Background and aims:
Efficient in vivo transport of active siRNA to specific liver cells remains challenging. First and
second generation cationic nanohydrogel particles (NHP) are excellent oligonucleotide
carriers [Kaps L et al, Adv. Healthcare Mat. 2015; J. Contr. Rel. 2016]. We designed
a third generation of NHP where mannose residues are covalently linked to the surface
(Man-NHP), enabling targeting of CD206 positive M2 macrophages, which are implicated
in HCC and liver fibrosis progression.
Method and Results:
Man-NHP composed of block copolymers (pentafluorophenyl methacrylate and tri-(ethylene
glycol) methyl ether methacrylate), with diameters around 40nm and loaded with control
siRNA (scsiRNA) up to 400 nM did not show cytotoxicity for murine 3T3 fibroblasts,
Raw macrophages, SVEC endothelial cells or HepG2 human hepatoma cells. Man-NHP labelled
with FITC showed a preferential binding to in vitro polarized CD206 high M2 compared to CD206 low non-polarized M0 or M1-polarized bone-marrow
derived macrophages (BMDM), as determined by FACS analysis. Man-NHP were shielded
from unspecific interactions compared to non-mannose coated NHP, which exhibited high
binding to macrophages regardless of their phenotype. Man-NHP loaded with siRNA to
CSFR-1, an M2 macrophage specific target, yielded a robust knockdown in M2 polarized
BMDM after 48h of incubation.
After intravenous injection in mice with CCl4-induced liver fibrosis, near infrared (NIR, CW800-dye) labeled Man-NHP loaded with
Cy5-labelled scsiRNA distributed preferentially to the liver (> 80%), as determined
by in vivo and ex vivo NIR imaging. Ex vivo colocalization studies of liver single cell suspension and confocal fluorescence
microscopy of cryo liver sections obtained from Man-NHP-NIR/Cy5-scsiRNA treated fibrotic
mice revealed that Man-NHP-NIR/Cy5-scsiRNA complexes were preferentially taken up
in CD206+ M2 macrophages in contrast to other (non)-parenchymal liver cells.
Conclusion:
Third generation NHP were derivatized with surface mannose residues for effective
M2 macrophage targeting via the mannose receptor CD206 in vitro and in vivo. Man-NHP are a promising tool to specifically target therapeutic siRNA to fibrosis
and HCC promoting M2 macrophages.
