Strategies for controlling egress of therapeutic cells from hydrogel microcapsules

Abstract

Endothelial progenitor cells and human mesenchymal stem cells (hMSCs) haveshown great regenerative potential to repair damaged tissue; however, their injection in vivo results in low retention and poor cell survival. Early clinical research has focussed on cell encapsulation to improve viability and integration of delivered cells. However, this strategy has been limited by the inability to reproduce large volumes of standardized microcapsules and the lack of information on cell-specific egress and timed release from hydrogel microcapsules. Here, we address both of these limitations. First, we use a droplet microfluidic platform to generate monodisperse agarose microcapsules, and second we encapsulate and characterize egress of therapeutically relevant cells (human umbilical vein endothelial cells, endothelial progenitor cells, and hMSCs). With increased temporal resolution, we demonstrate distinct differences in egress between cell types. Importantly, therapeutic cells (hMSCs) egress quickly, in <6 hr following encapsulation. Further, we examined potential escape mechanisms and showed that proliferation can be exploited by cells for microcapsule translocation. We also systematically characterized the egress of fibroblasts (as model cells) following alterations to the microcapsules. Specifically, we show that microcapsule size and hydrogel density impact cell egress efficiency.Overall, our results demonstrate the need for characterization of cell-specific egress and tuning of the cocoon microenvironment prior to delivery, for timely release and successful engraftment.

Targeting extracellular vesicle delivery to the lungs by microgel encapsulation

“…Nanoporous hydrogels have been previously used to encapsulate single cells forming a “microgel” niche to protect cells for in vivo delivery 23 . A microfluidic approach 27,28 was employed to encapsulate EVs labelled with pkh26 in 1% agarose-1% gelatin producing microgels of uniform size (47 ± 0.4 μm) ( Figure 2A-C ). Labelled EVs were detected within microgels evenly dispersed throughout the spherical microgel as observed using confocal imaging z-stacks ( Figure 2D ).…”

“…Extracellular vesicles were encapsulated using a novel microfluidic device designed for cell and small particle encapsulation, in a similar manner as described for cell encapsulation 27,28 . In brief, a known quantity of EV protein was mixed with 1% ultra-low gelling temperature agarose (Sigma Aldrich, Oakville, ON, Canada), 1% gelatin (Sigma Aldrich, Oakville, ON, Canada) and kept at 37°C during encapsulation.…”

Hydrogels for Single-Cell Microgel Production: Recent Advances and Applications

“…Similarly, combinations of natural and synthetic polymers can be combined with temperature responsive moieties to obtain hydrogels with unique swelling and gelling properties (Jiang et al, 2019a). Such composite hydrogels can also allow for finetuning of hydrogel degradation (Benavente Babace et al, 2019;Neubauer et al, 2019), which offers lots of potential for in vivo applications. In addition, alterations can facilitate complex techniques that would be extremely difficult or impossible with natural hydrogels.…”

Advanced microfluidic devices for fabricating multi‐structural hydrogel microsphere

“…When hydrogel microspheres are used as cell carriers, it is found that the cells distributed along the border of the hydrogel droplets tend to escape upon droplet crosslinking and during subsequent culturing. [114,115] Thus, the laden cells are expected to be focused on the center of the droplets to reduce or avoid cellular escape. In one study, microfluidic platform was placed on an orbital shaker that orbited at 1000 rpm during droplet crosslinking to achieve robust positioning of individual MSCs in the center of hydrogel microspheres.…”