Oral Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Effects of GDF6 on active protein synthesis by cells of degenerated intervertebral disc (115274)

Vivian Tam 1 , Neha Chopra 2 3 , Stone Sima 3 , Peikai Chen 4 5 , Rakesh Sharma 6 , Danny Chan 1 , Ashish Diwan 2 3 7
  1. School of Biomedical Sciences, The University of Hong Kong , Hong Kong, Hong Kong SAR
  2. Spine Service at St George and Sutherland Clinical School, Sydney, NSW, Australia
  3. Spine Labs, St George and Sutherland Clinical School, Sydney, NSW, Australia
  4. Orthopaedics, The University of Hong Kong - Shenzhen Hospital, Shenzhen , China
  5. The AI and Big Data Lab, University of Hongkong - Shenzhen Hospital, Shenzhen, China
  6. Proteomics and Metabolomics Core, Centre for PanorOmic Sciences, The University of Hong Kong, Hong Kong, Hong Kong SAR
  7. Spinal Unit, Discipline of Orthopaedic Surgery, School of Medicine, University of Adelaide, Adelaide, Australia

Introduction

Intervertebral disc degeneration (IVD) is a leading cause of low back pain, a prevalent musculoskeletal condition characterized by the degradation of nucleus pulposus (NP), annulus fibrosus (AF), and cartilage endplates (EP). Degeneration disrupts the extracellular matrix (ECM), leading to loss of hydration, mechanical integrity, and increased inflammation. Growth Differentiation Factor 6 (GDF6), a member of the bone morphogenetic protein family, has shown promise in promoting cartilage and disc health [1-5]. Despite its potential, the precise mechanisms by which GDF6 influences protein synthesis and ECM remodeling in degenerated IVDs remain unclear. This study aims to evaluate the effects of GDF6 on cellular protein synthesis and secretome profiles using Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC), providing insights into its therapeutic potential.

Methods

A degenerated lumbar IVD specimen (Pfirrmann grade 5) was collected from a 55-year-old female patient undergoing surgery. Cells were isolated from NP, AF, and EP tissues and cultured in SILAC media with and without GDF6 (400 ng/mL). Over an eight-day period, the incorporation of "heavy" isotopically labeled amino acids into newly synthesized proteins was assessed. Mass spectrometry was used to analyze cellular and secreted protein profiles. Proteins were categorized into matrisome (ECM) and non-matrisome groups. Changes in protein synthesis were quantified, and gene-set enrichment analyses were conducted to identify affected pathways (figure 1).

Results

GDF6 treatment modulated protein synthesis in a compartment-specific manner (figure 2 and 3). NP cells displayed decreased synthesis of matrisome proteins, including collagens and proteoglycans, but increased production of ECM stabilizers, including LOX, HAPLN1 and PCOLCE. These proteins are associated with improved ECM hydration and integrity. AF cells demonstrated an upregulation of glycoproteins, such as POSTN and FMOD, known for their roles in ECM reinforcement and anti-inflammatory effects. EP cells showed relatively minimal changes, though an increase in type II collagen production suggested potential ECM stabilization. Secretome analysis revealed significant changes in the extracellular environment (figure 4). In NP and AF cells, GDF6 reduced the secretion of inflammatory markers while increasing ECM-supportive proteins like MFGE8 and IGFBP2. Interestingly, GDF6 treatment also induced genes associated with epithelial-to-mesenchymal transition (EMT) across all compartments, potentially enhancing cellular plasticity and resilience to degeneration.

Discussion

This study highlights the compartment-specific effects of GDF6 in IVD degeneration. By reducing overall protein synthesis while promoting key ECM proteins, GDF6 helps restore hydration and mechanical properties, particularly in NP cells. The modulation of secretome profiles suggests that GDF6 creates a microenvironment conducive to regeneration by reducing fibrosis and inflammation. These findings underscore the potential of GDF6 as a therapeutic agent in targeting early and advanced stages of IVD degeneration.

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Figure 1

 

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Figure 2

 

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Figure 3 

 

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Figure 4

 

 

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