Transplantation of in vitro cultured endothelial progenitor cells repairs the blood-brain barrier and improves cognitive function of APP/PS1 transgenic AD mice

To date, the pathogenesis of Alzheimer's disease (AD) remains unclear. It is well-known that excessive deposition of A beta in the brain is a crucial part of the pathogenesis of AD. In recent years, the AD neurovascular unit hypothesis has attracted much attention. Impairment of the blood-brain barrier (BBB) leads to abnormal amyloid-beta (A beta) transport, and chronic cerebral hypoperfusion causes AO deposition throughout the onset and progression of AD. Endothelial progenitor cells (EPCs) are the universal cells for repairing blood vessels. Our previous studies have shown that a reduced number of EPCs in the peripheral blood results in cerebral vascular repair disorder, cerebral hypoperfusion and neurodegeneration, which might be related to the cognitive dysfunction of AD patients. This study was designed to confirm whether EPCs transplantation could repair the blood-brain barrier, stimulate angiogenesis and reduce A beta deposition in AD. The expression of ZO-1, Occludin and Claudin-5 was up regulated in APP/PS1 transgenic mice after hippocampal transplantation of EPCs. Consistent with previous studies, EPC transplants also increased the microvessel density. We observed that A beta senile plaque deposition was decreased and hippocampal cell apoptosis was reduced after EPCs transplantation. The Morris water maze test showed that spatial learning and memory functions were significantly improved in mice transplanted with EPCs. Consequently, EPCs could up-regulate the expression of tight junction proteins, repair BBB tight junction function, stimulate angiogenesis, promote A beta clearance, and decrease neuronal loss, ultimately improve cognitive function. Taken together, these data demonstrate EPCs may play an important role in the therapeutic implications for vascular dysfunction in AD.