Human umbilical cord blood cells-secreted exosomal MFG-E8 regulates microglia polarization and ameliorates hypoxic-ischemic brain damage in neonatal rats by SOCS3/STAT3 axis.

Stem cell therapy is expected to become a new treatment for central nervous system damage associated with perinatal hypoxic-ischemic encephalopathy (HIE), but the specific effects are unknown. This study explores the effects of human umbilical cord blood (HUCB) cells-secreted exosomal (HUCB-ex) MFG-E8 in neonatal rats with hypoxic-ischemic brain damage (HIBD), aiming to gain a theoretical foundation for the cure of perinatal HIE. HIBD model was constructed in the Sprague Dawley rats (7-day-old). Rats were then intervened with 1 × 106 HUCB cells, HUCB-ex, or HUCB-exoe-MFG-E8, and HUCB-exsi-MFG-E8. Primary microglia from rats were induced with oxygen-glucose deprivation and re-oxygenation (OGD/R), then co-cultured with either HUCB or primary neuronal cells, and subjected to treatment with HUCB-ex, HUCB-exoe-MFG-E8, HUCB-exsi-MFG-E8, or Stattic. The expression of polarization factors and secreted factors in the microglia was measured using RT-qPCR, immunofluorescence, and Western blot. Neuronal cell damage was assessed using MTT assays and flow cytometry. Behavioral impairments and brain tissue damage in the rats were evaluated using assays including the geotaxis reflex, cliff avoidance response, grip strength test, hematoxylin-eosin staining, TTC staining, and immunofluorescence. Early intervention with HUCB cells in HIBD rats increased test scores, decreased brain tissue weight, infarct area, as well as the IL-6, TNF-α, and IL-1β levels, and increased MFG-E8 levels. HUCB cells also decreased the levels of CD11b/c+CD45hi cells in HIBD rat brain tissue, and increased the levels of CD206+CD11b/c+ cells. In vitro experiments confirmed high expression of MFG-E8 in HUCB-ex. HUCB-exsi-MFG-E8 inhibited M2 polarization and induced neuronal cell injury through the SOCS3/STAT3 pathway. HUCB-ex and HUCB cells have equivalent therapeutic effects in HIBD rats. The treatment effectiveness of HUCB-ex was improved after delivering HUCB-exoe-MFG-E8, while was blocked after delivering HUCB-exsi-MFG-E8. HUCB-exoe-MFG-E8 promoted M2 polarization of microglial and inhibited neuronal cell apoptosis through the SOCS3/STAT3 pathway, to alleviate behavioral disorders and brain tissue damage in HIBD rats.