Vitamin B12 Attenuates Post-Ischemic Brain Fibrotic Remodeling and Suppresses MAPK1 Signaling in Male Rats

Ischemic stroke (IS) is a major global cause of mortality and disability, with fibrotic scar formation during disease progression markedly restricting neurological recovery. Vitamin B12 (cobalamin) has been shown to improve short-term stroke outcomes; however, its regulatory role in long-term fibrotic remodeling, particularly its capacity to modulate specific molecular pathways, is incompletely understood. The present study integrated network pharmacology with drug-target Mendelian randomization (MR) to identify pivotal vitamin B12-related targets involved in post-ischemic fibrosis, yielding three candidate genes—ALDH2, CD40, and mitogen-activated protein kinase 1 (MAPK1). These targets were subsequently validated through molecular docking, molecular dynamics simulation, nomogram prediction, and in vivo experiments using the middle cerebral artery occlusion/reperfusion (MCAO/R) rat model. The findings suggested that ALDH2 and CD40 act as protective factors, whereas MAPK1 serves as a risk-susceptible driver of post-ischemic fibrotic remodeling. Reverse MR emphasized MAPK1 as the most influential contributor to disease progression among these targets. In subacute MCAO/R male rats, vitamin B12 administration markedly suppressed MAPK1 expression, attenuated the expression of key fibrosis indicators (fibronectin, type I collagen, and alpha-smooth muscle actin), and improved motor recovery. Mechanistic analyses suggest that vitamin B12 may limit fibrotic scar deposition by coordinating a "metabolism–immune–matrix" regulatory network centered on MAPK1. These results provide a robust theoretical foundation for applying vitamin B12-based strategies to counteract post-ischemic fibrosis and establish MAPK1 as a promising therapeutic target for enhancing long-term neurological recovery in ischemic stroke. • Vitamin B12 improves neurological recovery after experimental ischemic stroke in rats. • Vitamin B12 attenuates post-ischemic fibrotic remodeling in brain tissue. • Bioinformatics and Mendelian randomization analyses identify MAPK1 as a potential mediator. • Vitamin B12 treatment suppresses MAPK1 signaling and fibrosis-related markers in vivo. • These findings suggest a potential anti-fibrotic mechanism underlying vitamin B12 neuroprotection.