In vitro nucleus pulposus tissue model with physicochemical stresses

Area of Science:

• Biomaterials Science
• Cell Biology
• Biotechnology

Background:

• Intervertebral discs (IVDs) experience physicochemical stresses from daily spinal motion.
• Current in vitro models struggle to replicate these stresses for studying IVD homeostasis, degeneration, and regeneration.
• Nucleus pulposus (NP) cell incubation in standard media limits the simulation of anabolic turnover.

Purpose of the Study:

• To develop and validate a novel pressure/perfusion cell culture system for IVD research.
• To identify optimal physicochemical stress loading regimens for NP cells.
• To simulate anabolic and catabolic processes in NP cells under physiologically relevant conditions.

Main Methods:

• Developed a novel pressure/perfusion system with semipermeable membrane pouches for isolated NP cells.
• Incubated bovine caudal NP cells under various cyclic and constant hydrostatic pressure (HP) regimens in high osmolality (HO) medium.
• Assessed gene expression (e.g., aggrecan) and extracellular matrix (ECM) accumulation.

Main Results:

• A 4-day cyclic HP followed by 3-day constant HP in HO showed trends of upregulated aggrecan and dense keratan sulfate accumulation.
• A repetitive regimen (2-day cyclic HP + 1-day constant HP in HO, repeated) significantly upregulated aggrecan gene expression (P < .05).
• The same repetitive regimen significantly suppressed matrix metalloproteinase-13 expression (P < .05).

Conclusions:

• The developed culture system effectively reproduces physicochemical stresses relevant to IVD function.
• Identified a promising stress loading regimen to promote anabolic markers and suppress catabolic markers in NP cells.
• The system offers a valuable tool for simulating IVD turnover and studying degeneration/regeneration in vitro.