Name: minimally invasive embryo transfer and embryo vitrification at the optimal embryo stage in rabbit model
Uploaded: 2019-05-16T12:30:00
Description: Watch this Scientific Journal Video about Minimally Invasive Embryo Transfer and Embryo Vitrification at the Optimal Embryo Stage in Rabbit Model at JoVE.com

This work was supported by funds from the Ministry of Economy and Competitiveness of Spain (AGL2017-85162-C2-1-R) and Generalitat Valenciana Research Programme (PrometeoII 2014/036). English text version revised by N. Macowan English Language Service

All experimental procedures used in this study were performed in accordance with Directive 2010/63/EU EEC for animal experiments and reviewed and approved by the Ethical Committee for Experimentation with Animals of the Universitat Polit&#232;cnica de Val&#232;ncia, Spain (research code: 2015/VSC/PEA/00170). XGD, FMJ, MPVC and JSV holds an authorization certificate issued by the Valencian governmental administration to experiment on animals. XGD is authorized to in situ supervise the welfare and care of the animals durin...

Since the first documented live birth case from transferred embryos9, this technique and the rabbit species have become crucial in reproductive studies. Besides, embryo research studies involving manipulation, production, cryopreservation, etc. require as a last step the evaluation of embryo capacity to generate healthy full-term offspring. Therefore, embryo transfer technique is indispensable13,28. Over the years, the surgical me...

With the aims of bypassing human infertility or improving dissemination of livestock of high genetic value and preserving animal genetic resources, a set of techniques collectively termed assisted reproduction technologies, such as superovulation, in vitro fertilization, embryo culture, or cryopreservation, were developed1,2. Currently, hormonal treatments are given to stimulate the ovaries and produce a large number of antral ovarian follicles1. Oocytes collected from these follicles can be matured, fertilized, and developed in vitro until they are either cryopreserved or transferred to surrogate mothers3. However, during these treatments, gametes and zygotes are exposed to a series of non-physiological processes that could require embryo adaptation to survive in these conditions4,5. This adaptation is possible due to early embryo plasticity, which allows embryo changes in gene expression and developmental programming6. However, these modifications can influence the subsequent stages of embryo development until adulthood, and it is now widely accepted that methods, timing, cryopreservation procedure or culture conditions show different outcomes on embryo fate7,8. Therefore, to elucidate the specific induced effects of ARTs, the use of well-characterized animal models is inevitable.
The first documented live birth resulting from transfer of mammalian embryos took place in 18909. Today, embryo transfer (ET) to a surrogate female is a crucial step in studying the ART-induced effects during preimplantation on subsequent embryo development stages10. ET techniques depend on the size and anatomical structure of each animal. In the case of large-sized animal models, it has been possible to perform ET by transcervical nonsurgical ET techniques, but in smaller-size species catheterization of the cervix is more complex and surgical techniques are frequently used11. However, surgical ET can cause hemorrhaging that could impair implantation and embryo development, as blood can invade the uterine lumen, causing embryo death10. Transcervical nonsurgical ET techniques are still applied in humans, baboons, bovine, pigs and mice12,13,14,15,16,17, but surgical ETs are still being used in species such as goats, sheep or other animals which present additional difficulties10,18,19,20,21, such as rabbits (two independent cervices) or mice (small size). Nonetheless, surgical transfer methods tend to have gradually been replaced by less invasive methods. Endoscopy was used to transfer embryos, for example, in rabbits, pigs and small ruminants18,19,20. These minimally invasive endoscopy methods can be used to transfer embryos into the ampulla via the infundibulum, which is essential in rabbits and has demonstrated beneficial effects in some species20. This is based on the importance of the correct dialogue between embryo and mother during early embryo stages in the oviduct. As mentioned above, the embryo remodeling that takes place in rabbits during embryo migration through the oviduct is essential to achieve embryos able to implant22,23.
Larger-size animal models, such as bovine, are interesting because the biochemical and preimplantation features are similar to those in human species24. However, large animals are too expensive to use in preliminary trials, and rodents are considered an ideal model (76% model organisms are rodents) for laboratory research25. Nevertheless, the rabbit model provides some advantages over rodents in reproductive studies, as some reproductive biological processes exhibited by humans are more similar in rabbits than those in mice. Human and rabbits present a similar chronological embryonic genome activation, gastrulation and hemochorial placenta structure. In addition, using rabbits it is possible to know the exact timing of fertilization and pregnancy stages due to their induced ovulation25. Rabbit life cycles are short, completing gestation in 31 days and reaching puberty at about 4-5 months; the animal is easy to handle due to its docile and non-aggressive behavior, and its upkeep is very economical compared to the expense of larger animals. Moreover, it is crucial to mention that rabbits have a duplex uterus with two independent cervixes11,25. This places the rabbit in a preferential position, as embryos from the different experimental groups can be transferred into the same animal, but into a different uterine horn. This allows us to compare both experimental effects, reducing the maternal factor from the results.
Today, nonsurgical ET methods are not in use in rabbit. Some studies carried out in the late 90s using a transcervical ET technique resulted in low delivery rates ranging from 5.5% to 20.0%11,26 versus 50-65% by surgical methods, among them the laparoscopy procedure described by Besenfelder and Brem18. The low success rates of these nonsurgical ET methods in rabbits coincide with the lack of the necessary embryo remodeling in the oviduct, which is avoided in transcervical ET. Here, we describe an effective minimally invasive laparoscopic ET procedure using rabbits as a model organism. This technique provides a model for further reproductive research in large animals and humans.
Because rabbits have a particularly narrow time window for embryo implantation, ET in this species requires a high degree of synchrony between the developmental stage of the embryo at ET and the physiological status of the recipient27. In some cases, after a reproductive treatment that slows embryo development (such as in vitro culture) or alters the endometrial receptivity (such as superovulation treatments), there is no synchrony between the embryo and the maternal uterus. These situations can negatively affect outcome. To respond in these contexts, we describe an effective rabbit morula vitrification protocol that allows us to pause, organize and resume the experiments. This process is logistically desirable for reproductive studies and gives us the capacity for long-term storage of embryos, allowing their transport. The laparoscopic procedure and cryopreservation strategies allow better planning of studies with fewer animals. Thus, our methodology offers hygienic and economic advantages and conforms to the concept of the 3Rs (replacement, reduction and refinement) of animal research with the stated goal of improving human treatment of experimental animals. Thus, with these methods, rabbits constitute an ideal model organism for in vivo reproductive assays.

<table>
	<tbody>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>VWR</td>
			<td>332</td>
			<td></td>
		</tr>
		<tr>
			<td>Buprenorphine hydrochloride</td>
			<td>Alvet Escart&#237;</td>
			<td>626</td>
			<td>To be ordered by a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>Buserelin Acetate</td>
			<td>Sigma Aldrich</td>
			<td>B3303</td>
			<td></td>
		</tr>
		<tr>
			<td>Clorhexidine digluconate soap</td>
			<td>Alvet Escart&#237;</td>
			<td>0265DCCJ500B</td>
			<td></td>
		</tr>
		<tr>
			<td>Clorhexidine digluconate solution</td>
			<td>Alvet Escart&#237;</td>
			<td>0265DCCA500B</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2</td>
			<td>Air Liquide</td>
			<td>99921</td>
			<td>CO2 N48.</td>
		</tr>
		<tr>
			<td>CO2 Incubator</td>
			<td>Fisher scientific</td>
			<td>15385194</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl Sulfoxide</td>
			<td>Sigma Aldrich</td>
			<td>W387509</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s phosphate-buffered saline (DPBS)</td>
			<td>Sigma Aldrich</td>
			<td>D5773</td>
			<td>Without calcium chloride.</td>
		</tr>
		<tr>
			<td>Electric razor</td>
			<td>Oster Golden A5</td>
			<td>078005-140-002</td>
			<td></td>
		</tr>
		<tr>
			<td>Endoscope camera</td>
			<td>Optomic Spain S.A</td>
			<td>OP-714</td>
			<td></td>
		</tr>
		<tr>
			<td>Endoscope trocar with silicone leaflet valve</td>
			<td>Karl Storz Endoscopia Ib&#233;rica S.A.</td>
			<td>30114GK</td>
			<td>Lightweight trocar model.</td>
		</tr>
		<tr>
			<td>Enrofloxacin</td>
			<td>Alvet Escart&#237;</td>
			<td>9993046</td>
			<td>To be ordered by a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>Epicraneal needle 23G</td>
			<td>Alvet Escart&#237;</td>
			<td>514056353</td>
			<td>Smaller needles can be also used.</td>
		</tr>
		<tr>
			<td>Epidural catheter</td>
			<td>Vygon corporate</td>
			<td>187.10</td>
			<td></td>
		</tr>
		<tr>
			<td>Epidural needle</td>
			<td>Vygon corporate</td>
			<td>187.10</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylene Glycol</td>
			<td>Sigma Aldrich</td>
			<td>102466-M</td>
			<td></td>
		</tr>
		<tr>
			<td>Eye ointment</td>
			<td>Alvet Escart&#237;</td>
			<td>5273</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine hydrochloride</td>
			<td>Alvet Escart&#237;</td>
			<td>184</td>
			<td>To be ordered by a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>Laparoscopy equipment</td>
			<td>Karl Storz Endoscopia Ib&#233;rica S.A.</td>
			<td>26003 AA</td>
			<td>Hopkins&#174; Laparoscope, 0&#186;-mm straight-viewing laparoscope, 30-cm length, 5-mm working channel.</td>
		</tr>
		<tr>
			<td>Light source</td>
			<td>Optomic Spain S.A</td>
			<td>Fibrolux 250</td>
			<td></td>
		</tr>
		<tr>
			<td>Liquid Nitrogen</td>
			<td>Air Liquide</td>
			<td>P1505XXX</td>
			<td></td>
		</tr>
		<tr>
			<td>Mechanical CO2 insufflator</td>
			<td>Karl Storz Endoscopia Ib&#233;rica S.A.</td>
			<td>Endoflator&#174;</td>
			<td></td>
		</tr>
		<tr>
			<td>Meloxicam</td>
			<td>Alvet Escart&#237;</td>
			<td>9993501</td>
			<td>To be ordered by a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>Petri dishes, 35-mm</td>
			<td>Sigma Aldrich</td>
			<td>CLS430165-500EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic dressing (Nobecutan)</td>
			<td>IBOR medica</td>
			<td>7140028</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic Straw 0.25 mL</td>
			<td>IMV - technologies</td>
			<td>6431</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone iodide solution</td>
			<td>Alvet Escart&#237;</td>
			<td>02656DPYS500S</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>ROBOZ</td>
			<td>RS-5880</td>
			<td>Any regular surgical grade steel small straight scissors will work.</td>
		</tr>
		<tr>
			<td>Silicone tube for insufflator</td>
			<td>Karl Storz Endoscopia Ib&#233;rica S.A.</td>
			<td>20400040</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>MZ16F</td>
			<td>There are cheaper options such as Leica MZ8 or Nikon SMZ-10 or SMZ-2B, to name a few.</td>
		</tr>
		<tr>
			<td>Sterile Gloves</td>
			<td>Alvet Escart&#237;</td>
			<td>087GL010075</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile gown</td>
			<td>Alvet Escart&#237;</td>
			<td>12261501</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile mask</td>
			<td>Alvet Escart&#237;</td>
			<td>058B15924B</td>
			<td></td>
		</tr>
		<tr>
			<td>Straw Plug</td>
			<td>IMV - technologies</td>
			<td>6431</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma Aldrich</td>
			<td>S7903</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe, 1-mL</td>
			<td>Fisher scientific</td>
			<td>11750425</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe, 5-mL</td>
			<td>Fisher scientific</td>
			<td>11773313</td>
			<td></td>
		</tr>
		<tr>
			<td>Urinary catheter</td>
			<td>IMV - technologies</td>
			<td>17722</td>
			<td></td>
		</tr>
		<tr>
			<td>Waterbath</td>
			<td>RAYPA</td>
			<td>BAE-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Alvet Escart&#237;</td>
			<td>525225</td>
			<td>To be ordered by a licensed veterinarian.</td>
		</tr>
		<tr>
			<td>Rabbits</td>
			<td>Universitat Polit&#232;cnica de Val&#232;ncia</td>
			<td>Line A</td>
			<td>Other maternal lines, such as Line V or Line HP can be used.</td>
		</tr>
	</tbody>
</table>

minimally invasive embryo transfer and embryo vitrification at the optimal embryo stage in rabbit model

Assisted reproductive techniques (ARTs), such as in vitro embryo culture or embryo cryopreservation, affect natural development patterns with perinatal and postnatal consequences. To ensure the innocuousness of ART applications, studies in animal models are necessary. In addition, as a last step, embryo development studies require evaluation of their capacity to develop full-term healthy offspring. Here, embryo transfer to the uterus is indispensable to perform any ARTs-related experiment.
The rabbit has been used as a model organism to study mammalian reproduction for over a century. In addition to its phylogenetic proximity to the human species and its small size and low maintenance cost, it has important reproductive characteristics such as induced ovulation, a chronology of early embryonic development similar to humans and a short gestation that allow us to study the consequences of ART application easily. Moreover, ARTs (such as intracytoplasmic sperm injection, embryo culture, or cryopreservation) are applied with suitable efficiency in this species.
Using the laparoscopic embryo transfer technique and the cryopreservation protocol presented in this article, we describe 1) how to transfer embryos through an easy, minimally invasive technique and 2) an effective protocol for long-term storage of rabbit embryos to provide time-flexible logistical capacities and the ability to transport the sample. The outcomes obtained after transferring rabbit embryos at different developmental stages indicate that morula is the ideal stage for rabbit embryo recovery and transfer. Thus, an oviductal embryo transfer is required, justifying the surgical procedure. Furthermore, rabbit morulae are successfully vitrified and laparoscopically transferred, proving the effectiveness of the described techniques.

Minimally invasive laparoscopic transfer of fresh or vitrified embryos places the rabbit among the best model animals for reproductive studies. Table 1 shows the results of fresh ET at different developmental stages (Figure 4) of transferred embryos. The survival rate at birth (percentage of embryos resulting in a pup) proved the efficacy of the laparoscopic technique described in this paper. The higher values were achieved when the ET was pe...

Watch this Scientific Journal Video about Minimally Invasive Embryo Transfer and Embryo Vitrification at the Optimal Embryo Stage in Rabbit Model at JoVE.com

Minimally Invasive Embryo Transfer and Embryo Vitrification at the Optimal Embryo Stage in Rabbit Model

Assisted reproductive techniques (ARTs) are in continuous evaluation to improve outcomes and reduce the associated risks. This manuscript describes a minimally invasive embryo transfer procedure with an efficient cryopreservation protocol that allows the use of rabbits as an ideal animal model of human reproduction.

Assisted reproductive techniques (ARTs), such as in vitro embryo culture or embryo cryopreservation, affect natural development patterns with perinatal ...

The main goal of this experiment is to describe a laparoscopic embryo transfer procedure in rabbit as a model. The main advantage of this technique is that this one works to transfer embryos using an easy, minimally invasive technique. Furthermore, the effective embryo cryopreservation protocol here described also works to long-term storage the rabbit embryos, providing time-flexible logistical capacities and the ability to transport the sample.As we know, assisted reproductive technologies are in continuous evaluation to improve outcomes and reduce the associated risks. Therefore, using both techniques, rabbit can be used as an ideal animal model of human reproduction to answer key questions in this field, such as the effects of the in vitro embryo manipulation on offspring. Visual demonstration of these matters are critical as the embryo transfer steps are difficult to learn, because it must be done with great precision to ensure the success of the technique.For embryonic vitrification, immerse the embryos in equilibrating solution for two minutes, followed by a one minute incubation in vitrification solution. At the end of the incubation, load the embryos into a 125 microliter plastic mini-straw, and couple the closed end of the mini-straw with an appropriate one milliliter microdispenser. Aspirate base medium up to one-third of the straw length, followed by a small air bubble.Next, use a stereomicroscope to aspirate the embryos in 40 microliters of vitrification solution, followed by another small air bubble and enough base medium to move first liquid fraction up to the cotton of the mini-straw. Then close the opened end of the mini-straw with a straw plug, plunge the mini-straw directly into liquid nitrogen to achieve vitrification, and store the mini-straw in a liquid nitrogen dewar. To thaw the embryos for a transfer, place the mini-straw horizontally 10 centimeters from the liquid nitrogen vapor for 20 to 30 seconds.When the crystallization process begins inside the mini-straw, immerse the mini-straw in the 25 degree celsius water bath for 10 to 15 seconds. Immediately remove the mini-straw and cotton plugs and use a coupled microdispenser to expel the mini-straw contents into a plate containing 25 degrees celsius base medium supplemented with 0.33 molar sucrose solution, in which embryos must remain during five minutes. Then transfer the embryos to a plate of fresh base medium for another five minute incubation.As many days before as the age of the embryos to be transferred, observe the turgidity and color of the vulvas of the available sexually mature 4.5 month old female rabbits, and induce ovulation in the receptive animals with a single intramuscular injection of one microgram of buserelin acetate regardless of body weight. On the day of the transfer, rinse the fresh or thawed embryos in 37 degree celsius base medium under a stereomicroscope, and attach an appropriately configured 17-gauge epidural catheter to a one milliliter syringe. Aspirate one centimeter of base medium into the catheter, followed by a small air bubble.Then aspirate five to seven embryos and 10 microliters of base medium, followed by another small air bubble, and a final one centimeter of base medium. Once the embryos have been loaded, place the anesthetized recipient rabbit in a cage on a warming stage, and apply ointment to the animal's eyes. After confirming a lack of response to pedal reflex, shave the fur from the ventral abdomen, clean the surgical area with chlorhexidine gluconate soap, and remove any remaining hair.Cover the area with a sterile drape with a hole for the surgical area, and insert one endoscopic trocar five centimeters into the abdominal cavity, two centimeters caudal to the zyphoid process, and use a pressure regulating mechanical insufflator to inflate the peritoneal cavity. Insert the endoscope camera through the endoscopic trocar, and insert the 17-gauge epidural needle into the inguinal region, two to three centimeters from the infundibulum. Insert the loaded catheter through the epidural needle into the abdomen, and insert one to two centimeters of the epidural catheter through the infundibulum in the ampulla.Gently depress the catheter plunger to release the embryos into the oviduct. Both air bubbles must exit from the catheter. Remove the catheter just after the embryos have been released, and aspirate and release the remaining medium to confirm the absence of the embryos.After confirming a successful transfer of the embryos, remove the epidural needle and the endoscope camera, and release the abdominal carbon dioxide through the endoscopic trocar. Clean the trocar incision with chlorhexidine solution, and close the wound with a micronised aluminum and a plastic dressing. Then treat the animal with the appropriate antibiotics and analgesics, and monitor the animal until full recovery.Minimally invasive laparoscopic embryo transfer places the rabbit among the best animal models for reproductive studies, with a high percentage of transferred fresh embryos resulting in a pup. Notably, higher values are achieved when the fresh embryo transfer is performed with embryos in either the early or compact morulae stage. Similar results are observed after early and compacted vitrified rabbit morula transfer, particularly with compact morulae, confirming the efficacy and reliability of this technique for transferring fresh in-vitrified embryos in rabbits.Following this procedure, other methods like conditional Assistive Reproductive Technologies can be performed in order to answer additional questions like how the addition of densities can incur in an analgesic effect later in life. After recent development, this technique paves the way for scientists in the field of reproduction to explore this effect in humans based on the close phylogenetic distance between rabbit and humans. Thus, this technique can provide results easily transferrable to human clinical medicine, as well in other mammal species.Don't forget that our method offers some hygienic and economic advantages conforming to the concept of three R's of animal welfare, Replacement, Reduction, and Refinement, by intending the goal of improving human treatment of experimental animals.

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Research

JoVE Journal

Developmental Biology

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

Characterizing thymic settling progenitors is important to understand the pre-thymic stages of T cell development, essential to devise strategies for T cell replacement in lymphopenic patients. We studied thymic settling progenitors from murine embryonic day 13 and 18 thymi by two complementary in vitro and in vivo techniques, both based on the &#8220;hanging drop&#8221; method. This method allowed colonizing irradiated fetal thymic lobes with E13 and/or E18 thymic progenitors distinguished by CD45 allotypic markers and thus following their progeny. Colonization with mixed populations allows analyzing cell autonomous differences in biologic properties of the progenitors while colonization with either population removes possible competitive selective pressures. The colonized thymic lobes can also be grafted in immunodeficient male recipient mice allowing the analysis of the mature T cell progeny in vivo, such as population dynamics of the peripheral immune system and colonization of different tissues and organs. Fetal thymic organ cultures revealed that E13 progenitors developed rapidly into all mature CD3+ cells and gave rise to the canonical &#947;&#948; T cell subset, known as dendritic epithelial T cells. In comparison, E18 progenitors have a delayed differentiation and were unable to generate dendritic epithelial T cells. The monitoring of peripheral blood of thymus-grafted CD3-/- mice further showed that E18 thymic settling progenitors generate, with time, larger numbers of mature T cells than their E13 counterparts, a feature that could not be appreciated in the short term fetal thymic organ cultures.

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

This article describes in vivo and in vitro methodology to characterize the thymic settling progenitors by the analysis of the kinetics of generation, phenotype and numbers of their T cell progeny.

Characterizing thymic settling progenitors is important to understand the pre-thymic stages of T cell development, essential to devise strategies for T ...

Microbead Implantation in the Zebrafish Embryo

The zebrafish has emerged as a valuable genetic model system for the study of developmental biology and disease. Zebrafish share a high degree of genomic conservation, as well as similarities in cellular, molecular, and physiological processes, with other vertebrates including humans. During early ontogeny, zebrafish embryos are optically transparent, allowing researchers to visualize the dynamics of organogenesis using a simple stereomicroscope. Microbead implantation is a method that enables tissue manipulation through the alteration of factors in local environments. This allows researchers to assay the effects of any number of signaling molecules of interest, such as secreted peptides, at specific spatial and temporal points within the developing embryo. Here, we detail a protocol for how to manipulate and implant beads during early zebrafish development.

The zebrafish is an excellent model system for genetic and developmental studies. Bead implantation is a valuable tissue manipulation technique that can be used to interrogate developmental mechanisms by introducing alterations in local cellular environments. This protocol describes how to perform microbead implantation in the zebrafish embryo.

The zebrafish has emerged as a valuable genetic model system for the study of developmental biology and disease. Zebrafish share a high degree of genomic ...

Imaging Subcellular Structures in the Living Zebrafish Embryo

In vivo imaging provides unprecedented access to the dynamic behavior of cellular and subcellular structures in their natural context. Performing such imaging experiments in higher vertebrates such as mammals generally requires surgical access to the system under study. The optical accessibility of embryonic and larval zebrafish allows such invasive procedures to be circumvented and permits imaging in the intact organism. Indeed the zebrafish is now a well-established model to visualize dynamic cellular behaviors using in vivo microscopy in a wide range of developmental contexts from proliferation to migration and differentiation. A more recent development is the increasing use of zebrafish to study subcellular events including mitochondrial trafficking and centrosome dynamics. The relative ease with which these subcellular structures can be genetically labeled by fluorescent proteins and the use of light microscopy techniques to image them is transforming the zebrafish into an in vivo model of cell biology. Here we describe methods to generate genetic constructs that fluorescently label organelles, highlighting mitochondria and centrosomes as specific examples. We use the bipartite Gal4-UAS system in multiple configurations to restrict expression to specific cell-types and provide protocols to generate transiently expressing and stable transgenic fish. Finally, we provide guidelines for choosing light microscopy methods that are most suitable for imaging subcellular dynamics.

Imaging the dynamic behavior of organelles and other subcellular structures in vivo can shed light on their function in physiological and disease conditions. Here, we present methods for genetically tagging two organelles, centrosomes and mitochondria, and imaging their dynamics in living zebrafish embryos using wide-field and confocal microscopy.

In vivo imaging provides unprecedented access to the dynamic behavior of cellular and subcellular structures in their natural context. Performing such ...

Observing Mitotic Division and Dynamics in a Live Zebrafish Embryo

Mitosis is critical for organismal growth and differentiation. The process is highly dynamic and requires ordered events to accomplish proper chromatin condensation, microtubule-kinetochore attachment, chromosome segregation, and cytokinesis in a small time frame. Errors in the delicate process can result in human disease, including birth defects and cancer. Traditional approaches investigating human mitotic disease states often rely on cell culture systems, which lack the natural physiology and developmental/tissue-specific context advantageous when studying human disease. This protocol overcomes many obstacles by providing a way to visualize, with high resolution, chromosome dynamics in a vertebrate system, the zebrafish. This protocol will detail an approach that can be used to obtain dynamic images of dividing cells, which include: in vitro transcription, zebrafish breeding/collecting, embryo embedding, and time-lapse imaging. Optimization and modifications of this protocol are also explored. Using H2A.F/Z-EGFP (labels chromatin) and mCherry-CAAX (labels cell membrane) mRNA-injected embryos, mitosis in AB wild-type, auroraBhi1045, and esco2hi2865 mutant zebrafish is visualized. High resolution live imaging in zebrafish allows one to observe multiple mitoses to statistically quantify mitotic defects and timing of mitotic progression. In addition, observation of qualitative aspects that define improper mitotic processes (i.e., congression defects, missegregation of chromosomes, etc.) and improper chromosomal outcomes (i.e., aneuploidy, polyploidy, micronuclei, etc.) are observed. This assay can be applied to the observation of tissue differentiation/development and is amenable to the use of mutant zebrafish and pharmacological agents. Visualization of how defects in mitosis lead to cancer and developmental disorders will greatly enhance understanding of the pathogenesis of disease.

Mitosis is critical to every living organism and defects often lead to cancer and developmental disorders. Using this imaging protocol and zebrafish as a model system, researchers can visualize mitosis in a live vertebrate organism and the multitude of defects that arise when mitotic processes are defective.

Mitosis is critical for organismal growth and differentiation. The process is highly dynamic and requires ordered events to accomplish proper chromatin ...

Embryo Microinjection and Electroporation in the Chordate Ciona intestinalis

Simple model organisms are instrumental for in vivo studies of developmental and cellular differentiation processes. Currently, the evolutionary distance to man of conventional invertebrate model systems and the complexity of genomes in vertebrates are critical challenges to modeling human normal and pathological conditions. The chordate Ciona intestinalis is an invertebrate chordate that emerged from a common ancestor with the vertebrates and may represent features at the interface between invertebrates and vertebrates. A common body plan with much simpler cellular and genomic composition should unveil gene regulatory network (GRN) links and functional genomics readouts explaining phenomena in the vertebrate condition. The compact genome of Ciona, a fixed embryonic lineage with few divisions and large cells, combined with versatile community tools foster efficient gene functional analyses in this organism. Here, we present several crucial methods for this promising model organism, which belongs to the closest sister group to vertebrates. We present protocols for transient transgenesis by electroporation, along with microinjection-mediated gene knockdown, which together provide the means to study gene function and genomic regulatory elements. We extend our protocols to provide information on how community databases are utilized for in silico design of gene regulatory or gene functional experiments. An example study demonstrates how novel information can be gained on the interplay, and its quantification, of selected neural factors conserved between Ciona and man. Furthermore, we show examples of differential subcellular localization in embryonic cells, following DNA electroporation in Ciona zygotes. Finally, we discuss the potential of these protocols to be adapted for tissue specific gene interference with emerging gene editing methods. The in vivo approaches in Ciona overcome major shortcomings of classical model organisms in the quest of unraveling conserved mechanisms in the chordate developmental program, relevant to stem cell research, drug discovery, and subsequent clinical application.

Embryo Microinjection and Electroporation in the Chordate Ciona intestinalis

We present transient transgenesis and gene knockdown in Ciona intestinalis, a chordate sister group to vertebrates, using microinjection and electroporation techniques. Such methods facilitate functional genomics in this simple invertebrate that features rudimentary characteristics of vertebrates, including notochord and head sensory epithelia, and many orthologs of human disease associated genes.

Simple model organisms are instrumental for in vivo studies of developmental and cellular differentiation processes. Currently, the evolutionary distance ...

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 ...

Use of Immunolabeling to Analyze Stable, Dynamic, and Nascent Microtubules in the Zebrafish Embryo

Microtubules (MTs) are dynamic and fragile structures that are challenging to image in vivo, particularly in vertebrate embryos. Immunolabeling methods are described here to analyze distinct populations of MTs in the developing neural tube of the zebrafish embryo. While the focus is on neural tissue, this methodology is broadly applicable to other tissues. The procedures are optimized for early to mid-somitogenesis-stage embryos (1 somite to 12 somites), however they can be adapted to a range of other stages with relatively minor adjustments. The first protocol provides a method to assess the spatial distribution of stable and dynamic MTs and perform a quantitative analysis of these populations with image-processing software. This approach complements existing tools to image microtubule dynamics and distribution in real-time, using transgenic lines or transient expression of tagged constructs. Indeed, such tools are very useful, however they do not readily distinguish between dynamic and stable MTs. The ability to image and analyze these distinct microtubule populations has important implications for understanding mechanisms underlying cell polarization and morphogenesis. The second protocol outlines a technique to analyze nascent MTs specifically. This is accomplished by capturing the de novo growth properties of MTs over time, following microtubule depolymerization with the drug nocodazole and a recovery period after drug washout. This technique has not yet been applied to the study of MTs in zebrafish embryos, but is a valuable assay for investigating the in vivo function of proteins implicated in microtubule assembly.

Immunolabeling methods to analyze distinct populations of microtubules in the developing zebrafish brain are described here, which are broadly applicable to other tissues. The first protocol outlines an optimized method for immunolabeling stable and dynamic microtubules. The second protocol provides a method to image and quantify nascent microtubules specifically.

Microtubules (MTs) are dynamic and fragile structures that are challenging to image in vivo, particularly in vertebrate embryos. Immunolabeling methods ...

AFM and Microrheology in the Zebrafish Embryo Yolk Cell

Elucidating the factors that direct the spatio-temporal organization of evolving tissues is one of the primary purposes in the study of development. Various propositions claim to have been important contributions to the understanding of the mechanical properties of cells and tissues in their spatiotemporal organization in different developmental and morphogenetic processes. However, due to the lack of reliable and accessible tools to measure material properties and tensional parameters in vivo, validating these hypotheses has been difficult. Here we present methods employing atomic force microscopy (AFM) and particle tracking with the aim of quantifying the mechanical properties of the intact zebrafish embryo yolk cell during epiboly. Epiboly is an early conserved developmental process whose study is facilitated by the transparency of the embryo. These methods are simple to implement, reliable, and widely applicable since they overcome intrusive interventions that could affect tissue mechanics. A simple strategy was applied for the mounting of specimens, AFM recording, and nanoparticle injections and tracking. This approach makes these methods easily adaptable to other developmental times or organisms.

The lack of tools to measure material properties and tensional parameters in vivo prevents validating their roles during development. We employed atomic force microscopy (AFM) and nanoparticle-tracking to quantify mechanical features on the intact zebrafish embryo yolk cell during epiboly. These methods are reliable and widely applicable avoiding intrusive interventions.

Elucidating the factors that direct the spatio-temporal organization of evolving tissues is one of the primary purposes in the study of development. ...

Effectiveness of the Air Stripping in Two Salmonid Fish, Rainbow Trout (Oncorhynchus Mykiss) and Brown Trout (Salmo Trutta Morpha fario)

Egg collection is one of the most crucial procedures during fish reproduction in salmonid hatcheries. Classic methods involve the use of hand massage on fish abdomens to expel the eggs. An alternative method uses the pressure of gas injected into the body cavity, which causes the subsequent release of the eggs. This method is believed to have less negative effects on both the welfare and egg quality of the broodstocks. Herein, we compare the results of air and hand stripping methods with respect to one-year survival and egg quantity and quality in two salmonid fish, rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta morpha fario). Our results indicate that air stripping yielded a better quality of eggs and higher one-year survival rate in rainbow trout. In addition, air stripping resulted in lower mortality rate than the group subjected to hand stripping (25% vs. 35%). The pH and hatching rate of the hand stripped group was lower than those of the air stripped group. In the case of brown trout, the quality of eggs obtained by both hand and air-stripping methods was similar; however, the one-year losses in fish were higher in air stripped group (15% compared to 0% in hand stripped fish). Although the advantages of air stripping method over hand stripping in terms of egg quality might not be observed in all salmonid species, the air-stripping procedure might be a promising option to be adopted in hatcheries as it ensures a high level of reproducibility and efficiency.

Effectiveness of the Air Stripping in Two Salmonid Fish, Rainbow Trout Oncorhynchus Mykiss and Brown Trout Salmo Trutta Morpha fario

The principal aim of this study is to standardize and test the pneumatic method (air stripping) of collecting eggs in rainbow trout and brown trout. This method allows effective and simple collection of the eggs without the necessity of fish abdomen massage.

Egg collection is one of the most crucial procedures during fish reproduction in salmonid hatcheries. Classic methods involve the use of hand massage on ...

Following Endocardial Tissue Movements via Cell Photoconversion in the Zebrafish Embryo

During embryogenesis, cells undergo dynamic changes in cell behavior, and deciphering the cellular logic behind these changes is a fundamental goal in the field of developmental biology. The discovery and development of photoconvertible proteins have greatly aided our understanding of these dynamic changes by providing a method to optically highlight cells and tissues. However, while photoconversion, time-lapse microscopy, and subsequent image analysis have proven to be very successful in uncovering cellular dynamics in organs such as the brain or the eye, this approach is generally not used in the developing heart due to challenges posed by the rapid movement of the heart during the cardiac cycle. This protocol consists of two parts. The first part describes a method for photoconverting and subsequently tracking endocardial cells (EdCs) during zebrafish atrioventricular canal (AVC) and atrioventricular heart valve development. The method involves temporally stopping the heart with a drug in order for accurate photoconversion to take place. Hearts are allowed to resume beating upon removal of the drug and embryonic development continues normally until the heart is stopped again for high-resolution imaging of photoconverted EdCs at a later developmental time point. The second part of the protocol describes an image analysis method to quantify the length of a photoconverted or non-photoconverted region in the AVC in young embryos by mapping the fluorescent signal from the three-dimensional structure onto a two-dimensional map. Together, the two parts of the protocol allows one to examine the origin and behavior of cells that make up the zebrafish AVC and atrioventricular heart valve, and can potentially be applied for studying mutants, morphants, or embryos that have been treated with reagents that disrupt AVC and/or valve development.

This protocol describes a method for the photoconversion of Kaede fluorescent protein in endocardial cells of the living zebrafish embryo that enables the tracking of endocardial cells during atrioventricular canal and atrioventricular heart valve development.

During embryogenesis, cells undergo dynamic changes in cell behavior, and deciphering the cellular logic behind these changes is a fundamental goal in the ...