The Regenerative Potential of Notochordal Cells in a Nucleus Pulposus Explant

STUDY DESIGN: In vitro disk explant culture. OBJECTIVE: Notochordal cells (NCs) have been shown to upregulate matrix production by nucleus pulposus (NP) cells in coculture. To examine the translation of these in vitro results to a nativelike setting, the regenerative potential of NCs injected into NP tissue was assessed in this study. METHODS: NP explants were cultured after injection with NCs in phosphate-buffered saline (PBS) or with PBS alone (sham). At days 0 and 42, cell viability and morphology, water, DNA, sulfated glycosaminoglycan and hydroxyproline content, and gene expression of anabolic markers were analyzed. RESULTS: NCs remained viable during culture, but their morphology changed. The biochemical content remained unchanged, except for the DNA content in the NC group. Overall ACAN expression remained unchanged, whereas COL2A1 decreased during culture. CONCLUSIONS: No overall anabolic response was observed when NCs were injected into NP explants. NCs were found to survive but did not display the typical NC morphology by the end of the culture period.