Intravenous immune-modifying nanoparticles as a therapy for spinal cord injury in mice

Abstract

Intravenously infused synthetic 500 nm nanoparticles composed of poly(lactide-co-glycolide) are taken up by blood-borne inflammatory monocytes via a macrophage scavenger receptor (macrophage receptor with collagenous structure), and the monocytes no longer traffic to sites of inflammation. Intravenous administration of the nanoparticles after experimental spinal cord injury in mice safely and selectively limited infiltration of hematogenous monocytes into the injury site. The nanoparticles did not bind to resident microglia, and did not change the number of microglia in the injured spinal cord. Nanoparticle administration reduced M1 macrophage polarization and microglia activation, reduced levels of inflammatory cytokines, and markedly reduced fibrotic scar formation without altering glial scarring. These findings thus implicate early-infiltrating hematogenous monocytes as highly selective contributors to fibrosis that do not play an indispensable role in gliosis after SCI. Further, the nanoparticle treatment reduced accumulation of chondroitin sulfate proteoglycans, increased axon density inside and caudal to the lesion site, and significantly improved functional recovery after both moderate and severe injuries to the spinal cord. These data provide further evidence that hematogenous monocytes contribute to inflammatory damage and fibrotic scar formation after spinal cord injury in mice. Further, since the nanoparticles are simple to administer intravenously, immunologically inert, stable at room temperature, composed of an FDA-approved material, and have no known toxicity, these findings suggest that the nanoparticles potentially offer a practical treatment for human spinal cord injury.

Intravenous Immunomodulatory Nanoparticle Treatment for Traumatic Brain Injury

“…As previously described, slides were washed in PBS‐Triton (PBS‐T) (Triton concentration is given thusly) (0.05% Triton X‐100) and incubated with primary antibodies at 4°C overnight in blocking media (5% normal donkey serum in PBS‐T). Primary antibodies used were: GFAP (Dako, Carpinteria, CA, Z0334, 1:1,000; Abcam, Cambridge, MA, ab4674, 1:1,000) and MARCO (BAF2956, 1:50) . For GFAP, primary antibodies were visualized with Alexa 647 (far red), 594 (red), and 488 (green) Alexa Fluor conjugated secondary antibodies at 1:1,000 dilution (Life Technologies, Carlsbad, CA).…”

“…As previously described, mice were anesthetized with 50mg/kg pentobarbital followed by cardiac perfusion with 30mL of phosphate-buffered saline (PBS). 13 For CCI, injured section of brain (3mm 3 lesional/perilesional area) was microdissected at 72 hours after injury. For CHI experiments, whole brain tissue was processed at 72 hours after injury as well.…”

“…Primary antibodies used were: GFAP (Dako, Carpinteria, CA, Z0334, 1:1,000; Abcam, Cambridge, MA, ab4674, 1:1,000) and MARCO (BAF2956, 1:50). 13 For GFAP, primary antibodies were visualized with Alexa 647 (far red), 594 (red), and 488 (green) Alexa Fluor conjugated secondary antibodies at 1:1,000 dilution (Life Technologies, Carlsbad, CA). Nuclei were visualized with 4 0 , 6-diamidino-2-phenylindole (DAPI) at 1:2,000 dilution.…”

Engineering Immune Tolerance with Biomaterials

“…While the precise mechanism for tolerance is not fully understand, this study and others using PLGA NPs displaying self‐antigens have demonstrated both size and charge play a role in efficacy; NPs ≈500 nm in diameter with negative surface charges display the highest level of colocalization with MARCO and efficacy in promoting tolerance. Recent studies, which are discussed in Section , have also demonstrated that negatively charged particles delivered without self‐antigens can drive tolerance …”

“…As described in Section , recent studies have demonstrated that biomaterials display intrinsic properties that can drive inflammatory or proimmune function in immune cells. Other recent studies have described tolerogenic properties of various biomaterials, including synthetic polymers such as PLGA and PS, QDs, gold NPs, and cellulose nanofibers . These intrinsic biomaterial properties are now starting to be explored in therapeutic contexts as tools to promote tolerance in preclinical models of autoimmune disease.…”