Downregulating ROCK2 by human umbilical cord mesenchymal stem cells promotes pro-resolving microglial polarization and alleviates cerebral injury in germinal matrix hemorrhage.

To address the lack of effective treatments for germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH), a devastating condition in preterm infants with poor prognosis, this study investigated the neuroprotective potential and underlying mechanism of human umbilical cord-derived mesenchymal stem cells (HUCMSCs). Using a collagenase VII-S-induced GMH neonatal rat model and lipopolysaccharide-stimulated BV2 microglial cells, in vivo and in vitro experiments were performed. In vivo results showed that intraventricular HUCMSCs administration alleviated cerebral injury (reduced ventricular enlargement and cortical damage) and improved motor, memory, and cognitive functions in GMH rats. Both HUCMSCs and MSC-conditioned medium (MSC-CM) modulated microglial polarization toward the pro-resolving phenotype, suppressed pro-inflammatory polarization, and decreased TNF-α and IL-6 expression. Mechanistically, MSCs downregulated ROCK2 protein levels; the ROCK agonist PA abrogated MSC-CM's anti-inflammatory effects, while the ROCK inhibitor Y27632 mimicked MSC-CM's pro-M2 polarization. Collectively, this study demonstrates that HUCMSCs exert neuroprotection against GMH by suppressing ROCK2 to regulate microglial polarization, thereby mitigating neuroinflammation and promoting nerve repair, highlighting MSCs as a promising therapeutic strategy for GMH-IVH.