A pilot study evaluating the safety of chronic retro-orbital administration of human glial progenitor cells in mice

Background Cell therapy is a promising approach for treating neurological disorders, but its safety remains a major concern, including the origin of cells, cultivation methods, and route of administration. Repeated systemic delivery is often required for long-term studies, yet the safety of chronic retro-orbital administration of human glial progenitor cells (GPCs) has not been characterised. This pilot study evaluated the potential risks and pathological processes associated with chronic retro-orbital administration of human iPSC-derived GPCs in mice. Methods GPCs were derived from human induced pluripotent stem cells and injected into the retro-orbital venous sinus of male C57Bl/6 J mice under isoflurane anaesthesia. Two pilot experiments were performed: a high-dose experiment with 500 × 10 3 (n = 9), 150 × 10 3 (n = 5), and 50 × 10 3 (n = 5) cells/mouse administered weekly for two months, and a control group (n = 9) receiving dPBS. Locomotor and exploratory activity were assessed in the open field test. Blood biochemical markers (ALT, AST, AST/ALT ratio, LDH, GGT, and total bilirubin) were measured, and brain sections were analysed by H&E staining and immunohistochemistry for glial fibrillary acidic protein (GFAP). Statistical analysis was performed using ANOVA on ranks with Dunn’s post-hoc test or one-way ANOVA with Holm–Sidak correction. Results Chronic administration of the high dose (500 × 10 3 cells/mouse) for 60 days induced a statistically significant increase in ALT, AST, LDH, and total bilirubin levels, and increased the number of GFAP-positive astrocytes in the cerebral cortex (p = 0.046) compared with the control group. In contrast, lower doses (50 × 10 3 and 150 × 10 3 cells/mouse) did not cause elevated blood markers or astrogliosis. No significant changes in locomotor or exploratory behaviour were observed in the open field test, and no pathomorphological changes were detected in the brain in any group. Conclusions Chronic retro-orbital administration of GPCs at 500 × 10 3 cells/mouse was associated with signs of inflammation and liver damage, whereas doses of 50 × 10 3 and 150 × 10 3 cells/mouse were safe and optimal. These findings provide important pharmacological parameters for designing preclinical studies using long-term GPC administration in mice.