Aggrecan, an unusual polyelectrolyte: review of solution behavior and physiological implications

Area of Science:

• Biopolymer science
• Extracellular matrix research
• Biophysics

Background:

• Aggrecan is a major component of cartilage extracellular matrix.
• It forms large complexes with hyaluronic acid, influencing cartilage's osmotic properties.
• These complexes resist swelling under compressive loads.

Purpose of the Study:

• To review aggrecan solution behavior across various experimental techniques.
• To correlate solution behavior with identified concentration regimes.
• To discuss the implications of aggrecan's structure on cartilage properties.

Main Methods:

• Compilation of data from diverse experimental techniques.
• Analysis of aggrecan solution behavior in different concentration regimes.
• Examination of osmotic pressure experiments.

Main Results:

• Aggrecan exhibits microgel-like behavior at low concentrations.
• At higher concentrations, aggrecan bottlebrushes self-assemble into large complexes.
• Repulsive electrostatic interactions dominate in the physiological concentration range (2-8% w/w).

Conclusions:

• Aggrecan's bottlebrush architecture significantly influences its polyelectrolyte characteristics.
• These characteristics are critical for maintaining cartilage properties and function.
• Understanding aggrecan behavior is key to understanding cartilage biomechanics.