Macrophage membrane-functionalized nanofibrous mats and their immunomodulatory effects on macrophage polarization

Immunomodulation is an important phenomenon in the normal mammalian host response toward an injury, and plays a critical role in tissue regeneration and regenerative medicine. Different phenotypes of macrophages show an array of activation states compassing pro-inflammatory to pro-alleviating cells, which are the critical players to modulate immune response and tissue regeneration. In this study, macrophage membranes of different phenotypes (macrophages (M0), classically activated macrophages (M1) and alternatively activated macrophages (M2)) were coated onto poly-ε-caprolactone (PCL) nanofibers to acquire exterior surface proteins and similar functions of the natural membranes. In vitro results unveiled that these nanofibers, especially the M2-PCL nanofibers, can suppress the activities of inflammatory markers such as TNF-α and IL-1β, and stimulate anti-inflammatory markers such as Arg-1, IL-10 and TGF-β. In a C57BL/6 mouse model, the macrophage membrane-coated nanofibers, especially the M2-PCL nanofibers, displayed minimal cellular infiltration and low collagen deposition, increased anti-inflammatory CD206 and decreased inflammatory CD86 levels. The M2-PCL nanofibers most effectively neutralized inflammatory chemokines, regulated the expression of inflammation-associated genes as well as anti-inflammatory genes, and showed strong immunomodulatory effects than the PCL, M0-PCL and M1-PCL nanofibers. Different types of macrophage membrane-functionalized PCL nanofibers were successfully prepared and well characterized. They inherited the surface proteins imitating the source macrophages, and played an important role in limiting cellular infiltration and collagen deposition. These different macrophages and their membrane-coated nanofibers (M0-PCL, M1-PCL and M2-PCL) behaved like their respective source cells. The M2 mimicking M2-PCL nanofibers effectively polarized macrophages to M2 phenotype and decreased the expression of inflammation-associated chemokines and promoted the anti-inflammation in vitro and in vivo, which is critical for tissue regeneration. The mice implanted with the bio-mimicking M2-PCL nanofibers effectively inhibited toll like receptors signaling induced NF-kB and IRF-5 and their target genes such as Edn-1, IL-6, iNOS, TNF-α, etc. compared to the PCL, and M0-PCL and M1-PCL macrophage membrane-coated nanofibers.