Rejuvenation of THY1+ nucleus pulposus-derived stem cells promotes intervertebral disc regeneration through FGF10-FGFR1-CREB pathway and mitochondrial fission.

INTRODUCTION: Intervertebral disc degeneration (IVDD), a major cause of low back pain, is primarily characterized by compromised regeneration ability of nucleus pulposus-derived stem cells (NPSCs) owing to their senescence. The role of NPSCs as major regenerative cells in IVDD is garnering attention. However, the drivers and mechanisms of NPSCs reactivation and regeneration are poorly understood, limiting the development of targeted therapies. The fibroblast growth factor (FGF) family has shown increasing promise in tissue regeneration; however, the key factors involved in IVDD remain unclear.
OBJECTIVES: To elucidate the regenerative driver of NPSCs and the underlying anti-senescence mechanism to provide a potential therapeutic strategy.
METHODS: Single cell RNA sequencing (scRNA-seq) and bulk RNA sequencing were performed to identify the key NPSCs clusters and regenerative drivers in IVDD. Clinical IVDD samples were collected to determine the alterations in the NPSCs subset proportion and the expression of regeneration factors. Further, NPSCs senescence and in vivo models were used to investigate the specific mechanisms and therapeutic effects.
RESULTS: Thy-1 membrane glycoprotein (THY1)+ NPSCs, which are depleted in IVDD, were the key cells involved in intervertebral disc degeneration based on scRNA-seq. THY1+ NPSCs exhibited stemness and regeneration potential. The RNA-seq analysis of senescent THY1+ NPSCs indicated fibroblast growth factor 10 (FGF10) as a pivotal rejuvenation factor. Multiplex fluorescence staining demonstrated diminished FGF10 expression in IVDD. FGF10 mitigated THY1+ NPSCs senescence by interacting with fibroblast growth factor receptor 1 (FGFR1). The FGF10-FGFR1 axis inhibited CREB phosphorylation and further alleviated ARG2-DRP1-related mitochondrial fission, reversing THY1+ NPSC senescence. Inhibition of CREB and downregulation of ARG2 regulate cellular senescence via modulation of mitochondrial fission. The transplantation of FGF10-overexpression NPSCs prominently alleviated nucleus pulposus degeneration and demonstrated regeneration potential in vivo.
CONCLUSION: Our findings elucidate the pivotal roles of THY1+ NPSCs and FGF10 in intervertebral disc regeneration and NPSCs activation, respectively, contributing to the development of regenerative therapeutic strategies for IVDD.