(143f) Inert Nanoparticles for Enhancing the Survival of Primary Macrophages.

Cell-based therapies have recently emerged as a new platform for treating a spectrum of chronic degenerative diseases, with serious advances made especially in hematopoietic stem cell and reactive lymphocyte therapies. Macrophages are leukocytes responsible for phagocytosing foreign objects, bacteria, and apoptotic cells, maintaining homeostasis, and bridging the innate and adaptive immunity. Macrophage-based cell therapy has been identified as a promising therapeutic approach to treat chronic immune dysfunctions, owing to the functionality and phenotype plasticity of macrophages. However, a major challenge in the advancement of macrophage-based cell therapies is the difficulty to maintain adequate cell viability ex vivo following macrophage isolation from tissue. Current attempts of macrophage in situ activation or autologous cell therapy following ex vivo stimulation fail to elicit effective therapeutic responses, due to low cell survival rates upon reintroduction. Therefore, there is a need to develop new approaches to regulate primary macrophage survival in both in vivo and ex vivo environments.

We attempted to extend the viability of ex vivo macrophage cultures through treatment of inert poly(ethylene glycol) (PEG) diacrylate (PEGDA)-based nanoparticles. We observe that ex vivo bone marrow-derived macrophages (BMMs), which typically undergo apoptosis within 2 weeks under appropriate culture conditions, can persist and maintain functionality for up to 6 months after being treated with a single dose of PEGDA nanoparticles. We find that nanoparticle uptake significantly delays primary macrophage cell death through the downregulation of caspase-dependent apoptosis pathways. Furthermore, we observe no major changes to macrophage phenotype following nanoparticle uptake. However, phagocytosis of PEGDA nanoparticles leads to increased expression of major histocompatibility complex (MHC) class II uniquely in the absence of other co-stimulatory molecules. The enhanced survival phenomenon is also applicable to ex vivo cultures of terminally differentiated macrophages isolated from tissue, including peritoneal and alveolar primary cells. Overall, this work demonstrates for the first time the ability of inert nanoparticles to suppress apoptotic signaling and prolong viability in primary macrophages extracted from different tissues. This work could eliminate a major obstacle standing in the way of developing macrophage-based cell therapies, as well as provide mechanistic insight into the implications of nanoparticle phagocytosis on cell longevity and function.