Microinjections of a protease-activated receptor-1 (PAR1) agonist into the intact spinal white matter induces cell proliferation including OPCs within 24 hr. (a) Injection site of PAR agonist (TFLLR-NH2, 60 nmol/1.5 μL, Abgent, San Diego, California) immunolabeled for NG2 (for OPCs; black) and Ki67 (brown) to label dividing cells. Two double-labeled NG2 cells are indicated by arrowheads. Vehicle (phosphate-buffered saline, PBS) injection sites contained no Ki67+ cells. (b) The number of Ki67+ cells expressing NG2 were quantified in the injection site. PAR1 agonist injection significantly increased the number in dividing NG2 cells. (c) The total number of Ki67+ cells was also quantified in the injection sites revealing a significant increase in overall proliferation in PAR agonist-injected tissue compared to PBS control. ***p < .001 t-tailed t test