Extracellular vesicles (EVs) and exosomes are nano-sized, membrane-bound vesicles shed by most eukaryotic cells studied to date. EVs play key signaling roles in cellular development, cancer metastasis, immune modulation and tissue regeneration. Attempts to modify exosomes to increase their targeting efficiency to specific tissue types are still in their infancy. Here researchers from Cedars-Sinai Medical Center describe an EV membrane anchoring platform termed “cloaking” to directly embed tissue-specific antibodies or homing peptides on EV membrane surfaces ex vivo for enhanced vesicle uptake in cells of interest. The cloaking system consists of three components: DMPE phospholipid membrane anchor, polyethylene glycol spacer and a conjugated streptavidin platform molecule, to which any biotinylated molecule can be coupled for EV decoration.
The researchers demonstrate the utility of membrane surface engineering and biodistribution tracking with this technology along with targeting EVs for enhanced uptake in cardiac fibroblasts, myoblasts and ischemic myocardium using combinations of fluorescent tags, tissue-targeting antibodies and homing peptide surface cloaks. They compare cloaking to a complementary approach, surface display, in which parental cells are engineered to secrete EVs with fusion surface targeting proteins.
EV targeting can be enhanced both by cloaking and by surface display; the former entails chemical modification of preformed EVs, while the latter requires genetic modification of the parent cells. Reduction to practice of the cloaking approach, using several different EV surface modifications to target distinct cells and tissues, supports the notion of cloaking as a platform technology.
Exosome fluorescent cloaking
a Schematic of cloaking technology depicting the three components: DMPE phospholipid membrane anchor, Polyethylene glycol (PEG) 5K spacer and streptavidin platform molecule (STVDN), together abbreviated DPS. To the right in a, example types of biotinylated molecules that can be coupled to the DPS membrane platform are shown. Representative FACS plots depicting NRVM uptake of CDC-EV cloaked with bio-FITC (b) or bio-PE (c), gates are indicated. d Pooled data from b, c. n = 4 wells per experimental group