Partial Reprogramming As An Emerging Strategy for Safe Induced Cell Generation and Rejuvenation

Background: Conventional cell reprogramming involves converting a somatic cell line into induced pluripotent stem cells (iPSC), which subsequently can be re-differentiated to specific somatic cell types. Alternatively, partial cell reprogramming converts somatic cells into other somatic cell types by transient expression of pluripotency genes thus generating intermediates that retain their original cell identity, but are responsive to appropriate cocktails of specific differentiation factors. Additionally, biological rejuvenation by partial cell reprogramming is an emerging avenue of research. Objective: Here, we will briefly review the emerging information pointing to partial reprogramming as a suitable strategy to achieve cell reprogramming and rejuvenation, bypassing cell dedifferentiation. Methods: In this context, regulatable pluripotency gene expression systems are the most widely used at present to implement partial cell reprogramming. For instance, we have constructed a regulatable bidirectional adenovector expressing Green Fluorescent Protein and oct4, sox2, klf4 and c-myc genes (known as the Yamanaka genes or OSKM). Results: Partial cell reprogramming has been used to reprogram fibroblasts to cardiomyocytes, neural progenitors and neural stem cells. Rejuvenation by cyclic partial reprogramming has been achieved both in vivo and in cell culture using transgenic mice and cells expressing the OSKM genes, respectively, controlled by a regulatable promoter. Conclusion: Partial reprogramming emerges as a powerful tool for the genesis of iPSC-free induced somatic cells of therapeutic value and for the implementation of in vitro and in vivo rejuvenation keeping cell type identity unchanged.