Background: Erythrolysis in the clot after intracerebral hemorrhage (ICH) and the release of hemoglobin causes brain injury but it is unclear when such lysis occurs. The present study examined early erythrolysis in rats.
>Methods: Male Sprague-Dawley, spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats had an intracaudate injection of 100μl autologous blood or a needle insertion (sham). All rats had T2 and T2* MRI scanning and brains were used for histology and CD163 (a hemoglobin scavenger receptor) and DARPP-32 (a neuronal marker) immunohistochemistry.
Results: There was marked heterogeneity within the hematoma on T2* MRI, with a hyper- or isointense core and a hypointense periphery at days 1 and 3. Hematoxylin and eosin staining in the same animals showed significant erythrolysis in the core with the formation of erythrocyte ghosts. While the periphery of hematoma had erythrocytes with normal profiles, the border of the periphery and the center displayed distorted erythrocytes and areas with ghost erythrocytes. The degree of erythrolysis was correlated with the severity of neuronal loss (marked by DARPP 32) after ICH (r = 0.791, n = 18, p < 0.01). Perihematomal CD163 was increased by day 1 after ICH and may be involved in clearing hemoglobin caused by early hemolysis (303 ± 128 at day 1 and 453 ± 57 cells/mm2 at day 3, p<0.01). Only a few CD163 positive cells were observed in the ipsilateral basal ganglia of sham controls and in the contralateral basal ganglia of ICH rats. ICH resulted in more severe erythrolysis (e.g. 18.3 ± 4.5 vs. 8.1 ± 5.2 %, p< 0.01 at day 1), neuronal loss (30.0 ± 5.6 vs. 14.1 ± 4.4 %, p<0.05 at day 1), and CD 163 upregulation (p< 0.05) in SHR than in WKY rats.
Conclusion: T2*MRI detectable early erythrolysis occurred in the clot after ICH, and activated CD163. Hypertension is associated with enhanced erythrolysis in the hematoma and more brain injury.