Bioprinting exosome-like extracellular vesicle microenvironments

Abstract

Exosomes are a subset of extracellular vesicles that transport a wide variety of cell signaling molecules. Similar to growth factors, exosomes occur both in a ‘liquid-phase’ suspension in body fluids and in a ‘solid-phase’ immobilized via native binding affinities to the extracellular matrix (ECM). To date, most investigations have been focused on liquid-phase exosomes, and only limited information is available regarding the interaction between exosomes and the ECM components during intercellular communication. This gap in knowledge is partly due to the lack of well-defined in vitro models of solid-phase exosome/ECM microenvironments. To study these interactions, we adapted our inkjet-based bioprinting technology to fabricate spatially defined patterns of solid-phase exosome microenvironments. As a paradigm application, microenvironments consisting of exosomes derived from different macrophage subsets, M0 (non-activated), M1 (pro-inflammatory) and M2 (pro-regenerative), were bioprinted on collagen type-I coated substrates and their effects on myogenesis of C2C12 cells were investigated in registration to the printed patterns. M1 exosome microenvironments spatially inhibited myogenesis while promoting proliferation, whereas M2 exosome microenvironments spatially promoted myogenesis in a dose-dependent manner. This work provides the proof-of-concept for bioprinting highly controlled and well-defined exosome-based microenvironments that can be used to investigate mechanisms underpinning exosome-mediated effects on the ECM. Furthermore, this bioprinting technology can be directly translated to in vivo applications for localized exosome delivery to tissues.