Advances in gene editing are pushing the possibility of raising pigs for organs that may be transplanted into humans with immunosuppression regimens comparable to those now used in human-to-human transplants, coauthors James Butler, MD, and A. Joseph Tector, MD, PhD, stated in an expert opinion in the February issue of the Journal of Thoracic and Cardiovascular Surgery ().
Developments in genome editing could bring new approaches to management of cardiopulmonary diseases, Dr. Butler and Dr. Tector noted. “Recently, cardiac-specific and lung-specific applications have been described, which will allow for the rapid creation of new models of heart and lung disease,” they said. Specifically, they noted gene targeting might eventually offer a way to treat challenging genetic problems “like the heterogeneous nature of nonsquamous cell lung cancer.”
Dr. Butler is with the department of surgery at Indiana University, Indianapolis, and Dr. Tector is with the department of surgery at the University of Alabama at Birmingham.
CRISPR technology has been used in developing multiple gene knockout pigs and neutralizing three separate porcine genes that encode human xenoantigens in a single reaction, leading to efficient methods for creating pigs with multiple genetic modifications.
According to the website of theof MIT and Harvard, Cambridge, Mass., where researchers perfected the system to work in eukaryotes, by using short RNA sequences designed by researchers to guide the system to matching sequences of DNA. When the target DNA is found, Cas9 – one of the enzymes produced by the CRISPR system – binds to the DNA and cuts it, shutting the targeted gene off.
“By facilitating high-throughput model creation, CRISPR has elucidated which modifications are necessary and which are not; despite the ability to alter many loci concurrently, recent evidence has implicated three porcine genes that are responsible for the majority of human-antiporcine humoral immunity,” Dr. Butler and Dr. Tector wrote.
Those genes are the Gal[alpha]1-3 epitope (Gal-alpha), CMAH and B4GaINT2 genes. “Each of these three genes is expressed in pigs but has been evolutionarily silenced in humans,” the coauthors added.
While CRISPR genome editing has yet to reach its full potential, researchers and clinicians should pay attention, according to Dr. Butler and Dr. Tector.
More recent modifications of CRISPR technology have shown promise in not just knocking out or turning off specific genes, but rather guiding directed replacement of genes with researcher-designed substitutes. This can enable permanent transformation of functional genes with altered behavior, according to the Broad Institute website.
Dr. Tector disclosed he has received funding from United Therapeutics and founded Xenobridge with patents for xenotransplantation. Dr. Butler has no relevant financial relationships to disclose.