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Methods are described for the generation of large amounts of recombinant adenoviruses, which can then be used to transduce the native rodent urothelium allowing for expression of transgenes or downregulation of endogenous gene products.
In addition to forming a high-resistance barrier, the urothelium lining the renal pelvis, ureters, bladder, and proximal urethra is hypothesized to sense and transmit information about its environment to the underlying tissues, promoting voiding function and behavior. Disruption of the urothelial barrier, or its sensory/transducer function, can lead to disease. Studying these complex events is hampered by lack of simple strategies to alter gene and protein expression in the urothelium. Methods are described here that allow investigators to generate large amounts of high-titer adenovirus, which can then be used to transduce rodent urothelium with high efficiency, and in a relatively straightforward manner. Both cDNAs and small interfering RNAs can be expressed using adenoviral transduction, and the impact of transgene expression on urothelial function can be assessed 12 h to several days later. These methods have broad applicability to studies of normal and abnormal urothelial biology using mouse or rat animal models.
The urothelium is the specialized epithelium that lines the renal pelvis, ureters, bladder, and proximal urethra1. It comprises three strata: a layer of highly differentiated and polarized often bi-nucleate umbrella cells, whose apical surfaces are bathed in urine; an intermediate cell layer with a population of bi-nucleate transit-amplifying cells that can give rise to superficial umbrella cells in response to their acute loss; and a single layer of basal cells, a subset of which function as stem cells that can regenerate the entirety of the urothelium in response to chronic injury. Umbrella cells are chiefly responsible for forming the high-resistance urothelial barrier, components of which include an apical membrane (rich in cholesterol and cerebrosides) with low permeability to water and solutes, and a high-resistance apical junctional complex (comprised of tight junctions, adherens junctions, desmosomes, and an associated actomyosin ring)1. Both the apical surface of the umbrella cell and its junctional ring expand during bladder filling and return to their pre-filled state rapidly after voiding1,2,3,4,5. In addition to its role in barrier function, the urothelium is also hypothesized to have sensory and transducer functions that allow it to sense changes in the extracellular milieu (e.g., stretch) and transmit this information via release of mediators (including ATP, adenosine, and acetylcholine) to underlying tissues, including suburothelial afferent nerve processes6,7,8. Recent evidence of this role is found in mice lacking urothelial expression of both Piezo1 and Piezo2, which results in altered voiding function9. Additionally, rats overexpressing the tight-junction pore-forming protein CLDN2 in the umbrella cell layer develop inflammation and pain analogous to that seen in patients with interstitial cystitis10. It is hypothesized that disruption of urothelial sensory/transducer or barrier function may contribute to several bladder disorders6,11.
A better understanding of the biology of the urothelium in normal and disease states depends on the availability of tools that will allow investigators to readily downregulate endogenous gene expression or allow for the expression of transgenes in the native tissue. While one approach to downregulate gene expression is to generate conditional urothelial knockout mice, this approach depends on the availability of mice with floxed alleles, is labor intensive, and can take months to years to complete12. Not surprisingly then, investigators have developed techniques to transfect or transduce the urothelium, which can lead to results on a shorter time scale. Published methods for transfection include the use of cationic lipids13, anti-sense phosphorothioated oligodeoxynucleotides14, or antisense nucleic acids tethered to the HIV TAT protein penetrating 11-mer peptide15. However, the focus of this protocol is on the use of adenoviral-mediated transduction, a well-studied methodology that is efficient at gene delivery to a broad range of cells, has been tested in numerous clinical trials, and most recently was used to deliver the cDNA encoding the COVID-19 capsid protein to recipients of one variant of the COVID-19 vaccine16,17. For a more thorough description of the adenovirus life cycle, adenoviral vectors, and clinical applications of adenoviruses, the reader is directed to reference17.
An important milestone in the use of adenoviruses to transduce the urothelium, was a report by Ramesh et al. that showed short pretreatments with detergents, including N-dodecyl-β-D-maltoside (DDM) dramatically enhanced transduction of the urothelium by an adenovirus encoding β-galactosidase18. Using this proof-of-principle study as a guide, adenoviral-mediated transduction of the urothelium has now been used to express a variety of proteins, including Rab-family GTPases, guanine-nucleotide exchange factors, myosin motor fragments, pore-forming tight junction-associated claudins, and ADAM1710,19,20,21,22. The same approach was adapted to express small interfering RNAs (siRNA), the effects of which were rescued by co-expressing siRNA-resistant variants of the transgene22. The protocol described here includes general methods to generate large amounts of highly concentrated adenovirus, a requirement for these techniques, as well adaptations of the methods of Ramesh et al.18 to express transgenes in the urothelium with high efficiency.
Experiments involving the generation of adenoviruses, which requires BSL2 certification, were performed under approval from the University of Pittsburgh Environmental Health and Safety offices and the Institutional Biosafety Committee. All animal experiments performed, including adenoviral transduction (which requires ABSL2 certification), were done in accordance with relevant guidelines/regulations of the Public Health Service Policy on Humane Care and Use of Laboratory Animals and the Animal Welfare Act, and under the approval of the University of Pittsburgh Institutional Animal Care and Use Committee. Gloves, eye protection, and appropriate garb are worn for all procedures involving recombinant viruses. Any liquid or solid waste should be disposed of as described below. The bedding of the animals post transduction, and any resulting animal carcasses, should be treated as biohazardous materials and disposed of according to institutional policies.
1. Preparation of high-titer adenovirus stocks
NOTE: Effective transduction of rodent bladders depends on the use of purified and concentrated viral stocks, typically 1 x 107 to 1 x 108 infectious viral particles (IVP) per µL. This portion of the protocol is focused on generating high-titer adenovirus stocks from existing virus preparations. All steps should be performed in a cell culture hood using sterile reagents and tools. While the available strains of adenovirus used today are replication defective, most institutions require approval to use adenoviruses and recombinant DNA. This often includes designation of a cell culture room as a BSL2 approved facility to produce and amplify adenoviruses. Some general considerations include use of masks, eye protection, gloves, and appropriate garb at all stages of virus production and purification. When performing centrifugation, safety caps are recommended if the centrifuge tubes lack tight-fitting caps. All non-disposable materials, including potentially contaminated centrifuge safety caps, bottles, and rotors are treated with an antiviral solution (see Table of Materials), and then rinsed with water or 70% ethanol. Liquid wastes are treated by adding bleach to a final concentration of 10% (v/v). Disposal of these liquid wastes will depend on institutional policies. Solid wastes are typically disposed of in biohazardous waste.
2. Transduction of rodent bladder
NOTE: If new to this technique, it is recommended that the number of animals transduced at one time be limited to 2-4. This can be accomplished by staggering the start times for each animal, particularly during the detergent treatment in step 2.2, and then the virus incubation in step 2.3. Experienced investigators can transduce up to six animals at a time.
Virus preparation
An example of virus purification by density gradient centrifugation is shown in Figure 1A. The light pink band, found at the interface of the loaded cellular material and the 1.25 g/mL CsCl layer, is primarily composed of disrupted cells and their debris (see magenta arrow in Figure 1A). It derives its pinkish color from the small amount of culture medium that is carried over from step 1.5 in the protocol. The virus parti...
While Ramesh et al. were focused on developing strategies to use adenoviral transduction in the treatment of bladder cancer18, more recent reports have demonstrated the utility of these techniques in studying normal urothelial biology/physiology and pathophysiology10,18,19,20,21. The important features of this approach include the follo...
The authors have nothing to disclose.
This work was supported by a pilot project award through P30DK079307 (to M.G.D.), NIH grant R01DK119183 (to G.A. and M.D.C.), NIH grant R01DK129473 (to G.A.), an American Urology Association Career Development award and a Winters Foundation grant (to N.M.), by the Cell Physiology and Model Organisms Kidney Imaging Cores of the Pittsburgh Center for Kidney Research (P30DK079307), and by S10OD028596 (to G.A.), which funded the purchase of the confocal system used to capture some of the images presented in this manuscript.
Name | Company | Catalog Number | Comments |
10 mL pipette | Corning Costar (Millipore Sigma) | CLS4488 | sterile, serological pipette, individually wrapped |
12 mL ultracentrifuge tube | ThermoFisher | 06-752 | PET thinwall ultracentrifuge tube |
15 mL conical centrifuge tube | Falcon (Corning) | 352097 | sterile |
18 G needle | BD | 305196 | 18 G x 1.5 in needle |
20 mL pipette | Corning Costar (Millipore Sigma) | CLS4489 | sterile, serological pipette, individually wrapped |
50 mL conical centrifuge tube | Falcon (Corning) | 352098 | sterile |
5 mL pipette | Corning Costar (Millipore Sigma) | CLS4487 | sterile, serological pipette, individually wrapped |
Cavicide | Henry Schein | 6400012 | Anti-viral solution |
Cell culture dish - 15 cm | Falcon (Corning) | 353025 | sterile, tissue-culture treated (150 mm x 25 mm dish) |
Cell scraper | Sarstedt | 893.1832 | handle length 24 cm, blade length 1.7 cm |
CsCl | Millipore Sigma | C-4306 | Molecular Biology grade ≥ 98% |
DMEM culture medium (high glucose) | Gibco (ThermoFisher) | 11965092 | with 4.5 g/L glucose + L-glutamine + phenol red |
EDTA | Millipore Sigma | EDS | Bioiultra grade ≥ 99% |
Fetal bovine serum | Hyclone (Cytiva) | SH30070.03 | defined serum |
Glass pipette | Fisher Scientific | 13-678-20A | 5.75 in glass pipette, autoclaved |
Glycerol | Millipore Sigma | G-5516 | Molecular Biology grade ≥ 99% |
HEK293 cells | ATCC | CRL-3216 | HEK293T cells are a variant of HEK293 cells that express the SV40 large T-antigen |
Isoflurane | Covetrus | 29405 | |
IV catheter - mouse | Smith Medical Jelco | 3063 | 24 G x 3/4 in Safety IV catheter radiopaque |
IV catheter - rat | Smith Medical Jelco | 3060 | 22 G x 1 in Safety IV catheter radiopaque |
KCl | Millipore Sigma | P-9541 | Molecular Biology grade ≥ 99% |
KH2PO4 | Millipore Sigma | P5655 | Cell culture grade ≥ 99% |
Na2HPO4•7 H2O | Millipore Sigma | 431478 | ≥ 99.99% |
NaCl | Millipore Sigma | S3014 | Molecular Biology grade ≥ 99% |
N-dodecyl-β-D-maltoside | Millipore Sigma | D4641 | ≥ 98% |
Nose cone for multiple animals | custom designed | commercial options include one from Parkland Scientific (RES3200) | |
PD-10 column | GE Healthcare | 17-085-01 | Prepacked columns filled ith Sephadex G-25M |
Penicillin/streptomycin antibiotic (100x) | Gibco (ThermoFisher) | 15070063 | 100x concentrated solution |
Spectrophotometer | Eppendorf | BioPhotometer | |
Stand and clamp | Fisher Scientific | 14-679Q and 05-769-8FQ | available from numerous suppliers |
Sterile filter unit | Fisher Scientific (Nalgene) | 09-740-65B | 0.2 µm rapid-flow filter unit (150 mL) |
Sterile filter unit 0.2 µm (syringe) | Fisher Scientific | SLGV004SL | Millipore Sigma Milex 0.22 µm filter unit that attaches to syringe |
Super speed centrifuge | Eppendorf | 5810R | with Eppendorf F34-6-38 fixed angle rotor (12,000 rpm) |
Syringe (1 mL) | BD | 309628 | 1-mL syringe Luer-lok tip - sterile |
Syringe (3 mL) | BD | 309656 | 3-mL syringe slip tip - sterile |
Table-top centrifuge (low speed) | Eppendorf | 5702 | with swinging bucket rotor |
Transfer pipettes | Fisher Scientific | 13-711-9AM | polyethylene 3.4 mL transfer pipette |
Tris-base | Millipore Sigma | 648310-M | Molecular Biology grade |
TrypLE select protease solution | Gibco (ThermoFisher) | 12604013 | TrypLE express enzyme (1x), no phenol red |
Ultracentrifuge | Beckman Coulter | Optima L-80 XP | with Beckman SW41 rotor (41,000 rpm) |
Vaporizer | General Anesthetic Services, Inc. | Tec 3 | Isoflurane vaporizer |
Vortex Mixer | VWR | 10153-838 | analog vortex mixer |
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