MESENCHYMAL STROMAL CELLS PROTECT AGAINST VASCULAR DAMAGE AND DEPRESSION-LIKE BEHAVIOR IN MICE SURVIVING CEREBRAL MALARIA

Introduction Cerebral malaria (CM) is a severe systemic inflammatory disease, that leads to behavioral impairments, such as depression. Currently, there are no therapies to treat the neurological sequelae of CM, and mesenchymal stromal cells (MSC) may be an alternative. Objectives To investigate the effects of MSC therapy on the blood-brain barrier (BBB), leukocyte rolling and adherence in the brain, and depression like-behavior in experimental CM. Methods Male C57BL/6 mice were infected with Plasmodium berghei ANKA (PbA, 1 × 106, intraperitoneally). At day 6, PbA-infected animals received chloroquine (25 mg/kg orally for seven days) and were then randomized to receive MSC (105 cells) or saline intravenously. All animal experiments were approved by the ethics committee of the Oswaldo Cruz Institute (L-012/2015), and had a number of 3 to 12 animals per group. In vitro, endothelial cells were used to evaluate the effects of conditioned media derived from MSC (CMMSC) on cell viability by lactate dehydrogenase (LDH) release. We used a one-way analysis of variance with post-hoc Tukey test to assess the differences between more than two groups and Student‘s t test when data from only two groups were analyzed. Results MSC therapy improved the vascular damage at 7 days after infection (dpi). Evans blue assay and intravital microscopy showed that infected mice, who received only saline, had an increase in BBB permeability (n=7; 0.0084±0.0016) and adherent leukocytes (n=3; 3.76±0.23). PbA+MSC mice had reduced BBB permeability (n=4; 0.0063±0.0012) and leukocyte adhesion in the brain microvasculature (n=4; 2.18±0.37). PbA-infected mice presented reduced levels of BDNF 7 dpi (n=4; 0.025±0.0015), and depression-like behavior 15 dpi evaluated by the tail suspension test (TST, n=5; 44.38±4) and the forced swim test (FST, n=5; 45.5±4.8). MSC therapy restored BDNF levels (n=11; 0.029±0.0008) and mitigated behavioral alterations (n=5; TST:18±2.7; FST:18.2±2.8). CMMSC reduced LDH release in endothelial cells stimulated with heme (group heme: 1,89±0,11; group CMMSC: 0,96±0,06), suggesting a paracrine mechanism of action. Conclusion A single dose of MSC as an adjuvant therapy protected against vascular damage and improved depression-like behavior in mice that survived experimental CM.