Chemically and mechanically defined hyaluronan hydrogels emulate the extracellular matrix for unbiased in vivo and in vitro organoid formation and drug testing in cancer

Abstract
Finding a material that emulates the in vivo microenvironment to allow complex cell phenotypes in vitro and without biasing cell fate in vivo remains a significant challenge. Hyaluronan is over-expressed in breast cancer and in several other tumours. Mammary epithelial cells invade tissues through both active degradation of the matrix and ameboid-like mechanisms. Thus, we synthesized a defined, biomimetic hydrogel composed of hyaluronan (HA) and matrix metalloproteinase-cleavable (MMPx) crosslinker and used oxime crosslinking to ensure tunability of the resulting HA-MMPx hydrogel. This strategy allowed us to identify the optimal matrix to study the growth and polarization of healthy and diseased mammary epithelial cancer cells first in vitro and then in vivo. We then extended the platform to study nine different cancer types in vitro. We demonstrate that primary, patient-derived breast cancer cells from biopsies established organoids within HA-MMPx and, relative to Matrigel®, had different growth rates and responses to drugs, underscoring the importance of the extracellular environment to cell fate. We established patient-derived xenografts (PDX) using HA-MMPx in SCID mice and showed superior reproducibility compared to Matrigel®. Fascinatingly, PDX grown in HA-MMPx did not induce resident murine macrophage polarization whereas those grown in Matrigel® showed an increase in the proportion of alternatively activated cells, indicating that Matrigel® itself skewed macrophage polarization. Importantly, HA-MMPx did not bias the immune cell response in vivo and supported a diverse range of organoid phenotypes in vitro.

Hyaluronic acid, Hydrogels, Acini, Polarization, Patient-derived xenograft, Matrigel, Cancer