Effects of macrophage-conditioned medium on sika deer (Cervus nippon) antler stem cells

Context Immune system has been claimed as the 'main switch' of tissue or organ regeneration. Among immune cells, macrophages stand out as important modulators in mutiple regeneration models, such as planarian, axolotl, mammalian hair and liver. As a unique model for mammals, deer antler is considered to ideal for studying complete mammalian organ regeneration. Studies have found that antler regeneration is a stem cell-based process and antler stem cells locate in the pedicle periosteum (PP). Although the regulatory roles of the immune system in other regeneration models have been extensively studied, they remain unstudied in antler regeneration. Aims To explore the possible role of macrophages in the PP cells (PPCs). Methods We treated PPCs with a macrophage-conditioned medium (MCM) and detected effects of MCM on proliferation, migration and apoptosis of the PPCs, and identified differentially expressed genes by using the RNA-seq technique. Key results We found that MCM enhanced proliferation rate and migration rate significantly and stimulated apoptosis of the PPCs. Using the RNA-seq technique, we identified 112 differentially expressed genes in the PPCs (38 downregulated and 74 upregulated) after the MCM treatment. Furthermore, gene-ontology annotation analyses showed that the upregulated genes were mainly involved in cell adhesion, chemotaxis, wound healing, growth factor-stimulated responses, and bone formation, and the downregulated genes were involved in regulation of biosynthesis. Conclusions MCM had a great influence on the antler stem cells, and macrophages might regulate antler regeneration through altering the microenvironment and gene-expression profiles of the PPCs. Implications We believe that the results of the present study would facilitate the discovery of the roles of immune system in antler stem cells and, thus, mammalian organ regeneration in general.