Name: generation of transgenic rats using a lentiviral vector approach
Uploaded: 2020-05-17T12:30:00
Description: Watch this Scientific Journal Video about Generation of Transgenic Rats using a Lentiviral Vector Approach at JoVE.com

This study was supported by the ANIMOD project within the Team Tech Core Facility Plus program of the Foundation for Polish Science, co-financed by the European Union under the European Regional Development Fund to WK.

The production and application of viral vectors was in accordance with Biosafety Level 2 guidelines and was approved by the Polish Ministry of Environment. All experimental animal procedures that are described below were approved by the Local Ethical Committee. The animals were housed in individually ventilated cages at a stable temperature (21&#8211;23 &#176;C) and humidity (50&#8211;60%) with ad libitum access to water and food under a 12 h/12 h light/dark cycle.
1. Lentiviral vector productio...

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Advances in transgenic technologies have made rodent models an invaluable tool in biomedical research. They provide the opportunity to study genotype-phenotype relationships in vivo. Here, we present a widely available alternative for conventional transgenesis by pronuclear injections. The use of lentiviral gene transduction bypasses the need for demanding microinjections because viral vectors can be injected under the zona pellucida. This approach does not affect embryo integrity, which essentially guarantees a 100% sur...

For many years, laboratory rodents, such as rats and mice, have been used to model human physiological and pathological conditions. Animal research has led to discoveries that were unattainable by any other means. Initially, genetic studies focused on the analysis of spontaneously occurring disorders and phenotypes that are considered to closely mimic the human condition1. The development of genetic engineering methods allowed the introduction or deletion of specific genes to obtain a desired phenotype. Therefore, the generation of transgenic animals is recognized as a fundamental technique in modern research that allows studies of gene function in living organisms.
Transgenic animal technology has become possible through a combination of achievements in experimental embryology and molecular biology. In the 1960s, the Polish embryologist A. K. Tarkowski published the first work on mouse embryo manipulation during the early stages of development2. Additionally, molecular biologists developed techniques to generate DNA vectors (i.e., carriers) for the inter alia introduction of foreign DNA into the animal&#8217;s genome. These vectors allow the propagation of selected genes and their appropriate modification, depending on the type of research that is conducted. The term &#8220;transgenic animal&#8221; was introduced by Gordon and Ruddle3.
The first widely accepted species that was used in neurobiology, physiology, pharmacology, toxicology, and many other fields of biological and medical sciences was the Norway rat, Rattus norvegicus4. However, because of the difficulty in manipulating rat embryos, the house mouse Mus musculus has become the dominant animal species in genetic research5. Another reason for the primacy of the mouse in such research was the availability of embryonic stem cell technology to generate knockout animals for this species. The most commonly used technique of transgenesis (2&#8211;10% of transgenic offspring relative to all born animals) is the microinjection of DNA fragments into a pronucleus of a fertilized oocyte. In 1990, this approach, which was first introduced in mice, was adapted for rats6,7. Rat transgenesis by pronuclear injection is characterized by lower efficiency8 compared with mice, which is strictly related to the presence of elastic plasma and pronuclear membranes9. Although the survival of embryos after manipulation is 40&#8211;50% lower than in mice, this technique is considered a standard in the generation of genetically modified rats10. Alternative approaches that can guarantee efficient transgene incorporation and higher survival rates of injected zygotes have been investigated.
The key determinant of stable transgene expression and transmission to progeny is its integration into the host cell genome. Lentiviruses (LVs) have the distinctive feature of being able to infect both dividing and non-dividing cells. Their use as a tool for the incorporation of heterologous genes into embryos proved to be highly efficient11, and transgenic individuals are characterized by stable expression of the incorporated DNA fragment. The efficacy of lentiviral vectors has been confirmed for the genetic modification of mice12,13, rats12,14, and other species11. In this method, the LV suspension is injected under the zona pellucida of the embryo at the stage of two pronuclei. This technique essentially guarantees 100% survival of the embryos because the oolemma remains unaffected. The production of high-quality and relatively highly concentrated LV suspensions are crucial factors. However, lower concentrations of LV suspensions can be overcome by repeated injections11, which increases the amount of viral particles at the egg surface while not affecting membrane integration. Embryos that are subjected to repeated injections into the perivitelline space develop further, and transgenic offspring can transmit the transgene through the germline. The efficiency of transgenic rat generation by lentiviral transgenesis can be as high as 80%12.
Here, we describe the production of HIV-1-derived recombinant lentivirus that was pseudotyped with vesicular stomatitis virus (VSV) G envelope protein. The use of the second-generation packaging system VSV pseudotype determines the wide infectivity of viral particles and allows the production of highly stable vectors that can be concentrated by ultracentrifugation and cryopreserved. After titer verification, the vectors are ready to be used as a vehicle for transgene delivery into albino Wistar rat zygotes. After a series of injections, the embryos can be cultured overnight and transferred at the two-cell stage to foster mothers. At this point, one of two alternative approaches can be considered. The standard procedure utilizes pseudopregnant females as embryo recipients. However, when the pregnancy rate is low after mating with vasectomized males, the embryos can be implanted into pregnant Wistar/Sprague-Dawley (SD) females that are mated with fertile male rats with a dark fur color (e.g., Brown Norway [BN] rats). The color of the fur allows the distinction of offspring from natural pregnancy from offspring that originate from the transferred manipulated embryos.

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	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">7500 Real Time PCR System</td>
			<td style="width:186px;">Applied Biosystems</td>
			<td style="width:354px;"></td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Aerrane (isoflurane)</td>
			<td style="width:186px;">Baxter</td>
			<td style="width:354px;">FDG9623</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Aspirator tube assemblies for calibrated microcapillary pipettes</td>
			<td>Sigma</td>
			<td>A5177-5EA</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Atipam 5 mg/ml</td>
			<td>Eurovet Animal Health BV</td>
			<td>N/A</td>
			<td>0.5 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Baytril 25 mg/ml (enrofloksacin)</td>
			<td>Bayer</td>
			<td>N/A</td>
			<td>5-10 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Borosilicate glass capillaries with filament GC100TF-15</td>
			<td style="width:186px;">Harvard Apparatus Limited</td>
			<td style="width:354px;">30-0039</td>
			<td style="width:172px;">injection capillary</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Bupivacaine 25 mg/ml</td>
			<td>Advanz Pharma</td>
			<td>N/A</td>
			<td>0.25% in&#160; 0.9% NaCl</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Butomidor 10 mg/ml (butorphanol&#160; tartrate)</td>
			<td>Orion Pharma</td>
			<td>N/A</td>
			<td>1 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">CELLSTAR Tissue Cell Culture Dish 35-mm</td>
			<td style="width:186px;">Greiner Bio-One</td>
			<td style="width:354px;">627160</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="49">
			<td height="49" style="height:49px;width:496px;">CELLSTAR Tissue Cell Culture Dish 60-mm</td>
			<td style="width:186px;">Greiner Bio-One</td>
			<td style="width:354px;">628160</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">CellTram Oil</td>
			<td style="width:186px;">Eppendorf</td>
			<td style="width:354px;">5176 000.025</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Cepetor (Medetomidine) 1 mg/ml</td>
			<td>cp-pharma</td>
			<td>N/A</td>
			<td>0.5 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Chorulon, Human Chorionic Gonadotrophin&#160;</td>
			<td>Intervet</td>
			<td>N/A</td>
			<td>150 IU/ ml ml 0.9% NaCl</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">DMEM low glucose</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">D6048</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">DNase, RNase-free</td>
			<td style="width:186px;">A&#38;A Biotechnology</td>
			<td style="width:354px;">1009-100</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">EmbryoMax Filtered Light Mineral Oil</td>
			<td>Sigma</td>
			<td>ES-005-C</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Envelope protein coding plasmid for lentiviral vectors (VSVg plasmid)&#160;</td>
			<td style="width:186px;">ADDGENE</td>
			<td style="width:354px;">14888</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">FemtoJet</td>
			<td style="width:186px;">Eppendorf</td>
			<td style="width:354px;">4i /5252 000.013</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Fetal Bovine Serum</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">F9665-500ML</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Folligon, Pregnant Mare&#8217;s Serum Gonadotropin&#160;</td>
			<td>Intervet</td>
			<td>N/A</td>
			<td>125 IU/ml in .9% NaCl</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">HEK 293T cells&#160;</td>
			<td style="width:186px;">ATCC</td>
			<td style="width:354px;">ATCC CRL-3216</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Hyaluronidase from Bovine Testis&#160;</td>
			<td>Sigma</td>
			<td>H4272-30MG</td>
			<td>0.5 mg/ml in M2 medium</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Inverted Microscope&#160;</td>
			<td style="width:186px;">Zeiss</td>
			<td style="width:354px;">Axiovert 200</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Ketamine 100mg/ml</td>
			<td>Biowet Pulawy</td>
			<td>N/A</td>
			<td>50 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Liquid Paraffin</td>
			<td>Merck Millipore</td>
			<td>8042-47-5</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">M16 medium EmbryoMax</td>
			<td>Sigma</td>
			<td>MR-016-D</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">M2 medium</td>
			<td>Sigma</td>
			<td>M7167</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Magnesium Chloride 1M</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">63069-100ML</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Microforge</td>
			<td style="width:186px;">Narishige</td>
			<td style="width:354px;">MF-900</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Mineral Oil</td>
			<td>Sigma</td>
			<td>M8410-500ML</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">NaCl 0.9%</td>
			<td>POLPHARMA OTC</td>
			<td>N/A</td>
			<td>sterile, 5ml ampules</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Operation microscope&#160;</td>
			<td style="width:186px;">Inami Ophthalmic Instruments</td>
			<td style="width:354px;">Deca-21</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:35px;">Packaging system coding plasmid for lentiviral vectors&#160; (delta R8.2 plasmid)</td>
			<td style="width:186px;">ADDGENE</td>
			<td style="width:354px;">12263</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">PEI reagent (Polyethylenimine, Mw ~ 25,000,),</td>
			<td style="width:186px;">Polysciences, Inc</td>
			<td style="width:354px;">23966-1</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Penicilin-streptomycin</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">P0781-100ML</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Phosphate Buffered Saline, pH 7.4, liquid, sterile-filtered, suitable for cell culture</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">806552-500ML</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Puller&#160;</td>
			<td style="width:186px;">Sutter Instrument Co.</td>
			<td style="width:354px;">P-97</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Reflex Clip Applier/Reflex Clips</td>
			<td style="width:186px;">World Precision Instruments</td>
			<td style="width:354px;">500345/500346</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Safil, polyglycolic acid, braided, coated, absorbable threads</td>
			<td style="width:186px;">B.Braun Surgical</td>
			<td style="width:354px;">1048029</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">Stereomicroscope</td>
			<td style="width:186px;">Olympus</td>
			<td style="width:354px;">SZX16</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Surgical Sewing Thread</td>
			<td>B.Braun&#160;</td>
			<td>C1048040</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">SYBR Green PCR Master Mix</td>
			<td style="width:186px;">Applied Biosystem</td>
			<td style="width:354px;">4334973</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Tolfedine 4% (tolfenamic acid)</td>
			<td>Vetoquinol</td>
			<td>N/A</td>
			<td>2 mg/kg</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:496px;">TransferMan NK2</td>
			<td style="width:186px;">Eppendorf</td>
			<td style="width:354px;">N/A</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:496px;">Trypsin EDTA solution</td>
			<td style="width:186px;">Sigma Aldrich</td>
			<td style="width:354px;">T3924-500ML</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:496px;">Ultracentrifuge</td>
			<td style="width:186px;">Beckman Coulter</td>
			<td style="width:354px;">Optima L-100 XP&#160;</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:496px;">VacuTip</td>
			<td style="width:186px;">Eppendorf</td>
			<td style="width:354px;">5175108.000</td>
			<td style="width:172px;">holders capillary</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Vita-POS</td>
			<td>Ursapharm</td>
			<td>N/A</td>
			<td>eye ointment</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:496px;">Warming Plate</td>
			<td style="width:186px;">Semic</td>
			<td style="width:354px;">N/A</td>
			<td style="width:172px;"></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Watchmaker Forceps</td>
			<td style="width:186px;">VWR</td>
			<td>470018-868</td>
			<td style="width:172px;"></td>
		</tr>
	</tbody>
</table>

generation of transgenic rats using a lentiviral vector approach

Transgenic animal models are fundamentally important for modern biomedical research. The incorporation of foreign genes into early mouse or rat embryos is an invaluable tool for gene function analysis in living organisms. The standard transgenesis method is based on microinjecting foreign DNA fragments into a pronucleus of a fertilized oocyte. This technique is widely used in mice but remains relatively inefficient and technically demanding in other animal species. The transgene can also be introduced into one-cell-stage embryos via lentiviral infection, providing an effective alternative to standard pronuclear injections, especially in species or strains with a more challenging embryo structure. In this approach, a suspension that contains lentiviral vectors is injected into the perivitelline space of a fertilized rat embryo, which is technically less demanding and has a higher success rate. Lentiviral vectors were shown to efficiently incorporate the transgene into the genome to determine the generation of stable transgenic lines. Despite some limitations (e.g., Biosafety Level 2 requirements, DNA fragment size limits), lentiviral transgenesis is a rapid and efficient transgenesis method. Additionally, using female rats that are mated with a fertile male strain with a different dominant fur color is presented as an alternative to generate pseudopregnant foster mothers.

Using the protocol described herein, lentiviral vectors that carried the Syn-TDP-43-eGFP construct were produced (physical LV titer = 3.4 x 108/&#181;L) and then could be used for one-cell-stage embryo subzonal injections. Only embryos with two visible pronuclei were subjected to the procedure. The number of injections of viral suspensions was determined experimentally. High implantation efficiency and a simultaneous lack of transgenic offspring were considered indicators of an insufficient number of viral par...

Watch this Scientific Journal Video about Generation of Transgenic Rats using a Lentiviral Vector Approach at JoVE.com

Generation of Transgenic Rats using a Lentiviral Vector Approach

This article aims to provide the methodology for lentiviral transgenesis in rat embryos using multiple injections of a virus suspension into the zygote perivitelline space. Female rats that are mated with a fertile male strain with a different dominant fur color is used to generate pseudopregnant foster mothers.

Transgenic animal models are fundamentally important for modern biomedical research. The incorporation of foreign genes into early mouse or rat embryos is ...

Transgenic animals are fundamental to modern biomedical research as they allow studies of gene function in living organisms. Various methods of genetic modifications have been applied in animal studies. Here, we present a widely accessible and effective technique that uses lentiviral vectors as a tool for transgene incorporation into the genome of a rat embryo.After human chorionic gonadotropin administration, mate five-week-old Wistar female rats one-to-one with sexually fertile three to 10-month-old Wistar males. At eight to 10 a.m. the next morning, check the females for the presence of a vaginal plug and harvest the oviducts from the females with a mating plug by no later than 10 a.m.into a collection dish containing pre-warmed M2 medium. When all of the oviducts have been collected, transfer the tissues into a 35 millimeter dish containing pre-warmed M2 medium supplemented with 0.5 milligrams per milliliter of hyaluronidase from bovine testes and place the dish under a stereo microscope. Use fine forceps to open the walls of the oviduct and press the ampulla until the embryos are freed.To facilitate the release of the embryos from the cumulus cells, use a glass transfer pipette connected to a mouth-operated aspirator tube to gently pipette the embryos up and down. When all of the embryos have been released, wash the cells a few times in fresh M2 medium to remove the hyaluronidase and cellular debris. Transfer the embryos into individual 50 microliter drops of pre-equilibrated M16 medium covered by mineral oil in a 60 millimeter dish.Then place the dish into a humidified 37 degree Celsius incubator with a 5%carbon dioxide atmosphere until their injection. For lentiviral vector microinjection under the zona pellucida of the one-cell stage embryos, use a pipette puller to prepare microinjection borosilicate glass capillaries with a filament. After every time the filament is changed or a new glass capillary is used, run a Ramp test to set the optimal parameters.Next, use a microloader tip to load approximately two microliters of freshly thawed lentiviral solution per microinjection pipette under a biosafety laminar flow hood. Add a 100 microliter drop of M2 medium to the center of the lid from a 60 millimeter Petri dish. Cover the medium with mineral oil and mount the holding pipette and the virus loaded microinjection capillary onto a micromanipulator.Place the microinjection dish under an inverted microscope and transfer 15 to 20 one-cell stage embryos into the M2 drop in the microinjection dish. Capture one embryo with the holding pipette and use the 400 times magnification and the glass capillary to inject the lentiviral solution under the zona pellucida into the perivitelline space holding the capillary under the zona pellucida for a moment after the virus has been delivered. When all of the embryos have been injected, use a fine pipette to return the injected cells to the culture dish and return the dish to the cell culture incubator until their implantation.To prepare the foster mothers for the embryo transfer, mate sexually mature Sprague-Dawley females with vasectomized males and check the females the next morning for a vaginal plug. After confirming a lack of response to pedal reflex in the anesthetized females with a viable plug, apply ointment to the animal's eyes and shave the fur from the back of each animal. Place the first rat in the prone position on a clean surface on a heating pad under a surgical microscope.Cover the rat with a sterile drape with a small hole cut over the lower back and make an approximately two centimeter skin incision parallel to the lumbar vertebral column. Use sharp scissors to make a cut in the abdominal wall and use forceps to grasp an ovarian fat pad. Pull the ovary and oviduct out of the abdominal cavity onto a piece of 0.9%sodium chloride soaked gauze.Load M2 medium, three bubbles of air, and the embryos into a transfer capillary. Use microscissors to make a small incision into the oviduct between the infundibulum and ampulla and insert the tip of the transfer pipette into the incision. Gently expel the embryos and air bubbles into the oviduct, then use blunt forceps to place the reproductive tract back into the abdominal cavity.Suture the abdominal wall with polyglycolic acid absorbable sutures and close the skin incision with wound clips and place the animal in a clean cage on a warming plate with monitoring until full recumbency. To vasectomize potential mates, after preparing the male rat for surgery as demonstrated, use 70%ethanol and a surgical scrub to disinfect the skin over the testes. Gently press the abdomen to expose the testes in the scrotal sac and cover the rat with a sterile drape with a small hole over the surgical site and use scrotal scissors to make a 0.5 centimeter incision in the middle of the sac.Carefully push the testis to the left and locate the vas deferens between the testis and midline as a white duct with a single blood vessel. Use watchmaker's forceps to gently pull the vas deferens out of the scrotal sac and holding the vessel with forceps, use fine scissors to remove a one centimeter fragment from the duct. Repeat the procedure for the second testis as just demonstrated and close the skin with polyglycolic acid absorbable sutures.Then place the rat into a clean cage on a warming plate with monitoring until full recumbency. In this representative experiment in which single embryos were injected multiple times, eight rats were born from embryos that were injected two times, three of which were confirmed to carry the transgene. One of the founders did not transfer the transgene to offspring and three foster females were used for each experimental setup.The chosen approach allowed the generation of stable transgenic rat lines that expressed the TDP-43-eGFP fusion protein under the control of the neuronal synapse in one promoter throughout the central nervous system. Lentivirus-based transgenesis resulted in a single copy insertion of the transgene as demonstrated by quantitative PCR. When this method was used for other lentiviral vectors, an approximately 90%survival rate was observed.The percentage of embryos that survived the pronuclear injections was significantly lower. Overall, these results suggest that pregnant female rats can be used as foster mothers with a comparable efficiency. Notably, the numerical data that were analyzed for individual rounds of microinjection indicated that the effectiveness of implantation depended directly on the number of injections into one embryo and indirectly on the viral load.The use of lentiviral vectors guarantees the genomic integration and transmission of the transgene and facilitates a high survival rate of the micromanipulated embryos even when multiple subdermal injections are performed. This procedure may be effectively applied to other species and can be considered an alternative for conventional transgenesis.

generation-of-transgenic-rats-using-a-lentiviral-vector-approach

Research

JoVE Journal

Bioengineering

A Cre-Lox P Recombination Approach for the Detection of Cell Fusion In Vivo

The ability of two or more cells of the same type to fuse has been utilized in metazoans throughout evolution to form many complex organs, including skeletal muscle, bone and placenta. Contemporary studies demonstrate fusion of cells of the same type confers enhanced function. For example, when the trophoblast cells of the placenta fuse to form the syncytiotrophoblast, the syncytiotrophoblast is better able to transport nutrients and hormones across the maternal-fetal barrier than unfused trophoblasts1-4. More recent studies demonstrate fusion of cells of different types can direct cell fate. The "reversion" or modification of cell fate by fusion was once thought to be limited to cell culture systems. But the advent of stem cell transplantation led to the discovery by us and others that stem cells can fuse with somatic cells in vivo and that fusion facilitates stem cell differentiation5-7. Thus, cell fusion is a regulated process capable of promoting cell survival and differentiation and thus could be of central importance for development, repair of tissues and even the pathogenesis of disease.
Limiting the study of cell fusion, is lack of appropriate technology to 1) accurately identify fusion products and to 2) track fusion products over time. Here we present a novel approach to address both limitations via induction of bioluminescence upon fusion (Figure 1); bioluminescence can be detected with high sensitivity in vivo8-15. We utilize a construct encoding the firefly luciferase (Photinus pyralis) gene placed adjacent to a stop codon flanked by LoxP sequences. When cells expressing this gene fuse with cells expressing the Cre recombinase protein, the LoxP sites are cleaved and the stop signal is excised allowing transcription of luciferase. Because the signal is inducible, the incidence of false-positive signals is very low. Unlike existing methods which utilize the Cre/LoxP system16, 17, we have incorporated a "living" detection signal and thereby afford for the first time the opportunity to track the kinetics of cell fusion in vivo.
To demonstrate the approach, mice ubiquitously expressing Cre recombinase served as recipients of stem cells transfected with a construct to express luciferase downstream of a floxed stop codon. Stem cells were transplanted via intramyocardial injection and after transplantation intravital image analysis was conducted to track the presence of fusion products in the heart and surrounding tissues over time. This approach could be adapted to analyze cell fusion in any tissue type at any stage of development, disease or adult tissue repair.

A Cre-Lox P Recombination Approach for the Detection of Cell Fusion In Vivo

A method to track cell fusion in living organisms over time is described. The approach utilizes Cre-LoxP recombination to induce luciferase expression upon cell fusion. The luminescent signal generated can be detected in living organisms using biophotonic imaging systems with a sensitivity of detection of &tilde;1,000 cells in peripheral tissues.

The ability of two or more cells of the same type to fuse has been utilized in metazoans throughout evolution to form many complex organs, including ...

Generation of Shear Adhesion Map Using SynVivo Synthetic Microvascular Networks

Cell/particle adhesion assays are critical to understanding the biochemical interactions involved in disease pathophysiology and have important applications in the quest for the development of novel therapeutics. Assays using static conditions fail to capture the dependence of adhesion on shear, limiting their correlation with in vivo environment. Parallel plate flow chambers that quantify adhesion under physiological fluid flow need multiple experiments for the generation of a shear adhesion map. In addition, they do not represent the in vivo scale and morphology and require large volumes (~ml) of reagents for experiments. In this study, we demonstrate the generation of shear adhesion map from a single experiment using a microvascular network based microfluidic device, SynVivo-SMN. This device recreates the complex in vivo vasculature including geometric scale, morphological elements, flow features and cellular interactions in an in vitro format, thereby providing a biologically realistic environment for basic and applied research in cellular behavior, drug delivery, and drug discovery. The assay was demonstrated by studying the interaction of the 2 &#181;m biotin-coated particles with avidin-coated surfaces of the microchip. The entire range of shear observed in the microvasculature is obtained in a single assay enabling adhesion vs. shear map for the particles under physiological conditions.

Flow chambers used in adhesion experiments typically consist of linear flow paths and require multiple experiments at different flow rates to generate a shear adhesion map. SynVivo-SMN enables the generation of shear adhesion map using a single experiment utilizing microliter volumes resulting in significant savings in time and consumables.

Cell/particle adhesion assays are critical to understanding the biochemical interactions involved in disease pathophysiology and have important ...

Characterization of Complex Systems Using the Design of Experiments Approach: Transient Protein Expression in Tobacco as a Case Study

Plants provide multiple benefits for the production of biopharmaceuticals including low costs, scalability, and safety. Transient expression offers the additional advantage of short development and production times, but expression levels can vary significantly between batches thus giving rise to regulatory concerns in the context of good manufacturing practice. We used a design of experiments (DoE) approach to determine the impact of major factors such as regulatory elements in the expression construct, plant growth and development parameters, and the incubation conditions during expression, on the variability of expression between batches. We tested plants expressing a model anti-HIV monoclonal antibody (2G12) and a fluorescent marker protein (DsRed). We discuss the rationale for selecting certain properties of the model and identify its potential limitations. The general approach can easily be transferred to other problems because the principles of the model are broadly applicable: knowledge-based parameter selection, complexity reduction by splitting the initial problem into smaller modules, software-guided setup of optimal experiment combinations and step-wise design augmentation. Therefore, the methodology is not only useful for characterizing protein expression in plants but also for the investigation of other complex systems lacking a mechanistic description. The predictive equations describing the interconnectivity between parameters can be used to establish mechanistic models for other complex systems.

We describe a design of experiments approach that can be used to determine and model the influence of transgene regulatory elements, plant growth and development parameters, and incubation conditions on the transient expression of monoclonal antibodies and reporter proteins in plants.

Plants provide multiple benefits for the production of biopharmaceuticals including low costs, scalability, and safety. Transient expression offers the ...

Lipid Bilayer Vesicle Generation Using Microfluidic Jetting

Bottom-up synthetic biology presents a novel approach for investigating and reconstituting biochemical systems and, potentially, minimal organisms. This emerging field engages engineers, chemists, biologists, and physicists to design and assemble basic biological components into complex, functioning systems from the bottom up. Such bottom-up systems could lead to the development of artificial cells for fundamental biological inquiries and innovative therapies1,2. Giant unilamellar vesicles (GUVs) can serve as a model platform for synthetic biology due to their cell-like membrane structure and size. Microfluidic jetting, or microjetting, is a technique that allows for the generation of GUVs with controlled size, membrane composition, transmembrane protein incorporation, and encapsulation3. The basic principle of this method is the use of multiple, high-frequency fluid pulses generated by a piezo-actuated inkjet device to deform a suspended lipid bilayer into a GUV. The process is akin to blowing soap bubbles from a soap film. By varying the composition of the jetted solution, the composition of the encompassing solution, and/or the components included in the bilayer, researchers can apply this technique to create customized vesicles. This paper describes the procedure to generate simple vesicles from a droplet interface bilayer by microjetting.

Microfluidic jetting against a droplet interface lipid bilayer provides a reliable way to generate vesicles with control over membrane asymmetry, incorporation of transmembrane proteins, and encapsulation of material. This technique can be applied to study a variety of biological systems where compartmentalized biomolecules are desired.

Bottom-up synthetic biology presents a novel approach for investigating and reconstituting biochemical systems and, potentially, minimal organisms. This ...

Generation and Grafting of Tissue-engineered Vessels in a Mouse Model

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. The current protocol presents an efficient and reproducible strategy in which functional tissue engineered vessel grafts can be generated using partially induced pluripotent stem cell (PiPSC) from human fibroblasts. We designed a decellularized vessel scaffold bioreactor, which closely mimics the matrix protein structure and blood flow that exists within a native vessel, for seeding of PiPSC-endothelial cells or smooth muscle cells prior to grafting into mice. This approach was demonstrated to be advantageous because immune-deficient mice engrafted with the PiPSC-derived grafts presented with markedly increased survival rate 3 weeks after surgery. This protocol represents a valuable tool for regenerative medicine, tissue engineering and potentially patient-specific cell-therapy in the near future.

Here, we present a protocol to generate tissue engineered vessel grafts that are functional for grafting into mice by double seeding partially induced pluripotent stem cell (PiPSC) - derived smooth muscle cells and PiPSC - derived endothelial cells on a decellularized vessel scaffold bioreactor.

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. ...

Double Emulsion Generation Using a Polydimethylsiloxane (PDMS) Co-axial Flow Focus Device

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 &#181;m to 50 &#181;m in diameter while using large channels that are robust against fouling and clogging.

Double Emulsion Generation Using a Polydimethylsiloxane PDMS Co-axial Flow Focus Device

Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 &#181;m.

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper ...

Generation of ESC-derived Mouse Airway Epithelial Cells Using Decellularized Lung Scaffolds

Lung lineage differentiation requires integration of complex environmental cues that include growth factor signaling, cell-cell interactions and cell-matrix interactions. Due to this complexity, recapitulation of lung development in vitro to promote differentiation of stem cells to lung epithelial cells has been challenging. In this protocol, decellularized lung scaffolds are used to mimic the 3-dimensional environment of the lung and generate stem cell-derived airway epithelial cells. Mouse embryonic stem cell are first differentiated to the endoderm lineage using an embryoid body (EB) culture method with activin A. Endoderm cells are then seeded onto decellularized scaffolds and cultured at air-liquid interface for up to 21 days. This technique promotes differentiation of seeded cells to functional airway epithelial cells (ciliated cells, club cells, and basal cells) without additional growth factor supplementation. This culture setup is defined, serum-free, inexpensive, and reproducible. Although there is limited contamination from non-lung endoderm lineages in culture, this protocol only generates airway epithelial populations and does not give rise to alveolar epithelial cells. Airway epithelia generated with this protocol can be used to study cell-matrix interactions during lung organogenesis and for disease modeling or drug-discovery platforms of airway-related pathologies such as cystic fibrosis.

This protocol efficiently directs mouse embryonic stem cell-derived definitive endoderm to mature airway epithelial cells. This differentiation technique uses 3-dimensional decellularized lung scaffolds to direct lung lineage specification, in a defined, serum-free culture setting.

Lung lineage differentiation requires integration of complex environmental cues that include growth factor signaling, cell-cell interactions and ...

Calorespirometry: A Powerful, Noninvasive Approach to Investigate Cellular Energy Metabolism

Many cell lines used in basic biological and biomedical research maintain energy homeostasis through a combination of both aerobic and anaerobic respiration. However, the extent to which both pathways contribute to the landscape of cellular energy production is consistently overlooked. Transformed cells cultured in saturating levels of glucose often show a decreased dependency on oxidative phosphorylation for ATP production, which is compensated by an increase in substrate-level phosphorylation. This shift in metabolic poise allows cells to proliferate despite the presence of mitochondrial toxins. In neglecting the altered metabolic poise of transformed cells, results from a pharmaceutical screening may be misinterpreted since the potentially mitotoxic effects may not be detected using model cell lines cultured in the presence of high glucose concentrations. This protocol describes the pairing of two powerful techniques, respirometry and calorimetry, which allows for the quantitative and noninvasive assessment of both aerobic and anaerobic contributions to cellular ATP production. Both aerobic and anaerobic respirations generate heat, which can be monitored via calorimetry. Meanwhile, measuring the rate of oxygen consumption can assess the extent of aerobic respiration. When both heat dissipation and oxygen consumption are measured simultaneously, the calorespirometric ratio can be determined. The experimentally obtained value can then be compared to the theoretical oxycaloric equivalent and the extent of the anaerobic respiration can be judged. Thus, calorespirometry provides a unique method to analyze a wide range of biological questions, including drug development, microbial growth, and fundamental bioenergetics under both normoxic and hypoxic conditions.

This protocol describes calorespirometry, the direct and simultaneous measurement of both heat dissipation and respiration, which provides a noninvasive approach to assess energy metabolism. This technique is used to assess the contribution of both aerobic and anaerobic pathways to energy utilization by monitoring the total cellular energy flow.

Many cell lines used in basic biological and biomedical research maintain energy homeostasis through a combination of both aerobic and anaerobic ...

In Silico Modeling Method for Computational Aquatic Toxicology of Endocrine Disruptors: A Software-Based Approach Using QSAR Toolbox

Computational analyses of toxicological processes enables high-throughput screening of chemical substances and prediction of their endpoints in biological systems. In particular, quantitative structure-activity relationship (QSAR) models have been increasingly applied to assess the environmental effects of a plethora of toxic materials. In recent years, some more highlighted types of toxicants are endocrine disruptors (EDs, which are chemicals that can interfere with any hormone-related metabolism). Because EDs may significantly affect animal development and reproduction, rapidly predicting the adverse effects of EDs using in silico techniques is required. This study presents an in silico method to generate prediction data on the effects of representative EDs in aquatic vertebrates, particularly fish species. The protocol describes an example utilizing the automated workflow of the QSAR Toolbox software developed by the Organization for Economic Co-operation and Development (OECD) to enable acute ecotoxicity predictions of EDs. As a result, the following are determined: (1) calculation of the numerical correlations between the concentration for 50% of lethality (LC50) and octanol-water partition coefficient (Kow), (2) output performances in which the LC50 values determined in experiments are compared to those generated by computations, and (3) the dependence of estrogen receptor binding affinity on the relationship between Kow and LC50.

Quantitative structure-activity relationship (QSAR) modeling is a representative bioinformatics-assisted method in toxicological screening. This protocol demonstrates how to computationally assess the risks of endocrine disruptors (EDs) in aquatic environments. Utilizing the OECD QSAR Toolbox, the protocol implements an in silico assay for analyzing toxicity of EDs in fish.

Computational analyses of toxicological processes enables high-throughput screening of chemical substances and prediction of their endpoints in biological ...

Isolation of Adult Human Dermal Fibroblasts from Abdominal Skin and Generation of Induced Pluripotent Stem Cells Using a Non-Integrating Method

Induced pluripotent stem cells (iPSCs) could be considered, to date, a promising source of pluripotent cells for the management of currently untreatable diseases, for the reconstitution and regeneration of injured tissues and for the development of new drugs. Despite all the advantages related to the use of iPSCs, such as the low risk of rejection, the lessened ethical issues, and the possibility to obtain them from both young and old patients without any difference in their reprogramming potential, problems to overcome are still numerous. In fact, cell reprogramming conducted with viral and integrating viruses can cause infections and the introduction of required genes can induce a genomic instability of the recipient cell, impairing their use in clinic. In particular, there are many concerns about the use of c-Myc gene, well-known from several studies for its mutation-inducing activity. Fibroblasts have emerged as the suitable cell population for cellular reprogramming as they are easy to isolate and culture and are harvested by a minimally invasive skin punch biopsy. The protocol described here provides a detailed step-by-step description of the whole procedure, from sample processing to obtain cell cultures, choice of reagents and supplies, cleaning and preparation, to cell reprogramming by the means of a commercial non-modified RNAs (NM-RNAs)-based reprogramming kit. The chosen reprogramming kit allows an effective reprogramming of human dermal fibroblast to iPSCs and small colonies can be seen as early as 24 h after the first transfection, even with modifications with the respect to the standard datasheet. The reprogramming procedure used in this protocol offers the advantage of a safe reprogramming, without the risk of infections caused by viral vector-based methods, reduces the cellular defense mechanisms, and allows the generation of xeno-free iPSCs, all critical features that are mandatory for further clinical applications.

Cell reprogramming requires the introduction of key genes, which regulate and maintain the pluripotent cell state. The protocol described enables the formation of induced pluripotent stem cells (iPSCs) colonies from human dermal fibroblasts without viral/integrating methods but using non-modified RNAs (NM-RNAs) combined with immune evasion factors reducing cellular defense mechanisms.

Induced pluripotent stem cells (iPSCs) could be considered, to date, a promising source of pluripotent cells for the management of currently untreatable ...