Extracellular vesicles (EVs) are cell-derived nanostructures that mediate intercellular communication by delivering complex signals in normal tissues and cancer. The cellular coordination required for tumor development and maintenance is mediated, in part, through EV transport of molecular cargo to resident and distant cells. Most studies on EV-mediated signaling have been performed in two-dimensional (2D) monolayer cell cultures, largely because of their simplicity and high-throughput screening capacity. Three-dimensional (3D) cell cultures can be used to study cell-to-cell and cell-to-matrix interactions, enabling the study of EV-mediated cellular communication. 3D cultures may best model the role of EVs in formation of the tumor microenvironment (TME) and cancer cell-stromal interactions that sustain tumor growth. In this review, we discuss EV biology in 3D culture correlates of the TME. This includes EV communication between cell types of the TME, differences in EV biogenesis and signaling associated with differing scaffold choices and in scaffold-free 3D cultures and cultivation of the premetastatic niche. An understanding of EV biogenesis and signaling within a 3D TME will improve culture correlates of oncogenesis, enable molecular control of the TME and aid development of drug delivery tools based on EV-mediated signaling.

Schwann cells (SCs) aid in nerve repair in the peripheral nervous system, and their ability to migrate into the injury site is critical for nerve regeneration after injury. The majority of studies on SC behavior have focused on SC alignment through contact guidance, rather than migration. The few studies on SC migration primarily investigated the migration of individual cells over several hours with time-lapse microscopy. However, during neural tissue repair, SCs do not migrate as single cells but as a population of cells over physiologically relevant time and length scales. Thus from a practical perspective, there is a need to understand the migration of large populations of SC and the collective guidance cues from the surrounding environment in designing optimal transplantable scaffolds. This study investigates a large population of migrating SCs over a period of 2 weeks on patterned polydimethylsiloxane (PDMS) microgrooved channels of different sizes. Two methods were used to quantify the migration velocity of a large cell population that minimized the confounding effect due to cell proliferation: one based on a leading edge velocity and a second based on a binary velocity. Both approaches showed that the SC population migrated the fastest on the smallest sized microgrooved channels. The insights provided in this study could inform on future designs of transplantable scaffolds for peripheral nerve regeneration.