Circular DNA Loops Boost Non-Viral Gene Therapy

For the past decade, scientists have sought effective ways to edit the genetic code of hematopoietic stem and progenitor cells (HSPCs)—the precursors to all blood cells. While non-viral DNA delivery methods exist, they have largely been limited to inserting short snippets of DNA, restricting their use to minor corrections rather than full gene replacements. A new study expands these horizons using kilobase-long circular single-stranded DNA (CssDNA).

By combining these long circular templates with TALEN technology—a tool that acts like molecular scissors—the researchers achieved high rates of gene insertion. Crucially, this method allows for the delivery of much larger genetic payloads than previous non-viral techniques.

The benefits extend beyond capacity. When tested in a female NCG murine model, cells edited with CssDNA outperformed those edited with Adeno-associated viruses (AAV). The CssDNA-edited cells displayed a higher aptitude for engraftment, meaning they successfully implanted and maintained the genetic changes within the host.

The researchers attribute this success to the physiological state of the edited cells. The CssDNA process preserved more 'primitive' stem cells in a quiescent, or resting, metabolic state. Furthermore, these cells exhibited elevated levels of bone marrow niche adhesion markers—proteins that help them anchor securely. These findings suggest CssDNA could become a scalable, universal standard for safer gene therapies.