What did this project achieve?
We now report the development of a novel therapeutic approach that will provide definitive treatment. Our approach starts with obtaining diseased skin cells from patients via a punch biopsy, which is minimally invasive. We then culture these cells in the laboratory and repair the disease-causing mutation of the COL7A1 gene with a state-of-the-art technology called CRISPR. Furthermore, while we repair the pathogenic mutation, we also convert these skin cells into induced pluripotent stem cells (iPSCs). The idea behind the latter is that, in contrast to skin cells, iPSCs can be grown in the laboratory indefinitely. Thus, we can grow a large amount of iPSCs in which the RDEB-causing mutation had been repaired. For the eventual therapeutic application, we will subsequently convert these repaired iPSCs back into skin cells that can be grafted onto the patient for definitive treatment. Once we have obtained correctly gene-edited iPSCs from a patient we can literally grow enough therapeutic skin grafts to cover the entire body! Since our approach started with the patients' own skin cells there will be virtually no immunological complication, allowing successful grafting.
Importantly, we have developed a very efficient way to generate these gene-edited iPSCs. Specifically, we can now combine CRISPR-mediated repair of the pathogenic mutation with reprogramming into iPSCs in 1 integrated step. This allows us to derive these repaired iPSCs from patient skin cells within less than 1 month, which is a most significant improvement over previous approaches that performed a repair of the pathogenic mutation separate from iPSC reprogramming. The main benefit of our accelerated protocol is that it shortens the time the cells are outside the patient’s body by numerous months. This is a tremendous improvement since we know that culturing cells outside the body for too long causes many mutations in the genome, which could have deleterious side effects like the development of cancers. Our approach is very robust as we have already generated 1-step gene repaired and reprogrammed iPSCs from numerous patients that carry different pathogenic mutations. In sum, this accelerated derivation of gene-repaired iPSCs in an unprecedentedly short time will make clinical translation feasible. We hope and expect to be able to bring this therapy, which will be a first-in-man CRISPR-mediated iPSC-based approach, to patients in the near future.