Quantification of Circulating Pig-Specific DNA in the Blood of a Xenotransplantation Model
September 22nd, 2020
In this protocol, porcine specific primers were designed, plasmids-containing porcine specific DNA fragments were constructed, and standard curves for quantitation were established. Using species-specific primers, cpsDNA was quantified by qPCR in pig-to-mouse cell transplantation models and pig-to-monkey artery patch transplantation models.
Xenotransplantation is a feasible method to to treat However, effective monitoring of the immune rejection of xenotransplantation is a problem for physicians and the researchers. This protocol is a simple, convenient, low cost and less invasive method to monitor the immune rejection of the xenotransmutation. This technique can be used in xenotransplantation field, including pig-to-human islet transplantation, kidney transplantation, liver transplantation and heart transplantation.
Begin by transferring 500 microliters of blood samples into different micro centrifuge tubes. Add 20 microliters of protease K and 500 microliters of lysis buffer into the tubes. Then thoroughly shake them to mix.
Put the tubes in a water bath at 56 degrees Celsius for 10 minutes, shaking them two to three times during the incubation until the solution becomes clear centrifuge them briefly to remove the liquid beads from the inner wall of the tube covers. Then add 500 microliters of Anhydrous, Ethyl Alcohol, and shake thoroughly. Transfer the mixture into the adsorption column.
Then centrifuge the column for two minutes and discard the waste liquid. Add 800 microliters of rinse solution to each adsorption column, and centrifuge for one minute. leave the columns at room temperature for a few minutes to dry the remaining rinse solution.
Transfer the absorption columns to a clean centrifugal tube. Add 50 microliters of elution buffer to the middle of the adsorption films and place them at room temperature for two to five minutes, then centrifuge them for one minute. Prepare the PCR master mix according to manuscript directions, then add 23 microliters of the mix into each 0.6 milliliter micro centrifuge tube.
Add two microliters of genomic DNA to each tube and carefully Cabot. Then briefly mix and centrifuge. Place the tubes in a PCR cycler and start the amplification.
When the reaction is finished perform Agarose electrophoresis. Add 1.2 grams of Agarose into a flask containing a hundred millimeters of TAE and boil it for five minutes in the microwave. Once the Agarose has cooled to approximately 70 degrees Celsius, add five microliters of nucleic acid dye into the flask, slowly, pour it into the plate and leave it at room temperature until it solidifies into a gel.
Add five microliters of each sample and 2-Log DNA Ladder or DNA Marker 1, into the wells of the Agarose gel and electrophoresis at 120 million pier until the bands are separated. Visualize the gel with an ultraviolet imager. After performing transformation as described in the text manuscript, verify the plasmids by double restriction enzyme digestion with EcoR I and Bam HI.Separate the digested products with 1%Agarose electrophoresis and expose the gel to UV light.
Dilute the concentrated plasmid with the fragment of porcine DNA to two times 10 to the 11th copies per milliliter for the starting standard solution, Using double distilled water. To establish a standard curve, prepare a qPCR master mix, as described in the text manuscript and add 40 microliters of the mix into each tube of an eight-tube strip. Add 10 microliters of standard DNA of different concentrations, cap the tubes then briefly mix and centrifuge them.
Place the tubes in the qPCR machine and perform the amplification. Use EDTA tubes to collect blood samples of about 400 microliters from the pig-to-monkey artery patch models, or 100 microliters from the pig-to-mouse cell transplantation models. Then transfer the samples to 1.5 milliliter centrifuge tubes.
Remove the blood cells from the blood samples by centrifugation at low temperature and high speed. Transfer the supernatant to a new 1.5 milliliters centrifuge tube and remove the cell debris by centrifugation at 16, 000 times G for 10 minutes. Transfer the supernatant to a new 1.5 milliliter centrifuge tube and extract the circulating DNA using a commercial serum while circulating DNA extraction kit.
Condense the volume of circulating DNA to 40 microliters and store it at negative 20 degrees Celsius. Perform qPCR to quantify the circulating pig-specific DNA. Porcine-specific primers were designed and used to quantify circulating pig-specific DNA by qPCR, in pig-to-mouse cell transplantation models and pig-to-monkey artery patch, transplantation models.
Agarose electrophoresis was used to isolate amplified DNA fragments. Using PCR, the primers-specific for amplified porcine genomic DNA were identified. Next, species specificities of these primers in the cohort of monkey or human genomic DNA or in the cohort of mouse genomic DNA, were confirmed.
Finally two species-specific primers, were used to amplify pig DNA in the pig-to-monkey artery patch and pig to mouse, cell transplantation models. The most important thing to remember while attempting this protocol, is that contamination of all sorts should be prevented. This technique paves the way for researchers to explore new questions within xenotransplantation because it is a simple low-cost and non invasive method to monitor the immune rejection of xenotransplantation.
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Overview
This protocol outlines a method for monitoring immune rejection in xenotransplantation using porcine specific primers and qPCR. It is designed to be simple, cost-effective, and minimally invasive.
Key Study Components
Area of Science
- Xenotransplantation
- Immunology
- Genetic Engineering
Background
- Xenotransplantation involves transplanting organs or tissues from one species to another.
- Monitoring immune rejection is crucial for the success of xenotransplants.
- Current methods may be invasive or costly.
- This protocol aims to provide a more accessible monitoring technique.
Purpose of Study
- To develop a method for quantifying porcine DNA in recipient models.
- To facilitate the monitoring of immune responses in xenotransplantation.
- To improve the feasibility of xenotransplantation in clinical settings.
Methods Used
- Designing porcine specific primers.
- Constructing plasmids containing porcine DNA fragments.
- Establishing standard curves for DNA quantitation.
- Using qPCR to quantify cpsDNA in various transplantation models.
Main Results
- Successful quantification of porcine DNA in pig-to-mouse and pig-to-monkey transplantation models.
- Establishment of reliable standard curves for accurate measurement.
- Demonstration of the method's effectiveness in monitoring immune rejection.
Conclusions
- The protocol provides a low-cost and less invasive method for monitoring xenotransplantation.
- It has potential applications in various types of organ transplantation.
- This approach may enhance the understanding of immune responses in xenotransplantation.
Frequently Asked Questions
Executive Industry Relevance
Monitoring immune rejection in xenotransplantation remains a critical challenge for preclinical development and translational decision-making. A non-invasive, qPCR-based method for quantifying circulating pig-specific DNA enables early detection of graft injury and immune activation. This approach supports mechanistic de-risking by providing a translational biomarker linked to xenograft viability, informing go/no-go decisions in organ replacement pipelines.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of xenograft rejection mechanisms through longitudinal tracking of species-specific DNA release.
- Operational Value: Provides a standardized, quantifiable readout for evaluating immunomodulatory interventions in preclinical models.
- Predictive Value: Supports target validation by correlating circulating DNA levels with immune-mediated graft damage, reducing false-positive therapeutic leads.
Screening & Assay Development
- Assay Readiness: Establishes a reproducible qPCR workflow with species-specific primers and standard curves for accurate cpsDNA quantification across models.
- Scalability: Compatible with high-throughput sample processing from murine and non-human primate xenotransplantation studies.
- Analytical Output: Generates quantitative DNA concentration data enabling dose-response and time-course analysis of graft integrity.
Translational & Preclinical Research
- Disease-Relevant System: Applicable to pig-to-mouse and pig-to-monkey transplantation models, reflecting cross-species immune dynamics relevant to human xenotransplantation.
- Translational Continuity: Circulating DNA serves as a non-invasive biomarker bridge from discovery to preclinical safety assessment.
- Risk-Adjusted Advancement: Enables longitudinal monitoring to inform dosing schedules and immunosuppression efficacy before GLP studies.
Pipeline & Workflow Integration
The method fits within the discovery-to-preclinical continuum by providing a molecular readout of graft status that complements functional and histological endpoints.
- Discovery Biology: Supports hypothesis testing on immune pathways driving xenograft loss through measurable DNA release kinetics.
- Screening: Enables assay standardization for evaluating biologics or small molecules targeting rejection mechanisms.
- Analytics: qPCR-derived cpsDNA quantification offers a sensitive, dynamic range for detecting early graft injury prior to functional decline.
- Translational Research: Biomarker alignment with clinical circulating DNA monitoring strategies enhances predictive confidence for human applications.
- Enterprise Reuse: The qPCR platform can be adapted across xenotransplantation programs (islet, kidney, liver, heart) with primer redesign.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in rejection studies by providing a direct, quantifiable measure of porcine cell death.
- Operational Value: Minimizes animal use through serial blood sampling versus terminal endpoint analysis.
- Strategic Value: Improves capital efficiency by enabling early termination of ineffective immunomodulatory candidates.
- Portfolio Impact: Facilitates risk-stratified advancement based on objective graft integrity metrics.
Implementation Considerations
- Requires expertise in nucleic acid extraction, qPCR optimization, and standard curve generation.
- Dependent on access to qPCR instrumentation, agarose gel validation tools, and contamination-controlled workflows.
- Necessitates cross-team standardization between animal handling, sample processing, and analytical teams for longitudinal consistency.
- Adaptation to alternative model systems requires revalidation of primer specificity and DNA extraction efficiency.
- Practical limitations include potential confounding from non-graft sources of porcine DNA and assay sensitivity at low rejection stages.
