Chitosan-polyvinyl pyrrolidone hydrogel does not activate macrophages: Potentials for transplantation applications

We have shown previously that chitosan-polyvinyl pynolidone (PVP) hydrogels are blood compatible, islet compatible, and noncytotoxic to various cell t ypes. Because of these potential applications of chitosan-PVP hydrogel, the present study was designed to investigate its effect on macrophage activat ion. Macrophages did not adhere to hydrogel in culture but maintained their viability and did not undergo apoptosis as confirmed by trypan blur staini ng and absence of DNA ladder. Hydrogel leach-out products did not exhibit c ytotoxic effects on macrophage functionality at mitochondrial and lysosomal level as confirmed by tetrazolium reduction (MTT) and neutral red uptake ( NRU) assay. On exposure to hydrogels, macrophages showed comparable express ion of activation markers such as CD11b/CD18 (Mac-1), CD45, and CD14 to tho se cultured in the presence of PTFE, a known biocompatible control. indicat ing its nonactivating nature. Macrophage activation was also assessed by ch ecking the level of messenger RNA of inflammatory cytokines such as IL-6 an d TNF-alpha by reverse transcriptase polymerase chain reaction (RT-PCR), wh ich did not show stastistically significant difference (p > 0.05) in the ex pression of these transcripts in both control and hydrogel-exposed macropha ges. The nonimmunogenic nature of the hydrogel was further confirmed by the lack of induced proliferation of mouse splenic lymphocytes after exposure to hydrogel leach-outs. All these results point out that chitosan-PVP hydro gel did not activate macrophages and thus is immunocompatible. Our results indicate that this hydrogel could be a potential candidate for transplantat ion studies by virtue of its biocompatibility and imunocompatibility.