The Immobilization of Hyaluronic Acid in 3D Hydrogel Scaffolds Modulates Macrophage Polarization.

Macrophages are key modulators of immunity, tissue homeostasis and disease development. As our understanding of macrophage biology and their tissue-specific behaviors grows the necessity to model macrophages within a 3D biomimetic environment becomes increasingly apparent. Numerous hydrogels are developed and explored for this purpose, extracellular matrix (ECM) mimicking hydrogels gaining special interest. In this study, the use of such a hydrogel composed of collagen and hyaluronic acid (HA), two of the major ECM components, is presented for the 3D culture of macrophages to model their role in different tissues and diseases. The ability to tailor the mechanical properties of the hydrogel through formulation modulation is demonstrated. Human macrophages retain morphology, viability, and expression of key cell surface markers when 3D cultured within the hydrogel. Interestingly, it is demonstrate in this work, that independent of mechanical properties, by adjusting the composition of the hydrogel, specifically HA molecular weight, steers macrophage polarization toward either a pro-inflammatory or anti-inflammatory phenotype. This HA-dependent modulation of macrophage behavior is nullified if the HA is chemically crosslinked, shedding light on the impact of one of the most commonly used preparation methods for collagen-HA hydrogels on macrophage behavior.