Quantifying Baseline Fixed Charge Density in Healthy Human Cartilage Endplate: A Two-point Electrical Conductivity...

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Spinal Biomechanics

Background:

• The cartilage endplate (CEP) is crucial for intervertebral disc health, regulating its internal environment via fixed charge density (FCD).
• FCD, determined by glycosaminoglycans (GAGs), influences ionic and osmotic balance.
• Quantitative FCD data for healthy human CEP is currently lacking.

Purpose of the Study:

• To determine regional FCDs in healthy human CEP across four distinct areas.
• To correlate CEP FCDs with the tissue's biochemical composition, specifically GAG and water content.

Main Methods:

• Regional isolation of human lumbar spine CEP specimens.
• Two-point electrical conductivity measurements for concurrent FCD and ion diffusivity assessment.
• Biochemical assays to quantify regional GAG and water content.

Main Results:

• Regional FCD in healthy human CEP is variable, being lowest in the lateral region.
• CEP FCD is significantly lower than in the nucleus pulposus (NP) but comparable to annulus fibrosus (AF) and articular cartilage (AC).
• CEP FCD positively correlates with GAG content and exhibits lower ion diffusivity compared to AF and NP.

Conclusions:

• Healthy human CEP functions as a critical biomechanical interface, managing load distribution between vertebral bodies and disc tissues.
• The CEP acts as a diffusion barrier, restricting rapid solute transport through the intervertebral disc.