CD47 inhibiting antibody alleviates brain injury after intraventricular hemorrhage in aged rats.

INTRODUCTION

Intraventricular hemorrhage (IVH) is a major contributor to acute brain injury and post-hemorrhagic hydrocephalus, especially in older adults. CD47 on erythrocytes delivers a "don't-eat-me" signal that inhibits macrophage/microglia (M/MΦ) mediated phagocytosis, slowing hematoma resolution. While CD47 blockade enhances hematoma clearance after IVH in young animals and in intracerebral hemorrhage models, its therapeutic potential in aged IVH has not been examined.

METHODS

Eighteen-month-old male Fischer 344 rats received intraventricular injections of autologous arterial blood mixed with either anti-CD47 antibody or isotype IgG. Saline-injected rats served as additional controls. MRI was performed post-IVH at 4 h, days 1 and 3 to quantify ventricular volume, T2* intraventricular hematoma volume, and T2* non-hypointense lesion volume (early hemolysis). Histological analyses assessed M/MΦ activation, choroid plexus and periventricular immune cell accumulation, ventricular wall injury, and hippocampal neuronal survival.

RESULTS

CD47-blocking antibody markedly alleviated hemorrhage-induced hydrocephalus in aged rats by day 3 after IVH. Treatment with CD47 inhibition significantly reduced intraventricular T2* hematoma volume on both days 1 and 3, and decreased T2* non-hypointense lesion size (an indicator of early hematoma lysis) at both time points. On post-hemorrhage day 3, CD47 blockade robustly increased hematomal Iba1+, CD68+, and HO-1+ M/MΦ infiltration. Enhanced Iba1+ cell accumulation was also observed in the choroid plexus, white matter, and hippocampus, alongside increased CD68+ cells in white matter. CD47 inhibition further attenuated ventricular wall damage on day 3 and reduced neuronal loss in the hippocampal CA1 region.

CONCLUSION

Blocking erythrocyte CD47 facilitates hematoma resolution, reduces hemolysis and hydrocephalus, enhances M/MΦ recruitment across multiple anatomical routes, and mitigates ependymal damage and neuronal injury after IVH in aged rats. These findings support CD47 as a promising therapeutic target for IVH, particularly in the aging population.