The gum has an exceptional capacity for healing. To examine the basis for this property and explore the potential of conferring it to organs with inferior healing capacity, we sought the presence of progenitor cells in gingival connective tissue. Colony-forming units of fibroblast-enriched cells from gingival fibroblast cultures were assessed for expression of membrane markers of mesenchymal stem cells; capacity to differentiate into osteoblasts, chondroblasts, and adipocytes; and engraftment efficiency after in vivo transfer. On the basis of their ability to differentiate into several lineages, proliferate from single cells, induce calcium deposits, and secrete collagen in vivo after transfer on hydroxyapatite carriers, we suggest that this population represents gingival multipotent progenitor cells. The discovery of progenitor cells in gingival connective tissue may help improve our understanding of how the wounded gum is capable of almost perfect healing and opens the prospect of cellular therapy for wound healing using readily available cells at limited risk to the patient.

Rationale: Cerebrovascular function is critical for brain health, and endogenous vascular-protective pathways may provide therapeutic targets for neurological disorders. Sphingosine 1-phosphate (S1P) signaling coordinates vascular functions in other organs, and S1P receptor-1 (S1P 1 ) modulators including fingolimod show promise for the treatment of ischemic and hemorrhagic stroke. However, S1P 1 also coordinates lymphocyte trafficking, and lymphocytes are currently viewed as the principal therapeutic target for S1P 1 modulation in stroke. Objective: To address roles and mechanisms of engagement of endothelial cell (EC) S1P 1 in the naïve and ischemic brain and its potential as a target for cerebrovascular therapy. Methods and Results: Using spatial modulation of S1P provision and signaling, we demonstrate a critical vascular protective role for endothelial S1P 1 in the mouse brain. With an S1P 1 signaling reporter, we reveal that abluminal polarization shields S1P 1 from circulating endogenous and synthetic ligands after maturation of the blood-neural barrier, restricting homeostatic signaling to a subset of arteriolar ECs. S1P 1 signaling sustains hallmark endothelial functions in the naïve brain, and expands during ischemia by engagement of cell-autonomous S1P provision. Disrupting this pathway by EC-selective deficiency in S1P production, export, or the S1P 1 receptor substantially exacerbates brain injury in permanent and transient models of ischemic stroke. By contrast, profound lymphopenia induced by loss of lymphocyte S1P 1 provides modest protection only in the context of reperfusion. In the ischemic brain, EC S1P 1 supports blood-brain barrier (BBB) function, microvascular patency, and the rerouting of blood to hypo-perfused brain tissue through collateral anastomoses. Selective S1P 1 agonism counteracts cortical infarct expansion after middle cerebral artery occlusion by engaging the endothelial receptor pool after BBB penetration. Conclusions: This study provides genetic evidence to support a pivotal role for the endothelium in maintaining perfusion and microvascular patency in the ischemic penumbra that is coordinated by S1P signaling and can be harnessed for neuroprotection with BBB-penetrating S1P 1 agonists.