Cranial photo-immunologic regulation along the skull-meninges-brain axis for promoting recovery from ischemic brain injury
Stroke involves in the interaction between central and peripheral immune systems. Skull bone marrows serve as reservoirs for immune cells in brain borders, and can rapidly respond to perturbations in the brain environment. Hence, targeting the skull bone marrow to modulate neuroimmune communications along the calvaria-meninges-brain axis would potentially improve stroke prognosis. Here, we successfully achieved cranial immunomodulation via ultraviolet (UV) irradiation of the interparietal region, which was characterized by rich marrow cavities and channels connecting the skull and meninges. Utilizing the recently-developed long-term clearing cranial window that ensured the integrity of skull, we discovered that the cranial photo-immunologic regulation (CPR) could promote cerebrovascular regeneration and aid in neurovascular repair post ischemic stroke. Single-cell transcriptome analysis revealed that meninge could be a crucial neuroimmune interface for ischemic stroke-induced immune responses. And, CPR could restore the stroke-induced alterations in cellular gene expression, especially meningeal B cells. Further we demonstrated that CPR could effectively alleviate the excessive suppression of meningeal B cell activation caused by ischemic stroke. This work opens avenues for immunoregulation through the skull-meninges-brain axis and provides valuable insights for immunomodulatory therapies in brain diseases. Overall design: Bulk RNA sequencing of mouse skull, meninges, and brain tissue at 0.5/24 hours post cranial photobiomodulation, as well as bulk RNA sequencing of mouse skull, meninges, and brain tissue following non-cranial  photobiomodulation.