Reversion of passaged nucleus pulposus cells to notochordal-type cells by FoxA2 upregulation

Notochordal cells (NC) have promise as a regenerative therapy for intervertebral disc (IVD) degeneration, but their maintenance in culture remains challenging. The study hypothesis is that nucleus pulposus (NP) cells can undergo reversion to NC-type cells through CRISPR/dCas9 activation of FoxA2. Serial passaging of cells isolated from NP shows loss of FoxA2, Brachyury (T), and Noto expression. Transient FoxA2 overexpression increased the levels of NC biomarkers, keratin, CD24, and SHH in passaged cells. So FoxA2-expressing cells were generated using CRISPR/dCas9-SAM. Analysis showed the presence of some vacuolated cells, elevated NC marker expression of Fox A2, Noto, Brachyury, and keratin and improved in vitro NP tissue formation (determined by quantifying proteoglycan content). TGFβ3 treatment enhanced tissue formation. Injected FoxA2-expressing cells survived and produced NP matrix molecules in an ex vivo bovine IVD injury model. The findings suggest FoxA2-expressing NC-type cells can be generated which may have potential to advance cell-based therapies for disc degeneration.