Shared and Compartment-Specific Processes in Nucleus Pulposus and Annulus Fibrosus During Intervertebral Disc...

Area of Science:

• Cellular and Molecular Biology
• Regenerative Medicine
• Orthopedics

Background:

• Intervertebral disc degeneration (IDD) is a complex process involving cellular and molecular changes within the annulus fibrosus (AF) and nucleus pulposus (NP).
• Understanding the specific cell populations and their roles in IDD pathogenesis is crucial for developing targeted therapies.

Purpose of the Study:

• To elucidate the cellular landscape of healthy and degenerated human intervertebral discs (IVDs) using single-cell RNA sequencing (scRNA-seq).
• To identify novel cell subsets and molecular mechanisms driving AF and NP degeneration.
• To uncover potential therapeutic targets for IDD prevention and treatment.

Main Methods:

• Single-cell RNA sequencing (scRNA-seq) was performed on AF and NP tissues from healthy and degenerated human IVDs.
• Computational analysis was used to identify distinct cell populations, their gene expression profiles, and associated biological pathways.

Main Results:

• Depletion of immature cell subsets (fibroblast progenitors, stem cells) was observed in both AF and NP, indicating impaired self-renewal in degenerated discs.
• Increased fibrotic populations were identified in the NP of degenerated discs, suggesting tissue remodeling.
• A novel disease-associated cell subset expressing disease-promoting genes was discovered in degenerated AF, linked to thrombospondin signaling and FOXO1 transcription factor.

Conclusions:

• IDD involves both shared and tissue-specific alterations in AF and NP cell populations.
• Thrombospondin protein influences gene expression related to fibrosis, angiogenesis, and nervous system development in both AF and NP cells.
• The identified cell populations, pathways (e.g., thrombospondin signaling, FOXO1), and molecules represent promising targets for novel IDD therapeutics.