Hydrogel Microparticles Preserve Cell Secretome and Extracellular Vesicle Bioactivity for Improved Cell-Based Therapy Deployment

Secretomes derived from diverse progenitor cell classes are commonly employed in regenerative medicine applications to promote cell expansion and tissue differentiation. However, the bioactivity of secretome components, including soluble proteins and extracellular vesicles, is hindered by their low stability in basal cell culture media. Hydrogels are a promising strategy for improving secretome viability by providing a structurally supportive, biomimetic environment. This work examined the effects of poly(acrylic acid)-based hydrogel microparticles in the context of a previously characterised magnetic secretome-induction paradigm. We investigated the impact of a hydrogel microenvironment on the release and collection of secretome, during and after media conditioning. Various inorganic salt species were used to control microgel particle swelling and enable liquid phase collection. Calcium chloride was more effective than sodium or magnesium chlorides in facilitating secretome recovery with reference to promoting in vitro myogenesis at the cellular and protein levels. Notably, the secretome released from magnetically-induced myoblast cultures in microgel-derived conditioning media was as supportive of cell growth as foetal bovine serum (FBS), whereas the secretomes harvested from unstimulated cells in hydrogels or from stimulated cells in the absence of hydrogels were less effective. Microgel-derived conditioned media also enhanced the stability of isolated extracellular vesicles, better preserving their efficacy during storage at room temperature, 4° C and -20° C. These results indicate that these microgels protected the secretome from degradation. Media incorporating microgels represent an innovative approach with which to preserve the potency of cell secretomes collected following various induction protocols for improved commercial and clinical exploitation.