Species-dependent lymphatic niche remodeling supports mesenchymal stem cells for superior skull regeneration

Mesenchymal stem cells (MSCs) depend on niche for tissue regeneration. Lymphatic vasculature in bone remains poorly understood. Here we use pro-regenerative spiny mouse (Acomys cahirinus) and lab mouse (Mus musculus) dual species system to dissect lymphatic-MSC interactions in skull regeneration. Our tissue clearing and 3D volume imaging identified lymphatic vessels in skull periosteum as the niche component of MSCs. Genetic or pharmacological depletion of lymphatic vessels delay skull injury repair due to MSC reduction. Compared to laboratory mice, single-cell RNA sequencing (scRNA-seq) revealed that spiny mice exhibit enhanced skull regeneration, characterized by a higher proportion of pro-regenerative macrophages, distinct gene expression programs, and elevated secretion of macrophage-derived factors, including vascular endothelial growth factor C (VEGF-C). Spiny mouse macrophages differentially upregulate and secrete VEGF-C to induce lymphangiogenesis, meanwhile impart a lymphatic endothelial cell (LEC) secretome switch towards more potent support of MSC activities. Lymphatic gain-of-function in lab mice promotes MSCs leading to enhanced skull injury repair, while its loss-of-function in spiny mice inhibits MSC activities resulting in a delayed repair. Ectopic LEC application promotes human MSC function and skull regeneration in humanized mouse models in vivo. Therefore, lymphatic niche supports MSCs for superior regeneration via species-dependent lymphangiogenesis and lymphangiocrine remodeling.