gms | German Medical Science

Objective: Transplantation of hucb was shown to improve hind limb spasticity in a rat model of neonatal/ infantile hypoxic ischemic brain damage (HI). In this study, we investigated the short- and long-term outcome on gross motor function as well as the influence on the inflammatory reaction of the neuroglial network.

Methods: Seven-day-old Wistar rats underwent a permanent ligation of the left common carotid artery followed by 80 minutes of systemic hypoxia; sham-operated animals served as controls. 24 hours after HI, animals received either a sham injection of saline, intraperitoneal, or intrathecal transplantation of 1x10⁷ hucb. Two and six weeks after HI motor skills were assessed, parameters including forelimb use bias, muscle-strength and distal spasticity (i.e. footprint analysis). Localization and activation of microglia and astrocytes were visualized immunohistochemically in brain sections at the same time points. To quantify changes in astrocytic activation, GFAP and Connexin43 (Cx43) mRNA and protein expression were analyzed on postnatal day (P) 9, 21 and 51.

Results: All behavioral tests showed significant differences between the control group and lesioned animals. Treatment with hucb led to improved motor performance in all tested parameters. Phagocytic-active cells expressing CD68 were found exclusively in the lesioned brain hemispheres. There was significantly less CD68 immunosignal detectable in brains of hucb transplanted versus non-transplanted rats. GFAP immunoreactivity was intense in the penumbral zone. The reactive cortical GFAP expression in hucb positive animals was minor compared to hucb negative rats and astrocytes seemed to display a different phenotype. However, the general level of astrocytic and phagocytic activation appeared reduced in both groups at P51, i.e. during the chronic postischemic phase. Consistently, at all three time points, Western blot analysis and realtime PCR revealed that the GFAP and Cx43 expression increased in lesioned animals as compared to non-lesioned controls and was reduced upon hUCB transplantation.

Conclusions: Transplantation of hucb resulted in an extensive functional improvement of motor abilities up to six weeks after lesion. HI lead to an acute inflammatory reaction with activation of microglia/ phagocytes and astrocytes that ceased during chronification. hUCB transplantation accelerated the regression of inflammatory events in resident neuroglia and invading phagocytes short- and long-term and thus, may result in reduced apoptotic cell death and partial inhibition of glial scar formation.