Cellular Reprogramming With Transient Plasmids for Stable iPSCs
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Solution Overview
Problem
Existing methods for generating induced pluripotent stem cells (iPSCs) using integrating viral systems result in permanent genomic changes and potential for exogenous gene reactivation, leading to inconsistencies and increased risk of tumors, necessitating extensive screening and limiting therapeutic applications.
Innovation Solution
A transient and temporal expression system using a combinational plasmid vector system that minimizes exogenous gene integration, inducing reprogramming in non-pluripotent cells to generate iPSCs with 'naïve' or 'grounded' pluripotency, ensuring genetic stability and high clonality, and allowing for targeted genomic editing and redifferentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integrating viral systems (retroviral or lentiviral) are used to express reprogramming factors, then reprogramming efficiency is improved, but permanent genomic changes and insertional mutagenesis occur
Solution Approach 1:
The patent extracts the harmful integrating capability from the viral system while retaining the beneficial reprogramming function. It uses non-integrating viral vectors (adenovirus, Sendai virus) or plasmid-based systems that deliver reprogramming factors without permanently integrating into the host genome, thus eliminating insertional mutagenesis while maintaining reprogramming efficiency.
Solution Approach 2:
The patent employs transient expression systems where the reprogramming factors are expressed only during a limited time window. The viral vectors or plasmids are designed to be eliminated from the cell after delivering their reprogramming cargo, leaving no permanent genetic footprint. This transient nature ensures that the reprogramming process occurs efficiently without long-term genomic alterations.
2Reliability
If non-integrating viral systems (adenovirus, Sendai virus, EBV episomal vector) are used, then genomic stability is improved, but reprogramming efficiency decreases
Solution Approach 1:
The patent combines the advantages of different non-integrating systems by using composite vector designs that incorporate strong promoters, optimized transgene expression cassettes, and enhanced delivery mechanisms. This merging approach achieves high reprogramming efficiency while maintaining genomic stability, overcoming the limitations of individual non-integrating systems.
Solution Approach 2:
The patent optimizes various parameters of the non-integrating systems including viral titers, transfection conditions, culture media composition, and timing of reprogramming factor expression. By carefully controlling these parameters, the system achieves efficient reprogramming without requiring permanent genomic integration, thus maintaining both high productivity and reliability.
3Reliability
If extensive screening of iPSC clones is performed to identify stable clones, then therapeutic safety is improved, but time and resource consumption increase
Solution Approach 1:
The patent incorporates preliminary screening markers and selection mechanisms into the reprogramming process itself. By using vectors with selectable markers or cells with inherent stable traits, the system enables early identification and selection of stable iPSC clones during the reprogramming process, eliminating the need for extensive post-generation screening and significantly reducing time and resource consumption.
4Productivity
If integrating systems are used for iPSC generation, then reprogramming can be achieved, but exogenous gene reactivation may occur post-differentiation
Solution Approach 1:
The patent extracts the reprogramming function from the host genome by using non-integrating delivery systems. The reprogramming factors are delivered transiently and then eliminated, ensuring that no exogenous genes remain in the cell to be reactivated during subsequent differentiation. This approach maintains reprogramming achievement while completely eliminating the risk of exogenous gene reactivation.
Data Source
AI summary
Provided are methods and compositions for inducing the reprogramming of a non-pluripotent to an iPSC having desirable properties using a vector system providing transient and temporal expression of transgenes that are short-lived. Also provided are reprogramming cells and iPSC populations or clonal cell lines using the provided reprogramming methods and compositions. Further provided are genome-engineered iPSCs and derived cells redifferentiated therefrom to comprise targeted editing involving insertions and deletions in one or more selected genomic loci.