after staining with the supravital fluorochrome Hoechst 33342, mammalian fully-grown oocytes are classified either as a Surrounded Nucleolus (SN) or a Not Surrounded Nucleolus (NSN)3. Besides their different chromatin organization, these two types of oocytes display many morphological and functional differences3,4,5,6,7,8,9, including their meiotic and developmental competence. When isolated from the ovary and matured in vitro, both type of oocytes reach the MII stage, and after sperm insemination, develop to the 2-cell stage, but only those with an SN chromatin organization may develop to term9. Although good as a classification method for selecting competent vs. incompetent oocytes, the main drawback is the mutagenic effect that the fluorochrome itself and, above all, the UV light used for its detection might have on the cells.
For all these reasons, we searched for other non-invasive markers associated with the SN or NSN chromatin conformation that could substitute the use of Hoechst while maintaining the same high classification accuracy. The time-lapse observation of Cytoplasmic Movement Velocities (CMVs) is emerging as a feature distinctive of the cell status. For example, recent studies demonstrated the association between CMVs recorded at the time of fertilization and the capacity of mouse and human zygotes to complete preimplantation and full-term development10,11.
Based on these earlier studies, we describe here a platform for the recognition of developmentally competent or incompetent mouse fully-grown oocytes5,6,7,8. The platform is based on three main steps: 1) Oocytes isolated from antral follicles are first classified based on their chromatin configuration either as a surrounded nucleolus (SN) or a not-surrounded nucleolus (NSN); 2) Time-Lapse images of CMVs occurring during the GV-to-MII transition of each single oocyte are taken and analyzed with particle image velocimetry (PIV); and 3) the data obtained with PIV are analyzed with a Feed-forward Artificial Neural Network (FANN) for blind classification12,13. We give details of the most critical steps of the procedure designed for the mouse to make it ready available to be tested and used for other mammalian species (e.g., bovine, monkey and humans).

<table border="0" cellpadding="0" cellspacing="0" width="1257">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Folligon</td>
			<td style="width:239px;">Intervet</td>
			<td style="width:157px;">A201A02</td>
			<td style="width:499px;">Hormonal treatment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Hoechst 33342&#160;</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">B2261</td>
			<td>For oocyte heterochromatin staining</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:363px;">Cell culture Petri-dish 35 mm x 10 mm&#160;</td>
			<td style="width:239px;">Corning&#160;</td>
			<td style="width:157px;">430165</td>
			<td>For COCs isolation</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:363px;">EmbryoMax M2 Medium (1X), Liquid, with phenol red</td>
			<td style="width:239px;">Merck-Millipore</td>
			<td style="width:157px;">MR-015-D</td>
			<td>For COCs isolation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MEM Alpha medium (1X) + Glutamax&#160;</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">M4526</td>
			<td>For oocyte in vitro maturation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell culture Petri-dish 35 mm glass-bottom&#160;</td>
			<td style="width:239px;">WillCo&#160;</td>
			<td style="width:157px;">GWSt-3522</td>
			<td>For imaging experiments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">BioStation IM-LM&#160;</td>
			<td style="width:239px;">Nikon</td>
			<td style="width:157px;">MFA91001</td>
			<td>Live cell screening system&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:363px;">Pasteur pipette</td>
			<td style="width:239px;">Delchimica Scientific Glassware</td>
			<td>6709230</td>
			<td>For follicles manipulation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Mineral oil</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">M8410</td>
			<td>To prevent contamination and medium evaporation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Penicillin / Streptomycin</td>
			<td style="width:239px;">Life Technologies</td>
			<td style="width:157px;">15070063</td>
			<td>To prevent medium contamination&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">ML16141079</td>
			<td>For making up &#945;MEM medium&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-Glutamine&#160;</td>
			<td style="width:239px;">Life Technologies</td>
			<td style="width:157px;">25030</td>
			<td>For making up &#945;MEM medium&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Taurine</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">T0625</td>
			<td>For making up &#945;MEM medium&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Bovine Serum Albumin (BSA)</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">A3310</td>
			<td>For making up &#945;MEM media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium pyruvate&#160;</td>
			<td style="width:239px;">Sigma-Aldrich</td>
			<td style="width:157px;">&#160;P4562</td>
			<td>For making up &#945;MEM media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Zoletil (Tiletamina and Zolazepan cloridrate)</td>
			<td style="width:239px;">Virbac Srl</td>
			<td style="width:157px;">QN01AX9</td>
			<td>For mice anesthesia</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:363px;">Cell_PIV sofware&#160;</td>
			<td style="width:239px;">Kindly provided by Dr. Shane Windsor, University of Bristol, UK</td>
			<td style="width:157px;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;-</td>
			<td style="width:499px;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;-</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">MATLAB</td>
			<td style="width:239px;">The MathWorks, Natick, MA&#160;</td>
			<td style="width:157px;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; &#160;-</td>
			<td>For multi-paradigm numerical computing</td>
		</tr>
	</tbody>
</table>

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.

Figure 2 shows a representative developmentally competent and incompetent oocyte, respectively at the beginning (GV) and at the end (MII) of the IVM procedure. IVM of fully-grown mouse oocytes occurs during 15 h culture. The Time-Lapse observation records the progression of meiosis and detects major meiotic events, including the GVBD and the extrusion of the first polar body.
The analysis and compar...

Watch this Scientific Journal Video about A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes at JoVE.com

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

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 ...

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Developmental Biology

6.6K Views.  University of Pavia. 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.

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

Neural Differentiation of Mouse Embryonic Stem Cells in Serum-free Monolayer Culture

The ability to differentiate mouse embryonic stem cells (ESC) to neural progenitors allows the study of the mechanisms controlling neural specification as well as the generation of mature neural cell types for further study. In this protocol we describe a method for the differentiation of ESC to neural progenitors using serum-free, monolayer culture. The method is scalable, efficient and results in production of ~70% neural progenitor cells within 4 - 6 days. It can be applied to ESC from various strains grown under a variety of conditions. Neural progenitors can be allowed to differentiate further into functional neurons and glia or analyzed by microscopy, flow cytometry or molecular techniques. The differentiation process is amenable to time-lapse microscopy and can be combined with the use of reporter lines to monitor the neural specification process. We provide detailed instructions on media preparation and cell density optimization to allow the process to be applied to most ESC lines and a variety of cell culture vessels.

This protocol describes in detail the method for generating neural progenitors from embryonic stem cells using a serum-free monolayer method. These progenitors can be used to derive mature neural cell types or to study the process of neural specification and is amenable to multiwell format scaling for compound screening.

The ability to differentiate mouse embryonic stem cells (ESC) to neural progenitors allows the study of the mechanisms controlling neural specification as ...

Methods for Precisely Localized Transfer of Cells or DNA into Early Postimplantation Mouse Embryos

Manipulation and culture of early mouse embryos is a powerful yet largely under-utilized technology enhancing the value of this model system. Conversely, cell culture has been widely used in developmental biology studies. However, it is important to determine whether in vitro cultured cells truly represent in vivo cell types. Grafting cells into embryos, followed by an assessment of their contribution during development is a useful method to determine the potential of in vitro cultured cells. In this study, we describe a method for grafting cells into a defined site of early postimplantation mouse embryos, followed by ex vivo culture. We also introduce an optimized electroporation method that uses glass capillaries of known diameter, allowing precise localization and adjustment of the number of cells receiving exogenous DNA with both high transfection efficiency and low cell death. These techniques, which do not require any specialized equipment, render experimental manipulations of the gastrulation and early organogenesis-stage mouse embryo possible, allowing analysis of commitment in cultured cell subpopulations and the effect of genetic manipulations in situ on cell differentiation.

We demonstrate a method for grafting cultured cells into defined sites of early mouse embryos to determine their in vivo potential. We also introduce an optimized electroporation method that uses glass capillaries of known diameter, allowing the precise delivery of exogenous DNA into a few cells in the embryos.

Manipulation and culture of early mouse embryos is a powerful yet largely under-utilized technology enhancing the value of this model system. Conversely, ...

Isolation and Characterization of Mouse Antral Oocytes Based on Nucleolar Chromatin Organization

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded Nucleolus) or unable (NSN, Not Surrounded Nucleolus) to develop to the blastocyst stage after in vitro maturation (IVM) and in vitro fertilization (IVF). It makes use of Hoeschst33342 (or any other DNA intercalating dye) able to bind to the heterochromatin of the nucleolus showing a ring in the SN oocytes or not, like in the NSN oocytes. This represents the easiest and quickest way to sort both antral oocytes that can be eventually used for IVM or IVF procedures. 
Briefly, the protocol consists of the following steps: hormone injection to stimulate follicular growth; isolation of the oocytes at the GV stage from the antral compartment by puncturing the ovary with a sterile needle; preparation of thin glass pipettes for mouth pipetting of the oocytes; sorting of the oocytes with Hoechst33342 prepared at a supravital concentration; IVM, IVF or any other molecular/cellular analysis.
Unfortunately there are still few evidences to sort SN and NSN oocytes using less invasive techniques. If and once they will be identified, they could be potentially applied to human assisted reproductive technologies, although with several aspects that should be modified. To date, this technique has potential implications to dramatically increase IVM and IVF successful procedures in both endangered and species with economic interest.

Here we present a protocol for the characterization of mouse antral oocytes based on nucleolar organization.

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded ...

Isolation and Expansion of Adult Canine Hippocampal Neural Precursors

The rate of neurogenesis within the adult hippocampus has been shown to vary across mammalian species. The canine hippocampus, demonstrating a structural intermediacy between the rodent and human hippocampi, is therefore a valuable model in which to study adult neurogenesis. In vitro culture assays are an essential component of characterizing neurogenesis and adult neural precursor cells, allowing for precise control over the cellular environment. To date however, culture protocols for canine cells remain under-represented in the literature. Detailed here are systematic protocols for the isolation and culture of hippocampal neural precursor cells from the adult canine brain. We demonstrate the expansion of canine neural precursor cells as floating neurospheres and as an adherent monolayer culture, producing stable cell lines that are able to differentiation into mature neural cell types in vitro. Adult canine neural precursors are an underused resource that may provide a more faithful analogue for the study of human neural precursors and the cellular mechanisms of adult neurogenesis.

The canine brain is a valuable model in which to study adult neurogenesis. Presented here are protocols for isolating and expanding adult canine hippocampal neural precursor cells from primary brain tissue.

The rate of neurogenesis within the adult hippocampus has been shown to vary across mammalian species. The canine hippocampus, demonstrating a structural ...

Identification Of Erythromyeloid Progenitors And Their Progeny In The Mouse Embryo By Flow Cytometry

Macrophages are professional phagocytes from the innate arm of the immune system. In steady-state, sessile macrophages are found in adult tissues where they act as front line sentinels of infection and tissue damage. While other immune cells are continuously renewed from hematopoietic stem and progenitor cells (HSPC) located in the bone marrow, a lineage of macrophages, known as resident macrophages, have been shown to be self-maintained in tissues without input from bone marrow HSPCs. This lineage is exemplified by microglia in the brain, Kupffer cells in the liver and Langerhans cells in the epidermis among others. The intestinal and colon lamina propria are the only adult tissues devoid of HSPC-independent resident macrophages. Recent investigations have identified that resident macrophages originate from the extra-embryonic yolk sac hematopoiesis from progenitor(s) distinct from fetal hematopoietic stem cells (HSC). Among yolk sac definitive hematopoiesis, erythromyeloid progenitors (EMP) give rise both to erythroid and myeloid cells, in particular resident macrophages. EMP are only generated within the yolk sac between E8.5 and E10.5 days of development and they migrate to the fetal liver as early as circulation is connected, where they expand and differentiate until at least E16.5. Their progeny includes erythrocytes, macrophages, neutrophils and mast cells but only EMP-derived macrophages persist until adulthood in tissues. The transient nature of EMP emergence and the temporal overlap with HSC generation renders the analysis of these progenitors difficult. We have established a tamoxifen-inducible fate mapping protocol based on expression of the macrophage cytokine receptor Csf1r promoter to characterize EMP and EMP-derived cells in vivo by flow cytometry.

While infiltrating macrophages are continuously recruited to adult tissues from circulating precursors, resident macrophages seed their tissue during development, where they are maintained without further input from progenitors. The progenitors for resident macrophages were recently identified. Here, we present methods for the genetic fate mapping of the resident macrophage progenitors.

Macrophages are professional phagocytes from the innate arm of the immune system. In steady-state, sessile macrophages are found in adult tissues where ...

Generation of Genetically Modified Mice through the Microinjection of Oocytes

The use of genetically modified mice has significantly contributed to studies on both physiological and pathological in vivo processes. The pronuclear injection of DNA expression constructs into fertilized oocytes remains the most commonly used technique to generate transgenic mice for overexpression. With the introduction of CRISPR technology for gene targeting, pronuclear injection into fertilized oocytes has been extended to the generation of both knockout and knockin mice. This work describes the preparation of DNA for injection and the generation of CRISPR guides for gene targeting, with a particular emphasis on quality control. The genotyping procedures required for the identification of potential founders are critical. Innovative genotyping strategies that take advantage of the "multiplexing" capabilities of CRISPR are presented herein. Surgical procedures are also outlined. Together, the steps of the protocol will allow for the generation of genetically modified mice and for the subsequent establishment of mouse colonies for a plethora of research fields, including immunology, neuroscience, cancer, physiology, development, and others.

The microinjection of mouse oocytes is commonly used for both classic transgenesis (i.e., the random integration of transgenes) and CRISPR-mediated gene targeting. This protocol reviews the latest developments in microinjection, with a particular emphasis on quality control and genotyping strategies.

The use of genetically modified mice has significantly contributed to studies on both physiological and pathological in vivo processes. The pronuclear ...

A Novel Use of Three-dimensional High-frequency Ultrasonography for Early Pregnancy Characterization in the Mouse

High-frequency ultrasonography (HFUS) is a common method to non-invasively monitor the real-time development of the human fetus in utero. The mouse is routinely used as an in vivo model to study embryo implantation and pregnancy progression. Unfortunately, such murine studies require pregnancy interruption to enable follow-up phenotypic analysis. To address this issue, we used three-dimensional (3-D) reconstruction of HFUS imaging data for early detection and characterization of murine embryo implantation sites and their individual developmental progression in utero. Combining HFUS imaging with 3-D reconstruction and modeling, we were able to accurately quantify embryo implantation site number as well as monitor developmental progression in pregnant C57BL6J/129S mice from 5.5 days post coitus (d.p.c.) through to 9.5 d.p.c. with the use of a transducer. Measurements included: number, location, and volume of implantation sites as well as inter-implantation site spacing; embryo viability was assessed by cardiac activity monitoring. In the immediate post-implantation period (5.5 to 8.5 d.p.c.), 3-D reconstruction of the gravid uterus in both mesh and solid overlay format enabled visual representation of the developing pregnancies within each uterine horn. As genetically engineered mice continue to be used to characterize female reproductive phenotypes derived from uterine dysfunction, this method offers a new approach to detect, quantify, and characterize early implantation events in vivo. This novel use of 3-D HFUS imaging demonstrates the ability to successfully detect, visualize, and characterize embryo-implantation sites during early murine pregnancy in a non-invasive manner. The technology offers a significant improvement over current methods, which rely on the interruption of pregnancies for gross tissue and histopathologic characterization. Here we use a video and text format to describe how to successfully perform ultrasounds of early murine pregnancy to generate reliable and reproducible data with reconstruction of the uterine form in mesh and solid 3-D images.

Mice are widely used to study gestational biology. However, pregnancy termination is required for such studies which precludes longitudinal investigations and necessitates the use of large numbers of animals. Therefore, we describe a non-invasive technique of high-frequency ultrasonography for early detection and monitoring of post-implantation events in the pregnant mouse.

High-frequency ultrasonography (HFUS) is a common method to non-invasively monitor the real-time development of the human fetus in utero. The mouse is ...

Dissection, Culture and Analysis of Primary Cranial Neural Crest Cells from Mouse for the Study of Neural Crest Cell Delamination and Migration

Over the past several decades there has been an increased availability of genetically modified mouse models used to mimic human pathologies. However, the ability to study cell movements and differentiation in vivo is still very difficult. Neurocristopathies, or disorders of the neural crest lineage, are particularly challenging to study due to a lack of accessibility of key embryonic stages and the difficulties in separating out the neural crest mesenchyme from adjacent mesodermal mesenchyme. Here, we set out to establish a well-defined, routine protocol for the culture of primary cranial neural crest cells. In our approach we dissect out the mouse neural plate border during the initial neural crest induction stage. The neural plate border region is explanted and cultured. The neural crest cells form in an epithelial sheet surrounding the neural plate border, and by 24 h after explant, begin to delaminate, undergoing an epithelial-mesenchymal transition (EMT) to become fully motile neural crest cells. Due to our two-dimensional culturing approach, the distinct tissue populations (neural plate versus premigratory and migratory neural crest) can be readily distinguished. Using live imaging approaches, we can then identify changes in neural crest induction, EMT and migratory behaviors. The combination of this technique with genetic mutants will be a very powerful approach for understanding normal and pathological neural crest cell biology.

This protocol describes the dissection and culture of cranial neural crest cells from mouse models, primarily for the study of cell migration. We describe the live imaging techniques used and the analysis of speed and cell shape changes.

Over the past several decades there has been an increased availability of genetically modified mouse models used to mimic human pathologies. However, the ...

Vascular Casting of Adult and Early Postnatal Mouse Lungs for Micro-CT Imaging

Blood vessels form intricate networks in 3-dimensional space. Consequently, it is difficult to visually appreciate how vascular networks interact and behave by observing the surface of a tissue. This method provides a means to visualize the complex 3-dimensional vascular architecture of the lung.
To accomplish this, a catheter is inserted into the pulmonary artery and the vasculature is simultaneously flushed of blood and chemically dilated to limit resistance. Lungs are then inflated through the trachea at a standard pressure and the polymer compound is infused into the vascular bed at a standard flow rate. Once the entire arterial network is filled and allowed to cure, the lung vasculature may be visualized directly or imaged on a micro-CT (&#181;CT) scanner.
When performed successfully, one can appreciate the pulmonary arterial network in mice ranging from early postnatal ages to adults. Additionally, while demonstrated in the pulmonary arterial bed, this method can be applied to any vascular bed with optimized catheter placement and endpoints.

The aim of this technique is ex vivo visualization of pulmonary arterial networks of early postnatal and adult mice through lung inflation and injection of a radio-opaque polymer-based compound via the pulmonary artery. Potential applications for casted tissues are also discussed.

Blood vessels form intricate networks in 3-dimensional space. Consequently, it is difficult to visually appreciate how vascular networks interact and ...

Minimum Volume Vitrification of Immature Feline Oocytes

In wild animals&#8217; conservation programs, gamete banking is crucial to safeguard genetic resources of valuable individuals and rare species and to promote biodiversity preservation. In felids, most species are threatened with extinction, and domestic breeds are used as a model to increase the efficiency of protocols for germplasm banking. Among oocyte cryopreservation techniques, vitrification is more and more popular in human and veterinary assisted reproduction. Cryotop vitrification, which was at first developed for human oocytes and embryos, has demonstrated to be well-suited for cat oocytes. This method offers several advantages, such as the feasibility in field conditions and the speed of the procedure, which can be helpful when several samples need to be processed. However, the efficiency is strongly dependent on the operator&#8217;s skills, and intra- and inter-laboratory standardization are needed, as well as personnel training. This protocol describes minimum volume vitrification of immature feline oocytes on a commercial support in a step by step field-friendly protocol, from oocyte collection to warming. Following the protocol, preservation of oocyte integrity and viability at warming (as high as 90%) can be expected, although there is still room for improvement in post-warming maturation and embryonic development outcomes.

This manuscript describes a protocol for the minimum volume vitrification of immature cat oocytes with laboratory-made media on commercial supports. It covers every step from oocyte isolation from ex vivo gonads to vitrification and warming.

In wild animals&#8217; conservation programs, gamete banking is crucial to safeguard genetic resources of valuable individuals and rare species and to ...