The Research Of Endothelial Progenitor Cells On Permeability Of Blood Brain Barrier And Angiogenesis After Traumatic Brain Injury

BackgroundTraumatic brain injury (TBI), a form of acquired brain injury, leads to blood-brain barrier (BBB) disruption, neuronal death and neurological dysfunction. Angiogenesis, as a key factor in the reparative process after TBI, provides critical neurovascular substrates for neuronal remodeling and is beneficial of long term functional recovery. Endothelial progenitor cells (EPCs) are lineage-specific stem cells that may be mobilized from the bone marrow (possibly from a number of other organs and tissues) to the peripheral blood in response to traumatic, inflammatory, ischemic injury and homed to the area of injured tissue, then differentiated into endothelial cells and incorporated into growing vessels (angiogenesis) and created new vessels (vasculogenesis). The emergence of EPCs have broken the dogma that revascularization only occurs during embryonic development. Animal models studies indicated that transplantation of EPCs could improve functional recovery of limb ischemia, myocardial ischemia and ischemia stroke. Previous studies in our group have shown a positive correlation between the number of circulating EPCs and clinical outcomes of patients with TBI. Erythropoietin, atorvastatin and progesterone could increase endogenous EPCs and improve outcomes of mice subjected to experimental TBI.ObjectiveThis follow-up study was designed to determine if intracerebroventricular infusion of human umbilical cord blood-derived endothelial colony-forming cells (ECFCs, which were considered to be current putative EPCs), which may reduce systemic impacts of these cells, could repair the BBB, promote angiogenesis and thereby improve functional outcome of mice with TBI.MethodsMononuclear cells isolated from human umbilical cord blood were cultured and expanded to ECFCs. Adult nude mice were exposed to lateral fluid percussion injury and transplanted intracerebroventricularly with ECFCs on day1post TBI, they were divided into ECFCs treated group, saline treated group and sham group. Cellular labeling methods of SP-DiIC18(3) and fluorescence in situ hybridization (FISH) were used to track transplanted ECFCs. BBB permeability and brain water content were measured by the extravasation of Evans blue dye and dry-wet method. The expression of tight junction associated proteins ZO-1and claudin-5and the cytokines angiopoietin (Ang)1and Ang2were assessed by immunoblots and qRT-PCR. The microvascular density (MVD) was quantified by using VWF immunostaining. Modified neurological severity score (mNSS) and Morris water maze were used to evaluate the functional outcome after TBI in mice.ResultsMNCs from umbilical cord blood were cultured for5-8days and formed colonies at approximately14days in culture, they were defined by their ability to take up DiⅠ-acLDL, bind FITC-UEA-1and express the stem cell marker CD34and the endothelial cell markers KDR, VWF and VE-cadherin. These ECFCs were detected at the TBI zone3days after transplantation by SP-DiIC18(3) and FISH. Mice with ECFCs transplant had reduced Evans blue extravasation and brain water content, increased expression of ZO-1, claudin-5and showed a higher expression of Ang1. Mice with ECFCs transplant had also increased MVD. mNSS and Morris water maze test indicated significant improvements in motor ability, spatial acquisition and reference memory in mice receiving ECFCs compared to those receiving saline.ConclusionThese data demonstrate that intracerebroventricular transplanted ECFCs could home to the TBI zone and contribute to the improvement of neurological functions potentially by repairing disrupted BBB and enhancing angiogenesis in the host brain. Our findings suggest that a ECFCs-based cell therapy may improve the recovery of patients with TBI.