RNA sequencing of cold stimulated neuroimmune cells from mouse subcutaneous adipose tissue

Adipose neural innervation is necessary for the proper function of this metabolic tissue. We and others have demonstrated that neuroimmune cells are present along the nerves in adipose tissue, but their functions (beyond norepinephrine degradation) remain largely unexplored. We previously demonstrated that knockout of brain derived neurotrophic factor (BDNF) from myeloid lineage cells resulted in reduced neurite density in subcutaneous white adipose tissue (scWAT) and subsequent metabolic perturbations, supporting the idea that adipose neuroimmune cells support the function and survival of peripheral nerves in the tissue. In an unbiased flow-cytometric analysis of immune cells recruited to scWAT with cold stimulation (a process known to increase neurite density in the tissue and promote metabolically healthy processes), we found a subset of myeloid lineage monocytes/macrophages (Ly6c+CCR2+Cx3cr1+) that are recruited to scWAT in response to cold in both male and female mice. We have named these cells cold induced neuroimmune cells (CINCs). To further understand the function of these cells in scWAT, we performed RNAseq on CINCs from cold exposed versus room temperature housed mice. RNASeq analysis revealed CINCs from cold-stimulated mice differentially express genes involved in neuronal function, including neurotrophin signaling and neurodegenerative pathways, consistent with our hypothesis that these are cold-recruited neuroimmune cells. Interestingly, CINCs in adipose tissue of mice housed at room temperature also exhibited a neuroimmune profile characterized by genes involved in axonal guidance. In CINCs from cold exposed mice, genes related to homing and leukocyte trans-endothelial migration are also increased, consistent with our hypothesis that they are recruited to scWAT. Based on these data, we propose that CINCs function in a homeostatic way to maintain nerve health and neuro-adipose communication, and that following noradrenergic stimulation (such as cold exposure) CINCs support adipose nerve remodeling through increased recruitment to scWAT and secretion of neurotrophic factors and axon guidance/repulsion cues.