Nociceptive nerves regulate haematopoietic stem cell mobilization

Haematopoietic stem cells (HSCs) reside in specialized microenvironments in the bone marrow (BM), often referred to as “niches”, which represent complex regulatory milieux influenced by multiple cellular constituents, including nerves(1,2). Although sympathetic nerves regulate the HSC niche(3-6), the contribution of nociceptive neurons in the BM remains unclear. Here we show that nociceptive nerves are required for enforced HSC mobilization and collaborate with sympathetic nerves for HSC maintenance in BM. Nociceptor neurons drive granulocyte colony-stimulating factor (G-CSF)-induced HSC mobilization via the secretion of calcitonin gene-related peptide (CGRP). Unlike sympathetic nerves which regulate HSCs indirectly via the niche(3,4,6), CGRP acts directly on HSCs via the receptor activity modifying protein-1 (RAMP1) and calcitonin-receptor-like receptor (CALCRL), to promote egress by activating Gα(s)/Adenylyl cyclase/cAMP pathway. Remarkably, the ingestion of food containing capsaicin (a natural component of chili peppers), significantly enhanced HSC mobilization. Thus, targeting the nociceptive nervous system is a novel strategy to improve the HSC yield for stem cell-based therapeutics.