Polydispersity and negative charge are key modulators of extracellular matrix deposition under macromolecular crowding conditions.

Macromolecular crowding is a biophysical phenomenon that stems from the volume excluded by macromolecules, as they undergo steric repulsion and electrostatic interactions. The excluded volume depends on the shape, size, charge and polydispersity of the molecules. Although theoretical/computational models have been used to assess the influence of macromolecular crowding in biological media, real-time experiments are scarce. Herein, we evaluated the influence of hydrodynamic radius, charge and polydispersity of (a) various concentrations of different crowders (carrageenan, Ficoll™ and dextran sulphate); (b) various molecular weights of different crowders (70, 400 and 100 kDa of Ficoll™ and 10, 100 and 500 kDa of dextran sulphate) and (c) various cocktails of the same crowders (cocktails of various concentrations of different molecular weights Ficoll™ and dextran sulphate) on extracellular matrix deposition in human dermal fibroblast culture. The use of crowding cocktails with different molecular weight/concentrations of Ficoll™ or dextran sulphate molecules led to increased polydispersity and enhanced collagen type I deposition in comparison to their mono-domain counterparts. Carrageenan, however, induced the highest deposition of collagen type I due to its negative charge and inherent polydispersity. Our data contribute to a better understanding of the influence of the biophysical properties of the crowders on extracellular matrix deposition in vitro. STATEMENT OF SIGNIFICANCE: Macromolecular crowding is a biophysical phenomenon that accelerates and enhances extracellular matrix deposition in cell culture systems. Herein, we demonstrate that negatively charged and polydispersed macromolecules or cocktails of macromolecules, as opposed to neutral and monodomain macromolecules, induce highest extracellular matrix deposition in human dermal fibroblast cultures.